exchange/src/lib/exchange_api_track_transaction.c

/*
  This file is part of TALER
  Copyright (C) 2014-2020 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_track_transaction.c
 * @brief Implementation of the /track/transaction request of the exchange's HTTP API
 * @author Christian Grothoff
 */
#include "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_json_lib.h"
#include "taler_exchange_service.h"
#include "exchange_api_handle.h"
#include "taler_signatures.h"
#include "exchange_api_curl_defaults.h"


/**
 * @brief A Deposit Wtid Handle
 */
struct TALER_EXCHANGE_TrackTransactionHandle
{

  /**
   * The connection to exchange this request handle will use
   */
  struct TALER_EXCHANGE_Handle *exchange;

  /**
   * 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_TrackTransactionCallback cb;

  /**
   * Closure for @a cb.
   */
  void *cb_cls;

  /**
   * Information the exchange should sign in response.
   * (with pre-filled fields from the request).
   */
  struct TALER_ConfirmWirePS depconf;

};


/**
 * Verify that the signature on the "200 OK" response
 * from the exchange is valid.
 *
 * @param dwh deposit wtid handle
 * @param json json reply with the signature
 * @param[out] exchange_pub set to the exchange's public key
 * @return #GNUNET_OK if the signature is valid, #GNUNET_SYSERR if not
 */
static int
verify_deposit_wtid_signature_ok (const struct
                                  TALER_EXCHANGE_TrackTransactionHandle *dwh,
                                  const json_t *json,
                                  struct TALER_ExchangePublicKeyP *exchange_pub)
{
  struct TALER_ExchangeSignatureP exchange_sig;
  const struct TALER_EXCHANGE_Keys *key_state;
  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;
  }
  key_state = TALER_EXCHANGE_get_keys (dwh->exchange);
  if (GNUNET_OK !=
      TALER_EXCHANGE_test_signing_key (key_state,
                                       exchange_pub))
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  if (GNUNET_OK !=
      GNUNET_CRYPTO_eddsa_verify (TALER_SIGNATURE_EXCHANGE_CONFIRM_WIRE,
                                  &dwh->depconf.purpose,
                                  &exchange_sig.eddsa_signature,
                                  &exchange_pub->eddsa_pub))
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  return GNUNET_OK;
}


/**
 * Function called when we're done processing the
 * HTTP /track/transaction request.
 *
 * @param cls the `struct TALER_EXCHANGE_TrackTransactionHandle`
 * @param response_code HTTP response code, 0 on error
 * @param response parsed JSON result, NULL on error
 */
static void
handle_deposit_wtid_finished (void *cls,
                              long response_code,
                              const void *response)
{
  struct TALER_EXCHANGE_TrackTransactionHandle *dwh = cls;
  const struct TALER_WireTransferIdentifierRawP *wtid = NULL;
  struct GNUNET_TIME_Absolute execution_time = GNUNET_TIME_UNIT_FOREVER_ABS;
  const struct TALER_Amount *coin_contribution = NULL;
  struct TALER_Amount coin_contribution_s;
  struct TALER_ExchangePublicKeyP exchange_pub;
  struct TALER_ExchangePublicKeyP *ep = NULL;
  const json_t *j = response;

  dwh->job = NULL;
  switch (response_code)
  {
  case 0:
    break;
  case MHD_HTTP_OK:
    {
      struct GNUNET_JSON_Specification spec[] = {
        GNUNET_JSON_spec_fixed_auto ("wtid", &dwh->depconf.wtid),
        GNUNET_JSON_spec_absolute_time ("execution_time", &execution_time),
        TALER_JSON_spec_amount ("coin_contribution", &coin_contribution_s),
        GNUNET_JSON_spec_end ()
      };

      if (GNUNET_OK !=
          GNUNET_JSON_parse (j,
                             spec,
                             NULL, NULL))
      {
        GNUNET_break_op (0);
        response_code = 0;
        break;
      }
      wtid = &dwh->depconf.wtid;
      dwh->depconf.execution_time = GNUNET_TIME_absolute_hton (execution_time);
      TALER_amount_hton (&dwh->depconf.coin_contribution,
                         &coin_contribution_s);
      coin_contribution = &coin_contribution_s;
      if (GNUNET_OK !=
          verify_deposit_wtid_signature_ok (dwh,
                                            j,
                                            &exchange_pub))
      {
        GNUNET_break_op (0);
        response_code = 0;
      }
      else
      {
        ep = &exchange_pub;
      }
    }
    break;
  case MHD_HTTP_ACCEPTED:
    {
      /* Transaction known, but not executed yet */
      struct GNUNET_JSON_Specification spec[] = {
        GNUNET_JSON_spec_absolute_time ("execution_time", &execution_time),
        GNUNET_JSON_spec_end ()
      };

      if (GNUNET_OK !=
          GNUNET_JSON_parse (j,
                             spec,
                             NULL, NULL))
      {
        GNUNET_break_op (0);
        response_code = 0;
        break;
      }
    }
    break;
  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 */
    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 */
    break;
  case MHD_HTTP_NOT_FOUND:
    /* Exchange does not know about transaction;
       we should pass the reply to the application */
    break;
  case MHD_HTTP_INTERNAL_SERVER_ERROR:
    /* Server had an internal issue; we should retry, but this API
       leaves this to the application */
    break;
  default:
    /* unexpected response code */
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                "Unexpected response code %u\n",
                (unsigned int) response_code);
    GNUNET_break (0);
    response_code = 0;
    break;
  }
  dwh->cb (dwh->cb_cls,
           response_code,
           TALER_JSON_get_error_code (j),
           ep,
           j,
           wtid,
           execution_time,
           coin_contribution);
  TALER_EXCHANGE_track_transaction_cancel (dwh);
}


/**
 * Obtain wire transfer details about an existing deposit operation.
 *
 * @param exchange the exchange to query
 * @param merchant_priv the merchant's private key
 * @param h_wire hash of merchant's wire transfer details
 * @param h_contract_terms hash of the proposal data from the contract
 *                        between merchant and customer
 * @param coin_pub public key of the coin
 * @param cb function to call with the result
 * @param cb_cls closure for @a cb
 * @return handle to abort request
 */
struct TALER_EXCHANGE_TrackTransactionHandle *
TALER_EXCHANGE_track_transaction (struct TALER_EXCHANGE_Handle *exchange,
                                  const struct
                                  TALER_MerchantPrivateKeyP *merchant_priv,
                                  const struct GNUNET_HashCode *h_wire,
                                  const struct
                                  GNUNET_HashCode *h_contract_terms,
                                  const struct
                                  TALER_CoinSpendPublicKeyP *coin_pub,
                                  TALER_EXCHANGE_TrackTransactionCallback cb,
                                  void *cb_cls)
{
  struct TALER_DepositTrackPS dtp;
  struct TALER_MerchantSignatureP merchant_sig;
  struct TALER_EXCHANGE_TrackTransactionHandle *dwh;
  struct GNUNET_CURL_Context *ctx;
  CURL *eh;
  char arg_str[(sizeof (struct TALER_CoinSpendPublicKeyP)
                + sizeof (struct GNUNET_HashCode)
                + sizeof (struct TALER_MerchantPublicKeyP)
                + sizeof (struct GNUNET_HashCode)
                + sizeof (struct TALER_MerchantSignatureP)) * 2 + 48];

  if (GNUNET_YES !=
      TEAH_handle_is_ready (exchange))
  {
    GNUNET_break (0);
    return NULL;
  }
  dtp.purpose.purpose = htonl (TALER_SIGNATURE_MERCHANT_TRACK_TRANSACTION);
  dtp.purpose.size = htonl (sizeof (dtp));
  dtp.h_contract_terms = *h_contract_terms;
  dtp.h_wire = *h_wire;
  GNUNET_CRYPTO_eddsa_key_get_public (&merchant_priv->eddsa_priv,
                                      &dtp.merchant.eddsa_pub);

  dtp.coin_pub = *coin_pub;
  GNUNET_assert (GNUNET_OK ==
                 GNUNET_CRYPTO_eddsa_sign (&merchant_priv->eddsa_priv,
                                           &dtp.purpose,
                                           &merchant_sig.eddsa_sig));
  {
    char cpub_str[sizeof (struct TALER_CoinSpendPublicKeyP) * 2];
    char mpub_str[sizeof (struct TALER_MerchantPublicKeyP) * 2];
    char msig_str[sizeof (struct TALER_MerchantSignatureP) * 2];
    char chash_str[sizeof (struct GNUNET_HashCode) * 2];
    char whash_str[sizeof (struct GNUNET_HashCode) * 2];
    char *end;

    end = GNUNET_STRINGS_data_to_string (h_wire,
                                         sizeof (struct
                                                 GNUNET_HashCode),
                                         whash_str,
                                         sizeof (whash_str));
    *end = '\0';
    end = GNUNET_STRINGS_data_to_string (&dtp.merchant,
                                         sizeof (struct
                                                 TALER_MerchantPublicKeyP),
                                         mpub_str,
                                         sizeof (mpub_str));
    *end = '\0';
    end = GNUNET_STRINGS_data_to_string (h_contract_terms,
                                         sizeof (struct
                                                 GNUNET_HashCode),
                                         chash_str,
                                         sizeof (chash_str));
    *end = '\0';
    end = GNUNET_STRINGS_data_to_string (coin_pub,
                                         sizeof (struct
                                                 TALER_CoinSpendPublicKeyP),
                                         cpub_str,
                                         sizeof (cpub_str));
    *end = '\0';
    end = GNUNET_STRINGS_data_to_string (&merchant_sig,
                                         sizeof (struct
                                                 TALER_MerchantSignatureP),
                                         msig_str,
                                         sizeof (msig_str));
    *end = '\0';

    GNUNET_snprintf (arg_str,
                     sizeof (arg_str),
                     "/deposits/%s/%s/%s/%s?merchant_sig=%s",
                     whash_str,
                     mpub_str,
                     chash_str,
                     cpub_str,
                     msig_str);
  }

  dwh = GNUNET_new (struct TALER_EXCHANGE_TrackTransactionHandle);
  dwh->exchange = exchange;
  dwh->cb = cb;
  dwh->cb_cls = cb_cls;
  dwh->url = TEAH_path_to_url (exchange,
                               arg_str);
  dwh->depconf.purpose.size = htonl (sizeof (struct TALER_ConfirmWirePS));
  dwh->depconf.purpose.purpose = htonl (TALER_SIGNATURE_EXCHANGE_CONFIRM_WIRE);
  dwh->depconf.h_wire = *h_wire;
  dwh->depconf.h_contract_terms = *h_contract_terms;
  dwh->depconf.coin_pub = *coin_pub;

  eh = TEL_curl_easy_get (dwh->url);
  ctx = TEAH_handle_to_context (exchange);
  dwh->job = GNUNET_CURL_job_add (ctx,
                                  eh,
                                  GNUNET_NO,
                                  &handle_deposit_wtid_finished,
                                  dwh);
  return dwh;
}


/**
 * Cancel deposit wtid request.  This function cannot be used on a request
 * handle if a response is already served for it.
 *
 * @param dwh the wire deposits request handle
 */
void
TALER_EXCHANGE_track_transaction_cancel (struct
                                         TALER_EXCHANGE_TrackTransactionHandle *
                                         dwh)
{
  if (NULL != dwh->job)
  {
    GNUNET_CURL_job_cancel (dwh->job);
    dwh->job = NULL;
  }
  GNUNET_free (dwh->url);
  TALER_curl_easy_post_finished (&dwh->ctx);
  GNUNET_free (dwh);
}


/* end of exchange_api_track_transaction.c */