adding merchant library +

testcases for contract mgmt + minor tree adjustments

6 files changed, 686 insertions, 0 deletions

diff --git a/src/backend-lib/Makefile.am b/src/backend-lib/Makefile.am
new file mode 100644
index 00000000..61867e41
--- /dev/null
+++ b/src/backend-lib/Makefile.am
@@ -0,0 +1,24 @@
+# This Makefile.am is in the public domain
+AM_CPPFLAGS = -I$(top_srcdir)/src/include
+
+lib_LTLIBRARIES = \
+  libtalermerchant.la 
+
+include_HEADERS = \
+  taler_merchant_lib.h \
+  taler_merchant_contract_lib.h
+
+libtalermerchant_la_SOURCES = \
+  taler-merchant-httpd_contract.c \
+  taler_merchant_contract_lib.h \
+  merchant_db.c merchant_db.h \
+  merchant.h
+
+libtalermerchant_la_LIBADD = \
+  $(LIBGCRYPT_LIBS) \
+  -ltalerutil \
+  -lgnunetutil \
+  -ltalerpq \
+  -lgnunetpostgres \
+  -lpq \
+  -lpthread
diff --git a/src/backend-lib/merchant_db.c b/src/backend-lib/merchant_db.c
new file mode 100644
index 00000000..274de25a
--- /dev/null
+++ b/src/backend-lib/merchant_db.c
@@ -0,0 +1,354 @@
+/*
+  This file is part of TALER
+  (C) 2014 Christian Grothoff (and other contributing authors)
+
+  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, If not, see <http://www.gnu.org/licenses/>
+*/
+
+/**
+ * @file merchant/merchant_db.c
+ * @brief database helper functions used by the merchant
+ * @author Sree Harsha Totakura <sreeharsha@totakura.in>
+ */
+
+#include "platform.h"
+#include <gnunet/gnunet_util_lib.h>
+#include <taler/taler_util.h>
+#include <taler/taler_pq_lib.h>
+#include "merchant_db.h"
+
+
+#define PQSQL_strerror(kind, cmd, res)                \
+  GNUNET_log_from (kind, "merchant-db",                     \
+                   "SQL %s failed at %s:%u with error: %s", \
+                   cmd, __FILE__, __LINE__, PQresultErrorMessage (res));
+
+/**
+ * Shorthand for exit jumps.
+ */
+#define EXITIF(cond)                                              \
+  do {                                                            \
+    if (cond) { GNUNET_break (0); goto EXITIF_exit; }             \
+  } while (0)
+
+
+/**
+ * Connect to postgresql database
+ *
+ * @param cfg the configuration handle
+ * @return connection to the postgresql database; NULL upon error
+ */
+PGconn *
+MERCHANT_DB_connect (const struct GNUNET_CONFIGURATION_Handle *cfg)
+{
+  return GNUNET_POSTGRES_connect (cfg, "merchant-db");
+}
+
+
+/**
+ * Disconnect from the database
+ *
+ * @param conn database handle to close
+ */
+void
+MERCHANT_DB_disconnect (PGconn *conn)
+{
+  PQfinish (conn);
+}
+
+
+/**
+ * Initialize merchant tables
+ *
+ * @param conn the connection handle to postgres db.
+ * @param tmp GNUNET_YES if the tables are to be made temporary i.e. their
+ *          contents are dropped when the @a conn is closed
+ * @return GNUNET_OK upon success; GNUNET_SYSERR upon failure
+ */
+int
+MERCHANT_DB_initialize (PGconn *conn, int tmp)
+{
+  const char *tmp_str = (1 == tmp) ? "TEMPORARY" : "";
+  char *sql;
+  PGresult *res;
+  ExecStatusType status;
+  int ret;
+
+  res = NULL;
+  (void) GNUNET_asprintf (&sql,
+                          "BEGIN TRANSACTION;"
+                          "CREATE %1$s TABLE IF NOT EXISTS contracts ("
+                          "contract_id INT8 PRIMARY KEY,"
+                          "amount INT8 NOT NULL,"
+                          "amount_fraction INT4 NOT NULL,"
+			  "amount_currency VARCHAR(" TALER_CURRENCY_LEN_STR ") NOT NULL,"
+                          "description TEXT NOT NULL,"
+                          "nounce INT8 NOT NULL,"
+                          "expiry INT8 NOT NULL,"
+                          "product INT8 NOT NULL);"
+                          "CREATE %1$s TABLE IF NOT EXISTS checkouts ("
+                          "coin_pub BYTEA PRIMARY KEY,"
+                          "contract_id INT8 REFERENCES contracts(contract_id),"
+                          "amount INT4 NOT NULL,"
+                          "amount_fraction INT4 NOT NULL,"
+                          "coin_sig BYTEA NOT NULL);",
+                          tmp_str);
+  ret = GNUNET_POSTGRES_exec (conn, sql);
+  (void) GNUNET_POSTGRES_exec (conn,
+                              (GNUNET_OK == ret) ? "COMMIT;" : "ROLLBACK;");
+  GNUNET_free (sql);
+  if (GNUNET_OK != ret)
+    return ret;
+
+  while (NULL != (res = PQgetResult (conn)))
+  {
+    status = PQresultStatus (res);
+    PQclear (res);
+  }
+
+  EXITIF (NULL == (res = PQprepare
+                   (conn,
+                    "contract_create",
+                    "INSERT INTO contracts"
+                    "(contract_id, amount, amount_fraction, amount_currency,"
+		    "description, nounce, expiry, product) VALUES"
+                    "($1, $2, $3, $4, $5, $6, $7, $8)",
+                    8, NULL)));
+  EXITIF (PGRES_COMMAND_OK != (status = PQresultStatus(res)));
+  PQclear (res);
+
+  EXITIF (NULL == (res = PQprepare
+                   (conn,
+                    "get_contract_product",
+                    "SELECT ("
+                    "product"
+                    ") FROM contracts "
+                    "WHERE ("
+                    "contract_id=$1"
+                    ")",
+                    1, NULL)));
+  EXITIF (PGRES_COMMAND_OK != (status = PQresultStatus(res)));
+  PQclear (res);
+
+  EXITIF (NULL == (res = PQprepare
+                   (conn,
+                    "checkout_create",
+                    "INSERT INTO checkouts ("
+                    "coin_pub,"
+                    "contract_id,"
+                    "amount,"
+                    "amount_fraction,"
+                    "coin_sig"
+                    ") VALUES ("
+                    "$1, $2, $3, $4, $5"
+                    ")",
+                    5, NULL)));
+  EXITIF (PGRES_COMMAND_OK != (status = PQresultStatus (res)));
+  PQclear (res);
+
+  EXITIF (NULL == (res = PQprepare
+                   (conn,
+                    "get_checkout_product",
+                    "SELECT ("
+                    "product"
+                    ") FROM contracts "
+                    "WHERE "
+                    "contract_id IN ("
+                    "SELECT (contract_id) FROM checkouts "
+                    "WHERE coin_pub=$1"
+                    ")",
+                    1, NULL)));
+  EXITIF (PGRES_COMMAND_OK != (status = PQresultStatus (res)));
+  PQclear (res);
+
+  return GNUNET_OK;
+
+ EXITIF_exit:
+  if (NULL != res)
+  {
+    PQSQL_strerror (GNUNET_ERROR_TYPE_ERROR, "PQprepare", res);
+    PQclear (res);
+  }
+  return GNUNET_SYSERR;
+}
+
+
+/**
+ * Inserts a contract record into the database and if successfull returns the
+ * serial number of the inserted row.
+ *
+ * @param conn the database connection
+ * @param expiry the time when the contract will expire
+ * @param amount the taler amount corresponding to the contract
+ * @param c_id contract's id
+ * @param desc descripition of the contract
+ * @param nounce a random 64-bit nounce
+ * @param product description to identify a product
+ * @return GNUNET_OK on success, GNUNET_SYSERR upon error
+ */
+
+uint32_t
+MERCHANT_DB_contract_create (PGconn *conn,
+                             const struct GNUNET_TIME_Absolute *expiry,
+                             const struct TALER_Amount *amount,
+			     uint64_t c_id,
+                             const char *desc,
+                             uint64_t nounce,
+                             uint64_t product)
+{
+  PGresult *res;
+  #if 0
+  uint64_t expiry_ms_nbo;
+  uint64_t value_nbo;
+  uint32_t fraction_nbo;
+  uint64_t nounce_nbo;
+  #endif
+  ExecStatusType status;
+
+  #if 0
+  /*
+  NOTE: the conversion to nl(l) happens *inside* the query param helpers; since
+  the policy imposes this format for storing values. */
+  value_nbo = GNUNET_htonll (amount->value);
+  fraction_nbo = GNUNET_htonll (amount->fraction);
+  nounce_nbo = GNUNET_htonll (nounce);
+  expiry_ms_nbo = GNUNET_htonll (expiry.abs_value_us);
+  product = GNUNET_htonll (product);
+  #endif
+
+  /* ported. To be tested/compiled */
+  struct TALER_PQ_QueryParam params[] = {
+    TALER_PQ_query_param_uint64 (&c_id), 
+    TALER_PQ_query_param_amount (amount),
+    /* a *string* is being put in the following statement,
+    though the API talks about a *blob*. Will this be liked by
+    the DB ? */
+    // the following inserts a string as a blob. Will Taler provide a param-from-string helper?
+    TALER_PQ_query_param_fixed_size (desc, strlen(desc)),
+    TALER_PQ_query_param_uint64 (&nounce), 
+    TALER_PQ_query_param_absolute_time (expiry),
+    TALER_PQ_query_param_uint64 (&product),
+    TALER_PQ_query_param_end
+  };
+  
+  /* NOTE: the statement is prepared by MERCHANT_DB_initialize function */
+  res = TALER_PQ_exec_prepared (conn, "contract_create", params);
+  status = PQresultStatus (res);
+  EXITIF (PGRES_COMMAND_OK != status);
+  PQclear (res);
+  return GNUNET_OK;
+
+ EXITIF_exit:
+  PQclear (res);
+  return GNUNET_SYSERR;
+}
+
+long long
+MERCHANT_DB_get_contract_product (PGconn *conn,
+                                  uint64_t contract_id)
+{
+  PGresult *res;
+  uint64_t product;
+  ExecStatusType status;
+  struct TALER_PQ_QueryParam params[] = {
+    TALER_PQ_query_param_uint64 (&contract_id),
+    TALER_PQ_query_param_end
+  };
+  struct TALER_PQ_ResultSpec rs[] = {
+    TALER_PQ_result_spec_uint64 ("product", &product),
+    TALER_PQ_result_spec_end
+  };
+
+  contract_id = GNUNET_htonll (contract_id);
+  res = TALER_PQ_exec_prepared (conn, "get_contract_product", params);
+  status = PQresultStatus (res);
+  EXITIF (PGRES_TUPLES_OK != status);
+  EXITIF (1 != PQntuples (res));
+  EXITIF (GNUNET_YES != TALER_PQ_extract_result (res, rs, 0));
+  PQclear (res);
+  return GNUNET_ntohll ((uint64_t) product);
+
+ EXITIF_exit:
+  PQclear (res);
+  return -1;
+}
+
+unsigned int
+MERCHANT_DB_checkout_create (PGconn *conn,
+                             struct GNUNET_CRYPTO_rsa_PublicKey *coin_pub,
+                             uint64_t transaction_id,
+                             struct TALER_Amount *amount,
+                             struct GNUNET_CRYPTO_rsa_Signature *coin_sig)
+{
+  PGresult *res;
+  ExecStatusType status;
+  uint32_t value_nbo;
+  uint32_t fraction_nbo;
+  struct TALER_PQ_QueryParam params[] = {
+    TALER_PQ_query_param_rsa_public_key (coin_pub),
+    TALER_PQ_query_param_uint64 (&transaction_id),
+    TALER_PQ_query_param_uint32 (&value_nbo),
+    TALER_PQ_query_param_uint32 (&fraction_nbo),
+    TALER_PQ_query_param_rsa_signature (coin_sig),
+    TALER_PQ_query_param_end
+  };
+
+  transaction_id = GNUNET_htonll (transaction_id);
+  value_nbo = htonl (amount->value);
+  fraction_nbo = htonl (amount->fraction);
+  res = TALER_PQ_exec_prepared (conn, "checkout_create", params);
+  status = PQresultStatus (res);
+  EXITIF (PGRES_COMMAND_OK != status);
+  PQclear (res);
+  return GNUNET_OK;
+
+ EXITIF_exit:
+  PQclear (res);
+  return GNUNET_SYSERR;
+}
+
+
+long long
+MERCHANT_DB_get_checkout_product (PGconn *conn,
+                                  struct GNUNET_CRYPTO_rsa_PublicKey *coin_pub)
+{
+  PGresult *res;
+  ExecStatusType status;
+  uint64_t product;
+  struct TALER_PQ_QueryParam params[] = {
+    TALER_PQ_query_param_rsa_public_key (coin_pub),
+    TALER_PQ_query_param_end
+  };
+  struct TALER_PQ_ResultSpec rs[] = {
+    TALER_PQ_result_spec_uint64 ("product", &product),
+    TALER_PQ_result_spec_end
+  };
+
+  product = -1;
+  res = TALER_PQ_exec_prepared (conn, "get_checkout_product", params);
+  status = PQresultStatus (res);
+  EXITIF (PGRES_TUPLES_OK != status);
+  if (0 == PQntuples (res))
+  {
+    TALER_LOG_DEBUG ("Checkout not found for given coin");
+    goto EXITIF_exit;
+  }
+  EXITIF (1 != PQntuples (res));
+  EXITIF (GNUNET_YES != TALER_PQ_extract_result (res, rs, 0));
+  PQclear (res);
+  return GNUNET_ntohll ((uint64_t) product);
+
+ EXITIF_exit:
+  PQclear (res);
+  return -1;
+}
+/* end of merchant-db.c */
diff --git a/src/backend-lib/merchant_db.h b/src/backend-lib/merchant_db.h
new file mode 100644
index 00000000..a723b229
--- /dev/null
+++ b/src/backend-lib/merchant_db.h
@@ -0,0 +1,101 @@
+/*
+  This file is part of TALER
+  (C) 2014 Christian Grothoff (and other contributing authors)
+
+  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, If not, see <http://www.gnu.org/licenses/>
+*/
+
+/**
+ * @file merchant/merchant_db.h
+ * @brief database helper functions used by the merchant
+ * @author Sree Harsha Totakura <sreeharsha@totakura.in>
+ */
+
+#ifndef MERCHANT_DB_H
+#define MERCHANT_DB_H
+
+#include <gnunet/gnunet_postgres_lib.h>
+#include <taler/taler_util.h>
+
+/**
+ * Connect to postgresql database
+ *
+ * @param cfg the configuration handle
+ * @return connection to the postgresql database; NULL upon error
+ */
+PGconn *
+MERCHANT_DB_connect (const struct GNUNET_CONFIGURATION_Handle *cfg);
+
+
+/**
+ * Disconnect from the database
+ *
+ * @param conn database handle to close
+ */
+void
+MERCHANT_DB_disconnect (PGconn *conn);
+
+
+/**
+ * Initialize merchant tables
+ *
+ * @param conn the connection handle to postgres db.
+ * @param tmp GNUNET_YES if the tables are to be made temporary i.e. their
+ *          contents are dropped when the @a conn is closed
+ * @return GNUNET_OK upon success; GNUNET_SYSERR upon failure
+ */
+int
+MERCHANT_DB_initialize (PGconn *conn, int tmp);
+
+
+/**
+ * Inserts a contract record into the database and if successfull returns the
+ * serial number of the inserted row.
+ *
+ * @param conn the database connection
+ * @param expiry the time when the contract will expire
+ * @param amount the taler amount corresponding to the contract
+ * @param c_id this contract's identification number
+ * @param desc descripition of the contract
+ * @param nounce a random 64-bit nounce
+ * @param product description to identify a product
+ * @return GNUNET_OK on success, GNUNET_SYSERR upon error
+ */
+
+uint32_t
+MERCHANT_DB_contract_create (PGconn *conn,
+                             const struct GNUNET_TIME_Absolute *expiry,
+                             const struct TALER_Amount *amount,
+			     uint64_t c_id,
+                             const char *desc,
+                             uint64_t nounce,
+                             uint64_t product);
+
+long long
+MERCHANT_DB_get_contract_product (PGconn *conn,
+                                  uint64_t contract_id);
+
+unsigned int
+MERCHANT_DB_checkout_create (PGconn *conn,
+                             struct GNUNET_CRYPTO_rsa_PublicKey *coin_pub,
+                             uint64_t transaction_id,
+                             struct TALER_Amount *amount,
+                             struct GNUNET_CRYPTO_rsa_Signature *coin_sig);
+
+
+long long
+MERCHANT_DB_get_checkout_product (PGconn *conn,
+                                  struct GNUNET_CRYPTO_rsa_PublicKey *coin_pub);
+
+#endif  /* MERCHANT_DB_H */
+
+/* end of merchant-db.h */
diff --git a/src/backend-lib/taler-merchant-httpd_contract.c b/src/backend-lib/taler-merchant-httpd_contract.c
new file mode 100644
index 00000000..55c56e0a
--- /dev/null
+++ b/src/backend-lib/taler-merchant-httpd_contract.c
@@ -0,0 +1,144 @@
+#include "platform.h"
+#include <jansson.h>
+#include <taler/taler_signatures.h>
+#include <gnunet/gnunet_util_lib.h>
+#include "merchant.h"
+#include "merchant_db.h"
+#include "taler_merchant_contract_lib.h"
+
+
+/* TODO: make this file a library, and programmatically call the following
+ * functions */
+
+/**
+ * Macro to round microseconds to seconds in GNUNET_TIME_* structs.
+ */
+#define ROUND_TO_SECS(name,us_field) name.us_field -= name.us_field % (1000 * 1000)
+
+/**
+ * Shorthand for exit jumps.
+ */
+#define EXITIF(cond)                                              \
+  do {                                                            \
+    if (cond) { GNUNET_break (0); goto EXITIF_exit; }             \
+  } while (0)
+
+/**
+* Generate the hash containing the information (= a nounce + merchant's IBAN) to
+* redeem money from mint in a subsequent /deposit operation
+* @param nounce the nounce
+* @param wire the merchant's wire details
+* @return the hash to be included in the contract's blob
+*
+*/
+
+static struct GNUNET_HashCode
+hash_wireformat (uint64_t nounce, const struct MERCHANT_WIREFORMAT_Sepa *wire)
+{
+  struct GNUNET_HashContext *hc;
+  struct GNUNET_HashCode hash;
+
+  hc = GNUNET_CRYPTO_hash_context_start ();
+  GNUNET_CRYPTO_hash_context_read (hc, wire->iban, strlen (wire->iban));
+  GNUNET_CRYPTO_hash_context_read (hc, wire->name, strlen (wire->name));
+  GNUNET_CRYPTO_hash_context_read (hc, wire->bic, strlen (wire->bic));
+  nounce = GNUNET_htonll (nounce);
+  GNUNET_CRYPTO_hash_context_read (hc, &nounce, sizeof (nounce));
+  GNUNET_CRYPTO_hash_context_finish (hc, &hash);
+  return hash;
+}
+
+/**
+* Take from the frontend the (partly) generated contract and fill
+* the missing values in it; for example, the SEPA-aware values.
+* Moreover, it stores the contract in the DB and does the signature of it.
+* @param contract parsed contract, originated by the frontend
+* @param db_conn the handle to the local DB
+* @param kpriv merchant's private key
+* @param wire merchant's bank's details
+* @param sig where to store the signature
+* @return pointer to the complete JSON; NULL upon errors
+*/
+
+/* TODO: this handles a simplified version (for debugging purposes)
+         of the contract. To expand to the full fledged version */
+
+json_t *
+MERCHANT_handle_contract (json_t *contract,
+                          PGconn *db_conn,
+                          struct GNUNET_CRYPTO_EddsaPrivateKey *kpriv,
+                          const struct MERCHANT_WIREFORMAT_Sepa *wire,
+			  struct GNUNET_CRYPTO_EddsaSignature *sig)
+{
+  json_t *root;
+  json_t *j_timestamp;
+  json_t *jh_wire;
+  json_t *j_amount;
+  json_int_t j_trans_id;
+
+  uint64_t nounce;
+  uint64_t product_id;
+  char *a;
+  char *h_wire_enc;
+  char *str;
+  struct GNUNET_HashCode h_wire;
+  struct GNUNET_TIME_Absolute timestamp;
+  struct TALER_Amount amount;
+  struct TALER_AmountNBO amount_nbo;
+  struct ContractNBO contract_nbo;
+
+  nounce = GNUNET_CRYPTO_random_u64 (GNUNET_CRYPTO_QUALITY_NONCE, UINT64_MAX);
+  // timing mgmt
+  timestamp = GNUNET_TIME_absolute_add (GNUNET_TIME_absolute_get (),
+                                     GNUNET_TIME_UNIT_DAYS);
+  ROUND_TO_SECS (timestamp, abs_value_us);
+  j_timestamp = TALER_json_from_abs (timestamp);
+
+  // wireformat mgmt
+  h_wire = hash_wireformat (nounce, wire);
+  h_wire_enc = GNUNET_STRINGS_data_to_string_alloc (&h_wire,
+                                                    sizeof (struct GNUNET_HashCode));
+
+  jh_wire = json_string (h_wire_enc);
+
+  str = json_dumps (contract, JSON_INDENT(2) | JSON_PRESERVE_ORDER);
+
+
+  json_unpack (contract, "{s:o, s:I}",
+               "amount", &j_amount,
+	       "trans_id", &j_trans_id);
+
+  /* needed for DB stuff */
+  TALER_json_to_amount (j_amount, &amount);
+  /* temporary way of getting this value. To be adapted to the expanded contract
+  format. See 'TODO' above. */
+  product_id = GNUNET_CRYPTO_random_u64 (GNUNET_CRYPTO_QUALITY_NONCE, UINT64_MAX);
+  /* adding the generated values in this JSON */
+  root = json_pack ("{s:o, s:I, s:s, s:o}",
+             "amount", j_amount,
+	     "trans_id", j_trans_id,
+	     "h_wire", jh_wire,
+	     "timestamp", j_timestamp);
+  a = json_dumps (root, JSON_COMPACT | JSON_PRESERVE_ORDER);
+
+  // DB mgmt
+  if (GNUNET_SYSERR == MERCHANT_DB_contract_create (db_conn,
+                                                    &timestamp,
+                                                    &amount,
+ 					            (uint64_t) j_trans_id, // safe?
+                                                    a,
+                                                    nounce,
+                                                    product_id));
+  contract_nbo.h_wire = h_wire;
+  TALER_amount_hton (&amount_nbo, &amount);
+  contract_nbo.amount = amount_nbo;
+  contract_nbo.t = GNUNET_TIME_absolute_hton (timestamp);
+  contract_nbo.m = GNUNET_htonll ((uint64_t) j_trans_id); // safe?
+  GNUNET_CRYPTO_hash (a, strlen (a) + 1, &contract_nbo.h_contract_details);
+  free (a);
+  contract_nbo.purpose.purpose = htonl (TALER_SIGNATURE_MERCHANT_CONTRACT);
+  contract_nbo.purpose.size = htonl (sizeof (struct ContractNBO));
+  GNUNET_CRYPTO_eddsa_sign (kpriv, &contract_nbo.purpose, sig);
+
+  return root;
+}
diff --git a/src/backend-lib/taler_merchant_contract_lib.h b/src/backend-lib/taler_merchant_contract_lib.h
new file mode 100644
index 00000000..4e345703
--- /dev/null
+++ b/src/backend-lib/taler_merchant_contract_lib.h
@@ -0,0 +1,62 @@
+
+GNUNET_NETWORK_STRUCT_BEGIN
+
+struct ContractNBO
+{
+  /**
+   * Purpose header for the signature over contract
+   */
+  struct GNUNET_CRYPTO_EccSignaturePurpose purpose;
+
+  /**
+   * The transaction identifier. NOTE: it was m[13]. TODO:
+   * change the API accordingly!
+   */
+  uint64_t m;
+
+  /**
+   * Expiry time
+   */
+  struct GNUNET_TIME_AbsoluteNBO t;
+
+  /**
+   * The invoice amount
+   */
+  struct TALER_AmountNBO amount;
+
+  /**
+   * The hash of the merchant's wire details (bank account information), with a nounce
+   */
+  struct GNUNET_HashCode h_wire;
+
+  /**
+   * Hash of the JSON contract in UTF-8 including 0-termination,
+   * using JSON_COMPACT encoding with sorted fields.
+   */
+  struct GNUNET_HashCode h_contract_details;
+
+};
+
+GNUNET_NETWORK_STRUCT_END
+
+/**
+* Take from the frontend the (partly) generated contract and fill
+* the missing values in it; for example, the SEPA-aware values.
+* Moreover, it stores the contract in the DB and does the signature of it.
+* @param contract parsed contract, originated by the frontend
+* @param db_conn the handle to the local DB
+* @param kpriv merchant's private key
+* @param wire merchant's bank's details
+* @param sig where to store the signature
+* @return pointer to the complete JSON; NULL upon errors
+*/
+
+/* TODO: this handles a simplified version (for debugging purposes)
+         of the contract. To expand to the full fledged version */
+
+json_t *
+MERCHANT_handle_contract (json_t *contract,
+                          PGconn *db_conn,
+			  struct GNUNET_CRYPTO_EddsaPrivateKey *kpriv,
+                          const struct MERCHANT_WIREFORMAT_Sepa *wire,
+                          struct GNUNET_CRYPTO_EddsaSignature *sig);
diff --git a/src/backend-lib/taler_merchant_lib.h b/src/backend-lib/taler_merchant_lib.h
new file mode 100644
index 00000000..41891783
--- /dev/null
+++ b/src/backend-lib/taler_merchant_lib.h
@@ -0,0 +1 @@
+#include "taler_merchant_contract_lib.h"