Add a test for the TLSv1.3 downgrade mechanism

Reviewed-by: NRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3022)

test/recipes/70-test_sslextension.t

@@ -43,6 +43,15 @@ sub extension_filter
 {
     my $proxy = shift;
 
+    if ($proxy->flight == 1) {
+        # Change the ServerRandom so that the downgrade sentinel doesn't cause
+        # the connection to fail
+        my $message = ${$proxy->message_list}[1];
+        $message->random("\0"x32);
+        $message->repack();
+        return;
+    }
+
     # We're only interested in the initial ClientHello
     if ($proxy->flight != 0) {
         return;

test/recipes/70-test_sslversions.t

@@ -115,6 +115,17 @@ sub modify_supported_versions_filter
 {
     my $proxy = shift;
 
+    if ($proxy->flight == 1) {
+        # Change the ServerRandom so that the downgrade sentinel doesn't cause
+        # the connection to fail
+        my $message = ${$proxy->message_list}[1];
+        return if (!defined $message);
+
+        $message->random("\0"x32);
+        $message->repack();
+        return;
+    }
+
     # We're only interested in the initial ClientHello
     if ($proxy->flight != 0) {
         return;

test/recipes/70-test_tls13downgrade.t

+#! /usr/bin/env perl
+# Copyright 2017 The OpenSSL Project Authors. All Rights Reserved.
+#
+# Licensed under the OpenSSL license (the "License").  You may not use
+# this file except in compliance with the License.  You can obtain a copy
+# in the file LICENSE in the source distribution or at
+# https://www.openssl.org/source/license.html
+
+use strict;
+use OpenSSL::Test qw/:DEFAULT cmdstr srctop_file bldtop_dir/;
+use OpenSSL::Test::Utils;
+use TLSProxy::Proxy;
+
+my $test_name = "test_tls13downgrade";
+setup($test_name);
+
+plan skip_all => "TLSProxy isn't usable on $^O"
+    if $^O =~ /^(VMS|MSWin32)$/;
+
+plan skip_all => "$test_name needs the dynamic engine feature enabled"
+    if disabled("engine") || disabled("dynamic-engine");
+
+plan skip_all => "$test_name needs the sock feature enabled"
+    if disabled("sock");
+
+plan skip_all => "$test_name needs TLS1.3 and TLS1.2 enabled"
+    if disabled("tls1_3") || disabled("tls1_2");
+
+# TODO(TLS1.3): Enable this when TLSv1.3 comes out of draft
+plan skip_all => "$test_name not run in pre TLSv1.3 RFC implementation"
+    if disabled("tls13downgrade");
+
+$ENV{OPENSSL_ia32cap} = '~0x200000200000000';
+
+my $proxy = TLSProxy::Proxy->new(
+    undef,
+    cmdstr(app(["openssl"]), display => 1),
+    srctop_file("apps", "server.pem"),
+    (!$ENV{HARNESS_ACTIVE} || $ENV{HARNESS_VERBOSE})
+);
+
+use constant {
+    DOWNGRADE_TO_TLS_1_2 => 0,
+    DOWNGRADE_TO_TLS_1_1 => 1
+};
+
+#Test 1: Downgrade from TLSv1.3 to TLSv1.2
+$proxy->filter(\&downgrade_filter);
+my $testtype = DOWNGRADE_TO_TLS_1_2;
+$proxy->start() or plan skip_all => "Unable to start up Proxy for tests";
+plan tests => 3;
+ok(TLSProxy::Message->fail(), "Downgrade TLSv1.3 to TLSv1.2");
+
+#Test 2: Downgrade from TLSv1.3 to TLSv1.1
+$proxy->clear();
+$testtype = DOWNGRADE_TO_TLS_1_1;
+$proxy->start();
+ok(TLSProxy::Message->fail(), "Downgrade TLSv1.3 to TLSv1.1");
+
+#Test 3: Downgrade from TLSv1.2 to TLSv1.1
+$proxy->clear();
+$proxy->clientflags("-no_tls1_3");
+$proxy->serverflags("-no_tls1_3");
+$proxy->start();
+ok(TLSProxy::Message->fail(), "Downgrade TLSv1.2 to TLSv1.1");
+
+sub downgrade_filter
+{
+    my $proxy = shift;
+
+    # We're only interested in the initial ClientHello
+    if ($proxy->flight != 0) {
+        return;
+    }
+
+    my $message = ${$proxy->message_list}[0];
+
+    my $ext;
+    if ($testtype == DOWNGRADE_TO_TLS_1_2) {
+        $ext = pack "C3",
+            0x02, # Length
+            0x03, 0x03; #TLSv1.2
+    } else {
+        $ext = pack "C3",
+            0x02, # Length
+            0x03, 0x02; #TLSv1.1
+    }
+
+    $message->set_extension(TLSProxy::Message::EXT_SUPPORTED_VERSIONS, $ext);
+
+    $message->repack();
+}
+