From cd53cdbc3774fb193bdebcdc5d7019ddebc16dbc Mon Sep 17 00:00:00 2001
From: Werner Koch <wk@gnupg.org>
Date: Thu, 11 Sep 2014 17:06:16 +0200
Subject: mpi: Improve mpi_invm to detect bad input.

* mpi/mpi-inv.c (mpi_invm): Return 0 for bad input.
--

Without this patch the function may enter an endless loop.  This is a
backport from libgcrypt.

GnuPG-bug-id: 1713
---
 mpi/mpi-inv.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/mpi/mpi-inv.c b/mpi/mpi-inv.c
index b76263047..361c57ea4 100644
--- a/mpi/mpi-inv.c
+++ b/mpi/mpi-inv.c
@@ -165,6 +165,11 @@ mpi_invm( MPI x, MPI a, MPI n )
     int sign;
     int odd ;
 
+    if (!mpi_cmp_ui (a, 0))
+        return 0; /* Inverse does not exists.  */
+    if (!mpi_cmp_ui (n, 1))
+        return 0; /* Inverse does not exists.  */
+
     u = mpi_copy(a);
     v = mpi_copy(n);
 
-- 
cgit v1.2.3