test/recipes/70-test_tls13downgrade.t

#! /usr/bin/env perl
# Copyright 2017-2021 The OpenSSL Project Authors. All Rights Reserved.
#
# Licensed under the Apache License 2.0 (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 $^O =~ /^(VMS)$/;

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("ec") && disabled("dh"))
       || disabled("tls1_2");

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,
    FALLBACK_FROM_TLS_1_3 => 2,
};

#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 => 6;
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");

#Test 4: Client falls back from TLSv1.3 (server does not support the fallback
#        SCSV)
$proxy->clear();
$testtype = FALLBACK_FROM_TLS_1_3;
$proxy->clientflags("-fallback_scsv -no_tls1_3");
$proxy->start();
my $alert = TLSProxy::Message->alert();
ok(TLSProxy::Message->fail()
   && !$alert->server()
   && $alert->description() == TLSProxy::Message::AL_DESC_ILLEGAL_PARAMETER,
   "Fallback from TLSv1.3");

SKIP: {
    skip "TLSv1.1 disabled", 2 if disabled("tls1_1");
    #Test 5: A client side protocol "hole" should not be detected as a downgrade
    $proxy->clear();
    $proxy->filter(undef);
    $proxy->clientflags("-no_tls1_2");
    $proxy->ciphers("AES128-SHA:\@SECLEVEL=0");
    $proxy->start();
    ok(TLSProxy::Message->success(), "TLSv1.2 client-side protocol hole");

    #Test 6: A server side protocol "hole" should not be detected as a downgrade
    $proxy->clear();
    $proxy->filter(undef);
    $proxy->serverflags("-no_tls1_2");
    $proxy->start();
    ok(TLSProxy::Message->success(), "TLSv1.2 server-side protocol hole");
}

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 == FALLBACK_FROM_TLS_1_3) {
        #The default ciphersuite we use for TLSv1.2 without any SCSV
        my @ciphersuites = (TLSProxy::Message::CIPHER_RSA_WITH_AES_128_CBC_SHA);
        $message->ciphersuite_len(2 * scalar @ciphersuites);
        $message->ciphersuites(\@ciphersuites);
    } else {
        if ($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();
}