[age restriction] progress 14/n - withdraw and deposit

Age restriction support for
  - withdraw is done and tested
  - deposit is done and tested

TODOs:
  - melt/refresh/reveal
  - link

------

Added functions
 - TALER_age_restriction_commit
 - TALER_age_commitment_derive
 - TALER_age_commitment_hash
 - TALER_age_restriction_commitment_free_inside
 - Hash of age commitment passed around API boundaries

Exchangedb adjustments for denominations
 - all prepared statements re: denominations now handle age_mask
 - signature parameters adjusted

Hash and signature verification of /keys adjusted
 - Hashes of (normal) denominations and age-restricted denominations are
   calculated seperately
 - The hash of the age-restricted ones will then be added to the other
   hash
 - The total hash is signed/verified

Tests for withdraw with age restriction added
 - TALER_EXCHANGE_DenomPublickey now carries age_mask
 - TALER_TESTING_cmd_withdraw_amount* takes age parameter
 - TALER_TESTING_find_pk takes boolean age_restricted
 - WithdrawState carries age_commitment and its hash
 - withdraw_run derives new age commitment, if applicable
 - Added age parameter to testing (13 as example)

Various Fixes and changes
 - Fixes of post handler for /management/extensions
 - Fixes for offline tool extensions signing
 - Slight refactoring of extensions
 - Age restriction extension simplified
   - config is now global to extension
   - added global TEH_age_restriction_enabled and TEH_age_mask in
     taler-exchange-httpd
   - helper functions and macros introduced

1 files changed, 36 insertions, 22 deletions

diff --git a/src/lib/exchange_api_handle.c b/src/lib/exchange_api_handle.c
index cf3d69d6a..3243f5e95 100644
--- a/src/lib/exchange_api_handle.c
+++ b/src/lib/exchange_api_handle.c
@@ -667,7 +667,9 @@ decode_keys_json (const json_t *resp_obj,
                   enum TALER_EXCHANGE_VersionCompatibility *vc)
 {
   struct TALER_ExchangeSignatureP sig;
-  struct GNUNET_HashContext *hash_context;
+  struct GNUNET_HashContext *hash_context = NULL;
+  struct GNUNET_HashContext *hash_context_restricted = NULL;
+  bool have_age_restricted_denom = false;
   struct TALER_ExchangePublicKeyP pub;
   const char *currency;
   struct GNUNET_JSON_Specification mspec[] = {
@@ -746,7 +748,6 @@ decode_keys_json (const json_t *resp_obj,
     key_data->version = GNUNET_strdup (ver);
   }
 
-  hash_context = NULL;
   EXITIF (GNUNET_OK !=
           GNUNET_JSON_parse (resp_obj,
                              (check_sig) ? mspec : &mspec[2],
@@ -766,7 +767,10 @@ decode_keys_json (const json_t *resp_obj,
 
   /* parse the master public key and issue date of the response */
   if (check_sig)
+  {
     hash_context = GNUNET_CRYPTO_hash_context_start ();
+    hash_context_restricted = GNUNET_CRYPTO_hash_context_start ();
+  }
 
   /* parse the signing keys */
   {
@@ -829,6 +833,9 @@ decode_keys_json (const json_t *resp_obj,
       EXITIF (GNUNET_OK !=
               TALER_extensions_load_json_config (extensions));
     }
+
+    /* 4. assuming we might have now a new value for age_mask, set it in key_data */
+    key_data->age_mask = TALER_extensions_age_restriction_ageMask ();
   }
 
   /* parse the denomination keys, merging with the
@@ -839,9 +846,15 @@ decode_keys_json (const json_t *resp_obj,
      */
     struct
     { char *name;
-      bool is_optional_age_restriction;} hive[2] = {
-      { "denoms",                false },
-      { "age_restricted_denoms", true  },
+      struct GNUNET_HashContext *hc;
+      bool is_optional_age_restriction;}
+    hive[2] = {
+      { "denoms",
+        hash_context,
+        false },
+      { "age_restricted_denoms",
+        hash_context_restricted,
+        true  }
     };
 
     for (size_t s = 0; s < sizeof(hive) / sizeof(hive[0]); s++)
@@ -853,25 +866,19 @@ decode_keys_json (const json_t *resp_obj,
       denom_keys_array = json_object_get (resp_obj,
                                           hive[s].name);
 
-      EXITIF (NULL == denom_keys_array &&
-              ! hive[s].is_optional_age_restriction);
-
-      if (NULL == denom_keys_array &&
-          hive[s].is_optional_age_restriction)
+      if (NULL == denom_keys_array)
         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) {
         struct TALER_EXCHANGE_DenomPublicKey dk;
         bool found = false;
 
+        /* mark that we have at least one age restricted denomination, needed
+         * for the hash calculation and signature verification below. */
+        have_age_restricted_denom |= hive[s].is_optional_age_restriction;
+
         memset (&dk,
                 0,
                 sizeof (dk));
@@ -880,12 +887,7 @@ decode_keys_json (const json_t *resp_obj,
                                      check_sig,
                                      denom_key_obj,
                                      &key_data->master_pub,
-                                     hash_context));
-
-        /* Mark age restriction according where we got this denomination from,
-         * "denoms" or "age_restricted_denoms" */
-        if (hive[s].is_optional_age_restriction)
-          dk.age_restricted = true;
+                                     hive[s].hc));
 
         for (unsigned int j = 0;
              j<key_data->num_denom_keys;
@@ -1044,6 +1046,18 @@ decode_keys_json (const json_t *resp_obj,
       .list_issue_date = GNUNET_TIME_timestamp_hton (key_data->list_issue_date)
     };
 
+    /* If we had any age restricted denominations, add their hash to the end of
+     * the normal denominations. */
+    if (have_age_restricted_denom)
+    {
+      struct GNUNET_HashCode hcr;
+      GNUNET_CRYPTO_hash_context_finish (hash_context_restricted,
+                                         &hcr);
+      GNUNET_CRYPTO_hash_context_read (hash_context,
+                                       &hcr,
+                                       sizeof(struct GNUNET_HashCode));
+    }
+
     GNUNET_CRYPTO_hash_context_finish (hash_context,
                                        &ks.hc);
     hash_context = NULL;