Add JWK support for HMAC and RSA keys

- JWKs for RSA and HMAC can be encoded / decoded using the .to_jwk() and
  .from_jwk() methods on their respective jwt.algorithms instances

- Replaced tests.utils ensure_unicode and ensure_bytes with jwt.utils versions

jwt/algorithms.py

@@ -1,17 +1,24 @@
 import hashlib
 import hmac
+import json
 
-from .compat import binary_type, constant_time_compare, is_string_type
+
+from .compat import constant_time_compare, string_types
 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,
+    force_bytes, force_unicode, 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 +84,20 @@ def verify(self, msg, key, sig):
         """
         raise NotImplementedError
 
+    @staticmethod
+    def to_jwk(key_obj):
+        """
+        Serializes a given RSA key into a JWK
+        """
+        raise NotImplementedError
+
+    @staticmethod
+    def from_jwk(jwk):
+        """
+        Deserializes a given RSA key from JWK back into a PublicKey or PrivateKey object
+        """
+        raise NotImplementedError
+
 
 class NoneAlgorithm(Algorithm):
     """
@@ -112,11 +133,7 @@ def __init__(self, hash_alg):
         self.hash_alg = hash_alg
 
     def prepare_key(self, key):
-        if not is_string_type(key):
-            raise TypeError('Expecting a string- or bytes-formatted key.')
-
-        if not isinstance(key, binary_type):
-            key = key.encode('utf-8')
+        key = force_bytes(key)
 
         invalid_strings = [
             b'-----BEGIN PUBLIC KEY-----',
@@ -131,6 +148,22 @@ def prepare_key(self, key):
 
         return key
 
+    @staticmethod
+    def to_jwk(key_obj):
+        return json.dumps({
+            'k': force_unicode(base64url_encode(force_bytes(key_obj))),
+            'kty': '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()
 
@@ -156,9 +189,8 @@ def prepare_key(self, key):
                isinstance(key, RSAPublicKey):
                 return key
 
-            if is_string_type(key):
-                if not isinstance(key, binary_type):
-                    key = key.encode('utf-8')
+            if isinstance(key, string_types):
+                key = force_bytes(key)
 
                 try:
                     if key.startswith(b'ssh-rsa'):
@@ -172,6 +204,105 @@ 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'],
+                    'n': force_unicode(to_base64url_uint(numbers.public_numbers.n)),
+                    'e': force_unicode(to_base64url_uint(numbers.public_numbers.e)),
+                    'd': force_unicode(to_base64url_uint(numbers.d)),
+                    'p': force_unicode(to_base64url_uint(numbers.p)),
+                    'q': force_unicode(to_base64url_uint(numbers.q)),
+                    'dp': force_unicode(to_base64url_uint(numbers.dmp1)),
+                    'dq': force_unicode(to_base64url_uint(numbers.dmq1)),
+                    'qi': force_unicode(to_base64url_uint(numbers.iqmp))
+                }
+
+            elif getattr(key_obj, 'verifier', None):
+                # Public key
+                numbers = key_obj.public_numbers()
+
+                obj = {
+                    'kty': 'RSA',
+                    'key_ops': ['verify'],
+                    'n': force_unicode(to_base64url_uint(numbers.n)),
+                    'e': force_unicode(to_base64url_uint(numbers.e))
+                }
+            else:
+                raise InvalidKeyError('Not a public or private key')
+
+            return json.dumps(obj)
+
+        @staticmethod
+        def from_jwk(jwk):
+            try:
+                obj = json.loads(jwk)
+            except ValueError:
+                raise InvalidKeyError('Key is not valid JSON')
+
+            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 = [prop in obj for prop in other_props]
+                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:
+                    d = from_base64url_uint(obj['d'])
+                    p, q = rsa_recover_prime_factors(
+                        public_numbers.n, d, public_numbers.e
+                    )
+
+                    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(),
@@ -213,9 +344,8 @@ def prepare_key(self, key):
                isinstance(key, EllipticCurvePublicKey):
                 return key
 
-            if is_string_type(key):
-                if not isinstance(key, binary_type):
-                    key = key.encode('utf-8')
+            if isinstance(key, string_types):
+                key = force_bytes(key)
 
                 # Attempt to load key. We don't know if it's
                 # a Signing Key or a Verifying Key, so we try

jwt/api_jws.py

@@ -7,7 +7,7 @@
 from .algorithms import Algorithm, get_default_algorithms  # NOQA
 from .compat import binary_type, string_types, text_type
 from .exceptions import DecodeError, InvalidAlgorithmError, InvalidTokenError
-from .utils import base64url_decode, base64url_encode, merge_dict
+from .utils import base64url_decode, base64url_encode, force_bytes, merge_dict
 
 
 class PyJWS(object):
@@ -82,11 +82,13 @@ def encode(self, payload, key, algorithm='HS256', headers=None,
             self._validate_headers(headers)
             header.update(headers)
 
-        json_header = json.dumps(
-            header,
-            separators=(',', ':'),
-            cls=json_encoder
-        ).encode('utf-8')
+        json_header = force_bytes(
+            json.dumps(
+                header,
+                separators=(',', ':'),
+                cls=json_encoder
+            )
+        )
 
         segments.append(base64url_encode(json_header))
         segments.append(base64url_encode(payload))

jwt/compat.py

@@ -3,8 +3,9 @@
 versions of python, and compatibility wrappers around optional packages.
 """
 # flake8: noqa
-import sys
 import hmac
+import struct
+import sys
 
 
 PY3 = sys.version_info[0] == 3
@@ -20,10 +21,6 @@
 string_types = (text_type, binary_type)
 
 
-def is_string_type(val):
-    return any([isinstance(val, typ) for typ in string_types])
-
-
 def timedelta_total_seconds(delta):
     try:
         delta.total_seconds
@@ -56,3 +53,24 @@ def constant_time_compare(val1, val2):
             result |= ord(x) ^ ord(y)
 
         return result == 0
+
+# Use int.to_bytes if it exists (Python 3)
+if getattr(int, 'to_bytes', None):
+    def bytes_from_int(val):
+        remaining = val
+        byte_length = 0
+
+        while remaining != 0:
+            remaining = remaining >> 8
+            byte_length += 1
+
+        return val.to_bytes(byte_length, 'big', signed=False)
+else:
+    def bytes_from_int(val):
+        buf = []
+        while val:
+            val, remainder = divmod(val, 256)
+            buf.append(remainder)
+
+        buf.reverse()
+        return struct.pack('%sB' % len(buf), *buf)

jwt/utils.py

@@ -1,5 +1,8 @@
 import base64
 import binascii
+import struct
+
+from .compat import binary_type, bytes_from_int, text_type
 
 try:
     from cryptography.hazmat.primitives.asymmetric.utils import (
@@ -9,7 +12,28 @@
     pass
 
 
+def force_unicode(value):
+    if isinstance(value, binary_type):
+        return value.decode('utf-8')
+    elif isinstance(value, text_type):
+        return value
+    else:
+        raise TypeError('Expected a string value')
+
+
+def force_bytes(value):
+    if isinstance(value, text_type):
+        return value.encode('utf-8')
+    elif isinstance(value, binary_type):
+        return value
+    else:
+        raise TypeError('Expected a string value')
+
+
 def base64url_decode(input):
+    if isinstance(input, text_type):
+        input = input.encode('ascii')
+
     rem = len(input) % 4
 
     if rem > 0:
@@ -22,6 +46,28 @@ 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')
+
+    int_bytes = bytes_from_int(val)
+
+    if len(int_bytes) == 0:
+        int_bytes = b'\x00'
+
+    return base64url_encode(int_bytes)
+
+
+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