libmicrohttpd

postprocessor.c (38909B)

---

 /*
      This file is part of libmicrohttpd
      Copyright (C) 2007-2021 Daniel Pittman and Christian Grothoff
      Copyright (C) 2014-2022 Karlson2k (Evgeny Grin)
 
      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 postprocessor.c
  * @brief  Methods for parsing POST data
  * @author Christian Grothoff
  * @author Karlson2k (Evgeny Grin)
  */
 
 #include "postprocessor.h"
 #include "internal.h"
 #include "mhd_str.h"
 #include "mhd_compat.h"
 #include "mhd_assert.h"
 
 /**
  * Size of on-stack buffer that we use for un-escaping of the value.
  * We use a pretty small value to be nice to the stack on embedded
  * systems.
  */
 #define XBUF_SIZE 512
 
 
 _MHD_EXTERN struct MHD_PostProcessor *
 MHD_create_post_processor (struct MHD_Connection *connection,
                            size_t buffer_size,
                            MHD_PostDataIterator iter,
                            void *iter_cls)
 {
   struct MHD_PostProcessor *ret;
   const char *encoding;
   const char *boundary;
   size_t blen;
 
   if ( (buffer_size < 256) ||
        (NULL == connection) ||
        (NULL == iter))
     MHD_PANIC (_ ("libmicrohttpd API violation.\n"));
   encoding = NULL;
   if (MHD_NO ==
       MHD_lookup_connection_value_n (connection,
                                      MHD_HEADER_KIND,
                                      MHD_HTTP_HEADER_CONTENT_TYPE,
                                      MHD_STATICSTR_LEN_ (
                                        MHD_HTTP_HEADER_CONTENT_TYPE),
                                      &encoding,
                                      NULL))
     return NULL;
   mhd_assert (NULL != encoding);
   boundary = NULL;
   if (! MHD_str_equal_caseless_n_ (MHD_HTTP_POST_ENCODING_FORM_URLENCODED,
                                    encoding,
                                    MHD_STATICSTR_LEN_ (
                                      MHD_HTTP_POST_ENCODING_FORM_URLENCODED)))
   {
     if (! MHD_str_equal_caseless_n_ (
           MHD_HTTP_POST_ENCODING_MULTIPART_FORMDATA,
           encoding,
           MHD_STATICSTR_LEN_ (
             MHD_HTTP_POST_ENCODING_MULTIPART_FORMDATA)))
     {
       return NULL;
     }
     boundary =
       &encoding[MHD_STATICSTR_LEN_ (MHD_HTTP_POST_ENCODING_MULTIPART_FORMDATA)];
     /* Q: should this be "strcasestr"? */
     boundary = strstr (boundary, "boundary=");
     if (NULL == boundary)
       return NULL; /* failed to determine boundary */
     boundary += MHD_STATICSTR_LEN_ ("boundary=");
     blen = strlen (boundary);
     if ( (blen < 2) ||
          (blen * 2 + 2 > buffer_size) )
       return NULL;              /* (will be) out of memory or invalid boundary */
     if ( (boundary[0] == '"') &&
          (boundary[blen - 1] == '"') )
     {
       /* remove enclosing quotes */
       ++boundary;
       blen -= 2;
     }
   }
   else
     blen = 0;
   buffer_size += 4; /* round up to get nice block sizes despite boundary search */
 
   /* add +1 to ensure we ALWAYS have a zero-termination at the end */
   if (NULL == (ret = MHD_calloc_ (1, sizeof (struct MHD_PostProcessor)
                                   + buffer_size + 1)))
     return NULL;
   ret->connection = connection;
   ret->ikvi = iter;
   ret->cls = iter_cls;
   ret->encoding = encoding;
   ret->buffer_size = buffer_size;
   ret->state = PP_Init;
   ret->blen = blen;
   ret->boundary = boundary;
   ret->skip_rn = RN_Inactive;
   return ret;
 }
 
 
 /**
  * Give a (possibly partial) value to the application callback.  We have some
  * part of the value in the 'pp->xbuf', the rest is between @a value_start and
  * @a value_end.  If @a last_escape is non-NULL, there may be an incomplete
  * escape sequence at at @a value_escape between @a value_start and @a
  * value_end which we should preserve in 'pp->xbuf' for the future.
  *
  * Unescapes the value and calls the iterator together with the key.  The key
  * must already be in the key buffer allocated and 0-terminated at the end of
  * @a pp at the time of the call.
  *
  * @param[in,out] pp post processor to act upon
  * @param value_start where in memory is the value
  * @param value_end where does the value end
  * @param last_escape last '%'-sign in value range,
  *        if relevant, or NULL
  */
 static void
 process_value (struct MHD_PostProcessor *pp,
                const char *value_start,
                const char *value_end,
                const char *last_escape)
 {
   char xbuf[XBUF_SIZE + 1];
   size_t xoff;
 
   mhd_assert (pp->xbuf_pos < sizeof (xbuf));
   /* 'value_start' and 'value_end' must be either both non-NULL or both NULL */
   mhd_assert ( (NULL == value_start) || (NULL != value_end) );
   mhd_assert ( (NULL != value_start) || (NULL == value_end) );
   mhd_assert ( (NULL == last_escape) || (NULL != value_start) );
   /* move remaining input from previous round into processing buffer */
   if (0 != pp->xbuf_pos)
     memcpy (xbuf,
             pp->xbuf,
             pp->xbuf_pos);
   xoff = pp->xbuf_pos;
   pp->xbuf_pos = 0;
   if ( (NULL != last_escape) &&
        (((size_t) (value_end - last_escape)) < sizeof (pp->xbuf)) )
   {
     mhd_assert (value_end >= last_escape);
     pp->xbuf_pos = (size_t) (value_end - last_escape);
     memcpy (pp->xbuf,
             last_escape,
             (size_t) (value_end - last_escape));
     value_end = last_escape;
   }
   while ( (value_start != value_end) ||
           (pp->must_ikvi) ||
           (xoff > 0) )
   {
     size_t delta = (size_t) (value_end - value_start);
     bool cut = false;
     size_t clen = 0;
 
     mhd_assert (value_end >= value_start);
 
     if (delta > XBUF_SIZE - xoff)
       delta = XBUF_SIZE - xoff;
     /* move (additional) input into processing buffer */
     if (0 != delta)
     {
       memcpy (&xbuf[xoff],
               value_start,
               delta);
       xoff += delta;
       value_start += delta;
     }
     /* find if escape sequence is at the end of the processing buffer;
        if so, exclude those from processing (reduce delta to point at
        end of processed region) */
     if ( (xoff > 0) &&
          ('%' == xbuf[xoff - 1]) )
     {
       cut = (xoff != XBUF_SIZE);
       xoff--;
       if (cut)
       {
         /* move escape sequence into buffer for next function invocation */
         pp->xbuf[0] = '%';
         pp->xbuf_pos = 1;
       }
       else
       {
         /* just skip escape sequence for next loop iteration */
         delta = xoff;
         clen = 1;
       }
     }
     else if ( (xoff > 1) &&
               ('%' == xbuf[xoff - 2]) )
     {
       cut = (xoff != XBUF_SIZE);
       xoff -= 2;
       if (cut)
       {
         /* move escape sequence into buffer for next function invocation */
         memcpy (pp->xbuf,
                 &xbuf[xoff],
                 2);
         pp->xbuf_pos = 2;
       }
       else
       {
         /* just skip escape sequence for next loop iteration */
         delta = xoff;
         clen = 2;
       }
     }
     mhd_assert (xoff < sizeof (xbuf));
     /* unescape */
     xbuf[xoff] = '\0';        /* 0-terminate in preparation */
     if (0 != xoff)
     {
       MHD_unescape_plus (xbuf);
       xoff = MHD_http_unescape (xbuf);
     }
     /* finally: call application! */
     if (pp->must_ikvi || (0 != xoff) )
     {
       pp->must_ikvi = false;
       if (MHD_NO == pp->ikvi (pp->cls,
                               MHD_POSTDATA_KIND,
                               (const char *) &pp[1],      /* key */
                               NULL,
                               NULL,
                               NULL,
                               xbuf,
                               pp->value_offset,
                               xoff))
       {
         pp->state = PP_Error;
         return;
       }
     }
     pp->value_offset += xoff;
     if (cut)
       break;
     if (0 != clen)
     {
       xbuf[delta] = '%';        /* undo 0-termination */
       memmove (xbuf,
                &xbuf[delta],
                clen);
     }
     xoff = clen;
   }
 }
 
 
 /**
  * Process url-encoded POST data.
  *
  * @param pp post processor context
  * @param post_data upload data
  * @param post_data_len number of bytes in @a post_data
  * @return #MHD_YES on success, #MHD_NO if there was an error processing the data
  */
 static enum MHD_Result
 post_process_urlencoded (struct MHD_PostProcessor *pp,
                          const char *post_data,
                          size_t post_data_len)
 {
   char *kbuf = (char *) &pp[1];
   size_t poff;
   const char *start_key = NULL;
   const char *end_key = NULL;
   const char *start_value = NULL;
   const char *end_value = NULL;
   const char *last_escape = NULL;
 
   mhd_assert (PP_Callback != pp->state);
 
   poff = 0;
   while ( ( (poff < post_data_len) ||
             (pp->state == PP_Callback) ) &&
           (pp->state != PP_Error) )
   {
     switch (pp->state)
     {
     case PP_Error:
       /* clearly impossible as per while loop invariant */
       abort ();
       break; /* Unreachable */
     case PP_Init:
       /* initial phase */
       mhd_assert (NULL == start_key);
       mhd_assert (NULL == end_key);
       mhd_assert (NULL == start_value);
       mhd_assert (NULL == end_value);
       switch (post_data[poff])
       {
       case '=':
         /* Case: (no key)'=' */
         /* Empty key with value */
         pp->state = PP_Error;
         continue;
       case '&':
         /* Case: (no key)'&' */
         /* Empty key without value */
         poff++;
         continue;
       case '\n':
       case '\r':
         /* Case: (no key)'\n' or (no key)'\r' */
         pp->state = PP_Done;
         poff++;
         break;
       default:
         /* normal character, key start, advance! */
         pp->state = PP_ProcessKey;
         start_key = &post_data[poff];
         pp->must_ikvi = true;
         poff++;
         continue;
       }
       break; /* end PP_Init */
     case PP_ProcessKey:
       /* key phase */
       mhd_assert (NULL == start_value);
       mhd_assert (NULL == end_value);
       mhd_assert (NULL != start_key || 0 == poff);
       mhd_assert (0 != poff || NULL == start_key);
       mhd_assert (NULL == end_key);
       switch (post_data[poff])
       {
       case '=':
         /* Case: 'key=' */
         if (0 != poff)
           end_key = &post_data[poff];
         poff++;
         pp->state = PP_ProcessValue;
         break;
       case '&':
         /* Case: 'key&' */
         if (0 != poff)
           end_key = &post_data[poff];
         poff++;
         pp->state = PP_Callback;
         break;
       case '\n':
       case '\r':
         /* Case: 'key\n' or 'key\r' */
         if (0 != poff)
           end_key = &post_data[poff];
         /* No advance here, 'PP_Done' will be selected by next 'PP_Init' phase */
         pp->state = PP_Callback;
         break;
       default:
         /* normal character, advance! */
         if (0 == poff)
           start_key = post_data;
         poff++;
         break;
       }
       mhd_assert (NULL == end_key || NULL != start_key);
       break; /* end PP_ProcessKey */
     case PP_ProcessValue:
       if (NULL == start_value)
         start_value = &post_data[poff];
       switch (post_data[poff])
       {
       case '=':
         /* case 'key==' */
         pp->state = PP_Error;
         continue;
       case '&':
         /* case 'value&' */
         end_value = &post_data[poff];
         poff++;
         if (pp->must_ikvi ||
             (start_value != end_value) )
         {
           pp->state = PP_Callback;
         }
         else
         {
           pp->buffer_pos = 0;
           pp->value_offset = 0;
           pp->state = PP_Init;
           start_value = NULL;
           end_value = NULL;
         }
         continue;
       case '\n':
       case '\r':
         /* Case: 'value\n' or 'value\r' */
         end_value = &post_data[poff];
         if (pp->must_ikvi ||
             (start_value != end_value) )
           pp->state = PP_Callback; /* No poff advance here to set PP_Done in the next iteration */
         else
         {
           poff++;
           pp->state = PP_Done;
         }
         break;
       case '%':
         last_escape = &post_data[poff];
         poff++;
         break;
       case '0':
       case '1':
       case '2':
       case '3':
       case '4':
       case '5':
       case '6':
       case '7':
       case '8':
       case '9':
         /* character, may be part of escaping */
         poff++;
         continue;
       default:
         /* normal character, no more escaping! */
         last_escape = NULL;
         poff++;
         continue;
       }
       break; /* end PP_ProcessValue */
     case PP_Done:
       switch (post_data[poff])
       {
       case '\n':
       case '\r':
         poff++;
         continue;
       }
       /* unexpected data at the end, fail! */
       pp->state = PP_Error;
       break;
     case PP_Callback:
       mhd_assert ((NULL != end_key) || (NULL == start_key));
       if (1)
       {
         const size_t key_len = (size_t) (end_key - start_key);
         mhd_assert (end_key >= start_key);
         if (0 != key_len)
         {
           if ( (pp->buffer_pos + key_len >= pp->buffer_size) ||
                (pp->buffer_pos + key_len < pp->buffer_pos) )
           {
             /* key too long, cannot parse! */
             pp->state = PP_Error;
             continue;
           }
           /* compute key, if we have not already */
           memcpy (&kbuf[pp->buffer_pos],
                   start_key,
                   key_len);
           pp->buffer_pos += key_len;
           start_key = NULL;
           end_key = NULL;
           pp->must_unescape_key = true;
         }
       }
 #ifdef _DEBUG
       else
         mhd_assert (0 != pp->buffer_pos);
 #endif /* _DEBUG */
       if (pp->must_unescape_key)
       {
         kbuf[pp->buffer_pos] = '\0'; /* 0-terminate key */
         MHD_unescape_plus (kbuf);
         MHD_http_unescape (kbuf);
         pp->must_unescape_key = false;
       }
       process_value (pp,
                      start_value,
                      end_value,
                      NULL);
       if (PP_Error == pp->state)
         continue;
       pp->value_offset = 0;
       start_value = NULL;
       end_value = NULL;
       pp->buffer_pos = 0;
       pp->state = PP_Init;
       break;
     case PP_NextBoundary:
     case PP_ProcessEntryHeaders:
     case PP_PerformCheckMultipart:
     case PP_ProcessValueToBoundary:
     case PP_PerformCleanup:
     case PP_Nested_Init:
     case PP_Nested_PerformMarking:
     case PP_Nested_ProcessEntryHeaders:
     case PP_Nested_ProcessValueToBoundary:
     case PP_Nested_PerformCleanup:
     default:
       MHD_PANIC (_ ("internal error.\n")); /* should never happen! */
     }
     mhd_assert ((end_key == NULL) || (start_key != NULL));
     mhd_assert ((end_value == NULL) || (start_value != NULL));
   }
 
   mhd_assert (PP_Callback != pp->state);
 
   if (PP_Error == pp->state)
   {
     /* State in error, returning failure */
     return MHD_NO;
   }
 
   /* save remaining data for next iteration */
   if (NULL != start_key)
   {
     size_t key_len;
     mhd_assert ((PP_ProcessKey == pp->state) || (NULL != end_key));
     if (NULL == end_key)
       end_key = &post_data[poff];
     mhd_assert (end_key >= start_key);
     key_len = (size_t) (end_key - start_key);
     mhd_assert (0 != key_len); /* it must be always non-zero here */
     if ( (pp->buffer_pos + key_len >= pp->buffer_size) ||
          (pp->buffer_pos + key_len < pp->buffer_pos) )
     {
       pp->state = PP_Error;
       return MHD_NO;
     }
     memcpy (&kbuf[pp->buffer_pos],
             start_key,
             key_len);
     pp->buffer_pos += key_len;
     pp->must_unescape_key = true;
     start_key = NULL;
     end_key = NULL;
   }
   if ( (NULL != start_value) &&
        (PP_ProcessValue == pp->state) )
   {
     /* compute key, if we have not already */
     if (pp->must_unescape_key)
     {
       kbuf[pp->buffer_pos] = '\0'; /* 0-terminate key */
       MHD_unescape_plus (kbuf);
       MHD_http_unescape (kbuf);
       pp->must_unescape_key = false;
     }
     if (NULL == end_value)
       end_value = &post_data[poff];
     if ( (NULL != last_escape) &&
          (2 < (end_value - last_escape)) )
       last_escape = NULL;
     process_value (pp,
                    start_value,
                    end_value,
                    last_escape);
     pp->must_ikvi = false;
   }
   if (PP_Error == pp->state)
   {
     /* State in error, returning failure */
     return MHD_NO;
   }
   return MHD_YES;
 }
 
 
 /**
  * If the given line matches the prefix, strdup the
  * rest of the line into the suffix ptr.
  *
  * @param prefix prefix to match
  * @param prefix_len length of @a prefix
  * @param line line to match prefix in
  * @param suffix set to a copy of the rest of the line, starting at the end of the match
  * @return #MHD_YES if there was a match, #MHD_NO if not
  */
 static int
 try_match_header (const char *prefix,
                   size_t prefix_len,
                   char *line,
                   char **suffix)
 {
   if (NULL != *suffix)
     return MHD_NO;
   if (MHD_str_equal_caseless_n_ (prefix,
                                  line,
                                  prefix_len))
   {
     *suffix = strdup (&line[prefix_len]);
     return MHD_YES;
   }
   return MHD_NO;
 }
 
 
 /**
  *
  * @param pp post processor context
  * @param boundary boundary to look for
  * @param blen number of bytes in boundary
  * @param ioffptr set to the end of the boundary if found,
  *                otherwise incremented by one (FIXME: quirky API!)
  * @param next_state state to which we should advance the post processor
  *                   if the boundary is found
  * @param next_dash_state dash_state to which we should advance the
  *                   post processor if the boundary is found
  * @return #MHD_NO if the boundary is not found, #MHD_YES if we did find it
  */
 static int
 find_boundary (struct MHD_PostProcessor *pp,
                const char *boundary,
                size_t blen,
                size_t *ioffptr,
                enum PP_State next_state,
                enum PP_State next_dash_state)
 {
   char *buf = (char *) &pp[1];
   const char *dash;
 
   if (pp->buffer_pos < 2 + blen)
   {
     if (pp->buffer_pos == pp->buffer_size)
       pp->state = PP_Error;     /* out of memory */
     /* ++(*ioffptr); */
     return MHD_NO;              /* not enough data */
   }
   if ( (0 != memcmp ("--",
                      buf,
                      2)) ||
        (0 != memcmp (&buf[2],
                      boundary,
                      blen)))
   {
     if (pp->state != PP_Init)
     {
       /* garbage not allowed */
       pp->state = PP_Error;
     }
     else
     {
       /* skip over garbage (RFC 2046, 5.1.1) */
       dash = memchr (buf,
                      '-',
                      pp->buffer_pos);
       if (NULL == dash)
         (*ioffptr) += pp->buffer_pos;         /* skip entire buffer */
       else if (dash == buf)
         (*ioffptr)++;                         /* at least skip one byte */
       else
         (*ioffptr) += (size_t) (dash - buf);  /* skip to first possible boundary */
     }
     return MHD_NO;                            /* expected boundary */
   }
   /* remove boundary from buffer */
   (*ioffptr) += 2 + blen;
   /* next: start with headers */
   pp->skip_rn = RN_Dash;
   pp->state = next_state;
   pp->dash_state = next_dash_state;
   return MHD_YES;
 }
 
 
 /**
  * In buf, there maybe an expression '$key="$value"'.  If that is the
  * case, copy a copy of $value to destination.
  *
  * If destination is already non-NULL, do nothing.
  */
 static void
 try_get_value (const char *buf,
                const char *key,
                char **destination)
 {
   const char *spos;
   const char *bpos;
   const char *endv;
   size_t klen;
   size_t vlen;
 
   if (NULL != *destination)
     return;
   bpos = buf;
   klen = strlen (key);
   while (NULL != (spos = strstr (bpos, key)))
   {
     if ( (spos[klen] != '=') ||
          ( (spos != buf) &&
            (spos[-1] != ' ') ) )
     {
       /* no match */
       bpos = spos + 1;
       continue;
     }
     if (spos[klen + 1] != '"')
       return;                   /* not quoted */
     if (NULL == (endv = strchr (&spos[klen + 2],
                                 '\"')))
       return;                   /* no end-quote */
     vlen = (size_t) (endv - spos) - klen - 1;
     *destination = malloc (vlen);
     if (NULL == *destination)
       return;                   /* out of memory */
     (*destination)[vlen - 1] = '\0';
     memcpy (*destination,
             &spos[klen + 2],
             vlen - 1);
     return;                     /* success */
   }
 }
 
 
 /**
  * Go over the headers of the part and update
  * the fields in "pp" according to what we find.
  * If we are at the end of the headers (as indicated
  * by an empty line), transition into next_state.
  *
  * @param pp post processor context
  * @param ioffptr set to how many bytes have been
  *                processed
  * @param next_state state to which the post processor should
  *                be advanced if we find the end of the headers
  * @return #MHD_YES if we can continue processing,
  *         #MHD_NO on error or if we do not have
  *                enough data yet
  */
 static int
 process_multipart_headers (struct MHD_PostProcessor *pp,
                            size_t *ioffptr,
                            enum PP_State next_state)
 {
   char *buf = (char *) &pp[1];
   size_t newline;
 
   newline = 0;
   while ( (newline < pp->buffer_pos) &&
           (buf[newline] != '\r') &&
           (buf[newline] != '\n') )
     newline++;
   if (newline == pp->buffer_size)
   {
     pp->state = PP_Error;
     return MHD_NO;              /* out of memory */
   }
   if (newline == pp->buffer_pos)
     return MHD_NO;              /* will need more data */
   if (0 == newline)
   {
     /* empty line - end of headers */
     pp->skip_rn = RN_Full;
     pp->state = next_state;
     return MHD_YES;
   }
   /* got an actual header */
   if (buf[newline] == '\r')
     pp->skip_rn = RN_OptN;
   buf[newline] = '\0';
   if (MHD_str_equal_caseless_n_ ("Content-disposition: ",
                                  buf,
                                  MHD_STATICSTR_LEN_ ("Content-disposition: ")))
   {
     try_get_value (&buf[MHD_STATICSTR_LEN_ ("Content-disposition: ")],
                    "name",
                    &pp->content_name);
     try_get_value (&buf[MHD_STATICSTR_LEN_ ("Content-disposition: ")],
                    "filename",
                    &pp->content_filename);
   }
   else
   {
     try_match_header ("Content-type: ",
                       MHD_STATICSTR_LEN_ ("Content-type: "),
                       buf,
                       &pp->content_type);
     try_match_header ("Content-Transfer-Encoding: ",
                       MHD_STATICSTR_LEN_ ("Content-Transfer-Encoding: "),
                       buf,
                       &pp->content_transfer_encoding);
   }
   (*ioffptr) += newline + 1;
   return MHD_YES;
 }
 
 
 /**
  * We have the value until we hit the given boundary;
  * process accordingly.
  *
  * @param pp post processor context
  * @param ioffptr incremented based on the number of bytes processed
  * @param boundary the boundary to look for
  * @param blen strlen(boundary)
  * @param next_state what state to go into after the
  *        boundary was found
  * @param next_dash_state state to go into if the next
  *        boundary ends with "--"
  * @return #MHD_YES if we can continue processing,
  *         #MHD_NO on error or if we do not have
  *                enough data yet
  */
 static int
 process_value_to_boundary (struct MHD_PostProcessor *pp,
                            size_t *ioffptr,
                            const char *boundary,
                            size_t blen,
                            enum PP_State next_state,
                            enum PP_State next_dash_state)
 {
   char *buf = (char *) &pp[1];
   size_t newline;
   const char *r;
 
   /* all data in buf until the boundary
      (\r\n--+boundary) is part of the value */
   newline = 0;
   while (1)
   {
     while (newline + 4 < pp->buffer_pos)
     {
       r = memchr (&buf[newline],
                   '\r',
                   pp->buffer_pos - newline - 4);
       if (NULL == r)
       {
         newline = pp->buffer_pos - 4;
         break;
       }
       newline = (size_t) (r - buf);
       if (0 == memcmp ("\r\n--",
                        &buf[newline],
                        4))
         break;
       newline++;
     }
     if (newline + blen + 4 <= pp->buffer_pos)
     {
       /* can check boundary */
       if (0 != memcmp (&buf[newline + 4],
                        boundary,
                        blen))
       {
         /* no boundary, "\r\n--" is part of content, skip */
         newline += 4;
         continue;
       }
       else
       {
         /* boundary found, process until newline then
            skip boundary and go back to init */
         pp->skip_rn = RN_Dash;
         pp->state = next_state;
         pp->dash_state = next_dash_state;
         (*ioffptr) += blen + 4;             /* skip boundary as well */
         buf[newline] = '\0';
         break;
       }
     }
     else
     {
       /* cannot check for boundary, process content that
          we have and check again later; except, if we have
          no content, abort (out of memory) */
       if ( (0 == newline) &&
            (pp->buffer_pos == pp->buffer_size) )
       {
         pp->state = PP_Error;
         return MHD_NO;
       }
       break;
     }
   }
   /* newline is either at beginning of boundary or
      at least at the last character that we are sure
      is not part of the boundary */
   if ( ( (pp->must_ikvi) ||
          (0 != newline) ) &&
        (MHD_NO == pp->ikvi (pp->cls,
                             MHD_POSTDATA_KIND,
                             pp->content_name,
                             pp->content_filename,
                             pp->content_type,
                             pp->content_transfer_encoding,
                             buf,
                             pp->value_offset,
                             newline)) )
   {
     pp->state = PP_Error;
     return MHD_NO;
   }
   pp->must_ikvi = false;
   pp->value_offset += newline;
   (*ioffptr) += newline;
   return MHD_YES;
 }
 
 
 /**
  *
  * @param pp post processor context
  */
 static void
 free_unmarked (struct MHD_PostProcessor *pp)
 {
   if ( (NULL != pp->content_name) &&
        (0 == (pp->have & NE_content_name)) )
   {
     free (pp->content_name);
     pp->content_name = NULL;
   }
   if ( (NULL != pp->content_type) &&
        (0 == (pp->have & NE_content_type)) )
   {
     free (pp->content_type);
     pp->content_type = NULL;
   }
   if ( (NULL != pp->content_filename) &&
        (0 == (pp->have & NE_content_filename)) )
   {
     free (pp->content_filename);
     pp->content_filename = NULL;
   }
   if ( (NULL != pp->content_transfer_encoding) &&
        (0 == (pp->have & NE_content_transfer_encoding)) )
   {
     free (pp->content_transfer_encoding);
     pp->content_transfer_encoding = NULL;
   }
 }
 
 
 /**
  * Decode multipart POST data.
  *
  * @param pp post processor context
  * @param post_data data to decode
  * @param post_data_len number of bytes in @a post_data
  * @return #MHD_NO on error,
  */
 static enum MHD_Result
 post_process_multipart (struct MHD_PostProcessor *pp,
                         const char *post_data,
                         size_t post_data_len)
 {
   char *buf;
   size_t max;
   size_t ioff;
   size_t poff;
   int state_changed;
 
   buf = (char *) &pp[1];
   ioff = 0;
   poff = 0;
   state_changed = 1;
   while ( (poff < post_data_len) ||
           ( (pp->buffer_pos > 0) &&
             (0 != state_changed) ) )
   {
     /* first, move as much input data
        as possible to our internal buffer */
     max = pp->buffer_size - pp->buffer_pos;
     if (max > post_data_len - poff)
       max = post_data_len - poff;
     memcpy (&buf[pp->buffer_pos],
             &post_data[poff],
             max);
     poff += max;
     pp->buffer_pos += max;
     if ( (0 == max) &&
          (0 == state_changed) &&
          (poff < post_data_len) )
     {
       pp->state = PP_Error;
       return MHD_NO;            /* out of memory */
     }
     state_changed = 0;
 
     /* first state machine for '\r'-'\n' and '--' handling */
     switch (pp->skip_rn)
     {
     case RN_Inactive:
       break;
     case RN_OptN:
       if (buf[0] == '\n')
       {
         ioff++;
         pp->skip_rn = RN_Inactive;
         goto AGAIN;
       }
     /* fall-through! */
     case RN_Dash:
       if (buf[0] == '-')
       {
         ioff++;
         pp->skip_rn = RN_Dash2;
         goto AGAIN;
       }
       pp->skip_rn = RN_Full;
     /* fall-through! */
     case RN_Full:
       if (buf[0] == '\r')
       {
         if ( (pp->buffer_pos > 1) &&
              ('\n' == buf[1]) )
         {
           pp->skip_rn = RN_Inactive;
           ioff += 2;
         }
         else
         {
           pp->skip_rn = RN_OptN;
           ioff++;
         }
         goto AGAIN;
       }
       if (buf[0] == '\n')
       {
         ioff++;
         pp->skip_rn = RN_Inactive;
         goto AGAIN;
       }
       pp->skip_rn = RN_Inactive;
       pp->state = PP_Error;
       return MHD_NO;            /* no '\r\n' */
     case RN_Dash2:
       if (buf[0] == '-')
       {
         ioff++;
         pp->skip_rn = RN_Full;
         pp->state = pp->dash_state;
         goto AGAIN;
       }
       pp->state = PP_Error;
       break;
     }
 
     /* main state engine */
     switch (pp->state)
     {
     case PP_Error:
       return MHD_NO;
     case PP_Done:
       /* did not expect to receive more data */
       pp->state = PP_Error;
       return MHD_NO;
     case PP_Init:
       /**
        * Per RFC2046 5.1.1 NOTE TO IMPLEMENTORS, consume anything
        * prior to the first multipart boundary:
        *
        * > There appears to be room for additional information prior
        * > to the first boundary delimiter line and following the
        * > final boundary delimiter line.  These areas should
        * > generally be left blank, and implementations must ignore
        * > anything that appears before the first boundary delimiter
        * > line or after the last one.
        */
       (void) find_boundary (pp,
                             pp->boundary,
                             pp->blen,
                             &ioff,
                             PP_ProcessEntryHeaders,
                             PP_Done);
       break;
     case PP_NextBoundary:
       if (MHD_NO == find_boundary (pp,
                                    pp->boundary,
                                    pp->blen,
                                    &ioff,
                                    PP_ProcessEntryHeaders,
                                    PP_Done))
       {
         if (pp->state == PP_Error)
           return MHD_NO;
         goto END;
       }
       break;
     case PP_ProcessEntryHeaders:
       pp->must_ikvi = true;
       if (MHD_NO ==
           process_multipart_headers (pp,
                                      &ioff,
                                      PP_PerformCheckMultipart))
       {
         if (pp->state == PP_Error)
           return MHD_NO;
         else
           goto END;
       }
       state_changed = 1;
       break;
     case PP_PerformCheckMultipart:
       if ( (NULL != pp->content_type) &&
            (MHD_str_equal_caseless_n_ (pp->content_type,
                                        "multipart/mixed",
                                        MHD_STATICSTR_LEN_ ("multipart/mixed"))))
       {
         const char *bnd;
         char *nested;
 
         bnd = strstr (pp->content_type,
                       "boundary=");
         if (NULL == bnd)
         {
           pp->state = PP_Error;
           return MHD_NO;
         }
         /* Note: 'bnd' points into 'pp->content_type', which is released
            below, so the copy must be taken first.  It must also be
            taken into a local: assigning the 'strstr()' result to
            'pp->nested_boundary' first would overwrite -- and leak -- a
            boundary already owned by this post processor.  That happens
            whenever this state is reached twice without passing through
            PP_PerformCleanup, i.e. for every additional nested
            "multipart/mixed" part, and the leaked block is as long as
            the boundary the client chose. */
         nested = strdup (&bnd[MHD_STATICSTR_LEN_ ("boundary=")]);
         if (NULL == nested)
         {
           /* out of memory */
           pp->state = PP_Error;
           return MHD_NO;
         }
         if (NULL != pp->nested_boundary)
           free (pp->nested_boundary);
         pp->nested_boundary = nested;
         /* free old content type, we will need that field
            for the content type of the nested elements */
         free (pp->content_type);
         pp->content_type = NULL;
         pp->nlen = strlen (pp->nested_boundary);
         pp->state = PP_Nested_Init;
         state_changed = 1;
         break;
       }
       pp->state = PP_ProcessValueToBoundary;
       pp->value_offset = 0;
       state_changed = 1;
       break;
     case PP_ProcessValueToBoundary:
       if (MHD_NO == process_value_to_boundary (pp,
                                                &ioff,
                                                pp->boundary,
                                                pp->blen,
                                                PP_PerformCleanup,
                                                PP_Done))
       {
         if (pp->state == PP_Error)
           return MHD_NO;
         break;
       }
       break;
     case PP_PerformCleanup:
       /* clean up state of one multipart form-data element! */
       pp->have = NE_none;
       free_unmarked (pp);
       if (NULL != pp->nested_boundary)
       {
         free (pp->nested_boundary);
         pp->nested_boundary = NULL;
       }
       pp->state = PP_ProcessEntryHeaders;
       state_changed = 1;
       break;
     case PP_Nested_Init:
       if (NULL == pp->nested_boundary)
       {
         pp->state = PP_Error;
         return MHD_NO;
       }
       if (MHD_NO == find_boundary (pp,
                                    pp->nested_boundary,
                                    pp->nlen,
                                    &ioff,
                                    PP_Nested_PerformMarking,
                                    PP_NextBoundary /* or PP_Error? */))
       {
         if (pp->state == PP_Error)
           return MHD_NO;
         goto END;
       }
       break;
     case PP_Nested_PerformMarking:
       /* remember what headers were given
          globally */
       pp->have = NE_none;
       if (NULL != pp->content_name)
         pp->have |= NE_content_name;
       if (NULL != pp->content_type)
         pp->have |= NE_content_type;
       if (NULL != pp->content_filename)
         pp->have |= NE_content_filename;
       if (NULL != pp->content_transfer_encoding)
         pp->have |= NE_content_transfer_encoding;
       pp->state = PP_Nested_ProcessEntryHeaders;
       state_changed = 1;
       break;
     case PP_Nested_ProcessEntryHeaders:
       pp->value_offset = 0;
       if (MHD_NO ==
           process_multipart_headers (pp,
                                      &ioff,
                                      PP_Nested_ProcessValueToBoundary))
       {
         if (pp->state == PP_Error)
           return MHD_NO;
         else
           goto END;
       }
       state_changed = 1;
       break;
     case PP_Nested_ProcessValueToBoundary:
       if (MHD_NO == process_value_to_boundary (pp,
                                                &ioff,
                                                pp->nested_boundary,
                                                pp->nlen,
                                                PP_Nested_PerformCleanup,
                                                PP_NextBoundary))
       {
         if (pp->state == PP_Error)
           return MHD_NO;
         break;
       }
       break;
     case PP_Nested_PerformCleanup:
       free_unmarked (pp);
       pp->state = PP_Nested_ProcessEntryHeaders;
       state_changed = 1;
       break;
     case PP_ProcessKey:
     case PP_ProcessValue:
     case PP_Callback:
     default:
       MHD_PANIC (_ ("internal error.\n")); /* should never happen! */
     }
 AGAIN:
     if (ioff > 0)
     {
       memmove (buf,
                &buf[ioff],
                pp->buffer_pos - ioff);
       pp->buffer_pos -= ioff;
       ioff = 0;
       state_changed = 1;
     }
   }
 END:
   if (0 != ioff)
   {
     memmove (buf,
              &buf[ioff],
              pp->buffer_pos - ioff);
     pp->buffer_pos -= ioff;
   }
   if (poff < post_data_len)
   {
     pp->state = PP_Error;
     return MHD_NO;              /* serious error */
   }
   return MHD_YES;
 }
 
 
 _MHD_EXTERN enum MHD_Result
 MHD_post_process (struct MHD_PostProcessor *pp,
                   const char *post_data,
                   size_t post_data_len)
 {
   if (0 == post_data_len)
     return MHD_YES;
   if (NULL == pp)
     return MHD_NO;
   if (MHD_str_equal_caseless_n_ (MHD_HTTP_POST_ENCODING_FORM_URLENCODED,
                                  pp->encoding,
                                  MHD_STATICSTR_LEN_ (
                                    MHD_HTTP_POST_ENCODING_FORM_URLENCODED)))
     return post_process_urlencoded (pp,
                                     post_data,
                                     post_data_len);
   if (MHD_str_equal_caseless_n_ (MHD_HTTP_POST_ENCODING_MULTIPART_FORMDATA,
                                  pp->encoding,
                                  MHD_STATICSTR_LEN_ (
                                    MHD_HTTP_POST_ENCODING_MULTIPART_FORMDATA)))
     return post_process_multipart (pp,
                                    post_data,
                                    post_data_len);
   /* this should never be reached */
   return MHD_NO;
 }
 
 
 _MHD_EXTERN enum MHD_Result
 MHD_destroy_post_processor (struct MHD_PostProcessor *pp)
 {
   enum MHD_Result ret;
 
   if (NULL == pp)
     return MHD_YES;
   if (PP_ProcessValue == pp->state)
   {
     /* key without terminated value left at the end of the
        buffer; fake receiving a termination character to
        ensure it is also processed */
     post_process_urlencoded (pp,
                              "\n",
                              1);
   }
   /* These internal strings need cleaning up since
      the post-processing may have been interrupted
      at any stage */
   if ( (pp->xbuf_pos > 0) ||
        ( (pp->state != PP_Done) &&
          (pp->state != PP_Init) ) )
     ret = MHD_NO;
   else
     ret = MHD_YES;
   pp->have = NE_none;
   free_unmarked (pp);
   if (NULL != pp->nested_boundary)
     free (pp->nested_boundary);
   free (pp);
   return ret;
 }
 
 
 /* end of postprocessor.c */