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"""JSON Web Key."""
import abc
import json
import logging
import math
from typing import (
Any,
Callable,
Dict,
Mapping,
Optional,
Sequence,
Tuple,
Type,
Union,
)
import cryptography.exceptions
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives import hashes, serialization
from cryptography.hazmat.primitives.asymmetric import ec, rsa
import josepy.util
from josepy import errors, json_util, util
logger = logging.getLogger(__name__)
class JWK(json_util.TypedJSONObjectWithFields, metaclass=abc.ABCMeta):
"""JSON Web Key."""
type_field_name = "kty"
TYPES: Dict[str, Type["JWK"]] = {}
cryptography_key_types: Tuple[Type[Any], ...] = ()
"""Subclasses should override."""
required: Sequence[str] = NotImplemented
"""Required members of public key's representation as defined by JWK/JWA."""
_thumbprint_json_dumps_params: Dict[str, Union[Optional[int], Sequence[str], bool]] = {
# "no whitespace or line breaks before or after any syntactic
# elements"
"indent": None,
"separators": (",", ":"),
# "members ordered lexicographically by the Unicode [UNICODE]
# code points of the member names"
"sort_keys": True,
}
key: Any
def thumbprint(
self, hash_function: Callable[[], hashes.HashAlgorithm] = hashes.SHA256
) -> bytes:
"""Compute JWK Thumbprint.
https://tools.ietf.org/html/rfc7638
:returns: bytes
"""
digest = hashes.Hash(hash_function(), backend=default_backend())
digest.update(
json.dumps(
{k: v for k, v in self.to_json().items() if k in self.required},
**self._thumbprint_json_dumps_params, # type: ignore[arg-type]
).encode()
)
return digest.finalize()
@abc.abstractmethod
def public_key(self) -> "JWK": # pragma: no cover
"""Generate JWK with public key.
For symmetric cryptosystems, this would return ``self``.
"""
raise NotImplementedError()
@classmethod
def _load_cryptography_key(
cls, data: bytes, password: Optional[bytes] = None, backend: Optional[Any] = None
) -> Any:
backend = default_backend() if backend is None else backend
exceptions = {}
# private key?
loader_private: Any
for loader_private in (
serialization.load_pem_private_key,
serialization.load_der_private_key,
):
try:
return loader_private(data, password, backend)
except (ValueError, TypeError, cryptography.exceptions.UnsupportedAlgorithm) as error:
exceptions[str(loader_private)] = error
# public key?
loader_public: Any
for loader_public in (serialization.load_pem_public_key, serialization.load_der_public_key):
try:
return loader_public(data, backend)
except (ValueError, cryptography.exceptions.UnsupportedAlgorithm) as error:
exceptions[str(loader_public)] = error
# no luck
raise errors.Error("Unable to deserialize key: {0}".format(exceptions))
@classmethod
def load(
cls, data: bytes, password: Optional[bytes] = None, backend: Optional[Any] = None
) -> "JWK":
"""Load serialized key as JWK.
:param str data: Public or private key serialized as PEM or DER.
:param str password: Optional password.
:param backend: A `.PEMSerializationBackend` and
`.DERSerializationBackend` provider.
:raises errors.Error: if unable to deserialize, or unsupported
JWK algorithm
:returns: JWK of an appropriate type.
:rtype: `JWK`
"""
try:
key = cls._load_cryptography_key(data, password, backend)
except errors.Error as error:
logger.debug("Loading symmetric key, asymmetric failed: %s", error)
return JWKOct(key=data)
if cls.typ is not NotImplemented and not isinstance(key, cls.cryptography_key_types):
raise errors.Error(
"Unable to deserialize {0} into {1}".format(key.__class__, cls.__class__)
)
for jwk_cls in cls.TYPES.values():
if isinstance(key, jwk_cls.cryptography_key_types):
return jwk_cls(key=key)
raise errors.Error("Unsupported algorithm: {0}".format(key.__class__))
@JWK.register
class JWKOct(JWK):
"""Symmetric JWK."""
typ = "oct"
__slots__ = ("key",)
required = ("k", JWK.type_field_name)
key: bytes
def fields_to_partial_json(self) -> Dict[str, str]:
# TODO: An "alg" member SHOULD also be present to identify the
# algorithm intended to be used with the key, unless the
# application uses another means or convention to determine
# the algorithm used.
return {"k": json_util.encode_b64jose(self.key)}
@classmethod
def fields_from_json(cls, jobj: Mapping[str, Any]) -> "JWKOct":
return cls(key=json_util.decode_b64jose(jobj["k"]))
def public_key(self) -> "JWKOct":
return self
@JWK.register
class JWKRSA(JWK):
"""RSA JWK.
:ivar key: :class:`~cryptography.hazmat.primitives.asymmetric.rsa.RSAPrivateKey`
or :class:`~cryptography.hazmat.primitives.asymmetric.rsa.RSAPublicKey` wrapped
in :class:`~josepy.util.ComparableRSAKey`
"""
typ = "RSA"
cryptography_key_types = (rsa.RSAPublicKey, rsa.RSAPrivateKey)
__slots__ = ("key",)
required = ("e", JWK.type_field_name, "n")
key: josepy.util.ComparableRSAKey
def __init__(self, *args: Any, **kwargs: Any) -> None:
if "key" in kwargs and not isinstance(kwargs["key"], util.ComparableRSAKey):
kwargs["key"] = util.ComparableRSAKey(kwargs["key"])
super().__init__(*args, **kwargs)
@classmethod
def _encode_param(cls, data: int) -> str:
"""Encode Base64urlUInt.
:type data: long
:rtype: unicode
"""
length = max(data.bit_length(), 8) # decoding 0
length = math.ceil(length / 8)
return json_util.encode_b64jose(data.to_bytes(byteorder="big", length=length))
@classmethod
def _decode_param(cls, data: str) -> int:
"""Decode Base64urlUInt."""
try:
binary = json_util.decode_b64jose(data)
if not binary:
raise errors.DeserializationError()
return int.from_bytes(binary, byteorder="big")
except ValueError: # invalid literal for long() with base 16
raise errors.DeserializationError()
def public_key(self) -> "JWKRSA":
return type(self)(key=self.key.public_key())
@classmethod
def fields_from_json(cls, jobj: Mapping[str, Any]) -> "JWKRSA":
n, e = (cls._decode_param(jobj[x]) for x in ("n", "e"))
public_numbers = rsa.RSAPublicNumbers(e=e, n=n)
# public key
if "d" not in jobj:
return cls(key=public_numbers.public_key(default_backend()))
# private key
d = cls._decode_param(jobj["d"])
if (
"p" in jobj
or "q" in jobj
or "dp" in jobj
or "dq" in jobj
or "qi" in jobj
or "oth" in jobj
):
# "If the producer includes any of the other private
# key parameters, then all of the others MUST be
# present, with the exception of "oth", which MUST
# only be present when more than two prime factors
# were used."
(
p,
q,
dp,
dq,
qi,
) = all_params = tuple(jobj.get(x) for x in ("p", "q", "dp", "dq", "qi"))
if tuple(param for param in all_params if param is None):
raise errors.Error("Some private parameters are missing: {0}".format(all_params))
p, q, dp, dq, qi = tuple(cls._decode_param(str(x)) for x in all_params)
# TODO: check for oth
else:
# cryptography>=0.8
p, q = rsa.rsa_recover_prime_factors(n, e, d)
dp = rsa.rsa_crt_dmp1(d, p)
dq = rsa.rsa_crt_dmq1(d, q)
qi = rsa.rsa_crt_iqmp(p, q)
key = rsa.RSAPrivateNumbers(p, q, d, dp, dq, qi, public_numbers).private_key(
default_backend()
)
return cls(key=key)
def fields_to_partial_json(self) -> Dict[str, Any]:
if isinstance(self.key._wrapped, rsa.RSAPublicKey):
numbers = self.key.public_numbers()
params = {
"n": numbers.n,
"e": numbers.e,
}
else: # rsa.RSAPrivateKey
private = self.key.private_numbers()
public = self.key.public_key().public_numbers()
params = {
"n": public.n,
"e": public.e,
"d": private.d,
"p": private.p,
"q": private.q,
"dp": private.dmp1,
"dq": private.dmq1,
"qi": private.iqmp,
}
return {key: self._encode_param(value) for key, value in params.items()}
@JWK.register
class JWKEC(JWK):
"""EC JWK.
:ivar key: :class:`~cryptography.hazmat.primitives.asymmetric.ec.EllipticCurvePrivateKey`
or :class:`~cryptography.hazmat.primitives.asymmetric.ec.EllipticCurvePublicKey` wrapped
in :class:`~josepy.util.ComparableECKey`
"""
typ = "EC"
__slots__ = ("key",)
cryptography_key_types = (ec.EllipticCurvePublicKey, ec.EllipticCurvePrivateKey)
required = ("crv", JWK.type_field_name, "x", "y")
key: josepy.util.ComparableECKey
def __init__(self, *args: Any, **kwargs: Any) -> None:
if "key" in kwargs and not isinstance(kwargs["key"], util.ComparableECKey):
kwargs["key"] = util.ComparableECKey(kwargs["key"])
super().__init__(*args, **kwargs)
@classmethod
def _encode_param(cls, data: int, length: int) -> str:
"""Encode Base64urlUInt.
:type data: long
:type key_size: long
:rtype: unicode
"""
return json_util.encode_b64jose(data.to_bytes(byteorder="big", length=length))
@classmethod
def _decode_param(cls, data: str, name: str, valid_length: int) -> int:
"""Decode Base64urlUInt."""
try:
binary = json_util.decode_b64jose(data)
if len(binary) != valid_length:
raise errors.DeserializationError(
f'Expected parameter "{name}" to be {valid_length} bytes '
f"after base64-decoding; got {len(binary)} bytes instead"
)
return int.from_bytes(binary, byteorder="big")
except ValueError: # invalid literal for long() with base 16
raise errors.DeserializationError()
@classmethod
def _curve_name_to_crv(cls, curve_name: str) -> str:
if curve_name == "secp256r1":
return "P-256"
if curve_name == "secp384r1":
return "P-384"
if curve_name == "secp521r1":
return "P-521"
raise errors.SerializationError()
@classmethod
def _crv_to_curve(cls, crv: str) -> ec.EllipticCurve:
# crv is case-sensitive
if crv == "P-256":
return ec.SECP256R1()
if crv == "P-384":
return ec.SECP384R1()
if crv == "P-521":
return ec.SECP521R1()
raise errors.DeserializationError()
@classmethod
def expected_length_for_curve(cls, curve: ec.EllipticCurve) -> int:
if isinstance(curve, ec.SECP256R1):
return 32
elif isinstance(curve, ec.SECP384R1):
return 48
elif isinstance(curve, ec.SECP521R1):
return 66
raise ValueError(f"Unexpected curve: {curve}")
def fields_to_partial_json(self) -> Dict[str, Any]:
params = {}
if isinstance(self.key._wrapped, ec.EllipticCurvePublicKey):
public = self.key.public_numbers()
elif isinstance(self.key._wrapped, ec.EllipticCurvePrivateKey):
private = self.key.private_numbers()
public = self.key.public_key().public_numbers()
params["d"] = private.private_value
else:
raise errors.SerializationError(
"Supplied key is neither of type EllipticCurvePublicKey "
"nor EllipticCurvePrivateKey"
)
params["x"] = public.x
params["y"] = public.y
params = {
key: self._encode_param(value, self.expected_length_for_curve(public.curve))
for key, value in params.items()
}
params["crv"] = self._curve_name_to_crv(public.curve.name)
return params
@classmethod
def fields_from_json(cls, jobj: Mapping[str, Any]) -> "JWKEC":
curve = cls._crv_to_curve(jobj["crv"])
expected_length = cls.expected_length_for_curve(curve)
x, y = (cls._decode_param(jobj[n], n, expected_length) for n in ("x", "y"))
public_numbers = ec.EllipticCurvePublicNumbers(x=x, y=y, curve=curve)
# private key
if "d" not in jobj:
return cls(key=public_numbers.public_key(default_backend()))
# private key
d = cls._decode_param(jobj["d"], "d", expected_length)
key = ec.EllipticCurvePrivateNumbers(d, public_numbers).private_key(default_backend())
return cls(key=key)
def public_key(self) -> "JWKEC":
# Unlike RSAPrivateKey, EllipticCurvePrivateKey does not contain public_key()
if hasattr(self.key, "public_key"):
key = self.key.public_key()
else:
key = self.key.public_numbers().public_key(default_backend())
return type(self)(key=key)
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