Make lib more performant by allowing to provide local key objects and shared secrets

[marcvdm]

This pull request adds the ability to generate the local keys before hand and provide them to the WebPush client. This way it does not generate a new local key object for each notification.

This also opens the possibility to generate the shared secret before hand so that this is also skipped when you send the notification.

Here is an example:

Generate the local public and private key and store them

use Jose\Component\Core\Util\Ecc\NistCurve;
use Minishlink\WebPush\Encryption;
use Minishlink\WebPush\Utils;
use Base64Url\Base64Url;

[$localPublicKeyObject, $localPrivateKeyObject] = Encryption::createLocalKeyObject();

// Store these variables
$localPublicKey = Base64Url::encode(Utils::serializePublicKey($localPublicKeyObject));
$localPrivateKey = Base64Url::encode(Utils::serializePrivateKey($localPrivateKeyObject));

When a user subscribes we generate the shared secret and store it with all the other info

use Minishlink\WebPush\Encryption;
use Minishlink\WebPush\Utils;
use Base64Url\Base64Url;

$localPrivateKey = Base64Url::decode('storedLocalPrivateKey');
$userPublicKey = "TheUsersPublicKey";

// Store the shared secret with the subscription
$sharedSecret = Encryption::createSharedSecret($userPublicKey, Utils::unserializePrivateKey($localPrivateKey));

When you want to send a notification

use Minishlink\WebPush\Encryption;
use Minishlink\WebPush\Utils;
use Base64Url\Base64Url;

$localPublicKey = 'storedLocalPublicKey';
$localPrivateKey = 'storedLocalPrivateKey';

$webPush = new WebPush();
$webPush->setLocalKeys($localPublicKey, $localPrivateKey);

$endpoint = 'endpoint'; // From your data store
$publicKey = 'publicKey'; // From your data store
$authToken = 'authToken'; // From your data store
$contentEncoding= 'contentEncoding'; // From your data store
$sharedSecret = 'sharedSecret'; // From your data store, previously created

$subscriptions = new Subscription($endpoint, $publicKey, $authToken, $contentEncoding, $sharedSecret);

$webPush->sendNotification($subscription, '{"test":"payload"}');

[Minishlink]

This looks cool!
Can you rebase and fix the static errors please ?

[marcvdm]

Fixed the static errors, is it possible for you to rebase and merge pull request?

[marcvdm]

Pinging @Minishlink Can we move forward with this? I'm unable to rebase the current merge request

[Minishlink]

@marcvdm Thanks Marc, I'll work on it probably this week-end

[marcvdm]

Closing this merge request for the rebased version #227