PHP SSL Certificate Calculate Fingerprint


When you view certificate details in a browser, it shows the certificate fingerprint. At the time of this writing, Firefox shows the md5 and sha1 fingerprints, Chrome shows sha1 and sha256 fingerprints. It leads one to wonder how to calculate the fingerprint of certificate.

In command line openssl:
openssl x509 -in github.com -noout -fingerprint -md5
openssl x509 -in github.com -noout -fingerprint -sha1
openssl x509 -in github.com -noout -fingerprint -sha256

output:
MD5 Fingerprint=DF:EF:60:0C:26:E8:CF:C7:00:3A:F4:B7:30:58:0D:07
SHA1 Fingerprint=CE:67:99:25:2C:AC:78:12:7D:94:B5:62:2C:31:C5:16:A6:34:73:53
SHA256 Fingerprint=7C:FB:00:BA:0B:97:69:F1:36:FC:4F:D4:F3:96:19:89:8B:D1:D9:DD:85:A5:7F:3C:0A:D1:9B:8A:BF:97:76:5B

in PHP:
<?php
function x509_fingerprint($pem,$hash='sha1')
{
    $hash = in_array($hash,array('sha1','md5','sha256')) ? $hash: 'sha1';
    $pem = preg_replace('/\-+BEGIN CERTIFICATE\-+/','',$pem);
    $pem = preg_replace('/\-+END CERTIFICATE\-+/','',$pem);
    $pem = str_replace( array("\n","\r"), '', trim($pem));
    return strtoupper(hash($hash,base64_decode($pem)));
}
 
$x509_cert_pem='-----BEGIN CERTIFICATE-----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AVYeggFSAEEAbgB5ACAAdQBzAGUAIABvAGYAIAB0AGgAaQBzACAAQwBlAHIAdABp
AGYAaQBjAGEAdABlACAAYwBvAG4AcwB0AGkAdAB1AHQAZQBzACAAYQBjAGMAZQBw
AHQAYQBuAGMAZQAgAG8AZgAgAHQAaABlACAARABpAGcAaQBDAGUAcgB0ACAAQwBQ
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AHQAeQAgAEEAZwByAGUAZQBtAGUAbgB0ACAAdwBoAGkAYwBoACAAbABpAG0AaQB0
ACAAbABpAGEAYgBpAGwAaQB0AHkAIABhAG4AZAAgAGEAcgBlACAAaQBuAGMAbwBy
AHAAbwByAGEAdABlAGQAIABoAGUAcgBlAGkAbgAgAGIAeQAgAHIAZQBmAGUAcgBl
AG4AYwBlAC4wHQYDVR0lBBYwFAYIKwYBBQUHAwEGCCsGAQUFBwMCMBEGCWCGSAGG
+EIBAQQEAwIGwDAOBgNVHQ8BAf8EBAMCBaAwDQYJKoZIhvcNAQEFBQADggEBABRS
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n2Xkw9dJh1tybLEvrG8=
-----END CERTIFICATE-----';
$pem = $x509_cert_pem;
echo 'MD5 Fingerprint='.implode(":", str_split( x509_fingerprint($pem,$hash='md5'), 2))."\n";
echo 'SHA1 Fingerprint='.implode(":", str_split( x509_fingerprint($pem,$hash='sha1'), 2))."\n";
echo 'SHA256 Fingerprint='.implode(":", str_split( x509_fingerprint($pem,$hash='sha256'), 2))."\n";

code snippets are licensed under Creative Commons CC-By-SA 3.0 (unless otherwise specified)

Eric on 2014-08-14 05:57:14
Combine this with:

$g = stream_context_create (array("ssl" =&gt; array("capture_peer_cert" =&gt; true)));
$r = stream_socket_client("ssl://domain:443", $errno, $errstr, 30, STREAM_CLIENT_CONNECT, $g);
$cont = stream_context_get_params($r);
// Store remote certificate as a string
openssl_x509_export($cont['options']['ssl']['peer_certificate'], $x509_cert);

And you've got yourself a powerful thumbprint scanner capable of verifying remote hosts. Way better than the curl implementation.

Pepe on 2015-05-26 10:27:09
Thanks!!
It helped me a lot!

Charly on 2016-11-04 14:30:47
Thank you for this code. So simple !