README

This package offers a module for the SetaPDF-Signer component that allows you to use keys stored on a PKCS11 compatible device (e.g. HSM, USB Token) to digital sign PDF documents in pure PHP.

Requirements

This module requires the PKCS11 PHP extension to be installed.

You also need to provide the path to the PKCS11 module of your device.

The package is developed and tested on PHP >= 7.4 up to PHP 8.5 (PKCS11 PHP extension compiled from master; 2026-01-27). Requirements of the SetaPDF-Signer component can be found here.

Installation

Add following to your composer.json:

{
    "require": {
        "setasign/setapdf-signer-addon-pkcs11": "^1.1"
    },
    "repositories": [
        {
            "type": "composer",
            "url": "https://www.setasign.com/downloads/"
        }
    ]
}

and execute composer update. You need to define the repository to evaluate the dependency to the SetaPDF-Signer component (see here for more details).

Usage

All classes in this package are located in the namespace setasign\SetaPDF\Signer\Module\Pkcs11.

The Module class

This is the main signature module which can be used with the SetaPDF-Signer component. Internally it holds an own instance of the PAdES signature module and offers all relevant proxy methods.

The only arguments you need to pass to the Module instance is a \Pkcs11\Key instance of the private key and the related X509 certificate.

The default padding schema for signatures using RSA keys is RSASSA-PKCS1-v1_5. To use RSASSA-PSS just call $module->setPssPadding();.

A simple complete signature process would look like this:

<?php

use setasign\SetaPDF\Signer\Module\Pkcs11\Module;
use setasign\SetaPDF2\Core\Document;
use setasign\SetaPDF2\Core\Writer\HttpWriter;
use setasign\SetaPDF2\Signer\Digest;
use setasign\SetaPDF2\Signer\Signer;

$pin = '123456';

$modulePath = '/usr/lib/softhsm/libsofthsm2.so';
$pkcs11 = new Pkcs11\Module($modulePath);

$slotList = $pkcs11->getSlotList();
$slotId = $slotList[0];

$session = $pkcs11->openSession($slotId, Pkcs11\CKF_RW_SESSION);
$session->login(Pkcs11\CKU_USER, $pin);

$skey = $session->findObjects([
    Pkcs11\CKA_PRIVATE => true,
    Pkcs11\CKA_LABEL => "SetaPDF-Demo"
])[0];

$module = new setasign\SetaPDF\Signer\Module\Pkcs11\Module($skey);
$module->setCertificate('path/to/setapdf.pem');
$module->setPssPadding();
$module->setDigest(SetaPDF_Signer_Digest::SHA_512);

$fileToSign = 'path/to/Laboratory-Report.pdf';

// create a writer instance
$writer = new HttpWriter('signed.pdf');
// create the document instance
$document = Document::loadByFilename($fileToSign, $writer);

// create the signer instance
$signer = new Signer($document);
$signer->sign($module);

$session->logout();

Testing

For testing purpose we used SoftHSM2 and imported existing test certificates and keys into it using following command:

softhsm2-util --import <PATH-TO-CERTIFICATE> --token "<THE-TOKEN-NAME>" --label "<THE-LABEL>" --id <UNIQUE-ID-IN-HEX-NOTATION>

CSR generation and key attestation is not part of this add-on.