tlsext: check we reject unadvertised selected protocol

This test currently fails and will be fixed in ssl_tlsect.c r1.168

1 files changed, 24 insertions, 1 deletions

diff --git a/src/regress/lib/libssl/tlsext/tlsexttest.c b/src/regress/lib/libssl/tlsext/tlsexttest.c
index 9c4c0f55a1..29b348154f 100644
--- a/src/regress/lib/libssl/tlsext/tlsexttest.c
+++ b/src/regress/lib/libssl/tlsext/tlsexttest.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: tlsexttest.c,v 1.97 2026/04/03 07:37:52 jsing Exp $ */
+/* $OpenBSD: tlsexttest.c,v 1.98 2026/08/29 05:12:47 tb Exp $ */
 /*
  * Copyright (c) 2017 Joel Sing <jsing@openbsd.org>
  * Copyright (c) 2017 Doug Hogan <doug@openbsd.org>
@@ -153,6 +153,14 @@ const uint8_t tlsext_alpn_single_proto[] = {
         0x68, 0x74, 0x74, 0x70, 0x2f, 0x31, 0x2e, 0x31
 };
 
+const uint8_t tlsext_alpn_single_proto_unadvertised[] = {
+        /* ProtocolName protocol_name_list<2..2^16-1> -- ALPN names */
+        0x00, 0x09, /* len of all names */
+        /* opaque ProtocolName<1..2^8-1> -- 'http/1.2' */
+        0x08, /* len */
+        0x68, 0x74, 0x74, 0x70, 0x2f, 0x31, 0x2e, 0x32
+};
+
 #define TLSEXT_TYPE_alpn TLSEXT_TYPE_application_layer_protocol_negotiation
 
 static int
@@ -334,6 +342,21 @@ test_tlsext_alpn_client(void)
                 goto err;
         }
 
+        /* Make sure we don't accept a protocol we did not advertise. */
+
+        CBS_init(&cbs, tlsext_alpn_single_proto_unadvertised,
+            sizeof(tlsext_alpn_single_proto_unadvertised));
+
+        if (client_funcs->process(ssl, SSL_TLSEXT_MSG_SH, &cbs, &alert)) {
+                FAIL("failed to reject unadvertised ALPN protocol\n");
+                goto err;
+        }
+        if (alert != SSL_AD_ILLEGAL_PARAMETER) {
+                FAIL("unadvertised ALPN: want illegal_parameter, got %s\n",
+                    SSL_alert_desc_string_long(alert));
+                goto err;
+        }
+
         /* Make sure we can remove the list and avoid ALPN */
 
         free(ssl->alpn_client_proto_list);