feat: add support for W3C ES256K (#462)

Author: scrummitch

Diff for: src/JWK.php

@@ -26,6 +26,7 @@ class JWK
     private const ASN1_BIT_STRING = 0x03;
     private const EC_CURVES = [
         'P-256' => '1.2.840.10045.3.1.7', // Len: 64
+        'secp256k1' => '1.3.132.0.10', // Len: 64
         // 'P-384' => '1.3.132.0.34', // Len: 96 (not yet supported)
         // 'P-521' => '1.3.132.0.35', // Len: 132 (not supported)
     ];

Diff for: src/JWT.php

@@ -55,6 +55,7 @@ class JWT
     public static $supported_algs = [
         'ES384' => ['openssl', 'SHA384'],
         'ES256' => ['openssl', 'SHA256'],
+        'ES256K' => ['openssl', 'SHA256'],
         'HS256' => ['hash_hmac', 'SHA256'],
         'HS384' => ['hash_hmac', 'SHA384'],
         'HS512' => ['hash_hmac', 'SHA512'],
@@ -132,8 +133,8 @@ public static function decode(
             // See issue #351
             throw new UnexpectedValueException('Incorrect key for this algorithm');
         }
-        if ($header->alg === 'ES256' || $header->alg === 'ES384') {
-            // OpenSSL expects an ASN.1 DER sequence for ES256/ES384 signatures
+        if (\in_array($header->alg, ['ES256', 'ES256K', 'ES384'], true)) {
+            // OpenSSL expects an ASN.1 DER sequence for ES256/ES256K/ES384 signatures
             $sig = self::signatureToDER($sig);
         }
         if (!self::verify("{$headb64}.{$bodyb64}", $sig, $key->getKeyMaterial(), $header->alg)) {
@@ -170,8 +171,8 @@ public static function decode(
      *
      * @param array<mixed>          $payload PHP array
      * @param string|resource|OpenSSLAsymmetricKey|OpenSSLCertificate $key The secret key.
-     * @param string                $alg     Supported algorithms are 'ES384','ES256', 'HS256', 'HS384',
-     *                                       'HS512', 'RS256', 'RS384', and 'RS512'
+     * @param string                $alg     Supported algorithms are 'ES384','ES256', 'ES256K', 'HS256',
+     *                                       'HS384', 'HS512', 'RS256', 'RS384', and 'RS512'
      * @param string                $keyId
      * @param array<string, string> $head    An array with header elements to attach
      *
@@ -210,8 +211,8 @@ 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',
-     *                    'HS512', 'RS256', 'RS384', and 'RS512'
+     * @param string $alg  Supported algorithms are 'ES384','ES256', 'ES256K', 'HS256',
+     *                    'HS384', 'HS512', 'RS256', 'RS384', and 'RS512'
      *
      * @return string An encrypted message
      *
@@ -238,7 +239,7 @@ public static function sign(
                 if (!$success) {
                     throw new DomainException('OpenSSL unable to sign data');
                 }
-                if ($alg === 'ES256') {
+                if ($alg === 'ES256' || $alg === 'ES256K') {
                     $signature = self::signatureFromDER($signature, 256);
                 } elseif ($alg === 'ES384') {
                     $signature = self::signatureFromDER($signature, 384);

Diff for: tests/JWTTest.php

@@ -377,6 +377,7 @@ public function provideEncodeDecode()
             [__DIR__ . '/data/ecdsa384-private.pem', __DIR__ . '/data/ecdsa384-public.pem', 'ES384'],
             [__DIR__ . '/data/rsa1-private.pem', __DIR__ . '/data/rsa1-public.pub', 'RS512'],
             [__DIR__ . '/data/ed25519-1.sec', __DIR__ . '/data/ed25519-1.pub', 'EdDSA'],
+            [__DIR__ . '/data/secp256k1-private.pem', __DIR__ . '/data/secp256k1-public.pem', 'ES256K'],
         ];
     }
 

Diff for: tests/data/ec-jwkset.json

@@ -17,6 +17,15 @@
             "x": "mQa0q5FvxPRujxzFazQT1Mo2YJJzuKiXU3svOJ41jhw",
             "y": "jAz7UwIl2oOFk06kj42ZFMOXmGMFUGjKASvyYtibCH0",
             "alg": "ES256"
+        },
+        {
+            "kty": "EC",
+            "use": "sig",
+            "crv": "secp256k1",
+            "kid": "jwk3",
+            "x": "EFpwNuP322bU3WP1DtJgx67L0CUV1MxNixqPVMH2L9Q",
+            "y": "_fSTbijIJjpsqL16cIEvxxf3MaYMY8MbqEq066yV9ls",
+            "alg": "ES256K"
         }
     ]
 }

Diff for: tests/data/secp256k1-private.pem

@@ -0,0 +1,5 @@
+-----BEGIN PRIVATE KEY-----
+MIGEAgEAMBAGByqGSM49AgEGBSuBBAAKBG0wawIBAQQgC8ouvv1ZOmOjh5Nbwx6i
+3b35wWN+OEkW2hzm3BKAQJ2hRANCAAT9nYGLVP6Unm/LXOoyWhsKpalffMSr3EHV
+iUE8gVmj2/atnPkblx38Yj6bC3z1urERAB+JqgpWOAKaWcEYCUuO
+-----END PRIVATE KEY-----

Diff for: tests/data/secp256k1-public.pem

@@ -0,0 +1,4 @@
+-----BEGIN PUBLIC KEY-----
+MFYwEAYHKoZIzj0CAQYFK4EEAAoDQgAE/Z2Bi1T+lJ5vy1zqMlobCqWpX3zEq9xB
+1YlBPIFZo9v2rZz5G5cd/GI+mwt89bqxEQAfiaoKVjgCmlnBGAlLjg==
+-----END PUBLIC KEY-----