SSL context option 'CN_match' useless without 'verify

SSL context option 'CN_match' useless without 'verify_peer'

Bug #47030

SSL context option 'CN_match' useless without 'verify_peer'

Submitted:

2009-01-07 17:33 UTC

Modified:

2014-02-16 17:18 UTC

Votes:	6
Avg. Score:	4.8 ± 0.4
Reproduced:	6 of 6 (100.0%)
Same Version:	0 (0.0%)
Same OS:	0 (0.0%)

From:

avb@php.net

Assigned:

rdlowrey (profile)

Status:

Closed

Package:

OpenSSL related

PHP Version:

5.2.8

OS:

Windows Vista

Private report:

CVE-ID:

None

[2009-01-07 17:33 UTC] avb@php.net

Description:
------------
It is currently impossible to only perform a check that the host name matches Common Name in SSL certificate. If 'verify_peer' is off, then the check is not performed, while documentation does not mention that these context options are dependent.

Note that cURL extension behaves as expected, the script
<?php
$ch = curl_init();
curl_setopt($ch, CURLOPT_HTTPGET, true);
curl_setopt($ch, CURLOPT_URL, 'https://sf.net/');
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 2);
if (!curl_exec($ch)) {
    echo "Error #" . curl_errno($ch) . ": " . curl_error($ch);
}
?>
outputs the following:
Error #51: SSL: certificate subject name 'sourceforge.net' does not match target host name 'sf.net'

Reproduce code:
---------------
$context = stream_context_create(array(
    'ssl' => array(
        'verify_peer' => false,
        'CN_match'    => 'sf.net'
    )
));
$stream = stream_socket_client('ssl://sf.net:443', $errno, $errstr, 10, STREAM_CLIENT_CONNECT, $context);
if ($stream) {
    echo "Stream connected OK\r\n";
}


Expected result:
----------------
Some error message that certificate name 'sourceforge.net' does not match expected 'sf.net'

Actual result:
--------------
Stream connected OK

Patches

Pull Requests

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[2009-09-20 09:14 UTC] avb@php.net

It may also be a good idea to use name explicitly given in CN_match for peer verification instead of host name stream_socket_client() was called upon. Consider a proxy scenario:
<php
$context = stream_context_create(array(
    'ssl' => array(
        'verify_peer' => true,
        'CN_match'    => 'sourceforge.net'
    )
));
// connecting to proxy
$stream = stream_socket_client(
    'tcp://proxy.example.com:3128', $errno, $errstr, 10,
    STREAM_CLIENT_CONNECT, $context
);
// establishing the tunnel
fwrite($stream, 'CONNECT sourceforge.net ...');

// ... read proxy response

// establish crypto
stream_socket_enable_crypto(
    $stream, true, STREAM_CRYPTO_METHOD_TLS_CLIENT
);
?>

This script will fail now since proxy.example.com obviously doesn't match the certificate for sourceforge.net

[2014-02-15 00:02 UTC] rdlowrey@php.net

This has been addressed in the 5.6 development branch and master via the linked pull request.

As of 5.6 all client streams verify peers and host names by default. Peer certificate verification (via CAs) and host name verification (via CN and SAN) are now independent of one another. As these changes rely heavily on other features introduced in 5.6 you probably shouldn't hold your breath waiting for them to be back-ported to older versions.

<?php
$uri = '';
$flags = STREAM_CLIENT_CONNECT;
$ctx = stream_context_create(['ssl' => [
    'verify_peer' => false, // defaults to true for clients (as of 5.6)
    'verify_host' => true, // defaults to true for clients (new in 5.6)
    'CN_match' => 'somename.com' // <-- override the URI host name
]]);

$client = stream_socket_client($uri, $errno, $errstr, $timeout, $flags, $ctx);

[2014-02-16 17:18 UTC] rdlowrey@php.net

-Assigned To: pajoye +Assigned To: rdlowrey

[2015-08-10 07:51 UTC] arekm at maven dot pl

Related To: Bug #68344