-draft implementation of /purses//merge endpoint

12 files changed, 708 insertions, 37 deletions

diff --git a/src/exchange/Makefile.am b/src/exchange/Makefile.am
index c4c1656a5..949a1dcba 100644
--- a/src/exchange/Makefile.am
+++ b/src/exchange/Makefile.am
@@ -104,6 +104,7 @@ taler_exchange_httpd_SOURCES = \
   taler-exchange-httpd_metrics.c taler-exchange-httpd_metrics.h \
   taler-exchange-httpd_mhd.c taler-exchange-httpd_mhd.h \
   taler-exchange-httpd_purses_create.c taler-exchange-httpd_purses_create.h \
+  taler-exchange-httpd_purses_merge.c taler-exchange-httpd_purses_merge.h \
   taler-exchange-httpd_recoup.c taler-exchange-httpd_recoup.h \
   taler-exchange-httpd_recoup-refresh.c taler-exchange-httpd_recoup-refresh.h \
   taler-exchange-httpd_refreshes_reveal.c taler-exchange-httpd_refreshes_reveal.h \
diff --git a/src/exchange/taler-exchange-httpd_keys.h b/src/exchange/taler-exchange-httpd_keys.h
index 544906ad8..d8fe81e5c 100644
--- a/src/exchange/taler-exchange-httpd_keys.h
+++ b/src/exchange/taler-exchange-httpd_keys.h
@@ -318,8 +318,8 @@ TEH_keys_denomination_cs_r_pub_melt (
  * @param h_denom_pub hash of the public key to revoke
  */
 void
-TEH_keys_denomination_revoke (const struct
-                              TALER_DenominationHashP *h_denom_pub);
+TEH_keys_denomination_revoke (
+  const struct TALER_DenominationHashP *h_denom_pub);
 
 
 /**
diff --git a/src/exchange/taler-exchange-httpd_metrics.h b/src/exchange/taler-exchange-httpd_metrics.h
index d1d20d9aa..4fef6464a 100644
--- a/src/exchange/taler-exchange-httpd_metrics.h
+++ b/src/exchange/taler-exchange-httpd_metrics.h
@@ -36,7 +36,8 @@ enum TEH_MetricTypeRequest
   TEH_MT_REQUEST_WITHDRAW = 2,
   TEH_MT_REQUEST_MELT = 3,
   TEH_MT_REQUEST_PURSE_CREATE = 4,
-  TEH_MT_REQUEST_COUNT = 5 /* MUST BE LAST! */
+  TEH_MT_REQUEST_PURSE_MERGE = 5,
+  TEH_MT_REQUEST_COUNT = 6 /* MUST BE LAST! */
 };
 
 /**
diff --git a/src/exchange/taler-exchange-httpd_purses_merge.c b/src/exchange/taler-exchange-httpd_purses_merge.c
index 07038cb6a..2121169c2 100644
--- a/src/exchange/taler-exchange-httpd_purses_merge.c
+++ b/src/exchange/taler-exchange-httpd_purses_merge.c
@@ -32,6 +32,7 @@
 #include "taler-exchange-httpd_responses.h"
 #include "taler_exchangedb_lib.h"
 #include "taler-exchange-httpd_keys.h"
+#include "taler-exchange-httpd_wire.h"
 
 
 /**
@@ -60,6 +61,11 @@ struct PurseMergeContext
   struct GNUNET_TIME_Timestamp purse_expiration;
 
   /**
+   * When the client signed the merge.
+   */
+  struct GNUNET_TIME_Timestamp merge_timestamp;
+
+  /**
    * Our current time.
    */
   struct GNUNET_TIME_Timestamp exchange_timestamp;
@@ -92,7 +98,7 @@ struct PurseMergeContext
   /**
    * Fees that apply to this operation.
    */
-  const struct TEH_GlobalFee *gf;
+  const struct TALER_WireFeeSet *wf;
 
   /**
    * URI of the account the purse is to be merged into.
@@ -101,7 +107,7 @@ struct PurseMergeContext
   const char *payto_uri;
 
   /**
-   * Base URL of the exchange provider.
+   * Base URL of the exchange provider hosting the reserve.
    */
   char *provider_url;
 
@@ -138,10 +144,26 @@ reply_merge_success (struct MHD_Connection *connection,
       TALER_JSON_pack_amount ("balance",
                               &pcc->balance));
   }
-  // FIXME: check return value...
-  TALER_amount_subtract (&merge_amount,
-                         &pcc->target_amount,
-                         &gf->fees.merge);
+  if (0 == strcmp (pcc->provider_url,
+                   TEH_base_url))
+  {
+    /* wad fee is always zero if we stay at our own exchange */
+    merge_amount = pcc->target_amount;
+  }
+  else
+  {
+    if (0 >
+        TALER_amount_subtract (&merge_amount,
+                               &pcc->target_amount,
+                               &pcc->wf->wad))
+    {
+      GNUNET_break_op (0);
+      return TALER_MHD_reply_with_ec (
+        connection,
+        TALER_EC_EXCHANGE_PURSE_MERGE_WAD_FEE_EXCEEDS_PURSE_VALUE,
+        TALER_amount2s (&pcc->wf->wad));
+    }
+  }
   if (TALER_EC_NONE !=
       (ec = TALER_exchange_online_purse_merged_sign (
          &TEH_keys_exchange_sign_,
@@ -149,8 +171,9 @@ reply_merge_success (struct MHD_Connection *connection,
          pcc->purse_expiration,
          &merge_amount,
          pcc->purse_pub,
-         &pcc->merge_pub,
          &pcc->h_contract_terms,
+         &pcc->reserve_pub,
+         pcc->provider_url,
          &pub,
          &sig)))
   {
@@ -200,7 +223,7 @@ merge_transaction (void *cls,
                                    &pcc->merge_sig,
                                    pcc->merge_timestamp,
                                    pcc->provider_url,
-                                   &pcc.reserve_pub);
+                                   &pcc->reserve_pub);
   if (qs < 0)
   {
     if (GNUNET_DB_STATUS_SOFT_ERROR == qs)
@@ -250,7 +273,7 @@ TEH_handler_purses_merge (
   };
   struct GNUNET_JSON_Specification spec[] = {
     GNUNET_JSON_spec_string ("payto_uri",
-                             &pcc.payt_uri),
+                             &pcc.payto_uri),
     GNUNET_JSON_spec_fixed_auto ("reserve_sig",
                                  &pcc.reserve_sig),
     GNUNET_JSON_spec_fixed_auto ("merge_sig",
@@ -281,9 +304,9 @@ TEH_handler_purses_merge (
     }
   }
 
-  pcc.gf = TEH_keys_global_fee_by_time (TEH_keys_get_state (),
-                                        pcc.exchange_timestamp);
-  if (NULL == pcc.gf)
+  pcc.wf = TEH_wire_fees_by_time (pcc.exchange_timestamp,
+                                  "sepa"); // FIXME!
+  if (NULL == pcc.wf)
   {
     GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                 "Cannot create purse: global fees not configured!\n");
@@ -294,13 +317,13 @@ TEH_handler_purses_merge (
   }
   /* 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,
+                                         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)
   {
@@ -395,8 +418,9 @@ TEH_handler_purses_merge (
   /* check signatures */
   if (GNUNET_OK !=
       TALER_wallet_purse_merge_verify (
-        pcc.payto_url,
+        pcc.payto_uri,
         pcc.merge_timestamp,
+        pcc.purse_pub,
         &pcc.merge_pub,
         &pcc.merge_sig))
   {
diff --git a/src/exchange/taler-exchange-httpd_purses_merge.h b/src/exchange/taler-exchange-httpd_purses_merge.h
new file mode 100644
index 000000000..3bc6e1696
--- /dev/null
+++ b/src/exchange/taler-exchange-httpd_purses_merge.h
@@ -0,0 +1,46 @@
+/*
+  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.h
+ * @brief Handle /purses/$PID/merge requests
+ * @author Christian Grothoff
+ */
+#ifndef TALER_EXCHANGE_HTTPD_PURSES_MERGE_H
+#define TALER_EXCHANGE_HTTPD_PURSES_MERGE_H
+
+#include <gnunet/gnunet_util_lib.h>
+#include <microhttpd.h>
+#include "taler-exchange-httpd.h"
+
+
+/**
+ * Handle a "/purses/$PURSE_PUB/merge" request.  Parses the JSON, and, if
+ * successful, passes the JSON data to #merge_transaction() to further check
+ * the details of the operation specified.  If everything checks out, this
+ * will ultimately lead to the "purses merge" being executed, or rejected.
+ *
+ * @param connection the MHD connection to handle
+ * @param purse_pub public key of the purse
+ * @param root uploaded JSON data
+ * @return MHD result code
+  */
+MHD_RESULT
+TEH_handler_purses_merge (struct MHD_Connection *connection,
+                          const struct TALER_PurseContractPublicKeyP *purse_pub,
+                          const json_t *root);
+
+
+#endif
diff --git a/src/exchange/taler-exchange-httpd_wire.c b/src/exchange/taler-exchange-httpd_wire.c
index e1adde22a..cbd0f6400 100644
--- a/src/exchange/taler-exchange-httpd_wire.c
+++ b/src/exchange/taler-exchange-httpd_wire.c
@@ -158,11 +158,13 @@ make_ec_reply (enum TALER_ErrorCode ec,
                const char *detail)
 {
   return GNUNET_JSON_PACK (
-    GNUNET_JSON_pack_uint64 ("code", ec),
+    GNUNET_JSON_pack_uint64 ("code",
+                             ec),
     GNUNET_JSON_pack_string ("hint",
                              TALER_ErrorCode_get_hint (ec)),
     GNUNET_JSON_pack_allow_null (
-      GNUNET_JSON_pack_string ("detail", detail)));
+      GNUNET_JSON_pack_string ("detail",
+                               detail)));
 }
 
 
@@ -421,4 +423,14 @@ TEH_handler_wire (struct TEH_RequestContext *rc,
 }
 
 
+const struct TALER_WireFeeSet *
+TEH_wire_fees_by_time (
+  struct GNUNET_TIME_Timestamp ts,
+  const char *method)
+{
+  GNUNET_break (0); // FIXME: implement!
+  return NULL;
+}
+
+
 /* end of taler-exchange-httpd_wire.c */
diff --git a/src/exchange/taler-exchange-httpd_wire.h b/src/exchange/taler-exchange-httpd_wire.h
index ed815a57e..75595fe69 100644
--- a/src/exchange/taler-exchange-httpd_wire.h
+++ b/src/exchange/taler-exchange-httpd_wire.h
@@ -34,6 +34,20 @@ TEH_wire_done (void);
 
 
 /**
+ * Look up wire fee structure by @a ts.
+ *
+ * @param ts timestamp to lookup wire fees at
+ * @param method wire method to lookup fees for
+ * @return the wire fee details, or
+ *         NULL if none are configured for @a ts and @a method
+ */
+const struct TALER_WireFeeSet *
+TEH_wire_fees_by_time (
+  struct GNUNET_TIME_Timestamp ts,
+  const char *method);
+
+
+/**
  * Initialize wire subsystem.
  *
  * @return #GNUNET_OK on success
diff --git a/src/include/taler_crypto_lib.h b/src/include/taler_crypto_lib.h
index 5f425341e..332923a9a 100644
--- a/src/include/taler_crypto_lib.h
+++ b/src/include/taler_crypto_lib.h
@@ -3875,6 +3875,33 @@ TALER_exchange_online_purse_created_verify (
   const struct TALER_ExchangeSignatureP *sig);
 
 
+enum TALER_ErrorCode
+TALER_exchange_online_purse_merged_sign (
+  TALER_ExchangeSignCallback scb,
+  struct GNUNET_TIME_Timestamp exchange_time,
+  struct GNUNET_TIME_Timestamp purse_expiration,
+  const struct TALER_Amount *amount_without_fee,
+  const struct TALER_PurseContractPublicKeyP *purse_pub,
+  const struct TALER_PrivateContractHashP *h_contract_terms,
+  const struct TALER_ReservePublicKeyP *reserve_pub,
+  const char *exchange_url,
+  struct TALER_ExchangePublicKeyP *pub,
+  struct TALER_ExchangeSignatureP *sig);
+
+
+enum GNUNET_GenericReturnValue
+TALER_exchange_online_purse_merged_verify (
+  struct GNUNET_TIME_Timestamp exchange_time,
+  struct GNUNET_TIME_Timestamp purse_expiration,
+  const struct TALER_Amount *amount_without_fee,
+  const struct TALER_PurseContractPublicKeyP *purse_pub,
+  const struct TALER_PrivateContractHashP *h_contract_terms,
+  const struct TALER_ReservePublicKeyP *reserve_pub,
+  const char *exchange_url,
+  const struct TALER_ExchangePublicKeyP *pub,
+  const struct TALER_ExchangeSignatureP *sig);
+
+
 /* ********************* offline signing ************************** */
 
 
diff --git a/src/include/taler_exchange_service.h b/src/include/taler_exchange_service.h
index 876e529f9..207573ed3 100644
--- a/src/include/taler_exchange_service.h
+++ b/src/include/taler_exchange_service.h
@@ -4383,12 +4383,14 @@ struct TALER_EXCHANGE_AccountMergeHandle;
  * Inform the exchange that a purse should be merged
  * with a reserve.
  *
- * @param ctx the context
- * @param url HTTP base URL for the exchange with the purse
+ * @param exchange the exchange hosting the purse
  * @param reserve_exchange_url base URL of the exchange with the reserve
  * @param reserve_priv private key of the reserve to merge into
  * @param purse_pub public key of the purse to merge
  * @param merge_priv private key granting us the right to merge
+ * @param h_contract_terms hash of the purses' contract
+ * @param min_age minimum age of deposits into the purse
+ * @param purse_value_after_fees amount that should be in the purse
  * @param merge_timestamp when is the merge happening (current time)
  * @param cb function to call with the exchange's result
  * @param cb_cls closure for @a cb
@@ -4396,12 +4398,14 @@ struct TALER_EXCHANGE_AccountMergeHandle;
  */
 struct TALER_EXCHANGE_AccountMergeHandle *
 TALER_EXCHANGE_account_merge (
-  struct GNUNET_CURL_Context *ctx,
-  const char *url,
+  struct TALER_EXCHANGE_Handle *exchange,
   const char *reserve_exchange_url,
   const struct TALER_ReservePrivateKeyP *reserve_priv,
   const struct TALER_PurseContractPublicKeyP *purse_pub,
   const struct TALER_PurseMergePrivateKeyP *merge_priv,
+  const struct TALER_PrivateContractHashP *h_contract_terms,
+  uint8_t min_age,
+  const struct TALER_Amount *purse_value_after_fees,
   struct GNUNET_TIME_Timestamp merge_timestamp,
   TALER_EXCHANGE_AccountMergeCallback cb,
   void *cb_cls);
@@ -4466,8 +4470,7 @@ struct TALER_EXCHANGE_PurseCreateMergeHandle;
  * Inform the exchange that a purse should be created
  * and merged with a reserve.
  *
- * @param ctx the context
- * @param url HTTP base URL for the exchange
+ * @param exchange the exchange hosting the reserve
  * @param reserve_priv private key of the reserve
  * @param purse_priv private key of the purse
  * @param contract_terms contract the purse is about
@@ -4481,8 +4484,7 @@ struct TALER_EXCHANGE_PurseCreateMergeHandle;
  */
 struct TALER_EXCHANGE_PurseCreateMergeHandle *
 TALER_EXCHANGE_purse_create_with_merge (
-  struct GNUNET_CURL_Context *ctx,
-  const char *url,
+  struct TALER_EXCHANGE_Handle *exchange,
   const struct TALER_ReservePrivateKeyP *reserve_priv,
   const struct TALER_PurseContractPrivateKeyP *purse_priv,
   const json_t *contract_terms,
@@ -4553,8 +4555,7 @@ struct TALER_EXCHANGE_PurseDepositHandle;
  * Inform the exchange that a deposit should be made into
  * a purse.
  *
- * @param ctx the context
- * @param url HTTP base URL for the exchange where we make the deposit
+ * @param exchange the exchange that issued the coins
  * @param purse_exchange_url base URL of the exchange hosting the purse
  * @param purse_pub public key of the purse to merge
  * @param min_age minimum age we need to prove for the purse
@@ -4566,8 +4567,7 @@ struct TALER_EXCHANGE_PurseDepositHandle;
  */
 struct TALER_EXCHANGE_PurseDepositHandle *
 TALER_EXCHANGE_purse_deposit (
-  struct GNUNET_CURL_Context *ctx,
-  const char *url,
+  struct TALER_EXCHANGE_Handle *exchange,
   const char *purse_exchange_url,
   const struct TALER_PurseContractPublicKeyP *purse_pub,
   uint8_t min_age,
diff --git a/src/include/taler_signatures.h b/src/include/taler_signatures.h
index d3e70a9e7..45bdca590 100644
--- a/src/include/taler_signatures.h
+++ b/src/include/taler_signatures.h
@@ -182,6 +182,13 @@
  */
 #define TALER_SIGNATURE_EXCHANGE_CONFIRM_PURSE_CREATION 1045
 
+
+/**
+ * Signature by which the exchange affirms that a purse
+ * was merged into a reserve with a certain amount in it.
+ */
+#define TALER_SIGNATURE_EXCHANGE_CONFIRM_PURSE_MERGED 1046
+
 /**********************/
 /* Auditor signatures */
 /**********************/
diff --git a/src/lib/exchange_api_purse_merge.c b/src/lib/exchange_api_purse_merge.c
new file mode 100644
index 000000000..8f6723ee6
--- /dev/null
+++ b/src/lib/exchange_api_purse_merge.c
@@ -0,0 +1,408 @@
+/*
+   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 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_purse_merge.c
+ * @brief Implementation of the client to merge a purse
+ *        into an account
+ * @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 purse merge with deposit handle
+ */
+struct TALER_EXCHANGE_AccountMergeHandle
+{
+
+  /**
+   * 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_AccountMergeCallback cb;
+
+  /**
+   * Closure for @a cb.
+   */
+  void *cb_cls;
+
+  /**
+   * Expected value in the purse after fees.
+   */
+  struct TALER_Amount purse_value_after_fees;
+
+  /**
+   * Public key of the merge capability.
+   */
+  struct TALER_AccountMergePublicKeyP merge_pub;
+
+  /**
+   * Public key of the purse.
+   */
+  struct TALER_PurseContractPublicKeyP purse_pub;
+
+  /**
+   * Hash over the purse's contrac terms.
+   */
+  struct TALER_PrivateContractHashP h_contract_terms;
+
+  /**
+   * When does the purse expire.
+   */
+  struct GNUNET_TIME_Timestamp purse_expiration;
+};
+
+
+/**
+ * Function called when we're done processing the
+ * HTTP /purse/$PID/merge request.
+ *
+ * @param cls the `struct TALER_EXCHANGE_AccountMergeHandle`
+ * @param response_code HTTP response code, 0 on error
+ * @param response parsed JSON result, NULL on error
+ */
+static void
+handle_purse_merge_finished (void *cls,
+                             long response_code,
+                             const void *response)
+{
+  struct TALER_EXCHANGE_AccountMergeHandle *pch = cls;
+  const json_t *j = response;
+  struct TALER_EXCHANGE_AccountMergeResponse dr = {
+    .hr.reply = j,
+    .hr.http_status = (unsigned int) response_code
+  };
+
+  pch->job = NULL;
+  switch (response_code)
+  {
+  case 0:
+    dr.hr.ec = TALER_EC_GENERIC_INVALID_RESPONSE;
+    break;
+  case MHD_HTTP_OK:
+    {
+      const struct TALER_EXCHANGE_Keys *key_state;
+      struct GNUNET_TIME_Timestamp etime;
+      struct TALER_Amount total_deposited;
+      struct TALER_ExchangeSignatureP exchange_sig;
+      struct TALER_ExchangePublicKeyP exchange_pub;
+      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_timestamp ("exchange_timestamp",
+                                    &etime),
+        TALER_JSON_spec_amount ("total_deposited",
+                                pch->purse_value_after_fees.currency,
+                                &total_deposited),
+        GNUNET_JSON_spec_end ()
+      };
+
+      if (GNUNET_OK !=
+          GNUNET_JSON_parse (j,
+                             spec,
+                             NULL, NULL))
+      {
+        GNUNET_break_op (0);
+        dr.hr.http_status = 0;
+        dr.hr.ec = TALER_EC_GENERIC_REPLY_MALFORMED;
+        break;
+      }
+      key_state = TALER_EXCHANGE_get_keys (pch->exchange);
+      if (GNUNET_OK !=
+          TALER_EXCHANGE_test_signing_key (key_state,
+                                           &exchange_pub))
+      {
+        GNUNET_break_op (0);
+        dr.hr.http_status = 0;
+        dr.hr.ec = TALER_EC_EXCHANGE_PURSE_MERGE_EXCHANGE_SIGNATURE_INVALID;
+        break;
+      }
+      if (GNUNET_OK !=
+          TALER_exchange_online_purse_merged_verify (
+            etime,
+            pch->purse_expiration,
+            &pch->purse_value_after_fees,
+            &total_deposited,
+            &pch->purse_pub,
+            &pch->merge_pub,
+            &pch->h_contract_terms,
+            &exchange_pub,
+            &exchange_sig))
+      {
+        GNUNET_break_op (0);
+        dr.hr.http_status = 0;
+        dr.hr.ec = TALER_EC_EXCHANGE_PURSE_MERGE_EXCHANGE_SIGNATURE_INVALID;
+        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 */
+    dr.hr.ec = TALER_JSON_get_error_code (j);
+    dr.hr.hint = TALER_JSON_get_error_hint (j);
+    break;
+  case MHD_HTTP_FORBIDDEN:
+    dr.hr.ec = TALER_JSON_get_error_code (j);
+    dr.hr.hint = TALER_JSON_get_error_hint (j);
+    /* 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:
+    dr.hr.ec = TALER_JSON_get_error_code (j);
+    dr.hr.hint = TALER_JSON_get_error_hint (j);
+    /* Nothing really to verify, this should never
+       happen, we should pass the JSON reply to the application */
+    break;
+  case MHD_HTTP_CONFLICT:
+    // FIXME: check reply!
+    break;
+  case MHD_HTTP_GONE:
+    /* could happen if denomination was revoked */
+    /* Note: one might want to check /keys for revocation
+       signature here, alas tricky in case our /keys
+       is outdated => left to clients */
+    dr.hr.ec = TALER_JSON_get_error_code (j);
+    dr.hr.hint = TALER_JSON_get_error_hint (j);
+    break;
+  case MHD_HTTP_INTERNAL_SERVER_ERROR:
+    dr.hr.ec = TALER_JSON_get_error_code (j);
+    dr.hr.hint = TALER_JSON_get_error_hint (j);
+    /* Server had an internal issue; we should retry, but this API
+       leaves this to the application */
+    break;
+  default:
+    /* unexpected response code */
+    dr.hr.ec = TALER_JSON_get_error_code (j);
+    dr.hr.hint = TALER_JSON_get_error_hint (j);
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                "Unexpected response code %u/%d for exchange deposit\n",
+                (unsigned int) response_code,
+                dr.hr.ec);
+    GNUNET_break_op (0);
+    break;
+  }
+  pch->cb (pch->cb_cls,
+           &dr);
+  TALER_EXCHANGE_purse_merge_with_deposit_cancel (pch);
+}
+
+
+struct TALER_EXCHANGE_AccountMergeHandle *
+TALER_EXCHANGE_account_merge (
+  struct TALER_EXCHANGE_Handle *exchange,
+  const char *reserve_exchange_url,
+  const struct TALER_ReservePrivateKeyP *reserve_priv,
+  const struct TALER_PurseContractPublicKeyP *purse_pub,
+  const struct TALER_PurseMergePrivateKeyP *merge_priv,
+  const struct TALER_PrivateContractHashP *h_contract_terms,
+  uint8_t min_age,
+  const struct TALER_Amount *purse_value_after_fees,
+  struct GNUNET_TIME_Timestamp purse_expiration,
+  struct GNUNET_TIME_Timestamp merge_timestamp,
+  TALER_EXCHANGE_AccountMergeCallback cb,
+  void *cb_cls)
+{
+  struct TALER_EXCHANGE_AccountMergeHandle *pch;
+  struct GNUNET_CURL_Context *ctx;
+  json_t *merge_obj;
+  CURL *eh;
+  struct TALER_PurseMergeSignatureP merge_sig;
+  struct TALER_ReserveSignatureP account_sig;
+  char arg_str[sizeof (pch->purse_pub) * 2 + 32];
+  char *url;
+  char *reserve_url;
+
+  pch = GNUNET_new (struct TALER_EXCHANGE_AccountMergeHandle);
+  pch->exchange = exchange;
+  pch->cb = cb;
+  pch->cb_cls = cb_cls;
+  pch->merge_timestamp = merge_timestamp;
+  pch->purse_pub = *purse_pub;
+  pch->h_contract_terms = *h_contract_terms;
+  pch->purse_expiration = purse_expiration;
+  pch->purse_value_after_fees = *purse_value_after_fees;
+  GNUNET_assert (GNUNET_YES ==
+                 TEAH_handle_is_ready (exchange));
+  {
+    char pub_str[sizeof (*purse_pub) * 2];
+    char *end;
+
+    end = GNUNET_STRINGS_data_to_string (
+      purse_pub,
+      sizeof (*purse_pub),
+      pub_str,
+      sizeof (pub_str));
+    *end = '\0';
+    GNUNET_snprintf (arg_str,
+                     sizeof (arg_str),
+                     "/purses/%s/merge",
+                     pub_str);
+  }
+  {
+    struct TALER_ReservePublicKeyP reserve_pub;
+    char pub_str[sizeof (reserve_pub) * 2];
+    char *end;
+    const char *exchange_url;
+    bool is_http;
+
+    GNUNET_CRYPTO_eddsa_key_get_public (&reserve_priv->eddsa_priv,
+                                        &reserve_pub.eddsa_pub);
+
+    end = GNUNET_STRINGS_data_to_string (
+      &reserve_pub,
+      sizeof (reserve_pub),
+      pub_str,
+      sizeof (pub_str));
+    *end = '\0';
+    if (0 == strncmp (reserve_exchange_url,
+                      "http://",
+                      strlen ("http://")))
+    {
+      is_http = true;
+      exchange_url = &reserve_exchange_url[strlen ("http://")];
+    }
+    else if (0 == strncmp (reserve_exchange_url,
+                           "https://",
+                           strlen ("https://")))
+    {
+      is_http = false;
+      exchange_url = &reserve_exchange_url[strlen ("https://")];
+    }
+    else
+    {
+      GNUNET_break (0);
+      GNUNET_free (pch);
+      return NULL;
+    }
+    GNUNET_asprintf (&reserve_url,
+                     "payto://%s/%s/%s",
+                     is_http ? "taler+http" : "taler",
+                     pub_str,
+                     exchange_url);
+  }
+  pch->url = TEAH_path_to_url (exchange,
+                               arg_str);
+  if (NULL == pch->url)
+  {
+    GNUNET_break (0);
+    GNUNET_free (pch);
+    return NULL;
+  }
+  GNUNET_CRYPTO_eddsa_key_get_public (&merge_priv->eddsa_priv,
+                                      &pch->merge_pub.eddsa_pub);
+  TALER_wallet_purse_merge_sign (reserve_url,
+                                 merge_timestamp,
+                                 purse_pub,
+                                 merge_priv,
+                                 &merge_sig);
+  TALER_wallet_account_merge_sign (merge_timestamp,
+                                   purse_pub,
+                                   purse_expiration,
+                                   h_contract_terms,
+                                   purse_value_after_fees,
+                                   min_age,
+                                   reserve_priv,
+                                   &reserve_sig);
+  merge_obj = GNUNET_JSON_PACK (
+    GNUNET_JSON_pack_string ("payto_uri",
+                             reserve_url),
+    GNUNET_JSON_pack_data_auto ("merge_sig",
+                                &merge_sig),
+    GNUNET_JSON_pack_data_auto ("reserve_sig",
+                                &reserve_sig),
+    GNUNET_JSON_pack_timestamp ("merge_timestamp",
+                                merge_timestamp));
+  GNUNET_assert (NULL != merge_obj);
+  eh = TALER_EXCHANGE_curl_easy_get_ (pch->url);
+  if ( (NULL == eh) ||
+       (GNUNET_OK !=
+        TALER_curl_easy_post (&pch->ctx,
+                              eh,
+                              merge_obj)) )
+  {
+    GNUNET_break (0);
+    if (NULL != eh)
+      curl_easy_cleanup (eh);
+    json_decref (merge_obj);
+    GNUNET_free (pch->url);
+    GNUNET_free (pch);
+    return NULL;
+  }
+  json_decref (merge_obj);
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "URL for purse merge with deposit: `%s'\n",
+              pch->url);
+  ctx = TEAH_handle_to_context (exchange);
+  pch->job = GNUNET_CURL_job_add2 (ctx,
+                                   eh,
+                                   pch->ctx.headers,
+                                   &handle_purse_merge_deposit_finished,
+                                   pch);
+  return pch;
+}
+
+
+void
+TALER_EXCHANGE_account_merge_cancel (
+  struct TALER_EXCHANGE_AccountMergeHandle *pch)
+{
+  if (NULL != pch->job)
+  {
+    GNUNET_CURL_job_cancel (pch->job);
+    pch->job = NULL;
+  }
+  GNUNET_free (pch->url);
+  TALER_curl_easy_post_finished (&pch->ctx);
+  GNUNET_free (pch);
+}
+
+
+/* end of exchange_api_purse_merge.c */
diff --git a/src/util/exchange_signatures.c b/src/util/exchange_signatures.c
index eeec0d613..d6214ab3e 100644
--- a/src/util/exchange_signatures.c
+++ b/src/util/exchange_signatures.c
@@ -1338,6 +1338,10 @@ TALER_exchange_online_purse_created_sign (
     .exchange_time = GNUNET_TIME_timestamp_hton (exchange_time)
   };
 
+  TALER_amount_hton (&dc.amount_without_fee,
+                     amount_without_fee);
+  TALER_amount_hton (&dc.total_deposited,
+                     total_deposited);
   return scb (&dc.purpose,
               pub,
               sig);
@@ -1366,6 +1370,10 @@ TALER_exchange_online_purse_created_verify (
     .exchange_time = GNUNET_TIME_timestamp_hton (exchange_time)
   };
 
+  TALER_amount_hton (&dc.amount_without_fee,
+                     amount_without_fee);
+  TALER_amount_hton (&dc.total_deposited,
+                     total_deposited);
   return
     GNUNET_CRYPTO_eddsa_verify (TALER_SIGNATURE_EXCHANGE_CONFIRM_PURSE_CREATION,
                                 &dc,
@@ -1374,4 +1382,127 @@ TALER_exchange_online_purse_created_verify (
 }
 
 
+GNUNET_NETWORK_STRUCT_BEGIN
+
+/**
+ * Response by which the exchange affirms that it has
+ * merged a purse into a reserve.
+ */
+struct TALER_PurseMergedConfirmationPS
+{
+
+  /**
+   * Purpose is #TALER_SIGNATURE_EXCHANGE_CONFIRM_PURSE_MERGED
+   */
+  struct GNUNET_CRYPTO_EccSignaturePurpose purpose;
+
+  /**
+   * When did the exchange receive the deposits.
+   */
+  struct GNUNET_TIME_TimestampNBO exchange_time;
+
+  /**
+   * When will the purse expire?
+   */
+  struct GNUNET_TIME_TimestampNBO purse_expiration;
+
+  /**
+   * How much should the purse ultimately contain.
+   */
+  struct TALER_AmountNBO amount_without_fee;
+
+  /**
+   * Public key of the purse.
+   */
+  struct TALER_PurseContractPublicKeyP purse_pub;
+
+  /**
+   * Public key of the reserve.
+   */
+  struct TALER_ReservePublicKeyP reserve_pub;
+
+  /**
+   * Hash of the contract of the purse.
+   */
+  struct TALER_PrivateContractHashP h_contract_terms;
+
+  /**
+   * Hash of the provider URL hosting the reserve.
+   */
+  struct GNUNET_HashCode h_provider_url;
+
+};
+
+GNUNET_NETWORK_STRUCT_END
+
+
+enum TALER_ErrorCode
+TALER_exchange_online_purse_merged_sign (
+  TALER_ExchangeSignCallback scb,
+  struct GNUNET_TIME_Timestamp exchange_time,
+  struct GNUNET_TIME_Timestamp purse_expiration,
+  const struct TALER_Amount *amount_without_fee,
+  const struct TALER_PurseContractPublicKeyP *purse_pub,
+  const struct TALER_PrivateContractHashP *h_contract_terms,
+  const struct TALER_ReservePublicKeyP *reserve_pub,
+  const char *exchange_url,
+  struct TALER_ExchangePublicKeyP *pub,
+  struct TALER_ExchangeSignatureP *sig)
+{
+  struct TALER_PurseMergedConfirmationPS dc = {
+    .purpose.purpose = htonl (TALER_SIGNATURE_EXCHANGE_CONFIRM_PURSE_MERGED),
+    .purpose.size = htonl (sizeof (dc)),
+    .h_contract_terms = *h_contract_terms,
+    .purse_pub = *purse_pub,
+    .reserve_pub = *reserve_pub,
+    .purse_expiration = GNUNET_TIME_timestamp_hton (purse_expiration),
+    .exchange_time = GNUNET_TIME_timestamp_hton (exchange_time)
+  };
+
+  TALER_amount_hton (&dc.amount_without_fee,
+                     amount_without_fee);
+  GNUNET_CRYPTO_hash (exchange_url,
+                      strlen (exchange_url) + 1,
+                      &dc.h_provider_url);
+  return scb (&dc.purpose,
+              pub,
+              sig);
+}
+
+
+enum GNUNET_GenericReturnValue
+TALER_exchange_online_purse_merged_verify (
+  struct GNUNET_TIME_Timestamp exchange_time,
+  struct GNUNET_TIME_Timestamp purse_expiration,
+  const struct TALER_Amount *amount_without_fee,
+  const struct TALER_PurseContractPublicKeyP *purse_pub,
+  const struct TALER_PrivateContractHashP *h_contract_terms,
+  const struct TALER_ReservePublicKeyP *reserve_pub,
+  const char *exchange_url,
+  const struct TALER_ExchangePublicKeyP *pub,
+  const struct TALER_ExchangeSignatureP *sig)
+{
+  struct TALER_PurseMergedConfirmationPS dc = {
+    .purpose.purpose = htonl (TALER_SIGNATURE_EXCHANGE_CONFIRM_PURSE_MERGED),
+    .purpose.size = htonl (sizeof (dc)),
+    .h_contract_terms = *h_contract_terms,
+    .purse_pub = *purse_pub,
+    .reserve_pub = *reserve_pub,
+    .purse_expiration = GNUNET_TIME_timestamp_hton (purse_expiration),
+    .exchange_time = GNUNET_TIME_timestamp_hton (exchange_time)
+  };
+
+  TALER_amount_hton (&dc.amount_without_fee,
+                     amount_without_fee);
+  GNUNET_CRYPTO_hash (exchange_url,
+                      strlen (exchange_url) + 1,
+                      &dc.h_provider_url);
+  return
+    GNUNET_CRYPTO_eddsa_verify (TALER_SIGNATURE_EXCHANGE_CONFIRM_PURSE_MERGED,
+                                &dc,
+                                &sig->eddsa_signature,
+                                &pub->eddsa_pub);
+}
+
+
 /* end of exchange_signatures.c */