Add utility class to create JWKs JSON from public key.

Author: Potherca

src/Utils/Jwks.php

@@ -0,0 +1,77 @@
+<?php
+
+namespace Pdsinterop\Solid\Auth\Utils;
+
+use JsonSerializable;
+use Lcobucci\JWT\Signer\Key;
+use Pdsinterop\Solid\Auth\Enum\Jwk\Parameter as JwkParameter;
+use Pdsinterop\Solid\Auth\Enum\Rsa\Parameter as RsaParameter;
+
+class Jwks implements JsonSerializable
+{
+    ////////////////////////////// CLASS PROPERTIES \\\\\\\\\\\\\\\\\\\\\\\\\\\\
+
+    /** @var Key */
+    private $publicKey;
+
+    //////////////////////////////// PUBLIC API \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
+
+    final public function __construct(Key $publicKey)
+    {
+        $this->publicKey = $publicKey;
+    }
+
+    final public function __toString() : string
+    {
+        return (string) json_encode($this);
+    }
+
+    final public function jsonSerialize()
+    {
+        return $this->create();
+    }
+
+    ////////////////////////////// UTILITY METHODS \\\\\\\\\\\\\\\\\\\\\\\\\\\\\
+
+    /**
+     * @param string $certificate
+     * @param $subject
+     *
+     * @return array
+     */
+    private function createKey(string $certificate, $subject) : array
+    {
+        return [
+            JwkParameter::ALGORITHM => 'RS256',
+            JwkParameter::KEY_ID => md5($certificate),
+            JwkParameter::KEY_TYPE => 'RSA',
+            RsaParameter::PUBLIC_EXPONENT => 'AQAB', // Hard-coded as `Base64Url::encode($keyInfo['rsa']['e'])` tends to be empty...
+            RsaParameter::PUBLIC_MODULUS => Base64Url::encode($subject),
+        ];
+    }
+
+    /**
+     * As the JWT library does not (yet?) have support for JWK, a custom solution is used for now.
+     *
+     * @return array
+     *
+     * @see https://github.com/lcobucci/jwt/issues/32
+     */
+    private function create() : array
+    {
+        $jwks = ['keys' => []];
+
+        $publicKeys = [$this->publicKey];
+
+        array_walk($publicKeys, function (Key $publicKey) use (&$jwks) {
+            $certificate = $publicKey->getContent();
+
+            $key = openssl_pkey_get_public($certificate);
+            $keyInfo = openssl_pkey_get_details($key);
+
+            $jwks['keys'][] = $this->createKey($certificate, $keyInfo['rsa']['n']);
+        });
+
+        return $jwks;
+    }
+}