first steps on #5777

src/exchange/taler-exchange-httpd_keystate.c

@@ -1907,6 +1907,9 @@ TEH_KS_denomination_key_lookup_by_hash (const struct TEH_KS_StateHandle *key_sta
   map = (TEH_KS_DKU_PAYBACK == use) ? key_state->revoked_map : key_state->denomkey_map;
   dki = GNUNET_CONTAINER_multihashmap_get (map,
 					   denom_pub_hash);
+  if ( (NULL == dki) && (TEH_KS_DKU_ZOMBIE == use))
+    dki = GNUNET_CONTAINER_multihashmap_get (key_state->revoked_map,
+                                             denom_pub_hash);
   if (NULL == dki)
     return NULL;
   now = GNUNET_TIME_absolute_get ();
@@ -1958,6 +1961,16 @@ TEH_KS_denomination_key_lookup_by_hash (const struct TEH_KS_StateHandle *key_sta
       return NULL;
     }
     break;
+  case TEH_KS_DKU_ZOMBIE:
+    if (now.abs_value_us >
+	GNUNET_TIME_absolute_ntoh (dki->issue.properties.expire_legal).abs_value_us)
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+		  "Not returning DKI for %s, as legal expiration of coin has passed\n",
+		  GNUNET_h2s (denom_pub_hash));
+      return NULL;
+    }
+    break;
   }
   return dki;
 }

src/exchange/taler-exchange-httpd_keystate.h

@@ -109,7 +109,14 @@ enum TEH_KS_DenominationKeyUse {
   /**
    * The key is to be used for a /payback operation.
    */
-  TEH_KS_DKU_PAYBACK
+  TEH_KS_DKU_PAYBACK,
+
+  /**
+   * The key is to be used for a /refresh/payback operation,
+   * i.e. it is an old coin that regained value from a 
+   * payback on a new coin derived from the old coin.
+   */
+  TEH_KS_DKU_ZOMBIE
 
 };
 

src/exchange/taler-exchange-httpd_refresh_melt.c

@@ -1,6 +1,6 @@
 /*
   This file is part of TALER
-  Copyright (C) 2014-2019 Inria & GNUnet e.V.
+  Copyright (C) 2014-2019 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
@@ -453,9 +453,64 @@ TEH_REFRESH_handler_refresh_melt (struct TEH_RequestHandler *rh,
                                              "no keys");
     goto cleanup;
   }
+
+  /* Baseline: check if deposits/refreshs are generally
+     simply still allowed for this denomination */
   rmc.dki = TEH_KS_denomination_key_lookup_by_hash (key_state,
                                                     &rmc.refresh_session.coin.denom_pub_hash,
                                                     TEH_KS_DKU_DEPOSIT);
+  /* Consider case that denomination was revoked but
+     this coin was already seen and thus refresh is OK. */
+  if (NULL == rmc.dki)
+  {
+    struct TALER_EXCHANGEDB_DenominationKeyIssueInformation *dki;
+
+    dki = TEH_KS_denomination_key_lookup_by_hash (key_state,
+                                                  &rmc.refresh_session.coin.denom_pub_hash,
+                                                  TEH_KS_DKU_PAYBACK);
+    if (NULL != dki)
+    {
+      struct TALER_CoinPublicInfo coin_info;
+      enum GNUNET_DB_QueryStatus qs;
+
+      qs = TEH_plugin->get_known_coin (TEH_plugin->cls,
+                                       NULL,
+                                       &rmc.refresh_session.coin.coin_pub,
+                                       &coin_info);
+      if (0 > qs)
+      {
+        GNUNET_break (0);
+        res = TEH_RESPONSE_reply_internal_db_error (connection,
+                                                    TALER_EC_REFRESH_MELT_DB_FETCH_ERROR);
+        goto cleanup;
+      }
+      if (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT == qs)
+      {
+        /* Coin was known beforehand, so we should allow the refresh */
+        rmc.dki = dki;
+        GNUNET_CRYPTO_rsa_signature_free (coin_info.denom_sig.rsa_signature);
+      }
+    }
+  }
+
+  /* Consider the case that the denomination expired for deposits,
+     but /refresh/payback refilled the balance of the 'zombie' coin
+     and we should thus allow the refresh during the legal period. */
+  if (NULL == rmc.dki)
+  {
+    struct TALER_EXCHANGEDB_DenominationKeyIssueInformation *dki;
+
+    dki = TEH_KS_denomination_key_lookup_by_hash (key_state,
+                                                  &rmc.refresh_session.coin.denom_pub_hash,
+                                                  TEH_KS_DKU_ZOMBIE);
+    if (NULL != dki)
+    {
+      /* Test if zombie-condition is actually satisfied for the coin */
+      if (0 /* FIXME: test if zombie-satisfied */)
+        rmc.dki = dki;
+    }
+  }
+
   if (NULL == rmc.dki)
   {
     TALER_LOG_WARNING ("Unknown denomination key in /refresh/melt request\n");

src/exchangedb/plugin_exchangedb_postgres.c

@@ -3304,6 +3304,7 @@ postgres_get_known_coin (void *cls,
                          const struct TALER_CoinSpendPublicKeyP *coin_pub,
                          struct TALER_CoinPublicInfo *coin_info)
 {
+  struct PostgresClosure *pc = cls;
   struct GNUNET_PQ_QueryParam params[] = {
     GNUNET_PQ_query_param_auto_from_type (coin_pub),
     GNUNET_PQ_query_param_end
@@ -3320,6 +3321,8 @@ postgres_get_known_coin (void *cls,
               "Getting known coin data for coin %s\n",
               TALER_B2S (coin_pub));
   coin_info->coin_pub = *coin_pub;
+  if (NULL == session)
+    session = postgres_get_session (pc);
   return GNUNET_PQ_eval_prepared_singleton_select (session->conn,
 						   "get_known_coin",
 						   params,