From: simon <simon@cda61777-01e9-0310-a592-d414129be87e>
Date: Mon, 5 Aug 2013 19:50:51 +0000 (+0000)
Subject: The bignum code has two representations of zero, since
X-Git-Url: https://git.distorted.org.uk/u/mdw/putty/commitdiff_plain/434a1d60dbb7311c85e957dfd02c9b8bafaa2c44

The bignum code has two representations of zero, since
bn_restore_invariant (and the many loops that duplicate it) leaves a
single zero word in a bignum representing 0, whereas the constant
'Zero' does not have any data words at all. Cope with this in
bignum_cmp.

(It would be a better plan to decide on one representation and stick
with it, but this is the less disruptive fix for the moment.)


git-svn-id: svn://svn.tartarus.org/sgt/putty@9996 cda61777-01e9-0310-a592-d414129be87e
---

diff --git a/sshbn.c b/sshbn.c
index cbd710d5..1c5c46a1 100644
--- a/sshbn.c
+++ b/sshbn.c
@@ -1322,6 +1322,12 @@ int bignum_cmp(Bignum a, Bignum b)
     int amax = a[0], bmax = b[0];
     int i;
 
+    /* Annoyingly we have two representations of zero */
+    if (amax == 1 && a[amax] == 0)
+        amax = 0;
+    if (bmax == 1 && b[bmax] == 0)
+        bmax = 0;
+
     assert(amax == 0 || a[amax] != 0);
     assert(bmax == 0 || b[bmax] != 0);