exchange

exchange_api_refund.c (14903B)

---

 /*
   This file is part of TALER
   Copyright (C) 2014-2023 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_refund.c
  * @brief Implementation of the /refund 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_handle.h"
 #include "taler/taler_signatures.h"
 #include "exchange_api_curl_defaults.h"
 
 
 /**
  * @brief A Refund Handle
  */
 struct TALER_EXCHANGE_RefundHandle
 {
 
   /**
    * 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;
 
   /**
    * Handle for the request.
    */
   struct GNUNET_CURL_Job *job;
 
   /**
    * Function to call with the result.
    */
   TALER_EXCHANGE_RefundCallback cb;
 
   /**
    * Closure for @a cb.
    */
   void *cb_cls;
 
   /**
    * Hash over the proposal data to identify the contract
    * which is being refunded.
    */
   struct TALER_PrivateContractHashP h_contract_terms;
 
   /**
    * The coin's public key.  This is the value that must have been
    * signed (blindly) by the Exchange.
    */
   struct TALER_CoinSpendPublicKeyP coin_pub;
 
   /**
    * The Merchant's public key.  Allows the merchant to later refund
    * the transaction or to inquire about the wire transfer identifier.
    */
   struct TALER_MerchantPublicKeyP merchant;
 
   /**
    * Merchant-generated transaction ID for the refund.
    */
   uint64_t rtransaction_id;
 
   /**
    * Amount to be refunded, including refund fee charged by the
    * exchange to the customer.
    */
   struct TALER_Amount refund_amount;
 
 };
 
 
 /**
  * Verify that the signature on the "200 OK" response
  * from the exchange is valid.
  *
  * @param[in,out] rh refund handle (refund fee added)
  * @param json json reply with the signature
  * @param[out] exchange_pub set to the exchange's public key
  * @param[out] exchange_sig set to the exchange's signature
  * @return #GNUNET_OK if the signature is valid, #GNUNET_SYSERR if not
  */
 static enum GNUNET_GenericReturnValue
 verify_refund_signature_ok (struct TALER_EXCHANGE_RefundHandle *rh,
                             const json_t *json,
                             struct TALER_ExchangePublicKeyP *exchange_pub,
                             struct TALER_ExchangeSignatureP *exchange_sig)
 {
   struct GNUNET_JSON_Specification spec[] = {
     GNUNET_JSON_spec_fixed_auto ("exchange_sig",
                                  exchange_sig),
     GNUNET_JSON_spec_fixed_auto ("exchange_pub",
                                  exchange_pub),
     GNUNET_JSON_spec_end ()
   };
 
   if (GNUNET_OK !=
       GNUNET_JSON_parse (json,
                          spec,
                          NULL, NULL))
   {
     GNUNET_break_op (0);
     return GNUNET_SYSERR;
   }
   if (GNUNET_OK !=
       TALER_EXCHANGE_test_signing_key (rh->keys,
                                        exchange_pub))
   {
     GNUNET_break_op (0);
     return GNUNET_SYSERR;
   }
   if (GNUNET_OK !=
       TALER_exchange_online_refund_confirmation_verify (
         &rh->h_contract_terms,
         &rh->coin_pub,
         &rh->merchant,
         rh->rtransaction_id,
         &rh->refund_amount,
         exchange_pub,
         exchange_sig))
   {
     GNUNET_break_op (0);
     return GNUNET_SYSERR;
   }
   return GNUNET_OK;
 }
 
 
 /**
  * Verify that the information on the "412 Dependency Failed" response
  * from the exchange is valid and indeed shows that there is a refund
  * transaction ID reuse going on.
  *
  * @param[in,out] rh refund handle (refund fee added)
  * @param json json reply with the signature
  * @return #GNUNET_OK if the signature is valid, #GNUNET_SYSERR if not
  */
 static enum GNUNET_GenericReturnValue
 verify_failed_dependency_ok (struct TALER_EXCHANGE_RefundHandle *rh,
                              const json_t *json)
 {
   const json_t *h;
   json_t *e;
   struct GNUNET_JSON_Specification spec[] = {
     GNUNET_JSON_spec_array_const ("history",
                                   &h),
     GNUNET_JSON_spec_end ()
   };
 
   if (GNUNET_OK !=
       GNUNET_JSON_parse (json,
                          spec,
                          NULL, NULL))
   {
     GNUNET_break_op (0);
     return GNUNET_SYSERR;
   }
   if (1 != json_array_size (h))
   {
     GNUNET_break_op (0);
     return GNUNET_SYSERR;
   }
   e = json_array_get (h, 0);
   {
     struct TALER_Amount amount;
     const char *type;
     struct TALER_MerchantSignatureP sig;
     struct TALER_Amount refund_fee;
     struct TALER_PrivateContractHashP h_contract_terms;
     uint64_t rtransaction_id;
     struct TALER_MerchantPublicKeyP merchant_pub;
     struct GNUNET_JSON_Specification ispec[] = {
       TALER_JSON_spec_amount_any ("amount",
                                   &amount),
       GNUNET_JSON_spec_string ("type",
                                &type),
       TALER_JSON_spec_amount_any ("refund_fee",
                                   &refund_fee),
       GNUNET_JSON_spec_fixed_auto ("merchant_sig",
                                    &sig),
       GNUNET_JSON_spec_fixed_auto ("h_contract_terms",
                                    &h_contract_terms),
       GNUNET_JSON_spec_fixed_auto ("merchant_pub",
                                    &merchant_pub),
       GNUNET_JSON_spec_uint64 ("rtransaction_id",
                                &rtransaction_id),
       GNUNET_JSON_spec_end ()
     };
 
     if (GNUNET_OK !=
         GNUNET_JSON_parse (e,
                            ispec,
                            NULL, NULL))
     {
       GNUNET_break_op (0);
       return GNUNET_SYSERR;
     }
     if (GNUNET_OK !=
         TALER_merchant_refund_verify (&rh->coin_pub,
                                       &h_contract_terms,
                                       rtransaction_id,
                                       &amount,
                                       &merchant_pub,
                                       &sig))
     {
       GNUNET_break_op (0);
       return GNUNET_SYSERR;
     }
     if ( (rtransaction_id != rh->rtransaction_id) ||
          (0 != GNUNET_memcmp (&rh->h_contract_terms,
                               &h_contract_terms)) ||
          (0 != GNUNET_memcmp (&rh->merchant,
                               &merchant_pub)) ||
          (0 == TALER_amount_cmp (&rh->refund_amount,
                                  &amount)) )
     {
       GNUNET_break_op (0);
       return GNUNET_SYSERR;
     }
   }
   return GNUNET_OK;
 }
 
 
 /**
  * Function called when we're done processing the
  * HTTP /refund request.
  *
  * @param cls the `struct TALER_EXCHANGE_RefundHandle`
  * @param response_code HTTP response code, 0 on error
  * @param response parsed JSON result, NULL on error
  */
 static void
 handle_refund_finished (void *cls,
                         long response_code,
                         const void *response)
 {
   struct TALER_EXCHANGE_RefundHandle *rh = cls;
   const json_t *j = response;
   struct TALER_EXCHANGE_RefundResponse rr = {
     .hr.reply = j,
     .hr.http_status = (unsigned int) response_code
   };
 
   rh->job = NULL;
   switch (response_code)
   {
   case 0:
     rr.hr.ec = TALER_EC_GENERIC_INVALID_RESPONSE;
     break;
   case MHD_HTTP_OK:
     if (GNUNET_OK !=
         verify_refund_signature_ok (rh,
                                     j,
                                     &rr.details.ok.exchange_pub,
                                     &rr.details.ok.exchange_sig))
     {
       GNUNET_break_op (0);
       rr.hr.http_status = 0;
       rr.hr.ec = TALER_EC_EXCHANGE_REFUND_INVALID_SIGNATURE_BY_EXCHANGE;
     }
     break;
   case MHD_HTTP_BAD_REQUEST:
     /* This should never happen, either us or the exchange is buggy
        (or API version conflict); also can happen if the currency
        differs (which we should obviously never support).
        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_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_CONFLICT:
     /* Requested total refunds exceed deposited amount */
     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_FAILED_DEPENDENCY:
     rr.hr.ec = TALER_JSON_get_error_code (j);
     rr.hr.hint = TALER_JSON_get_error_hint (j);
     break;
   case MHD_HTTP_PRECONDITION_FAILED:
     if (GNUNET_OK !=
         verify_failed_dependency_ok (rh,
                                      j))
     {
       GNUNET_break (0);
       rr.hr.http_status = 0;
       rr.hr.ec = TALER_EC_EXCHANGE_REFUND_INVALID_FAILURE_PROOF_BY_EXCHANGE;
       rr.hr.hint = "failed precondition proof returned by exchange is invalid";
       break;
     }
     /* Two different refund requests were made about the same deposit, but
        carrying identical refund transaction ids.  */
     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 */
     GNUNET_break_op (0);
     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 refund\n",
                 (unsigned int) response_code,
                 rr.hr.ec);
     break;
   }
   rh->cb (rh->cb_cls,
           &rr);
   TALER_EXCHANGE_refund_cancel (rh);
 }
 
 
 struct TALER_EXCHANGE_RefundHandle *
 TALER_EXCHANGE_refund (
   struct GNUNET_CURL_Context *ctx,
   const char *url,
   struct TALER_EXCHANGE_Keys *keys,
   const struct TALER_Amount *amount,
   const struct TALER_PrivateContractHashP *h_contract_terms,
   const struct TALER_CoinSpendPublicKeyP *coin_pub,
   uint64_t rtransaction_id,
   const struct TALER_MerchantPrivateKeyP *merchant_priv,
   TALER_EXCHANGE_RefundCallback cb,
   void *cb_cls)
 {
   struct TALER_MerchantPublicKeyP merchant_pub;
   struct TALER_MerchantSignatureP merchant_sig;
   struct TALER_EXCHANGE_RefundHandle *rh;
   json_t *refund_obj;
   CURL *eh;
   char arg_str[sizeof (struct TALER_CoinSpendPublicKeyP) * 2 + 32];
 
   GNUNET_CRYPTO_eddsa_key_get_public (&merchant_priv->eddsa_priv,
                                       &merchant_pub.eddsa_pub);
   TALER_merchant_refund_sign (coin_pub,
                               h_contract_terms,
                               rtransaction_id,
                               amount,
                               merchant_priv,
                               &merchant_sig);
   {
     char pub_str[sizeof (struct TALER_CoinSpendPublicKeyP) * 2];
     char *end;
 
     end = GNUNET_STRINGS_data_to_string (
       coin_pub,
       sizeof (struct TALER_CoinSpendPublicKeyP),
       pub_str,
       sizeof (pub_str));
     *end = '\0';
     GNUNET_snprintf (arg_str,
                      sizeof (arg_str),
                      "coins/%s/refund",
                      pub_str);
   }
   refund_obj = GNUNET_JSON_PACK (
     TALER_JSON_pack_amount ("refund_amount",
                             amount),
     GNUNET_JSON_pack_data_auto ("h_contract_terms",
                                 h_contract_terms),
     GNUNET_JSON_pack_uint64 ("rtransaction_id",
                              rtransaction_id),
     GNUNET_JSON_pack_data_auto ("merchant_pub",
                                 &merchant_pub),
     GNUNET_JSON_pack_data_auto ("merchant_sig",
                                 &merchant_sig));
   rh = GNUNET_new (struct TALER_EXCHANGE_RefundHandle);
   rh->cb = cb;
   rh->cb_cls = cb_cls;
   rh->url = TALER_url_join (url,
                             arg_str,
                             NULL);
   if (NULL == rh->url)
   {
     json_decref (refund_obj);
     GNUNET_free (rh);
     return NULL;
   }
   rh->h_contract_terms = *h_contract_terms;
   rh->coin_pub = *coin_pub;
   rh->merchant = merchant_pub;
   rh->rtransaction_id = rtransaction_id;
   rh->refund_amount = *amount;
   eh = TALER_EXCHANGE_curl_easy_get_ (rh->url);
   if ( (NULL == eh) ||
        (GNUNET_OK !=
         TALER_curl_easy_post (&rh->ctx,
                               eh,
                               refund_obj)) )
   {
     GNUNET_break (0);
     if (NULL != eh)
       curl_easy_cleanup (eh);
     json_decref (refund_obj);
     GNUNET_free (rh->url);
     GNUNET_free (rh);
     return NULL;
   }
   json_decref (refund_obj);
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
               "URL for refund: `%s'\n",
               rh->url);
   rh->keys = TALER_EXCHANGE_keys_incref (keys);
   rh->job = GNUNET_CURL_job_add2 (ctx,
                                   eh,
                                   rh->ctx.headers,
                                   &handle_refund_finished,
                                   rh);
   return rh;
 }
 
 
 void
 TALER_EXCHANGE_refund_cancel (struct TALER_EXCHANGE_RefundHandle *refund)
 {
   if (NULL != refund->job)
   {
     GNUNET_CURL_job_cancel (refund->job);
     refund->job = NULL;
   }
   GNUNET_free (refund->url);
   TALER_curl_easy_post_finished (&refund->ctx);
   TALER_EXCHANGE_keys_decref (refund->keys);
   GNUNET_free (refund);
 }
 
 
 /* end of exchange_api_refund.c */