PHP Extension

SSH HSM Public Key Authentication

Demonstrates SSH public-key authentication using a private key stored on an HSM — a USB token or smart card — accessed through PKCS#11. A session is opened with the vendor's driver, the key handles are located, and an SshKey object is bound to them with UsePkcs11.

Background: The point of an HSM is that the private key is generated on the device and cannot be exported: the signing operation happens on the hardware, so the key material never reaches your application's memory or disk. Even a fully compromised host cannot yield a copy of the key. PKCS#11 is the vendor-neutral interface to such devices, which is why the driver path and the object-finding template are the only vendor-specific parts of this example.

Chilkat PHP Extension Downloads

Download Chilkat for PHP Extension

PHP Extension

<?php

include("chilkat.php");

$success = false;

//  This example requires the Chilkat API to have been previously unlocked.
//  See Global Unlock Sample for sample code.

//  Demonstrates SSH public-key authentication using a private key stored on an HSM (a USB token
//  or smart card) accessed through PKCS#11.
//  
//  Note: Chilkat's PKCS#11 implementation runs on Windows, Linux, macOS, and other supported
//  operating systems.

$pkcs11 = new CkPkcs11();

//  The PKCS#11 driver supplied by your HSM vendor: a .dll on Windows, a .so on Linux, or a
//  .dylib on macOS.
$pkcs11->put_SharedLibPath('C:/Program Files (x86)/Gemalto/IDGo 800 PKCS#11/IDPrimePKCS1164.dll');

//  The PIN should come from a secure source rather than being hard-coded.
$pin = '0000';

//  Normal user = 1
$userType = 1;

$success = $pkcs11->QuickSession($userType,$pin);
if ($success == false) {
    print $pkcs11->lastErrorText() . "\n";
    exit;
}

//  Describe the private key object to be located on the HSM.
$json = new CkJsonObject();
$json->UpdateString('class','private_key');
$json->UpdateString('label','MySshKey');

$priv_handle = $pkcs11->FindObject($json);
if ($priv_handle == 0) {
    print $pkcs11->lastErrorText() . "\n";
    exit;
}

//  Find the corresponding public key by changing the class in the same template.
$json->UpdateString('class','public_key');

$pub_handle = $pkcs11->FindObject($json);
if ($pub_handle == 0) {
    print $pkcs11->lastErrorText() . "\n";
    exit;
}

//  Create an SSH key object that uses the HSM handles.  The key type may be "rsa" or "ec".
$key = new CkSshKey();
$keyType = 'rsa';
$success = $key->UsePkcs11($pkcs11,$priv_handle,$pub_handle,$keyType);
if ($success == false) {
    print $key->lastErrorText() . "\n";
    exit;
}

$ssh = new CkSsh();

$port = 22;
$success = $ssh->Connect('ssh.example.com',$port);
if ($success == false) {
    print $ssh->lastErrorText() . "\n";
    exit;
}

//  The corresponding public key must already be installed on the SSH server for the account.
//  The signing operation happens on the HSM -- the private key never leaves the device.
$success = $ssh->AuthenticatePk('mySshLogin',$key);
if ($success == false) {
    print $ssh->lastErrorText() . "\n";
    exit;
}

print 'Public-key authentication successful.' . "\n";

$ssh->Disconnect();

$pkcs11->Logout();
$pkcs11->CloseSession();

?>