Verify SSL Certificates using Openssl in PHP - php

Question

I am working on below things:
Generate CSR(Certificate Signing Request)
Upload SSL Certificates
To generate SSL certificate I am using something like:
$privkey = openssl_pkey_new();
$csr = openssl_csr_new($dn, $privkey);
$sscert = openssl_csr_sign($csr, null, $privkey, $days);
openssl_csr_export($csr, $csrout);
openssl_pkey_export($privkey, $pkeyout, $_POST['password']);
openssl_pkey_export_to_file($privkey, "<path/to/store/server.key>");
openssl_csr_export_to_file($csr, "/tmp/".<domain-name>.".csr");
Now using that CSR request, I am able to generate(domain-name.cer),(DigitalCert.cer).
Now once I upload this(.cer) certificates, I need to verify those certificates.
Reason: Someone generated these certificates on say "a.com" and tries to upload on "b.com". this should not happen, so I want to validate the uploaded SSL certificates.
In PHP, we have
$ok = openssl_verify($data, $signature, $pubkeyid);
but i am not able to get what things would be treated as $data, $signature and $pubkeyid based on the above certificate generation process.

Answer 1

Check this out:
Verify SMTP in PHP
<?php
$server = "smtp.gmail.com"; // Who I connect to
$myself = "my_server.example.com"; // Who I am
$cabundle = '/etc/ssl/cacert.pem'; // Where my root certificates are
// Verify server. There's not much we can do, if we suppose that an attacker
// has taken control of the DNS. The most we can hope for is that there will
// be discrepancies between the expected responses to the following code and
// the answers from the subverted DNS server.
// To detect these discrepancies though, implies we knew the proper response
// and saved it in the code. At that point we might as well save the IP, and
// decouple from the DNS altogether.
$match1 = false;
$addrs = gethostbynamel($server);
foreach($addrs as $addr)
{
$name = gethostbyaddr($addr);
if ($name == $server)
{
$match1 = true;
break;
}
}
// Here we must decide what to do if $match1 is false.
// Which may happen often and for legitimate reasons.
print "Test 1: " . ($match1 ? "PASSED" : "FAILED") . "\n";
$match2 = false;
$domain = explode('.', $server);
array_shift($domain);
$domain = implode('.', $domain);
getmxrr($domain, $mxhosts);
foreach($mxhosts as $mxhost)
{
$tests = gethostbynamel($mxhost);
if (0 != count(array_intersect($addrs, $tests)))
{
// One of the instances of $server is a MX for its domain
$match2 = true;
break;
}
}
// Again here we must decide what to do if $match2 is false.
// Most small ISP pass test 2; very large ISPs and Google fail.
print "Test 2: " . ($match2 ? "PASSED" : "FAILED") . "\n";
// On the other hand, if you have a PASS on a server you use,
// it's unlikely to become a FAIL anytime soon.
// End of maybe-they-help-maybe-they-don't checks.
// Establish the connection
$smtp = fsockopen( "tcp://$server", 25, $errno, $errstr );
fread( $smtp, 512 );
// Here you can check the usual banner from $server (or in general,
// check whether it contains $server's domain name, or whether the
// domain it advertises has $server among its MX's.
// But yet again, Google fails both these tests.
fwrite($smtp,"HELO $myself\r\n");
fread($smtp, 512);
// Switch to TLS
fwrite($smtp,"STARTTLS\r\n");
fread($smtp, 512);
stream_set_blocking($smtp, true);
stream_context_set_option($smtp, 'ssl', 'verify_peer', true);
stream_context_set_option($smtp, 'ssl', 'allow_self_signed', false);
stream_context_set_option($smtp, 'ssl', 'capture_peer_cert', true);
stream_context_set_option($smtp, 'ssl', 'cafile', $cabundle);
$secure = stream_socket_enable_crypto($smtp, true, STREAM_CRYPTO_METHOD_TLS_CLIENT);
stream_set_blocking($smtp, false);
$opts = stream_context_get_options($smtp);
if (!isset($opts["ssl"]["peer_certificate"]))
$secure = false;
else
{
$cert = openssl_x509_parse($opts["ssl"]["peer_certificate"]);
$names = '';
if ('' != $cert)
{
if (isset($cert['extensions']))
$names = $cert['extensions']['subjectAltName'];
elseif (isset($cert['subject']))
{
if (isset($cert['subject']['CN']))
$names = 'DNS:' . $cert['subject']['CN'];
else
$secure = false; // No exts, subject without CN
}
else
$secure = false; // No exts, no subject
}
$checks = explode(',', $names);
// At least one $check must match $server
$tmp = explode('.', $server);
$fles = array_reverse($tmp);
$okay = false;
foreach($checks as $check)
{
$tmp = explode(':', $check);
if ('DNS' != $tmp[0]) continue; // candidates must start with DNS:
if (!isset($tmp[1])) continue; // and have something afterwards
$tmp = explode('.', $tmp[1]);
if (count($tmp) < 3) continue; // "*.com" is not a valid match
$cand = array_reverse($tmp);
$okay = true;
foreach($cand as $i => $item)
{
if (!isset($fles[$i]))
{
// We connected to www.example.com and certificate is for *.www.example.com -- bad.
$okay = false;
break;
}
if ($fles[$i] == $item)
continue;
if ($item == '*')
break;
}
if ($okay)
break;
}
if (!$okay)
$secure = false; // No hosts matched our server.
}
if (!$secure)
die("failed to connect securely\n");
print "Success!\n";
// Continue with connection...
?>

Answer 2

This works for me
$crt_md5=exec('openssl x509 -noout -modulus -in /path/to/domain.crt/ | openssl md5 | sed "s/^.* //"');
$key_md5=exec('openssl rsa -noout -modulus -in /path/to/server.key | openssl md5 | sed "s/^.* //"');
if($crt_md5 != $key_md5){
echo 'BAD';
}
else{
echo "GOOD";
}
sed "s/^.* //" - will remove (stdin)= thing from the output, so that
you get exact md5 string

Answer 3

this is how i do it...
system('openssl x509 -noout -modulus -in '.$crt.' | openssl md5', $crt_md5);
system('openssl rsa -noout -modulus -in '.$key.' | openssl md5', $key_md5);
if($crt_md5 != $key_md5){
echo 'BAD';
}

Answer 4

Try openssl_x509_check_private_key( $crt, $key ) it returns boolean
ref http://php.net/manual/en/function.openssl-x509-check-private-key.php

Answer 5

WARNING: openssl_x509_check_private_key will not work for some case.
Example:
SSL certificate like this:
-----BEGIN CERTIFICATE-----
xxxx
-----END CERTIFICATE-----
-----BEGIN CERTIFICATE-----
xxxx
xxxx
This certificate does not end with -----END CERTIFICATE----- , but it can still pass the check of this function. It will return true to tell you that it is correct, but it is not actually. If you upload this certificate to your application, such as Nginx , Nginx will tell you an error.
This doesn't seem to be an error that only appears in PHP. If you check with the openssl function on the command line, it will tell you the same result.
So I think the best way is that you need to check whether the paragraphs of the certificate are complete.
After confirming that the format is correct, use this function to verify the certificate and private key.