feat: add ed25519 support to JWK (public keys)

Reference documentation:
https://datatracker.ietf.org/doc/html/rfc8037

Author: edudobay

src/JWK.php

@@ -6,6 +6,8 @@
 use InvalidArgumentException;
 use UnexpectedValueException;
 
+use function in_array;
+
 /**
  * JSON Web Key implementation, based on this spec:
  * https://tools.ietf.org/html/draft-ietf-jose-json-web-key-41
@@ -30,6 +32,11 @@ class JWK
         // 'P-521' => '1.3.132.0.35', // Len: 132 (not supported)
     ];
 
+    // 'crv' identifier => JWT 'alg'
+    private const OKP_CURVES = [
+        'Ed25519' => 'EdDSA',
+    ];
+
     /**
      * Parse a set of JWK keys
      *
@@ -96,11 +103,17 @@ public static function parseKey(array $jwk, string $defaultAlg = null): ?Key
             throw new UnexpectedValueException('JWK must contain a "kty" parameter');
         }
 
-        if (!isset($jwk['alg'])) {
+        $ktyNotRequiringAlg = [
+            // In Octet Key Pair (OKP) keys, the signing algorithm (alg) will not be read from the
+            // JWK, as it can be inferred directly from the curve type (crv).
+            // @see https://datatracker.ietf.org/doc/html/rfc8037#section-3.1
+            'OKP',
+        ];
+        if (!isset($jwk['alg']) && !in_array($jwk['kty'], $ktyNotRequiringAlg, true)) {
             if (\is_null($defaultAlg)) {
                 // The "alg" parameter is optional in a KTY, but an algorithm is required
-                // for parsing in this library. Use the $defaultAlg parameter when parsing the
-                // key set in order to prevent this error.
+                // for parsing certain key types in this library. Use the $defaultAlg parameter
+                // when parsing the key set in order to prevent this error.
                 // @see https://datatracker.ietf.org/doc/html/rfc7517#section-4.4
                 throw new UnexpectedValueException('JWK must contain an "alg" parameter');
             }
@@ -144,8 +157,28 @@ public static function parseKey(array $jwk, string $defaultAlg = null): ?Key
 
                 $publicKey = self::createPemFromCrvAndXYCoordinates($jwk['crv'], $jwk['x'], $jwk['y']);
                 return new Key($publicKey, $jwk['alg']);
+            case 'OKP':
+                if (isset($jwk['d'])) {
+                    // The key is actually a private key
+                    throw new UnexpectedValueException('Key data must be for a public key');
+                }
+
+                if (! isset($jwk['crv'])) {
+                    throw new UnexpectedValueException('crv not set');
+                }
+
+                if (!isset(self::OKP_CURVES[$jwk['crv']])) {
+                    throw new DomainException('Unrecognised or unsupported OKP curve');
+                }
+
+                if (empty($jwk['x'])) {
+                    throw new UnexpectedValueException('x not set');
+                }
+
+                $publicKey = \base64_encode(JWT::urlsafeB64Decode($jwk['x']));
+                $alg = self::OKP_CURVES[$jwk['crv']];
+                return new Key($publicKey, $alg);
             default:
-                // Currently only RSA is supported
                 break;
         }
 

src/JWT.php

@@ -210,7 +210,7 @@ public static function encode(
      *
      * @param string $msg  The message to sign
      * @param string|resource|OpenSSLAsymmetricKey|OpenSSLCertificate  $key  The secret key.
-     * @param string $alg  Supported algorithms are 'ES384','ES256', 'HS256', 'HS384',
+     * @param string $alg  Supported algorithms are 'EdDSA', 'ES384', 'ES256', 'HS256', 'HS384',
      *                    'HS512', 'RS256', 'RS384', and 'RS512'
      *
      * @return string An encrypted message
@@ -270,7 +270,7 @@ public static function sign(
      *
      * @param string $msg         The original message (header and body)
      * @param string $signature   The original signature
-     * @param string|resource|OpenSSLAsymmetricKey|OpenSSLCertificate  $keyMaterial For HS*, a string key works. for RS*, must be an instance of OpenSSLAsymmetricKey
+     * @param string|resource|OpenSSLAsymmetricKey|OpenSSLCertificate  $keyMaterial For Ed*, ES*, HS*, a string key works. for RS*, must be an instance of OpenSSLAsymmetricKey
      * @param string $alg         The algorithm
      *
      * @return bool

tests/JWKTest.php

@@ -151,6 +151,7 @@ public function provideDecodeByJwkKeySet()
         return [
             ['rsa1-private.pem', 'rsa-jwkset.json', 'RS256'],
             ['ecdsa256-private.pem', 'ec-jwkset.json', 'ES256'],
+            ['ed25519-1.sec', 'ed25519-jwkset.json', 'EdDSA'],
         ];
     }
 

tests/data/ed25519-jwkset.json

@@ -0,0 +1,10 @@
+{
+    "keys": [
+        {
+            "kid": "jwk1",
+            "kty": "OKP",
+            "crv": "Ed25519",
+            "x": "uOSJMhbKSG4V5xUHS7B9YHmVg_1yVd-G-Io6oBFhSfY"
+        }
+    ]
+}