[age restriction] progress 9/n

More worke towards support for extensions and age restriction:

- taler-exchange-httpd_management_extensions.c almost completed
  - handling of request implemented
  - stub "set_extensions" for database transaction added

- utility functions added
  - TALER_exchange_offline_extension_agemask_{sign,verify}
  - TALER_agemask_parse_json

12 files changed, 493 insertions, 372 deletions

diff --git a/src/exchange/taler-exchange-httpd.c b/src/exchange/taler-exchange-httpd.c
index de4ffc7ca..b435ee4ae 100644
--- a/src/exchange/taler-exchange-httpd.c
+++ b/src/exchange/taler-exchange-httpd.c
@@ -53,6 +53,7 @@
 #include "taler-exchange-httpd_withdraw.h"
 #include "taler_exchangedb_lib.h"
 #include "taler_exchangedb_plugin.h"
+#include "taler_extensions.h"
 #include <gnunet/gnunet_mhd_compat.h>
 
 /**
@@ -147,6 +148,25 @@ int TEH_check_invariants_flag;
 bool TEH_suicide;
 
 /**
+ * The global manifest with the list supported extensions, sorted by
+ * TALER_Extension_Type.
+ **/
+const struct TALER_Extension TEH_extensions[TALER_Extension_Max] = {
+  [TALER_Extension_Peer2Peer] = {
+    .type = TALER_Extension_Peer2Peer,
+    .name = "peer2peer",
+    .critical = false,
+    .config = NULL, // disabled per default
+  },
+  [TALER_Extension_AgeRestriction] = {
+    .type = TALER_Extension_AgeRestriction,
+    .name = "age_restriction",
+    .critical = false,
+    .config = NULL, // disabled per default
+  },
+};
+
+/**
  * Value to return from main()
  */
 static int global_ret;
@@ -184,7 +204,6 @@ struct GNUNET_CURL_Context *TEH_curl_ctx;
  */
 static struct GNUNET_CURL_RescheduleContext *exchange_curl_rc;
 
-
 /**
  * Signature of functions that handle operations on coins.
  *
diff --git a/src/exchange/taler-exchange-httpd.h b/src/exchange/taler-exchange-httpd.h
index cad74d2ed..fa47af6f4 100644
--- a/src/exchange/taler-exchange-httpd.h
+++ b/src/exchange/taler-exchange-httpd.h
@@ -26,6 +26,7 @@
 #include <microhttpd.h>
 #include "taler_json_lib.h"
 #include "taler_crypto_lib.h"
+#include "taler_extensions.h"
 #include <gnunet/gnunet_mhd_compat.h>
 
 
@@ -201,6 +202,11 @@ extern volatile bool MHD_terminating;
 extern struct GNUNET_CURL_Context *TEH_curl_ctx;
 
 /**
+ * The manifest of the available extensions
+ */
+extern const struct TALER_Extension TEH_extensions[TALER_Extension_Max];
+
+/**
  * @brief Struct describing an URL and the handler for it.
  */
 struct TEH_RequestHandler;
diff --git a/src/exchange/taler-exchange-httpd_management_extensions.c b/src/exchange/taler-exchange-httpd_management_extensions.c
index 96b42abb2..6a771bf43 100644
--- a/src/exchange/taler-exchange-httpd_management_extensions.c
+++ b/src/exchange/taler-exchange-httpd_management_extensions.c
@@ -1,18 +1,18 @@
 /*
-  This file is part of TALER
-  Copyright (C) 2021 Taler Systems SA
+   This file is part of TALER
+   Copyright (C) 2021 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 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 Affero General Public License for more details.
+   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 Affero General Public License for more details.
 
-  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/>
-*/
+   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/>
+ */
 /**
  * @file taler-exchange-httpd_management_extensions.c
  * @brief Handle request to POST /management/extensions
@@ -23,260 +23,80 @@
 #include <gnunet/gnunet_json_lib.h>
 #include <jansson.h>
 #include <microhttpd.h>
-#include <pthread.h>
 #include "taler_json_lib.h"
 #include "taler_mhd_lib.h"
 #include "taler_signatures.h"
 #include "taler-exchange-httpd_management.h"
 #include "taler-exchange-httpd_responses.h"
+#include "taler_extensions.h"
+
+
+struct Extension
+{
+  enum TALER_Extension_Type type;
+  json_t *config_json;
 
+  // This union contains the parsed configuration for each extension.
+  union
+  {
+    // configuration for the age restriction
+    struct TALER_AgeMask mask;
+
+    /* TODO oec - peer2peer config */
+  };
+};
 
-#if 0
 /**
- * Function implementing database transaction to add offline signing keys.
- * Runs the transaction logic; IF it returns a non-error code, the transaction
- * logic MUST NOT queue a MHD response.  IF it returns an hard error, the
- * transaction logic MUST queue a MHD response and set @a mhd_ret.  IF it
- * returns the soft error code, the function MAY be called again to retry and
- * MUST not queue a MHD response.
+ * Closure for the #set_extensions transaction
+ */
+struct SetExtensionsContext
+{
+  uint32_t num_extensions;
+  struct Extension *extensions;
+  struct TALER_MasterSignatureP *extensions_sigs;
+};
+
+/**
+ * Function implementing database transaction to set the configuration of
+ * extensions.  It runs the transaction logic.
+ *  - IF it returns a non-error code, the transaction logic MUST NOT queue a
+ *    MHD response.
+ *  - IF it returns an hard error, the transaction logic MUST queue a MHD
+ *    response and set @a mhd_ret.
+ *  - IF it returns the soft error code, the function MAY be called again to
+ *    retry and MUST not queue a MHD response.
  *
- * @param cls closure with a `struct AddKeysContext`
+ * @param cls closure with a `struct SetExtensionsContext`
  * @param connection MHD request which triggered the transaction
  * @param[out] mhd_ret set to MHD response status for @a connection,
  *             if transaction failed (!)
  * @return transaction status
  */
 static enum GNUNET_DB_QueryStatus
-add_keys (void *cls,
-          struct MHD_Connection *connection,
-          MHD_RESULT *mhd_ret)
+set_extensions (void *cls,
+                struct MHD_Connection *connection,
+                MHD_RESULT *mhd_ret)
 {
-  struct AddKeysContext *akc = cls;
-
-  /* activate all denomination keys */
-  for (unsigned int i = 0; i<akc->nd_sigs; i++)
-  {
-    struct DenomSig *d = &akc->d_sigs[i];
-    enum GNUNET_DB_QueryStatus qs;
-    bool is_active = false;
-    struct TALER_EXCHANGEDB_DenominationKeyMetaData meta;
-    struct TALER_DenominationPublicKey denom_pub;
-
-    /* For idempotency, check if the key is already active */
-    memset (&denom_pub,
-            0,
-            sizeof (denom_pub));
-    qs = TEH_plugin->lookup_denomination_key (
-      TEH_plugin->cls,
-      &d->h_denom_pub,
-      &meta);
-    if (qs < 0)
-    {
-      if (GNUNET_DB_STATUS_SOFT_ERROR == qs)
-        return qs;
-      GNUNET_break (0);
-      *mhd_ret = TALER_MHD_reply_with_error (connection,
-                                             MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                             TALER_EC_GENERIC_DB_FETCH_FAILED,
-                                             "lookup denomination key");
-      return qs;
-    }
-    if (0 == qs)
-    {
-      enum GNUNET_GenericReturnValue rv;
-
-      rv = TEH_keys_load_fees (&d->h_denom_pub,
-                               &denom_pub,
-                               &meta);
-      switch (rv)
-      {
-      case GNUNET_SYSERR:
-        *mhd_ret = TALER_MHD_reply_with_error (
-          connection,
-          MHD_HTTP_INTERNAL_SERVER_ERROR,
-          TALER_EC_EXCHANGE_GENERIC_BAD_CONFIGURATION,
-          GNUNET_h2s (&d->h_denom_pub.hash));
-        return GNUNET_DB_STATUS_HARD_ERROR;
-      case GNUNET_NO:
-        *mhd_ret = TALER_MHD_reply_with_error (
-          connection,
-          MHD_HTTP_NOT_FOUND,
-          TALER_EC_EXCHANGE_GENERIC_DENOMINATION_KEY_UNKNOWN,
-          GNUNET_h2s (&d->h_denom_pub.hash));
-        return GNUNET_DB_STATUS_HARD_ERROR;
-      case GNUNET_OK:
-        break;
-      }
-    }
-    else
-    {
-      is_active = true;
-    }
-
-    /* check signature is valid */
-    if (GNUNET_OK !=
-        TALER_exchange_offline_denom_validity_verify (
-          &d->h_denom_pub,
-          meta.start,
-          meta.expire_withdraw,
-          meta.expire_deposit,
-          meta.expire_legal,
-          &meta.value,
-          &meta.fee_withdraw,
-          &meta.fee_deposit,
-          &meta.fee_refresh,
-          &meta.fee_refund,
-          &TEH_master_public_key,
-          &d->master_sig))
-    {
-      GNUNET_break_op (0);
-      *mhd_ret = TALER_MHD_reply_with_error (
-        connection,
-        MHD_HTTP_FORBIDDEN,
-        TALER_EC_EXCHANGE_MANAGEMENT_KEYS_DENOMKEY_ADD_SIGNATURE_INVALID,
-        GNUNET_h2s (&d->h_denom_pub.hash));
-      if (! is_active)
-        TALER_denom_pub_free (&denom_pub);
-      return GNUNET_DB_STATUS_HARD_ERROR;
-    }
-    if (is_active)
-    {
-      GNUNET_log (GNUNET_ERROR_TYPE_INFO,
-                  "Denomination key %s already active, skipping\n",
-                  GNUNET_h2s (&d->h_denom_pub.hash));
-      continue; /* skip, already known */
-    }
-    qs = TEH_plugin->add_denomination_key (
-      TEH_plugin->cls,
-      &d->h_denom_pub,
-      &denom_pub,
-      &meta,
-      &d->master_sig);
-    TALER_denom_pub_free (&denom_pub);
-    if (qs < 0)
-    {
-      if (GNUNET_DB_STATUS_SOFT_ERROR == qs)
-        return qs;
-      GNUNET_break (0);
-      *mhd_ret = TALER_MHD_reply_with_error (connection,
-                                             MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                             TALER_EC_GENERIC_DB_STORE_FAILED,
-                                             "activate denomination key");
-      return qs;
-    }
-    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
-                "Added offline signature for denomination `%s'\n",
-                GNUNET_h2s (&d->h_denom_pub.hash));
-    GNUNET_assert (0 != qs);
-  }
+  // struct SetExtensionContext *sec = cls;
 
-  for (unsigned int i = 0; i<akc->ns_sigs; i++)
-  {
-    struct SigningSig *s = &akc->s_sigs[i];
-    enum GNUNET_DB_QueryStatus qs;
-    bool is_active = false;
-    struct TALER_EXCHANGEDB_SignkeyMetaData meta;
-
-    qs = TEH_plugin->lookup_signing_key (
-      TEH_plugin->cls,
-      &s->exchange_pub,
-      &meta);
-    if (qs < 0)
-    {
-      if (GNUNET_DB_STATUS_SOFT_ERROR == qs)
-        return qs;
-      GNUNET_break (0);
-      *mhd_ret = TALER_MHD_reply_with_error (connection,
-                                             MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                             TALER_EC_GENERIC_DB_FETCH_FAILED,
-                                             "lookup signing key");
-      return qs;
-    }
-    if (0 == qs)
-    {
-      if (GNUNET_OK !=
-          TEH_keys_get_timing (&s->exchange_pub,
-                               &meta))
-      {
-        /* For idempotency, check if the key is already active */
-        *mhd_ret = TALER_MHD_reply_with_error (
-          connection,
-          MHD_HTTP_NOT_FOUND,
-          TALER_EC_EXCHANGE_MANAGEMENT_KEYS_SIGNKEY_UNKNOWN,
-          TALER_B2S (&s->exchange_pub));
-        return GNUNET_DB_STATUS_HARD_ERROR;
-      }
-    }
-    else
-    {
-      is_active = true; /* if we pass, it's active! */
-    }
-
-    /* check signature is valid */
-    if (GNUNET_OK !=
-        TALER_exchange_offline_signkey_validity_verify (
-          &s->exchange_pub,
-          meta.start,
-          meta.expire_sign,
-          meta.expire_legal,
-          &TEH_master_public_key,
-          &s->master_sig))
-    {
-      GNUNET_break_op (0);
-      *mhd_ret = TALER_MHD_reply_with_error (
-        connection,
-        MHD_HTTP_FORBIDDEN,
-        TALER_EC_EXCHANGE_MANAGEMENT_KEYS_SIGNKEY_ADD_SIGNATURE_INVALID,
-        TALER_B2S (&s->exchange_pub));
-      return GNUNET_DB_STATUS_HARD_ERROR;
-    }
-    if (is_active)
-    {
-      GNUNET_log (GNUNET_ERROR_TYPE_INFO,
-                  "Signing key %s already active, skipping\n",
-                  TALER_B2S (&s->exchange_pub));
-      continue;   /* skip, already known */
-    }
-    qs = TEH_plugin->activate_signing_key (
-      TEH_plugin->cls,
-      &s->exchange_pub,
-      &meta,
-      &s->master_sig);
-    if (qs < 0)
-    {
-      if (GNUNET_DB_STATUS_SOFT_ERROR == qs)
-        return qs;
-      GNUNET_break (0);
-      *mhd_ret = TALER_MHD_reply_with_error (connection,
-                                             MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                             TALER_EC_GENERIC_DB_STORE_FAILED,
-                                             "activate signing key");
-      return qs;
-    }
-    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
-                "Added offline signature for signing key `%s'\n",
-                TALER_B2S (&s->exchange_pub));
-    GNUNET_assert (0 != qs);
-  }
+  // TODO oec
   return GNUNET_DB_STATUS_SUCCESS_ONE_RESULT; /* only 'success', so >=0, matters here */
 }
 
 
-#endif
-
 MHD_RESULT
 TEH_handler_management_post_extensions (
   struct MHD_Connection *connection,
   const json_t *root)
 {
-#if 0
-  json_t *denom_sigs;
-  json_t *signkey_sigs;
+  struct SetExtensionsContext sec = {0};
+  json_t *extensions;
+  json_t *extensions_sigs;
   struct GNUNET_JSON_Specification spec[] = {
-    GNUNET_JSON_spec_json ("denom_sigs",
-                           &denom_sigs),
-    GNUNET_JSON_spec_json ("signkey_sigs",
-                           &signkey_sigs),
+    GNUNET_JSON_spec_json ("extensions",
+                           &extensions),
+    GNUNET_JSON_spec_json ("extensions_sigs",
+                           &extensions_sigs),
     GNUNET_JSON_spec_end ()
   };
   bool ok;
@@ -293,8 +113,9 @@ TEH_handler_management_post_extensions (
     if (GNUNET_NO == res)
       return MHD_YES; /* failure */
   }
-  if (! (json_is_array (denom_sigs) &&
-         json_is_array (signkey_sigs)) )
+
+  if (! (json_is_array (extensions) &&
+         json_is_array (extensions_sigs)) )
   {
     GNUNET_break_op (0);
     GNUNET_JSON_parse_free (spec);
@@ -302,113 +123,236 @@ TEH_handler_management_post_extensions (
       connection,
       MHD_HTTP_BAD_REQUEST,
       TALER_EC_GENERIC_PARAMETER_MALFORMED,
-      "array expected for denom_sigs and signkey_sigs");
+      "array expected for extensions and extensions_sig");
   }
+
+  sec.num_extensions = json_array_size (extensions_sigs);
+  if (json_array_size (extensions) != sec.num_extensions)
+  {
+    GNUNET_break_op (0);
+    GNUNET_JSON_parse_free (spec);
+    return TALER_MHD_reply_with_error (
+      connection,
+      MHD_HTTP_BAD_REQUEST,
+      TALER_EC_GENERIC_PARAMETER_MALFORMED,
+      "arrays extensions and extensions_sig are not of equal size");
+  }
+
   GNUNET_log (GNUNET_ERROR_TYPE_INFO,
-              "Received /management/keys\n");
-  akc.nd_sigs = json_array_size (denom_sigs);
-  akc.d_sigs = GNUNET_new_array (akc.nd_sigs,
-                                 struct DenomSig);
+              "Received /management/extensions\n");
+
+  sec.extensions = GNUNET_new_array (sec.num_extensions,
+                                     struct Extension);
+  sec.extensions_sigs = GNUNET_new_array (sec.num_extensions,
+                                          struct TALER_MasterSignatureP);
   ok = true;
-  for (unsigned int i = 0; i<akc.nd_sigs; i++)
+
+  for (unsigned int i = 0; i<sec.num_extensions; i++)
   {
-    struct DenomSig *d = &akc.d_sigs[i];
-    struct GNUNET_JSON_Specification ispec[] = {
-      GNUNET_JSON_spec_fixed_auto ("master_sig",
-                                   &d->master_sig),
-      GNUNET_JSON_spec_fixed_auto ("h_denom_pub",
-                                   &d->h_denom_pub),
-      GNUNET_JSON_spec_end ()
-    };
-    enum GNUNET_GenericReturnValue res;
 
-    res = TALER_MHD_parse_json_data (connection,
-                                     json_array_get (denom_sigs,
-                                                     i),
-                                     ispec);
-    if (GNUNET_SYSERR == res)
+    // 1. parse the extension
     {
-      ret = MHD_NO; /* hard failure */
-      ok = false;
-      break;
-    }
-    if (GNUNET_NO == res)
-    {
-      ret = MHD_YES;
-      ok = false;
-      break;
+      enum GNUNET_GenericReturnValue res;
+      const char *name;
+      struct GNUNET_JSON_Specification ispec[] = {
+        GNUNET_JSON_spec_string ("extension",
+                                 &name),
+        GNUNET_JSON_spec_json ("config",
+                               &sec.extensions[i].config_json),
+        GNUNET_JSON_spec_end ()
+      };
+
+      res = TALER_MHD_parse_json_array (connection,
+                                        extensions,
+                                        ispec,
+                                        i,
+                                        -1);
+      if (GNUNET_SYSERR == res)
+      {
+        ret = MHD_NO; /* hard failure */
+        ok = false;
+        break;
+      }
+      if (GNUNET_NO == res)
+      {
+        ret = MHD_YES;
+        ok = false;
+        break;
+      }
+
+      // 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)
+        {
+          GNUNET_free (sec.extensions);
+          GNUNET_free (sec.extensions_sigs);
+          GNUNET_JSON_parse_free (spec);
+          GNUNET_JSON_parse_free (ispec);
+          return TALER_MHD_reply_with_error (
+            connection,
+            MHD_HTTP_BAD_REQUEST,
+            TALER_EC_GENERIC_PARAMETER_MALFORMED,
+            "invalid extension type");
+        }
+      }
+
+      // 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))
+          {
+            GNUNET_free (sec.extensions);
+            GNUNET_free (sec.extensions_sigs);
+            GNUNET_JSON_parse_free (spec);
+            return TALER_MHD_reply_with_error (
+              connection,
+              MHD_HTTP_BAD_REQUEST,
+              TALER_EC_GENERIC_PARAMETER_MALFORMED,
+              "invalid mask for age restriction");
+          }
+          break;
+
+        case TALER_Extension_Peer2Peer:   /* TODO */
+          ok = false;
+          ret = MHD_NO;
+          goto BREAK;
+
+        default:
+          /* not reachable */
+          GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                      "shouldn't be reached in handler for /management/extensions\n");
+          ok = false;
+          ret = MHD_NO;
+          goto BREAK;
+        }
+      }
     }
-  }
-  if (! ok)
-  {
-    GNUNET_free (akc.d_sigs);
-    GNUNET_JSON_parse_free (spec);
-    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
-                "Failure to handle /management/keys\n");
-    return ret;
-  }
-  akc.ns_sigs = json_array_size (signkey_sigs);
-  akc.s_sigs = GNUNET_new_array (akc.ns_sigs,
-                                 struct SigningSig);
-  for (unsigned int i = 0; i<akc.ns_sigs; i++)
-  {
-    struct SigningSig *s = &akc.s_sigs[i];
-    struct GNUNET_JSON_Specification ispec[] = {
-      GNUNET_JSON_spec_fixed_auto ("master_sig",
-                                   &s->master_sig),
-      GNUNET_JSON_spec_fixed_auto ("exchange_pub",
-                                   &s->exchange_pub),
-      GNUNET_JSON_spec_end ()
-    };
-    enum GNUNET_GenericReturnValue res;
 
-    res = TALER_MHD_parse_json_data (connection,
-                                     json_array_get (signkey_sigs,
-                                                     i),
-                                     ispec);
-    if (GNUNET_SYSERR == res)
+    // 2. parse the signature
     {
-      ret = MHD_NO; /* hard failure */
-      ok = false;
-      break;
+      enum GNUNET_GenericReturnValue res;
+      struct GNUNET_JSON_Specification ispec[] = {
+        GNUNET_JSON_spec_fixed_auto (NULL,
+                                     &sec.extensions_sigs[i]),
+        GNUNET_JSON_spec_end ()
+      };
+
+      res = TALER_MHD_parse_json_array (connection,
+                                        extensions_sigs,
+                                        ispec,
+                                        i,
+                                        -1);
+      if (GNUNET_SYSERR == res)
+      {
+        ret = MHD_NO; /* hard failure */
+        ok = false;
+        break;
+      }
+      if (GNUNET_NO == res)
+      {
+        ret = MHD_YES;
+        ok = false;
+        break;
+      }
     }
-    if (GNUNET_NO == res)
+
+    // 3. verify the signature
     {
-      ret = MHD_YES;
-      ok = false;
-      break;
+      enum GNUNET_GenericReturnValue res;
+
+      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]);
+        if (GNUNET_OK != res)
+        {
+          GNUNET_free (sec.extensions);
+          GNUNET_free (sec.extensions_sigs);
+          GNUNET_JSON_parse_free (spec);
+          return TALER_MHD_reply_with_error (
+            connection,
+            MHD_HTTP_BAD_REQUEST,
+            TALER_EC_GENERIC_PARAMETER_MALFORMED,
+            "invalid signature for age mask");
+        }
+        break;
+
+      case TALER_Extension_Peer2Peer:   /* TODO */
+        GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                    "Peer2peer not yet supported in handler for /management/extensions\n");
+        ok = false;
+        ret = MHD_NO;
+        goto BREAK;
+
+      default:
+        GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                    "shouldn't be reached in handler for /management/extensions\n");
+        ok = false;
+        ret = MHD_NO;
+        /* not reachable */
+        goto BREAK;
+      }
     }
   }
+
+BREAK:
   if (! ok)
   {
     GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
-                "Failure to handle /management/keys\n");
-    GNUNET_free (akc.d_sigs);
-    GNUNET_free (akc.s_sigs);
+                "Failure to handle /management/extensions\n");
+    GNUNET_free (sec.extensions);
+    GNUNET_free (sec.extensions_sigs);
     GNUNET_JSON_parse_free (spec);
     return ret;
   }
+
+
   GNUNET_log (GNUNET_ERROR_TYPE_INFO,
-              "Received %u denomination and %u signing key signatures\n",
-              akc.nd_sigs,
-              akc.ns_sigs);
+              "Received %u extensions\n",
+              sec.num_extensions);
+
   {
     enum GNUNET_GenericReturnValue res;
 
     res = TEH_DB_run_transaction (connection,
-                                  "add keys",
+                                  "set extensions",
                                   TEH_MT_OTHER,
                                   &ret,
-                                  &add_keys,
-                                  &akc);
-    GNUNET_free (akc.d_sigs);
-    GNUNET_free (akc.s_sigs);
+                                  &set_extensions,
+                                  &sec);
+
+    GNUNET_free (sec.extensions);
+    GNUNET_free (sec.extensions_sigs);
     GNUNET_JSON_parse_free (spec);
     if (GNUNET_SYSERR == res)
       return ret;
   }
-  TEH_keys_update_states ();
-#endif
 
   return TALER_MHD_reply_static (
     connection,
diff --git a/src/include/taler_crypto_lib.h b/src/include/taler_crypto_lib.h
index e6c5e2a4d..4ffee54c9 100644
--- a/src/include/taler_crypto_lib.h
+++ b/src/include/taler_crypto_lib.h
@@ -2518,4 +2518,36 @@ TALER_merchant_wire_signature_make (
   struct TALER_MerchantSignatureP *merch_sig);
 
 
+/* **************** /management/extensions offline signing **************** */
+
+/**
+ * Create a signature for age restriction groups
+ *
+ * @param mask The bitmask representing age groups
+ * @param master_priv private key to sign with
+ * @param[out] master_sig where to write the signature
+ */
+void
+TALER_exchange_offline_extension_agemask_sign (
+  const struct TALER_AgeMask mask,
+  const struct TALER_MasterPrivateKeyP *master_priv,
+  struct TALER_MasterSignatureP *master_sig);
+
+
+/**
+ * Verify the signature in @a master_sig.
+ *
+ * @param mask bit mask representing an age group for age restriction
+ * @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 (
+  const struct TALER_AgeMask mask,
+  const struct TALER_MasterPublicKeyP *master_pub,
+  const struct TALER_MasterSignatureP *master_sig
+  );
+
+
 #endif
diff --git a/src/include/taler_exchange_service.h b/src/include/taler_exchange_service.h
index af07588e1..04b731b32 100644
--- a/src/include/taler_exchange_service.h
+++ b/src/include/taler_exchange_service.h
@@ -2680,7 +2680,7 @@ TALER_EXCHANGE_post_management_keys_cancel (
 struct TALER_EXCHANGE_ManagementPostExtensionsData
 {
   struct TALER_Extension *extensions;
-  struct TALER_MasterSignatureP *extension_sigs;
+  struct TALER_MasterSignatureP *extensions_sigs;
   uint32_t num_extensions;
 };
 
diff --git a/src/include/taler_extensions.h b/src/include/taler_extensions.h
index 8f3dd69e7..b6d5c826c 100644
--- a/src/include/taler_extensions.h
+++ b/src/include/taler_extensions.h
@@ -22,6 +22,7 @@
 #define TALER_EXTENSIONS_H
 
 #include <gnunet/gnunet_util_lib.h>
+#include "taler_crypto_lib.h"
 
 
 #define TALER_EXTENSION_SECTION_PREFIX "exchange-extension-"
@@ -36,8 +37,8 @@ enum TALER_Extension_ReturnValue
 
 enum TALER_Extension_Type
 {
-  TALER_Extension_Peer2Peer = 0,
-  TALER_Extension_AgeRestriction = 1,
+  TALER_Extension_AgeRestriction = 0,
+  TALER_Extension_Peer2Peer = 1,
   TALER_Extension_Max = 2
 };
 
@@ -47,40 +48,11 @@ struct TALER_Extension
   char *name;
   bool critical;
   void *config;
-  size_t config_size;
 };
 
-struct TALER_Peer2Peer_Config
-{
-  // FIXME
-};
-
-/**
- * TEH_extensions is the global manifest with the list supported extensions,
- * sorted by TALER_Extension_Type.
- *
- * TODO: Mutex?
- *
- **/
-struct TALER_Extension TEH_extensions[TALER_Extension_Max] = {
-  [TALER_Extension_Peer2Peer] = {
-    .type = TALER_Extension_Peer2Peer,
-    .name = "peer2peer",
-    .critical = false,
-    .config_size = sizeof(struct TALER_Peer2Peer_Config),
-  },
-  [TALER_Extension_AgeRestriction] = {
-    .type = TALER_Extension_AgeRestriction,
-    .name = "age_restriction",
-    .critical = false,
-    .config_size = sizeof(struct TALER_AgeMask),
-  },
-};
-
-
 /*
  * TALER Peer2Peer Extension
- * FIXME
+ * FIXME oec
  */
 
 
diff --git a/src/include/taler_json_lib.h b/src/include/taler_json_lib.h
index b20bd4ea4..888256385 100644
--- a/src/include/taler_json_lib.h
+++ b/src/include/taler_json_lib.h
@@ -542,6 +542,18 @@ TALER_deposit_extension_hash (const json_t *extensions,
                               struct TALER_ExtensionContractHash *ech);
 
 
+/**
+ * Parses a JSON object { "extension": "age_restriction", "mask": <uint32> }.
+ *
+ * @param root is the json object
+ * @param[out] mask on succes, will contain the age mask
+ * @return GNUNET_OK on success and GNUNET_SYSERR on failure.
+ */
+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 */
diff --git a/src/include/taler_signatures.h b/src/include/taler_signatures.h
index bcfa863c1..d9fa7065b 100644
--- a/src/include/taler_signatures.h
+++ b/src/include/taler_signatures.h
@@ -97,6 +97,10 @@
  */
 #define TALER_SIGNATURE_MASTER_WIRE_DETAILS 1030
 
+/**
+ * Set the configuration of an extension (age-restriction or peer2peer)
+ */
+#define TALER_SIGNATURE_MASTER_EXTENSION 1031
 
 /*********************************************/
 /* Exchange online signatures (with signing key) */
@@ -961,6 +965,42 @@ struct TALER_MasterDelWirePS
 };
 
 
+/*
+ * @brief Signature made by the exchange offline key over the
+ * configuration of the age restriction extension.
+ */
+struct TALER_MasterExtensionAgeRestrictionPS
+{
+  /**
+   * Purpose is #TALER_SIGNATURE_MASTER_EXTENSION.   Signed
+   * by a `struct TALER_MasterPublicKeyP` using EdDSA.
+   */
+  struct GNUNET_CRYPTO_EccSignaturePurpose purpose;
+
+  /**
+   * Bit mask representing the lits of age groups, see TALER_AgeMask for a
+   * description.
+   */
+  struct TALER_AgeMask mask;
+};
+
+#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.
diff --git a/src/json/json_helper.c b/src/json/json_helper.c
index 949354e24..3b4da5595 100644
--- a/src/json/json_helper.c
+++ b/src/json/json_helper.c
@@ -659,4 +659,36 @@ TALER_JSON_spec_i18n_str (const char *name,
 }
 
 
+enum GNUNET_GenericReturnValue
+TALER_agemask_parse_json (const json_t *root,
+                          struct TALER_AgeMask *mask)
+{
+  const char *name;
+  struct GNUNET_JSON_Specification spec[] = {
+    GNUNET_JSON_spec_string ("extension",
+                             &name),
+    GNUNET_JSON_spec_uint32 ("mask",
+                             &mask->mask),
+    GNUNET_JSON_spec_end ()
+  };
+
+  if (GNUNET_OK != GNUNET_JSON_parse (root,
+                                      spec,
+                                      NULL,
+                                      NULL))
+  {
+    return GNUNET_SYSERR;
+  }
+
+  if (! strncmp (name,
+                 "age_restriction",
+                 sizeof("age_restriction")))
+  {
+    return GNUNET_SYSERR;
+  }
+
+  return GNUNET_OK;
+}
+
+
 /* end of json/json_helper.c */
diff --git a/src/lib/exchange_api_management_post_extensions.c b/src/lib/exchange_api_management_post_extensions.c
index 7f6349113..a2de2454c 100644
--- a/src/lib/exchange_api_management_post_extensions.c
+++ b/src/lib/exchange_api_management_post_extensions.c
@@ -130,11 +130,10 @@ TALER_EXCHANGE_management_post_extensions (
   void *cb_cls)
 {
   struct TALER_EXCHANGE_ManagementPostExtensionsHandle *ph;
-  //  FIXME-oec: TODO!
   CURL *eh = NULL;
-  json_t *body;
+  json_t *body = NULL;
   json_t *extensions = NULL;
-  json_t *extension_sigs = NULL;
+  json_t *extensions_sigs = NULL;
 
   ph = GNUNET_new (struct TALER_EXCHANGE_ManagementPostExtensionsHandle);
   ph->cb = cb;
@@ -156,16 +155,18 @@ TALER_EXCHANGE_management_post_extensions (
   {
     json_t *config;
     const struct TALER_AgeMask *mask;
-    const struct TALER_Extension *ext
-      = &pkd->extensions[i];
+    const struct TALER_Extension *ext = &pkd->extensions[i];
 
     switch (ext->type)
     {
     // TODO: case TALER_Extension_Peer2Peer
     case TALER_Extension_AgeRestriction:
-      mask = (struct TALER_AgeMask *) (&ext->config);
-      config = GNUNET_JSON_PACK (GNUNET_JSON_pack_data_auto ("mask",
-                                                             &mask->mask));
+      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:
@@ -177,22 +178,22 @@ TALER_EXCHANGE_management_post_extensions (
                    json_array_append_new (
                      extensions,
                      GNUNET_JSON_PACK (
-                       GNUNET_JSON_pack_data_auto ("extension",
+                       GNUNET_JSON_pack_data_auto ("name",
                                                    &ext->name),
                        GNUNET_JSON_pack_data_auto ("config",
                                                    config)
                        )));
   }
-  extension_sigs = json_array ();
-  GNUNET_assert (NULL != extension_sigs);
+  extensions_sigs = json_array ();
+  GNUNET_assert (NULL != extensions_sigs);
   for (unsigned int i = 0; i<pkd->num_extensions; i++)
   {
     const struct TALER_MasterSignatureP *sks
-      = &pkd->extension_sigs[i];
+      = &pkd->extensions_sigs[i];
 
     GNUNET_assert (0 ==
                    json_array_append_new (
-                     extension_sigs,
+                     extensions_sigs,
                      GNUNET_JSON_PACK (
                        GNUNET_JSON_pack_data_auto ("extension_sig",
                                                    &sks->eddsa_signature))));
@@ -200,8 +201,8 @@ TALER_EXCHANGE_management_post_extensions (
   body = GNUNET_JSON_PACK (
     GNUNET_JSON_pack_array_steal ("extensions",
                                   extensions),
-    GNUNET_JSON_pack_array_steal ("extension_sigs",
-                                  extension_sigs));
+    GNUNET_JSON_pack_array_steal ("extensions_sigs",
+                                  extensions_sigs));
   eh = curl_easy_init ();
   GNUNET_assert (NULL != eh);
   if (GNUNET_OK !=
diff --git a/src/util/extension_age_restriction.c b/src/util/extension_age_restriction.c
index fbdb796f2..c0efd7cd1 100644
--- a/src/util/extension_age_restriction.c
+++ b/src/util/extension_age_restriction.c
@@ -38,12 +38,12 @@ TALER_get_age_mask (const struct GNUNET_CONFIGURATION_Handle *cfg,
   char *groups;
   enum TALER_Extension_ReturnValue ret = TALER_Extension_ERROR_SYS;
 
-  if ((GNUNET_NO == GNUNET_CONFIGURATION_have_value (cfg,
-                                                     TALER_EXTENSION_SECTION_AGE_RESTRICTION,
-                                                     "ENABLED")) ||
-      (GNUNET_NO == GNUNET_CONFIGURATION_get_value_yesno (cfg,
-                                                          TALER_EXTENSION_SECTION_AGE_RESTRICTION,
-                                                          "ENABLED")))
+  if ((GNUNET_YES != GNUNET_CONFIGURATION_have_value (cfg,
+                                                      TALER_EXTENSION_SECTION_AGE_RESTRICTION,
+                                                      "ENABLED")) ||
+      (GNUNET_YES != GNUNET_CONFIGURATION_get_value_yesno (cfg,
+                                                           TALER_EXTENSION_SECTION_AGE_RESTRICTION,
+                                                           "ENABLED")))
   {
     /* Age restriction is not enabled */
     mask->mask = 0;
diff --git a/src/util/offline_signatures.c b/src/util/offline_signatures.c
index cd9dceca5..7fbec826b 100644
--- a/src/util/offline_signatures.c
+++ b/src/util/offline_signatures.c
@@ -490,4 +490,67 @@ TALER_exchange_offline_wire_fee_verify (
 }
 
 
+void
+TALER_exchange_offline_extension_agemask_sign (
+  const struct TALER_AgeMask mask,
+  const struct TALER_MasterPrivateKeyP *master_priv,
+  struct TALER_MasterSignatureP *master_sig)
+{
+  struct TALER_MasterExtensionAgeRestrictionPS ar = {
+    .purpose.purpose = htonl (TALER_SIGNATURE_MASTER_EXTENSION),
+    .purpose.size = htonl (sizeof(ar)),
+    .mask = mask
+  };
+  GNUNET_CRYPTO_eddsa_sign (&master_priv->eddsa_priv,
+                            &ar,
+                            &master_sig->eddsa_signature);
+}
+
+
+enum GNUNET_GenericReturnValue
+TALER_exchange_offline_extension_agemask_verify (
+  const struct TALER_AgeMask mask,
+  const struct TALER_MasterPublicKeyP *master_pub,
+  const struct TALER_MasterSignatureP *master_sig
+  )
+{
+  struct TALER_MasterExtensionAgeRestrictionPS ar = {
+    .purpose.purpose = htonl (TALER_SIGNATURE_MASTER_EXTENSION),
+    .purpose.size = htonl (sizeof(ar)),
+    .mask = mask
+  };
+  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;
+}
+
+
+#endif
+
 /* end of offline_signatures.c */