From 8c7406cb42c6c9cc8967ab8cbfd901809c8b3c2e Mon Sep 17 00:00:00 2001
From: Christian Grothoff <christian@grothoff.org>
Date: Wed, 15 Jun 2016 20:09:09 +0200
Subject: check refresh amounts add up correctly, fix linker issue

---
 src/exchange-lib/exchange_api_refresh.c | 35 +++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

(limited to 'src/exchange-lib/exchange_api_refresh.c')

diff --git a/src/exchange-lib/exchange_api_refresh.c b/src/exchange-lib/exchange_api_refresh.c
index 9a9c6b7eb..e32f73e21 100644
--- a/src/exchange-lib/exchange_api_refresh.c
+++ b/src/exchange-lib/exchange_api_refresh.c
@@ -764,6 +764,7 @@ TALER_EXCHANGE_refresh_prepare (const struct TALER_CoinSpendPrivateKeyP *melt_pr
   unsigned int i;
   unsigned int j;
   struct GNUNET_HashContext *hash_context;
+  struct TALER_Amount total;
 
   /* build up melt data structure */
   for (i=0;i<TALER_CNC_KAPPA;i++)
@@ -799,10 +800,44 @@ TALER_EXCHANGE_refresh_prepare (const struct TALER_CoinSpendPrivateKeyP *melt_pr
     md.fresh_coins[i] = GNUNET_new_array (fresh_pks_len,
                                           struct FreshCoinP);
     for (j=0;j<fresh_pks_len;j++)
+    {
       setup_fresh_coin (&md.fresh_coins[i][j],
                         &fresh_pks[j]);
+    }
   }
 
+  /* verify that melt_amount is above total cost */
+  GNUNET_assert (GNUNET_OK ==
+		 TALER_amount_get_zero (melt_amount->currency,
+					&total));
+  for (j=0;j<fresh_pks_len;j++)
+  {
+    if ( (GNUNET_OK !=
+	  TALER_amount_add (&total,
+			    &total,
+			    &fresh_pks[j].value)) ||
+	 (GNUNET_OK !=
+	  TALER_amount_add (&total,
+			    &total,
+			    &fresh_pks[j].fee_withdraw)) )
+    {
+      GNUNET_break (0);
+      free_melt_data (&md);
+      return NULL;
+    }
+  }
+  if (1 ==
+      TALER_amount_cmp (&total,
+			melt_amount) )
+  {
+    /* Eh, this operation is more expensive than the 
+       @a melt_amount. This is not OK. */
+    GNUNET_break (0);
+    free_melt_data (&md);
+    return NULL;
+  }
+
+
   /* now compute melt session hash */
   hash_context = GNUNET_CRYPTO_hash_context_start ();
   for (i=0;i<fresh_pks_len;i++)
-- 
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