Changing configuration structure to enable multiple accounts.

This change enables using multiple wire plugins at the same time.
Also, we now distinguish between the wire plugin (i.e. EBICS or
taler_bank) and the wire method (i.e. SEPA or x-taler-bank) that
the wire plugin is implementing.  The "taler-bank" wire method
was renamed from "test" to "x-taler-bank".

This also changes the format of the /wire response of the exchange,
as we now need to return multiple accounts.  Note that wire fees
are specified per wire method, not per wire account.

taler-exchange-keyup now automatically signs all of the /wire
responses in the location specified by the configuration.

Account identification in wire plugins was changed to use
payto://-URLs instead of method-specific JSON fields.  Signing
and validation of /wire responses was moved from each wire
plugin to a generic validation method in libtalerutil (crypto)
or libtalerjson (for JSON-formatted inputs).
Convenience methods were added to generate JSON for wire accounts
(salting, signing).

Various section and option names were adjusted to streamline the
configuration and make it more consistent overall.  Documentation
was updated as well.

1 files changed, 345 insertions, 0 deletions

diff --git a/src/wire-plugins/plugin_wire_template.c b/src/wire-plugins/plugin_wire_template.c
new file mode 100644
index 000000000..6fadb88ce
--- /dev/null
+++ b/src/wire-plugins/plugin_wire_template.c
@@ -0,0 +1,345 @@
+/*
+  This file is part of TALER
+  Copyright (C) 2016, 2018 GNUnet e.V.
+
+  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 plugin_wire_template.c
+ * @brief template for wire plugins; replace "template" with real plugin name!
+ * @author Florian Dold
+ * @author Christian Grothoff
+ * @author Sree Harsha Totakura
+ */
+#include "platform.h"
+#include "taler_wire_plugin.h"
+
+
+/**
+ * Type of the "cls" argument given to each of the functions in
+ * our API.
+ */
+struct TemplateClosure
+{
+
+  /**
+   * Which currency do we support?
+   */
+  char *currency;
+
+  /**
+   * Which configuration do we use to lookup accounts?
+   */
+  struct GNUNET_CONFIGURATION_Handle *cfg;
+
+};
+
+
+/**
+ * Round amount DOWN to the amount that can be transferred via the wire
+ * method.  For example, Taler may support 0.000001 EUR as a unit of
+ * payment, but SEPA only supports 0.01 EUR.  This function would
+ * round 0.125 EUR to 0.12 EUR in this case.
+ *
+ * @param cls the @e cls of this struct with the plugin-specific state
+ * @param[in,out] amount amount to round down
+ * @return #GNUNET_OK on success, #GNUNET_NO if rounding was unnecessary,
+ *         #GNUNET_SYSERR if the amount or currency was invalid
+ */
+static int
+template_amount_round (void *cls,
+                       struct TALER_Amount *amount)
+{
+  struct TemplateClosure *tc = cls;
+
+  if (0 != strcasecmp (amount->currency,
+                       tc->currency))
+  {
+    GNUNET_break (0);
+    return GNUNET_SYSERR;
+  }
+  GNUNET_break (0); // not implemented
+  return GNUNET_SYSERR;
+}
+
+
+/**
+ * Check if the given payto:// URL is correctly formatted for this plugin
+ *
+ * @param cls the @e cls of this struct with the plugin-specific state
+ * @param account_url the payto:// URL
+ * @return #TALER_EC_NONE if correctly formatted
+ */
+static enum TALER_ErrorCode
+template_wire_validate (void *cls,
+                        const char *account_url)
+{
+  GNUNET_break (0);
+  return TALER_EC_NOT_IMPLEMENTED;
+}
+
+
+/**
+ * Prepare for exeuction of a wire transfer.
+ *
+ * @param cls the @e cls of this struct with the plugin-specific state
+ * @param origin_account_section configuration section specifying the origin
+ *        account of the exchange to use
+ * @param destination_account_url payto:// URL identifying where to send the money
+ * @param amount amount to transfer, already rounded
+ * @param exchange_base_url base URL of the exchange (for tracking)
+ * @param wtid wire transfer identifier to use
+ * @param ptc function to call with the prepared data to persist
+ * @param ptc_cls closure for @a ptc
+ * @return NULL on failure
+ */
+static struct TALER_WIRE_PrepareHandle *
+template_prepare_wire_transfer (void *cls,
+                                const char *origin_account_section,
+                                const char *destination_account_url,
+                                const struct TALER_Amount *amount,
+                                const char *exchange_base_url,
+                                const struct TALER_WireTransferIdentifierRawP *wtid,
+                                TALER_WIRE_PrepareTransactionCallback ptc,
+                                void *ptc_cls)
+{
+  GNUNET_break (0);
+  return NULL;
+}
+
+
+/**
+ * Abort preparation of a wire transfer. For example,
+ * because we are shutting down.
+ *
+ * @param cls the @e cls of this struct with the plugin-specific state
+ * @param pth preparation to cancel
+ */
+static void
+template_prepare_wire_transfer_cancel (void *cls,
+                                       struct TALER_WIRE_PrepareHandle *pth)
+{
+  GNUNET_break (0);
+}
+
+
+/**
+ * Execute a wire transfer.
+ *
+ * @param cls the @e cls of this struct with the plugin-specific state
+ * @param buf buffer with the prepared execution details
+ * @param buf_size number of bytes in @a buf
+ * @param cc function to call upon success
+ * @param cc_cls closure for @a cc
+ * @return NULL on error
+ */
+static struct TALER_WIRE_ExecuteHandle *
+template_execute_wire_transfer (void *cls,
+                                const char *buf,
+                                size_t buf_size,
+                                TALER_WIRE_ConfirmationCallback cc,
+                                void *cc_cls)
+{
+  GNUNET_break (0);
+  return NULL;
+}
+
+
+/**
+ * Abort execution of a wire transfer. For example, because we are
+ * shutting down.  Note that if an execution is aborted, it may or
+ * may not still succeed. The caller MUST run @e
+ * execute_wire_transfer again for the same request as soon as
+ * possilbe, to ensure that the request either ultimately succeeds
+ * or ultimately fails. Until this has been done, the transaction is
+ * in limbo (i.e. may or may not have been committed).
+ *
+ * @param cls the @e cls of this struct with the plugin-specific state
+ * @param eh execution to cancel
+ */
+static void
+template_execute_wire_transfer_cancel (void *cls,
+                                       struct TALER_WIRE_ExecuteHandle *eh)
+{
+  GNUNET_break (0);
+}
+
+
+/**
+ * Query transfer history of an account.  We use the variable-size
+ * @a start_off to indicate which transfers we are interested in as
+ * different banking systems may have different ways to identify
+ * transfers.  The @a start_off value must thus match the value of
+ * a `row_off` argument previously given to the @a hres_cb.  Use
+ * NULL to query transfers from the beginning of time (with
+ * positive @a num_results) or from the latest committed transfers
+ * (with negative @a num_results).
+ *
+ * @param cls the @e cls of this struct with the plugin-specific state
+ * @param account_section specifies the configuration section which
+ *        identifies the account for which we should get the history
+ * @param direction what kinds of wire transfers should be returned
+ * @param start_off from which row on do we want to get results, use NULL for the latest; exclusive
+ * @param start_off_len number of bytes in @a start_off; must be `sizeof(uint64_t)`.
+ * @param num_results how many results do we want; negative numbers to go into the past,
+ *                    positive numbers to go into the future starting at @a start_row;
+ *                    must not be zero.
+ * @param hres_cb the callback to call with the transaction history
+ * @param hres_cb_cls closure for the above callback
+ */
+static struct TALER_WIRE_HistoryHandle *
+template_get_history (void *cls,
+                      const char *account_section,
+                      enum TALER_BANK_Direction direction,
+                      const void *start_off,
+                      size_t start_off_len,
+                      int64_t num_results,
+                      TALER_WIRE_HistoryResultCallback hres_cb,
+                      void *hres_cb_cls)
+{
+  GNUNET_break (0);
+  return NULL;
+}
+
+
+/**
+ * Cancel going over the account's history.
+ *
+ * @param cls the @e cls of this struct with the plugin-specific state
+ * @param whh operation to cancel
+ */
+static void
+template_get_history_cancel (void *cls,
+			     struct TALER_WIRE_HistoryHandle *whh)
+{
+  GNUNET_break (0);
+}
+
+
+/**
+ * Reject an incoming wire transfer that was obtained from the
+ * history. This function can be used to transfer funds back to
+ * the sender if the WTID was malformed (i.e. due to a typo).
+ *
+ * Calling `reject_transfer` twice on the same wire transfer should
+ * be idempotent, i.e. not cause the funds to be wired back twice.
+ * Furthermore, the transfer should henceforth be removed from the
+ * results returned by @e get_history.
+ *
+ * @param cls plugin's closure
+ * @param account_section specifies the configuration section which
+ *        identifies the account to use to reject the transfer
+ * @param start_off offset of the wire transfer in plugin-specific format
+ * @param start_off_len number of bytes in @a start_off
+ * @param rej_cb function to call with the result of the operation
+ * @param rej_cb_cls closure for @a rej_cb
+ * @return handle to cancel the operation
+ */
+static struct TALER_WIRE_RejectHandle *
+template_reject_transfer (void *cls,
+                          const char *account_section,
+                          const void *start_off,
+                          size_t start_off_len,
+                          TALER_WIRE_RejectTransferCallback rej_cb,
+                          void *rej_cb_cls)
+{
+  GNUNET_break (0);
+  return NULL;
+}
+
+
+/**
+ * Cancel ongoing reject operation.  Note that the rejection may still
+ * proceed. Basically, if this function is called, the rejection may
+ * have happened or not.  This function is usually used during shutdown
+ * or system upgrades.  At a later point, the application must call
+ * @e reject_transfer again for this wire transfer, unless the
+ * @e get_history shows that the wire transfer no longer exists.
+ *
+ * @param cls plugins' closure
+ * @param rh operation to cancel
+ * @return closure of the callback of the operation
+ */
+static void *
+template_reject_transfer_cancel (void *cls,
+                                 struct TALER_WIRE_RejectHandle *rh)
+{
+  GNUNET_break (0);
+  return NULL;
+}
+
+
+/**
+ * Initialize template-wire subsystem.
+ *
+ * @param cls a configuration instance
+ * @return NULL on error, otherwise a `struct TALER_WIRE_Plugin`
+ */
+void *
+libtaler_plugin_wire_template_init (void *cls)
+{
+  struct GNUNET_CONFIGURATION_Handle *cfg = cls;
+  struct TemplateClosure *tc;
+  struct TALER_WIRE_Plugin *plugin;
+
+  tc = GNUNET_new (struct TemplateClosure);
+  tc->cfg = cfg;
+  if (GNUNET_OK !=
+      GNUNET_CONFIGURATION_get_value_string (cfg,
+                                             "taler",
+                                             "CURRENCY",
+                                             &tc->currency))
+  {
+    GNUNET_log_config_missing (GNUNET_ERROR_TYPE_ERROR,
+                               "taler",
+                               "CURRENCY");
+    GNUNET_free (tc);
+    return NULL;
+  }
+
+  plugin = GNUNET_new (struct TALER_WIRE_Plugin);
+  plugin->cls = tc;
+  plugin->method = "FIXME-REPLACE-BY-METHOD";
+  plugin->amount_round = &template_amount_round;
+  plugin->wire_validate = &template_wire_validate;
+  plugin->prepare_wire_transfer = &template_prepare_wire_transfer;
+  plugin->prepare_wire_transfer_cancel = &template_prepare_wire_transfer_cancel;
+  plugin->execute_wire_transfer = &template_execute_wire_transfer;
+  plugin->execute_wire_transfer_cancel = &template_execute_wire_transfer_cancel;
+  plugin->get_history = &template_get_history;
+  plugin->get_history_cancel = &template_get_history_cancel;
+  plugin->reject_transfer = &template_reject_transfer;
+  plugin->reject_transfer_cancel = &template_reject_transfer_cancel;
+  return plugin;
+}
+
+
+/**
+ * Shutdown Template wire subsystem.
+ *
+ * @param cls a `struct TALER_WIRE_Plugin`
+ * @return NULL (always)
+ */
+void *
+libtaler_plugin_wire_template_done (void *cls)
+{
+  struct TALER_WIRE_Plugin *plugin = cls;
+  struct TemplateClosure *tc = plugin->cls;
+
+  GNUNET_free (tc->currency);
+  GNUNET_free (tc);
+  GNUNET_free (plugin);
+  return NULL;
+}
+
+/* end of plugin_wire_template.c */