From bd8add8e67126e3d5b120b2316d4dfc94eba57d0 Mon Sep 17 00:00:00 2001
From: tb <>
Date: Wed, 22 Jan 2020 10:28:49 +0000
Subject: Avoid modifying alert in the success path.

ok beck jsing
---
 src/lib/libssl/ssl_tlsext.c | 28 +++++++++++++++++-----------
 1 file changed, 17 insertions(+), 11 deletions(-)

(limited to 'src/lib')

diff --git a/src/lib/libssl/ssl_tlsext.c b/src/lib/libssl/ssl_tlsext.c
index fdaf251be4..d45dd50863 100644
--- a/src/lib/libssl/ssl_tlsext.c
+++ b/src/lib/libssl/ssl_tlsext.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssl_tlsext.c,v 1.51 2019/11/16 15:36:53 beck Exp $ */
+/* $OpenBSD: ssl_tlsext.c,v 1.52 2020/01/22 10:28:49 tb Exp $ */
 /*
  * Copyright (c) 2016, 2017, 2019 Joel Sing <jsing@openbsd.org>
  * Copyright (c) 2017 Doug Hogan <doug@openbsd.org>
@@ -1936,6 +1936,7 @@ tlsext_parse(SSL *s, CBS *cbs, int *alert, int is_server, uint16_t msg_type)
 	uint16_t type;
 	size_t idx;
 	uint16_t version;
+	uint8_t alert_desc;
 
 	S3I(s)->hs.extensions_seen = 0;
 
@@ -1948,16 +1949,16 @@ tlsext_parse(SSL *s, CBS *cbs, int *alert, int is_server, uint16_t msg_type)
 	if (CBS_len(cbs) == 0)
 		return 1;
 
-	*alert = SSL_AD_DECODE_ERROR;
+	alert_desc = SSL_AD_DECODE_ERROR;
 
 	if (!CBS_get_u16_length_prefixed(cbs, &extensions))
-		return 0;
+		goto err;
 
 	while (CBS_len(&extensions) > 0) {
 		if (!CBS_get_u16(&extensions, &type))
-			return 0;
+			goto err;
 		if (!CBS_get_u16_length_prefixed(&extensions, &extension_data))
-			return 0;
+			goto err;
 
 		if (s->internal->tlsext_debug_cb != NULL)
 			s->internal->tlsext_debug_cb(s, is_server, type,
@@ -1972,24 +1973,29 @@ tlsext_parse(SSL *s, CBS *cbs, int *alert, int is_server, uint16_t msg_type)
 		/* RFC 8446 Section 4.2 */
 		if (version >= TLS1_3_VERSION &&
 		    !(tlsext->messages & msg_type)) {
-			*alert = SSL_AD_ILLEGAL_PARAMETER;
-			return 0;
+			alert_desc = SSL_AD_ILLEGAL_PARAMETER;
+			goto err;
 		}
 
 		/* Check for duplicate known extensions. */
 		if ((S3I(s)->hs.extensions_seen & (1 << idx)) != 0)
-			return 0;
+			goto err;
 		S3I(s)->hs.extensions_seen |= (1 << idx);
 
 		ext = tlsext_funcs(tlsext, is_server);
-		if (!ext->parse(s, &extension_data, alert))
-			return 0;
+		if (!ext->parse(s, &extension_data, &alert_desc))
+			goto err;
 
 		if (CBS_len(&extension_data) != 0)
-			return 0;
+			goto err;
 	}
 
 	return 1;
+
+ err:
+	*alert = alert_desc;
+
+	return 0;
 }
 
 static void
-- 
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