Fix heap-buffer overread in ALPN ext parsing
diff --git a/ChangeLog b/ChangeLog
index 3f5e56f..ef5abb8 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -38,6 +38,9 @@
corrupt 6 bytes on the peer's heap, potentially leading to crash or
remote code execution. This can be triggered remotely from either
side in both TLS and DTLS.
+ * Fix a potential heap buffer overread in ALPN extension parsing
+ (server-side). Could result in application crash, but only if an ALPN
+ name larger than 16 bytes had been configured on the server.
Features
* Allow comments in test data files.
diff --git a/library/ssl_srv.c b/library/ssl_srv.c
index de3ea80..85c3c30 100644
--- a/library/ssl_srv.c
+++ b/library/ssl_srv.c
@@ -603,33 +603,41 @@
}
/*
- * Use our order of preference
+ * Validate peer's list (lengths)
*/
start = buf + 2;
end = buf + len;
+ for( theirs = start; theirs != end; theirs += cur_len )
+ {
+ cur_len = *theirs++;
+
+ /* Current identifier must fit in list */
+ if( cur_len > (size_t)( end - theirs ) )
+ {
+ mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
+ MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR );
+ return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
+ }
+
+ /* Empty strings MUST NOT be included */
+ if( cur_len == 0 )
+ {
+ mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
+ MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER );
+ return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
+ }
+ }
+
+ /*
+ * Use our order of preference
+ */
for( ours = ssl->conf->alpn_list; *ours != NULL; ours++ )
{
ours_len = strlen( *ours );
for( theirs = start; theirs != end; theirs += cur_len )
{
- /* If the list is well formed, we should get equality first */
- if( theirs > end )
- {
- mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
- MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER );
- return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
- }
-
cur_len = *theirs++;
- /* Empty strings MUST NOT be included */
- if( cur_len == 0 )
- {
- mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
- MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER );
- return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
- }
-
if( cur_len == ours_len &&
memcmp( theirs, *ours, cur_len ) == 0 )
{
