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#! /usr/bin/env perl
# Copyright 2017-2025 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("tls1_2")
|| (disabled("ec") && disabled("dh"));
$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,
FALLBACK_FROM_TLS_1_3 => 2,
DOWNGRADE_TO_TLS_1_2_WITH_TLS_1_1_SIGNAL => 3,
DOWNGRADE_TO_TLS_1_1_WITH_TLS_1_2_SIGNAL => 4,
};
#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 => 8;
ok(is_illegal_parameter_client_alert(), "Downgrade TLSv1.3 to TLSv1.2");
#Test 2: Downgrade from TLSv1.3 to TLSv1.2 (server sends TLSv1.1 signal)
$proxy->clear();
$testtype = DOWNGRADE_TO_TLS_1_2_WITH_TLS_1_1_SIGNAL;
$proxy->start();
ok(is_illegal_parameter_client_alert(),
"Downgrade from TLSv1.3 to TLSv1.2 (server sends TLSv1.1 signal)");
#Test 3: 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();
ok(is_illegal_parameter_client_alert(), "Fallback from TLSv1.3");
SKIP: {
skip "TLSv1.1 disabled", 5 if disabled("tls1_1");
my $client_flags = "-min_protocol TLSv1.1 -cipher DEFAULT:\@SECLEVEL=0";
my $server_flags = "-min_protocol TLSv1.1";
my $ciphers = "AES128-SHA:\@SECLEVEL=0";
#Test 4: Downgrade from TLSv1.3 to TLSv1.1
$proxy->clear();
$testtype = DOWNGRADE_TO_TLS_1_1;
$proxy->clientflags($client_flags);
$proxy->serverflags($server_flags);
$proxy->ciphers($ciphers);
$proxy->start();
ok(is_illegal_parameter_client_alert(), "Downgrade TLSv1.3 to TLSv1.1");
#Test 5: Downgrade from TLSv1.3 to TLSv1.1 (server sends TLSv1.2 signal)
$proxy->clear();
$testtype = DOWNGRADE_TO_TLS_1_1_WITH_TLS_1_2_SIGNAL;
$proxy->clientflags($client_flags);
$proxy->serverflags($server_flags);
$proxy->ciphers($ciphers);
$proxy->start();
ok(is_illegal_parameter_client_alert(),
"Downgrade TLSv1.3 to TLSv1.1 (server sends TLSv1.2 signal)");
#Test 6: Downgrade from TLSv1.2 to TLSv1.1
$proxy->clear();
$testtype = DOWNGRADE_TO_TLS_1_1;
$proxy->clientflags($client_flags." -max_protocol TLSv1.2");
$proxy->serverflags($server_flags." -max_protocol TLSv1.2");
$proxy->ciphers($ciphers);
$proxy->start();
ok(is_illegal_parameter_client_alert(), "Downgrade TLSv1.2 to TLSv1.1");
#Test 7: A client side protocol "hole" should not be detected as a downgrade
$proxy->clear();
$proxy->filter(undef);
$proxy->clientflags($client_flags." -no_tls1_2");
$proxy->serverflags($server_flags);
$proxy->ciphers($ciphers);
$proxy->start();
ok(TLSProxy::Message->success(), "TLSv1.2 client-side protocol hole");
#Test 8: A server side protocol "hole" should not be detected as a downgrade
$proxy->clear();
$proxy->filter(undef);
$proxy->clientflags($client_flags);
$proxy->serverflags($server_flags." -no_tls1_2");
$proxy->ciphers($ciphers);
$proxy->start();
ok(TLSProxy::Message->success(), "TLSv1.2 server-side protocol hole");
}
# Validate that the exchange fails with an illegal parameter alert from
# the client
sub is_illegal_parameter_client_alert
{
return 0 unless TLSProxy::Message->fail();
my $alert = TLSProxy::Message->alert();
return 1 if !$alert->server()
&& $alert->description()
== TLSProxy::Message::AL_DESC_ILLEGAL_PARAMETER;
return 0;
}
sub downgrade_filter
{
my $proxy = shift;
# We're only interested in the initial ClientHello and ServerHello
if ($proxy->flight > 1) {
return;
}
my $message = ${$proxy->message_list}[$proxy->flight];
# ServerHello
if ($proxy->flight == 1 && defined($message)) {
# Update the last byte of the downgrade signal
if ($testtype == DOWNGRADE_TO_TLS_1_2_WITH_TLS_1_1_SIGNAL) {
$message->random(substr($message->random, 0, 31) . "\0");
$message->repack();
} elsif ($testtype == DOWNGRADE_TO_TLS_1_1_WITH_TLS_1_2_SIGNAL) {
$message->random(substr($message->random, 0, 31) . "\1");
$message->repack();
}
return;
}
# ClientHello
if ($proxy->flight == 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
|| $testtype == DOWNGRADE_TO_TLS_1_2_WITH_TLS_1_1_SIGNAL) {
$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();
}
}
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