exchange

exchange_api_recoup.c (11401B)

---

 /*
   This file is part of TALER
   Copyright (C) 2017-2023 Taler Systems SA
 
   TALER is free software; you can redistribute it and/or modify it under the
   terms of the GNU General Public License as published by the Free Software
   Foundation; either version 3, or (at your option) any later version.
 
   TALER 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 General Public License for more details.
 
   You should have received a copy of the GNU General Public License along with
   TALER; see the file COPYING.  If not, see
   <http://www.gnu.org/licenses/>
 */
 /**
  * @file lib/exchange_api_recoup.c
  * @brief Implementation of the /recoup request of the exchange's HTTP API
  * @author Christian Grothoff
  */
 #include "taler/platform.h"
 #include <jansson.h>
 #include <microhttpd.h> /* just for HTTP status codes */
 #include <gnunet/gnunet_util_lib.h>
 #include <gnunet/gnunet_json_lib.h>
 #include <gnunet/gnunet_curl_lib.h>
 #include "taler/taler_json_lib.h"
 #include "taler/taler_exchange_service.h"
 #include "exchange_api_common.h"
 #include "exchange_api_handle.h"
 #include "taler/taler_signatures.h"
 #include "exchange_api_curl_defaults.h"
 
 
 /**
  * @brief A Recoup Handle
  */
 struct TALER_EXCHANGE_RecoupHandle
 {
 
   /**
    * The keys of the exchange this request handle will use
    */
   struct TALER_EXCHANGE_Keys *keys;
 
   /**
    * The url for this request.
    */
   char *url;
 
   /**
    * Context for #TEH_curl_easy_post(). Keeps the data that must
    * persist for Curl to make the upload.
    */
   struct TALER_CURL_PostContext ctx;
 
   /**
    * Denomination key of the coin.
    */
   struct TALER_EXCHANGE_DenomPublicKey pk;
 
   /**
    * Our signature requesting the recoup.
    */
   struct TALER_CoinSpendSignatureP coin_sig;
 
   /**
    * Handle for the request.
    */
   struct GNUNET_CURL_Job *job;
 
   /**
    * Function to call with the result.
    */
   TALER_EXCHANGE_RecoupResultCallback cb;
 
   /**
    * Closure for @a cb.
    */
   void *cb_cls;
 
   /**
    * Public key of the coin we are trying to get paid back.
    */
   struct TALER_CoinSpendPublicKeyP coin_pub;
 
 };
 
 
 /**
  * Parse a recoup response.  If it is valid, call the callback.
  *
  * @param ph recoup handle
  * @param json json reply with the signature
  * @return #GNUNET_OK if the signature is valid and we called the callback;
  *         #GNUNET_SYSERR if not (callback must still be called)
  */
 static enum GNUNET_GenericReturnValue
 process_recoup_response (const struct TALER_EXCHANGE_RecoupHandle *ph,
                          const json_t *json)
 {
   struct TALER_EXCHANGE_RecoupResponse rr = {
     .hr.reply = json,
     .hr.http_status = MHD_HTTP_OK
   };
   struct GNUNET_JSON_Specification spec_withdraw[] = {
     GNUNET_JSON_spec_fixed_auto ("reserve_pub",
                                  &rr.details.ok.reserve_pub),
     GNUNET_JSON_spec_end ()
   };
 
   if (GNUNET_OK !=
       GNUNET_JSON_parse (json,
                          spec_withdraw,
                          NULL, NULL))
   {
     GNUNET_break_op (0);
     return GNUNET_SYSERR;
   }
   ph->cb (ph->cb_cls,
           &rr);
   return GNUNET_OK;
 }
 
 
 /**
  * Function called when we're done processing the
  * HTTP /recoup request.
  *
  * @param cls the `struct TALER_EXCHANGE_RecoupHandle`
  * @param response_code HTTP response code, 0 on error
  * @param response parsed JSON result, NULL on error
  */
 static void
 handle_recoup_finished (void *cls,
                         long response_code,
                         const void *response)
 {
   struct TALER_EXCHANGE_RecoupHandle *ph = cls;
   const json_t *j = response;
   struct TALER_EXCHANGE_RecoupResponse rr = {
     .hr.reply = j,
     .hr.http_status = (unsigned int) response_code
   };
 
   ph->job = NULL;
   switch (response_code)
   {
   case 0:
     rr.hr.ec = TALER_EC_GENERIC_INVALID_RESPONSE;
     break;
   case MHD_HTTP_OK:
     if (GNUNET_OK !=
         process_recoup_response (ph,
                                  j))
     {
       GNUNET_break_op (0);
       rr.hr.ec = TALER_EC_GENERIC_REPLY_MALFORMED;
       rr.hr.http_status = 0;
       break;
     }
     TALER_EXCHANGE_recoup_cancel (ph);
     return;
   case MHD_HTTP_BAD_REQUEST:
     /* This should never happen, either us or the exchange is buggy
        (or API version conflict); just pass JSON reply to the application */
     rr.hr.ec = TALER_JSON_get_error_code (j);
     rr.hr.hint = TALER_JSON_get_error_hint (j);
     break;
   case MHD_HTTP_CONFLICT:
     {
       struct TALER_Amount min_key;
 
       rr.hr.ec = TALER_JSON_get_error_code (j);
       rr.hr.hint = TALER_JSON_get_error_hint (j);
       if (GNUNET_OK !=
           TALER_EXCHANGE_get_min_denomination_ (ph->keys,
                                                 &min_key))
       {
         GNUNET_break (0);
         rr.hr.ec = TALER_EC_GENERIC_REPLY_MALFORMED;
         rr.hr.http_status = 0;
         break;
       }
       break;
     }
   case MHD_HTTP_FORBIDDEN:
     /* Nothing really to verify, exchange says one of the signatures is
        invalid; as we checked them, this should never happen, we
        should pass the JSON reply to the application */
     rr.hr.ec = TALER_JSON_get_error_code (j);
     rr.hr.hint = TALER_JSON_get_error_hint (j);
     break;
   case MHD_HTTP_NOT_FOUND:
     /* Nothing really to verify, this should never
        happen, we should pass the JSON reply to the application */
     rr.hr.ec = TALER_JSON_get_error_code (j);
     rr.hr.hint = TALER_JSON_get_error_hint (j);
     break;
   case MHD_HTTP_GONE:
     /* Kind of normal: the money was already sent to the merchant
        (it was too late for the refund). */
     rr.hr.ec = TALER_JSON_get_error_code (j);
     rr.hr.hint = TALER_JSON_get_error_hint (j);
     break;
   case MHD_HTTP_INTERNAL_SERVER_ERROR:
     /* Server had an internal issue; we should retry, but this API
        leaves this to the application */
     rr.hr.ec = TALER_JSON_get_error_code (j);
     rr.hr.hint = TALER_JSON_get_error_hint (j);
     break;
   default:
     /* unexpected response code */
     rr.hr.ec = TALER_JSON_get_error_code (j);
     rr.hr.hint = TALER_JSON_get_error_hint (j);
     GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                 "Unexpected response code %u/%d for exchange recoup\n",
                 (unsigned int) response_code,
                 (int) rr.hr.ec);
     GNUNET_break (0);
     break;
   }
   ph->cb (ph->cb_cls,
           &rr);
   TALER_EXCHANGE_recoup_cancel (ph);
 }
 
 
 struct TALER_EXCHANGE_RecoupHandle *
 TALER_EXCHANGE_recoup (
   struct GNUNET_CURL_Context *ctx,
   const char *url,
   struct TALER_EXCHANGE_Keys *keys,
   const struct TALER_EXCHANGE_DenomPublicKey *pk,
   const struct TALER_DenominationSignature *denom_sig,
   const struct TALER_ExchangeBlindingValues *blinding_values,
   const struct TALER_PlanchetMasterSecretP *ps,
   const struct TALER_HashBlindedPlanchetsP *h_planchets,
   TALER_EXCHANGE_RecoupResultCallback recoup_cb,
   void *recoup_cb_cls)
 {
   struct TALER_EXCHANGE_RecoupHandle *ph;
   struct TALER_DenominationHashP h_denom_pub;
   json_t *recoup_obj;
   CURL *eh;
   char arg_str[sizeof (struct TALER_CoinSpendPublicKeyP) * 2 + 32];
   struct TALER_CoinSpendPrivateKeyP coin_priv;
   union GNUNET_CRYPTO_BlindingSecretP bks;
 
   ph = GNUNET_new (struct TALER_EXCHANGE_RecoupHandle);
   TALER_planchet_setup_coin_priv (ps,
                                   blinding_values,
                                   &coin_priv);
   TALER_planchet_blinding_secret_create (ps,
                                          blinding_values,
                                          &bks);
   GNUNET_CRYPTO_eddsa_key_get_public (&coin_priv.eddsa_priv,
                                       &ph->coin_pub.eddsa_pub);
   TALER_denom_pub_hash (&pk->key,
                         &h_denom_pub);
   TALER_wallet_recoup_sign (&h_denom_pub,
                             &bks,
                             &coin_priv,
                             &ph->coin_sig);
   recoup_obj = GNUNET_JSON_PACK (
     GNUNET_JSON_pack_data_auto ("denom_pub_hash",
                                 &h_denom_pub),
     TALER_JSON_pack_denom_sig ("denom_sig",
                                denom_sig),
     TALER_JSON_pack_exchange_blinding_values ("ewv",
                                               blinding_values),
     GNUNET_JSON_pack_data_auto ("coin_sig",
                                 &ph->coin_sig),
     GNUNET_JSON_pack_data_auto ("h_planchets",
                                 h_planchets),
     GNUNET_JSON_pack_data_auto ("coin_blind_key_secret",
                                 &bks));
   switch (denom_sig->unblinded_sig->cipher)
   {
   case GNUNET_CRYPTO_BSA_INVALID:
     json_decref (recoup_obj);
     GNUNET_break (0);
     GNUNET_free (ph);
     return NULL;
   case GNUNET_CRYPTO_BSA_RSA:
     break;
   case GNUNET_CRYPTO_BSA_CS:
     {
       union GNUNET_CRYPTO_BlindSessionNonce nonce;
 
       /* NOTE: this is not elegant, and as per the note in TALER_coin_ev_hash()
          it is not strictly clear that the nonce is needed. Best case would be
          to find a way to include it more 'naturally' somehow, for example with
          the variant union version of bks! */
       TALER_cs_withdraw_nonce_derive (ps,
                                       &nonce.cs_nonce);
       GNUNET_assert (
         0 ==
         json_object_set_new (recoup_obj,
                              "nonce",
                              GNUNET_JSON_from_data_auto (
                                &nonce)));
     }
   }
 
   {
     char pub_str[sizeof (struct TALER_CoinSpendPublicKeyP) * 2];
     char *end;
 
     end = GNUNET_STRINGS_data_to_string (
       &ph->coin_pub,
       sizeof (struct TALER_CoinSpendPublicKeyP),
       pub_str,
       sizeof (pub_str));
     *end = '\0';
     GNUNET_snprintf (arg_str,
                      sizeof (arg_str),
                      "coins/%s/recoup",
                      pub_str);
   }
 
   ph->pk = *pk;
   memset (&ph->pk.key,
           0,
           sizeof (ph->pk.key)); /* zero out, as lifetime cannot be warranted */
   ph->cb = recoup_cb;
   ph->cb_cls = recoup_cb_cls;
   ph->url = TALER_url_join (url,
                             arg_str,
                             NULL);
   if (NULL == ph->url)
   {
     json_decref (recoup_obj);
     GNUNET_free (ph);
     return NULL;
   }
   eh = TALER_EXCHANGE_curl_easy_get_ (ph->url);
   if ( (NULL == eh) ||
        (GNUNET_OK !=
         TALER_curl_easy_post (&ph->ctx,
                               eh,
                               recoup_obj)) )
   {
     GNUNET_break (0);
     if (NULL != eh)
       curl_easy_cleanup (eh);
     json_decref (recoup_obj);
     GNUNET_free (ph->url);
     GNUNET_free (ph);
     return NULL;
   }
   json_decref (recoup_obj);
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
               "URL for recoup: `%s'\n",
               ph->url);
   ph->keys = TALER_EXCHANGE_keys_incref (keys);
   ph->job = GNUNET_CURL_job_add2 (ctx,
                                   eh,
                                   ph->ctx.headers,
                                   &handle_recoup_finished,
                                   ph);
   return ph;
 }
 
 
 void
 TALER_EXCHANGE_recoup_cancel (struct TALER_EXCHANGE_RecoupHandle *ph)
 {
   if (NULL != ph->job)
   {
     GNUNET_CURL_job_cancel (ph->job);
     ph->job = NULL;
   }
   GNUNET_free (ph->url);
   TALER_curl_easy_post_finished (&ph->ctx);
   TALER_EXCHANGE_keys_decref (ph->keys);
   GNUNET_free (ph);
 }
 
 
 /* end of exchange_api_recoup.c */