ACMECert

PHP client library for Let's Encrypt (ACME v2 - RFC 8555)
Version: 2.8

Description

ACMECert is designed to help you to setup an automated SSL/TLS-certificate/renewal process with a few lines of PHP.

It is self contained and contains a set of functions allowing you to:

• generate RSA / EC (Elliptic Curve) keys
• manage account: register/update/deactivate and account key roll-over
• get/revoke certificates (to renew a certificate just get a new one)
• parse certificates / get the remaining days a certificate is still valid

see Function Reference for a full list

It abstacts away the complexity of the ACME protocol to get a certificate (create order, fetch authorizations, compute challenge tokens, polling for status, generate CSR, finalize order, request certificate) into a single function getCertificateChain, where you specify a set of domains you want to get a certificate for and which challenge type to use (all challenge types are supported). This function takes as third argument a user-defined callback function which gets invoked every time a challenge needs to be fulfilled. It is up to you to set/remove the challenge tokens:

$handler=function($opts){
  // Write code to setup the challenge token here.

  // Return a function that gets called when the challenge token should be removed again:
  return function($opts){
    // Write code to remove previously setup challenge token.
  };
};

$ac->getCertificateChain(..., ..., $handler);

see description of getCertificateChain for details about the callback function.

also see the Get Certificate examples below.

Instead of returning FALSE on error, every function in ACMECert throws an Exception if it fails or an ACME_Exception if the ACME-Server reponded with an error message.

Requirements

• PHP 5.3 or higher (for EC keys PHP 7.1 or higher is required)
• OpenSSL extension
• enabled fopen wrappers (allow_url_fopen=1) or cURL extension

Usage Examples

Require ACMECert

require 'ACMECert.php';

Choose Live or Staging Environment

Live

$ac=new ACMECert();

Staging

$ac=new ACMECert(false);

Generate RSA Private Key

$key=$ac->generateRSAKey(2048);
file_put_contents('account_key.pem',$key);

Equivalent to: openssl genrsa -out account_key.pem 2048

Generate EC Private Key

$key=$ac->generateECKey('P-384');
file_put_contents('account_key.pem',$key);

Equivalent to: openssl ecparam -name secp384r1 -genkey -noout -out account_key.pem

Register Account Key with Let's Encrypt

$ac->loadAccountKey('file://'.'account_key.pem');
$ret=$ac->register(true,'[email protected]');
print_r($ret);

WARNING: By passing TRUE as first parameter of the register function you agree to the terms of service of Let's Encrypt. See Let’s Encrypt Subscriber Agreement for more information.

Get Account Information

$ac->loadAccountKey('file://'.'account_key.pem');
$ret=$ac->getAccount();
print_r($ret);

Account Key Roll-over

$ac->loadAccountKey('file://'.'account_key.pem');
$ret=$ac->keyChange('file://'.'new_account_key.pem');
print_r($ret);

Deactivate Account

$ac->loadAccountKey('file://'.'account_key.pem');
$ret=$ac->deactivateAccount();
print_r($ret);

Revoke Certificate

$ac->loadAccountKey('file://'.'account_key.pem');
$ac->revoke('file://'.'fullchain.pem');

Get Remaining Days

$days=$ac->getRemainingDays('file://'.'fullchain.pem'); // certificate or certificate-chain
if ($days>30) { // renew 30 days before expiry
  die('Certificate still good, exiting..');
}
// get new certificate here..

This allows you to run your renewal script without the need to time it exactly, just run it often enough. (cronjob)

Get Certificate using http-01 challenge

$ac->loadAccountKey('file://'.'account_key.pem');

$domain_config=array(
  'test1.example.com'=>array('challenge'=>'http-01','docroot'=>'/var/www/vhosts/test1.example.com'),
  'test2.example.com'=>array('challenge'=>'http-01','docroot'=>'/var/www/vhosts/test2.example.com')
);

$handler=function($opts){
  $fn=$opts['config']['docroot'].$opts['key'];
  @mkdir(dirname($fn),0777,true);
  file_put_contents($fn,$opts['value']);
  return function($opts){
    unlink($opts['config']['docroot'].$opts['key']);
  };
};

$fullchain=$ac->getCertificateChain('file://'.'cert_private_key.pem',$domain_config,$handler);
file_put_contents('fullchain.pem',$fullchain);

Get Certificate using all (http-01,dns-01 and tls-alpn-01) challenge types together

$ac->loadAccountKey('file://'.'account_key.pem');

$domain_config=array(
  'example.com'=>array('challenge'=>'http-01','docroot'=>'/var/www/vhosts/example.com'),
  '*.example.com'=>array('challenge'=>'dns-01'),
  'test.example.org'=>array('challenge'=>'tls-alpn-01')
);

$handler=function($opts) use ($ac){
  switch($opts['config']['challenge']){
    case 'http-01': // automatic example: challenge directory/file is created..
      $fn=$opts['config']['docroot'].$opts['key'];
      @mkdir(dirname($fn),0777,true);
      file_put_contents($fn,$opts['value']);
      return function($opts) use ($fn){ // ..and removed after validation completed
        unlink($fn);
      };
    break;
    case 'dns-01': // manual example:
      echo 'Create DNS-TXT-Record '.$opts['key'].' with value '.$opts['value']."\n";
      readline('Ready?');
      return function($opts){
        echo 'Remove DNS-TXT-Record '.$opts['key'].' with value '.$opts['value']."\n";
      };
    break;
    case 'tls-alpn-01':
      $cert=$ac->generateALPNCertificate('file://'.'some_private_key.pem',$opts['domain'],$opts['value']);
      // Use $cert and some_private_key.pem(<- does not have to be a specific key,
      // just make sure you generated one) to serve the certificate for $opts['domain']


      // This example uses an included ALPN Responder - a standalone https-server
      // written in a few lines of node.js - which is able to complete this challenge.

      // store the generated verification certificate to be used by the ALPN Responder.
      file_put_contents('alpn_cert.pem',$cert);

      // To keep this example simple, the included Example ALPN Responder listens on port 443,
      // so - for the sake of this example - you have to stop the webserver here, like:
      shell_exec('/etc/init.d/apache2 stop');

      // Start ALPN Responder (requires node.js)
      $resource=proc_open(
        'node alpn_responder.js some_private_key.pem alpn_cert.pem',
        array(
          0=>array('pipe','r'),
          1=>array('pipe','w')
        ),
        $pipes
      );

      // wait until alpn responder is listening
      fgets($pipes[1]);

      return function($opts) use ($resource,$pipes){
        // Stop ALPN Responder
        fclose($pipes[0]);
        fclose($pipes[1]);
        proc_close($resource);
        shell_exec('/etc/init.d/apache2 start');
      };
    break;
  }
};

// Example for using a pre-generated CSR as input to getCertificateChain instead of a private key:
// $csr=$ac->generateCSR('file://'.'cert_private_key.pem',array_keys($domain_config));
// $fullchain=$ac->getCertificateChain($csr,$domain_config,$handler);

$fullchain=$ac->getCertificateChain('file://'.'cert_private_key.pem',$domain_config,$handler);
file_put_contents('fullchain.pem',$fullchain);

Logging

ACMECert logs its actions using error_log, which logs messages to stderr per default in PHP CLI so it is easy to log to a file instead:

error_reporting(E_ALL);
ini_set('log_errors',1);
ini_set('error_log',dirname(__FILE__).'/ACMECert.log');

ACME_Exception

If the ACME-Server responded with an error message an ACME_Exception is thrown. (ACME_Exception extends Exception)

ACME_Exception has two additional functions:

• getType() to get the ACME error code:

require 'ACMECert.php';
$ac=new ACMECert();
$ac->loadAccountKey('file://'.'account_key.pem');
try {
  echo $ac->getAccountID().PHP_EOL;
}catch(ACME_Exception $e){
  if ($e->getType()=='urn:ietf:params:acme:error:accountDoesNotExist'){
    echo 'Account does not exist'.PHP_EOL;
  }else{
    throw $e; // another error occured
  }
}

• getSubproblems() to get an array of ACME_Exceptions if there is more than one error returned from the ACME-Server:

try {
	$cert=$ac->getCertificateChain('file://'.'cert_private_key.pem',$domain_config,$handler);
} catch (ACME_Exception $e){
	$ac->log($e->getMessage()); // log original error
	foreach($e->getSubproblems() as $subproblem){
		$ac->log($subproblem->getMessage()); // log sub errors
	}
}

Function Reference

ACMECert::__construct

Creates a new ACMECert instance.

public ACMECert::__construct ( bool $live = TRUE )

Parameters

live

When FALSE, the ACME v2 staging environment is used otherwise the live environment.

Return Values

Returns a new ACMECert instance.

---

ACMECert::generateRSAKey

Generate RSA private key (used as account key or private key for a certificate).

public string ACMECert::generateRSAKey ( int $bits = 2048 )

Parameters

bits

RSA key size in bits.

Return Values

Returns the generated RSA private key as PEM encoded string.

Errors/Exceptions

Throws an Exception if the RSA key could not be generated.

---

ACMECert::generateECKey

Generate Elliptic Curve (EC) private key (used as account key or private key for a certificate).

public string ACMECert::generateECKey ( string $curve_name = 'P-384' )

Parameters

curve_name

Supported Curves by Let’s Encrypt:

• P-256 (prime256v1)
• P-384 (secp384r1)
• P-521 (secp521r1)

Return Values

Returns the generated EC private key as PEM encoded string.

Errors/Exceptions

Throws an Exception if the EC key could not be generated.

---

ACMECert::loadAccountKey

Load account key.

public void ACMECert::loadAccountKey ( mixed $account_key_pem )

Parameters

account_key_pem

can be one of the following:

• a string containing a PEM formatted private key.
• a string beginning with file:// containing the filename to read a PEM formatted private key from.

Return Values

No value is returned.

Errors/Exceptions

Throws an Exception if the account key could not be loaded.

---

ACMECert::register

Associate the loaded account key with a Let's Encrypt account and optionally specify contacts.

public array ACMECert::register ( bool $termsOfServiceAgreed = FALSE [, mixed $contacts = array() ] )

Parameters

termsOfServiceAgreed

WARNING: By passing TRUE, you agree to the terms of service of Let's Encrypt. See Let’s Encrypt Subscriber Agreement for more information.

Must be set to TRUE in order to successully register an account.

contacts

can be one of the following:

1. A string containing an e-mail address
2. Array of e-mail adresses

Return Values

Returns an array containing the account information.

Errors/Exceptions

Throws an ACME_Exception if the server responded with an error message or an Exception if an other registration error occured.

---

ACMECert::update

Update account contacts.

public array ACMECert::update ( mixed $contacts = array() )

Parameters

contacts

can be one of the following:

• A string containing an e-mail address
• Array of e-mail adresses

Return Values

Returns an array containing the account information.

Errors/Exceptions

Throws an ACME_Exception if the server responded with an error message or an Exception if an other error occured updating the account.

---

ACMECert::getAccount

Get Account Information.

public array ACMECert::getAccount()

Return Values

Returns an array containing the account information.

Errors/Exceptions

Throws an ACME_Exception if the server responded with an error message or an Exception if an other error occured getting the account information.

---

ACMECert::getAccountID

Get Account ID.

public string ACMECert::getAccountID()

Return Values

Returns the Account ID

Errors/Exceptions

Throws an ACME_Exception if the server responded with an error message or an Exception if an other error occured getting the account id.

---

ACMECert::keyChange

Account Key Roll-over (exchange the current account key with another one).

If the Account Key Roll-over succeeded, the new account key is automatically loaded via loadAccountKey

public array ACMECert::keyChange ( mixed $new_account_key_pem )

Parameters

new_account_key_pem

can be one of the following:

• a string containing a PEM formatted private key.
• a string beginning with file:// containing the filename to read a PEM formatted private key from.

Return Values

Returns an array containing the account information.

Errors/Exceptions

Throws an ACME_Exception if the server responded with an error message or an Exception if an other error occured during key change.

---

ACMECert::deactivateAccount

Deactivate account.

public array ACMECert::deactivateAccount()

Return Values

Returns an array containing the account information.

Errors/Exceptions

Throws an ACME_Exception if the server responded with an error message or an Exception if an other error occured during account deactivation.

---

ACMECert::getCertificateChain

Get certificate-chain (certificate + the intermediate certificate).

This is what Apache >= 2.4.8 needs for SSLCertificateFile, and what Nginx needs for ssl_certificate.

public string ACMECert::getCertificateChain ( mixed $pem, array $domain_config, callable $callback, bool $authz_reuse = TRUE )

Parameters

pem

A Private Key used for the certificate (the needed CSR is generated automatically using the given key in this case) or an already existing CSR in one of the following formats:

• a string containing a PEM formatted private key.
• a string beginning with file:// containing the filename to read a PEM encoded private key from.
  or
• a string beginning with file:// containing the filename to read a PEM encoded CSR from.
• a string containing the content of a CSR, PEM encoded, may start with -----BEGIN CERTIFICATE REQUEST-----

domain_config

An Array defining the domains and the corresponding challenge types to get a certificate for (up to 100 domains per certificate).

The first one is used as Common Name for the certificate.

Here is an example structure:

$domain_config=array(
  '*.example.com'=>array('challenge'=>'dns-01'),
  'test.example.org'=>array('challenge'=>'tls-alpn-01')
  'test.example.net'=>array('challenge'=>'http-01','docroot'=>'/var/www/vhosts/test1.example.com'),
);

Hint: Wildcard certificates (*.example.com) are only supported with the dns-01 challenge type.

challenge is mandatory and has to be one of http-01, dns-01 or tls-alpn-01. All other keys are optional and up to you to be used and are later available in the callback function as $opts['config'] (see the http-01 example where docroot is used this way)

callback

Callback function which gets invoked every time a challenge needs to be fulfilled.

callable callback ( array $opts )

Inside a callback function you can return another callback function, which gets invoked after the verification completed and the challenge tokens can be removed again.

Hint: To get access to variables of the parent scope inside the callback function use the use languange construct:

$handler=function($opts) use ($variable_from_parent_scope){};
                         ^^^

Parameters

opts

$opts['domain']

Domain name to be validated.

$opts['config']

Corresponding element of the domain_config array.

$opts['key'] and $opts['value']

Contain the following, depending on the chosen challenge type:

Challenge Type	$opts['key']	$opts['value']
http-01	path + filename	file contents
dns-01	TXT Resource Record Name	TXT Resource Record Value
tls-alpn-01	unused	token used in the acmeIdentifier extension of the verification certificate; use generateALPNCertificate to generate the verification certificate from that token. (see the tls-alpn-01 example)

authz_reuse (default: TRUE)

If FALSE the callback function is always called for each domain and does not get skipped due to possibly already valid authorizations (authz) that are reused. This is achieved by deactivating already valid authorizations before getting new ones.

Hint: Under normal circumstances this is only needed when testing the callback function, not in production!

Return Values

Returns a PEM encoded certificate chain.

Errors/Exceptions

Throws an ACME_Exception if the server responded with an error message or an Exception if an other error occured obtaining the certificate.

---

ACMECert::revoke

Revoke certificate.

public void ACMECert::revoke ( mixed $pem )

Parameters

pem

can be one of the following:

• a string beginning with file:// containing the filename to read a PEM encoded certificate or certificate-chain from.
• a string containing the content of a certificate or certificate-chain, PEM encoded, may start with -----BEGIN CERTIFICATE-----

Return Values

No value is returned.

If the function completes without Exception, the certificate was successully revoked.

Errors/Exceptions

Throws an ACME_Exception if the server responded with an error message or an Exception if an other error occured revoking the certificate.

---

ACMECert::generateCSR

Generate CSR for a set of domains.

public string ACMECert::generateCSR ( mixed $private_key, array $domains )

Parameters

private_key

can be one of the following:

• a string containing a PEM formatted private key.
• a string beginning with file:// containing the filename to read a PEM formatted private key from.

domains

Array of domains

Return Values

Returns the generated CSR as string.

Errors/Exceptions

Throws an Exception if the CSR could not be generated.

---

ACMECert::generateALPNCertificate

Generate a self signed verification certificate containing the acmeIdentifier extension used in tls-alpn-01 challenge.

public string ACMECert::generateALPNCertificate ( mixed $private_key, string $domain, string $token )

Parameters

private_key

private key used for the certificate.

can be one of the following:

• a string containing a PEM formatted private key.
• a string beginning with file:// containing the filename to read a PEM formatted private key from.

domain

domain name to be validated.

token

verification token.

Return Values

Returns a PEM encoded verification certificate.

Errors/Exceptions

Throws an Exception if the certificate could not be generated.

---

ACMECert::parseCertificate

Get information about a certificate.

public array ACMECert::parseCertificate ( mixed $pem )

Parameters

pem

can be one of the following:

• a string beginning with file:// containing the filename to read a PEM encoded certificate or certificate-chain from.
• a string containing the content of a certificate or certificate-chain, PEM encoded, may start with -----BEGIN CERTIFICATE-----

Return Values

Returns an array containing information about the certificate.

Errors/Exceptions

Throws an Exception if the certificate could not be parsed.

---

ACMECert::getRemainingDays

Get the number of days the certificate is still valid.

public float ACMECert::getRemainingDays ( mixed $pem )

Parameters

pem

can be one of the following:

• a string beginning with file:// containing the filename to read a PEM encoded certificate or certificate-chain from.
• a string containing the content of a certificate or certificate-chain, PEM encoded, may start with -----BEGIN CERTIFICATE-----

Return Values

Returns how many days the certificate is still valid.

Errors/Exceptions

Throws an Exception if the certificate could not be parsed.

---

MIT License

Copyright (c) 2018 Stefan Körfgen

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.