Blake2b added as an experimental algorithm (#367)

Author: Spomky

Diff for: Blake2b.php

@@ -0,0 +1,61 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Jose\Component\Signature\Algorithm;
+
+use function in_array;
+use InvalidArgumentException;
+use function is_string;
+use Jose\Component\Core\JWK;
+use ParagonIE\ConstantTime\Base64UrlSafe;
+
+/**
+ * @see \Jose\Tests\Component\Signature\Algorithm\Blake2bTest
+ */
+final class Blake2b implements MacAlgorithm
+{
+    private const MINIMUM_KEY_LENGTH = 32;
+
+    public function allowedKeyTypes(): array
+    {
+        return ['oct'];
+    }
+
+    public function name(): string
+    {
+        return 'BLAKE2B';
+    }
+
+    public function verify(JWK $key, string $input, string $signature): bool
+    {
+        return hash_equals($this->hash($key, $input), $signature);
+    }
+
+    public function hash(JWK $key, string $input): string
+    {
+        $k = $this->getKey($key);
+
+        return sodium_crypto_generichash($input, $k);
+    }
+
+    private function getKey(JWK $key): string
+    {
+        if (! in_array($key->get('kty'), $this->allowedKeyTypes(), true)) {
+            throw new InvalidArgumentException('Wrong key type.');
+        }
+        if (! $key->has('k')) {
+            throw new InvalidArgumentException('The key parameter "k" is missing.');
+        }
+        $k = $key->get('k');
+        if (! is_string($k)) {
+            throw new InvalidArgumentException('The key parameter "k" is invalid.');
+        }
+        $key = Base64UrlSafe::decode($k);
+        if (mb_strlen($key, '8bit') < self::MINIMUM_KEY_LENGTH) {
+            throw new InvalidArgumentException('Key provided is shorter than 256 bits.');
+        }
+
+        return $key;
+    }
+}