Fix overread when verifying SERVER_HELLO in DTLS
diff --git a/ChangeLog b/ChangeLog
index 1e882ef..def7e6d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -25,6 +25,8 @@
* Fix documentation and implementation missmatch for function arguments of
mbedtls_gcm_finish(). Found by cmiatpaar. #602
* Guarantee that P>Q at RSA key generation. Found by inestlerode. #558
+ * Fix potential byte overread when verifying malformed SERVER_HELLO in
+ ssl_parse_hello_verify_request() for DTLS. Found by Guido Vranken.
= mbed TLS 2.1.5 branch released 2016-06-28
diff --git a/library/ssl_cli.c b/library/ssl_cli.c
index 16fd43b..3d7283c 100644
--- a/library/ssl_cli.c
+++ b/library/ssl_cli.c
@@ -1226,6 +1226,15 @@
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,
+ ( "cookie length does not match incoming message size" ) );
+ mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
+ MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR );
+ return( MBEDTLS_ERR_SSL_BAD_HS_SERVER_HELLO );
+ }
+
mbedtls_free( ssl->handshake->verify_cookie );
ssl->handshake->verify_cookie = mbedtls_calloc( 1, cookie_len );