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From baaabfd8fdcec04a691695fad9a664bea43202b6 Mon Sep 17 00:00:00 2001
From: "Dr. Stephen Henson" <steve@openssl.org>
Date: Tue, 23 Aug 2016 18:14:54 +0100
Subject: [PATCH] Sanity check ticket length.
If a ticket callback changes the HMAC digest to SHA512 the existing
sanity checks are not sufficient and an attacker could perform a DoS
attack with a malformed ticket. Add additional checks based on
HMAC size.
Thanks to Shi Lei for reporting this bug.
CVE-2016-6302
Reviewed-by: Rich Salz <rsalz@openssl.org>
Upstream-Status: Backport
CVE: CVE-2016-6302
Signed-off-by: Armin Kuster <akuster@mvista.com>
---
ssl/t1_lib.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
Index: openssl-1.0.2h/ssl/t1_lib.c
===================================================================
--- openssl-1.0.2h.orig/ssl/t1_lib.c
+++ openssl-1.0.2h/ssl/t1_lib.c
@@ -3397,9 +3397,7 @@ static int tls_decrypt_ticket(SSL *s, co
HMAC_CTX hctx;
EVP_CIPHER_CTX ctx;
SSL_CTX *tctx = s->initial_ctx;
- /* Need at least keyname + iv + some encrypted data */
- if (eticklen < 48)
- return 2;
+
/* Initialize session ticket encryption and HMAC contexts */
HMAC_CTX_init(&hctx);
EVP_CIPHER_CTX_init(&ctx);
@@ -3433,6 +3431,13 @@ static int tls_decrypt_ticket(SSL *s, co
if (mlen < 0) {
goto err;
}
+ /* Sanity check ticket length: must exceed keyname + IV + HMAC */
+ if (eticklen <= 16 + EVP_CIPHER_CTX_iv_length(&ctx) + mlen) {
+ HMAC_CTX_cleanup(&hctx);
+ EVP_CIPHER_CTX_cleanup(&ctx);
+ return 2;
+ }
+
eticklen -= mlen;
/* Check HMAC of encrypted ticket */
if (HMAC_Update(&hctx, etick, eticklen) <= 0
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