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Don't detect a downgrade where the server has a protocol version hole

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Reviewed-by: Viktor Dukhovni <viktor@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/7013)
This commit is contained in:
Matt Caswell 2018-08-20 18:05:28 +01:00
parent 3e7cb13dff
commit 5627f9f217
2 changed files with 21 additions and 7 deletions
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13
ssl/statem/statem_lib.c
View File

@ -1665,9 +1665,16 @@ static void check_for_downgrade(SSL *s, int vers, DOWNGRADE *dgrd)
if (vers == TLS1_2_VERSION
&& ssl_version_supported(s, TLS1_3_VERSION, NULL)) {
*dgrd = DOWNGRADE_TO_1_2;
} else if (!SSL_IS_DTLS(s) && vers < TLS1_2_VERSION
&& (ssl_version_supported(s, TLS1_2_VERSION, NULL)
|| ssl_version_supported(s, TLS1_3_VERSION, NULL))) {
} else if (!SSL_IS_DTLS(s)
&& vers < TLS1_2_VERSION
/*
* We need to ensure that a server that disables TLSv1.2
* (creating a hole between TLSv1.3 and TLSv1.1) can still
* complete handshakes with clients that support TLSv1.2 and
* below. Therefore we do not enable the sentinel if TLSv1.3 is
* enabled and TLSv1.2 is not.
*/
&& ssl_version_supported(s, TLS1_2_VERSION, NULL)) {
*dgrd = DOWNGRADE_TO_1_1;
} else {
*dgrd = DOWNGRADE_NONE;

15
test/recipes/70-test_tls13downgrade.t
View File

@ -45,7 +45,7 @@ use constant {
$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 => 5;
plan tests => 6;
ok(TLSProxy::Message->fail(), "Downgrade TLSv1.3 to TLSv1.2");
#Test 2: Downgrade from TLSv1.3 to TLSv1.1
@ -74,13 +74,20 @@ ok(TLSProxy::Message->fail()
"Fallback from TLSv1.3");
SKIP: {
skip "TLSv1.1 disabled", 1 if disabled("tls1_1");
#Test 5: A protocol "hole" should not be detected as a downgrade
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->start();
ok(TLSProxy::Message->success(), "TLSv1.2 protocol hole");
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