Reject elliptic curve lists of odd lengths.
authorEmilia Kasper <emilia@openssl.org>
Mon, 1 Dec 2014 14:04:02 +0000 (15:04 +0100)
committerEmilia Kasper <emilia@openssl.org>
Fri, 5 Dec 2014 15:32:39 +0000 (16:32 +0100)
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>
ssl/t1_lib.c

index e0f28d2..c5c8bb9 100644 (file)
@@ -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;