Logic for extensions more generic

- signature of the hash of the json will be checked
- config_verify for signature check of any extension
- FP for parsing the config as and converting to JSON
- simplify TEH_handler_management_post_extensions
- cleanups

src/exchange/taler-exchange-httpd.c

@@ -1,18 +1,18 @@
 /*
-  This file is part of TALER
+   This file is part of TALER
-  Copyright (C) 2014-2021 Taler Systems SA
+   Copyright (C) 2014-2021 Taler Systems SA
 
-  TALER is free software; you can redistribute it and/or modify it under the
+   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
+   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.
+   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
+   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
+   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
-  A PARTICULAR PURPOSE.  See the GNU Affero General Public License for more details.
+   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
+   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/>
+   TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
-*/
+ */
 /**
  * @file taler-exchange-httpd.c
  * @brief Serve the HTTP interface of the exchange
@@ -150,19 +150,33 @@ bool TEH_suicide;
 /**
  * The global manifest with the list supported extensions, sorted by
  * TALER_Extension_Type.
+ *
+ * TODO: This needs to become a dynamic list, once we have a model for
+ * extensions as plugins.
  **/
-const struct TALER_Extension TEH_extensions[TALER_Extension_Max] = {
+const struct TALER_Extension TEH_extensions[] = {
+  [TALER_Extension_AgeRestriction] = {
+    .type = TALER_Extension_AgeRestriction,
+    .name = "age_restriction",
+    .critical = false,
+    .config = NULL, // disabled per default
+    /* TODO:
+    .parse_config = &TALER_Extension_AgeRestriction_parse_config,
+    .config_to_json = &TALER_Extension_AgeRestriction_config_to_json,
+    */
+  },
   [TALER_Extension_Peer2Peer] = {
     .type = TALER_Extension_Peer2Peer,
     .name = "peer2peer",
     .critical = false,
     .config = NULL, // disabled per default
   },
-  [TALER_Extension_AgeRestriction] = {
+  /* terminator */
-    .type = TALER_Extension_AgeRestriction,
+  [TALER_Extension_Max] = {
-    .name = "age_restriction",
+    .type = TALER_Extension_Max,
+    .name = NULL,
     .critical = false,
-    .config = NULL, // disabled per default
+    .config = NULL,
   },
 };
 
@@ -485,7 +499,7 @@ proceed_with_handler (struct TEH_RequestContext *rc,
     if (GNUNET_SYSERR == res)
     {
       GNUNET_assert (NULL == root);
-      return MHD_NO;  /* bad upload, could not even generate error */
+      return MHD_NO; /* bad upload, could not even generate error */
     }
     if ( (GNUNET_NO == res) ||
          (NULL == root) )
@@ -528,8 +542,8 @@ proceed_with_handler (struct TEH_RequestContext *rc,
                          sizeof (emsg),
                          "Got %u/%u segments for %s request ('%s')",
                          (NULL == args[i - 1])
-                         ? i - 1
+       ? i - 1
-                         : i + ((NULL != fin) ? 1 : 0),
+       : i + ((NULL != fin) ? 1 : 0),
                          rh->nargs,
                          rh->url,
                          url);
@@ -553,7 +567,7 @@ proceed_with_handler (struct TEH_RequestContext *rc,
                               root,
                               args);
     else /* We also only have "POST" or "GET" in the API for at this point
-            (OPTIONS/HEAD are taken care of earlier) */
+      (OPTIONS/HEAD are taken care of earlier) */
       ret = rh->handler.get (rc,
                              args);
   }
@@ -1120,7 +1134,7 @@ handle_mhd_request (void *cls,
 
   if (0 == strcasecmp (method,
                        MHD_HTTP_METHOD_HEAD))
-    method = MHD_HTTP_METHOD_GET;   /* treat HEAD as GET here, MHD will do the rest */
+    method = MHD_HTTP_METHOD_GET; /* treat HEAD as GET here, MHD will do the rest */
 
   /* parse first part of URL */
   {
@@ -1954,8 +1968,8 @@ run (void *cls,
                           MHD_OPTION_CONNECTION_TIMEOUT,
                           connection_timeout,
                           (0 == allow_address_reuse)
-                          ? MHD_OPTION_END
+                    ? MHD_OPTION_END
-                          : MHD_OPTION_LISTENING_ADDRESS_REUSE,
+                    : MHD_OPTION_LISTENING_ADDRESS_REUSE,
                           (unsigned int) allow_address_reuse,
                           MHD_OPTION_END);
   if (NULL == mhd)

src/exchange/taler-exchange-httpd.h

@@ -202,9 +202,9 @@ extern volatile bool MHD_terminating;
 extern struct GNUNET_CURL_Context *TEH_curl_ctx;
 
 /**
- * The manifest of the available extensions
+ * The manifest of the available extensions, NULL terminated
  */
-extern const struct TALER_Extension TEH_extensions[TALER_Extension_Max];
+extern const struct TALER_Extension TEH_extensions[];
 
 /**
  * @brief Struct describing an URL and the handler for it.

src/exchange/taler-exchange-httpd_management_extensions.c

@@ -32,19 +32,14 @@
 #include "taler_dbevents.h"
 
 
+/**
+ * Extension carries the necessary data for a particular extension.
+ *
+ */
 struct Extension
 {
   enum TALER_Extension_Type type;
-  json_t *config_json;
+  json_t *config;
-
-  // This union contains the parsed configuration for each extension.
-  union
-  {
-    // configuration for the age restriction
-    struct TALER_AgeMask mask;
-
-    /* TODO oec - add peer2peer config */
-  };
 };
 
 /**
@@ -57,6 +52,38 @@ struct SetExtensionsContext
   struct TALER_MasterSignatureP *extensions_sigs;
 };
 
+
+/**
+ * @brief verifies the signature a configuration with the offline master key.
+ *
+ * @param config configuration of an extension given as JSON object
+ * @param master_priv offline master public key of the exchange
+ * @param[out] master_sig  signature
+ * @return GNUNET_OK on success, GNUNET_SYSERR otherwise
+ */
+static enum GNUNET_GenericReturnValue
+config_verify (
+  const json_t *config,
+  const struct TALER_MasterPublicKeyP *master_pub,
+  const struct TALER_MasterSignatureP *master_sig
+  )
+{
+  enum GNUNET_GenericReturnValue ret;
+  struct TALER_ExtensionConfigHash h_config;
+
+  ret = TALER_extension_config_hash (config, &h_config);
+  if (GNUNET_OK != ret)
+  {
+    GNUNET_break (0);
+    return ret;
+  }
+
+  return TALER_exchange_offline_extension_config_hash_verify (h_config,
+                                                              master_pub,
+                                                              master_sig);
+}
+
+
 /**
  * Function implementing database transaction to set the configuration of
  * extensions.  It runs the transaction logic.
@@ -88,7 +115,7 @@ set_extensions (void *cls,
     enum GNUNET_DB_QueryStatus qs;
     char *config;
 
-    config = json_dumps (ext->config_json, JSON_COMPACT | JSON_SORT_KEYS);
+    config = json_dumps (ext->config, JSON_COMPACT | JSON_SORT_KEYS);
     if (NULL == config)
     {
       GNUNET_break (0);
@@ -143,7 +170,7 @@ TEH_handler_management_post_extensions (
   struct SetExtensionsContext sec = {0};
   json_t *extensions;
   json_t *extensions_sigs;
-  struct GNUNET_JSON_Specification spec[] = {
+  struct GNUNET_JSON_Specification top_spec[] = {
     GNUNET_JSON_spec_json ("extensions",
                            &extensions),
     GNUNET_JSON_spec_json ("extensions_sigs",
@@ -157,7 +184,7 @@ TEH_handler_management_post_extensions (
 
     res = TALER_MHD_parse_json_data (connection,
                                      root,
-                                     spec);
+                                     top_spec);
     if (GNUNET_SYSERR == res)
       return MHD_NO; /* hard failure */
     if (GNUNET_NO == res)
@@ -168,7 +195,7 @@ TEH_handler_management_post_extensions (
          json_is_array (extensions_sigs)) )
   {
     GNUNET_break_op (0);
-    GNUNET_JSON_parse_free (spec);
+    GNUNET_JSON_parse_free (top_spec);
     return TALER_MHD_reply_with_error (
       connection,
       MHD_HTTP_BAD_REQUEST,
@@ -180,7 +207,7 @@ TEH_handler_management_post_extensions (
   if (json_array_size (extensions) != sec.num_extensions)
   {
     GNUNET_break_op (0);
-    GNUNET_JSON_parse_free (spec);
+    GNUNET_JSON_parse_free (top_spec);
     return TALER_MHD_reply_with_error (
       connection,
       MHD_HTTP_BAD_REQUEST,
@@ -198,105 +225,53 @@ TEH_handler_management_post_extensions (
 
   for (unsigned int i = 0; i<sec.num_extensions; i++)
   {
-    // 1. parse the extension
+    // 1. parse the extension out of the json
+    enum GNUNET_GenericReturnValue res;
+    const struct TALER_Extension *extension;
+    const char *name;
+    struct GNUNET_JSON_Specification ext_spec[] = {
+      GNUNET_JSON_spec_string ("extension",
+                               &name),
+      GNUNET_JSON_spec_json ("config",
+                             &sec.extensions[i].config),
+      GNUNET_JSON_spec_end ()
+    };
+
+    res = TALER_MHD_parse_json_array (connection,
+                                      extensions,
+                                      ext_spec,
+                                      i,
+                                      -1);
+    if (GNUNET_SYSERR == res)
     {
-      enum GNUNET_GenericReturnValue res;
+      ret = MHD_NO; /* hard failure */
-      const char *name;
+      goto CLEANUP;
-      struct GNUNET_JSON_Specification ispec[] = {
+    }
-        GNUNET_JSON_spec_string ("extension",
+    if (GNUNET_NO == res)
-                                 &name),
+    {
-        GNUNET_JSON_spec_json ("config",
+      ret = MHD_YES;
-                               &sec.extensions[i].config_json),
+      goto CLEANUP;
-        GNUNET_JSON_spec_end ()
-      };
-
-      res = TALER_MHD_parse_json_array (connection,
-                                        extensions,
-                                        ispec,
-                                        i,
-                                        -1);
-      if (GNUNET_SYSERR == res)
-      {
-        ret = MHD_NO; /* hard failure */
-        goto CLEANUP;
-      }
-      if (GNUNET_NO == res)
-      {
-        ret = MHD_YES;
-        goto CLEANUP;;
-      }
-
-      /* Make sure name refers to a supported extension */
-      {
-        bool found = false;
-        for (unsigned int k = 0; k < TALER_Extension_Max; k++)
-        {
-          if (0 == strncmp (name,
-                            TEH_extensions[k].name,
-                            strlen (TEH_extensions[k].name)))
-          {
-            sec.extensions[i].type = TEH_extensions[k].type;
-            found = true;
-            break;
-          }
-        }
-
-        if (! found)
-        {
-          ret = TALER_MHD_reply_with_error (
-            connection,
-            MHD_HTTP_BAD_REQUEST,
-            TALER_EC_GENERIC_PARAMETER_MALFORMED,
-            "invalid extension type");
-          goto CLEANUP;
-        }
-      }
-
-      /* We have a JSON object for the extension.
-       * Increment its refcount and free the parser.
-       * TODO: is this correct?  */
-      json_incref (sec.extensions[i].config_json);
-      GNUNET_JSON_parse_free (ispec);
-
-      /* Make sure the config is sound */
-      {
-        switch (sec.extensions[i].type)
-        {
-        case TALER_Extension_AgeRestriction:
-          if (GNUNET_OK != TALER_agemask_parse_json (
-                sec.extensions[i].config_json,
-                &sec.extensions[i].mask))
-          {
-            ret = TALER_MHD_reply_with_error (
-              connection,
-              MHD_HTTP_BAD_REQUEST,
-              TALER_EC_GENERIC_PARAMETER_MALFORMED,
-              "invalid mask for age restriction");
-            goto CLEANUP;
-          }
-          break;
-
-        case TALER_Extension_Peer2Peer:
-          /* TODO */
-          GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
-                      "peer2peer not yet supported in handler for /management/extensions\n");
-          ret = MHD_NO;
-          goto CLEANUP;
-
-        default:
-          /* not reachable */
-          GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
-                      "shouldn't be reached in handler for /management/extensions\n");
-          ret = MHD_NO;
-          goto CLEANUP;
-        }
-      }
     }
 
-    // 2. parse and verify the signature
+    /* 2. Make sure name refers to a supported extension */
+    if (GNUNET_OK != TALER_get_extension_by_name (name,
+                                                  TEH_extensions,
+                                                  &extension))
+    {
+      ret = TALER_MHD_reply_with_error (
+        connection,
+        MHD_HTTP_BAD_REQUEST,
+        TALER_EC_GENERIC_PARAMETER_MALFORMED,
+        "invalid extension type");
+      goto CLEANUP;
+    }
+
+    sec.extensions[i].type = extension->type;
+
+    /* 3. Extract the signature out of the json array */
     {
       enum GNUNET_GenericReturnValue res;
-      struct GNUNET_JSON_Specification ispec[] = {
+      struct GNUNET_JSON_Specification sig_spec[] = {
         GNUNET_JSON_spec_fixed_auto (NULL,
                                      &sec.extensions_sigs[i]),
         GNUNET_JSON_spec_end ()
@@ -304,7 +279,7 @@ TEH_handler_management_post_extensions (
 
       res = TALER_MHD_parse_json_array (connection,
                                         extensions_sigs,
-                                        ispec,
+                                        sig_spec,
                                         i,
                                         -1);
       if (GNUNET_SYSERR == res)
@@ -317,44 +292,41 @@ TEH_handler_management_post_extensions (
         ret = MHD_YES;
         goto CLEANUP;
       }
-
-      /* verify the signature */
-      res = GNUNET_SYSERR;
-
-      switch (sec.extensions[i].type)
-      {
-      case TALER_Extension_AgeRestriction:
-        res = TALER_exchange_offline_extension_agemask_verify (
-          sec.extensions[i].mask,
-          &TEH_master_public_key,
-          &sec.extensions_sigs[i]);
-        break;
-
-      case TALER_Extension_Peer2Peer:
-        /* TODO */
-        GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
-                    "Peer2peer not yet supported in handler for /management/extensions\n");
-        ret = MHD_NO;
-        goto CLEANUP;
-
-      default:
-        /* not reachable */
-        GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
-                    "shouldn't be reached in handler for /management/extensions\n");
-        ret = MHD_NO;
-        goto CLEANUP;
-      }
-
-      if (GNUNET_OK != res)
-      {
-        ret = TALER_MHD_reply_with_error (
-          connection,
-          MHD_HTTP_BAD_REQUEST,
-          TALER_EC_GENERIC_PARAMETER_MALFORMED,
-          "invalid signature for extension");
-        goto CLEANUP;
-      }
     }
+
+    /* 4. Verify the signature of the config */
+    if (GNUNET_OK != config_verify (
+          sec.extensions[i].config,
+          &TEH_master_public_key,
+          &sec.extensions_sigs[i]))
+    {
+      ret = TALER_MHD_reply_with_error (
+        connection,
+        MHD_HTTP_BAD_REQUEST,
+        TALER_EC_GENERIC_PARAMETER_MALFORMED,
+        "invalid signature for extension");
+      goto CLEANUP;
+    }
+
+    /* 5. Make sure the config is sound */
+    if (GNUNET_OK != extension->parse_config (NULL /* only verify */,
+                                              sec.extensions[i].config))
+    {
+      GNUNET_JSON_parse_free (ext_spec);
+      ret = TALER_MHD_reply_with_error (
+        connection,
+        MHD_HTTP_BAD_REQUEST,
+        TALER_EC_GENERIC_PARAMETER_MALFORMED,
+        "invalid configuration for extension");
+      goto CLEANUP;
+
+    }
+
+    /* We have a validly signed JSON object for the extension.
+     * Increment its refcount and free the parser for the extension.
+     */
+    json_incref (sec.extensions[i].config);
+    GNUNET_JSON_parse_free (ext_spec);
   } /* for-loop */
 
   GNUNET_log (GNUNET_ERROR_TYPE_INFO,
@@ -386,14 +358,14 @@ TEH_handler_management_post_extensions (
 CLEANUP:
   for (unsigned int i = 0; i < sec.num_extensions; i++)
   {
-    if (NULL != sec.extensions[i].config_json)
+    if (NULL != sec.extensions[i].config)
     {
-      json_decref (sec.extensions[i].config_json);
+      json_decref (sec.extensions[i].config);
     }
   }
   GNUNET_free (sec.extensions);
   GNUNET_free (sec.extensions_sigs);
-  GNUNET_JSON_parse_free (spec);
+  GNUNET_JSON_parse_free (top_spec);
   return ret;
 }
 

src/include/taler_crypto_lib.h

@@ -23,7 +23,6 @@
 #define TALER_CRYPTO_LIB_H
 
 #include <gnunet/gnunet_util_lib.h>
-#include "taler_extensions.h"
 #include "taler_error_codes.h"
 #include <gcrypt.h>
 
@@ -281,6 +280,26 @@ struct TALER_MasterSignatureP
   struct GNUNET_CRYPTO_EddsaSignature eddsa_signature;
 };
 
+/*
+ * @brief Type of a list of age groups, represented as bit mask.
+ *
+ * The bits set in the mask mark the edges at the beginning of a next age
+ * group.  F.e. for the age groups
+ *     0-7, 8-9, 10-11, 12-14, 14-15, 16-17, 18-21, 21-*
+ * the following bits are set:
+ *
+ *   31     24        16        8         0
+ *   |      |         |         |         |
+ *   oooooooo  oo1oo1o1  o1o1o1o1  ooooooo1
+ *
+ * A value of 0 means that the exchange does not support the extension for
+ * age-restriction.
+ */
+struct TALER_AgeMask
+{
+  uint32_t mask;
+};
+
 /**
  * @brief Age restriction commitment of a coin.
  */
@@ -523,6 +542,19 @@ struct TALER_PickupIdentifierP
 };
 
 
+/**
+ * @brief Salted hash over the JSON object representing the configuration of an
+ * extension.
+ */
+struct TALER_ExtensionConfigHash
+{
+  /**
+   * Actual hash value.
+   */
+  struct GNUNET_HashCode hash;
+};
+
+
 GNUNET_NETWORK_STRUCT_END
 
 
@@ -2502,30 +2534,31 @@ TALER_merchant_wire_signature_make (
 /* **************** /management/extensions offline signing **************** */
 
 /**
- * Create a signature for age restriction groups
+ * Create a signature for the hash of the configuration of an extension
  *
- * @param mask The bitmask representing age groups
+ * @param h_config hash of the JSON object representing the configuration
  * @param master_priv private key to sign with
  * @param[out] master_sig where to write the signature
  */
 void
-TALER_exchange_offline_extension_agemask_sign (
+TALER_exchange_offline_extension_config_hash_sign (
-  const struct TALER_AgeMask mask,
+  const struct TALER_ExtensionConfigHash h_config,
   const struct TALER_MasterPrivateKeyP *master_priv,
   struct TALER_MasterSignatureP *master_sig);
 
 
 /**
- * Verify the signature in @a master_sig.
+ * Verify the signature in @a master_sig of the given hash, taken over the JSON
+ * blob representing the configuration of an extension
  *
- * @param mask bit mask representing an age group for age restriction
+ * @param h_config hash of the JSON blob of a configuration of an extension
  * @param master_pub master public key of the exchange
  * @param master_sig signature of the exchange
  * @return #GNUNET_OK if signature is valid
  */
 enum GNUNET_GenericReturnValue
-TALER_exchange_offline_extension_agemask_verify (
+TALER_exchange_offline_extension_config_hash_verify (
-  const struct TALER_AgeMask mask,
+  const struct TALER_ExtensionConfigHash h_config,
   const struct TALER_MasterPublicKeyP *master_pub,
   const struct TALER_MasterSignatureP *master_sig
   );

src/include/taler_extensions.h

@@ -23,6 +23,7 @@
 
 #include <gnunet/gnunet_util_lib.h>
 #include "taler_crypto_lib.h"
+#include "taler_json_lib.h"
 
 
 #define TALER_EXTENSION_SECTION_PREFIX "exchange-extension-"
@@ -39,41 +40,45 @@ enum TALER_Extension_Type
 {
   TALER_Extension_AgeRestriction = 0,
   TALER_Extension_Peer2Peer = 1,
-  TALER_Extension_Max = 2
+  TALER_Extension_Max = 2 // Must be last
 };
 
+/*
+ * TODO oec: documentation
+ */
 struct TALER_Extension
 {
   enum TALER_Extension_Type type;
   char *name;
   bool critical;
   void *config;
+
+  enum GNUNET_GenericReturnValue (*parse_config)(struct TALER_Extension *this,
+                                                 const json_t *config);
+  json_t *(*config_to_json)(const struct TALER_Extension *this);
 };
 
+/**
+ * Generic functions for extensions
+ */
+
+/**
+ * Finds and returns a supported extension by a given name.
+ *
+ * @param name name of the extension to lookup
+ * @param extensions list of TALER_Extensions as haystack, terminated by an entry of type TALER_Extension_Max
+ * @param[out] ext set to the extension, if found, NULL otherwise
+ * @return GNUNET_OK if extension was found, GNUNET_NO otherwise
+ */
+enum GNUNET_GenericReturnValue
+TALER_get_extension_by_name (const char *name,
+                             const struct TALER_Extension *extensions,
+                             const struct TALER_Extension **ext);
+
 /*
  * TALER Age Restriction Extension
  */
 
-/*
- * @brief Type of a list of age groups, represented as bit mask.
- *
- * The bits set in the mask mark the edges at the beginning of a next age
- * group.  F.e. for the age groups
- *     0-7, 8-9, 10-11, 12-14, 14-15, 16-17, 18-21, 21-*
- * the following bits are set:
- *
- *   31     24        16        8         0
- *   |      |         |         |         |
- *   oooooooo  oo1oo1o1  o1o1o1o1  ooooooo1
- *
- * A value of 0 means that the exchange does not support the extension for
- * age-restriction.
- */
-struct TALER_AgeMask
-{
-  uint32_t mask;
-};
-
 #define TALER_EXTENSION_SECTION_AGE_RESTRICTION (TALER_EXTENSION_SECTION_PREFIX  \
                                                  "age_restriction")
 
@@ -86,7 +91,19 @@ struct TALER_AgeMask
                                                 << 21)
 
 /**
- * @param groups String representation of age groups, like: "8:10:12:14:16:18:21"
+ * @brief Parses a string as a list of age groups.
+ *
+ * The string must consist of a colon-separated list of increasing integers
+ * between 0 and 31.  Each entry represents the beginning of a new age group.
+ * F.e. the string "8:10:12:14:16:18:21" parses into the following list of age
+ * groups
+ *   0-7, 8-9, 10-11, 12-13, 14-15, 16-17, 18-20, 21-...
+ * which then is represented as bit mask with the corresponding bits set:
+ *   31     24        16        8         0
+ *   |      |         |         |         |
+ *   oooooooo  oo1oo1o1  o1o1o1o1  ooooooo1
+ *
+ * @param groups String representation of age groups
  * @param[out] mask Mask representation for age restriction.
  * @return Error, if age groups were invalid, OK otherwise.
  */

src/include/taler_json_lib.h

@@ -532,7 +532,7 @@ TALER_JSON_wire_to_payto (const json_t *wire_s);
 
 
 /**
- * Hash @a extensions.
+ * Hash @a extensions in deposits.
  *
  * @param extensions contract extensions to hash
  * @param[out] ech where to write the extension hash
@@ -541,6 +541,16 @@ void
 TALER_deposit_extension_hash (const json_t *extensions,
                               struct TALER_ExtensionContractHash *ech);
 
+/**
+ * Hash the @a config of an extension, given as JSON
+ *
+ * @param config configuration of the extension
+ * @param[out] eh where to write the extension hash
+ * @return GNUNET_OK on success, GNUNET_SYSERR on failure
+ */
+enum GNUNET_GenericReturnValue
+TALER_extension_config_hash (const json_t *config,
+                             struct TALER_ExtensionConfigHash *eh);
 
 /**
  * Parses a JSON object { "extension": "age_restriction", "mask": <uint32> }.
@@ -553,7 +563,6 @@ enum GNUNET_GenericReturnValue
 TALER_agemask_parse_json (const json_t *root,
                           struct TALER_AgeMask *mask);
 
-
 #endif /* TALER_JSON_LIB_H_ */
 
 /* End of taler_json_lib.h */

src/include/taler_signatures.h

@@ -967,9 +967,9 @@ struct TALER_MasterDelWirePS
 
 /*
  * @brief Signature made by the exchange offline key over the
- * configuration of the age restriction extension.
+ * configuration of an extension.
  */
-struct TALER_MasterExtensionAgeRestrictionPS
+struct TALER_MasterExtensionConfigurationPS
 {
   /**
    * Purpose is #TALER_SIGNATURE_MASTER_EXTENSION.   Signed
@@ -978,29 +978,11 @@ struct TALER_MasterExtensionAgeRestrictionPS
   struct GNUNET_CRYPTO_EccSignaturePurpose purpose;
 
   /**
-   * Bit mask representing the lits of age groups, see TALER_AgeMask for a
+   * Hash of the JSON object that represents the configuration of an extension.
-   * description.
    */
-  struct TALER_AgeMask mask;
+  struct TALER_ExtensionConfigHash h_config GNUNET_PACKED;
 };
 
-#if 0
-/*
- * @brief Signature made by the exchange offline key over the
- * configuration of the peer2peer extension.
- */
-struct TALER_MasterExtensionPeer2PeerPS
-{
-  /**
-   * Purpose is #TALER_SIGNATURE_MASTER_EXTENSION.   Signed
-   * by a `struct TALER_MasterPublicKeyP` using EdDSA.
-   */
-  struct GNUNET_CRYPTO_EccSignaturePurpose purpose;
-
-  // TODO oec
-};
-#endif
-
 /**
  * @brief Information about a denomination key. Denomination keys
  * are used to sign coins of a certain value into existence.

src/json/json.c

@@ -1009,4 +1009,14 @@ TALER_deposit_extension_hash (const json_t *extensions,
 }
 
 
+enum GNUNET_GenericReturnValue
+TALER_extension_config_hash (const json_t *config,
+                             struct TALER_ExtensionConfigHash *ech)
+{
+  return dump_and_hash (config,
+                        "taler-extension-configuration",
+                        &ech->hash);
+}
+
+
 /* End of json/json.c */

src/lib/exchange_api_management_post_extensions.c

@@ -153,32 +153,17 @@ TALER_EXCHANGE_management_post_extensions (
   GNUNET_assert (NULL != extensions);
   for (unsigned int i = 0; i<pkd->num_extensions; i++)
   {
-    json_t *config;
+    const json_t *config;
-    const struct TALER_AgeMask *mask;
     const struct TALER_Extension *ext = &pkd->extensions[i];
 
-    switch (ext->type)
+    config = ext->config_to_json (ext);
-    {
-    // TODO: case TALER_Extension_Peer2Peer
-    case TALER_Extension_AgeRestriction:
-      mask = (const struct TALER_AgeMask *) (&ext->config);
-      config = GNUNET_JSON_PACK (
-        GNUNET_JSON_pack_string ("extension",
-                                 ext->name),
-        GNUNET_JSON_pack_data_auto ("mask",
-                                    &mask->mask));
-      GNUNET_assert (NULL != config);
-      break;
-    default:
-      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
-                  "Extension not supported.\n");
-    }
 
+    GNUNET_assert (NULL != config);
     GNUNET_assert (0 ==
                    json_array_append_new (
                      extensions,
                      GNUNET_JSON_PACK (
-                       GNUNET_JSON_pack_data_auto ("name",
+                       GNUNET_JSON_pack_data_auto ("extension",
                                                    &ext->name),
                        GNUNET_JSON_pack_data_auto ("config",
                                                    config)

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 \

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_get_extension_by_name (const char *name,
+                             const struct TALER_Extension *extensions,
+                             const struct TALER_Extension **ext)
+{
+
+  const struct TALER_Extension *it = extensions;
+
+  for (; it->type != TALER_Extension_Max; it++)
+  {
+    if (0 == strncmp (name,
+                      it->name,
+                      strlen (it->name)))
+    {
+      *ext = it;
+      return GNUNET_OK;
+    }
+  }
+
+  return GNUNET_NO;
+}
+
+
+/* end of extensions.c */

src/util/offline_signatures.c

@@ -491,66 +491,40 @@ TALER_exchange_offline_wire_fee_verify (
 
 
 void
-TALER_exchange_offline_extension_agemask_sign (
+TALER_exchange_offline_extension_config_hash_sign (
-  const struct TALER_AgeMask mask,
+  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)),
+    .purpose.size = htonl (sizeof(ec)),
-    .mask = mask
+    .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 (
+TALER_exchange_offline_extension_config_hash_verify (
-  const struct TALER_AgeMask mask,
+  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)),
+    .purpose.size = htonl (sizeof(ec)),
-    .mask = mask
+    .h_config = h_config
   };
-  return
+
-    GNUNET_CRYPTO_eddsa_verify (TALER_SIGNATURE_MASTER_EXTENSION,
+  return GNUNET_CRYPTO_eddsa_verify (TALER_SIGNATURE_MASTER_EXTENSION,
-                                &ar,
+                                     &ec,
-                                &master_sig->eddsa_signature,
+                                     &master_sig->eddsa_signature,
-                                &master_pub->eddsa_pub);
+                                     &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;
-}
-
-
-#endif
-
 /* end of offline_signatures.c */