[age restriction] progress 10/n

More work towards support for extensions:
- Prepared statements and DB-plugin-functions for setting and retrieving
  configurations from the database added.
- primitive "registry" of extensions for age restrictions and peer2peer
  (stub)
- TALER_Extensions now with FP for parsing, setting and converting a
  configuration.
- /management/extensions handler now verifies signature of the (opaque)
  json object for all extensions.
- /management/extensions handler calls the FP in the corrensponding
  TALER_Extension for parsing and setting the configuration of a
  particular extension

More work towards age restriction:
- TALER_Extensions interfaces for config-parser, -setter and converter
  implemented for age restriction
- DB event handler now retrieves config from database, parses it and
  sets it (the age mask) in the global extension.
- load_age_mask now loads age mask from the global extension (and not
  from the config file)
- add age_restricted_denoms to /keys response

4 files changed, 68 insertions, 43 deletions

diff --git a/src/util/Makefile.am b/src/util/Makefile.am
index cae1a205e..55ebb4dff 100644
--- a/src/util/Makefile.am
+++ b/src/util/Makefile.am
@@ -72,6 +72,7 @@ libtalerutil_la_SOURCES = \
   crypto_wire.c \
   denom.c \
   exchange_signatures.c \
+  extensions.c \
   extension_age_restriction.c \
   getopt.c \
   lang.c \
diff --git a/src/util/extension_age_restriction.c b/src/util/extension_age_restriction.c
index c0efd7cd1..42a58b2e9 100644
--- a/src/util/extension_age_restriction.c
+++ b/src/util/extension_age_restriction.c
@@ -23,7 +23,6 @@
 #include "taler_extensions.h"
 #include "stdint.h"
 
-
 /**
  *
  * @param cfg Handle to the GNUNET configuration
@@ -137,12 +136,14 @@ TALER_parse_age_group_string (char *groups,
 
 
 /**
+ * Encodes the age mask into a string, like "8:10:12:14:16:18:21"
+ *
  * @param mask Age mask
  * @return String representation of the age mask, allocated by GNUNET_malloc.
  *         Can be used as value in the TALER config.
  */
 char *
-TALER_age_mask_to_string (struct TALER_AgeMask *m)
+TALER_age_mask_to_string (const struct TALER_AgeMask *m)
 {
   uint32_t mask = m->mask;
   unsigned int n = 0;
diff --git a/src/util/extensions.c b/src/util/extensions.c
new file mode 100644
index 000000000..87dd16b4d
--- /dev/null
+++ b/src/util/extensions.c
@@ -0,0 +1,49 @@
+/*
+   This file is part of TALER
+   Copyright (C) 2014-2021 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 extensions.c
+ * @brief Utility functions for extensions
+ * @author Özgür Kesim
+ */
+#include "platform.h"
+#include "taler_util.h"
+#include "taler_extensions.h"
+#include "stdint.h"
+
+enum GNUNET_GenericReturnValue
+TALER_extension_get_by_name (const char *name,
+                             const struct TALER_Extension **extensions,
+                             const struct TALER_Extension **ext)
+{
+
+  const struct TALER_Extension *it = *extensions;
+
+  for (; NULL != it; it++)
+  {
+    if (0 == strncmp (name,
+                      it->name,
+                      strlen (it->name)))
+    {
+      *ext = it;
+      return GNUNET_OK;
+    }
+  }
+
+  return GNUNET_NO;
+}
+
+
+/* end of extensions.c */
diff --git a/src/util/offline_signatures.c b/src/util/offline_signatures.c
index 7fbec826b..1240a8bc5 100644
--- a/src/util/offline_signatures.c
+++ b/src/util/offline_signatures.c
@@ -491,66 +491,40 @@ TALER_exchange_offline_wire_fee_verify (
 
 
 void
-TALER_exchange_offline_extension_agemask_sign (
-  const struct TALER_AgeMask mask,
+TALER_exchange_offline_extension_config_hash_sign (
+  const struct TALER_ExtensionConfigHash h_config,
   const struct TALER_MasterPrivateKeyP *master_priv,
   struct TALER_MasterSignatureP *master_sig)
 {
-  struct TALER_MasterExtensionAgeRestrictionPS ar = {
+  struct TALER_MasterExtensionConfigurationPS ec = {
     .purpose.purpose = htonl (TALER_SIGNATURE_MASTER_EXTENSION),
-    .purpose.size = htonl (sizeof(ar)),
-    .mask = mask
+    .purpose.size = htonl (sizeof(ec)),
+    .h_config = h_config
   };
   GNUNET_CRYPTO_eddsa_sign (&master_priv->eddsa_priv,
-                            &ar,
+                            &ec,
                             &master_sig->eddsa_signature);
 }
 
 
 enum GNUNET_GenericReturnValue
-TALER_exchange_offline_extension_agemask_verify (
-  const struct TALER_AgeMask mask,
+TALER_exchange_offline_extension_config_hash_verify (
+  const struct TALER_ExtensionConfigHash h_config,
   const struct TALER_MasterPublicKeyP *master_pub,
   const struct TALER_MasterSignatureP *master_sig
   )
 {
-  struct TALER_MasterExtensionAgeRestrictionPS ar = {
+  struct TALER_MasterExtensionConfigurationPS ec = {
     .purpose.purpose = htonl (TALER_SIGNATURE_MASTER_EXTENSION),
-    .purpose.size = htonl (sizeof(ar)),
-    .mask = mask
+    .purpose.size = htonl (sizeof(ec)),
+    .h_config = h_config
   };
-  return
-    GNUNET_CRYPTO_eddsa_verify (TALER_SIGNATURE_MASTER_EXTENSION,
-                                &ar,
-                                &master_sig->eddsa_signature,
-                                &master_pub->eddsa_pub);
-}
-
 
-#if 0
-/* TODO peer2peer */
-void
-TALER_exchange_offline_extension_p2p_sign (
-  // TODO
-  const struct TALER_MasterPrivateKeyP *master_priv,
-  struct TALER_MasterSignatureP *master_sig)
-{
-  // TODO
-}
-
-
-enum GNUNET_GenericReturnValue
-TALER_exchange_offline_extension_p2p_verify (
-  // TODO
-  const struct TALER_MasterPublicKeyP *master_pub,
-  const struct TALER_MasterSignatureP *master_sig,
-  )
-{
-  // TODO
-  return GNUNET_FALSE;
+  return GNUNET_CRYPTO_eddsa_verify (TALER_SIGNATURE_MASTER_EXTENSION,
+                                     &ec,
+                                     &master_sig->eddsa_signature,
+                                     &master_pub->eddsa_pub);
 }
 
 
-#endif
-
 /* end of offline_signatures.c */