parse age-restriction info from /keys

- parse "age_restriction" extension, extract mask for age groups
- parse denoms from "age_restricted_denoms", too, if available

src/include/taler_exchange_service.h

@@ -287,6 +287,11 @@ struct TALER_EXCHANGE_Keys
    */
   struct GNUNET_TIME_Timestamp last_denom_issue_date;
 
+  /**
+   * If age restriction is enabled on the exchange, we get an non-zero age_mask
+   */
+  struct TALER_AgeMask age_mask;
+
   /**
    * Length of the @e sign_keys array (number of valid entries).
    */

src/include/taler_extensions.h

@@ -110,7 +110,7 @@ TALER_extension_get_by_name (const char *name,
  * @return Error, if age groups were invalid, OK otherwise.
  */
 enum TALER_Extension_ReturnValue
-TALER_parse_age_group_string (char *groups,
+TALER_parse_age_group_string (const char *groups,
                               struct TALER_AgeMask *mask);
 
 /**

src/lib/exchange_api_handle.c

@@ -30,6 +30,7 @@
 #include "taler_exchange_service.h"
 #include "taler_auditor_service.h"
 #include "taler_signatures.h"
+#include "taler_extensions.h"
 #include "exchange_api_handle.h"
 #include "exchange_api_curl_defaults.h"
 #include "backoff.h"
@@ -762,6 +763,7 @@ decode_keys_json (const json_t *resp_obj,
       return GNUNET_SYSERR;
     }
   }
+
   /* parse the master public key and issue date of the response */
   if (check_sig)
     hash_context = GNUNET_CRYPTO_hash_context_start ();
@@ -792,36 +794,89 @@ decode_keys_json (const json_t *resp_obj,
     }
   }
 
+  /* Parse the supported extension(s): age-restriction. */
+  /* TODO: maybe lift this into a FP in TALER_Extension ? */
+  {
+    json_t *age_restriction = json_object_get (resp_obj,
+                                               "age_restriction");
+
+    if (NULL != age_restriction)
+    {
+      bool critical;
+      const char *version;
+      const char *age_groups;
+      struct GNUNET_JSON_Specification spec[] = {
+        GNUNET_JSON_spec_bool ("critical",
+                               &critical),
+        GNUNET_JSON_spec_string ("version",
+                                 &version),
+        GNUNET_JSON_spec_string ("age_groups",
+                                 &age_groups),
+        GNUNET_JSON_spec_end ()
+      };
+
+      if (GNUNET_OK !=
+          GNUNET_JSON_parse (age_restriction,
+                             spec,
+                             NULL, NULL))
+      {
+        GNUNET_break_op (0);
+        return GNUNET_SYSERR;
+      }
+
+      if (critical || // do we care?
+          0 != strncmp (version, "1", 1) ) /* TODO: better compatibility check */
+      {
+        GNUNET_break_op (0);
+        return GNUNET_SYSERR;
+      }
+
+      if (TALER_Extension_OK !=
+          TALER_parse_age_group_string (age_groups,
+                                        &key_data->age_mask))
+      {
+        // TODO: print more specific error?
+        GNUNET_break_op (0);
+        return GNUNET_SYSERR;
+      }
+    }
+  }
+
   /* parse the denomination keys, merging with the
      possibly EXISTING array as required (/keys cherry picking) */
   {
+    /* The denominations can be in "denoms" and (optionally) in
+     * "age_restricted_denoms"
+     */
     struct
-    {
-      char *name;
-      bool is_optional_age_restriction;
-    } section[2] = {
-      /* The denominations can be in "denoms" or in
-       * "age_restricted_denoms", the later being optional */
+    { char *name;
+      bool is_optional_age_restriction;} hive[2] = {
       { "denoms",                false },
       { "age_restricted_denoms", true  },
     };
 
-    for (size_t s = 0; s < sizeof(section) / sizeof(section[0]); s++)
+    for (size_t s = 0; s < sizeof(hive) / sizeof(hive[0]); s++)
     {
       json_t *denom_keys_array;
       json_t *denom_key_obj;
       unsigned int index;
 
       denom_keys_array = json_object_get (resp_obj,
-                                          section[s].name);
+                                          hive[s].name);
 
       EXITIF (NULL == denom_keys_array &&
-              ! section[s].is_optional_age_restriction);
+              ! hive[s].is_optional_age_restriction);
 
       if (NULL == denom_keys_array &&
-          section[s].is_optional_age_restriction)
+          hive[s].is_optional_age_restriction)
         continue;
 
+      /* if "age_restricted_denoms" exists, age-restriction better be enabled
+       * (that is: mask non-zero) */
+      EXITIF (NULL != denom_keys_array &&
+              hive[s].is_optional_age_restriction &&
+              0 == key_data->age_mask.mask);
+
       EXITIF (JSON_ARRAY != json_typeof (denom_keys_array));
 
       json_array_foreach (denom_keys_array, index, denom_key_obj) {
@@ -840,7 +895,7 @@ decode_keys_json (const json_t *resp_obj,
 
         /* Mark age restriction according where we got this denomination from,
          * "denoms" or "age_restricted_denoms" */
-        if (section[s].is_optional_age_restriction)
+        if (hive[s].is_optional_age_restriction)
           dk.age_restricted = true;
 
         for (unsigned int j = 0;

src/util/extension_age_restriction.c

@@ -80,7 +80,7 @@ TALER_get_age_mask (const struct GNUNET_CONFIGURATION_Handle *cfg,
  * @return Error if string was invalid, OK otherwise.
  */
 enum TALER_Extension_ReturnValue
-TALER_parse_age_group_string (char *groups,
+TALER_parse_age_group_string (const char *groups,
                               struct TALER_AgeMask *mask)
 {
   enum TALER_Extension_ReturnValue ret = TALER_Extension_ERROR_SYS;