Add JWK support for HMAC and RSA keys

jwt/algorithms.py

@@ -1,17 +1,22 @@
 import hashlib
 import hmac
+import json
 
 from .compat import constant_time_compare, string_types, text_type
 from .exceptions import InvalidKeyError
-from .utils import der_to_raw_signature, raw_to_der_signature
+from .utils import (
+    base64url_decode, base64url_encode, der_to_raw_signature,
+    from_base64url_uint, raw_to_der_signature, to_base64url_uint
+)
 
 try:
     from cryptography.hazmat.primitives import hashes
     from cryptography.hazmat.primitives.serialization import (
         load_pem_private_key, load_pem_public_key, load_ssh_public_key
     )
     from cryptography.hazmat.primitives.asymmetric.rsa import (
-        RSAPrivateKey, RSAPublicKey
+        RSAPrivateKey, RSAPublicKey, RSAPrivateNumbers, RSAPublicNumbers,
+        rsa_recover_prime_factors, rsa_crt_dmp1, rsa_crt_dmq1, rsa_crt_iqmp
     )
     from cryptography.hazmat.primitives.asymmetric.ec import (
         EllipticCurvePrivateKey, EllipticCurvePublicKey
@@ -77,6 +82,18 @@ def verify(self, msg, key, sig):
         """
         raise NotImplementedError
 
+    def to_jwk(self, key_obj):
+        """
+        Serializes a given RSA key into a JWK
+        """
+        raise NotImplementedError
+
+    def from_jwk(self, jwk):
+        """
+        Deserializes a given RSA key from JWK back into a PublicKey or PrivateKey object
+        """
+        return NotImplementedError
+
 
 class NoneAlgorithm(Algorithm):
     """
@@ -92,6 +109,14 @@ def prepare_key(self, key):
 
         return key
 
+    @staticmethod
+    def to_jwk(key_obj):
+        return {}
+
+    @staticmethod
+    def from_jwk(jwk):
+        return None
+
     def sign(self, msg, key):
         return b''
 
@@ -131,6 +156,22 @@ def prepare_key(self, key):
 
         return key
 
+    @staticmethod
+    def to_jwk(key_obj):
+        return json.dumps({
+            'k': base64url_encode(key_obj),
+            'typ': 'oct'
+        })
+
+    @staticmethod
+    def from_jwk(jwk):
+        obj = json.loads(jwk)
+
+        if obj.get('kty') != 'oct':
+            raise InvalidKeyError('Not an HMAC key')
+
+        return base64url_decode(obj['k'])
+
     def sign(self, msg, key):
         return hmac.new(key, msg, self.hash_alg).digest()
 
@@ -172,6 +213,101 @@ def prepare_key(self, key):
 
             return key
 
+        @staticmethod
+        def to_jwk(key_obj):
+            obj = None
+
+            if getattr(key_obj, 'private_numbers', None):
+                # Private key
+                numbers = key_obj.private_numbers()
+
+                obj = {
+                    'kty': 'RSA',
+                    'key_ops': ['sign'],
+                    'd': to_base64url_uint(numbers.d),
+                    'p': to_base64url_uint(numbers.p),
+                    'q': to_base64url_uint(numbers.q),
+                    'dp': to_base64url_uint(numbers.dmp1),
+                    'dq': to_base64url_uint(numbers.dmq1),
+                    'qi': to_base64url_uint(numbers.iqmp)
+                }
+
+            elif getattr(key_obj, 'verifier', None):
+                # Public key
+                numbers = key_obj.public_numbers()
+
+                obj = {
+                    'kty': 'RSA',
+                    'use': 'sig',
+                    'key_ops': ['verify'],
+                    'n': to_base64url_uint(numbers.n),
+                    'e': to_base64url_uint(numbers.e)
+                }
+            else:
+                raise InvalidKeyError('Not a public or private key')
+
+            return json.dumps(obj)
+
+        @staticmethod
+        def from_jwk(jwk):
+            obj = json.loads(jwk)
+
+            if obj.get('kty') != 'RSA':
+                raise InvalidKeyError('Not an RSA key')
+
+            if 'd' in obj and 'e' in obj and 'n' in obj:
+                # Private key
+                if 'oth' in obj:
+                    raise InvalidKeyError('Unsupported RSA private key: > 2 primes not supported')
+
+                other_props = ['p', 'q', 'dp', 'dq', 'qi']
+                props_found = [True for prop in other_props if prop in obj]
+                any_props_found = any(props_found)
+
+                if any_props_found and not all(props_found):
+                    raise InvalidKeyError('RSA key must include all parameters if any are present besides d')
+
+                public_numbers = RSAPublicNumbers(
+                    from_base64url_uint(obj['e']), from_base64url_uint(obj['n'])
+                )
+
+                if any_props_found:
+                    numbers = RSAPrivateNumbers(
+                        d=from_base64url_uint(obj['d']),
+                        p=from_base64url_uint(obj['p']),
+                        q=from_base64url_uint(obj['q']),
+                        dmp1=from_base64url_uint(obj['dp']),
+                        dmq1=from_base64url_uint(obj['dq']),
+                        iqmp=from_base64url_uint(obj['qi']),
+                        public_numbers=public_numbers
+                    )
+                else:
+                    p, q = rsa_recover_prime_factors(
+                        public_numbers.n, public_numbers.d, public_numbers.e
+                    )
+                    d = from_base64url_uint(obj['d'])
+
+                    numbers = RSAPrivateNumbers(
+                        d=d,
+                        p=p,
+                        q=q,
+                        dmp1=rsa_crt_dmp1(d, p),
+                        dmq1=rsa_crt_dmq1(d, q),
+                        iqmp=rsa_crt_iqmp(p, q),
+                        public_numbers=public_numbers
+                    )
+
+                return numbers.private_key(default_backend())
+            elif 'n' in obj and 'e' in obj:
+                # Public key
+                numbers = RSAPublicNumbers(
+                    from_base64url_uint(obj['e']), from_base64url_uint(obj['n'])
+                )
+
+                return numbers.public_key(default_backend())
+            else:
+                raise InvalidKeyError('Not a public or private key')
+
         def sign(self, msg, key):
             signer = key.signer(
                 padding.PKCS1v15(),

jwt/utils.py

@@ -1,5 +1,8 @@
 import base64
 import binascii
+import struct
+
+from .compat import text_type
 
 try:
     from cryptography.hazmat.primitives.asymmetric.utils import (
@@ -10,6 +13,9 @@
 
 
 def base64url_decode(input):
+    if isinstance(input, text_type):
+        input = input.encode('ascii')
+
     rem = len(input) % 4
 
     if rem > 0:
@@ -22,6 +28,35 @@ def base64url_encode(input):
     return base64.urlsafe_b64encode(input).replace(b'=', b'')
 
 
+def to_base64url_uint(val):
+    if val < 0:
+        raise ValueError('Must be a positive integer')
+
+    buf = []
+    while val:
+        val, remainder = divmod(val, 256)
+        buf.append(remainder)
+
+    buf.reverse()
+
+    data = struct.pack('%sB' % len(buf), *buf)
+
+    if len(data) == 0:
+        data = '\x00'
+
+    return base64url_encode(data)
+
+
+def from_base64url_uint(val):
+    if isinstance(val, text_type):
+        val = val.encode('ascii')
+
+    data = base64url_decode(val)
+
+    buf = struct.unpack('%sB' % len(data), data)
+    return int(''.join(["%02x" % byte for byte in buf]), 16)
+
+
 def merge_dict(original, updates):
     if not updates:
         return original

tests/keys/__init__.py

@@ -20,37 +20,21 @@ def load_hmac_key():
     return base64url_decode(ensure_bytes(keyobj['k']))
 
 try:
-    from cryptography.hazmat.primitives.asymmetric import rsa
     from cryptography.hazmat.primitives.asymmetric import ec
     from cryptography.hazmat.backends import default_backend
-
+    from jwt.algorithms import RSAAlgorithm
     has_crypto = True
 except ImportError:
     has_crypto = False
 
 if has_crypto:
     def load_rsa_key():
         with open(os.path.join(BASE_PATH, 'jwk_rsa_key.json'), 'r') as infile:
-            keyobj = json.load(infile)
-
-        return rsa.RSAPrivateNumbers(
-            p=decode_value(keyobj['p']),
-            q=decode_value(keyobj['q']),
-            d=decode_value(keyobj['d']),
-            dmp1=decode_value(keyobj['dp']),
-            dmq1=decode_value(keyobj['dq']),
-            iqmp=decode_value(keyobj['qi']),
-            public_numbers=load_rsa_pub_key().public_numbers()
-        ).private_key(default_backend())
+            return RSAAlgorithm.from_jwk(infile.read())
 
     def load_rsa_pub_key():
         with open(os.path.join(BASE_PATH, 'jwk_rsa_pub.json'), 'r') as infile:
-            keyobj = json.load(infile)
-
-        return rsa.RSAPublicNumbers(
-            n=decode_value(keyobj['n']),
-            e=decode_value(keyobj['e'])
-        ).public_key(default_backend())
+            return RSAAlgorithm.from_jwk(infile.read())
 
     def load_ec_key():
         with open(os.path.join(BASE_PATH, 'jwk_ec_key.json'), 'r') as infile:

tests/test_algorithms.py

@@ -88,6 +88,15 @@ def test_hmac_should_throw_exception_if_key_is_x509_cert(self):
             with open(key_path('testkey2_rsa.pub.pem'), 'r') as keyfile:
                 algo.prepare_key(keyfile.read())
 
+    def test_hmac_jwk_public_and_private_keys_should_parse_and_verify(self):
+        algo = HMACAlgorithm(HMACAlgorithm.SHA256)
+
+        with open(key_path('jwk_hmac.json'), 'r') as keyfile:
+            key = algo.from_jwk(keyfile.read())
+
+        signature = algo.sign('Hello World!', key)
+        assert algo.verify('Hello World!', key, signature)
+
     @pytest.mark.skipif(not has_crypto, reason='Not supported without cryptography library')
     def test_rsa_should_parse_pem_public_key(self):
         algo = RSAAlgorithm(RSAAlgorithm.SHA256)
@@ -131,6 +140,19 @@ def test_rsa_verify_should_return_false_if_signature_invalid(self):
         result = algo.verify(message, pub_key, sig)
         assert not result
 
+    @pytest.mark.skipif(not has_crypto, reason='Not supported without cryptography library')
+    def test_rsa_jwk_public_and_private_keys_should_parse_and_verify(self):
+        algo = RSAAlgorithm(RSAAlgorithm.SHA256)
+
+        with open(key_path('jwk_rsa_pub.json'), 'r') as keyfile:
+            pub_key = algo.from_jwk(keyfile.read())
+
+        with open(key_path('jwk_rsa_key.json'), 'r') as keyfile:
+            priv_key = algo.from_jwk(keyfile.read())
+
+        signature = algo.sign('Hello World!', priv_key)
+        assert algo.verify('Hello World!', pub_key, signature)
+
     @pytest.mark.skipif(not has_crypto, reason='Not supported without cryptography library')
     def test_ec_should_reject_non_string_key(self):
         algo = ECAlgorithm(ECAlgorithm.SHA256)