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From ea39b16b71e4e72a228a4535bd6d6a02c5edbc1f Mon Sep 17 00:00:00 2001
From: Matt Caswell <matt@openssl.org>
Date: Fri, 9 Sep 2016 10:08:45 +0100
Subject: [PATCH] Fix OCSP Status Request extension unbounded memory growth
A malicious client can send an excessively large OCSP Status Request
extension. If that client continually requests renegotiation,
sending a large OCSP Status Request extension each time, then there will
be unbounded memory growth on the server. This will eventually lead to a
Denial Of Service attack through memory exhaustion. Servers with a
default configuration are vulnerable even if they do not support OCSP.
Builds using the "no-ocsp" build time option are not affected.
I have also checked other extensions to see if they suffer from a similar
problem but I could not find any other issues.
CVE-2016-6304
Issue reported by Shi Lei.
Reviewed-by: Rich Salz <rsalz@openssl.org>
Upstream-Status: Backport
CVE: CVE-2016-6304
Signed-off-by: Armin Kuster <akuster@mvista.com>
---
ssl/t1_lib.c | 24 +++++++++++++++++-------
1 file changed, 17 insertions(+), 7 deletions(-)
diff --git a/ssl/t1_lib.c b/ssl/t1_lib.c
index fbcf2e6..e4b4e27 100644
--- a/ssl/t1_lib.c
+++ b/ssl/t1_lib.c
@@ -2316,6 +2316,23 @@ static int ssl_scan_clienthello_tlsext(SSL *s, unsigned char **p,
size -= 2;
if (dsize > size)
goto err;
+
+ /*
+ * We remove any OCSP_RESPIDs from a previous handshake
+ * to prevent unbounded memory growth - CVE-2016-6304
+ */
+ sk_OCSP_RESPID_pop_free(s->tlsext_ocsp_ids,
+ OCSP_RESPID_free);
+ if (dsize > 0) {
+ s->tlsext_ocsp_ids = sk_OCSP_RESPID_new_null();
+ if (s->tlsext_ocsp_ids == NULL) {
+ *al = SSL_AD_INTERNAL_ERROR;
+ return 0;
+ }
+ } else {
+ s->tlsext_ocsp_ids = NULL;
+ }
+
while (dsize > 0) {
OCSP_RESPID *id;
int idsize;
@@ -2335,13 +2352,6 @@ static int ssl_scan_clienthello_tlsext(SSL *s, unsigned char **p,
OCSP_RESPID_free(id);
goto err;
}
- if (!s->tlsext_ocsp_ids
- && !(s->tlsext_ocsp_ids =
- sk_OCSP_RESPID_new_null())) {
- OCSP_RESPID_free(id);
- *al = SSL_AD_INTERNAL_ERROR;
- return 0;
- }
if (!sk_OCSP_RESPID_push(s->tlsext_ocsp_ids, id)) {
OCSP_RESPID_free(id);
*al = SSL_AD_INTERNAL_ERROR;
--
2.7.4
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