libmicrohttpd

digestauth.c (145350B)

---

 /*
      This file is part of libmicrohttpd
      Copyright (C) 2010, 2011, 2012, 2015, 2018 Daniel Pittman and Christian Grothoff
      Copyright (C) 2014-2024 Evgeny Grin (Karlson2k)
 
      This library is free software; you can redistribute it and/or
      modify it under the terms of the GNU Lesser General Public
      License as published by the Free Software Foundation; either
      version 2.1 of the License, or (at your option) any later version.
 
      This library is distributed in the hope that it will be useful,
      but WITHOUT ANY WARRANTY; without even the implied warranty of
      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      Lesser General Public License for more details.
 
      You should have received a copy of the GNU Lesser General Public
      License along with this library; if not, write to the Free Software
      Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 */
 /**
  * @file digestauth.c
  * @brief Implements HTTP digest authentication
  * @author Amr Ali
  * @author Matthieu Speder
  * @author Christian Grothoff (RFC 7616 support)
  * @author Karlson2k (Evgeny Grin) (fixes, new API, improvements, large rewrite,
  *                                  many RFC 7616 features implementation,
  *                                  old RFC 2069 support)
  */
 #include "digestauth.h"
 #include "gen_auth.h"
 #include "platform.h"
 #include "mhd_limits.h"
 #include "internal.h"
 #include "response.h"
 #ifdef MHD_MD5_SUPPORT
 #  include "mhd_md5_wrap.h"
 #endif /* MHD_MD5_SUPPORT */
 #ifdef MHD_SHA256_SUPPORT
 #  include "mhd_sha256_wrap.h"
 #endif /* MHD_SHA256_SUPPORT */
 #ifdef MHD_SHA512_256_SUPPORT
 #  include "sha512_256.h"
 #endif /* MHD_SHA512_256_SUPPORT */
 #include "mhd_locks.h"
 #include "mhd_mono_clock.h"
 #include "mhd_str.h"
 #include "mhd_compat.h"
 #include "mhd_bithelpers.h"
 #include "mhd_assert.h"
 #include "mhd_check.h"
 
 
 /**
  * Allow re-use of the nonce-nc map array slot after #REUSE_TIMEOUT seconds,
  * if this slot is needed for the new nonce, while the old nonce was not used
  * even one time by the client.
  * Typically clients immediately use generated nonce for new request.
  */
 #define REUSE_TIMEOUT 30
 
 /**
  * The maximum value of artificial timestamp difference to avoid clashes.
  * The value must be suitable for bitwise AND operation.
  */
 #define DAUTH_JUMPBACK_MAX (0x7F)
 
 
 /**
  * 48 bit value in bytes
  */
 #define TIMESTAMP_BIN_SIZE (48 / 8)
 
 
 /**
  * Trim value to the TIMESTAMP_BIN_SIZE size
  */
 #define TRIM_TO_TIMESTAMP(value) \
         ((value) & ((UINT64_C (1) << (TIMESTAMP_BIN_SIZE * 8)) - 1))
 
 
 /**
  * The printed timestamp size in chars
  */
 #define TIMESTAMP_CHARS_LEN (TIMESTAMP_BIN_SIZE * 2)
 
 
 /**
  * Standard server nonce length, not including terminating null,
  *
  * @param digest_size digest size
  */
 #define NONCE_STD_LEN(digest_size) \
         ((digest_size) * 2 + TIMESTAMP_CHARS_LEN)
 
 
 #ifdef MHD_SHA512_256_SUPPORT
 /**
  * Maximum size of any digest hash supported by MHD.
  * (SHA-512/256 > MD5).
  */
 #define MAX_DIGEST SHA512_256_DIGEST_SIZE
 
 /**
  * The common size of SHA-256 digest and SHA-512/256 digest
  */
 #define SHA256_SHA512_256_DIGEST_SIZE SHA512_256_DIGEST_SIZE
 #elif defined(MHD_SHA256_SUPPORT)
 /**
  * Maximum size of any digest hash supported by MHD.
  * (SHA-256 > MD5).
  */
 #define MAX_DIGEST SHA256_DIGEST_SIZE
 
 /**
  * The common size of SHA-256 digest and SHA-512/256 digest
  */
 #define SHA256_SHA512_256_DIGEST_SIZE SHA256_DIGEST_SIZE
 #elif defined(MHD_MD5_SUPPORT)
 /**
  * Maximum size of any digest hash supported by MHD.
  */
 #define MAX_DIGEST MD5_DIGEST_SIZE
 #else  /* ! MHD_MD5_SUPPORT */
 #error At least one hashing algorithm must be enabled
 #endif /* ! MHD_MD5_SUPPORT */
 
 
 /**
  * Macro to avoid using VLAs if the compiler does not support them.
  */
 #ifndef HAVE_C_VARARRAYS
 /**
  * Return #MAX_DIGEST.
  *
  * @param n length of the digest to be used for a VLA
  */
 #define VLA_ARRAY_LEN_DIGEST(n) (MAX_DIGEST)
 
 #else
 /**
  * Return @a n.
  *
  * @param n length of the digest to be used for a VLA
  */
 #define VLA_ARRAY_LEN_DIGEST(n) (n)
 #endif
 
 /**
  * Check that @a n is below #MAX_DIGEST
  */
 #define VLA_CHECK_LEN_DIGEST(n) \
         do { if ((n) > MAX_DIGEST) MHD_PANIC (_ ("VLA too big.\n")); } while (0)
 
 /**
  * Maximum length of a username for digest authentication.
  */
 #define MAX_USERNAME_LENGTH 128
 
 /**
  * Maximum length of a realm for digest authentication.
  */
 #define MAX_REALM_LENGTH 256
 
 /**
  * Maximum length of the response in digest authentication.
  */
 #define MAX_AUTH_RESPONSE_LENGTH (MAX_DIGEST * 2)
 
 /**
  * The required prefix of parameter with the extended notation
  */
 #define MHD_DAUTH_EXT_PARAM_PREFIX "UTF-8'"
 
 /**
  * The minimal size of the prefix for parameter with the extended notation
  */
 #define MHD_DAUTH_EXT_PARAM_MIN_LEN \
         MHD_STATICSTR_LEN_ (MHD_DAUTH_EXT_PARAM_PREFIX "'")
 
 /**
  * The result of nonce-nc map array check.
  */
 enum MHD_CheckNonceNC_
 {
   /**
    * The nonce and NC are OK (valid and NC was not used before).
    */
   MHD_CHECK_NONCENC_OK = MHD_DAUTH_OK,
 
   /**
    * The 'nonce' was overwritten with newer 'nonce' in the same slot or
    * NC was already used.
    * The validity of the 'nonce' was not be checked.
    */
   MHD_CHECK_NONCENC_STALE = MHD_DAUTH_NONCE_STALE,
 
   /**
    * The 'nonce' is wrong, it was not generated before.
    */
   MHD_CHECK_NONCENC_WRONG = MHD_DAUTH_NONCE_WRONG
 };
 
 
 /**
  * Get base hash calculation algorithm from #MHD_DigestAuthAlgo3 value.
  * @param algo3 the MHD_DigestAuthAlgo3 value
  * @return the base hash calculation algorithm
  */
 _MHD_static_inline enum MHD_DigestBaseAlgo
 get_base_digest_algo (enum MHD_DigestAuthAlgo3 algo3)
 {
   unsigned int base_algo;
 
   base_algo =
     ((unsigned int) algo3)
     & ~((unsigned int)
         (MHD_DIGEST_AUTH_ALGO3_NON_SESSION
          | MHD_DIGEST_AUTH_ALGO3_SESSION));
   return (enum MHD_DigestBaseAlgo) base_algo;
 }
 
 
 /**
  * Get digest size for specified algorithm.
  *
  * Internal inline version.
  * @param algo3 the algorithm to check
  * @return the size of the digest or zero if the input value is not
  *         supported/valid
  */
 _MHD_static_inline size_t
 digest_get_hash_size (enum MHD_DigestAuthAlgo3 algo3)
 {
 #ifdef MHD_MD5_SUPPORT
   mhd_assert (MHD_MD5_DIGEST_SIZE == MD5_DIGEST_SIZE);
 #endif /* MHD_MD5_SUPPORT */
 #ifdef MHD_SHA256_SUPPORT
   mhd_assert (MHD_SHA256_DIGEST_SIZE == SHA256_DIGEST_SIZE);
 #endif /* MHD_SHA256_SUPPORT */
 #ifdef MHD_SHA512_256_SUPPORT
   mhd_assert (MHD_SHA512_256_DIGEST_SIZE == SHA512_256_DIGEST_SIZE);
 #ifdef MHD_SHA256_SUPPORT
   mhd_assert (SHA256_DIGEST_SIZE == SHA512_256_DIGEST_SIZE);
 #endif /* MHD_SHA256_SUPPORT */
 #endif /* MHD_SHA512_256_SUPPORT */
   /* Only one algorithm must be specified */
   mhd_assert (1 == \
               (((0 != (algo3 & MHD_DIGEST_BASE_ALGO_MD5)) ? 1 : 0)   \
                + ((0 != (algo3 & MHD_DIGEST_BASE_ALGO_SHA256)) ? 1 : 0)   \
                + ((0 != (algo3 & MHD_DIGEST_BASE_ALGO_SHA512_256)) ? 1 : 0)));
 #ifdef MHD_MD5_SUPPORT
   if (0 != (((unsigned int) algo3)
             & ((unsigned int) MHD_DIGEST_BASE_ALGO_MD5)))
     return MHD_MD5_DIGEST_SIZE;
   else
 #endif /* MHD_MD5_SUPPORT */
 #if defined(MHD_SHA256_SUPPORT) && defined(MHD_SHA512_256_SUPPORT)
   if (0 != (((unsigned int) algo3)
             & ( ((unsigned int) MHD_DIGEST_BASE_ALGO_SHA256)
                 | ((unsigned int) MHD_DIGEST_BASE_ALGO_SHA512_256))))
     return MHD_SHA256_DIGEST_SIZE; /* The same as SHA512_256_DIGEST_SIZE */
   else
 #elif defined(MHD_SHA256_SUPPORT)
   if (0 != (((unsigned int) algo3)
             & ((unsigned int) MHD_DIGEST_BASE_ALGO_SHA256)))
     return MHD_SHA256_DIGEST_SIZE;
   else
 #elif defined(MHD_SHA512_256_SUPPORT)
   if (0 != (((unsigned int) algo3)
             & ((unsigned int) MHD_DIGEST_BASE_ALGO_SHA512_256)))
     return MHD_SHA512_256_DIGEST_SIZE;
   else
 #endif /* MHD_SHA512_256_SUPPORT */
     (void) 0; /* Unsupported algorithm */
 
   return 0; /* Wrong input or unsupported algorithm */
 }
 
 
 /**
  * Get digest size for specified algorithm.
  *
  * The size of the digest specifies the size of the userhash, userdigest
  * and other parameters which size depends on used hash algorithm.
  * @param algo3 the algorithm to check
  * @return the size of the digest (either #MHD_MD5_DIGEST_SIZE or
  *         #MHD_SHA256_DIGEST_SIZE/MHD_SHA512_256_DIGEST_SIZE)
  *         or zero if the input value is not supported or not valid
  * @sa #MHD_digest_auth_calc_userdigest()
  * @sa #MHD_digest_auth_calc_userhash(), #MHD_digest_auth_calc_userhash_hex()
  * @note Available since #MHD_VERSION 0x00097701
  * @ingroup authentication
  */
 _MHD_EXTERN size_t
 MHD_digest_get_hash_size (enum MHD_DigestAuthAlgo3 algo3)
 {
   return digest_get_hash_size (algo3);
 }
 
 
 /**
  * Digest context data
  */
 union DigestCtx
 {
 #ifdef MHD_MD5_SUPPORT
   struct Md5CtxWr md5_ctx;
 #endif /* MHD_MD5_SUPPORT */
 #ifdef MHD_SHA256_SUPPORT
   struct Sha256CtxWr sha256_ctx;
 #endif /* MHD_SHA256_SUPPORT */
 #ifdef MHD_SHA512_256_SUPPORT
   struct Sha512_256Ctx sha512_256_ctx;
 #endif /* MHD_SHA512_256_SUPPORT */
 };
 
 /**
  * The digest calculation structure.
  */
 struct DigestAlgorithm
 {
   /**
    * A context for the digest algorithm, already initialized to be
    * useful for @e init, @e update and @e digest.
    */
   union DigestCtx ctx;
 
   /**
    * The hash calculation algorithm.
    */
   enum MHD_DigestBaseAlgo algo;
 
   /**
    * Buffer for hex-print of the final digest.
    */
 #ifdef _DEBUG
   bool uninitialised; /**< The structure has been not set-up */
   bool algo_selected; /**< The algorithm has been selected */
   bool ready_for_hashing; /**< The structure is ready to hash data */
   bool hashing; /**< Some data has been hashed, but the digest has not finalised yet */
 #endif /* _DEBUG */
 };
 
 
 /**
  * Return the size of the digest.
  * @param da the digest calculation structure to identify
  * @return the size of the digest.
  */
 _MHD_static_inline unsigned int
 digest_get_size (struct DigestAlgorithm *da)
 {
   mhd_assert (! da->uninitialised);
   mhd_assert (da->algo_selected);
 #ifdef MHD_MD5_SUPPORT
   if (MHD_DIGEST_BASE_ALGO_MD5 == da->algo)
     return MD5_DIGEST_SIZE;
 #endif /* MHD_MD5_SUPPORT */
 #ifdef MHD_SHA256_SUPPORT
   if (MHD_DIGEST_BASE_ALGO_SHA256 == da->algo)
     return SHA256_DIGEST_SIZE;
 #endif /* MHD_SHA256_SUPPORT */
 #ifdef MHD_SHA512_256_SUPPORT
   if (MHD_DIGEST_BASE_ALGO_SHA512_256 == da->algo)
     return SHA512_256_DIGEST_SIZE;
 #endif /* MHD_SHA512_256_SUPPORT */
   mhd_assert (0); /* May not happen */
   return 0;
 }
 
 
 #if defined(MHD_MD5_HAS_DEINIT) || defined(MHD_SHA256_HAS_DEINIT)
 /**
  * Indicates presence of digest_deinit() function
  */
 #define MHD_DIGEST_HAS_DEINIT 1
 #endif /* MHD_MD5_HAS_DEINIT || MHD_SHA256_HAS_DEINIT */
 
 #ifdef MHD_DIGEST_HAS_DEINIT
 /**
  * Zero-initialise digest calculation structure.
  *
  * This initialisation is enough to safely call #digest_deinit() only.
  * To make any real digest calculation, #digest_setup_and_init() must be called.
  * @param da the digest calculation
  */
 _MHD_static_inline void
 digest_setup_zero (struct DigestAlgorithm *da)
 {
 #ifdef _DEBUG
   da->uninitialised = false;
   da->algo_selected = false;
   da->ready_for_hashing = false;
   da->hashing = false;
 #endif /* _DEBUG */
   da->algo = MHD_DIGEST_BASE_ALGO_INVALID;
 }
 
 
 /**
  * De-initialise digest calculation structure.
  *
  * This function must be called if #digest_setup_and_init() was called for
  * @a da.
  * This function must not be called if @a da was not initialised by
  * #digest_setup_and_init() or by #digest_setup_zero().
  * @param da the digest calculation
  */
 _MHD_static_inline void
 digest_deinit (struct DigestAlgorithm *da)
 {
   mhd_assert (! da->uninitialised);
 #ifdef MHD_MD5_HAS_DEINIT
   if (MHD_DIGEST_BASE_ALGO_MD5 == da->algo)
     MHD_MD5_deinit (&da->ctx.md5_ctx);
   else
 #endif /* MHD_MD5_HAS_DEINIT */
 #ifdef MHD_SHA256_HAS_DEINIT
   if (MHD_DIGEST_BASE_ALGO_SHA256 == da->algo)
     MHD_SHA256_deinit (&da->ctx.sha256_ctx);
   else
 #endif /* MHD_SHA256_HAS_DEINIT */
   (void) 0;
   digest_setup_zero (da);
 }
 
 
 #else  /* ! MHD_DIGEST_HAS_DEINIT */
 #define digest_setup_zero(da) (void) 0
 #define digest_deinit(da) (void) 0
 #endif /* ! MHD_DIGEST_HAS_DEINIT */
 
 
 /**
  * Set-up the digest calculation structure and initialise with initial values.
  *
  * If @a da was successfully initialised, #digest_deinit() must be called
  * after finishing using of the @a da.
  *
  * This function must not be called more than once for any @a da.
  *
  * @param da the structure to set-up
  * @param algo the algorithm to use for digest calculation
  * @return boolean 'true' if successfully set-up,
  *         false otherwise.
  */
 _MHD_static_inline bool
 digest_init_one_time (struct DigestAlgorithm *da,
                       enum MHD_DigestBaseAlgo algo)
 {
 #ifdef _DEBUG
   da->uninitialised = false;
   da->algo_selected = false;
   da->ready_for_hashing = false;
   da->hashing = false;
 #endif /* _DEBUG */
 #ifdef MHD_MD5_SUPPORT
   if (MHD_DIGEST_BASE_ALGO_MD5 == algo)
   {
     da->algo = MHD_DIGEST_BASE_ALGO_MD5;
 #ifdef _DEBUG
     da->algo_selected = true;
 #endif
     MHD_MD5_init_one_time (&da->ctx.md5_ctx);
 #ifdef _DEBUG
     da->ready_for_hashing = true;
 #endif
     return true;
   }
 #endif /* MHD_MD5_SUPPORT */
 #ifdef MHD_SHA256_SUPPORT
   if (MHD_DIGEST_BASE_ALGO_SHA256 == algo)
   {
     da->algo = MHD_DIGEST_BASE_ALGO_SHA256;
 #ifdef _DEBUG
     da->algo_selected = true;
 #endif
     MHD_SHA256_init_one_time (&da->ctx.sha256_ctx);
 #ifdef _DEBUG
     da->ready_for_hashing = true;
 #endif
     return true;
   }
 #endif /* MHD_SHA256_SUPPORT */
 #ifdef MHD_SHA512_256_SUPPORT
   if (MHD_DIGEST_BASE_ALGO_SHA512_256 == algo)
   {
     da->algo = MHD_DIGEST_BASE_ALGO_SHA512_256;
 #ifdef _DEBUG
     da->algo_selected = true;
 #endif
     MHD_SHA512_256_init (&da->ctx.sha512_256_ctx);
 #ifdef _DEBUG
     da->ready_for_hashing = true;
 #endif
     return true;
   }
 #endif /* MHD_SHA512_256_SUPPORT */
 
   da->algo = MHD_DIGEST_BASE_ALGO_INVALID;
   return false; /* Unsupported or bad algorithm */
 }
 
 
 /**
  * Feed digest calculation with more data.
  * @param da the digest calculation
  * @param data the data to process
  * @param length the size of the @a data in bytes
  */
 _MHD_static_inline void
 digest_update (struct DigestAlgorithm *da,
                const void *data,
                size_t length)
 {
   mhd_assert (! da->uninitialised);
   mhd_assert (da->algo_selected);
   mhd_assert (da->ready_for_hashing);
 #ifdef MHD_MD5_SUPPORT
   if (MHD_DIGEST_BASE_ALGO_MD5 == da->algo)
     MHD_MD5_update (&da->ctx.md5_ctx, (const uint8_t *) data, length);
   else
 #endif /* MHD_MD5_SUPPORT */
 #ifdef MHD_SHA256_SUPPORT
   if (MHD_DIGEST_BASE_ALGO_SHA256 == da->algo)
     MHD_SHA256_update (&da->ctx.sha256_ctx, (const uint8_t *) data, length);
   else
 #endif /* MHD_SHA256_SUPPORT */
 #ifdef MHD_SHA512_256_SUPPORT
   if (MHD_DIGEST_BASE_ALGO_SHA512_256 == da->algo)
     MHD_SHA512_256_update (&da->ctx.sha512_256_ctx,
                            (const uint8_t *) data, length);
   else
 #endif /* MHD_SHA512_256_SUPPORT */
   mhd_assert (0);   /* May not happen */
 #ifdef _DEBUG
   da->hashing = true;
 #endif
 }
 
 
 /**
  * Feed digest calculation with more data from string.
  * @param da the digest calculation
  * @param str the zero-terminated string to process
  */
 _MHD_static_inline void
 digest_update_str (struct DigestAlgorithm *da,
                    const char *str)
 {
   const size_t str_len = strlen (str);
   digest_update (da, (const uint8_t *) str, str_len);
 }
 
 
 /**
  * Feed digest calculation with single colon ':' character.
  * @param da the digest calculation
  * @param str the zero-terminated string to process
  */
 _MHD_static_inline void
 digest_update_with_colon (struct DigestAlgorithm *da)
 {
   static const uint8_t colon = (uint8_t) ':';
   digest_update (da, &colon, 1);
 }
 
 
 /**
  * Finally calculate hash (the digest).
  * @param da the digest calculation
  * @param[out] digest the pointer to the buffer to put calculated digest,
  *                    must be at least digest_get_size(da) bytes large
  */
 _MHD_static_inline void
 digest_calc_hash (struct DigestAlgorithm *da, uint8_t *digest)
 {
   mhd_assert (! da->uninitialised);
   mhd_assert (da->algo_selected);
   mhd_assert (da->ready_for_hashing);
 #ifdef MHD_MD5_SUPPORT
   if (MHD_DIGEST_BASE_ALGO_MD5 == da->algo)
   {
 #ifdef MHD_MD5_HAS_FINISH
     MHD_MD5_finish (&da->ctx.md5_ctx, digest);
 #ifdef _DEBUG
     da->ready_for_hashing = false;
 #endif /* _DEBUG */
 #else  /* ! MHD_MD5_HAS_FINISH */
     MHD_MD5_finish_reset (&da->ctx.md5_ctx, digest);
 #ifdef _DEBUG
     da->ready_for_hashing = true;
 #endif /* _DEBUG */
 #endif /* ! MHD_MD5_HAS_FINISH */
   }
   else
 #endif /* MHD_MD5_SUPPORT */
 #ifdef MHD_SHA256_SUPPORT
   if (MHD_DIGEST_BASE_ALGO_SHA256 == da->algo)
   {
 #ifdef MHD_SHA256_HAS_FINISH
     MHD_SHA256_finish (&da->ctx.sha256_ctx, digest);
 #ifdef _DEBUG
     da->ready_for_hashing = false;
 #endif /* _DEBUG */
 #else  /* ! MHD_SHA256_HAS_FINISH */
     MHD_SHA256_finish_reset (&da->ctx.sha256_ctx, digest);
 #ifdef _DEBUG
     da->ready_for_hashing = true;
 #endif /* _DEBUG */
 #endif /* ! MHD_SHA256_HAS_FINISH */
   }
   else
 #endif /* MHD_SHA256_SUPPORT */
 #ifdef MHD_SHA512_256_SUPPORT
   if (MHD_DIGEST_BASE_ALGO_SHA512_256 == da->algo)
   {
     MHD_SHA512_256_finish (&da->ctx.sha512_256_ctx, digest);
 #ifdef _DEBUG
     da->ready_for_hashing = false;
 #endif /* _DEBUG */
   }
   else
 #endif /* MHD_SHA512_256_SUPPORT */
   mhd_assert (0);   /* Should not happen */
 #ifdef _DEBUG
   da->hashing = false;
 #endif /* _DEBUG */
 }
 
 
 /**
  * Reset the digest calculation structure.
  *
  * @param da the structure to reset
  */
 _MHD_static_inline void
 digest_reset (struct DigestAlgorithm *da)
 {
   mhd_assert (! da->uninitialised);
   mhd_assert (da->algo_selected);
   mhd_assert (! da->hashing);
 #ifdef MHD_MD5_SUPPORT
   if (MHD_DIGEST_BASE_ALGO_MD5 == da->algo)
   {
 #ifdef MHD_MD5_HAS_FINISH
     mhd_assert (! da->ready_for_hashing);
 #else  /* ! MHD_MD5_HAS_FINISH */
     mhd_assert (da->ready_for_hashing);
 #endif /* ! MHD_MD5_HAS_FINISH */
     MHD_MD5_reset (&da->ctx.md5_ctx);
 #ifdef _DEBUG
     da->ready_for_hashing = true;
 #endif /* _DEBUG */
   }
   else
 #endif /* MHD_MD5_SUPPORT */
 #ifdef MHD_SHA256_SUPPORT
   if (MHD_DIGEST_BASE_ALGO_SHA256 == da->algo)
   {
 #ifdef MHD_SHA256_HAS_FINISH
     mhd_assert (! da->ready_for_hashing);
 #else  /* ! MHD_SHA256_HAS_FINISH */
     mhd_assert (da->ready_for_hashing);
 #endif /* ! MHD_SHA256_HAS_FINISH */
     MHD_SHA256_reset (&da->ctx.sha256_ctx);
 #ifdef _DEBUG
     da->ready_for_hashing = true;
 #endif /* _DEBUG */
   }
   else
 #endif /* MHD_SHA256_SUPPORT */
 #ifdef MHD_SHA512_256_SUPPORT
   if (MHD_DIGEST_BASE_ALGO_SHA512_256 == da->algo)
   {
     mhd_assert (! da->ready_for_hashing);
     MHD_SHA512_256_init (&da->ctx.sha512_256_ctx);
 #ifdef _DEBUG
     da->ready_for_hashing = true;
 #endif
   }
   else
 #endif /* MHD_SHA512_256_SUPPORT */
   {
 #ifdef _DEBUG
     da->ready_for_hashing = false;
 #endif
     mhd_assert (0); /* May not happen, bad algorithm */
   }
 }
 
 
 #if defined(MHD_MD5_HAS_EXT_ERROR) || defined(MHD_SHA256_HAS_EXT_ERROR)
 /**
  * Indicates that digest algorithm has external error status
  */
 #define MHD_DIGEST_HAS_EXT_ERROR 1
 #endif /* MHD_MD5_HAS_EXT_ERROR || MHD_SHA256_HAS_EXT_ERROR */
 
 #ifdef MHD_DIGEST_HAS_EXT_ERROR
 /**
  * Get external error code.
  *
  * When external digest calculation used, an error may occur during
  * initialisation or hashing data. This function checks whether external
  * error has been reported for digest calculation.
  * @param da the digest calculation
  * @return true if external error occurs
  */
 _MHD_static_inline bool
 digest_ext_error (struct DigestAlgorithm *da)
 {
   mhd_assert (! da->uninitialised);
   mhd_assert (da->algo_selected);
 #ifdef MHD_MD5_HAS_EXT_ERROR
   if (MHD_DIGEST_BASE_ALGO_MD5 == da->algo)
     return 0 != da->ctx.md5_ctx.ext_error;
 #endif /* MHD_MD5_HAS_EXT_ERROR */
 #ifdef MHD_SHA256_HAS_EXT_ERROR
   if (MHD_DIGEST_BASE_ALGO_SHA256 == da->algo)
     return 0 != da->ctx.sha256_ctx.ext_error;
 #endif /* MHD_MD5_HAS_EXT_ERROR */
   return false;
 }
 
 
 #else  /* ! MHD_DIGEST_HAS_EXT_ERROR */
 #define digest_ext_error(da) (false)
 #endif /* ! MHD_DIGEST_HAS_EXT_ERROR */
 
 
 /**
  * Extract timestamp from the given nonce.
  * @param nonce the nonce to check
  * @param noncelen the length of the nonce, zero for autodetect
  * @param[out] ptimestamp the pointer to store extracted timestamp
  * @return true if timestamp was extracted,
  *         false if nonce does not have valid timestamp.
  */
 static bool
 get_nonce_timestamp (const char *const nonce,
                      size_t noncelen,
                      uint64_t *const ptimestamp)
 {
   if (0 == noncelen)
     noncelen = strlen (nonce);
 
   if (true
 #ifdef MHD_MD5_SUPPORT
       && (NONCE_STD_LEN (MD5_DIGEST_SIZE) != noncelen)
 #endif /* MHD_MD5_SUPPORT */
 #if defined(MHD_SHA256_SUPPORT) || defined(MHD_SHA512_256_SUPPORT)
       && (NONCE_STD_LEN (SHA256_SHA512_256_DIGEST_SIZE) != noncelen)
 #endif /* MHD_SHA256_SUPPORT */
       )
     return false;
 
   if (TIMESTAMP_CHARS_LEN !=
       MHD_strx_to_uint64_n_ (nonce + noncelen - TIMESTAMP_CHARS_LEN,
                              TIMESTAMP_CHARS_LEN,
                              ptimestamp))
     return false;
   return true;
 }
 
 
 MHD_DATA_TRUNCATION_RUNTIME_CHECK_DISABLE_
 
 /**
  * Super-fast xor-based "hash" function
  *
  * @param data the data to calculate hash for
  * @param data_size the size of the data in bytes
  * @return the "hash"
  */
 static uint32_t
 fast_simple_hash (const uint8_t *data,
                   size_t data_size)
 {
   uint32_t hash;
 
   if (0 != data_size)
   {
     size_t i;
     hash = data[0];
     for (i = 1; i < data_size; i++)
       hash = _MHD_ROTL32 (hash, 7) ^ data[i];
   }
   else
     hash = 0;
 
   return hash;
 }
 
 
 MHD_DATA_TRUNCATION_RUNTIME_CHECK_RESTORE_
 
 /**
  * Get index of the nonce in the nonce-nc map array.
  *
  * @param arr_size the size of nonce_nc array
  * @param nonce the pointer that referenced a zero-terminated array of nonce
  * @param noncelen the length of @a nonce, in characters
  * @return #MHD_YES if successful, #MHD_NO if invalid (or we have no NC array)
  */
 static size_t
 get_nonce_nc_idx (size_t arr_size,
                   const char *nonce,
                   size_t noncelen)
 {
   mhd_assert (0 != arr_size);
   mhd_assert (0 != noncelen);
   return fast_simple_hash ((const uint8_t *) nonce, noncelen) % arr_size;
 }
 
 
 /**
  * Check nonce-nc map array with the new nonce counter.
  *
  * @param connection The MHD connection structure
  * @param nonce the pointer that referenced hex nonce, does not need to be
  *              zero-terminated
  * @param noncelen the length of @a nonce, in characters
  * @param nc The nonce counter
  * @return #MHD_DAUTH_NONCENC_OK if successful,
  *         #MHD_DAUTH_NONCENC_STALE if nonce is stale (or no nonce-nc array
  *         is available),
  *         #MHD_DAUTH_NONCENC_WRONG if nonce was not recodered in nonce-nc map
  *         array, while it should.
  */
 static enum MHD_CheckNonceNC_
 check_nonce_nc (struct MHD_Connection *connection,
                 const char *nonce,
                 size_t noncelen,
                 uint64_t nonce_time,
                 uint64_t nc)
 {
   struct MHD_Daemon *daemon = MHD_get_master (connection->daemon);
   struct MHD_NonceNc *nn;
   uint32_t mod;
   enum MHD_CheckNonceNC_ ret;
 
   mhd_assert (0 != noncelen);
   mhd_assert (0 != nc);
   if (MAX_DIGEST_NONCE_LENGTH < noncelen)
     return MHD_CHECK_NONCENC_WRONG; /* This should be impossible, but static analysis
                       tools have a hard time with it *and* this also
                       protects against unsafe modifications that may
                       happen in the future... */
   mod = daemon->nonce_nc_size;
   if (0 == mod)
     return MHD_CHECK_NONCENC_STALE;  /* no array! */
   if (nc >= UINT32_MAX - 64)
     return MHD_CHECK_NONCENC_STALE;  /* Overflow, unrealistically high value */
 
   nn = &daemon->nnc[get_nonce_nc_idx (mod, nonce, noncelen)];
 
   MHD_mutex_lock_chk_ (&daemon->nnc_lock);
 
   /* The nonces recorded in the array do not all have the same length: the
    * daemon may serve several digest algorithms at the same time and the
    * length of the nonce depends on the size of the digest (44 characters
    * for MD5, 76 for SHA-256 and SHA-512/256).  The slot selected by the
    * hash of the client's nonce may therefore hold a nonce of a completely
    * different length, which must not be inspected with the client's
    * length. */
   if (strlen (nn->nonce) != noncelen)
   {
     if (0 == nn->nonce[0])
     { /* The slot was never used, while the client's nonce value should be
        * recorded when it was generated by MHD */
       ret = MHD_CHECK_NONCENC_WRONG;
     }
     else
     { /* The slot holds a nonce generated for another digest algorithm.
        * The client's nonce is not (or no longer) recorded. */
       ret = MHD_CHECK_NONCENC_STALE;
     }
   }
   else if (0 != memcmp (nn->nonce, nonce, noncelen))
   { /* The nonce in the slot does not match nonce from the client */
     if (0 == nn->nonce[0])
     { /* The slot was never used, while the client's nonce value should be
        * recorded when it was generated by MHD */
       ret = MHD_CHECK_NONCENC_WRONG;
     }
     else
     {
       uint64_t slot_ts; /**< The timestamp in the slot */
       if (! get_nonce_timestamp (nn->nonce, noncelen, &slot_ts))
       {
         mhd_assert (0); /* The value is the slot is wrong */
         ret = MHD_CHECK_NONCENC_STALE;
       }
       else
       {
         /* Unsigned value, will be large if nonce_time is less than slot_ts */
         const uint64_t ts_diff = TRIM_TO_TIMESTAMP (nonce_time - slot_ts);
         if ((REUSE_TIMEOUT * 1000) >= ts_diff)
         {
           /* The nonce from the client may not have been placed in the slot
            * because another nonce in that slot has not yet expired. */
           ret = MHD_CHECK_NONCENC_STALE;
         }
         else if (TRIM_TO_TIMESTAMP (UINT64_MAX) / 2 >= ts_diff)
         {
           /* Too large value means that nonce_time is less than slot_ts.
            * The nonce from the client may have been overwritten by the newer
            * nonce. */
           ret = MHD_CHECK_NONCENC_STALE;
         }
         else
         {
           /* The nonce from the client should be generated after the nonce
            * in the slot has been expired, the nonce must be recorded, but
            * it's not. */
           ret = MHD_CHECK_NONCENC_WRONG;
         }
       }
     }
   }
   else if (nc > nn->nc)
   {
     /* 'nc' is larger, shift bitmask and bump limit */
     const uint32_t jump_size = (uint32_t) nc - nn->nc;
     if (64 > jump_size)
     {
       /* small jump, less than mask width */
       nn->nmask <<= jump_size;
       /* Set bit for the old 'nc' value */
       nn->nmask |= (UINT64_C (1) << (jump_size - 1));
     }
     else if (64 == jump_size)
       nn->nmask = (UINT64_C (1) << 63);
     else
       nn->nmask = 0;                /* big jump, unset all bits in the mask */
     nn->nc = (uint32_t) nc;
     ret = MHD_CHECK_NONCENC_OK;
   }
   else if (nc < nn->nc)
   {
     /* Note that we use 64 here, as we do not store the
        bit for 'nn->nc' itself in 'nn->nmask' */
     if ( (nc + 64 >= nn->nc) &&
          (0 == ((UINT64_C (1) << (nn->nc - nc - 1)) & nn->nmask)) )
     {
       /* Out-of-order nonce, but within 64-bit bitmask, set bit */
       nn->nmask |= (UINT64_C (1) << (nn->nc - nc - 1));
       ret = MHD_CHECK_NONCENC_OK;
     }
     else
       /* 'nc' was already used or too old (more then 64 values ago) */
       ret = MHD_CHECK_NONCENC_STALE;
   }
   else /* if (nc == nn->nc) */
     /* 'nc' was already used */
     ret = MHD_CHECK_NONCENC_STALE;
 
   MHD_mutex_unlock_chk_ (&daemon->nnc_lock);
 
   return ret;
 }
 
 
 /**
  * Get username type used by the client.
  * This function does not check whether userhash can be decoded or
  * extended notation (if used) is valid.
  * @param params the Digest Authorization parameters
  * @return the type of username
  */
 _MHD_static_inline enum MHD_DigestAuthUsernameType
 get_rq_uname_type (const struct MHD_RqDAuth *params)
 {
   if (NULL != params->username.value.str)
   {
     if (NULL == params->username_ext.value.str)
       return params->userhash ?
              MHD_DIGEST_AUTH_UNAME_TYPE_USERHASH :
              MHD_DIGEST_AUTH_UNAME_TYPE_STANDARD;
     else  /* Both 'username' and 'username*' are used */
       return MHD_DIGEST_AUTH_UNAME_TYPE_INVALID;
   }
   else if (NULL != params->username_ext.value.str)
   {
     if (! params->username_ext.quoted && ! params->userhash &&
         (MHD_DAUTH_EXT_PARAM_MIN_LEN <= params->username_ext.value.len) )
       return MHD_DIGEST_AUTH_UNAME_TYPE_EXTENDED;
     else
       return MHD_DIGEST_AUTH_UNAME_TYPE_INVALID;
   }
 
   return MHD_DIGEST_AUTH_UNAME_TYPE_MISSING;
 }
 
 
 /**
  * Get total size required for 'username' and 'userhash_bin'
  * @param params the Digest Authorization parameters
  * @param uname_type the type of username
  * @return the total size required for 'username' and
  *         'userhash_bin' is userhash is used
  */
 _MHD_static_inline size_t
 get_rq_unames_size (const struct MHD_RqDAuth *params,
                     enum MHD_DigestAuthUsernameType uname_type)
 {
   size_t s;
 
   mhd_assert (get_rq_uname_type (params) == uname_type);
   s = 0;
   if ((MHD_DIGEST_AUTH_UNAME_TYPE_STANDARD == uname_type) ||
       (MHD_DIGEST_AUTH_UNAME_TYPE_USERHASH == uname_type) )
   {
     s += params->username.value.len + 1; /* Add one byte for zero-termination */
     if (MHD_DIGEST_AUTH_UNAME_TYPE_USERHASH == uname_type)
       s += (params->username.value.len + 1) / 2;
   }
   else if (MHD_DIGEST_AUTH_UNAME_TYPE_EXTENDED == uname_type)
     s += params->username_ext.value.len
          - MHD_DAUTH_EXT_PARAM_MIN_LEN + 1; /* Add one byte for zero-termination */
   return s;
 }
 
 
 /**
  * Get unquoted version of Digest Authorization parameter.
  * This function automatically zero-teminate the result.
  * @param param the parameter to extract
  * @param[out] buf the output buffer, must be enough size to hold the result,
  *                 the recommended size is 'param->value.len + 1'
  * @return the size of the result, not including the terminating zero
  */
 static size_t
 get_rq_param_unquoted_copy_z (const struct MHD_RqDAuthParam *param, char *buf)
 {
   size_t len;
   mhd_assert (NULL != param->value.str);
   if (! param->quoted)
   {
     memcpy (buf, param->value.str, param->value.len);
     buf [param->value.len] = 0;
     return param->value.len;
   }
 
   len = MHD_str_unquote (param->value.str, param->value.len, buf);
   mhd_assert (0 != len);
   mhd_assert (len < param->value.len);
   buf[len] = 0;
   return len;
 }
 
 
 /**
  * Get decoded version of username from extended notation.
  * This function automatically zero-teminate the result.
  * @param uname_ext the string of client's 'username*' parameter value
  * @param uname_ext_len the length of @a uname_ext in chars
  * @param[out] buf the output buffer to put decoded username value
  * @param buf_size the size of @a buf
  * @return the number of characters copied to the output buffer or
  *         -1 if wrong extended notation is used.
  */
 static ssize_t
 get_rq_extended_uname_copy_z (const char *uname_ext, size_t uname_ext_len,
                               char *buf, size_t buf_size)
 {
   size_t r;
   size_t w;
   if ((size_t) SSIZE_MAX < uname_ext_len)
     return -1; /* Too long input string */
 
   if (MHD_DAUTH_EXT_PARAM_MIN_LEN > uname_ext_len)
     return -1; /* Required prefix is missing */
 
   if (! MHD_str_equal_caseless_bin_n_ (uname_ext, MHD_DAUTH_EXT_PARAM_PREFIX,
                                        MHD_STATICSTR_LEN_ ( \
                                          MHD_DAUTH_EXT_PARAM_PREFIX)))
     return -1; /* Only UTF-8 is supported, as it is implied by RFC 7616 */
 
   r = MHD_STATICSTR_LEN_ (MHD_DAUTH_EXT_PARAM_PREFIX);
   /* Skip language tag */
   while (r < uname_ext_len && '\'' != uname_ext[r])
   {
     const char chr = uname_ext[r];
     if ((' ' == chr) || ('\t' == chr) || ('\"' == chr) || (',' == chr) ||
         (';' == chr) )
       return -1; /* Wrong char in language tag */
     r++;
   }
   if (r >= uname_ext_len)
     return -1; /* The end of the language tag was not found */
   r++; /* Advance to the next char */
 
   w = MHD_str_pct_decode_strict_n_ (uname_ext + r, uname_ext_len - r,
                                     buf, buf_size);
   if ((0 == w) && (0 != uname_ext_len - r))
     return -1; /* Broken percent encoding */
   buf[w] = 0; /* Zero terminate the result */
   mhd_assert (SSIZE_MAX > w);
   return (ssize_t) w;
 }
 
 
 /**
  * Get copy of username used by the client.
  * @param params the Digest Authorization parameters
  * @param uname_type the type of username
  * @param[out] uname_info the pointer to the structure to be filled
  * @param buf the buffer to be used for usernames
  * @param buf_size the size of the @a buf
  * @return the size of the @a buf used by pointers in @a unames structure
  */
 static size_t
 get_rq_uname (const struct MHD_RqDAuth *params,
               enum MHD_DigestAuthUsernameType uname_type,
               struct MHD_DigestAuthUsernameInfo *uname_info,
               uint8_t *buf,
               size_t buf_size)
 {
   size_t buf_used;
 
   buf_used = 0;
   mhd_assert (get_rq_uname_type (params) == uname_type);
   mhd_assert (MHD_DIGEST_AUTH_UNAME_TYPE_INVALID != uname_type);
   mhd_assert (MHD_DIGEST_AUTH_UNAME_TYPE_MISSING != uname_type);
 
   uname_info->username = NULL;
   uname_info->username_len = 0;
   uname_info->userhash_hex = NULL;
   uname_info->userhash_hex_len = 0;
   uname_info->userhash_bin = NULL;
 
   if (MHD_DIGEST_AUTH_UNAME_TYPE_STANDARD == uname_type)
   {
     uname_info->username = (char *) (buf + buf_used);
     uname_info->username_len =
       get_rq_param_unquoted_copy_z (&params->username,
                                     uname_info->username);
     buf_used += uname_info->username_len + 1;
     uname_info->uname_type = MHD_DIGEST_AUTH_UNAME_TYPE_STANDARD;
   }
   else if (MHD_DIGEST_AUTH_UNAME_TYPE_USERHASH == uname_type)
   {
     size_t res;
 
     uname_info->userhash_hex = (char *) (buf + buf_used);
     uname_info->userhash_hex_len =
       get_rq_param_unquoted_copy_z (&params->username,
                                     uname_info->userhash_hex);
     buf_used += uname_info->userhash_hex_len + 1;
     uname_info->userhash_bin = (uint8_t *) (buf + buf_used);
     res = MHD_hex_to_bin (uname_info->userhash_hex,
                           uname_info->userhash_hex_len,
                           uname_info->userhash_bin);
     if (res != uname_info->userhash_hex_len / 2)
     {
       uname_info->userhash_bin = NULL;
       uname_info->uname_type = MHD_DIGEST_AUTH_UNAME_TYPE_INVALID;
     }
     else
     {
       /* Avoid pointers outside allocated region when the size is zero */
       if (0 == res)
         uname_info->userhash_bin = (uint8_t *) uname_info->username;
       uname_info->uname_type = MHD_DIGEST_AUTH_UNAME_TYPE_USERHASH;
       buf_used += res;
     }
   }
   else if (MHD_DIGEST_AUTH_UNAME_TYPE_EXTENDED == uname_type)
   {
     ssize_t res;
     res = get_rq_extended_uname_copy_z (params->username_ext.value.str,
                                         params->username_ext.value.len,
                                         (char *) (buf + buf_used),
                                         buf_size - buf_used);
     if (0 > res)
       uname_info->uname_type = MHD_DIGEST_AUTH_UNAME_TYPE_INVALID;
     else
     {
       uname_info->username = (char *) (buf + buf_used);
       uname_info->username_len = (size_t) res;
       uname_info->uname_type = MHD_DIGEST_AUTH_UNAME_TYPE_EXTENDED;
       buf_used += uname_info->username_len + 1;
     }
   }
   else
   {
     mhd_assert (0);
     uname_info->uname_type = MHD_DIGEST_AUTH_UNAME_TYPE_INVALID;
   }
   mhd_assert (buf_size >= buf_used);
   return buf_used;
 }
 
 
 /**
  * Result of request's Digest Authorization 'nc' value extraction
  */
 enum MHD_GetRqNCResult
 {
   MHD_GET_RQ_NC_NONE = -1,    /**< No 'nc' value */
   MHD_GET_RQ_NC_VALID = 0,    /**< Readable 'nc' value */
   MHD_GET_RQ_NC_TOO_LONG = 1, /**< The 'nc' value is too long */
   MHD_GET_RQ_NC_TOO_LARGE = 2,/**< The 'nc' value is too big to fit uint32_t */
   MHD_GET_RQ_NC_BROKEN = 3    /**< The 'nc' value is not a number */
 };
 
 
 /**
  * Get 'nc' value from request's Authorization header
  * @param params the request digest authentication
  * @param[out] nc the pointer to put nc value to
  * @return enum value indicating the result
  */
 static enum MHD_GetRqNCResult
 get_rq_nc (const struct MHD_RqDAuth *params,
            uint32_t *nc)
 {
   const struct MHD_RqDAuthParam *const nc_param =
     &params->nc;
   char unq[16];
   const char *val;
   size_t val_len;
   size_t res;
   uint64_t nc_val;
 
   if (NULL == nc_param->value.str)
     return MHD_GET_RQ_NC_NONE;
 
   if (0 == nc_param->value.len)
     return MHD_GET_RQ_NC_BROKEN;
 
   if (! nc_param->quoted)
   {
     val = nc_param->value.str;
     val_len = nc_param->value.len;
   }
   else
   {
     /* Actually no backslashes must be used in 'nc' */
     if (sizeof(unq) < params->nc.value.len)
       return MHD_GET_RQ_NC_TOO_LONG;
     val_len = MHD_str_unquote (nc_param->value.str, nc_param->value.len, unq);
     if (0 == val_len)
       return MHD_GET_RQ_NC_BROKEN;
     val = unq;
   }
 
   res = MHD_strx_to_uint64_n_ (val, val_len, &nc_val);
   if (0 == res)
   {
     const char f = val[0];
     if ( (('9' >= f) && ('0' <= f)) ||
          (('F' >= f) && ('A' <= f)) ||
          (('a' <= f) && ('f' >= f)) )
       return MHD_GET_RQ_NC_TOO_LARGE;
     else
       return MHD_GET_RQ_NC_BROKEN;
   }
   if (val_len != res)
     return MHD_GET_RQ_NC_BROKEN;
   if (UINT32_MAX < nc_val)
     return MHD_GET_RQ_NC_TOO_LARGE;
   *nc = (uint32_t) nc_val;
   return MHD_GET_RQ_NC_VALID;
 }
 
 
 /**
  * Get information about Digest Authorization client's header.
  *
  * @param connection The MHD connection structure
  * @return NULL no valid Digest Authorization header is used in the request;
  *         a pointer structure with information if the valid request header
  *         found, free using #MHD_free().
  * @note Available since #MHD_VERSION 0x00097701
  * @ingroup authentication
  */
 _MHD_EXTERN struct MHD_DigestAuthInfo *
 MHD_digest_auth_get_request_info3 (struct MHD_Connection *connection)
 {
   const struct MHD_RqDAuth *params;
   struct MHD_DigestAuthInfo *info;
   enum MHD_DigestAuthUsernameType uname_type;
   size_t unif_buf_size;
   uint8_t *unif_buf_ptr;
   size_t unif_buf_used;
   enum MHD_GetRqNCResult nc_res;
 
   params = MHD_get_rq_dauth_params_ (connection);
   if (NULL == params)
     return NULL;
 
   unif_buf_size = 0;
 
   uname_type = get_rq_uname_type (params);
 
   unif_buf_size += get_rq_unames_size (params, uname_type);
 
   if (NULL != params->opaque.value.str)
     unif_buf_size += params->opaque.value.len + 1;  /* Add one for zero-termination */
   if (NULL != params->realm.value.str)
     unif_buf_size += params->realm.value.len + 1;   /* Add one for zero-termination */
   info = (struct MHD_DigestAuthInfo *)
          MHD_calloc_ (1, (sizeof(struct MHD_DigestAuthInfo)) + unif_buf_size);
   if (NULL == info)
     return NULL;
   unif_buf_ptr = (uint8_t *) (info + 1);
   unif_buf_used = 0;
 
   info->algo3 = params->algo3;
 
   if ( (MHD_DIGEST_AUTH_UNAME_TYPE_MISSING != uname_type) &&
        (MHD_DIGEST_AUTH_UNAME_TYPE_INVALID != uname_type) )
     unif_buf_used +=
       get_rq_uname (params, uname_type,
                     (struct MHD_DigestAuthUsernameInfo *) info,
                     unif_buf_ptr + unif_buf_used,
                     unif_buf_size - unif_buf_used);
   else
     info->uname_type = uname_type;
 
   if (NULL != params->opaque.value.str)
   {
     info->opaque = (char *) (unif_buf_ptr + unif_buf_used);
     info->opaque_len = get_rq_param_unquoted_copy_z (&params->opaque,
                                                      info->opaque);
     unif_buf_used += info->opaque_len + 1;
   }
   if (NULL != params->realm.value.str)
   {
     info->realm = (char *) (unif_buf_ptr + unif_buf_used);
     info->realm_len = get_rq_param_unquoted_copy_z (&params->realm,
                                                     info->realm);
     unif_buf_used += info->realm_len + 1;
   }
 
   mhd_assert (unif_buf_size >= unif_buf_used);
 
   info->qop = params->qop;
 
   if (NULL != params->cnonce.value.str)
     info->cnonce_len = params->cnonce.value.len;
   else
     info->cnonce_len = 0;
 
   nc_res = get_rq_nc (params, &info->nc);
   if (MHD_GET_RQ_NC_VALID != nc_res)
     info->nc = MHD_DIGEST_AUTH_INVALID_NC_VALUE;
 
   return info;
 }
 
 
 /**
  * Get the username from Digest Authorization client's header.
  *
  * @param connection The MHD connection structure
  * @return NULL if no valid Digest Authorization header is used in the request,
  *         or no username parameter is present in the header, or username is
  *         provided incorrectly by client (see description for
  *         #MHD_DIGEST_AUTH_UNAME_TYPE_INVALID);
  *         a pointer structure with information if the valid request header
  *         found, free using #MHD_free().
  * @sa MHD_digest_auth_get_request_info3() provides more complete information
  * @note Available since #MHD_VERSION 0x00097701
  * @ingroup authentication
  */
 _MHD_EXTERN struct MHD_DigestAuthUsernameInfo *
 MHD_digest_auth_get_username3 (struct MHD_Connection *connection)
 {
   const struct MHD_RqDAuth *params;
   struct MHD_DigestAuthUsernameInfo *uname_info;
   enum MHD_DigestAuthUsernameType uname_type;
   size_t unif_buf_size;
   uint8_t *unif_buf_ptr;
   size_t unif_buf_used;
 
   params = MHD_get_rq_dauth_params_ (connection);
   if (NULL == params)
     return NULL;
 
   uname_type = get_rq_uname_type (params);
   if ( (MHD_DIGEST_AUTH_UNAME_TYPE_MISSING == uname_type) ||
        (MHD_DIGEST_AUTH_UNAME_TYPE_INVALID == uname_type) )
     return NULL;
 
   unif_buf_size = get_rq_unames_size (params, uname_type);
 
   uname_info = (struct MHD_DigestAuthUsernameInfo *)
                MHD_calloc_ (1, (sizeof(struct MHD_DigestAuthUsernameInfo))
                             + unif_buf_size);
   if (NULL == uname_info)
     return NULL;
   unif_buf_ptr = (uint8_t *) (uname_info + 1);
   unif_buf_used = get_rq_uname (params, uname_type, uname_info, unif_buf_ptr,
                                 unif_buf_size);
   mhd_assert (unif_buf_size >= unif_buf_used);
   (void) unif_buf_used; /* Mute compiler warning on non-debug builds */
   mhd_assert (MHD_DIGEST_AUTH_UNAME_TYPE_MISSING != uname_info->uname_type);
 
   if (MHD_DIGEST_AUTH_UNAME_TYPE_INVALID == uname_info->uname_type)
   {
     free (uname_info);
     return NULL;
   }
   mhd_assert (uname_type == uname_info->uname_type);
   uname_info->algo3 = params->algo3;
 
   return uname_info;
 }
 
 
 /**
  * Get the username from the authorization header sent by the client
  *
  * This function supports username in standard and extended notations.
  * "userhash" is not supported by this function.
  *
  * @param connection The MHD connection structure
  * @return NULL if no username could be found, username provided as
  *         "userhash", extended notation broken or memory allocation error
  *         occurs;
  *         a pointer to the username if found, free using #MHD_free().
  * @warning Returned value must be freed by #MHD_free().
  * @sa #MHD_digest_auth_get_username3()
  * @ingroup authentication
  */
 _MHD_EXTERN char *
 MHD_digest_auth_get_username (struct MHD_Connection *connection)
 {
   const struct MHD_RqDAuth *params;
   char *username;
   size_t buf_size;
   enum MHD_DigestAuthUsernameType uname_type;
 
   params = MHD_get_rq_dauth_params_ (connection);
   if (NULL == params)
     return NULL;
 
   uname_type = get_rq_uname_type (params);
 
   if ( (MHD_DIGEST_AUTH_UNAME_TYPE_STANDARD != uname_type) &&
        (MHD_DIGEST_AUTH_UNAME_TYPE_EXTENDED != uname_type) )
     return NULL;
 
   buf_size = get_rq_unames_size (params, uname_type);
 
   mhd_assert (0 != buf_size);
 
   username = (char *) MHD_calloc_ (1, buf_size);
   if (NULL == username)
     return NULL;
 
   if (1)
   {
     struct MHD_DigestAuthUsernameInfo uname_strct;
     size_t used;
 
     memset (&uname_strct, 0, sizeof(uname_strct));
 
     used = get_rq_uname (params, uname_type, &uname_strct,
                          (uint8_t *) username, buf_size);
     if (uname_type != uname_strct.uname_type)
     { /* Broken encoding for extended notation */
       free (username);
       return NULL;
     }
     (void) used; /* Mute compiler warning for non-debug builds */
     mhd_assert (buf_size >= used);
   }
 
   return username;
 }
 
 
 /**
  * Calculate the server nonce so that it mitigates replay attacks
  * The current format of the nonce is ...
  * H(timestamp:random data:various parameters) + Hex(timestamp)
  *
  * @param nonce_time The amount of time in seconds for a nonce to be invalid
  * @param mthd_e HTTP method as enum value
  * @param method HTTP method as a string
  * @param rnd the pointer to a character array for the random seed
  * @param rnd_size The size of the random seed array @a rnd
  * @param saddr the pointer to the socket address structure
  * @param saddr_size the size of the socket address structure @a saddr
  * @param uri the HTTP URI (in MHD, without the arguments ("?k=v")
  * @param uri_len the length of the @a uri
  * @param first_header the pointer to the first request's header
  * @param realm A string of characters that describes the realm of auth.
  * @param realm_len the length of the @a realm.
  * @param bind_options the nonce bind options (#MHD_DAuthBindNonce values).
  * @param da digest algorithm to use
  * @param[out] nonce the pointer to a character array for the nonce to put in,
  *                   must provide NONCE_STD_LEN(digest_get_size(da)) bytes,
  *                   result is NOT zero-terminated
  */
 static void
 calculate_nonce (uint64_t nonce_time,
                  enum MHD_HTTP_Method mthd_e,
                  const char *method,
                  const char *rnd,
                  size_t rnd_size,
                  const struct sockaddr_storage *saddr,
                  size_t saddr_size,
                  const char *uri,
                  size_t uri_len,
                  const struct MHD_HTTP_Req_Header *first_header,
                  const char *realm,
                  size_t realm_len,
                  unsigned int bind_options,
                  struct DigestAlgorithm *da,
                  char *nonce)
 {
   mhd_assert (! da->hashing);
   if (1)
   {
     /* Add the timestamp to the hash calculation */
     uint8_t timestamp[TIMESTAMP_BIN_SIZE];
     /* If the nonce_time is milliseconds, then the same 48 bit value will repeat
      * every 8 919 years, which is more than enough to mitigate a replay attack */
 #if TIMESTAMP_BIN_SIZE != 6
 #error The code needs to be updated here
 #endif
     timestamp[0] = (uint8_t) (nonce_time >> (8 * (TIMESTAMP_BIN_SIZE - 1 - 0)));
     timestamp[1] = (uint8_t) (nonce_time >> (8 * (TIMESTAMP_BIN_SIZE - 1 - 1)));
     timestamp[2] = (uint8_t) (nonce_time >> (8 * (TIMESTAMP_BIN_SIZE - 1 - 2)));
     timestamp[3] = (uint8_t) (nonce_time >> (8 * (TIMESTAMP_BIN_SIZE - 1 - 3)));
     timestamp[4] = (uint8_t) (nonce_time >> (8 * (TIMESTAMP_BIN_SIZE - 1 - 4)));
     timestamp[5] = (uint8_t) (nonce_time >> (8 * (TIMESTAMP_BIN_SIZE - 1 - 5)));
     MHD_bin_to_hex (timestamp,
                     sizeof (timestamp),
                     nonce + digest_get_size (da) * 2);
     digest_update (da,
                    timestamp,
                    sizeof (timestamp));
   }
   if (rnd_size > 0)
   {
     /* Add the unique random value to the hash calculation */
     digest_update_with_colon (da);
     digest_update (da,
                    rnd,
                    rnd_size);
   }
   if ( (MHD_DAUTH_BIND_NONCE_NONE == bind_options) &&
        (0 != saddr_size) )
   {
     /* Add full client address including source port to make unique nonces
      * for requests received exactly at the same time */
     digest_update_with_colon (da);
     digest_update (da,
                    saddr,
                    saddr_size);
   }
   if ( (0 != (bind_options & MHD_DAUTH_BIND_NONCE_CLIENT_IP)) &&
        (0 != saddr_size) )
   {
     /* Add the client's IP address to the hash calculation */
     digest_update_with_colon (da);
     if (AF_INET == saddr->ss_family)
       digest_update (da,
                      &((const struct sockaddr_in *) saddr)->sin_addr,
                      sizeof(((const struct sockaddr_in *) saddr)->sin_addr));
 #ifdef HAVE_INET6
     else if (AF_INET6 == saddr->ss_family)
       digest_update (da,
                      &((const struct sockaddr_in6 *) saddr)->sin6_addr,
                      sizeof(((const struct sockaddr_in6 *) saddr)->sin6_addr));
 #endif /* HAVE_INET6 */
   }
   if ( (MHD_DAUTH_BIND_NONCE_NONE == bind_options) ||
        (0 != (bind_options & MHD_DAUTH_BIND_NONCE_URI)))
   {
     /* Add the request method to the hash calculation */
     digest_update_with_colon (da);
     if (MHD_HTTP_MTHD_OTHER != mthd_e)
     {
       uint8_t mthd_for_hash;
       if (MHD_HTTP_MTHD_HEAD != mthd_e)
         mthd_for_hash = (uint8_t) mthd_e;
       else /* Treat HEAD method in the same way as GET method */
         mthd_for_hash = (uint8_t) MHD_HTTP_MTHD_GET;
       digest_update (da,
                      &mthd_for_hash,
                      sizeof(mthd_for_hash));
     }
     else
       digest_update_str (da, method);
   }
 
   if (0 != (bind_options & MHD_DAUTH_BIND_NONCE_URI))
   {
     /* Add the request URI to the hash calculation */
     digest_update_with_colon (da);
 
     digest_update (da,
                    uri,
                    uri_len);
   }
   if (0 != (bind_options & MHD_DAUTH_BIND_NONCE_URI_PARAMS))
   {
     /* Add the request URI parameters to the hash calculation */
     const struct MHD_HTTP_Req_Header *h;
 
     digest_update_with_colon (da);
     for (h = first_header; NULL != h; h = h->next)
     {
       if (MHD_GET_ARGUMENT_KIND != h->kind)
         continue;
       digest_update (da, "\0", 2);
       if (0 != h->header_size)
         digest_update (da, h->header, h->header_size);
       digest_update (da, "", 1);
       if (0 != h->value_size)
         digest_update (da, h->value, h->value_size);
     }
   }
   if ( (MHD_DAUTH_BIND_NONCE_NONE == bind_options) ||
        (0 != (bind_options & MHD_DAUTH_BIND_NONCE_REALM)))
   {
     /* Add the realm to the hash calculation */
     digest_update_with_colon (da);
     digest_update (da,
                    realm,
                    realm_len);
   }
   if (1)
   {
     uint8_t hash[MAX_DIGEST];
     digest_calc_hash (da, hash);
     MHD_bin_to_hex (hash,
                     digest_get_size (da),
                     nonce);
   }
 }
 
 
 /**
  * Check whether it is possible to use slot in nonce-nc map array.
  *
  * Should be called with mutex held to avoid external modification of
  * the slot data.
  *
  * @param nn the pointer to the nonce-nc slot
  * @param now the current time
  * @param new_nonce the new nonce supposed to be stored in this slot,
  *                  zero-terminated
  * @param new_nonce_len the length of the @a new_nonce in chars, not including
  *                      the terminating zero.
  * @return true if the slot can be used to store the new nonce,
  *         false otherwise.
  */
 static bool
 is_slot_available (const struct MHD_NonceNc *const nn,
                    const uint64_t now,
                    const char *const new_nonce,
                    size_t new_nonce_len)
 {
   uint64_t timestamp;
   bool timestamp_valid;
   mhd_assert (new_nonce_len <= NONCE_STD_LEN (MAX_DIGEST));
   mhd_assert (NONCE_STD_LEN (MAX_DIGEST) <= MAX_DIGEST_NONCE_LENGTH);
   if (0 == nn->nonce[0])
     return true; /* The slot is empty */
 
   if (0 == memcmp (nn->nonce, new_nonce, new_nonce_len))
   {
     /* The slot has the same nonce already. This nonce cannot be registered
      * again as it would just clear 'nc' usage history. */
     return false;
   }
 
   if (0 != nn->nc)
     return true; /* Client already used the nonce in this slot at least
                     one time, re-use the slot */
 
   /* The nonce must be zero-terminated */
   mhd_assert (0 == nn->nonce[sizeof(nn->nonce) - 1]);
   if (0 != nn->nonce[sizeof(nn->nonce) - 1])
     return true; /* Wrong nonce format in the slot */
 
   timestamp_valid = get_nonce_timestamp (nn->nonce, 0, &timestamp);
   mhd_assert (timestamp_valid);
   if (! timestamp_valid)
     return true; /* Invalid timestamp in nonce-nc, should not be possible */
 
   if ((REUSE_TIMEOUT * 1000) < TRIM_TO_TIMESTAMP (now - timestamp))
     return true;
 
   return false;
 }
 
 
 /**
  * Calculate the server nonce so that it mitigates replay attacks and add
  * the new nonce to the nonce-nc map array.
  *
  * @param connection the MHD connection structure
  * @param timestamp the current timestamp
  * @param realm the string of characters that describes the realm of auth
  * @param realm_len the length of the @a realm
  * @param da the digest algorithm to use
  * @param[out] nonce the pointer to a character array for the nonce to put in,
  *                   must provide NONCE_STD_LEN(digest_get_size(da)) bytes,
  *                   result is NOT zero-terminated
  * @return true if the new nonce has been added to the nonce-nc map array,
  *         false otherwise.
  */
 static bool
 calculate_add_nonce (struct MHD_Connection *const connection,
                      uint64_t timestamp,
                      const char *realm,
                      size_t realm_len,
                      struct DigestAlgorithm *da,
                      char *nonce)
 {
   struct MHD_Daemon *const daemon = MHD_get_master (connection->daemon);
   struct MHD_NonceNc *nn;
   const size_t nonce_size = NONCE_STD_LEN (digest_get_size (da));
   bool ret;
 
   mhd_assert (! da->hashing);
   mhd_assert (MAX_DIGEST_NONCE_LENGTH >= nonce_size);
   mhd_assert (0 != nonce_size);
 
   calculate_nonce (timestamp,
                    connection->rq.http_mthd,
                    connection->rq.method,
                    daemon->digest_auth_random,
                    daemon->digest_auth_rand_size,
                    connection->addr,
                    (size_t) connection->addr_len,
                    connection->rq.url,
                    connection->rq.url_len,
                    connection->rq.headers_received,
                    realm,
                    realm_len,
                    daemon->dauth_bind_type,
                    da,
                    nonce);
 
 #ifdef MHD_DIGEST_HAS_EXT_ERROR
   if (digest_ext_error (da))
     return false;
 #endif /* MHD_DIGEST_HAS_EXT_ERROR */
 
   if (0 == daemon->nonce_nc_size)
     return false;
 
   /* Sanity check for values */
   mhd_assert (MAX_DIGEST_NONCE_LENGTH == NONCE_STD_LEN (MAX_DIGEST));
 
   nn = daemon->nnc + get_nonce_nc_idx (daemon->nonce_nc_size,
                                        nonce,
                                        nonce_size);
 
   MHD_mutex_lock_chk_ (&daemon->nnc_lock);
   if (is_slot_available (nn, timestamp, nonce, nonce_size))
   {
     memcpy (nn->nonce,
             nonce,
             nonce_size);
     nn->nonce[nonce_size] = 0;  /* With terminating zero */
     nn->nc = 0;
     nn->nmask = 0;
     ret = true;
   }
   else
     ret = false;
   MHD_mutex_unlock_chk_ (&daemon->nnc_lock);
 
   return ret;
 }
 
 
 MHD_DATA_TRUNCATION_RUNTIME_CHECK_DISABLE_
 
 /**
  * Calculate the server nonce so that it mitigates replay attacks and add
  * the new nonce to the nonce-nc map array.
  *
  * @param connection the MHD connection structure
  * @param realm A string of characters that describes the realm of auth.
  * @param da digest algorithm to use
  * @param[out] nonce the pointer to a character array for the nonce to put in,
  *                   must provide NONCE_STD_LEN(digest_get_size(da)) bytes,
  *                   result is NOT zero-terminated
  */
 static bool
 calculate_add_nonce_with_retry (struct MHD_Connection *const connection,
                                 const char *realm,
                                 struct DigestAlgorithm *da,
                                 char *nonce)
 {
   const uint64_t timestamp1 = MHD_monotonic_msec_counter ();
   const size_t realm_len = strlen (realm);
   mhd_assert (! da->hashing);
 
 #ifdef HAVE_MESSAGES
   if (0 == MHD_get_master (connection->daemon)->digest_auth_rand_size)
     MHD_DLOG (connection->daemon,
               _ ("Random value was not initialised by " \
                  "MHD_OPTION_DIGEST_AUTH_RANDOM or " \
                  "MHD_OPTION_DIGEST_AUTH_RANDOM_COPY, generated nonces " \
                  "are predictable.\n"));
 #endif
 
   if (! calculate_add_nonce (connection, timestamp1, realm, realm_len, da,
                              nonce))
   {
     /* Either:
      * 1. The same nonce was already generated. If it will be used then one
      * of the clients will fail (as no initial 'nc' value could be given to
      * the client, the second client which will use 'nc=00000001' will fail).
      * 2. Another nonce uses the same slot, and this nonce never has been
      * used by the client and this nonce is still fresh enough.
      */
     const size_t digest_size = digest_get_size (da);
     char nonce2[NONCE_STD_LEN (MAX_DIGEST) + 1];
     uint64_t timestamp2;
 #ifdef MHD_DIGEST_HAS_EXT_ERROR
     if (digest_ext_error (da))
       return false; /* No need to re-try */
 #endif /* MHD_DIGEST_HAS_EXT_ERROR */
     if (0 == MHD_get_master (connection->daemon)->nonce_nc_size)
       return false; /* No need to re-try */
 
     timestamp2 = MHD_monotonic_msec_counter ();
     if (timestamp1 == timestamp2)
     {
       /* The timestamps are equal, need to generate some arbitrary
        * difference for nonce. */
       /* As the number is needed only to differentiate clients, weak
        * pseudo-random generators could be used. Seeding is not needed. */
       uint64_t base1;
       uint32_t base2;
       uint16_t base3;
       uint8_t base4;
 #ifdef HAVE_RANDOM
       base1 = ((uint64_t) random ()) ^ UINT64_C (0x54a5acff5be47e63);
       base4 = 0xb8;
 #elif defined(HAVE_RAND)
       base1 = ((uint64_t) rand ()) ^ UINT64_C (0xc4bcf553b12f3965);
       base4 = 0x92;
 #else
       /* Monotonic msec counter alone does not really help here as it is already
          known that this value is not unique. */
       base1 = ((uint64_t) (uintptr_t) nonce2) ^ UINT64_C (0xf2e1b21bc6c92655);
       base2 = ((uint32_t) (base1 >> 32)) ^ ((uint32_t) base1);
       base2 = _MHD_ROTR32 (base2, 4);
       base3 = ((uint16_t) (base2 >> 16)) ^ ((uint16_t) base2);
       base4 = ((uint8_t) (base3 >> 8)) ^ ((uint8_t) base3);
       base1 = ((uint64_t) MHD_monotonic_msec_counter ())
               ^ UINT64_C (0xccab93f72cf5b15);
 #endif
       base2 = ((uint32_t) (base1 >> 32)) ^ ((uint32_t) base1);
       base2 = _MHD_ROTL32 (base2, (((base4 >> 4) ^ base4) % 32));
       base3 = ((uint16_t) (base2 >> 16)) ^ ((uint16_t) base2);
       base4 = ((uint8_t) (base3 >> 8)) ^ ((uint8_t) base3);
       /* Use up to 127 ms difference */
       timestamp2 -= (base4 & DAUTH_JUMPBACK_MAX);
       if (timestamp1 == timestamp2)
         timestamp2 -= 2; /* Fallback value */
     }
     digest_reset (da);
     if (! calculate_add_nonce (connection, timestamp2, realm, realm_len, da,
                                nonce2))
     {
       /* No free slot has been found. Re-tries are expensive, just use
        * the generated nonce. As it is not stored in nonce-nc map array,
        * the next request of the client will be recognized as valid, but 'stale'
        * so client should re-try automatically. */
       return false;
     }
     memcpy (nonce, nonce2, NONCE_STD_LEN (digest_size));
   }
   return true;
 }
 
 
 MHD_DATA_TRUNCATION_RUNTIME_CHECK_RESTORE_
 
 /**
  * Calculate userdigest, return it as binary data.
  *
  * It is equal to H(A1) for non-session algorithms.
  *
  * MHD internal version.
  *
  * @param da the digest algorithm
  * @param username the username to use
  * @param username_len the length of the @a username
  * @param realm the realm to use
  * @param realm_len the length of the @a realm
  * @param password the password, must be zero-terminated
  * @param[out] ha1_bin the output buffer, must have at least
  *                     #digest_get_size(da) bytes available
  */
 _MHD_static_inline void
 calc_userdigest (struct DigestAlgorithm *da,
                  const char *username, const size_t username_len,
                  const char *realm, const size_t realm_len,
                  const char *password,
                  uint8_t *ha1_bin)
 {
   mhd_assert (! da->hashing);
   digest_update (da, username, username_len);
   digest_update_with_colon (da);
   digest_update (da, realm, realm_len);
   digest_update_with_colon (da);
   digest_update_str (da, password);
   digest_calc_hash (da, ha1_bin);
 }
 
 
 /**
  * Calculate userdigest, return it as a binary data.
  *
  * The "userdigest" is the hash of the "username:realm:password" string.
  *
  * The "userdigest" can be used to avoid storing the password in clear text
  * in database/files
  *
  * This function is designed to improve security of stored credentials,
  * the "userdigest" does not improve security of the authentication process.
  *
  * The results can be used to store username & userdigest pairs instead of
  * username & password pairs. To further improve security, application may
  * store username & userhash & userdigest triplets.
  *
  * @param algo3 the digest algorithm
  * @param username the username
  * @param realm the realm
  * @param password the password
  * @param[out] userdigest_bin the output buffer for userdigest;
  *                            if this function succeeds, then this buffer has
  *                            #MHD_digest_get_hash_size(algo3) bytes of
  *                            userdigest upon return
  * @param bin_buf_size the size of the @a userdigest_bin buffer, must be
  *                     at least #MHD_digest_get_hash_size(algo3) bytes long
  * @return MHD_YES on success,
  *         MHD_NO if @a userdigest_bin is too small or if @a algo3 algorithm is
  *         not supported (or external error has occurred,
  *         see #MHD_FEATURE_EXTERN_HASH).
  * @sa #MHD_digest_auth_check_digest3()
  * @note Available since #MHD_VERSION 0x00097701
  * @ingroup authentication
  */
 _MHD_EXTERN enum MHD_Result
 MHD_digest_auth_calc_userdigest (enum MHD_DigestAuthAlgo3 algo3,
                                  const char *username,
                                  const char *realm,
                                  const char *password,
                                  void *userdigest_bin,
                                  size_t bin_buf_size)
 {
   struct DigestAlgorithm da;
   enum MHD_Result ret;
   if (! digest_init_one_time (&da, get_base_digest_algo (algo3)))
     return MHD_NO;
 
   if (digest_get_size (&da) > bin_buf_size)
     ret = MHD_NO;
   else
   {
     calc_userdigest (&da,
                      username,
                      strlen (username),
                      realm,
                      strlen (realm),
                      password,
                      userdigest_bin);
     ret = MHD_YES;
 
 #ifdef MHD_DIGEST_HAS_EXT_ERROR
     if (digest_ext_error (&da))
       ret = MHD_NO;
 #endif /* MHD_DIGEST_HAS_EXT_ERROR */
   }
   digest_deinit (&da);
 
   return ret;
 }
 
 
 /**
  * Calculate userhash, return it as binary data.
  *
  * MHD internal version.
  *
  * @param da the digest algorithm
  * @param username the username to use
  * @param username_len the length of the @a username
  * @param realm the realm to use
  * @param realm_len the length of the @a realm
  * @param[out] digest_bin the output buffer, must have at least
  *                        #MHD_digest_get_hash_size(algo3) bytes available
  */
 _MHD_static_inline void
 calc_userhash (struct DigestAlgorithm *da,
                const char *username, const size_t username_len,
                const char *realm, const size_t realm_len,
                uint8_t *digest_bin)
 {
   mhd_assert (NULL != username);
   mhd_assert (! da->hashing);
   digest_update (da, username, username_len);
   digest_update_with_colon (da);
   digest_update (da, realm, realm_len);
   digest_calc_hash (da, digest_bin);
 }
 
 
 /**
  * Calculate "userhash", return it as binary data.
  *
  * The "userhash" is the hash of the string "username:realm".
  *
  * The "userhash" could be used to avoid sending username in cleartext in Digest
  * Authorization client's header.
  *
  * Userhash is not designed to hide the username in local database or files,
  * as username in cleartext is required for #MHD_digest_auth_check3() function
  * to check the response, but it can be used to hide username in HTTP headers.
  *
  * This function could be used when the new username is added to the username
  * database to save the "userhash" alongside with the username (preferably) or
  * when loading list of the usernames to generate the userhash for every loaded
  * username (this will cause delays at the start with the long lists).
  *
  * Once "userhash" is generated it could be used to identify users by clients
  * with "userhash" support.
  * Avoid repetitive usage of this function for the same username/realm
  * combination as it will cause excessive CPU load; save and re-use the result
  * instead.
  *
  * @param algo3 the algorithm for userhash calculations
  * @param username the username
  * @param realm the realm
  * @param[out] userhash_bin the output buffer for userhash as binary data;
  *                          if this function succeeds, then this buffer has
  *                          #MHD_digest_get_hash_size(algo3) bytes of userhash
  *                          upon return
  * @param bin_buf_size the size of the @a userhash_bin buffer, must be
  *                     at least #MHD_digest_get_hash_size(algo3) bytes long
  * @return MHD_YES on success,
  *         MHD_NO if @a bin_buf_size is too small or if @a algo3 algorithm is
  *         not supported (or external error has occurred,
  *         see #MHD_FEATURE_EXTERN_HASH)
  * @sa #MHD_digest_auth_calc_userhash_hex()
  * @note Available since #MHD_VERSION 0x00097701
  * @ingroup authentication
  */
 _MHD_EXTERN enum MHD_Result
 MHD_digest_auth_calc_userhash (enum MHD_DigestAuthAlgo3 algo3,
                                const char *username,
                                const char *realm,
                                void *userhash_bin,
                                size_t bin_buf_size)
 {
   struct DigestAlgorithm da;
   enum MHD_Result ret;
 
   if (! digest_init_one_time (&da, get_base_digest_algo (algo3)))
     return MHD_NO;
   if (digest_get_size (&da) > bin_buf_size)
     ret = MHD_NO;
   else
   {
     calc_userhash (&da,
                    username,
                    strlen (username),
                    realm,
                    strlen (realm),
                    userhash_bin);
     ret = MHD_YES;
 
 #ifdef MHD_DIGEST_HAS_EXT_ERROR
     if (digest_ext_error (&da))
       ret = MHD_NO;
 #endif /* MHD_DIGEST_HAS_EXT_ERROR */
   }
   digest_deinit (&da);
 
   return ret;
 }
 
 
 /**
  * Calculate "userhash", return it as hexadecimal string.
  *
  * The "userhash" is the hash of the string "username:realm".
  *
  * The "userhash" could be used to avoid sending username in cleartext in Digest
  * Authorization client's header.
  *
  * Userhash is not designed to hide the username in local database or files,
  * as username in cleartext is required for #MHD_digest_auth_check3() function
  * to check the response, but it can be used to hide username in HTTP headers.
  *
  * This function could be used when the new username is added to the username
  * database to save the "userhash" alongside with the username (preferably) or
  * when loading list of the usernames to generate the userhash for every loaded
  * username (this will cause delays at the start with the long lists).
  *
  * Once "userhash" is generated it could be used to identify users by clients
  * with "userhash" support.
  * Avoid repetitive usage of this function for the same username/realm
  * combination as it will cause excessive CPU load; save and re-use the result
  * instead.
  *
  * @param algo3 the algorithm for userhash calculations
  * @param username the username
  * @param realm the realm
  * @param[out] userhash_hex the output buffer for userhash as hex string;
  *                          if this function succeeds, then this buffer has
  *                          #MHD_digest_get_hash_size(algo3)*2 chars long
  *                          userhash zero-terminated string
  * @param bin_buf_size the size of the @a userhash_bin buffer, must be
  *                     at least #MHD_digest_get_hash_size(algo3)*2+1 chars long
  * @return MHD_YES on success,
  *         MHD_NO if @a bin_buf_size is too small or if @a algo3 algorithm is
  *         not supported (or external error has occurred,
  *         see #MHD_FEATURE_EXTERN_HASH).
  * @sa #MHD_digest_auth_calc_userhash()
  * @note Available since #MHD_VERSION 0x00097701
  * @ingroup authentication
  */
 _MHD_EXTERN enum MHD_Result
 MHD_digest_auth_calc_userhash_hex (enum MHD_DigestAuthAlgo3 algo3,
                                    const char *username,
                                    const char *realm,
                                    char *userhash_hex,
                                    size_t hex_buf_size)
 {
   uint8_t userhash_bin[MAX_DIGEST];
   size_t digest_size;
 
   digest_size = digest_get_hash_size (algo3);
   if (digest_size * 2 + 1 > hex_buf_size)
     return MHD_NO;
   if (MHD_NO == MHD_digest_auth_calc_userhash (algo3, username, realm,
                                                userhash_bin, MAX_DIGEST))
     return MHD_NO;
 
   MHD_bin_to_hex_z (userhash_bin, digest_size, userhash_hex);
   return MHD_YES;
 }
 
 
 struct test_header_param
 {
   struct MHD_Connection *connection;
   size_t num_headers;
 };
 
 /**
  * Test if the given key-value pair is in the headers for the
  * given connection.
  *
  * @param cls the test context
  * @param key the key
  * @param key_size number of bytes in @a key
  * @param value the value, can be NULL
  * @param value_size number of bytes in @a value
  * @param kind type of the header
  * @return #MHD_YES if the key-value pair is in the headers,
  *         #MHD_NO if not
  */
 static enum MHD_Result
 test_header (void *cls,
              const char *key,
              size_t key_size,
              const char *value,
              size_t value_size,
              enum MHD_ValueKind kind)
 {
   struct test_header_param *const param = (struct test_header_param *) cls;
   struct MHD_Connection *connection = param->connection;
   struct MHD_HTTP_Req_Header *pos;
   size_t i;
 
   param->num_headers++;
   i = 0;
   for (pos = connection->rq.headers_received; NULL != pos; pos = pos->next)
   {
     if (kind != pos->kind)
       continue;
     if (++i == param->num_headers)
     {
       if (key_size != pos->header_size)
         return MHD_NO;
       if (value_size != pos->value_size)
         return MHD_NO;
       if (0 != key_size)
       {
         mhd_assert (NULL != key);
         mhd_assert (NULL != pos->header);
         if (0 != memcmp (key,
                          pos->header,
                          key_size))
           return MHD_NO;
       }
       if (0 != value_size)
       {
         mhd_assert (NULL != value);
         mhd_assert (NULL != pos->value);
         if (0 != memcmp (value,
                          pos->value,
                          value_size))
           return MHD_NO;
       }
       return MHD_YES;
     }
   }
   return MHD_NO;
 }
 
 
 /**
  * Check that the arguments given by the client as part
  * of the authentication header match the arguments we
  * got as part of the HTTP request URI.
  *
  * @param connection connections with headers to compare against
  * @param args the copy of argument URI string (after "?" in URI), will be
  *             modified by this function
  * @return boolean true if the arguments match,
  *         boolean false if not
  */
 static bool
 check_argument_match (struct MHD_Connection *connection,
                       char *args)
 {
   struct MHD_HTTP_Req_Header *pos;
   enum MHD_Result ret;
   struct test_header_param param;
 
   param.connection = connection;
   param.num_headers = 0;
   ret = MHD_parse_arguments_ (connection,
                               MHD_GET_ARGUMENT_KIND,
                               args,
                               &test_header,
                               &param);
   if (MHD_NO == ret)
   {
     return false;
   }
   /* also check that the number of headers matches */
   for (pos = connection->rq.headers_received; NULL != pos; pos = pos->next)
   {
     if (MHD_GET_ARGUMENT_KIND != pos->kind)
       continue;
     param.num_headers--;
   }
   if (0 != param.num_headers)
   {
     /* argument count mismatch */
     return false;
   }
   return true;
 }
 
 
 /**
  * Check that the URI provided by the client as part
  * of the authentication header match the real HTTP request URI.
  *
  * @param connection connections with headers to compare against
  * @param uri the copy of URI in the authentication header, should point to
  *            modifiable buffer at least @a uri_len + 1 characters long,
  *            will be modified by this function, not valid upon return
  * @param uri_len the length of the @a uri string in characters
  * @return boolean true if the URIs match,
  *         boolean false if not
  */
 static bool
 check_uri_match (struct MHD_Connection *connection, char *uri, size_t uri_len)
 {
   char *qmark;
   char *args;
   struct MHD_Daemon *const daemon = connection->daemon;
 
   uri[uri_len] = 0;
   qmark = memchr (uri,
                   '?',
                   uri_len);
   if (NULL != qmark)
     *qmark = '\0';
 
   /* Need to unescape URI before comparing with connection->url */
   uri_len = daemon->unescape_callback (daemon->unescape_callback_cls,
                                        connection,
                                        uri);
   if ((uri_len != connection->rq.url_len) ||
       (0 != memcmp (uri, connection->rq.url, uri_len)))
   {
 #ifdef HAVE_MESSAGES
     MHD_DLOG (daemon,
               _ ("Authentication failed, URI does not match.\n"));
 #endif
     return false;
   }
 
   args = (NULL != qmark) ? (qmark + 1) : uri + uri_len;
 
   if (! check_argument_match (connection,
                               args) )
   {
 #ifdef HAVE_MESSAGES
     MHD_DLOG (daemon,
               _ ("Authentication failed, arguments do not match.\n"));
 #endif
     return false;
   }
   return true;
 }
 
 
 /**
  * The size of the unquoting buffer in stack
  */
 #define _MHD_STATIC_UNQ_BUFFER_SIZE 128
 
 
 /**
  * Get the pointer to buffer with required size
  * @param tmp1 the first buffer with fixed size
  * @param ptmp2 the pointer to pointer to malloc'ed buffer
  * @param ptmp2_size the pointer to the size of the buffer pointed by @a ptmp2
  * @param required_size the required size in buffer
  * @return the pointer to the buffer or NULL if failed to allocate buffer with
  *         requested size
  */
 static char *
 get_buffer_for_size (char tmp1[_MHD_STATIC_UNQ_BUFFER_SIZE],
                      char **ptmp2,
                      size_t *ptmp2_size,
                      size_t required_size)
 {
   mhd_assert ((0 == *ptmp2_size) || (NULL != *ptmp2));
   mhd_assert ((NULL != *ptmp2) || (0 == *ptmp2_size));
   mhd_assert ((0 == *ptmp2_size) || \
               (_MHD_STATIC_UNQ_BUFFER_SIZE < *ptmp2_size));
 
   if (required_size <= _MHD_STATIC_UNQ_BUFFER_SIZE)
     return tmp1;
 
   if (required_size <= *ptmp2_size)
     return *ptmp2;
 
   if (required_size > _MHD_AUTH_DIGEST_MAX_PARAM_SIZE)
     return NULL;
   if (NULL != *ptmp2)
     free (*ptmp2);
   *ptmp2 = (char *) malloc (required_size);
   if (NULL == *ptmp2)
     *ptmp2_size = 0;
   else
     *ptmp2_size = required_size;
   return *ptmp2;
 }
 
 
 /**
   * The result of parameter unquoting
   */
 enum _MHD_GetUnqResult
 {
   _MHD_UNQ_OK = 0,         /**< Got unquoted string */
   _MHD_UNQ_TOO_LARGE = -7, /**< The string is too large to unquote */
   _MHD_UNQ_OUT_OF_MEM = 3  /**< Out of memory error */
 };
 
 /**
  * Get Digest authorisation parameter as unquoted string.
  * @param param the parameter to process
  * @param tmp1 the small buffer in stack
  * @param ptmp2 the pointer to pointer to malloc'ed buffer
  * @param ptmp2_size the pointer to the size of the buffer pointed by @a ptmp2
  * @param[out] unquoted the pointer to store the result, NOT zero terminated
  * @return enum code indicating result of the process
  */
 static enum _MHD_GetUnqResult
 get_unquoted_param (const struct MHD_RqDAuthParam *param,
                     char tmp1[_MHD_STATIC_UNQ_BUFFER_SIZE],
                     char **ptmp2,
                     size_t *ptmp2_size,
                     struct _MHD_str_w_len *unquoted)
 {
   char *str;
   size_t len;
   mhd_assert (NULL != param->value.str);
   mhd_assert (0 != param->value.len);
 
   if (! param->quoted)
   {
     unquoted->str = param->value.str;
     unquoted->len = param->value.len;
     return _MHD_UNQ_OK;
   }
   /* The value is present and is quoted, needs to be copied and unquoted */
   str = get_buffer_for_size (tmp1, ptmp2, ptmp2_size, param->value.len);
   if (NULL == str)
     return (param->value.len > _MHD_AUTH_DIGEST_MAX_PARAM_SIZE) ?
            _MHD_UNQ_TOO_LARGE : _MHD_UNQ_OUT_OF_MEM;
 
   len = MHD_str_unquote (param->value.str, param->value.len, str);
   unquoted->str = str;
   unquoted->len = len;
   mhd_assert (0 != unquoted->len);
   mhd_assert (unquoted->len < param->value.len);
   return _MHD_UNQ_OK;
 }
 
 
 /**
  * Get copy of Digest authorisation parameter as unquoted string.
  * @param param the parameter to process
  * @param tmp1 the small buffer in stack
  * @param ptmp2 the pointer to pointer to malloc'ed buffer
  * @param ptmp2_size the pointer to the size of the buffer pointed by @a ptmp2
  * @param[out] unquoted the pointer to store the result, NOT zero terminated,
  *                      but with enough space to zero-terminate
  * @return enum code indicating result of the process
  */
 static enum _MHD_GetUnqResult
 get_unquoted_param_copy (const struct MHD_RqDAuthParam *param,
                          char tmp1[_MHD_STATIC_UNQ_BUFFER_SIZE],
                          char **ptmp2,
                          size_t *ptmp2_size,
                          struct _MHD_mstr_w_len *unquoted)
 {
   mhd_assert (NULL != param->value.str);
   mhd_assert (0 != param->value.len);
 
   /* The value is present and is quoted, needs to be copied and unquoted */
   /* Allocate buffer with one more additional byte for zero-termination */
   unquoted->str =
     get_buffer_for_size (tmp1, ptmp2, ptmp2_size, param->value.len + 1);
 
   if (NULL == unquoted->str)
     return (param->value.len + 1 > _MHD_AUTH_DIGEST_MAX_PARAM_SIZE) ?
            _MHD_UNQ_TOO_LARGE : _MHD_UNQ_OUT_OF_MEM;
 
   if (! param->quoted)
   {
     memcpy (unquoted->str, param->value.str, param->value.len);
     unquoted->len = param->value.len;
     return _MHD_UNQ_OK;
   }
 
   unquoted->len =
     MHD_str_unquote (param->value.str, param->value.len, unquoted->str);
   mhd_assert (0 != unquoted->len);
   mhd_assert (unquoted->len < param->value.len);
   return _MHD_UNQ_OK;
 }
 
 
 /**
  * Check whether Digest Auth request parameter is equal to given string
  * @param param the parameter to check
  * @param str the string to compare with, does not need to be zero-terminated
  * @param str_len the length of the @a str
  * @return true is parameter is equal to the given string,
  *         false otherwise
  */
 _MHD_static_inline bool
 is_param_equal (const struct MHD_RqDAuthParam *param,
                 const char *const str,
                 const size_t str_len)
 {
   mhd_assert (NULL != param->value.str);
   mhd_assert (0 != param->value.len);
   if (param->quoted)
     return MHD_str_equal_quoted_bin_n (param->value.str, param->value.len,
                                        str, str_len);
   return (str_len == param->value.len) &&
          (0 == memcmp (str, param->value.str, str_len));
 
 }
 
 
 /**
  * Check whether Digest Auth request parameter is caseless equal to given string
  * @param param the parameter to check
  * @param str the string to compare with, does not need to be zero-terminated
  * @param str_len the length of the @a str
  * @return true is parameter is caseless equal to the given string,
  *         false otherwise
  */
 _MHD_static_inline bool
 is_param_equal_caseless (const struct MHD_RqDAuthParam *param,
                          const char *const str,
                          const size_t str_len)
 {
   mhd_assert (NULL != param->value.str);
   mhd_assert (0 != param->value.len);
   if (param->quoted)
     return MHD_str_equal_caseless_quoted_bin_n (param->value.str,
                                                 param->value.len,
                                                 str,
                                                 str_len);
   return (str_len == param->value.len) &&
          (MHD_str_equal_caseless_bin_n_ (str,
                                          param->value.str,
                                          str_len));
 }
 
 
 /**
  * Authenticates the authorization header sent by the client
  *
  * If RFC2069 mode is allowed by setting bit #MHD_DIGEST_AUTH_QOP_NONE in
  * @a mqop and the client uses this mode, then server generated nonces are
  * used as one-time nonces because nonce-count is not supported in this old RFC.
  * Communication in this mode is very inefficient, especially if the client
  * requests several resources one-by-one as for every request new nonce must be
  * generated and client repeat all requests twice (the first time to get a new
  * nonce and the second time to perform an authorised request).
  *
  * @param connection the MHD connection structure
  * @param realm the realm for authorization of the client
  * @param username the username to be authenticated, must be in clear text
  *                 even if userhash is used by the client
  * @param password the password used in the authentication,
  *                 must be NULL if @a userdigest is not NULL
  * @param userdigest the precalculated binary hash of the string
  *                   "username:realm:password",
  *                   must be NULL if @a password is not NULL
  * @param nonce_timeout the period of seconds since nonce generation, when
  *                      the nonce is recognised as valid and not stale;
  *                      unlike #digest_auth_check_all() zero is used literally
  * @param max_nc the maximum allowed nc (Nonce Count) value, if client's nc
  *               exceeds the specified value then MHD_DAUTH_NONCE_STALE is
  *               returned;
  *               unlike #digest_auth_check_all() zero is treated as "no limit"
  * @param mqop the QOP to use
  * @param malgo3 digest algorithms allowed to use, fail if algorithm specified
  *               by the client is not allowed by this parameter
  * @param[out] pbuf the pointer to pointer to internally malloc'ed buffer,
  *                  to be freed if not NULL upon return
  * @return #MHD_DAUTH_OK if authenticated,
  *         error code otherwise.
  * @ingroup authentication
  */
 static enum MHD_DigestAuthResult
 digest_auth_check_all_inner (struct MHD_Connection *connection,
                              const char *realm,
                              const char *username,
                              const char *password,
                              const uint8_t *userdigest,
                              unsigned int nonce_timeout,
                              uint32_t max_nc,
                              enum MHD_DigestAuthMultiQOP mqop,
                              enum MHD_DigestAuthMultiAlgo3 malgo3,
                              char **pbuf,
                              struct DigestAlgorithm *da)
 {
   struct MHD_Daemon *daemon = MHD_get_master (connection->daemon);
   enum MHD_DigestAuthAlgo3 c_algo; /**< Client's algorithm */
   enum MHD_DigestAuthQOP c_qop; /**< Client's QOP */
   unsigned int digest_size;
   uint8_t hash1_bin[MAX_DIGEST];
   uint8_t hash2_bin[MAX_DIGEST];
 #if 0
   const char *hentity = NULL; /* "auth-int" is not supported */
 #endif
   uint64_t nonce_time;
   uint64_t nci;
   const struct MHD_RqDAuth *params;
   /**
    * Temporal buffer in stack for unquoting and other needs
    */
   char tmp1[_MHD_STATIC_UNQ_BUFFER_SIZE];
   char **const ptmp2 = pbuf;     /**< Temporal malloc'ed buffer for unquoting */
   size_t tmp2_size; /**< The size of @a tmp2 buffer */
   struct _MHD_str_w_len unquoted;
   struct _MHD_mstr_w_len unq_copy;
   enum _MHD_GetUnqResult unq_res;
   size_t username_len;
   size_t realm_len;
 
   mhd_assert ((NULL != password) || (NULL != userdigest));
   mhd_assert (! ((NULL != userdigest) && (NULL != password)));
 
   tmp2_size = 0;
 
   params = MHD_get_rq_dauth_params_ (connection);
   if (NULL == params)
     return MHD_DAUTH_WRONG_HEADER;
 
   /* ** Initial parameters checks and setup ** */
   /* Get client's algorithm */
   c_algo = params->algo3;
   /* Check whether client's algorithm is allowed by function parameter */
   if (((unsigned int) c_algo) !=
       (((unsigned int) c_algo) & ((unsigned int) malgo3)))
     return MHD_DAUTH_WRONG_ALGO;
   if (MHD_DIGEST_AUTH_ALGO3_INVALID == c_algo)
     return MHD_DAUTH_WRONG_ALGO;
   /* Check whether client's algorithm is supported */
   if (0 != (((unsigned int) c_algo) & MHD_DIGEST_AUTH_ALGO3_SESSION))
   {
 #ifdef HAVE_MESSAGES
     MHD_DLOG (connection->daemon,
               _ ("The 'session' algorithms are not supported.\n"));
 #endif /* HAVE_MESSAGES */
     return MHD_DAUTH_WRONG_ALGO;
   }
 #ifndef MHD_MD5_SUPPORT
   if (0 != (((unsigned int) c_algo) & MHD_DIGEST_BASE_ALGO_MD5))
   {
 #ifdef HAVE_MESSAGES
     MHD_DLOG (connection->daemon,
               _ ("The MD5 algorithm is not supported by this MHD build.\n"));
 #endif /* HAVE_MESSAGES */
     return MHD_DAUTH_WRONG_ALGO;
   }
 #endif /* ! MHD_MD5_SUPPORT */
 #ifndef MHD_SHA256_SUPPORT
   if (0 != (((unsigned int) c_algo) & MHD_DIGEST_BASE_ALGO_SHA256))
   {
 #ifdef HAVE_MESSAGES
     MHD_DLOG (connection->daemon,
               _ ("The SHA-256 algorithm is not supported by "
                  "this MHD build.\n"));
 #endif /* HAVE_MESSAGES */
     return MHD_DAUTH_WRONG_ALGO;
   }
 #endif /* ! MHD_SHA256_SUPPORT */
 #ifndef MHD_SHA512_256_SUPPORT
   if (0 != (((unsigned int) c_algo) & MHD_DIGEST_BASE_ALGO_SHA512_256))
   {
 #ifdef HAVE_MESSAGES
     MHD_DLOG (connection->daemon,
               _ ("The SHA-512/256 algorithm is not supported by "
                  "this MHD build.\n"));
 #endif /* HAVE_MESSAGES */
     return MHD_DAUTH_WRONG_ALGO;
   }
 #endif /* ! MHD_SHA512_256_SUPPORT */
   if (! digest_init_one_time (da, get_base_digest_algo (c_algo)))
     MHD_PANIC (_ ("Wrong 'malgo3' value, API violation"));
   /* Check 'mqop' value */
   c_qop = params->qop;
   /* Check whether client's QOP is allowed by function parameter */
   if (((unsigned int) c_qop) !=
       (((unsigned int) c_qop) & ((unsigned int) mqop)))
     return MHD_DAUTH_WRONG_QOP;
   /* The numeric value of #MHD_DIGEST_AUTH_QOP_INVALID is zero, therefore
      the bitmask check above passes it for any 'mqop' value. */
   if (MHD_DIGEST_AUTH_QOP_INVALID == c_qop)
     return MHD_DAUTH_WRONG_QOP;
   if (0 != (((unsigned int) c_qop) & MHD_DIGEST_AUTH_QOP_AUTH_INT))
   {
 #ifdef HAVE_MESSAGES
     MHD_DLOG (connection->daemon,
               _ ("The 'auth-int' QOP is not supported.\n"));
 #endif /* HAVE_MESSAGES */
     return MHD_DAUTH_WRONG_QOP;
   }
 #ifdef HAVE_MESSAGES
   if ((MHD_DIGEST_AUTH_QOP_NONE == c_qop) &&
       (0 == (((unsigned int) c_algo) & MHD_DIGEST_BASE_ALGO_MD5)))
     MHD_DLOG (connection->daemon,
               _ ("RFC2069 with SHA-256 or SHA-512/256 algorithm is " \
                  "non-standard extension.\n"));
 #endif /* HAVE_MESSAGES */
 
   digest_size = digest_get_size (da);
 
   /* ** A quick check for presence of all required parameters ** */
 
   if ((NULL == params->username.value.str) &&
       (NULL == params->username_ext.value.str))
     return MHD_DAUTH_WRONG_USERNAME;
   else if ((NULL != params->username.value.str) &&
            (NULL != params->username_ext.value.str))
     return MHD_DAUTH_WRONG_USERNAME; /* Parameters cannot be used together */
   else if ((NULL != params->username.value.str) &&
            (0 == params->username.value.len))
     return MHD_DAUTH_WRONG_USERNAME;  /* Empty username */
   else if ((NULL != params->username_ext.value.str) &&
            (MHD_DAUTH_EXT_PARAM_MIN_LEN > params->username_ext.value.len))
     return MHD_DAUTH_WRONG_USERNAME;  /* Broken extended notation */
   else if (params->userhash && (NULL == params->username.value.str))
     return MHD_DAUTH_WRONG_USERNAME;  /* Userhash cannot be used with extended notation */
   else if (params->userhash && (digest_size * 2 > params->username.value.len))
     return MHD_DAUTH_WRONG_USERNAME;  /* Too few chars for correct userhash */
   else if (params->userhash && (digest_size * 4 < params->username.value.len))
     return MHD_DAUTH_WRONG_USERNAME;  /* Too many chars for correct userhash */
 
   if (NULL == params->realm.value.str)
     return MHD_DAUTH_WRONG_REALM;
   else if (0 == params->realm.value.len)
     return MHD_DAUTH_WRONG_REALM;  /* Empty realm */
   else if (((NULL == userdigest) || params->userhash) &&
            (_MHD_AUTH_DIGEST_MAX_PARAM_SIZE < params->realm.value.len))
     return MHD_DAUTH_TOO_LARGE; /* Realm is too large and should be used in hash calculations */
 
   if (MHD_DIGEST_AUTH_QOP_NONE != c_qop)
   {
     if (NULL == params->nc.value.str)
       return MHD_DAUTH_WRONG_HEADER;
     else if (0 == params->nc.value.len)
       return MHD_DAUTH_WRONG_HEADER;
     else if (4 * 8 < params->nc.value.len) /* Four times more than needed */
       return MHD_DAUTH_WRONG_HEADER;
 
     if (NULL == params->cnonce.value.str)
       return MHD_DAUTH_WRONG_HEADER;
     else if (0 == params->cnonce.value.len)
       return MHD_DAUTH_WRONG_HEADER;
     else if (_MHD_AUTH_DIGEST_MAX_PARAM_SIZE < params->cnonce.value.len)
       return MHD_DAUTH_TOO_LARGE;
   }
 
   /* The QOP parameter was checked already */
 
   if (NULL == params->uri.value.str)
     return MHD_DAUTH_WRONG_URI;
   else if (0 == params->uri.value.len)
     return MHD_DAUTH_WRONG_URI;
   else if (_MHD_AUTH_DIGEST_MAX_PARAM_SIZE < params->uri.value.len)
     return MHD_DAUTH_TOO_LARGE;
 
   if (NULL == params->nonce.value.str)
     return MHD_DAUTH_NONCE_WRONG;
   else if (0 == params->nonce.value.len)
     return MHD_DAUTH_NONCE_WRONG;
   else if (NONCE_STD_LEN (digest_size) * 2 < params->nonce.value.len)
     return MHD_DAUTH_NONCE_WRONG;
 
   if (NULL == params->response.value.str)
     return MHD_DAUTH_RESPONSE_WRONG;
   else if (0 == params->response.value.len)
     return MHD_DAUTH_RESPONSE_WRONG;
   else if (digest_size * 4 < params->response.value.len)
     return MHD_DAUTH_RESPONSE_WRONG;
 
   /* ** Check simple parameters match ** */
 
   /* Check 'algorithm' */
   /* The 'algorithm' was checked at the start of the function */
   /* 'algorithm' valid */
 
   /* Check 'qop' */
   /* The 'qop' was checked at the start of the function */
   /* 'qop' valid */
 
   /* Check 'realm' */
   realm_len = strlen (realm);
   if (! is_param_equal (&params->realm, realm, realm_len))
     return MHD_DAUTH_WRONG_REALM;
   /* 'realm' valid */
 
   /* Check 'username' */
   username_len = strlen (username);
   if (! params->userhash)
   {
     if (NULL != params->username.value.str)
     { /* Username in standard notation */
       if (! is_param_equal (&params->username, username, username_len))
         return MHD_DAUTH_WRONG_USERNAME;
     }
     else
     { /* Username in extended notation */
       char *r_uname;
       size_t buf_size = params->username_ext.value.len;
       ssize_t res;
 
       mhd_assert (NULL != params->username_ext.value.str);
       mhd_assert (MHD_DAUTH_EXT_PARAM_MIN_LEN <= buf_size); /* It was checked already */
       buf_size += 1; /* For zero-termination */
       buf_size -= MHD_DAUTH_EXT_PARAM_MIN_LEN;
       r_uname = get_buffer_for_size (tmp1, ptmp2, &tmp2_size, buf_size);
       if (NULL == r_uname)
         return (_MHD_AUTH_DIGEST_MAX_PARAM_SIZE < buf_size) ?
                MHD_DAUTH_TOO_LARGE : MHD_DAUTH_ERROR;
       res = get_rq_extended_uname_copy_z (params->username_ext.value.str,
                                           params->username_ext.value.len,
                                           r_uname, buf_size);
       if (0 > res)
         return MHD_DAUTH_WRONG_HEADER; /* Broken extended notation */
       if ((username_len != (size_t) res) ||
           (0 != memcmp (username, r_uname, username_len)))
         return MHD_DAUTH_WRONG_USERNAME;
     }
   }
   else
   { /* Userhash */
     mhd_assert (NULL != params->username.value.str);
     calc_userhash (da, username, username_len, realm, realm_len, hash1_bin);
 #ifdef MHD_DIGEST_HAS_EXT_ERROR
     if (digest_ext_error (da))
       return MHD_DAUTH_ERROR;
 #endif /* MHD_DIGEST_HAS_EXT_ERROR */
     /* MHD_bin_to_hex()
        takes no output size and writes exactly 2 * digest_size bytes into
        this fixed-size stack buffer */
     MHD_CHECK_ (connection->daemon,
                 (2 * digest_size) <= sizeof (tmp1),
                 return MHD_DAUTH_ERROR);
     MHD_bin_to_hex (hash1_bin, digest_size, tmp1);
     if (! is_param_equal_caseless (&params->username, tmp1, 2 * digest_size))
       return MHD_DAUTH_WRONG_USERNAME;
     /* To simplify the logic, the digest is reset here instead of resetting
        before the next hash calculation. */
     digest_reset (da);
   }
   /* 'username' valid */
 
   /* ** Do basic nonce and nonce-counter checks (size, timestamp) ** */
 
   /* Get 'nc' digital value */
   if (MHD_DIGEST_AUTH_QOP_NONE != c_qop)
   {
 
     unq_res = get_unquoted_param (&params->nc, tmp1, ptmp2, &tmp2_size,
                                   &unquoted);
     if (_MHD_UNQ_OK != unq_res)
       return MHD_DAUTH_ERROR;
 
     if (unquoted.len != MHD_strx_to_uint64_n_ (unquoted.str,
                                                unquoted.len,
                                                &nci))
     {
 #ifdef HAVE_MESSAGES
       MHD_DLOG (daemon,
                 _ ("Authentication failed, invalid nc format.\n"));
 #endif
       return MHD_DAUTH_WRONG_HEADER;   /* invalid nonce format */
     }
     if (0 == nci)
     {
 #ifdef HAVE_MESSAGES
       MHD_DLOG (daemon,
                 _ ("Authentication failed, invalid 'nc' value.\n"));
 #endif
       return MHD_DAUTH_WRONG_HEADER;   /* invalid nc value */
     }
     if ((0 != max_nc) && (max_nc < nci))
       return MHD_DAUTH_NONCE_STALE;    /* Too large 'nc' value */
   }
   else
     nci = 1; /* Force 'nc' value */
   /* Got 'nc' digital value */
 
   /* Get 'nonce' with basic checks */
   unq_res = get_unquoted_param (&params->nonce, tmp1, ptmp2, &tmp2_size,
                                 &unquoted);
   if (_MHD_UNQ_OK != unq_res)
     return MHD_DAUTH_ERROR;
 
   if ((NONCE_STD_LEN (digest_size) != unquoted.len) ||
       (! get_nonce_timestamp (unquoted.str, unquoted.len, &nonce_time)))
   {
 #ifdef HAVE_MESSAGES
     MHD_DLOG (daemon,
               _ ("Authentication failed, invalid nonce format.\n"));
 #endif
     return MHD_DAUTH_NONCE_WRONG;
   }
 
   if (1)
   {
     uint64_t t;
 
     t = MHD_monotonic_msec_counter ();
     /*
      * First level vetting for the nonce validity: if the timestamp
      * attached to the nonce exceeds `nonce_timeout', then the nonce is
      * stale.
      */
     if (TRIM_TO_TIMESTAMP (t - nonce_time) > (nonce_timeout * 1000))
       return MHD_DAUTH_NONCE_STALE; /* too old */
   }
   if (1)
   {
     enum MHD_CheckNonceNC_ nonce_nc_check;
     /*
      * Checking if that combination of nonce and nc is sound
      * and not a replay attack attempt. Refuse if nonce was not
      * generated previously.
      */
     nonce_nc_check = check_nonce_nc (connection,
                                      unquoted.str,
                                      NONCE_STD_LEN (digest_size),
                                      nonce_time,
                                      nci);
     if (MHD_CHECK_NONCENC_STALE == nonce_nc_check)
     {
 #ifdef HAVE_MESSAGES
       if (MHD_DIGEST_AUTH_QOP_NONE != c_qop)
         MHD_DLOG (daemon,
                   _ ("Stale nonce received. If this happens a lot, you should "
                      "probably increase the size of the nonce array.\n"));
       else
         MHD_DLOG (daemon,
                   _ ("Stale nonce received. This is expected when client " \
                      "uses RFC2069-compatible mode and makes more than one " \
                      "request.\n"));
 #endif
       return MHD_DAUTH_NONCE_STALE;
     }
     else if (MHD_CHECK_NONCENC_WRONG == nonce_nc_check)
     {
 #ifdef HAVE_MESSAGES
       MHD_DLOG (daemon,
                 _ ("Received nonce that was not "
                    "generated by MHD. This may indicate an attack attempt.\n"));
 #endif
       return MHD_DAUTH_NONCE_WRONG;
     }
     mhd_assert (MHD_CHECK_NONCENC_OK == nonce_nc_check);
   }
   /* The nonce was generated by MHD, is not stale and nonce-nc combination was
      not used before */
 
   /* ** Build H(A2) and check URI match in the header and in the request ** */
 
   /* Get 'uri' */
   mhd_assert (! da->hashing);
   digest_update_str (da, connection->rq.method);
   digest_update_with_colon (da);
 #if 0
   /* TODO: add support for "auth-int" */
   digest_update_str (da, hentity);
   digest_update_with_colon (da);
 #endif
   unq_res = get_unquoted_param_copy (&params->uri, tmp1, ptmp2, &tmp2_size,
                                      &unq_copy);
   if (_MHD_UNQ_OK != unq_res)
     return MHD_DAUTH_ERROR;
 
   digest_update (da, unq_copy.str, unq_copy.len);
   /* The next check will modify copied URI string */
   if (! check_uri_match (connection, unq_copy.str, unq_copy.len))
     return MHD_DAUTH_WRONG_URI;
   digest_calc_hash (da, hash2_bin);
 #ifdef MHD_DIGEST_HAS_EXT_ERROR
   /* Skip digest calculation external error check, the next one checks both */
 #endif /* MHD_DIGEST_HAS_EXT_ERROR */
   /* Got H(A2) */
 
   /* ** Build H(A1) ** */
   if (NULL == userdigest)
   {
     mhd_assert (! da->hashing);
     digest_reset (da);
     calc_userdigest (da,
                      username, username_len,
                      realm, realm_len,
                      password,
                      hash1_bin);
   }
   /* TODO: support '-sess' versions */
 #ifdef MHD_DIGEST_HAS_EXT_ERROR
   if (digest_ext_error (da))
     return MHD_DAUTH_ERROR;
 #endif /* MHD_DIGEST_HAS_EXT_ERROR */
   /* Got H(A1) */
 
   /* **  Check 'response' ** */
 
   mhd_assert (! da->hashing);
   digest_reset (da);
   /* Update digest with H(A1) */
   MHD_CHECK_ (connection->daemon,
               (digest_size * 2) <= sizeof (tmp1),
               return MHD_DAUTH_ERROR);
   if (NULL == userdigest)
     MHD_bin_to_hex (hash1_bin, digest_size, tmp1);
   else
     MHD_bin_to_hex (userdigest, digest_size, tmp1);
   digest_update (da, (const uint8_t *) tmp1, digest_size * 2);
 
   /* H(A1) is not needed anymore, reuse the buffer.
    * Use hash1_bin for the client's 'response' decoded to binary form. */
   unq_res = get_unquoted_param (&params->response, tmp1, ptmp2, &tmp2_size,
                                 &unquoted);
   if (_MHD_UNQ_OK != unq_res)
     return MHD_DAUTH_ERROR;
   if (unquoted.len > MAX_AUTH_RESPONSE_LENGTH)
     return MHD_DAUTH_ERROR;
   if (digest_size !=
       MHD_hex_to_bin (unquoted.str,
                       unquoted.len,
                       hash1_bin))
     return MHD_DAUTH_RESPONSE_WRONG;
 
   /* Update digest with ':' */
   digest_update_with_colon (da);
   /* Update digest with 'nonce' text value */
   unq_res = get_unquoted_param (&params->nonce, tmp1, ptmp2, &tmp2_size,
                                 &unquoted);
   if (_MHD_UNQ_OK != unq_res)
     return MHD_DAUTH_ERROR;
   digest_update (da, (const uint8_t *) unquoted.str, unquoted.len);
   /* Update digest with ':' */
   digest_update_with_colon (da);
   if (MHD_DIGEST_AUTH_QOP_NONE != c_qop)
   {
     /* Update digest with 'nc' text value */
     unq_res = get_unquoted_param (&params->nc, tmp1, ptmp2, &tmp2_size,
                                   &unquoted);
     if (_MHD_UNQ_OK != unq_res)
       return MHD_DAUTH_ERROR;
     digest_update (da, (const uint8_t *) unquoted.str, unquoted.len);
     /* Update digest with ':' */
     digest_update_with_colon (da);
     /* Update digest with 'cnonce' value */
     unq_res = get_unquoted_param (&params->cnonce, tmp1, ptmp2, &tmp2_size,
                                   &unquoted);
     if (_MHD_UNQ_OK != unq_res)
       return MHD_DAUTH_ERROR;
     digest_update (da, (const uint8_t *) unquoted.str, unquoted.len);
     /* Update digest with ':' */
     digest_update_with_colon (da);
     /* Update digest with 'qop' value */
     unq_res = get_unquoted_param (&params->qop_raw, tmp1, ptmp2, &tmp2_size,
                                   &unquoted);
     if (_MHD_UNQ_OK != unq_res)
       return MHD_DAUTH_ERROR;
     digest_update (da, (const uint8_t *) unquoted.str, unquoted.len);
     /* Update digest with ':' */
     digest_update_with_colon (da);
   }
   /* Update digest with H(A2) */
   MHD_bin_to_hex (hash2_bin,
                   digest_size,
                   tmp1);
   digest_update (da,
                  (const uint8_t *) tmp1,
                  digest_size * 2);
 
   /* H(A2) is not needed anymore, reuse the buffer.
    * Use hash2_bin for the calculated response in binary form */
   digest_calc_hash (da, hash2_bin);
 #ifdef MHD_DIGEST_HAS_EXT_ERROR
   if (digest_ext_error (da))
     return MHD_DAUTH_ERROR;
 #endif /* MHD_DIGEST_HAS_EXT_ERROR */
 
   if (0 != memcmp (hash1_bin,
                    hash2_bin,
                    digest_size))
     return MHD_DAUTH_RESPONSE_WRONG;
 
   if (MHD_DAUTH_BIND_NONCE_NONE != daemon->dauth_bind_type)
   {
     mhd_assert (sizeof(tmp1) >= (NONCE_STD_LEN (digest_size) + 1));
     /* It was already checked that 'nonce' (including timestamp) was generated
        by MHD. */
     mhd_assert (! da->hashing);
     digest_reset (da);
     calculate_nonce (nonce_time,
                      connection->rq.http_mthd,
                      connection->rq.method,
                      daemon->digest_auth_random,
                      daemon->digest_auth_rand_size,
                      connection->addr,
                      (size_t) connection->addr_len,
                      connection->rq.url,
                      connection->rq.url_len,
                      connection->rq.headers_received,
                      realm,
                      realm_len,
                      daemon->dauth_bind_type,
                      da,
                      tmp1);
 
 #ifdef MHD_DIGEST_HAS_EXT_ERROR
     if (digest_ext_error (da))
       return MHD_DAUTH_ERROR;
 #endif /* MHD_DIGEST_HAS_EXT_ERROR */
 
     if (! is_param_equal (&params->nonce, tmp1,
                           NONCE_STD_LEN (digest_size)))
       return MHD_DAUTH_NONCE_OTHER_COND;
     /* The 'nonce' was generated in the same conditions */
   }
 
   return MHD_DAUTH_OK;
 }
 
 
 /**
  * Authenticates the authorization header sent by the client
  *
  * If RFC2069 mode is allowed by setting bit #MHD_DIGEST_AUTH_QOP_NONE in
  * @a mqop and the client uses this mode, then server generated nonces are
  * used as one-time nonces because nonce-count is not supported in this old RFC.
  * Communication in this mode is very inefficient, especially if the client
  * requests several resources one-by-one as for every request new nonce must be
  * generated and client repeat all requests twice (the first time to get a new
  * nonce and the second time to perform an authorised request).
  *
  * @param connection the MHD connection structure
  * @param realm the realm for authorization of the client
  * @param username the username to be authenticated, must be in clear text
  *                 even if userhash is used by the client
  * @param password the password used in the authentication,
  *                 must be NULL if @a userdigest is not NULL
  * @param userdigest the precalculated binary hash of the string
  *                   "username:realm:password",
  *                   must be NULL if @a password is not NULL
  * @param nonce_timeout the period of seconds since nonce generation, when
  *                      the nonce is recognised as valid and not stale;
  *                      if set to zero then daemon's default value is used
  * @param max_nc the maximum allowed nc (Nonce Count) value, if client's nc
  *               exceeds the specified value then MHD_DAUTH_NONCE_STALE is
  *               returned;
  *               if set to zero then daemon's default value is used
  * @param mqop the QOP to use
  * @param malgo3 digest algorithms allowed to use, fail if algorithm specified
  *               by the client is not allowed by this parameter
  * @return #MHD_DAUTH_OK if authenticated,
  *         error code otherwise.
  * @ingroup authentication
  */
 static enum MHD_DigestAuthResult
 digest_auth_check_all (struct MHD_Connection *connection,
                        const char *realm,
                        const char *username,
                        const char *password,
                        const uint8_t *userdigest,
                        unsigned int nonce_timeout,
                        uint32_t max_nc,
                        enum MHD_DigestAuthMultiQOP mqop,
                        enum MHD_DigestAuthMultiAlgo3 malgo3)
 {
   enum MHD_DigestAuthResult res;
   char *buf;
   struct DigestAlgorithm da;
 
   buf = NULL;
   digest_setup_zero (&da);
   if (0 == nonce_timeout)
     nonce_timeout = connection->daemon->dauth_def_nonce_timeout;
   if (0 == max_nc)
     max_nc = connection->daemon->dauth_def_max_nc;
   res = digest_auth_check_all_inner (connection, realm, username, password,
                                      userdigest,
                                      nonce_timeout,
                                      max_nc, mqop, malgo3,
                                      &buf, &da);
   digest_deinit (&da);
   if (NULL != buf)
     free (buf);
 
   return res;
 }
 
 
 /**
  * Authenticates the authorization header sent by the client.
  * Uses #MHD_DIGEST_ALG_MD5 (for now, for backwards-compatibility).
  * Note that this MAY change to #MHD_DIGEST_ALG_AUTO in the future.
  * If you want to be sure you get MD5, use #MHD_digest_auth_check2()
  * and specify MD5 explicitly.
  *
  * @param connection The MHD connection structure
  * @param realm The realm presented to the client
  * @param username The username needs to be authenticated
  * @param password The password used in the authentication
  * @param nonce_timeout The amount of time for a nonce to be
  *      invalid in seconds
  * @return #MHD_YES if authenticated, #MHD_NO if not,
  *         #MHD_INVALID_NONCE if nonce is invalid or stale
  * @deprecated use MHD_digest_auth_check3()
  * @ingroup authentication
  */
 _MHD_EXTERN int
 MHD_digest_auth_check (struct MHD_Connection *connection,
                        const char *realm,
                        const char *username,
                        const char *password,
                        unsigned int nonce_timeout)
 {
   return MHD_digest_auth_check2 (connection,
                                  realm,
                                  username,
                                  password,
                                  nonce_timeout,
                                  MHD_DIGEST_ALG_MD5);
 }
 
 
 /**
  * Authenticates the authorization header sent by the client.
  *
  * If RFC2069 mode is allowed by setting bit #MHD_DIGEST_AUTH_QOP_NONE in
  * @a mqop and the client uses this mode, then server generated nonces are
  * used as one-time nonces because nonce-count is not supported in this old RFC.
  * Communication in this mode is very inefficient, especially if the client
  * requests several resources one-by-one as for every request a new nonce must
  * be generated and client repeats all requests twice (first time to get a new
  * nonce and second time to perform an authorised request).
  *
  * @param connection the MHD connection structure
  * @param realm the realm for authorization of the client
  * @param username the username to be authenticated, must be in clear text
  *                 even if userhash is used by the client
  * @param password the password matching the @a username (and the @a realm)
  * @param nonce_timeout the period of seconds since nonce generation, when
  *                      the nonce is recognised as valid and not stale;
  *                      if zero is specified then daemon default value is used.
  * @param max_nc the maximum allowed nc (Nonce Count) value, if client's nc
  *               exceeds the specified value then MHD_DAUTH_NONCE_STALE is
  *               returned;
  *               if zero is specified then daemon default value is used.
  * @param mqop the QOP to use
  * @param malgo3 digest algorithms allowed to use, fail if algorithm used
  *               by the client is not allowed by this parameter
  * @return #MHD_DAUTH_OK if authenticated,
  *         the error code otherwise
  * @note Available since #MHD_VERSION 0x00097708
  * @ingroup authentication
  */
 _MHD_EXTERN enum MHD_DigestAuthResult
 MHD_digest_auth_check3 (struct MHD_Connection *connection,
                         const char *realm,
                         const char *username,
                         const char *password,
                         unsigned int nonce_timeout,
                         uint32_t max_nc,
                         enum MHD_DigestAuthMultiQOP mqop,
                         enum MHD_DigestAuthMultiAlgo3 malgo3)
 {
   mhd_assert (NULL != password);
 
   return digest_auth_check_all (connection,
                                 realm,
                                 username,
                                 password,
                                 NULL,
                                 nonce_timeout,
                                 max_nc,
                                 mqop,
                                 malgo3);
 }
 
 
 /**
  * Authenticates the authorization header sent by the client by using
  * hash of "username:realm:password".
  *
  * If RFC2069 mode is allowed by setting bit #MHD_DIGEST_AUTH_QOP_NONE in
  * @a mqop and the client uses this mode, then server generated nonces are
  * used as one-time nonces because nonce-count is not supported in this old RFC.
  * Communication in this mode is very inefficient, especially if the client
  * requests several resources one-by-one as for every request a new nonce must
  * be generated and client repeats all requests twice (first time to get a new
  * nonce and second time to perform an authorised request).
  *
  * @param connection the MHD connection structure
  * @param realm the realm for authorization of the client
  * @param username the username to be authenticated, must be in clear text
  *                 even if userhash is used by the client
  * @param userdigest the precalculated binary hash of the string
  *                   "username:realm:password",
  *                   see #MHD_digest_auth_calc_userdigest()
  * @param userdigest_size the size of the @a userdigest in bytes, must match the
  *                        hashing algorithm (see #MHD_MD5_DIGEST_SIZE,
  *                        #MHD_SHA256_DIGEST_SIZE, #MHD_SHA512_256_DIGEST_SIZE,
  *                        #MHD_digest_get_hash_size())
  * @param nonce_timeout the period of seconds since nonce generation, when
  *                      the nonce is recognised as valid and not stale;
  *                      if zero is specified then daemon default value is used.
  * @param max_nc the maximum allowed nc (Nonce Count) value, if client's nc
  *               exceeds the specified value then MHD_DAUTH_NONCE_STALE is
  *               returned;
  *               if zero is specified then daemon default value is used.
  * @param mqop the QOP to use
  * @param malgo3 digest algorithms allowed to use, fail if algorithm used
  *               by the client is not allowed by this parameter;
  *               more than one base algorithms (MD5, SHA-256, SHA-512/256)
  *               cannot be used at the same time for this function
  *               as @a userdigest must match specified algorithm
  * @return #MHD_DAUTH_OK if authenticated,
  *         the error code otherwise
  * @sa #MHD_digest_auth_calc_userdigest()
  * @note Available since #MHD_VERSION 0x00097708
  * @ingroup authentication
  */
 _MHD_EXTERN enum MHD_DigestAuthResult
 MHD_digest_auth_check_digest3 (struct MHD_Connection *connection,
                                const char *realm,
                                const char *username,
                                const void *userdigest,
                                size_t userdigest_size,
                                unsigned int nonce_timeout,
                                uint32_t max_nc,
                                enum MHD_DigestAuthMultiQOP mqop,
                                enum MHD_DigestAuthMultiAlgo3 malgo3)
 {
   if (1 != (((0 != (malgo3 & MHD_DIGEST_BASE_ALGO_MD5)) ? 1 : 0)
             + ((0 != (malgo3 & MHD_DIGEST_BASE_ALGO_SHA256)) ? 1 : 0)
             + ((0 != (malgo3 & MHD_DIGEST_BASE_ALGO_SHA512_256)) ? 1 : 0)))
     MHD_PANIC (_ ("Wrong 'malgo3' value, only one base hashing algorithm " \
                   "(MD5, SHA-256 or SHA-512/256) must be specified, " \
                   "API violation"));
 
 #ifndef MHD_MD5_SUPPORT
   if (0 != (((unsigned int) malgo3) & MHD_DIGEST_BASE_ALGO_MD5))
   {
 #ifdef HAVE_MESSAGES
     MHD_DLOG (connection->daemon,
               _ ("The MD5 algorithm is not supported by this MHD build.\n"));
 #endif /* HAVE_MESSAGES */
     return MHD_DAUTH_WRONG_ALGO;
   }
 #endif /* ! MHD_MD5_SUPPORT */
 #ifndef MHD_SHA256_SUPPORT
   if (0 != (((unsigned int) malgo3) & MHD_DIGEST_BASE_ALGO_SHA256))
   {
 #ifdef HAVE_MESSAGES
     MHD_DLOG (connection->daemon,
               _ ("The SHA-256 algorithm is not supported by "
                  "this MHD build.\n"));
 #endif /* HAVE_MESSAGES */
     return MHD_DAUTH_WRONG_ALGO;
   }
 #endif /* ! MHD_SHA256_SUPPORT */
 #ifndef MHD_SHA512_256_SUPPORT
   if (0 != (((unsigned int) malgo3) & MHD_DIGEST_BASE_ALGO_SHA512_256))
   {
 #ifdef HAVE_MESSAGES
     MHD_DLOG (connection->daemon,
               _ ("The SHA-512/256 algorithm is not supported by "
                  "this MHD build.\n"));
 #endif /* HAVE_MESSAGES */
     return MHD_DAUTH_WRONG_ALGO;
   }
 #endif /* ! MHD_SHA512_256_SUPPORT */
 
   if (digest_get_hash_size ((enum MHD_DigestAuthAlgo3) malgo3) !=
       userdigest_size)
     MHD_PANIC (_ ("Wrong 'userdigest_size' value, does not match 'malgo3', "
                   "API violation"));
 
   return digest_auth_check_all (connection,
                                 realm,
                                 username,
                                 NULL,
                                 (const uint8_t *) userdigest,
                                 nonce_timeout,
                                 max_nc,
                                 mqop,
                                 malgo3);
 }
 
 
 /**
  * Authenticates the authorization header sent by the client.
  *
  * @param connection The MHD connection structure
  * @param realm The realm presented to the client
  * @param username The username needs to be authenticated
  * @param password The password used in the authentication
  * @param nonce_timeout The amount of time for a nonce to be
  *      invalid in seconds
  * @param algo digest algorithms allowed for verification
  * @return #MHD_YES if authenticated, #MHD_NO if not,
  *         #MHD_INVALID_NONCE if nonce is invalid or stale
  * @note Available since #MHD_VERSION 0x00096200
  * @deprecated use MHD_digest_auth_check3()
  * @ingroup authentication
  */
 _MHD_EXTERN int
 MHD_digest_auth_check2 (struct MHD_Connection *connection,
                         const char *realm,
                         const char *username,
                         const char *password,
                         unsigned int nonce_timeout,
                         enum MHD_DigestAuthAlgorithm algo)
 {
   enum MHD_DigestAuthResult res;
   enum MHD_DigestAuthMultiAlgo3 malgo3;
 
   if (MHD_DIGEST_ALG_AUTO == algo)
     malgo3 = MHD_DIGEST_AUTH_MULT_ALGO3_ANY_NON_SESSION;
   else if (MHD_DIGEST_ALG_MD5 == algo)
     malgo3 = MHD_DIGEST_AUTH_MULT_ALGO3_MD5;
   else if (MHD_DIGEST_ALG_SHA256 == algo)
     malgo3 = MHD_DIGEST_AUTH_MULT_ALGO3_SHA256;
   else
     MHD_PANIC (_ ("Wrong 'algo' value, API violation"));
 
   res = MHD_digest_auth_check3 (connection,
                                 realm,
                                 username,
                                 password,
                                 nonce_timeout,
                                 0, MHD_DIGEST_AUTH_MULT_QOP_AUTH,
                                 malgo3);
   if (MHD_DAUTH_OK == res)
     return MHD_YES;
   else if ((MHD_DAUTH_NONCE_STALE == res) || (MHD_DAUTH_NONCE_WRONG == res) ||
            (MHD_DAUTH_NONCE_OTHER_COND == res) )
     return MHD_INVALID_NONCE;
   return MHD_NO;
 
 }
 
 
 /**
  * Authenticates the authorization header sent by the client.
  *
  * @param connection The MHD connection structure
  * @param realm The realm presented to the client
  * @param username The username needs to be authenticated
  * @param digest An `unsigned char *' pointer to the binary MD5 sum
  *      for the precalculated hash value "username:realm:password"
  *      of @a digest_size bytes
  * @param digest_size number of bytes in @a digest (size must match @a algo!)
  * @param nonce_timeout The amount of time for a nonce to be
  *      invalid in seconds
  * @param algo digest algorithm allowed for verification; exactly one
  *      algorithm must be named, as @a digest is a hash produced by one
  *      specific algorithm.  #MHD_DIGEST_ALG_AUTO cannot be used here
  *      and makes this function return #MHD_NO
  * @return #MHD_YES if authenticated, #MHD_NO if not,
  *         #MHD_INVALID_NONCE if nonce is invalid or stale
  * @note Available since #MHD_VERSION 0x00096200
  * @deprecated use MHD_digest_auth_check_digest3()
  * @ingroup authentication
  */
 _MHD_EXTERN int
 MHD_digest_auth_check_digest2 (struct MHD_Connection *connection,
                                const char *realm,
                                const char *username,
                                const uint8_t *digest,
                                size_t digest_size,
                                unsigned int nonce_timeout,
                                enum MHD_DigestAuthAlgorithm algo)
 {
   enum MHD_DigestAuthResult res;
   enum MHD_DigestAuthMultiAlgo3 malgo3;
 
   if (MHD_DIGEST_ALG_AUTO == algo)
   {
     /* MHD_DIGEST_ALG_AUTO maps to more than one base hashing algorithm,
      * but @a digest is a hash of one specific algorithm and its length
      * does not identify which one (SHA-256 and SHA-512/256 hashes are
      * both 32 bytes).  Forwarding AUTO to
      * MHD_digest_auth_check_digest3() would therefore reach the
      * MHD_PANIC() in that function and kill the process.  Report it as
      * a failed authentication instead; the caller cannot recover from
      * an abort, but it can handle MHD_NO. */
 #ifdef HAVE_MESSAGES
     MHD_DLOG (connection->daemon,
               _ ("MHD_DIGEST_ALG_AUTO cannot be used with a " \
                  "pre-calculated digest: exactly one algorithm must be " \
                  "named, as the digest was produced by one.\n"));
 #endif /* HAVE_MESSAGES */
     return MHD_NO;
   }
   else if (MHD_DIGEST_ALG_MD5 == algo)
     malgo3 = MHD_DIGEST_AUTH_MULT_ALGO3_MD5;
   else if (MHD_DIGEST_ALG_SHA256 == algo)
     malgo3 = MHD_DIGEST_AUTH_MULT_ALGO3_SHA256;
   else
     MHD_PANIC (_ ("Wrong 'algo' value, API violation"));
 
   res = MHD_digest_auth_check_digest3 (connection,
                                        realm,
                                        username,
                                        digest,
                                        digest_size,
                                        nonce_timeout,
                                        0, MHD_DIGEST_AUTH_MULT_QOP_AUTH,
                                        malgo3);
   if (MHD_DAUTH_OK == res)
     return MHD_YES;
   else if ((MHD_DAUTH_NONCE_STALE == res) || (MHD_DAUTH_NONCE_WRONG == res) ||
            (MHD_DAUTH_NONCE_OTHER_COND == res) )
     return MHD_INVALID_NONCE;
   return MHD_NO;
 }
 
 
 /**
  * Authenticates the authorization header sent by the client
  * Uses #MHD_DIGEST_ALG_MD5 (required, as @a digest is of fixed
  * size).
  *
  * @param connection The MHD connection structure
  * @param realm The realm presented to the client
  * @param username The username needs to be authenticated
  * @param digest An `unsigned char *' pointer to the binary hash
  *    for the precalculated hash value "username:realm:password";
  *    length must be #MHD_MD5_DIGEST_SIZE bytes
  * @param nonce_timeout The amount of time for a nonce to be
  *      invalid in seconds
  * @return #MHD_YES if authenticated, #MHD_NO if not,
  *         #MHD_INVALID_NONCE if nonce is invalid or stale
  * @note Available since #MHD_VERSION 0x00096000
  * @deprecated use #MHD_digest_auth_check_digest3()
  * @ingroup authentication
  */
 _MHD_EXTERN int
 MHD_digest_auth_check_digest (struct MHD_Connection *connection,
                               const char *realm,
                               const char *username,
                               const uint8_t digest[MHD_MD5_DIGEST_SIZE],
                               unsigned int nonce_timeout)
 {
   return MHD_digest_auth_check_digest2 (connection,
                                         realm,
                                         username,
                                         digest,
                                         MHD_MD5_DIGEST_SIZE,
                                         nonce_timeout,
                                         MHD_DIGEST_ALG_MD5);
 }
 
 
 /**
  * Internal version of #MHD_queue_auth_required_response3() to simplify
  * cleanups.
  *
  * @param connection the MHD connection structure
  * @param realm the realm presented to the client
  * @param opaque the string for opaque value, can be NULL, but NULL is
  *               not recommended for better compatibility with clients;
  *               the recommended format is hex or Base64 encoded string
  * @param domain the optional space-separated list of URIs for which the
  *               same authorisation could be used, URIs can be in form
  *               "path-absolute" (the path for the same host with initial slash)
  *               or in form "absolute-URI" (the full path with protocol), in
  *               any case client may assume that URI is in the same "protection
  *               space" if it starts with any of values specified here;
  *               could be NULL (clients typically assume that the same
  *               credentials could be used for any URI on the same host)
  * @param response the reply to send; should contain the "access denied"
  *                 body; note that this function sets the "WWW Authenticate"
  *                 header and that the caller should not do this;
  *                 the NULL is tolerated
  * @param signal_stale set to #MHD_YES if the nonce is stale to add 'stale=true'
  *                     to the authentication header, this instructs the client
  *                     to retry immediately with the new nonce and the same
  *                     credentials, without asking user for the new password
  * @param mqop the QOP to use
  * @param malgo3 digest algorithm to use, MHD selects; if several algorithms
  *               are allowed then MD5 is preferred (currently, may be changed
  *               in next versions)
  * @param userhash_support if set to non-zero value (#MHD_YES) then support of
  *                         userhash is indicated, the client may provide
  *                         hash("username:realm") instead of username in
  *                         clear text;
  *                         note that clients are allowed to provide the username
  *                         in cleartext even if this parameter set to non-zero;
  *                         when userhash is used, application must be ready to
  *                         identify users by provided userhash value instead of
  *                         username; see #MHD_digest_auth_calc_userhash() and
  *                         #MHD_digest_auth_calc_userhash_hex()
  * @param prefer_utf8 if not set to #MHD_NO, parameter 'charset=UTF-8' is
  *                    added, indicating for the client that UTF-8 encoding
  *                    is preferred
  * @param prefer_utf8 if not set to #MHD_NO, parameter 'charset=UTF-8' is
  *                    added, indicating for the client that UTF-8 encoding
  *                    is preferred
  * @return #MHD_YES on success, #MHD_NO otherwise
  * @note Available since #MHD_VERSION 0x00097701
  * @ingroup authentication
  */
 static enum MHD_Result
 queue_auth_required_response3_inner (struct MHD_Connection *connection,
                                      const char *realm,
                                      const char *opaque,
                                      const char *domain,
                                      struct MHD_Response *response,
                                      int signal_stale,
                                      enum MHD_DigestAuthMultiQOP mqop,
                                      enum MHD_DigestAuthMultiAlgo3 malgo3,
                                      int userhash_support,
                                      int prefer_utf8,
                                      char **buf_ptr,
                                      struct DigestAlgorithm *da)
 {
   static const char prefix_realm[] = "realm=\"";
   static const char prefix_qop[] = "qop=\"";
   static const char prefix_algo[] = "algorithm=";
   static const char prefix_nonce[] = "nonce=\"";
   static const char prefix_opaque[] = "opaque=\"";
   static const char prefix_domain[] = "domain=\"";
   static const char str_charset[] = "charset=UTF-8";
   static const char str_userhash[] = "userhash=true";
   static const char str_stale[] = "stale=true";
   enum MHD_DigestAuthAlgo3 s_algo; /**< Selected algorithm */
   size_t realm_len;
   size_t opaque_len;
   size_t domain_len;
   size_t buf_size;
   char *buf;
   size_t p; /* The position in the buffer */
   char *hdr_name;
 
   if ((0 == (((unsigned int) malgo3) & MHD_DIGEST_AUTH_ALGO3_NON_SESSION)) ||
       (0 != (((unsigned int) malgo3) & MHD_DIGEST_AUTH_ALGO3_SESSION)))
   {
 #ifdef HAVE_MESSAGES
     MHD_DLOG (connection->daemon,
               _ ("Only non-'session' algorithms are supported.\n"));
 #endif /* HAVE_MESSAGES */
     return MHD_NO;
   }
   malgo3 =
     (enum MHD_DigestAuthMultiAlgo3)
     (malgo3
      & (~((enum MHD_DigestAuthMultiAlgo3) MHD_DIGEST_AUTH_ALGO3_NON_SESSION)));
 #ifdef MHD_MD5_SUPPORT
   if (0 != (((unsigned int) malgo3) & MHD_DIGEST_BASE_ALGO_MD5))
     s_algo = MHD_DIGEST_AUTH_ALGO3_MD5;
   else
 #endif /* MHD_MD5_SUPPORT */
 #ifdef MHD_SHA256_SUPPORT
   if (0 != (((unsigned int) malgo3) & MHD_DIGEST_BASE_ALGO_SHA256))
     s_algo = MHD_DIGEST_AUTH_ALGO3_SHA256;
   else
 #endif /* MHD_SHA256_SUPPORT */
 #ifdef MHD_SHA512_256_SUPPORT
   if (0 != (((unsigned int) malgo3) & MHD_DIGEST_BASE_ALGO_SHA512_256))
     s_algo = MHD_DIGEST_AUTH_ALGO3_SHA512_256;
   else
 #endif /* MHD_SHA512_256_SUPPORT */
   {
     if (0 == (((unsigned int) malgo3)
               & (MHD_DIGEST_BASE_ALGO_MD5 | MHD_DIGEST_BASE_ALGO_SHA256
                  | MHD_DIGEST_BASE_ALGO_SHA512_256)))
       MHD_PANIC (_ ("Wrong 'malgo3' value, API violation"));
     else
     {
 #ifdef HAVE_MESSAGES
       MHD_DLOG (connection->daemon,
                 _ ("No requested algorithm is supported by this MHD build.\n"));
 #endif /* HAVE_MESSAGES */
     }
     return MHD_NO;
   }
 
   if (MHD_DIGEST_AUTH_MULT_QOP_AUTH_INT == mqop)
     MHD_PANIC (_ ("Wrong 'mqop' value, API violation"));
 
   mqop = (enum MHD_DigestAuthMultiQOP)
          (mqop
           & (~((enum MHD_DigestAuthMultiQOP) MHD_DIGEST_AUTH_QOP_AUTH_INT)));
 
   if (! digest_init_one_time (da, get_base_digest_algo (s_algo)))
     MHD_PANIC (_ ("Wrong 'algo' value, API violation"));
 
   if (MHD_DIGEST_AUTH_MULT_QOP_NONE == mqop)
   {
 #ifdef HAVE_MESSAGES
     if ((0 != userhash_support) || (0 != prefer_utf8))
       MHD_DLOG (connection->daemon,
                 _ ("The 'userhash' and 'charset' ('prefer_utf8') parameters " \
                    "are not compatible with RFC2069 and ignored.\n"));
     if (0 == (((unsigned int) s_algo) & MHD_DIGEST_BASE_ALGO_MD5))
       MHD_DLOG (connection->daemon,
                 _ ("RFC2069 with SHA-256 or SHA-512/256 algorithm is " \
                    "non-standard extension.\n"));
 #endif
     userhash_support = 0;
     prefer_utf8 = 0;
   }
 
   if (0 == MHD_get_master (connection->daemon)->nonce_nc_size)
   {
 #ifdef HAVE_MESSAGES
     MHD_DLOG (connection->daemon,
               _ ("The nonce array size is zero.\n"));
 #endif /* HAVE_MESSAGES */
     return MHD_NO;
   }
 
   /* Calculate required size */
   buf_size = 0;
   /* 'Digest ' */
   buf_size += MHD_STATICSTR_LEN_ (_MHD_AUTH_DIGEST_BASE) + 1; /* 1 for ' ' */
   buf_size += MHD_STATICSTR_LEN_ (prefix_realm) + 3; /* 3 for '", ' */
   /* 'realm="xxxx", ' */
   realm_len = strlen (realm);
   if (_MHD_AUTH_DIGEST_MAX_PARAM_SIZE < realm_len)
   {
 #ifdef HAVE_MESSAGES
     MHD_DLOG (connection->daemon,
               _ ("The 'realm' is too large.\n"));
 #endif /* HAVE_MESSAGES */
     return MHD_NO;
   }
   if ((NULL != memchr (realm, '\r', realm_len)) ||
       (NULL != memchr (realm, '\n', realm_len)))
     return MHD_NO;
 
   buf_size += realm_len * 2; /* Quoting may double the size */
   /* 'qop="xxxx", ' */
   if (MHD_DIGEST_AUTH_MULT_QOP_NONE != mqop)
   {
     buf_size += MHD_STATICSTR_LEN_ (prefix_qop) + 3; /* 3 for '", ' */
     buf_size += MHD_STATICSTR_LEN_ (MHD_TOKEN_AUTH_);
   }
   /* 'algorithm="xxxx", ' */
   if (((MHD_DIGEST_AUTH_MULT_QOP_NONE) != mqop) ||
       (0 == (((unsigned int) s_algo) & MHD_DIGEST_BASE_ALGO_MD5)))
   {
     buf_size += MHD_STATICSTR_LEN_ (prefix_algo) + 2; /* 2 for ', ' */
 #ifdef MHD_MD5_SUPPORT
     if (MHD_DIGEST_AUTH_ALGO3_MD5 == s_algo)
       buf_size += MHD_STATICSTR_LEN_ (_MHD_MD5_TOKEN);
     else
 #endif /* MHD_MD5_SUPPORT */
 #ifdef MHD_SHA256_SUPPORT
     if (MHD_DIGEST_AUTH_ALGO3_SHA256 == s_algo)
       buf_size += MHD_STATICSTR_LEN_ (_MHD_SHA256_TOKEN);
     else
 #endif /* MHD_SHA256_SUPPORT */
 #ifdef MHD_SHA512_256_SUPPORT
     if (MHD_DIGEST_AUTH_ALGO3_SHA512_256 == s_algo)
       buf_size += MHD_STATICSTR_LEN_ (_MHD_SHA512_256_TOKEN);
     else
 #endif /* MHD_SHA512_256_SUPPORT */
     mhd_assert (0);
   }
   /* 'nonce="xxxx", ' */
   buf_size += MHD_STATICSTR_LEN_ (prefix_nonce) + 3; /* 3 for '", ' */
   buf_size += NONCE_STD_LEN (digest_get_size (da)); /* Escaping not needed */
   /* 'opaque="xxxx", ' */
   if (NULL != opaque)
   {
     buf_size += MHD_STATICSTR_LEN_ (prefix_opaque) + 3; /* 3 for '", ' */
     opaque_len = strlen (opaque);
     if ((NULL != memchr (opaque, '\r', opaque_len)) ||
         (NULL != memchr (opaque, '\n', opaque_len)))
       return MHD_NO;
 
     buf_size += opaque_len * 2; /* Quoting may double the size */
   }
   else
     opaque_len = 0;
   /* 'domain="xxxx", ' */
   if (NULL != domain)
   {
     buf_size += MHD_STATICSTR_LEN_ (prefix_domain) + 3; /* 3 for '", ' */
     domain_len = strlen (domain);
     if ((NULL != memchr (domain, '\r', domain_len)) ||
         (NULL != memchr (domain, '\n', domain_len)))
       return MHD_NO;
 
     buf_size += domain_len * 2; /* Quoting may double the size */
   }
   else
     domain_len = 0;
   /* 'charset=UTF-8' */
   if (MHD_NO != prefer_utf8)
     buf_size += MHD_STATICSTR_LEN_ (str_charset) + 2; /* 2 for ', ' */
   /* 'userhash=true' */
   if (MHD_NO != userhash_support)
     buf_size += MHD_STATICSTR_LEN_ (str_userhash) + 2; /* 2 for ', ' */
   /* 'stale=true' */
   if (MHD_NO != signal_stale)
     buf_size += MHD_STATICSTR_LEN_ (str_stale) + 2; /* 2 for ', ' */
 
   /* The calculated length is for string ended with ", ". One character will
    * be used for zero-termination, the last one will not be used. */
 
   /* Allocate the buffer */
   buf = malloc (buf_size);
   if (NULL == buf)
     return MHD_NO;
   *buf_ptr = buf;
 
   /* Build the challenge string */
   p = 0;
   /* 'Digest: ' */
   memcpy (buf + p, _MHD_AUTH_DIGEST_BASE,
           MHD_STATICSTR_LEN_ (_MHD_AUTH_DIGEST_BASE));
   p += MHD_STATICSTR_LEN_ (_MHD_AUTH_DIGEST_BASE);
   buf[p++] = ' ';
   /* 'realm="xxxx", ' */
   memcpy (buf + p, prefix_realm,
           MHD_STATICSTR_LEN_ (prefix_realm));
   p += MHD_STATICSTR_LEN_ (prefix_realm);
   mhd_assert ((buf_size - p) >= (realm_len * 2));
   if (1)
   {
     size_t quoted_size;
     quoted_size = MHD_str_quote (realm, realm_len, buf + p, buf_size - p);
     if (_MHD_AUTH_DIGEST_MAX_PARAM_SIZE < quoted_size)
     {
 #ifdef HAVE_MESSAGES
       MHD_DLOG (connection->daemon,
                 _ ("The 'realm' is too large after 'quoting'.\n"));
 #endif /* HAVE_MESSAGES */
       return MHD_NO;
     }
     p += quoted_size;
   }
   buf[p++] = '\"';
   buf[p++] = ',';
   buf[p++] = ' ';
   /* 'qop="xxxx", ' */
   if (MHD_DIGEST_AUTH_MULT_QOP_NONE != mqop)
   {
     memcpy (buf + p, prefix_qop,
             MHD_STATICSTR_LEN_ (prefix_qop));
     p += MHD_STATICSTR_LEN_ (prefix_qop);
     memcpy (buf + p, MHD_TOKEN_AUTH_,
             MHD_STATICSTR_LEN_ (MHD_TOKEN_AUTH_));
     p += MHD_STATICSTR_LEN_ (MHD_TOKEN_AUTH_);
     buf[p++] = '\"';
     buf[p++] = ',';
     buf[p++] = ' ';
   }
   /* 'algorithm="xxxx", ' */
   if (((MHD_DIGEST_AUTH_MULT_QOP_NONE) != mqop) ||
       (0 == (((unsigned int) s_algo) & MHD_DIGEST_BASE_ALGO_MD5)))
   {
     memcpy (buf + p, prefix_algo,
             MHD_STATICSTR_LEN_ (prefix_algo));
     p += MHD_STATICSTR_LEN_ (prefix_algo);
 #ifdef MHD_MD5_SUPPORT
     if (MHD_DIGEST_AUTH_ALGO3_MD5 == s_algo)
     {
       memcpy (buf + p, _MHD_MD5_TOKEN,
               MHD_STATICSTR_LEN_ (_MHD_MD5_TOKEN));
       p += MHD_STATICSTR_LEN_ (_MHD_MD5_TOKEN);
     }
     else
 #endif /* MHD_MD5_SUPPORT */
 #ifdef MHD_SHA256_SUPPORT
     if (MHD_DIGEST_AUTH_ALGO3_SHA256 == s_algo)
     {
       memcpy (buf + p, _MHD_SHA256_TOKEN,
               MHD_STATICSTR_LEN_ (_MHD_SHA256_TOKEN));
       p += MHD_STATICSTR_LEN_ (_MHD_SHA256_TOKEN);
     }
     else
 #endif /* MHD_SHA256_SUPPORT */
 #ifdef MHD_SHA512_256_SUPPORT
     if (MHD_DIGEST_AUTH_ALGO3_SHA512_256 == s_algo)
     {
       memcpy (buf + p, _MHD_SHA512_256_TOKEN,
               MHD_STATICSTR_LEN_ (_MHD_SHA512_256_TOKEN));
       p += MHD_STATICSTR_LEN_ (_MHD_SHA512_256_TOKEN);
     }
     else
 #endif /* MHD_SHA512_256_SUPPORT */
     mhd_assert (0);
     buf[p++] = ',';
     buf[p++] = ' ';
   }
   /* 'nonce="xxxx", ' */
   memcpy (buf + p, prefix_nonce,
           MHD_STATICSTR_LEN_ (prefix_nonce));
   p += MHD_STATICSTR_LEN_ (prefix_nonce);
   mhd_assert ((buf_size - p) >= (NONCE_STD_LEN (digest_get_size (da))));
   if (! calculate_add_nonce_with_retry (connection, realm, da, buf + p))
   {
 #ifdef MHD_DIGEST_HAS_EXT_ERROR
     if (digest_ext_error (da))
     {
 #ifdef HAVE_MESSAGES
       MHD_DLOG (connection->daemon,
                 _ ("TLS library reported hash calculation error, nonce could "
                    "not be generated.\n"));
 #endif /* HAVE_MESSAGES */
       return MHD_NO;
     }
 #endif /* MHD_DIGEST_HAS_EXT_ERROR */
 #ifdef HAVE_MESSAGES
     MHD_DLOG (connection->daemon,
               _ ("Could not register nonce. Client's requests with this "
                  "nonce will be always 'stale'. Probably clients' requests "
                  "are too intensive.\n"));
 #endif /* HAVE_MESSAGES */
     (void) 0; /* Mute compiler warning for builds without messages */
   }
   p += NONCE_STD_LEN (digest_get_size (da));
   buf[p++] = '\"';
   buf[p++] = ',';
   buf[p++] = ' ';
   /* 'opaque="xxxx", ' */
   if (NULL != opaque)
   {
     memcpy (buf + p, prefix_opaque,
             MHD_STATICSTR_LEN_ (prefix_opaque));
     p += MHD_STATICSTR_LEN_ (prefix_opaque);
     mhd_assert ((buf_size - p) >= (opaque_len * 2));
     p += MHD_str_quote (opaque, opaque_len, buf + p, buf_size - p);
     buf[p++] = '\"';
     buf[p++] = ',';
     buf[p++] = ' ';
   }
   /* 'domain="xxxx", ' */
   if (NULL != domain)
   {
     memcpy (buf + p, prefix_domain,
             MHD_STATICSTR_LEN_ (prefix_domain));
     p += MHD_STATICSTR_LEN_ (prefix_domain);
     mhd_assert ((buf_size - p) >= (domain_len * 2));
     p += MHD_str_quote (domain, domain_len, buf + p, buf_size - p);
     buf[p++] = '\"';
     buf[p++] = ',';
     buf[p++] = ' ';
   }
   /* 'charset=UTF-8' */
   if (MHD_NO != prefer_utf8)
   {
     memcpy (buf + p, str_charset,
             MHD_STATICSTR_LEN_ (str_charset));
     p += MHD_STATICSTR_LEN_ (str_charset);
     buf[p++] = ',';
     buf[p++] = ' ';
   }
   /* 'userhash=true' */
   if (MHD_NO != userhash_support)
   {
     memcpy (buf + p, str_userhash,
             MHD_STATICSTR_LEN_ (str_userhash));
     p += MHD_STATICSTR_LEN_ (str_userhash);
     buf[p++] = ',';
     buf[p++] = ' ';
   }
   /* 'stale=true' */
   if (MHD_NO != signal_stale)
   {
     memcpy (buf + p, str_stale,
             MHD_STATICSTR_LEN_ (str_stale));
     p += MHD_STATICSTR_LEN_ (str_stale);
     buf[p++] = ',';
     buf[p++] = ' ';
   }
   mhd_assert (buf_size >= p);
   /* The built string ends with ", ". Replace comma with zero-termination. */
   --p;
   buf[--p] = 0;
 
   hdr_name = malloc (MHD_STATICSTR_LEN_ (MHD_HTTP_HEADER_WWW_AUTHENTICATE) + 1);
   if (NULL != hdr_name)
   {
     memcpy (hdr_name, MHD_HTTP_HEADER_WWW_AUTHENTICATE,
             MHD_STATICSTR_LEN_ (MHD_HTTP_HEADER_WWW_AUTHENTICATE) + 1);
     if (MHD_add_response_entry_no_alloc_ (response, MHD_HEADER_KIND,
                                           hdr_name,
                                           MHD_STATICSTR_LEN_ ( \
                                             MHD_HTTP_HEADER_WWW_AUTHENTICATE),
                                           buf, p))
     {
       *buf_ptr = NULL; /* The buffer will be free()ed when the response is destroyed */
       return MHD_queue_response (connection, MHD_HTTP_UNAUTHORIZED, response);
     }
 #ifdef HAVE_MESSAGES
     else
     {
       MHD_DLOG (connection->daemon,
                 _ ("Failed to add Digest auth header.\n"));
     }
 #endif /* HAVE_MESSAGES */
     free (hdr_name);
   }
   return MHD_NO;
 }
 
 
 /**
  * Queues a response to request authentication from the client
  *
  * This function modifies provided @a response. The @a response must not be
  * reused and should be destroyed (by #MHD_destroy_response()) after call of
  * this function.
  *
  * If @a mqop allows both RFC 2069 (MHD_DIGEST_AUTH_QOP_NONE) and QOP with
  * value, then response is formed like if MHD_DIGEST_AUTH_QOP_NONE bit was
  * not set, because such response should be backward-compatible with RFC 2069.
  *
  * If @a mqop allows only MHD_DIGEST_AUTH_MULT_QOP_NONE, then the response is
  * formed in strict accordance with RFC 2069 (no 'qop', no 'userhash', no
  * 'charset'). For better compatibility with clients, it is recommended (but
  * not required) to set @a domain to NULL in this mode.
  *
  * @param connection the MHD connection structure
  * @param realm the realm presented to the client
  * @param opaque the string for opaque value, can be NULL, but NULL is
  *               not recommended for better compatibility with clients;
  *               the recommended format is hex or Base64 encoded string
  * @param domain the optional space-separated list of URIs for which the
  *               same authorisation could be used, URIs can be in form
  *               "path-absolute" (the path for the same host with initial slash)
  *               or in form "absolute-URI" (the full path with protocol), in
  *               any case client may assume that URI is in the same "protection
  *               space" if it starts with any of values specified here;
  *               could be NULL (clients typically assume that the same
  *               credentials could be used for any URI on the same host);
  *               this list provides information for the client only and does
  *               not actually restrict anything on the server side
  * @param response the reply to send; should contain the "access denied"
  *                 body;
  *                 note: this function sets the "WWW Authenticate" header and
  *                 the caller should not set this header;
  *                 the NULL is tolerated
  * @param signal_stale if set to #MHD_YES then indication of stale nonce used in
  *                     the client's request is signalled by adding 'stale=true'
  *                     to the authentication header, this instructs the client
  *                     to retry immediately with the new nonce and the same
  *                     credentials, without asking user for the new password
  * @param mqop the QOP to use
  * @param malgo3 digest algorithm to use; if several algorithms are allowed
  *               then MD5 is preferred (currently, may be changed in next
  *               versions)
  * @param userhash_support if set to non-zero value (#MHD_YES) then support of
  *                         userhash is indicated, allowing client to provide
  *                         hash("username:realm") instead of the username in
  *                         clear text;
  *                         note that clients are allowed to provide the username
  *                         in cleartext even if this parameter set to non-zero;
  *                         when userhash is used, application must be ready to
  *                         identify users by provided userhash value instead of
  *                         username; see #MHD_digest_auth_calc_userhash() and
  *                         #MHD_digest_auth_calc_userhash_hex()
  * @param prefer_utf8 if not set to #MHD_NO, parameter 'charset=UTF-8' is
  *                    added, indicating for the client that UTF-8 encoding for
  *                    the username is preferred
  * @return #MHD_YES on success, #MHD_NO otherwise
  * @note Available since #MHD_VERSION 0x00097701
  * @ingroup authentication
  */
 _MHD_EXTERN enum MHD_Result
 MHD_queue_auth_required_response3 (struct MHD_Connection *connection,
                                    const char *realm,
                                    const char *opaque,
                                    const char *domain,
                                    struct MHD_Response *response,
                                    int signal_stale,
                                    enum MHD_DigestAuthMultiQOP mqop,
                                    enum MHD_DigestAuthMultiAlgo3 malgo3,
                                    int userhash_support,
                                    int prefer_utf8)
 {
   struct DigestAlgorithm da;
   char *buf_ptr;
   enum MHD_Result ret;
 
   buf_ptr = NULL;
   digest_setup_zero (&da);
   ret = queue_auth_required_response3_inner (connection,
                                              realm,
                                              opaque,
                                              domain,
                                              response,
                                              signal_stale,
                                              mqop,
                                              malgo3,
                                              userhash_support,
                                              prefer_utf8,
                                              &buf_ptr,
                                              &da);
   digest_deinit (&da);
   if (NULL != buf_ptr)
     free (buf_ptr);
   return ret;
 }
 
 
 /**
  * Queues a response to request authentication from the client
  *
  * @param connection The MHD connection structure
  * @param realm the realm presented to the client
  * @param opaque string to user for opaque value
  * @param response reply to send; should contain the "access denied"
  *        body; note that this function will set the "WWW Authenticate"
  *        header and that the caller should not do this; the NULL is tolerated
  * @param signal_stale #MHD_YES if the nonce is stale to add
  *        'stale=true' to the authentication header
  * @param algo digest algorithm to use
  * @return #MHD_YES on success, #MHD_NO otherwise
  * @note Available since #MHD_VERSION 0x00096200
  * @ingroup authentication
  */
 _MHD_EXTERN enum MHD_Result
 MHD_queue_auth_fail_response2 (struct MHD_Connection *connection,
                                const char *realm,
                                const char *opaque,
                                struct MHD_Response *response,
                                int signal_stale,
                                enum MHD_DigestAuthAlgorithm algo)
 {
   enum MHD_DigestAuthMultiAlgo3 algo3;
 
   if (MHD_DIGEST_ALG_MD5 == algo)
     algo3 = MHD_DIGEST_AUTH_MULT_ALGO3_MD5;
   else if (MHD_DIGEST_ALG_SHA256 == algo)
     algo3 = MHD_DIGEST_AUTH_MULT_ALGO3_SHA256;
   else if (MHD_DIGEST_ALG_AUTO == algo)
     algo3 = MHD_DIGEST_AUTH_MULT_ALGO3_ANY_NON_SESSION;
   else
     MHD_PANIC (_ ("Wrong algo value.\n")); /* API violation! */
 
   return MHD_queue_auth_required_response3 (connection, realm, opaque,
                                             NULL, response, signal_stale,
                                             MHD_DIGEST_AUTH_MULT_QOP_AUTH,
                                             algo3,
                                             0, 0);
 }
 
 
 /**
  * Queues a response to request authentication from the client.
  * For now uses MD5 (for backwards-compatibility). Still, if you
  * need to be sure, use #MHD_queue_auth_fail_response2().
  *
  * @param connection The MHD connection structure
  * @param realm the realm presented to the client
  * @param opaque string to user for opaque value
  * @param response reply to send; should contain the "access denied"
  *        body; note that this function will set the "WWW Authenticate"
  *        header and that the caller should not do this; the NULL is tolerated
  * @param signal_stale #MHD_YES if the nonce is stale to add
  *        'stale=true' to the authentication header
  * @return #MHD_YES on success, #MHD_NO otherwise
  * @ingroup authentication
  * @deprecated use MHD_queue_auth_fail_response2()
  */
 _MHD_EXTERN enum MHD_Result
 MHD_queue_auth_fail_response (struct MHD_Connection *connection,
                               const char *realm,
                               const char *opaque,
                               struct MHD_Response *response,
                               int signal_stale)
 {
   return MHD_queue_auth_fail_response2 (connection,
                                         realm,
                                         opaque,
                                         response,
                                         signal_stale,
                                         MHD_DIGEST_ALG_MD5);
 }
 
 
 /* end of digestauth.c */