From 01a96d6fd28996b0290d14dd853969d61be13184 Mon Sep 17 00:00:00 2001 From: Gilles Peskine Date: Fri, 27 Sep 2019 14:00:36 +0200 Subject: [PATCH] Parse HelloVerifyRequest: avoid buffer overread on the cookie In ssl_parse_hello_verify_request, we print cookie_len bytes without checking that there are that many bytes left in ssl->in_msg. This could potentially log data outside the received message (not a big deal) and could potentially read from memory outside of the receive buffer (which would be a remotely exploitable crash). --- library/ssl_cli.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/library/ssl_cli.c b/library/ssl_cli.c index afced7a99..eeedfe6cc 100644 --- a/library/ssl_cli.c +++ b/library/ssl_cli.c @@ -1445,8 +1445,6 @@ static int ssl_parse_hello_verify_request( mbedtls_ssl_context *ssl ) } cookie_len = *p++; - MBEDTLS_SSL_DEBUG_BUF( 3, "cookie", p, cookie_len ); - if( ( ssl->in_msg + ssl->in_msglen ) - p < cookie_len ) { MBEDTLS_SSL_DEBUG_MSG( 1, @@ -1455,6 +1453,7 @@ static int ssl_parse_hello_verify_request( mbedtls_ssl_context *ssl ) MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR ); return( MBEDTLS_ERR_SSL_BAD_HS_SERVER_HELLO ); } + MBEDTLS_SSL_DEBUG_BUF( 3, "cookie", p, cookie_len ); mbedtls_free( ssl->handshake->verify_cookie );