GPG-Mailer

Send GPG-encrypted emails (using zend-mail and Crypt_GPG).

License: MIT

The GPG-Mailer API in a Nutshell

/**
 * Import a public key, return the fingerprint
 *
 * @param string $gpgKey An ASCII armored public key
 * @return string The GPG fingerprint for this key
 */
public function import(string $gpgKey): string;

/**
 * Get the public key corresponding to a fingerprint.
 *
 * @param string $fingerprint
 * @return string
 */
public function export(string $fingerprint): string;

/**
 * Encrypt then email a message
 *
 * @param Message $message    The message data
 * @param string $fingerprint Which public key fingerprint to use
 */
public function send(Message $message, string $fingerprint);

/**
 * Email a message without encrypting it.
 *
 * @param Message $message The message data
 * @param bool $force      Send even if we don't have a private key?
 */
public function sendUnencrypted(Message $message, bool $force = false);

Example: Encrypt Outbound Emails with Your GnuPG Public Key

<?php
use \ParagonIE\GPGMailer\GPGMailer;
use \Zend\Mail\Message;
use \Zend\Mail\Transport\Sendmail;

// First, create a Zend\Mail message as usual:
$message = new Message;
$message->addTo('[email protected]', 'Test Email');
$message->setBody('Cleartext for now. Do not worry; this gets encrypted.');

// Instantiate GPGMailer:
$gpgMailer = new GPGMailer(
    new Sendmail(), 
    ['homedir' => '/homedir/containing/keyring']
);

// GPG public key for <[email protected]> (fingerprint):
$fingerprint = '7F52D5C61D1255C731362E826B97A1C2826404DA';

// Finally:
$gpgMailer->send($message, $fingerprint); 

If you're encrypting with a user provided public key (and they didn't tell you their fingerprint), do this instead:

<?php

/**
 * Output from: gpg --armor --export [email protected]
 *
 * This is our security team's GPG public key. You probably don't
 * want to use ours, as only we can decrypt the messages.
 *
 * @var string 
 */
$ASCIIArmoredPublicKey = "-----BEGIN PGP PUBLIC KEY BLOCK-----
Version: SKS 1.1.5
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OHdggnRtmm/0wVu38GLz8SgYl4Q/IccbKiXnbsPZDvtXCyviFNT+Shve017uJFjQtz9lUGqf
+w/o2g3By9bGjIDSOvmgY7i0HF2B4GMZK4B7MT1haJ/ObIDKPyqRxrunvUSh38bv6KZc5F+V
/4u7qz4Wy03rC8HHSJan5yuxUCQXgMIopk5DOcCvKQ6GAq0WPwPWy0EgSPjbjxpHeSx9lgsI
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7JWU0HJS2o71r1hwp05Zvy21kcUEobz/WWQQyGS0Neo7PJn+9KS6wOxXul/UE0jct/5f7KLM
dWMJ1VgniQmmhjvkHLPSICteqCI04RfcmMseW9gueHQXeUu1SNIvsWa2MhxjeBej3pDnrZWs
zKwygF45GO9/v4tkIXNMy5J1AtOyRgQ3IUMqp8EAEQEAAYkBHwQYAQIACQUCVSDBFQIbDAAK
CRBrl6HCgmQE2jnIB/4/xFz8InpM7eybnBOAir3uGcYfs3DOmaKn7qWVtGzvrKpQPYnVtlU2
i6Z5UO4c4jDLT/8Xm1UDz3Lxvqt4xCaDwJvBZexU5BMK8l5DvOzH6o6P2L1UDu6BvmPXpVZz
7/qUhOnyf8VQg/dAtYF4/ax19giNUpI5j5o5mX5w80RxqSXV9NdSL4fdjeG1g/xXv2luhoV5
3T1bsycI3wjk/x5tV+M2KVhZBvvuOm/zhJjeoLWp0saaESkGXIXqurj6gZoujJvSvzl0n9F9
VwqMEizDUfrXgtD1siQGhP0sVC6qha+F/SAEJ0jEquM4TfKWWU2S5V5vgPPpIQSYRnhQW4b1
=Z4m0
-----END PGP PUBLIC KEY BLOCK-----";

// Then to import.
$fingerprint = $gpgMailer->import($ASCIIArmoredPublicKey);

Sign Emails with the Server's Private Key

Signed and Encrypted

To add signing, we pass the signing key to the third argument of the GPGMailer constructor.

<?php

use \ParagonIE\GPGMailer\GPGMailer;
use \Zend\Mail\Message;
use \Zend\Mail\Transport\Sendmail;

// First, create a Zend\Mail message as usual:
$message = new Message;
$message->addTo('[email protected]', 'Test Email');
$message->setBody('Cleartext for now. Do not worry; this gets encrypted.');

$signingKey = file_get_contents('tests/private.key');

// Instantiate GPGMailer:
$gpgMailer = new GPGMailer(
    new Sendmail(), 
    ['homedir' => '/homedir/containing/keyring'],
    $signingKey
);

// GPG public key for <[email protected]> (fingerprint):
$fingerprint = '7F52D5C61D1255C731362E826B97A1C2826404DA';

// Finally:
$gpgMailer->send($message, $fingerprint); 

Alternatively, we could define our constructor as above but then use setPrivateKey() like so:

$gpgMailer = new GPGMailer(
    new Sendmail(), 
    ['homedir' => '/homedir/containing/keyring']
);

$signingKey = file_get_contents('tests/private.key');
$gpgMailer->setPrivateKey($signingKey);

Signed, But Not Encrypted

Same as above, except we don't need to load the recipient's fingerprint and we use the sendUnencrypted() method instead.

<?php
use \ParagonIE\GPGMailer\GPGMailer;
use \Zend\Mail\Message;
use \Zend\Mail\Transport\Sendmail;

// First, create a Zend\Mail message as usual:
$message = new Message;
$message->addTo('[email protected]', 'Test Email');
$message->setBody('Cleartext for now. Do not worry; this gets encrypted.');

$signingKey = file_get_contents('tests/private.key');

$gpgMailer = new GPGMailer(
    new Sendmail(), 
    ['homedir' => '/homedir/containing/keyring'],
    $signingKey
);

$gpgMailer->sendUnencrypted($message); 

Support Contracts

If your company uses this library in their products or services, you may be interested in purchasing a support contract from Paragon Initiative Enterprises.