implement /payback-functions in libtalerexchange.so (new C file)

1 files changed, 338 insertions, 0 deletions

diff --git a/src/exchange-lib/exchange_api_payback.c b/src/exchange-lib/exchange_api_payback.c
new file mode 100644
index 000000000..7546605d1
--- /dev/null
+++ b/src/exchange-lib/exchange_api_payback.c
@@ -0,0 +1,338 @@
+/*
+  This file is part of TALER
+  Copyright (C) 2017 GNUnet e.V. and Inria
+
+  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 exchange-lib/exchange_api_payback.c
+ * @brief Implementation of the /payback request of the exchange's HTTP API
+ * @author Christian Grothoff
+ */
+#include "platform.h"
+#include <curl/curl.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"
+
+
+/**
+ * @brief A Payback Handle
+ */
+struct TALER_EXCHANGE_PaybackHandle
+{
+
+  /**
+   * The connection to exchange this request handle will use
+   */
+  struct TALER_EXCHANGE_Handle *exchange;
+
+  /**
+   * The url for this request.
+   */
+  char *url;
+
+  /**
+   * JSON encoding of the request to POST.
+   */
+  char *json_enc;
+
+  /**
+   * Handle for the request.
+   */
+  struct GNUNET_CURL_Job *job;
+
+  /**
+   * Function to call with the result.
+   */
+  TALER_EXCHANGE_PaybackResultCallback 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;
+
+};
+
+
+/**
+ * Verify that the signature on the "200 OK" response
+ * from the exchange is valid. If it is, call the
+ * callback.
+ *
+ * @param ph payback 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 int
+verify_payback_signature_ok (const struct TALER_EXCHANGE_PaybackHandle *ph,
+                             const json_t *json)
+{
+  struct TALER_PaybackConfirmationPS pc;
+  struct TALER_ExchangePublicKeyP exchange_pub;
+  struct TALER_ExchangeSignatureP exchange_sig;
+  struct TALER_Amount amount;
+  struct GNUNET_TIME_Absolute deadline;
+  const char *wire_subject;
+  const struct TALER_EXCHANGE_Keys *key_state;
+  struct GNUNET_JSON_Specification spec[] = {
+    GNUNET_JSON_spec_fixed_auto ("eddsa_sig", &exchange_sig),
+    GNUNET_JSON_spec_fixed_auto ("eddsa_pub", &exchange_pub),
+    TALER_JSON_spec_amount ("amount", &amount),
+    GNUNET_JSON_spec_absolute_time ("payback_deadline", &deadline),
+    GNUNET_JSON_spec_string ("wire_subject", &wire_subject),
+    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 (ph->exchange);
+  if (GNUNET_OK !=
+      TALER_EXCHANGE_test_signing_key (key_state,
+				       &exchange_pub))
+  {
+    GNUNET_break_op (0);
+    return GNUNET_SYSERR;
+  }
+  pc.purpose.purpose = htonl (TALER_SIGNATURE_EXCHANGE_CONFIRM_PAYBACK);
+  pc.purpose.size = htonl (sizeof (pc));
+  pc.payback_deadline = GNUNET_TIME_absolute_hton (deadline);
+  TALER_amount_hton (&pc.payback_amount,
+                     &amount);
+  pc.coin_pub = ph->coin_pub;
+  GNUNET_CRYPTO_hash (wire_subject,
+                      strlen (wire_subject),
+                      &pc.h_wire_subject);
+  if (GNUNET_OK !=
+      GNUNET_CRYPTO_eddsa_verify (TALER_SIGNATURE_EXCHANGE_CONFIRM_PAYBACK,
+                                  &pc.purpose,
+                                  &exchange_sig.eddsa_signature,
+                                  &exchange_pub.eddsa_pub))
+  {
+    GNUNET_break_op (0);
+    return GNUNET_SYSERR;
+  }
+  ph->cb (ph->cb_cls,
+          MHD_HTTP_OK,
+	  TALER_EC_NONE,
+          &amount,
+          deadline,
+          wire_subject,
+          json);
+  return GNUNET_OK;
+}
+
+
+/**
+ * Function called when we're done processing the
+ * HTTP /payback request.
+ *
+ * @param cls the `struct TALER_EXCHANGE_PaybackHandle`
+ * @param response_code HTTP response code, 0 on error
+ * @param json parsed JSON result, NULL on error
+ */
+static void
+handle_payback_finished (void *cls,
+                         long response_code,
+                         const json_t *json)
+{
+  struct TALER_EXCHANGE_PaybackHandle *ph = cls;
+
+  ph->job = NULL;
+  switch (response_code)
+  {
+  case 0:
+    break;
+  case MHD_HTTP_OK:
+    if (GNUNET_OK !=
+        verify_payback_signature_ok (ph,
+                                     json))
+    {
+      GNUNET_break_op (0);
+      response_code = 0;
+    }
+    TALER_EXCHANGE_payback_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 */
+    break;
+  case MHD_HTTP_UNAUTHORIZED:
+    /* 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:
+    /* Nothing really to verify, this should never
+       happen, we should pass the JSON reply to the application */
+    break;
+  case MHD_HTTP_GONE:
+    /* Kind of normal: the money was already sent to the merchant
+       (it was too late for the refund). */
+    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;
+  }
+  ph->cb (ph->cb_cls,
+          response_code,
+	  TALER_JSON_get_error_code (json),
+          NULL,
+          GNUNET_TIME_UNIT_FOREVER_ABS,
+          NULL,
+          json);
+  TALER_EXCHANGE_payback_cancel (ph);
+}
+
+
+/**
+ * Ask the exchange to pay back a coin due to the exchange triggering
+ * the emergency payback protocol for a given denomination.  The value
+ * of the coin will be refunded to the original customer (without fees).
+ *
+ * @param exchange the exchange handle; the exchange must be ready to operate
+ * @param pk kind of coin to pay back
+ * @param denom_sig signature over the coin by the exchange using @a pk
+ * @param coin_priv the coin's private key,
+ * @param blinding_key where to fetch the coin's blinding key
+ * @param payback_cb the callback to call when the final result for this request is available
+ * @param payback_cb_cls closure for @a payback_cb
+ * @return NULL
+ *         if the inputs are invalid (i.e. denomination key not with this exchange).
+ *         In this case, the callback is not called.
+ */
+struct TALER_EXCHANGE_PaybackHandle *
+TALER_EXCHANGE_payback (struct TALER_EXCHANGE_Handle *exchange,
+                        const struct TALER_EXCHANGE_DenomPublicKey *pk,
+                        const struct TALER_DenominationSignature *denom_sig,
+                        const struct TALER_CoinSpendPrivateKeyP *coin_priv,
+                        const struct TALER_DenominationBlindingKeyP *blinding_key,
+                        TALER_EXCHANGE_PaybackResultCallback payback_cb,
+                        void *payback_cb_cls)
+{
+  struct TALER_EXCHANGE_PaybackHandle *ph;
+  struct GNUNET_CURL_Context *ctx;
+  struct TALER_PaybackRequestPS pr;
+  struct TALER_CoinSpendSignatureP coin_sig;
+  json_t *payback_obj;
+  CURL *eh;
+
+  GNUNET_assert (GNUNET_YES ==
+		 MAH_handle_is_ready (exchange));
+  pr.purpose.purpose = htonl (TALER_SIGNATURE_WALLET_COIN_PAYBACK);
+  pr.purpose.size = htonl (sizeof (struct TALER_PaybackRequestPS));
+  GNUNET_CRYPTO_eddsa_key_get_public (&coin_priv->eddsa_priv,
+                                      &pr.coin_pub.eddsa_pub);
+  pr.h_denom_pub = pk->h_key;
+  pr.coin_blind = *blinding_key;
+  GNUNET_assert (GNUNET_OK ==
+                 GNUNET_CRYPTO_eddsa_sign (&coin_priv->eddsa_priv,
+                                           &pr.purpose,
+                                           &coin_sig.eddsa_signature));
+
+  payback_obj = json_pack ("{s:o, s:o," /* denom pub/sig */
+                           " s:o, s:o," /* coin pub/sig */
+                           " s:o}", /* coin_bks */
+                           "denom_pub", GNUNET_JSON_from_rsa_public_key (pk->key.rsa_public_key),
+                           "denom_sig", GNUNET_JSON_from_rsa_signature (denom_sig->rsa_signature),
+                           "coin_pub", GNUNET_JSON_from_data_auto (&pr.coin_pub),
+                           "coin_sig", GNUNET_JSON_from_data_auto (&coin_sig),
+                           "coin_blind_key_secret", GNUNET_JSON_from_data_auto (blinding_key)
+			  );
+  GNUNET_assert (NULL != payback_obj);
+
+  ph = GNUNET_new (struct TALER_EXCHANGE_PaybackHandle);
+  ph->coin_pub = pr.coin_pub;
+  ph->exchange = exchange;
+  ph->cb = payback_cb;
+  ph->cb_cls = payback_cb_cls;
+  ph->url = MAH_path_to_url (exchange, "/payback");
+
+  eh = curl_easy_init ();
+  GNUNET_assert (NULL != (ph->json_enc =
+                          json_dumps (payback_obj,
+                                      JSON_COMPACT)));
+  json_decref (payback_obj);
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "URL for payback: `%s'\n",
+              ph->url);
+  GNUNET_assert (CURLE_OK ==
+                 curl_easy_setopt (eh,
+                                   CURLOPT_URL,
+                                   ph->url));
+  GNUNET_assert (CURLE_OK ==
+                 curl_easy_setopt (eh,
+                                   CURLOPT_POSTFIELDS,
+                                   ph->json_enc));
+  GNUNET_assert (CURLE_OK ==
+                 curl_easy_setopt (eh,
+                                   CURLOPT_POSTFIELDSIZE,
+                                   strlen (ph->json_enc)));
+  ctx = MAH_handle_to_context (exchange);
+  ph->job = GNUNET_CURL_job_add (ctx,
+				 eh,
+				 GNUNET_YES,
+				 &handle_payback_finished,
+				 ph);
+  return ph;
+}
+
+
+/**
+ * Cancel a payback request.  This function cannot be used on a
+ * request handle if the callback was already invoked.
+ *
+ * @param ph the payback handle
+ */
+void
+TALER_EXCHANGE_payback_cancel (struct TALER_EXCHANGE_PaybackHandle *ph)
+{
+  if (NULL != ph->job)
+  {
+    GNUNET_CURL_job_cancel (ph->job);
+    ph->job = NULL;
+  }
+  GNUNET_free (ph->url);
+  GNUNET_free (ph->json_enc);
+  GNUNET_free (ph);
+}
+
+
+/* end of exchange_api_payback.c */