support REFUNDS in transaction history in libtalerexchange

src/exchange-lib/exchange_api_common.c

@@ -44,6 +44,8 @@ TALER_EXCHANGE_verify_coin_history (const char *currency,
 {
   size_t len;
   size_t off;
+  int add;
+  struct TALER_Amount rtotal;
 
   if (NULL == history)
   {
@@ -58,6 +60,8 @@ TALER_EXCHANGE_verify_coin_history (const char *currency,
   }
   TALER_amount_get_zero (currency,
                          total);
+  TALER_amount_get_zero (currency,
+                         &rtotal);
   for (off=0;off<len;off++)
   {
     json_t *transaction;
@@ -89,6 +93,7 @@ TALER_EXCHANGE_verify_coin_history (const char *currency,
       GNUNET_break_op (0);
       return GNUNET_SYSERR;
     }
+    add = GNUNET_SYSERR;
     if (0 == strcasecmp (type,
                          "DEPOSIT"))
     {
@@ -128,6 +133,7 @@ TALER_EXCHANGE_verify_coin_history (const char *currency,
         GNUNET_JSON_parse_free (spec);
         return GNUNET_SYSERR;
       }
+      add = GNUNET_YES;
     }
     else if (0 == strcasecmp (type,
                               "MELT"))
@@ -167,6 +173,67 @@ TALER_EXCHANGE_verify_coin_history (const char *currency,
         GNUNET_JSON_parse_free (spec);
         return GNUNET_SYSERR;
       }
+      add = GNUNET_YES;
+    }
+    else if (0 == strcasecmp (type,
+                              "REFUND"))
+    {
+      const struct TALER_RefundRequestPS *rr;
+      struct TALER_Amount rr_amount;
+      struct TALER_Amount rr_fee;
+      struct TALER_Amount rr_delta;
+
+      if (details_size != sizeof (struct TALER_RefundRequestPS))
+      {
+        GNUNET_break_op (0);
+        GNUNET_JSON_parse_free (spec);
+        return GNUNET_SYSERR;
+      }
+      rr = (const struct TALER_RefundRequestPS *) details;
+      if (details_size != ntohl (rr->purpose.size))
+      {
+        GNUNET_break_op (0);
+        GNUNET_JSON_parse_free (spec);
+        return GNUNET_SYSERR;
+      }
+      if (GNUNET_OK !=
+          GNUNET_CRYPTO_eddsa_verify (TALER_SIGNATURE_MERCHANT_REFUND,
+                                      &rr->purpose,
+                                      &sig.eddsa_signature,
+                                      &rr->merchant.eddsa_pub))
+      {
+        GNUNET_break_op (0);
+        GNUNET_JSON_parse_free (spec);
+        return GNUNET_SYSERR;
+      }
+      TALER_amount_ntoh (&rr_amount,
+                         &rr->refund_amount);
+      TALER_amount_ntoh (&rr_fee,
+                         &rr->refund_fee);
+      if (GNUNET_OK !=
+          TALER_amount_subtract (&rr_delta,
+                                 &rr_amount,
+                                 &rr_fee))
+      {
+        GNUNET_break_op (0);
+        GNUNET_JSON_parse_free (spec);
+        return GNUNET_SYSERR;
+      }
+      if (0 != TALER_amount_cmp (&rr_delta,
+                                 &amount))
+      {
+        GNUNET_break_op (0);
+        GNUNET_JSON_parse_free (spec);
+        return GNUNET_SYSERR;
+      }
+      /* NOTE/FIXME: theoretically, we could also check that the given
+         transaction_id and merchant_pub and h_contract appear in the
+         history under deposits.  However, there is really no benefit
+         for the exchange to lie here, so not checking is probably OK
+         (an auditor ought to check, though). Then again, we similarly
+         had no reason to check the merchant's signature (other than a
+         well-formendess check). */
+      add = GNUNET_NO;
     }
     else
     {
@@ -175,6 +242,9 @@ TALER_EXCHANGE_verify_coin_history (const char *currency,
       GNUNET_JSON_parse_free (spec);
       return GNUNET_SYSERR;
     }
+    if (GNUNET_YES == add)
+    {
+      /* This amount should be added to the total */
       if (GNUNET_OK !=
           TALER_amount_add (total,
                             total,
@@ -185,8 +255,41 @@ TALER_EXCHANGE_verify_coin_history (const char *currency,
         GNUNET_JSON_parse_free (spec);
         return GNUNET_SYSERR;
       }
+    }
+    else
+    {
+      /* This amount should be subtracted from the total.
+
+         However, for the implementation, we first *add* up all of
+         these negative amounts, as we might get refunds before
+         deposits from a semi-evil exchange.  Then, at the end, we do
+         the subtraction by calculating "total = total - rtotal" */
+      GNUNET_assert (GNUNET_NO == add);
+      if (GNUNET_OK !=
+          TALER_amount_add (&rtotal,
+                            &rtotal,
+                            &amount))
+      {
+        /* overflow in refund history? inconceivable! Bad exchange! */
+        GNUNET_break_op (0);
+        GNUNET_JSON_parse_free (spec);
+        return GNUNET_SYSERR;
+      }
+    }
     GNUNET_JSON_parse_free (spec);
   }
+
+  /* Finally, subtract 'rtotal' from total to handle the subtractions */
+  if (GNUNET_OK !=
+      TALER_amount_subtract (total,
+                             total,
+                             &rtotal))
+  {
+    /* underflow in history? inconceivable! Bad exchange! */
+    GNUNET_break_op (0);
+    return GNUNET_SYSERR;
+  }
+
   return GNUNET_OK;
 }
 

src/exchange/taler-exchange-httpd_responses.c

@@ -408,7 +408,7 @@ compile_transaction_history (const struct TALER_EXCHANGEDB_TransactionList *tl)
   const char *type;
   struct TALER_Amount value;
   json_t *history;
-  const struct TALER_CoinSpendSignatureP *sig;
+  const struct GNUNET_CRYPTO_EddsaSignature *sig;
   const struct TALER_EXCHANGEDB_TransactionList *pos;
 
   history = json_array ();
@@ -436,12 +436,12 @@ compile_transaction_history (const struct TALER_EXCHANGEDB_TransactionList *tl)
                            &deposit->deposit_fee);
         dr.merchant = deposit->merchant_pub;
         dr.coin_pub = deposit->coin.coin_pub;
-        sig = &deposit->csig;
+        sig = &deposit->csig.eddsa_signature;
 	/* internal sanity check before we hand out a bogus sig... */
         if (GNUNET_OK !=
             GNUNET_CRYPTO_eddsa_verify (TALER_SIGNATURE_WALLET_COIN_DEPOSIT,
                                         &dr.purpose,
-                                        &sig->eddsa_signature,
+                                        sig,
                                         &deposit->coin.coin_pub.eddsa_pub))
 	{
 	  GNUNET_break (0);
@@ -468,12 +468,12 @@ compile_transaction_history (const struct TALER_EXCHANGEDB_TransactionList *tl)
         TALER_amount_hton (&ms.melt_fee,
                            &melt->melt_fee);
         ms.coin_pub = melt->coin.coin_pub;
-        sig = &melt->coin_sig;
+        sig = &melt->coin_sig.eddsa_signature;
 	/* internal sanity check before we hand out a bogus sig... */
         if (GNUNET_OK !=
             GNUNET_CRYPTO_eddsa_verify (TALER_SIGNATURE_WALLET_COIN_MELT,
                                         &ms.purpose,
-                                        &sig->eddsa_signature,
+                                        sig,
                                         &melt->coin.coin_pub.eddsa_pub))
 	{
 	  GNUNET_break (0);
@@ -485,6 +485,48 @@ compile_transaction_history (const struct TALER_EXCHANGEDB_TransactionList *tl)
                                         sizeof (struct TALER_RefreshMeltCoinAffirmationPS));
       }
       break;
+    case TALER_EXCHANGEDB_TT_REFUND:
+      {
+        struct TALER_RefundRequestPS rr;
+        const struct TALER_EXCHANGEDB_Refund *refund = pos->details.refund;
+
+        type = "REFUND";
+        if (GNUNET_OK !=
+            TALER_amount_subtract (&value,
+                                   &refund->refund_amount,
+                                   &refund->refund_fee))
+        {
+	  GNUNET_break (0);
+	  json_decref (history);
+	  return NULL;
+        }
+        rr.purpose.purpose = htonl (TALER_SIGNATURE_MERCHANT_REFUND);
+        rr.purpose.size = htonl (sizeof (struct TALER_RefundRequestPS));
+        rr.h_contract = refund->h_contract;
+        rr.transaction_id = GNUNET_htonll (refund->transaction_id);
+        rr.coin_pub = refund->coin.coin_pub;
+        rr.merchant = refund->merchant_pub;
+        rr.rtransaction_id = GNUNET_htonll (refund->rtransaction_id);
+        TALER_amount_hton (&rr.refund_amount,
+                           &refund->refund_amount);
+        TALER_amount_hton (&rr.refund_fee,
+                           &refund->refund_fee);
+	/* internal sanity check before we hand out a bogus sig... */
+        if (GNUNET_OK !=
+            GNUNET_CRYPTO_eddsa_verify (TALER_SIGNATURE_MERCHANT_REFUND,
+                                        &rr.purpose,
+                                        sig,
+                                        &refund->merchant_pub.eddsa_pub))
+	{
+	  GNUNET_break (0);
+	  json_decref (history);
+	  return NULL;
+	}
+        sig = &refund->merchant_sig.eddsa_sig;
+        details = GNUNET_JSON_from_data (&rr.purpose,
+                                         sizeof (struct TALER_RefundRequestPS));
+      }
+      break;
     default:
       GNUNET_assert (0);
     }
@@ -493,7 +535,7 @@ compile_transaction_history (const struct TALER_EXCHANGEDB_TransactionList *tl)
                                       "type", type,
                                       "amount", TALER_JSON_from_amount (&value),
                                       "signature", GNUNET_JSON_from_data (sig,
-                                                                         sizeof (struct TALER_CoinSpendSignatureP)),
+                                                                          sizeof (struct GNUNET_CRYPTO_EddsaSignature)),
                                       "details", details));
   }
   return history;