From: Emilia Kasper <emilia@openssl.org>
Date: Mon, 1 Dec 2014 14:04:02 +0000 (+0100)
Subject: Reject elliptic curve lists of odd lengths.
X-Git-Tag: master-post-reformat~226
X-Git-Url: https://git.openssl.org/gitweb/?p=openssl.git;a=commitdiff_plain;h=33d5ba862939ff8db70a9e36fc9a326fab3e8d98

Reject elliptic curve lists of odd lengths.

The Supported Elliptic Curves extension contains a vector of NamedCurves
of 2 bytes each, so the total length must be even. Accepting odd-length
lists was observed to lead to a non-exploitable one-byte out-of-bounds
read in the latest development branches (1.0.2 and master). Released
versions of OpenSSL are not affected.

Thanks to Felix Groebert of the Google Security Team for reporting this issue.

Reviewed-by: Matt Caswell <matt@openssl.org>
---

diff --git a/ssl/t1_lib.c b/ssl/t1_lib.c
index e0f28d254b..c5c8bb95f3 100644
--- a/ssl/t1_lib.c
+++ b/ssl/t1_lib.c
@@ -2155,7 +2155,9 @@ static int ssl_scan_clienthello_tlsext(SSL *s, unsigned char **p, unsigned char
 			ellipticcurvelist_length += (*(sdata++));
 
 			if (ellipticcurvelist_length != size - 2 ||
-				ellipticcurvelist_length < 1)
+				ellipticcurvelist_length < 1 ||
+				/* Each NamedCurve is 2 bytes. */
+				ellipticcurvelist_length & 1)
 				{
 				*al = TLS1_AD_DECODE_ERROR;
 				return 0;