From: Bodo Möller <bodo@openssl.org>
Date: Mon, 23 Jun 2008 20:46:28 +0000 (+0000)
Subject: avoid potential infinite loop in final reduction round of BN_GF2m_mod_arr()
X-Git-Tag: OpenSSL_0_9_8i~38
X-Git-Url: https://git.librecmc.org/?a=commitdiff_plain;h=4afcee8b4b9d2837796d4f663086eb5a99bb7204;p=oweals%2Fopenssl.git

avoid potential infinite loop in final reduction round of BN_GF2m_mod_arr()

Submitted by: Huang Ying
Reviewed by: Douglas Stebila
---

diff --git a/CHANGES b/CHANGES
index 826a29e666..b78c8d1012 100644
--- a/CHANGES
+++ b/CHANGES
@@ -4,12 +4,16 @@
 
  Changes between 0.9.8h and 0.9.8i  [xx XXX xxxx]
 
+  *) Fix BN_GF2m_mod_arr() top-bit cleanup code.
+     [Huang Ying]
+
   *) Expand ENGINE to support engine supplied SSL client certificate functions.
 
      This work was sponsored by Logica.
      [Steve Henson]
 
-  *) Add CryptoAPI ENGINE to support use of RSA and DSA keys held in Windows         keystores. Support for SSL/TLS client authentication too.
+  *) Add CryptoAPI ENGINE to support use of RSA and DSA keys held in Windows
+     keystores. Support for SSL/TLS client authentication too.
      Not compiled unless enable-capieng specified to Configure.
 
      This work was sponsored by Logica.
diff --git a/crypto/bn/bn_gf2m.c b/crypto/bn/bn_gf2m.c
index 6a793857e1..306f029f27 100644
--- a/crypto/bn/bn_gf2m.c
+++ b/crypto/bn/bn_gf2m.c
@@ -384,7 +384,11 @@ int BN_GF2m_mod_arr(BIGNUM *r, const BIGNUM *a, const unsigned int p[])
 		if (zz == 0) break;
 		d1 = BN_BITS2 - d0;
 		
-		if (d0) z[dN] = (z[dN] << d1) >> d1; /* clear up the top d1 bits */
+		/* clear up the top d1 bits */
+		if (d0)
+			z[dN] = (z[dN] << d1) >> d1;
+		else
+			z[dN] = 0;
 		z[0] ^= zz; /* reduction t^0 component */
 
 		for (k = 1; p[k] != 0; k++)