-draft for merge endpoint

1 files changed, 455 insertions, 0 deletions

diff --git a/src/exchange/taler-exchange-httpd_purses_merge.c b/src/exchange/taler-exchange-httpd_purses_merge.c
new file mode 100644
index 000000000..07038cb6a
--- /dev/null
+++ b/src/exchange/taler-exchange-httpd_purses_merge.c
@@ -0,0 +1,455 @@
+/*
+  This file is part of TALER
+  Copyright (C) 2022 Taler Systems SA
+
+  TALER is free software; you can redistribute it and/or modify it under the
+  terms of the GNU Affero 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 Affero General Public License for more details.
+
+  You should have received a copy of the GNU Affero General Public License along with
+  TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+*/
+/**
+ * @file taler-exchange-httpd_purses_merge.c
+ * @brief Handle /purses/$PID/merge requests; parses the POST and JSON and
+ *        verifies the reserve signature before handing things off
+ *        to the database.
+ * @author Christian Grothoff
+ */
+#include "platform.h"
+#include <gnunet/gnunet_util_lib.h>
+#include <gnunet/gnunet_json_lib.h>
+#include <jansson.h>
+#include <microhttpd.h>
+#include <pthread.h>
+#include "taler_json_lib.h"
+#include "taler_mhd_lib.h"
+#include "taler-exchange-httpd_purses_merge.h"
+#include "taler-exchange-httpd_responses.h"
+#include "taler_exchangedb_lib.h"
+#include "taler-exchange-httpd_keys.h"
+
+
+/**
+ * Closure for #merge_transaction.
+ */
+struct PurseMergeContext
+{
+  /**
+   * Public key of the purse we are creating.
+   */
+  const struct TALER_PurseContractPublicKeyP *purse_pub;
+
+  /**
+   * Total amount to be put into the purse.
+   */
+  struct TALER_Amount target_amount;
+
+  /**
+   * Current amount in the purse.
+   */
+  struct TALER_Amount balance;
+
+  /**
+   * When should the purse expire.
+   */
+  struct GNUNET_TIME_Timestamp purse_expiration;
+
+  /**
+   * Our current time.
+   */
+  struct GNUNET_TIME_Timestamp exchange_timestamp;
+
+  /**
+   * Merge key for the purse.
+   */
+  struct TALER_PurseMergePublicKeyP merge_pub;
+
+  /**
+   * Signature of the reservce affiming this request.
+   */
+  struct TALER_ReserveSignatureP reserve_sig;
+
+  /**
+   * Signature of the client affiming the merge.
+   */
+  struct TALER_PurseMergeSignatureP merge_sig;
+
+  /**
+   * Public key of the reserve, as extracted from @e payto_uri.
+   */
+  struct TALER_ReservePublicKeyP reserve_pub;
+
+  /**
+   * Hash of the contract terms of the purse.
+   */
+  struct TALER_PrivateContractHashP h_contract_terms;
+
+  /**
+   * Fees that apply to this operation.
+   */
+  const struct TEH_GlobalFee *gf;
+
+  /**
+   * URI of the account the purse is to be merged into.
+   * Must be of the form 'payto://taler/$EXCHANGE_URL/RESERVE_PUB'.
+   */
+  const char *payto_uri;
+
+  /**
+   * Base URL of the exchange provider.
+   */
+  char *provider_url;
+
+  /**
+   * Minimum age for deposits into this purse.
+   */
+  uint32_t min_age;
+};
+
+
+/**
+ * Send confirmation of purse creation success to client.
+ *
+ * @param connection connection to the client
+ * @param pcc details about the request that succeeded
+ * @return MHD result code
+ */
+static MHD_RESULT
+reply_merge_success (struct MHD_Connection *connection,
+                     const struct PurseMergeContext *pcc)
+{
+  struct TALER_ExchangePublicKeyP pub;
+  struct TALER_ExchangeSignatureP sig;
+  enum TALER_ErrorCode ec;
+  struct TALER_Amount merge_amount;
+
+  if (0 <=
+      TALER_amount_cmp (&pcc->balance,
+                        &pcc->target_amount))
+  {
+    return TALER_MHD_REPLY_JSON_PACK (
+      connection,
+      MHD_HTTP_ACCEPTED,
+      TALER_JSON_pack_amount ("balance",
+                              &pcc->balance));
+  }
+  // FIXME: check return value...
+  TALER_amount_subtract (&merge_amount,
+                         &pcc->target_amount,
+                         &gf->fees.merge);
+  if (TALER_EC_NONE !=
+      (ec = TALER_exchange_online_purse_merged_sign (
+         &TEH_keys_exchange_sign_,
+         pcc->exchange_timestamp,
+         pcc->purse_expiration,
+         &merge_amount,
+         pcc->purse_pub,
+         &pcc->merge_pub,
+         &pcc->h_contract_terms,
+         &pub,
+         &sig)))
+  {
+    GNUNET_break (0);
+    return TALER_MHD_reply_with_ec (connection,
+                                    ec,
+                                    NULL);
+  }
+  return TALER_MHD_REPLY_JSON_PACK (
+    connection,
+    MHD_HTTP_OK,
+    TALER_JSON_pack_amount ("merge_amount",
+                            &merge_amount),
+    GNUNET_JSON_pack_timestamp ("exchange_timestamp",
+                                pcc->exchange_timestamp),
+    GNUNET_JSON_pack_data_auto ("exchange_sig",
+                                &sig),
+    GNUNET_JSON_pack_data_auto ("exchange_pub",
+                                &pub));
+}
+
+
+/**
+ * Execute database transaction for /purses/$PID/merge.  Runs the transaction
+ * logic; IF it returns a non-error code, the transaction logic MUST NOT queue
+ * a MHD response.  IF it returns an hard error, the transaction logic MUST
+ * queue a MHD response and set @a mhd_ret.  IF it returns the soft error
+ * code, the function MAY be called again to retry and MUST not queue a MHD
+ * response.
+ *
+ * @param cls a `struct PurseMergeContext`
+ * @param connection MHD request context
+ * @param[out] mhd_ret set to MHD status on error
+ * @return transaction status
+ */
+static enum GNUNET_DB_QueryStatus
+merge_transaction (void *cls,
+                   struct MHD_Connection *connection,
+                   MHD_RESULT *mhd_ret)
+{
+  struct PurseMergeContext *pcc = cls;
+  enum GNUNET_DB_QueryStatus qs;
+  bool in_conflict = true;
+
+  qs = TEH_plugin->do_purse_merge (TEH_plugin->cls,
+                                   pcc->purse_pub,
+                                   &pcc->merge_sig,
+                                   pcc->merge_timestamp,
+                                   pcc->provider_url,
+                                   &pcc.reserve_pub);
+  if (qs < 0)
+  {
+    if (GNUNET_DB_STATUS_SOFT_ERROR == qs)
+      return qs;
+    TALER_LOG_WARNING (
+      "Failed to store merge purse information in database\n");
+    *mhd_ret =
+      TALER_MHD_reply_with_error (connection,
+                                  MHD_HTTP_INTERNAL_SERVER_ERROR,
+                                  TALER_EC_GENERIC_DB_STORE_FAILED,
+                                  "purse merge");
+    return qs;
+  }
+
+
+  qs = TEH_plugin->do_account_merge (TEH_plugin->cls,
+                                     pcc->purse_pub,
+                                     &pcc->reserve_pub,
+                                     &pcc->reserve_sig);
+  if (qs < 0)
+  {
+    if (GNUNET_DB_STATUS_SOFT_ERROR == qs)
+      return qs;
+    TALER_LOG_WARNING (
+      "Failed to store account purse information in database\n");
+    *mhd_ret =
+      TALER_MHD_reply_with_error (connection,
+                                  MHD_HTTP_INTERNAL_SERVER_ERROR,
+                                  TALER_EC_GENERIC_DB_STORE_FAILED,
+                                  "account merge");
+    return qs;
+  }
+
+  return qs;
+}
+
+
+MHD_RESULT
+TEH_handler_purses_merge (
+  struct MHD_Connection *connection,
+  const struct TALER_PurseContractPublicKeyP *purse_pub,
+  const json_t *root)
+{
+  struct PurseMergeContext pcc = {
+    .purse_pub = purse_pub,
+    .exchange_timestamp = GNUNET_TIME_timestamp_get ()
+  };
+  struct GNUNET_JSON_Specification spec[] = {
+    GNUNET_JSON_spec_string ("payto_uri",
+                             &pcc.payt_uri),
+    GNUNET_JSON_spec_fixed_auto ("reserve_sig",
+                                 &pcc.reserve_sig),
+    GNUNET_JSON_spec_fixed_auto ("merge_sig",
+                                 &pcc.merge_sig),
+    GNUNET_JSON_spec_timestamp ("merge_timestamp",
+                                &pcc.merge_timestamp),
+    GNUNET_JSON_spec_end ()
+  };
+  struct TALER_PurseContractSignatureP purse_sig;
+  enum GNUNET_DB_QueryStatus qs;
+  bool http;
+
+  {
+    enum GNUNET_GenericReturnValue res;
+
+    res = TALER_MHD_parse_json_data (connection,
+                                     root,
+                                     spec);
+    if (GNUNET_SYSERR == res)
+    {
+      GNUNET_break (0);
+      return MHD_NO; /* hard failure */
+    }
+    if (GNUNET_NO == res)
+    {
+      GNUNET_break_op (0);
+      return MHD_YES; /* failure */
+    }
+  }
+
+  pcc.gf = TEH_keys_global_fee_by_time (TEH_keys_get_state (),
+                                        pcc.exchange_timestamp);
+  if (NULL == pcc.gf)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+                "Cannot create purse: global fees not configured!\n");
+    return TALER_MHD_reply_with_error (connection,
+                                       MHD_HTTP_INTERNAL_SERVER_ERROR,
+                                       TALER_EC_EXCHANGE_GENERIC_GLOBAL_FEES_MISSING,
+                                       NULL);
+  }
+  /* Fetch purse details */
+  qs = TEH_plugin->select_purse_request (TEH_plugin->cls,
+                                         pcc->purse_pub,
+                                         &pcc->merge_pub,
+                                         &pcc->purse_expiration,
+                                         &pcc->h_contract_terms,
+                                         &pcc->min_age,
+                                         &pcc->target_amount,
+                                         &pcc->balance,
+                                         &purse_sig);
+  switch (qs)
+  {
+  case GNUNET_DB_STATUS_HARD_ERROR:
+    GNUNET_break (0);
+    return TALER_MHD_reply_with_error (
+      connection,
+      MHD_HTTP_INTERNAL_SERVER_ERROR,
+      TALER_EC_GENERIC_DB_FETCH_FAILED,
+      "select purse request");
+  case GNUNET_DB_STATUS_SOFT_ERROR:
+    GNUNET_break (0);
+    return TALER_MHD_reply_with_error (
+      connection,
+      MHD_HTTP_INTERNAL_SERVER_ERROR,
+      TALER_EC_GENERIC_DB_FETCH_FAILED,
+      "select purse request");
+  case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
+    return TALER_MHD_reply_with_error (
+      connection,
+      MHD_HTTP_NOT_FOUND,
+      TALER_EC_EXCHANGE_MERGE_PURSE_NOT_FOUND,
+      NULL);
+  case GNUNET_DB_STATUS_SUCCESS_ONE_RESULT:
+    /* continued below */
+    break;
+  }
+  /* parse 'payto_uri' into pcc.reserve_pub and provider_url */
+  if ( (0 != strncmp (pcc.payto_uri,
+                      "payto://taler/",
+                      strlen ("payto://taler/"))) &&
+       (0 != strncmp (pcc.payto_uri,
+                      "payto://taler+http/",
+                      strlen ("payto://taler+http/"))) )
+  {
+    GNUNET_break_op (0);
+    return TALER_MHD_reply_with_error (
+      connection,
+      MHD_HTTP_BAD_REQUEST,
+      TALER_EC_GENERIC_PARAMETER_MALFORMED,
+      "payto_uri");
+  }
+
+  http = (0 == strncmp (pcc.payto_uri,
+                        "payto://taler+http/",
+                        strlen ("payto://taler+http/")));
+
+  {
+    const char *host = &pcc.payto_uri[http
+                                      ? strlen ("payto://taler+http/")
+                                      : strlen ("payto://taler/")];
+    const char *slash = strchr (host,
+                                '/');
+
+    if (NULL == slash)
+    {
+      GNUNET_break_op (0);
+      return TALER_MHD_reply_with_error (
+        connection,
+        MHD_HTTP_BAD_REQUEST,
+        TALER_EC_GENERIC_PARAMETER_MALFORMED,
+        "payto_uri");
+    }
+    GNUNET_asprintf (&pcc.provider_url,
+                     "%s://%.*s/",
+                     http ? "http" : "https",
+                     (int) (slash - host),
+                     host);
+    slash++;
+    if (GNUNET_OK !=
+        GNUNET_STRINGS_string_to_data (slash,
+                                       strlen (slash),
+                                       &pcc.reserve_pub,
+                                       sizeof (pcc.reserve_pub)))
+    {
+      GNUNET_break_op (0);
+      GNUNET_free (pcc.provider_url);
+      return TALER_MHD_reply_with_error (
+        connection,
+        MHD_HTTP_BAD_REQUEST,
+        TALER_EC_GENERIC_PARAMETER_MALFORMED,
+        "payto_uri");
+    }
+    slash++;
+  }
+  if (0 == strcmp (pcc.provider_url,
+                   TEH_base_url))
+  {
+    /* we use NULL to represent 'self' as the provider */
+    GNUNET_free (pcc.provider_url);
+  }
+  /* check signatures */
+  if (GNUNET_OK !=
+      TALER_wallet_purse_merge_verify (
+        pcc.payto_url,
+        pcc.merge_timestamp,
+        &pcc.merge_pub,
+        &pcc.merge_sig))
+  {
+    GNUNET_break_op (0);
+    GNUNET_free (pcc.provider_url);
+    return TALER_MHD_reply_with_error (
+      connection,
+      MHD_HTTP_BAD_REQUEST,
+      TALER_EC_EXCHANGE_PURSE_MERGE_INVALID_MERGE_SIGNATURE,
+      NULL);
+  }
+  if (GNUNET_OK !=
+      TALER_wallet_account_merge_verify (
+        pcc.merge_timestamp,
+        pcc.purse_pub,
+        pcc.purse_expiration,
+        &pcc.h_contract_terms,
+        &pcc.target_amount,
+        pcc.min_age,
+        &pcc.reserve_pub,
+        &pcc.reserve_sig))
+  {
+    GNUNET_break_op (0);
+    GNUNET_free (pcc.provider_url);
+    return TALER_MHD_reply_with_error (
+      connection,
+      MHD_HTTP_BAD_REQUEST,
+      TALER_EC_EXCHANGE_PURSE_MERGE_INVALID_RESERVE_SIGNATURE,
+      NULL);
+  }
+
+  /* execute transaction */
+  {
+    MHD_RESULT mhd_ret;
+
+    if (GNUNET_OK !=
+        TEH_DB_run_transaction (connection,
+                                "execute purse merge",
+                                TEH_MT_REQUEST_PURSE_MERGE,
+                                &mhd_ret,
+                                &merge_transaction,
+                                &pcc))
+    {
+      GNUNET_free (pcc.provider_url);
+      return mhd_ret;
+    }
+  }
+
+  GNUNET_free (pcc.provider_url);
+  /* generate regular response */
+  return reply_merge_success (connection,
+                              &pcc);
+}
+
+
+/* end of taler-exchange-httpd_purses_merge.c */