split refund file by handler

8 files changed, 635 insertions, 484 deletions

diff --git a/src/backend/Makefile.am b/src/backend/Makefile.am
index 1f583456..7ec1f6bf 100644
--- a/src/backend/Makefile.am
+++ b/src/backend/Makefile.am
@@ -30,6 +30,8 @@ taler_merchant_httpd_SOURCES = \
   taler-merchant-httpd_poll-payment.c taler-merchant-httpd_poll-payment.h \
   taler-merchant-httpd_proposal.c taler-merchant-httpd_proposal.h \
   taler-merchant-httpd_refund.c taler-merchant-httpd_refund.h \
+  taler-merchant-httpd_refund_increase.c taler-merchant-httpd_refund_increase.h \
+  taler-merchant-httpd_refund_lookup.c taler-merchant-httpd_refund_lookup.h \
   taler-merchant-httpd_tip-authorize.c taler-merchant-httpd_tip-authorize.h \
   taler-merchant-httpd_tip-pickup.c taler-merchant-httpd_tip-pickup.h \
   taler-merchant-httpd_tip-query.c taler-merchant-httpd_tip-query.h \
diff --git a/src/backend/taler-merchant-httpd.c b/src/backend/taler-merchant-httpd.c
index ba15625b..cb7e7011 100644
--- a/src/backend/taler-merchant-httpd.c
+++ b/src/backend/taler-merchant-httpd.c
@@ -31,22 +31,24 @@
 #include <taler/taler_exchange_service.h>
 #include "taler_merchantdb_lib.h"
 #include "taler-merchant-httpd.h"
-#include "taler-merchant-httpd_mhd.h"
 #include "taler-merchant-httpd_auditors.h"
+#include "taler-merchant-httpd_check-payment.h"
 #include "taler-merchant-httpd_exchanges.h"
+#include "taler-merchant-httpd_history.h"
+#include "taler-merchant-httpd_mhd.h"
 #include "taler-merchant-httpd_order.h"
-#include "taler-merchant-httpd_proposal.h"
 #include "taler-merchant-httpd_pay.h"
+#include "taler-merchant-httpd_poll-payment.h"
+#include "taler-merchant-httpd_proposal.h"
+#include "taler-merchant-httpd_refund.h"
+#include "taler-merchant-httpd_refund_increase.h"
+#include "taler-merchant-httpd_refund_lookup.h"
 #include "taler-merchant-httpd_track-transaction.h"
 #include "taler-merchant-httpd_track-transfer.h"
 #include "taler-merchant-httpd_tip-authorize.h"
 #include "taler-merchant-httpd_tip-pickup.h"
 #include "taler-merchant-httpd_tip-query.h"
 #include "taler-merchant-httpd_tip-reserve-helper.h"
-#include "taler-merchant-httpd_history.h"
-#include "taler-merchant-httpd_refund.h"
-#include "taler-merchant-httpd_check-payment.h"
-#include "taler-merchant-httpd_poll-payment.h"
 #include "taler-merchant-httpd_config.h"
 
 /**
diff --git a/src/backend/taler-merchant-httpd_refund.c b/src/backend/taler-merchant-httpd_refund.c
index e2f6126c..88e83033 100644
--- a/src/backend/taler-merchant-httpd_refund.c
+++ b/src/backend/taler-merchant-httpd_refund.c
@@ -61,464 +61,6 @@ struct ProcessRefundData
 
 
 /**
- * Information we keep for individual calls
- * to requests that parse JSON, but keep no other state.
- */
-struct TMH_JsonParseContext
-{
-
-  /**
-   * This field MUST be first for handle_mhd_completion_callback() to work
-   * when it treats this struct as a `struct TM_HandlerContext`.
-   */
-  struct TM_HandlerContext hc;
-
-  /**
-   * Placeholder for #TALER_MHD_parse_post_json() to keep its internal state.
-   */
-  void *json_parse_context;
-};
-
-
-/**
- * Make a taler://refund URI
- *
- * @param connection MHD connection to take host and path from
- * @param instance_id merchant's instance ID, must not be NULL
- * @param order_id order ID to show a refund for, must not be NULL
- * @returns the URI, must be freed with #GNUNET_free
- */
-static char *
-make_taler_refund_uri (struct MHD_Connection *connection,
-                       const char *instance_id,
-                       const char *order_id)
-{
-  const char *host;
-  const char *forwarded_host;
-  const char *uri_path;
-  const char *uri_instance_id;
-  const char *query;
-  char *result;
-
-  GNUNET_assert (NULL != instance_id);
-  GNUNET_assert (NULL != order_id);
-  host = MHD_lookup_connection_value (connection,
-                                      MHD_HEADER_KIND,
-                                      MHD_HTTP_HEADER_HOST);
-  forwarded_host = MHD_lookup_connection_value (connection,
-                                                MHD_HEADER_KIND,
-                                                "X-Forwarded-Host");
-  if (NULL != forwarded_host)
-    host = forwarded_host;
-  if (NULL == host)
-  {
-    /* Should never happen, at least the host header should be defined */
-    GNUNET_break (0);
-    return NULL;
-  }
-  uri_path = MHD_lookup_connection_value (connection,
-                                          MHD_HEADER_KIND,
-                                          "X-Forwarded-Prefix");
-  if (NULL == uri_path)
-    uri_path = "-";
-  if (0 == strcmp (instance_id,
-                   "default"))
-    uri_instance_id = "-";
-  else
-    uri_instance_id = instance_id;
-  if (GNUNET_YES == TALER_mhd_is_https (connection))
-    query = "";
-  else
-    query = "?insecure=1";
-  GNUNET_assert (0 < GNUNET_asprintf (&result,
-                                      "taler://refund/%s/%s/%s/%s%s",
-                                      host,
-                                      uri_path,
-                                      uri_instance_id,
-                                      order_id,
-                                      query));
-  return result;
-}
-
-
-/**
- * Custom cleanup routine for a `struct TMH_JsonParseContext`.
- *
- * @param hc the `struct TMH_JsonParseContext` to clean up.
- */
-static void
-json_parse_cleanup (struct TM_HandlerContext *hc)
-{
-  struct TMH_JsonParseContext *jpc = (struct TMH_JsonParseContext *) hc;
-
-  TALER_MHD_parse_post_cleanup_callback (jpc->json_parse_context);
-  GNUNET_free (jpc);
-}
-
-
-/**
- * Handle request for increasing the refund associated with
- * a contract.
- *
- * @param connection the MHD connection to handle
- * @param[in,out] connection_cls the connection's closure (can be updated)
- * @param upload_data upload data
- * @param[in,out] upload_data_size number of bytes (left) in @a upload_data
- * @param mi merchant backend instance, never NULL
- * @return MHD result code
- */
-int
-MH_handler_refund_increase (struct TMH_RequestHandler *rh,
-                            struct MHD_Connection *connection,
-                            void **connection_cls,
-                            const char *upload_data,
-                            size_t *upload_data_size,
-                            struct MerchantInstance *mi)
-{
-  int res;
-  struct TMH_JsonParseContext *ctx;
-  struct TALER_Amount refund;
-  json_t *root;
-  json_t *contract_terms;
-  const char *order_id;
-  const char *reason;
-  struct GNUNET_HashCode h_contract_terms;
-  struct GNUNET_CRYPTO_EddsaSignature sig;
-  struct GNUNET_JSON_Specification spec[] = {
-    TALER_JSON_spec_amount ("refund", &refund),
-    GNUNET_JSON_spec_string ("order_id", &order_id),
-    GNUNET_JSON_spec_string ("reason", &reason),
-    GNUNET_JSON_spec_end ()
-  };
-  enum GNUNET_DB_QueryStatus qs;
-  enum GNUNET_DB_QueryStatus qsx;
-
-  if (NULL == *connection_cls)
-  {
-    ctx = GNUNET_new (struct TMH_JsonParseContext);
-    ctx->hc.cc = &json_parse_cleanup;
-    *connection_cls = ctx;
-  }
-  else
-  {
-    ctx = *connection_cls;
-  }
-  res = TALER_MHD_parse_post_json (connection,
-                                   &ctx->json_parse_context,
-                                   upload_data,
-                                   upload_data_size,
-                                   &root);
-  if (GNUNET_SYSERR == res)
-    return MHD_NO;
-  /* the POST's body has to be further fetched */
-  if ( (GNUNET_NO == res) ||
-       (NULL == root) )
-    return MHD_YES;
-
-  res = TALER_MHD_parse_json_data (connection,
-                                   root,
-                                   spec);
-  if (GNUNET_NO == res)
-  {
-    GNUNET_break_op (0);
-    json_decref (root);
-    return MHD_YES;
-  }
-  if (GNUNET_SYSERR == res)
-  {
-    GNUNET_break_op (0);
-    json_decref (root);
-    return TALER_MHD_reply_with_error (connection,
-                                       MHD_HTTP_BAD_REQUEST,
-                                       TALER_EC_JSON_INVALID,
-                                       "Request body does not match specification");
-  }
-
-  db->preflight (db->cls);
-  /* Convert order id to h_contract_terms */
-  qs = db->find_contract_terms (db->cls,
-                                &contract_terms,
-                                order_id,
-                                &mi->pubkey);
-  if (0 > qs)
-  {
-    /* single, read-only SQL statements should never cause
-       serialization problems */
-    GNUNET_break (GNUNET_DB_STATUS_SOFT_ERROR != qs);
-    /* Always report on hard error as well to enable diagnostics */
-    GNUNET_break (GNUNET_DB_STATUS_HARD_ERROR == qs);
-    json_decref (root);
-    return TALER_MHD_reply_with_error (connection,
-                                       MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_REFUND_LOOKUP_DB_ERROR,
-                                       "An error occurred while retrieving payment data from db");
-  }
-  if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
-  {
-    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
-                "Unknown order id given: `%s'\n",
-                order_id);
-    json_decref (root);
-    return TALER_MHD_reply_with_error (connection,
-                                       MHD_HTTP_NOT_FOUND,
-                                       TALER_EC_REFUND_ORDER_ID_UNKNOWN,
-                                       "order_id not found in database");
-  }
-
-  if (GNUNET_OK !=
-      TALER_JSON_hash (contract_terms,
-                       &h_contract_terms))
-  {
-    GNUNET_break (0);
-    GNUNET_JSON_parse_free (spec);
-    json_decref (contract_terms);
-    json_decref (root);
-    return TALER_MHD_reply_with_error (connection,
-                                       MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_INTERNAL_LOGIC_ERROR,
-                                       "Could not hash contract terms");
-  }
-  for (unsigned int i = 0; i<MAX_RETRIES; i++)
-  {
-    if (GNUNET_OK !=
-        db->start (db->cls,
-                   "increase refund"))
-    {
-      GNUNET_break (0);
-      json_decref (contract_terms);
-      json_decref (root);
-      return GNUNET_DB_STATUS_HARD_ERROR;
-    }
-    qs = db->increase_refund_for_contract_NT (db->cls,
-                                              &h_contract_terms,
-                                              &mi->pubkey,
-                                              &refund,
-                                              reason);
-    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-                "increase refund returned %d\n",
-                qs);
-    if (GNUNET_DB_STATUS_HARD_ERROR == qs)
-    {
-      GNUNET_break (0);
-      db->rollback (db->cls);
-      break;
-    }
-    if (GNUNET_DB_STATUS_SOFT_ERROR == qs)
-    {
-      db->rollback (db->cls);
-      continue;
-    }
-    /* Got one or more deposits */
-    if (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT != qs)
-    {
-      db->rollback (db->cls);
-      break;
-    }
-    qsx = db->commit (db->cls);
-    if (GNUNET_DB_STATUS_HARD_ERROR == qsx)
-    {
-      GNUNET_break (0);
-      qs = qsx;
-      break;
-    }
-    if (GNUNET_DB_STATUS_SOFT_ERROR != qsx)
-      break;
-  }
-  if (0 > qs)
-  {
-    /* Special report if retries insufficient */
-    GNUNET_break (GNUNET_DB_STATUS_SOFT_ERROR != qs);
-    /* Always report on hard error as well to enable diagnostics */
-    GNUNET_break (GNUNET_DB_STATUS_HARD_ERROR == qs);
-    GNUNET_JSON_parse_free (spec);
-    json_decref (contract_terms);
-    json_decref (root);
-    return TALER_MHD_reply_with_error (connection,
-                                       MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_REFUND_MERCHANT_DB_COMMIT_ERROR,
-                                       "Internal database error or refund amount too big");
-  }
-  if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
-  {
-    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
-                "Refunded amount lower or equal to previous refund: %s\n",
-                TALER_amount2s (&refund));
-    GNUNET_JSON_parse_free (spec);
-    json_decref (contract_terms);
-    json_decref (root);
-    return TALER_MHD_reply_with_error (connection,
-                                       MHD_HTTP_CONFLICT,
-                                       TALER_EC_REFUND_INCONSISTENT_AMOUNT,
-                                       "Amount incorrect: not larger than the previous one");
-  }
-
-  /**
-   * Return to the frontend at this point.  The frontend will then return
-   * a "402 Payment required" carrying a "X-Taler-Refund-Url: www"
-   * where 'www' is the URL where the wallet can automatically fetch
-   * the refund permission.
-   *
-   * Just a "200 OK" should be fine here, as the frontend has all
-   * the information needed to generate the right response.
-   *///
-  {
-    struct TALER_MerchantRefundConfirmationPS confirmation = {
-      .purpose.purpose = htonl (TALER_SIGNATURE_MERCHANT_REFUND_OK),
-      .purpose.size = htonl (sizeof (confirmation))
-    };
-
-    GNUNET_CRYPTO_hash (order_id,
-                        strlen (order_id),
-                        &confirmation.h_order_id);
-
-    if (GNUNET_OK !=
-        GNUNET_CRYPTO_eddsa_sign (&mi->privkey.eddsa_priv,
-                                  &confirmation.purpose,
-                                  &sig))
-    {
-      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
-                  "Failed to sign successful refund confirmation\n");
-      json_decref (contract_terms);
-      GNUNET_JSON_parse_free (spec);
-      json_decref (root);
-      return TALER_MHD_reply_with_error (connection,
-                                         MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         TALER_EC_REFUND_MERCHANT_SIGNING_FAILED,
-                                         "Refund done, but failed to sign confirmation");
-
-    }
-  }
-
-  {
-    int ret;
-    char *taler_refund_uri;
-
-    taler_refund_uri = make_taler_refund_uri (connection,
-                                              mi->id,
-                                              order_id);
-    ret = TALER_MHD_reply_json_pack (connection,
-                                     MHD_HTTP_OK,
-                                     "{s:o, s:o, s:s}",
-                                     "sig", GNUNET_JSON_from_data_auto (&sig),
-                                     "contract_terms", contract_terms,
-                                     "taler_refund_uri", taler_refund_uri);
-    GNUNET_free (taler_refund_uri);
-    GNUNET_JSON_parse_free (spec);
-    json_decref (root);
-    return ret;
-  }
-}
-
-
-/**
- * Return refund situation about a contract.
- *
- * @param rh context of the handler
- * @param connection the MHD connection to handle
- * @param[in,out] connection_cls the connection's closure (can be updated)
- * @param upload_data upload data
- * @param[in,out] upload_data_size number of bytes (left) in @a upload_data
- * @param mi merchant backend instance, never NULL
- * @return MHD result code
- */
-int
-MH_handler_refund_lookup (struct TMH_RequestHandler *rh,
-                          struct MHD_Connection *connection,
-                          void **connection_cls,
-                          const char *upload_data,
-                          size_t *upload_data_size,
-                          struct MerchantInstance *mi)
-{
-  const char *order_id;
-  struct GNUNET_HashCode h_contract_terms;
-  json_t *contract_terms;
-  enum GNUNET_DB_QueryStatus qs;
-
-  order_id = MHD_lookup_connection_value (connection,
-                                          MHD_GET_ARGUMENT_KIND,
-                                          "order_id");
-  if (NULL == order_id)
-  {
-    GNUNET_break_op (0);
-    return TALER_MHD_reply_with_error (connection,
-                                       MHD_HTTP_BAD_REQUEST,
-                                       TALER_EC_PARAMETER_MISSING,
-                                       "order_id");
-  }
-
-  /* Convert order id to h_contract_terms */
-  contract_terms = NULL;
-  db->preflight (db->cls);
-  qs = db->find_contract_terms (db->cls,
-                                &contract_terms,
-                                order_id,
-                                &mi->pubkey);
-  if (0 > qs)
-  {
-    /* single, read-only SQL statements should never cause
-       serialization problems */
-    GNUNET_break (GNUNET_DB_STATUS_SOFT_ERROR != qs);
-    /* Always report on hard error as well to enable diagnostics */
-    GNUNET_break (GNUNET_DB_STATUS_HARD_ERROR == qs);
-    return TALER_MHD_reply_with_error (connection,
-                                       MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_REFUND_LOOKUP_DB_ERROR,
-                                       "database error looking up order_id from merchant_contract_terms table");
-  }
-
-  if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
-  {
-    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
-                "Unknown order id given: `%s'\n",
-                order_id);
-    return TALER_MHD_reply_with_error (connection,
-                                       MHD_HTTP_NOT_FOUND,
-                                       TALER_EC_REFUND_ORDER_ID_UNKNOWN,
-                                       "order_id not found in database");
-  }
-
-  if (GNUNET_OK !=
-      TALER_JSON_hash (contract_terms,
-                       &h_contract_terms))
-  {
-    GNUNET_break (0);
-    json_decref (contract_terms);
-    return TALER_MHD_reply_with_error (connection,
-                                       MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_INTERNAL_LOGIC_ERROR,
-                                       "Could not hash contract terms");
-  }
-  json_decref (contract_terms);
-
-  {
-    json_t *response;
-    enum TALER_ErrorCode ec;
-    const char *errmsg;
-
-    response = TM_get_refund_json (mi,
-                                   &h_contract_terms,
-                                   &ec,
-                                   &errmsg);
-    if (NULL == response)
-      return TALER_MHD_reply_with_error (connection,
-                                         MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         ec,
-                                         errmsg);
-    return TALER_MHD_reply_json_pack (connection, MHD_HTTP_OK,
-                                      "{s:o, s:o, s:o}",
-                                      "refund_permissions",
-                                      response,
-                                      "merchant_pub",
-                                      GNUNET_JSON_from_data_auto (
-                                        &mi->pubkey),
-                                      "h_contract_terms",
-                                      GNUNET_JSON_from_data_auto (
-                                        &h_contract_terms));
-  }
-}
-
-
-/**
  * Function called with information about a refund.
  * It is responsible for packing up the data to return.
  *
diff --git a/src/backend/taler-merchant-httpd_refund.h b/src/backend/taler-merchant-httpd_refund.h
index 9713adb0..636d291a 100644
--- a/src/backend/taler-merchant-httpd_refund.h
+++ b/src/backend/taler-merchant-httpd_refund.h
@@ -27,26 +27,6 @@
 
 
 /**
- * Handle request for increasing the refund associated with
- * a contract.
- *
- * @param connection the MHD connection to handle
- * @param[in,out] connection_cls the connection's closure (can be updated)
- * @param upload_data upload data
- * @param[in,out] upload_data_size number of bytes (left) in @a upload_data
- * @param mi merchant backend instance, never NULL
- * @return MHD result code
- */
-int
-MH_handler_refund_increase (struct TMH_RequestHandler *rh,
-                            struct MHD_Connection *connection,
-                            void **connection_cls,
-                            const char *upload_data,
-                            size_t *upload_data_size,
-                            struct MerchantInstance *mi);
-
-
-/**
  * Return refund situation about a contract.
  *
  * @param rh context of the handler
diff --git a/src/backend/taler-merchant-httpd_refund_increase.c b/src/backend/taler-merchant-httpd_refund_increase.c
new file mode 100644
index 00000000..33cf4d99
--- /dev/null
+++ b/src/backend/taler-merchant-httpd_refund_increase.c
@@ -0,0 +1,385 @@
+/*
+  This file is part of TALER
+  (C) 2014-2020 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 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 backend/taler-merchant-httpd_refund_increase.c
+ * @brief Handle request to increase the refund for an order
+ * @author Marcello Stanisci
+ */
+#include "platform.h"
+#include <jansson.h>
+#include <taler/taler_signatures.h>
+#include <taler/taler_json_lib.h>
+#include "taler-merchant-httpd.h"
+#include "taler-merchant-httpd_refund.h"
+
+/**
+ * How often do we retry the non-trivial refund INSERT database
+ * transaction?
+ */
+#define MAX_RETRIES 5
+
+
+/**
+ * Information we keep for individual calls
+ * to requests that parse JSON, but keep no other state.
+ */
+struct TMH_JsonParseContext
+{
+
+  /**
+   * This field MUST be first for handle_mhd_completion_callback() to work
+   * when it treats this struct as a `struct TM_HandlerContext`.
+   */
+  struct TM_HandlerContext hc;
+
+  /**
+   * Placeholder for #TALER_MHD_parse_post_json() to keep its internal state.
+   */
+  void *json_parse_context;
+};
+
+
+/**
+ * Make a taler://refund URI
+ *
+ * @param connection MHD connection to take host and path from
+ * @param instance_id merchant's instance ID, must not be NULL
+ * @param order_id order ID to show a refund for, must not be NULL
+ * @returns the URI, must be freed with #GNUNET_free
+ */
+static char *
+make_taler_refund_uri (struct MHD_Connection *connection,
+                       const char *instance_id,
+                       const char *order_id)
+{
+  const char *host;
+  const char *forwarded_host;
+  const char *uri_path;
+  const char *uri_instance_id;
+  const char *query;
+  char *result;
+
+  GNUNET_assert (NULL != instance_id);
+  GNUNET_assert (NULL != order_id);
+  host = MHD_lookup_connection_value (connection,
+                                      MHD_HEADER_KIND,
+                                      MHD_HTTP_HEADER_HOST);
+  forwarded_host = MHD_lookup_connection_value (connection,
+                                                MHD_HEADER_KIND,
+                                                "X-Forwarded-Host");
+  if (NULL != forwarded_host)
+    host = forwarded_host;
+  if (NULL == host)
+  {
+    /* Should never happen, at least the host header should be defined */
+    GNUNET_break (0);
+    return NULL;
+  }
+  uri_path = MHD_lookup_connection_value (connection,
+                                          MHD_HEADER_KIND,
+                                          "X-Forwarded-Prefix");
+  if (NULL == uri_path)
+    uri_path = "-";
+  if (0 == strcmp (instance_id,
+                   "default"))
+    uri_instance_id = "-";
+  else
+    uri_instance_id = instance_id;
+  if (GNUNET_YES == TALER_mhd_is_https (connection))
+    query = "";
+  else
+    query = "?insecure=1";
+  GNUNET_assert (0 < GNUNET_asprintf (&result,
+                                      "taler://refund/%s/%s/%s/%s%s",
+                                      host,
+                                      uri_path,
+                                      uri_instance_id,
+                                      order_id,
+                                      query));
+  return result;
+}
+
+
+/**
+ * Custom cleanup routine for a `struct TMH_JsonParseContext`.
+ *
+ * @param hc the `struct TMH_JsonParseContext` to clean up.
+ */
+static void
+json_parse_cleanup (struct TM_HandlerContext *hc)
+{
+  struct TMH_JsonParseContext *jpc = (struct TMH_JsonParseContext *) hc;
+
+  TALER_MHD_parse_post_cleanup_callback (jpc->json_parse_context);
+  GNUNET_free (jpc);
+}
+
+
+/**
+ * Handle request for increasing the refund associated with
+ * a contract.
+ *
+ * @param connection the MHD connection to handle
+ * @param[in,out] connection_cls the connection's closure (can be updated)
+ * @param upload_data upload data
+ * @param[in,out] upload_data_size number of bytes (left) in @a upload_data
+ * @param mi merchant backend instance, never NULL
+ * @return MHD result code
+ */
+int
+MH_handler_refund_increase (struct TMH_RequestHandler *rh,
+                            struct MHD_Connection *connection,
+                            void **connection_cls,
+                            const char *upload_data,
+                            size_t *upload_data_size,
+                            struct MerchantInstance *mi)
+{
+  int res;
+  struct TMH_JsonParseContext *ctx;
+  struct TALER_Amount refund;
+  json_t *root;
+  json_t *contract_terms;
+  const char *order_id;
+  const char *reason;
+  struct GNUNET_HashCode h_contract_terms;
+  struct GNUNET_CRYPTO_EddsaSignature sig;
+  struct GNUNET_JSON_Specification spec[] = {
+    TALER_JSON_spec_amount ("refund", &refund),
+    GNUNET_JSON_spec_string ("order_id", &order_id),
+    GNUNET_JSON_spec_string ("reason", &reason),
+    GNUNET_JSON_spec_end ()
+  };
+  enum GNUNET_DB_QueryStatus qs;
+  enum GNUNET_DB_QueryStatus qsx;
+
+  if (NULL == *connection_cls)
+  {
+    ctx = GNUNET_new (struct TMH_JsonParseContext);
+    ctx->hc.cc = &json_parse_cleanup;
+    *connection_cls = ctx;
+  }
+  else
+  {
+    ctx = *connection_cls;
+  }
+  res = TALER_MHD_parse_post_json (connection,
+                                   &ctx->json_parse_context,
+                                   upload_data,
+                                   upload_data_size,
+                                   &root);
+  if (GNUNET_SYSERR == res)
+    return MHD_NO;
+  /* the POST's body has to be further fetched */
+  if ( (GNUNET_NO == res) ||
+       (NULL == root) )
+    return MHD_YES;
+
+  res = TALER_MHD_parse_json_data (connection,
+                                   root,
+                                   spec);
+  if (GNUNET_NO == res)
+  {
+    GNUNET_break_op (0);
+    json_decref (root);
+    return MHD_YES;
+  }
+  if (GNUNET_SYSERR == res)
+  {
+    GNUNET_break_op (0);
+    json_decref (root);
+    return TALER_MHD_reply_with_error (connection,
+                                       MHD_HTTP_BAD_REQUEST,
+                                       TALER_EC_JSON_INVALID,
+                                       "Request body does not match specification");
+  }
+
+  db->preflight (db->cls);
+  /* Convert order id to h_contract_terms */
+  qs = db->find_contract_terms (db->cls,
+                                &contract_terms,
+                                order_id,
+                                &mi->pubkey);
+  if (0 > qs)
+  {
+    /* single, read-only SQL statements should never cause
+       serialization problems */
+    GNUNET_break (GNUNET_DB_STATUS_SOFT_ERROR != qs);
+    /* Always report on hard error as well to enable diagnostics */
+    GNUNET_break (GNUNET_DB_STATUS_HARD_ERROR == qs);
+    json_decref (root);
+    return TALER_MHD_reply_with_error (connection,
+                                       MHD_HTTP_INTERNAL_SERVER_ERROR,
+                                       TALER_EC_REFUND_LOOKUP_DB_ERROR,
+                                       "An error occurred while retrieving payment data from db");
+  }
+  if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+                "Unknown order id given: `%s'\n",
+                order_id);
+    json_decref (root);
+    return TALER_MHD_reply_with_error (connection,
+                                       MHD_HTTP_NOT_FOUND,
+                                       TALER_EC_REFUND_ORDER_ID_UNKNOWN,
+                                       "order_id not found in database");
+  }
+
+  if (GNUNET_OK !=
+      TALER_JSON_hash (contract_terms,
+                       &h_contract_terms))
+  {
+    GNUNET_break (0);
+    GNUNET_JSON_parse_free (spec);
+    json_decref (contract_terms);
+    json_decref (root);
+    return TALER_MHD_reply_with_error (connection,
+                                       MHD_HTTP_INTERNAL_SERVER_ERROR,
+                                       TALER_EC_INTERNAL_LOGIC_ERROR,
+                                       "Could not hash contract terms");
+  }
+  for (unsigned int i = 0; i<MAX_RETRIES; i++)
+  {
+    if (GNUNET_OK !=
+        db->start (db->cls,
+                   "increase refund"))
+    {
+      GNUNET_break (0);
+      json_decref (contract_terms);
+      json_decref (root);
+      return GNUNET_DB_STATUS_HARD_ERROR;
+    }
+    qs = db->increase_refund_for_contract_NT (db->cls,
+                                              &h_contract_terms,
+                                              &mi->pubkey,
+                                              &refund,
+                                              reason);
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "increase refund returned %d\n",
+                qs);
+    if (GNUNET_DB_STATUS_HARD_ERROR == qs)
+    {
+      GNUNET_break (0);
+      db->rollback (db->cls);
+      break;
+    }
+    if (GNUNET_DB_STATUS_SOFT_ERROR == qs)
+    {
+      db->rollback (db->cls);
+      continue;
+    }
+    /* Got one or more deposits */
+    if (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT != qs)
+    {
+      db->rollback (db->cls);
+      break;
+    }
+    qsx = db->commit (db->cls);
+    if (GNUNET_DB_STATUS_HARD_ERROR == qsx)
+    {
+      GNUNET_break (0);
+      qs = qsx;
+      break;
+    }
+    if (GNUNET_DB_STATUS_SOFT_ERROR != qsx)
+      break;
+  }
+  if (0 > qs)
+  {
+    /* Special report if retries insufficient */
+    GNUNET_break (GNUNET_DB_STATUS_SOFT_ERROR != qs);
+    /* Always report on hard error as well to enable diagnostics */
+    GNUNET_break (GNUNET_DB_STATUS_HARD_ERROR == qs);
+    GNUNET_JSON_parse_free (spec);
+    json_decref (contract_terms);
+    json_decref (root);
+    return TALER_MHD_reply_with_error (connection,
+                                       MHD_HTTP_INTERNAL_SERVER_ERROR,
+                                       TALER_EC_REFUND_MERCHANT_DB_COMMIT_ERROR,
+                                       "Internal database error or refund amount too big");
+  }
+  if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+                "Refunded amount lower or equal to previous refund: %s\n",
+                TALER_amount2s (&refund));
+    GNUNET_JSON_parse_free (spec);
+    json_decref (contract_terms);
+    json_decref (root);
+    return TALER_MHD_reply_with_error (connection,
+                                       MHD_HTTP_CONFLICT,
+                                       TALER_EC_REFUND_INCONSISTENT_AMOUNT,
+                                       "Amount incorrect: not larger than the previous one");
+  }
+
+  /**
+   * Return to the frontend at this point.  The frontend will then return
+   * a "402 Payment required" carrying a "X-Taler-Refund-Url: www"
+   * where 'www' is the URL where the wallet can automatically fetch
+   * the refund permission.
+   *
+   * Just a "200 OK" should be fine here, as the frontend has all
+   * the information needed to generate the right response.
+   *///
+  {
+    struct TALER_MerchantRefundConfirmationPS confirmation = {
+      .purpose.purpose = htonl (TALER_SIGNATURE_MERCHANT_REFUND_OK),
+      .purpose.size = htonl (sizeof (confirmation))
+    };
+
+    GNUNET_CRYPTO_hash (order_id,
+                        strlen (order_id),
+                        &confirmation.h_order_id);
+
+    if (GNUNET_OK !=
+        GNUNET_CRYPTO_eddsa_sign (&mi->privkey.eddsa_priv,
+                                  &confirmation.purpose,
+                                  &sig))
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                  "Failed to sign successful refund confirmation\n");
+      json_decref (contract_terms);
+      GNUNET_JSON_parse_free (spec);
+      json_decref (root);
+      return TALER_MHD_reply_with_error (connection,
+                                         MHD_HTTP_INTERNAL_SERVER_ERROR,
+                                         TALER_EC_REFUND_MERCHANT_SIGNING_FAILED,
+                                         "Refund done, but failed to sign confirmation");
+
+    }
+  }
+
+  {
+    int ret;
+    char *taler_refund_uri;
+
+    taler_refund_uri = make_taler_refund_uri (connection,
+                                              mi->id,
+                                              order_id);
+    ret = TALER_MHD_reply_json_pack (connection,
+                                     MHD_HTTP_OK,
+                                     "{s:o, s:o, s:s}",
+                                     "sig", GNUNET_JSON_from_data_auto (&sig),
+                                     "contract_terms", contract_terms,
+                                     "taler_refund_uri", taler_refund_uri);
+    GNUNET_free (taler_refund_uri);
+    GNUNET_JSON_parse_free (spec);
+    json_decref (root);
+    return ret;
+  }
+}
+
+
+/* end of taler-merchant-httpd_refund_increase.c */
diff --git a/src/backend/taler-merchant-httpd_refund_increase.h b/src/backend/taler-merchant-httpd_refund_increase.h
new file mode 100644
index 00000000..82a48f4c
--- /dev/null
+++ b/src/backend/taler-merchant-httpd_refund_increase.h
@@ -0,0 +1,49 @@
+/*
+  This file is part of TALER
+  (C) 2014, 2015, 2016, 2017 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 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 backend/taler-merchant-httpd_refund_increase.h
+ * @brief HTTP serving layer mainly intended to communicate with the frontend
+ * @author Marcello Stanisci
+ */
+
+#ifndef TALER_MERCHANT_HTTPD_REFUND_INCREASE_H
+#define TALER_MERCHANT_HTTPD_REFUND_INCREASE_H
+#include <microhttpd.h>
+#include "taler-merchant-httpd.h"
+
+
+/**
+ * Handle request for increasing the refund associated with
+ * a contract.
+ *
+ * @param connection the MHD connection to handle
+ * @param[in,out] connection_cls the connection's closure (can be updated)
+ * @param upload_data upload data
+ * @param[in,out] upload_data_size number of bytes (left) in @a upload_data
+ * @param mi merchant backend instance, never NULL
+ * @return MHD result code
+ */
+int
+MH_handler_refund_increase (struct TMH_RequestHandler *rh,
+                            struct MHD_Connection *connection,
+                            void **connection_cls,
+                            const char *upload_data,
+                            size_t *upload_data_size,
+                            struct MerchantInstance *mi);
+
+
+#endif
diff --git a/src/backend/taler-merchant-httpd_refund_lookup.c b/src/backend/taler-merchant-httpd_refund_lookup.c
new file mode 100644
index 00000000..36a6b88f
--- /dev/null
+++ b/src/backend/taler-merchant-httpd_refund_lookup.c
@@ -0,0 +1,143 @@
+/*
+  This file is part of TALER
+  (C) 2014-2020 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 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 backend/taler-merchant-httpd_refund_lookup.c
+ * @brief refund handling logic
+ * @author Marcello Stanisci
+ */
+#include "platform.h"
+#include <jansson.h>
+#include <taler/taler_signatures.h>
+#include <taler/taler_json_lib.h>
+#include "taler-merchant-httpd.h"
+#include "taler-merchant-httpd_refund.h"
+
+/**
+ * How often do we retry the non-trivial refund INSERT database
+ * transaction?
+ */
+#define MAX_RETRIES 5
+
+
+/**
+ * Return refund situation about a contract.
+ *
+ * @param rh context of the handler
+ * @param connection the MHD connection to handle
+ * @param[in,out] connection_cls the connection's closure (can be updated)
+ * @param upload_data upload data
+ * @param[in,out] upload_data_size number of bytes (left) in @a upload_data
+ * @param mi merchant backend instance, never NULL
+ * @return MHD result code
+ */
+int
+MH_handler_refund_lookup (struct TMH_RequestHandler *rh,
+                          struct MHD_Connection *connection,
+                          void **connection_cls,
+                          const char *upload_data,
+                          size_t *upload_data_size,
+                          struct MerchantInstance *mi)
+{
+  const char *order_id;
+  struct GNUNET_HashCode h_contract_terms;
+  json_t *contract_terms;
+  enum GNUNET_DB_QueryStatus qs;
+
+  order_id = MHD_lookup_connection_value (connection,
+                                          MHD_GET_ARGUMENT_KIND,
+                                          "order_id");
+  if (NULL == order_id)
+  {
+    GNUNET_break_op (0);
+    return TALER_MHD_reply_with_error (connection,
+                                       MHD_HTTP_BAD_REQUEST,
+                                       TALER_EC_PARAMETER_MISSING,
+                                       "order_id");
+  }
+
+  /* Convert order id to h_contract_terms */
+  contract_terms = NULL;
+  db->preflight (db->cls);
+  qs = db->find_contract_terms (db->cls,
+                                &contract_terms,
+                                order_id,
+                                &mi->pubkey);
+  if (0 > qs)
+  {
+    /* single, read-only SQL statements should never cause
+       serialization problems */
+    GNUNET_break (GNUNET_DB_STATUS_SOFT_ERROR != qs);
+    /* Always report on hard error as well to enable diagnostics */
+    GNUNET_break (GNUNET_DB_STATUS_HARD_ERROR == qs);
+    return TALER_MHD_reply_with_error (connection,
+                                       MHD_HTTP_INTERNAL_SERVER_ERROR,
+                                       TALER_EC_REFUND_LOOKUP_DB_ERROR,
+                                       "database error looking up order_id from merchant_contract_terms table");
+  }
+
+  if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+                "Unknown order id given: `%s'\n",
+                order_id);
+    return TALER_MHD_reply_with_error (connection,
+                                       MHD_HTTP_NOT_FOUND,
+                                       TALER_EC_REFUND_ORDER_ID_UNKNOWN,
+                                       "order_id not found in database");
+  }
+
+  if (GNUNET_OK !=
+      TALER_JSON_hash (contract_terms,
+                       &h_contract_terms))
+  {
+    GNUNET_break (0);
+    json_decref (contract_terms);
+    return TALER_MHD_reply_with_error (connection,
+                                       MHD_HTTP_INTERNAL_SERVER_ERROR,
+                                       TALER_EC_INTERNAL_LOGIC_ERROR,
+                                       "Could not hash contract terms");
+  }
+  json_decref (contract_terms);
+
+  {
+    json_t *response;
+    enum TALER_ErrorCode ec;
+    const char *errmsg;
+
+    response = TM_get_refund_json (mi,
+                                   &h_contract_terms,
+                                   &ec,
+                                   &errmsg);
+    if (NULL == response)
+      return TALER_MHD_reply_with_error (connection,
+                                         MHD_HTTP_INTERNAL_SERVER_ERROR,
+                                         ec,
+                                         errmsg);
+    return TALER_MHD_reply_json_pack (connection, MHD_HTTP_OK,
+                                      "{s:o, s:o, s:o}",
+                                      "refund_permissions",
+                                      response,
+                                      "merchant_pub",
+                                      GNUNET_JSON_from_data_auto (
+                                        &mi->pubkey),
+                                      "h_contract_terms",
+                                      GNUNET_JSON_from_data_auto (
+                                        &h_contract_terms));
+  }
+}
+
+
+/* end of taler-merchant-httpd_refund_lookup.c */
diff --git a/src/backend/taler-merchant-httpd_refund_lookup.h b/src/backend/taler-merchant-httpd_refund_lookup.h
new file mode 100644
index 00000000..9d34ad88
--- /dev/null
+++ b/src/backend/taler-merchant-httpd_refund_lookup.h
@@ -0,0 +1,48 @@
+/*
+  This file is part of TALER
+  (C) 2014, 2015, 2016, 2017 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 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 backend/taler-merchant-httpd_refund_lookup.h
+ * @brief
+ * @author Marcello Stanisci
+ */
+
+#ifndef TALER_MERCHANT_HTTPD_REFUND_LOOKUP_H
+#define TALER_MERCHANT_HTTPD_REFUND_LOOKUP_H
+#include <microhttpd.h>
+#include "taler-merchant-httpd.h"
+
+
+/**
+ * Return refund situation about a contract.
+ *
+ * @param rh context of the handler
+ * @param connection the MHD connection to handle
+ * @param[in,out] connection_cls the connection's closure (can be updated)
+ * @param upload_data upload data
+ * @param[in,out] upload_data_size number of bytes (left) in @a upload_data
+ * @param mi merchant backend instance, never NULL
+ * @return MHD result code
+ */
+int
+MH_handler_refund_lookup (struct TMH_RequestHandler *rh,
+                          struct MHD_Connection *connection,
+                          void **connection_cls,
+                          const char *upload_data,
+                          size_t *upload_data_size,
+                          struct MerchantInstance *mi);
+
+#endif