From 84998f9d052d49839a3bba75a91c3419acd87a86 Mon Sep 17 00:00:00 2001
From: Christian Grothoff <christian@grothoff.org>
Date: Thu, 2 Nov 2017 17:40:14 +0100
Subject: [PATCH] fix #5167

---
 ChangeLog         |  3 +++
 src/util/amount.c | 49 +++++++++++++++++++++++++++++++----------------
 2 files changed, 35 insertions(+), 17 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 80697eed5..2948a76c7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,6 @@
+Thu Nov  2 17:39:40 CET 2017
+	Limit amount values to 2^53 as we always wanted (#5167). -CG
+
 Thu Nov  2 16:50:46 CET 2017
 	Fixing serious bug in reserve balance calculations, as
 	fees were not always properly included in the summation. -CG
diff --git a/src/util/amount.c b/src/util/amount.c
index 33ba9a2f7..d52a32cf6 100644
--- a/src/util/amount.c
+++ b/src/util/amount.c
@@ -29,6 +29,25 @@
 #endif
 #include <gcrypt.h>
 
+/**
+ * Maximum legal 'value' for an amount, based on IEEE double (for JavaScript compatibility).
+ */
+#define MAX_AMOUNT_VALUE (1LLU << 53)
+
+
+/**
+ * Set @a a to "invalid".
+ *
+ * @param a amount to set to invalid
+ */
+static void
+invalidate (struct TALER_Amount *a)
+{
+  memset (a,
+          0,
+          sizeof (struct TALER_Amount));
+}
+
 
 /**
  * Parse money amount description, in the format "A:B.C".
@@ -48,9 +67,7 @@ TALER_string_to_amount (const char *str,
   const char *colon;
   const char *value;
 
-  memset (denom,
-          0,
-          sizeof (struct TALER_Amount));
+  invalidate (denom);
   /* skip leading whitespace */
   while (isspace( (unsigned char) str[0]))
     str++;
@@ -139,6 +156,12 @@ TALER_string_to_amount (const char *str,
     b /= 10;
     i++;
   }
+  if (denom->value > MAX_AMOUNT_VALUE)
+  {
+    /* too large to be legal */
+    invalidate (denom);
+    return GNUNET_SYSERR;
+  }
   return GNUNET_OK;
 
  fail:
@@ -237,20 +260,6 @@ TALER_amount_get_zero (const char *cur,
 }
 
 
-/**
- * Set @a a to "invalid".
- *
- * @param a amount to set to invalid
- */
-static void
-invalidate (struct TALER_Amount *a)
-{
-  memset (a,
-          0,
-          sizeof (struct TALER_Amount));
-}
-
-
 /**
  * Test if the given amount is valid.
  *
@@ -472,6 +481,12 @@ TALER_amount_add (struct TALER_Amount *sum,
     invalidate (sum);
     return GNUNET_SYSERR;
   }
+  if (res.value > MAX_AMOUNT_VALUE)
+  {
+    /* too large to be legal */
+    invalidate (sum);
+    return GNUNET_SYSERR;
+  }
   res.fraction = n1.fraction + n2.fraction;
   if (GNUNET_SYSERR ==
       TALER_amount_normalize (&res))