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Chapter 6. Secure your communication

[Warning]

This chapter is only for reader that use the GNTP adapter. Even if UDP is binary format protocol, it shouldn’t be considered as secure.

GNTP is a MIME like format, contents are sent as readable plain text. You should think to use either :

We will see now, how to encrypt your data and what formats are supported.

The authorization of messages is accomplished by passing key information that proves that the sending application knows a shared secret with the notification system, namely a password. Users that want to authorize applications must share with them a password that will be used for both authorization and encryption.

[Note]

By default, authorization is not required for requests orginating on the local machine.

Table 6.1. The supported hashing algorithms

HashFeatures

MD5

128-bit, 16 byte, 32 character length when hex encoded

SHA1

160-bit, 20 byte, 40 character length when hex encoded

SHA256

256-bit, 32 byte, 64 character length when hex encoded

SHA512

512-bit, 64 byte, 128 character length when hex encoded


Table 6.2. The supported encryption algorithms

HashFeatures

NONE

No encryption; messages are sent in plain text

AES

key length: 24 bytes (192 bit), block size: 16 byte (128 bit), iv size: 16 byte (128 bit)

DES

key length: 8 bytes (64 bit), block size: 8 byte (64 bit), iv size: 8 byte (64 bit)

3DES

key length: 24 bytes (192 bit), block size: 8 byte (64 bit), iv size: 8 byte (64 bit)


[Note]

All encryption algorithms should use a block mode of CBC (Cipher Block Chaining) and PKCS5 (PKCS7) padding.

[Important]

It is important to keep in mind that some encryption algorithms require keys that are longer than can be generated by some hashing algorithms. As such, not all hash/encryption combinations are valid (ex: MD5 hash produces a 16 byte result, but AES encryption requires a 24-byte key).

Table 6.3. Hash and Encryption algorithms compatibilities

EncryptionHash

AES

SHA256, SHA512

DES

MD5, SHA1, SHA256, SHA512

3DES

SHA256, SHA512


To encrypt your data, its very easy. You have just to specify in options of Net_Growl::singleton method :

Example 6.1. encrypted messages with AES/SHA256

<?php
require_once 'Net/Growl/Autoload.php';

$notifications = array(
    'GROWL_NOTIFY_PHPERROR'
);
$appName  = 'PHP App Example using GNTP/encrypt AES';
$password = 'mamasam';

$app = new Net_Growl_Application(
    $appName,
    $notifications,
    $password
);
$options = array(
    'host'     => '127.0.0.1',
    'protocol' => 'tcp',
    'port'     => Net_Growl::GNTP_PORT,
    'timeout'  => 10,
    'encryptionAlgorithm'   => 'AES',
    'passwordHashAlgorithm' => 'SHA256',
);

try {
    $growl = Net_Growl::singleton($app, null, null, $options);
    $growl->register();

    $title       = 'Welcome in PHP/GNTP world';
    $description = "New GNTP protocol support 3 encryption algorithms ! \n"
                 . "DES, 3DES, AES with 4 hash algorithm \n"
                 . "MD5, SHA1, SHA256, SHA512.";
    $options     = array(
        'sticky' => true,
    );
    $growl->notify($name, $title, $description, $options);

} catch (Net_Growl_Exception $e) {
    echo 'Growl exception: ' . $e->getMessage() . PHP_EOL;
}
?>

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