CasperSecurity
import hashlib
import hmac
import json
from .exceptions import InvalidKeyError
from .utils import (
base64url_decode,
base64url_encode,
der_to_raw_signature,
force_bytes,
from_base64url_uint,
is_pem_format,
is_ssh_key,
raw_to_der_signature,
to_base64url_uint,
)
try:
import cryptography.exceptions
from cryptography.exceptions import InvalidSignature
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives.asymmetric import ec, padding
from cryptography.hazmat.primitives.asymmetric.ec import (
EllipticCurvePrivateKey,
EllipticCurvePublicKey,
)
from cryptography.hazmat.primitives.asymmetric.ed448 import (
Ed448PrivateKey,
Ed448PublicKey,
)
from cryptography.hazmat.primitives.asymmetric.ed25519 import (
Ed25519PrivateKey,
Ed25519PublicKey,
)
from cryptography.hazmat.primitives.asymmetric.rsa import (
RSAPrivateKey,
RSAPrivateNumbers,
RSAPublicKey,
RSAPublicNumbers,
rsa_crt_dmp1,
rsa_crt_dmq1,
rsa_crt_iqmp,
rsa_recover_prime_factors,
)
from cryptography.hazmat.primitives.serialization import (
Encoding,
NoEncryption,
PrivateFormat,
PublicFormat,
load_pem_private_key,
load_pem_public_key,
load_ssh_public_key,
)
has_crypto = True
except ModuleNotFoundError:
has_crypto = False
requires_cryptography = {
"RS256",
"RS384",
"RS512",
"ES256",
"ES256K",
"ES384",
"ES521",
"ES512",
"PS256",
"PS384",
"PS512",
"EdDSA",
}
def get_default_algorithms():
"""
Returns the algorithms that are implemented by the library.
"""
default_algorithms = {
"none": NoneAlgorithm(),
"HS256": HMACAlgorithm(HMACAlgorithm.SHA256),
"HS384": HMACAlgorithm(HMACAlgorithm.SHA384),
"HS512": HMACAlgorithm(HMACAlgorithm.SHA512),
}
if has_crypto:
default_algorithms.update(
{
"RS256": RSAAlgorithm(RSAAlgorithm.SHA256),
"RS384": RSAAlgorithm(RSAAlgorithm.SHA384),
"RS512": RSAAlgorithm(RSAAlgorithm.SHA512),
"ES256": ECAlgorithm(ECAlgorithm.SHA256),
"ES256K": ECAlgorithm(ECAlgorithm.SHA256),
"ES384": ECAlgorithm(ECAlgorithm.SHA384),
"ES521": ECAlgorithm(ECAlgorithm.SHA512),
"ES512": ECAlgorithm(
ECAlgorithm.SHA512
), # Backward compat for #219 fix
"PS256": RSAPSSAlgorithm(RSAPSSAlgorithm.SHA256),
"PS384": RSAPSSAlgorithm(RSAPSSAlgorithm.SHA384),
"PS512": RSAPSSAlgorithm(RSAPSSAlgorithm.SHA512),
"EdDSA": OKPAlgorithm(),
}
)
return default_algorithms
class Algorithm:
"""
The interface for an algorithm used to sign and verify tokens.
"""
def prepare_key(self, key):
"""
Performs necessary validation and conversions on the key and returns
the key value in the proper format for sign() and verify().
"""
raise NotImplementedError
def sign(self, msg, key):
"""
Returns a digital signature for the specified message
using the specified key value.
"""
raise NotImplementedError
def verify(self, msg, key, sig):
"""
Verifies that the specified digital signature is valid
for the specified message and key values.
"""
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):
"""
Placeholder for use when no signing or verification
operations are required.
"""
def prepare_key(self, key):
if key == "":
key = None
if key is not None:
raise InvalidKeyError('When alg = "none", key value must be None.')
return key
def sign(self, msg, key):
return b""
def verify(self, msg, key, sig):
return False
class HMACAlgorithm(Algorithm):
"""
Performs signing and verification operations using HMAC
and the specified hash function.
"""
SHA256 = hashlib.sha256
SHA384 = hashlib.sha384
SHA512 = hashlib.sha512
def __init__(self, hash_alg):
self.hash_alg = hash_alg
def prepare_key(self, key):
key = force_bytes(key)
if is_pem_format(key) or is_ssh_key(key):
raise InvalidKeyError(
"The specified key is an asymmetric key or x509 certificate and"
" should not be used as an HMAC secret."
)
return key
@staticmethod
def to_jwk(key_obj):
return json.dumps(
{
"k": base64url_encode(force_bytes(key_obj)).decode(),
"kty": "oct",
}
)
@staticmethod
def from_jwk(jwk):
try:
if isinstance(jwk, str):
obj = json.loads(jwk)
elif isinstance(jwk, dict):
obj = jwk
else:
raise ValueError
except ValueError:
raise InvalidKeyError("Key is not valid JSON")
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()
def verify(self, msg, key, sig):
return hmac.compare_digest(sig, self.sign(msg, key))
if has_crypto:
class RSAAlgorithm(Algorithm):
"""
Performs signing and verification operations using
RSASSA-PKCS-v1_5 and the specified hash function.
"""
SHA256 = hashes.SHA256
SHA384 = hashes.SHA384
SHA512 = hashes.SHA512
def __init__(self, hash_alg):
self.hash_alg = hash_alg
def prepare_key(self, key):
if isinstance(key, (RSAPrivateKey, RSAPublicKey)):
return key
if not isinstance(key, (bytes, str)):
raise TypeError("Expecting a PEM-formatted key.")
key = force_bytes(key)
try:
if key.startswith(b"ssh-rsa"):
key = load_ssh_public_key(key)
else:
key = load_pem_private_key(key, password=None)
except ValueError:
key = load_pem_public_key(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": to_base64url_uint(numbers.public_numbers.n).decode(),
"e": to_base64url_uint(numbers.public_numbers.e).decode(),
"d": to_base64url_uint(numbers.d).decode(),
"p": to_base64url_uint(numbers.p).decode(),
"q": to_base64url_uint(numbers.q).decode(),
"dp": to_base64url_uint(numbers.dmp1).decode(),
"dq": to_base64url_uint(numbers.dmq1).decode(),
"qi": to_base64url_uint(numbers.iqmp).decode(),
}
elif getattr(key_obj, "verify", None):
# Public key
numbers = key_obj.public_numbers()
obj = {
"kty": "RSA",
"key_ops": ["verify"],
"n": to_base64url_uint(numbers.n).decode(),
"e": to_base64url_uint(numbers.e).decode(),
}
else:
raise InvalidKeyError("Not a public or private key")
return json.dumps(obj)
@staticmethod
def from_jwk(jwk):
try:
if isinstance(jwk, str):
obj = json.loads(jwk)
elif isinstance(jwk, dict):
obj = jwk
else:
raise ValueError
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()
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()
else:
raise InvalidKeyError("Not a public or private key")
def sign(self, msg, key):
return key.sign(msg, padding.PKCS1v15(), self.hash_alg())
def verify(self, msg, key, sig):
try:
key.verify(sig, msg, padding.PKCS1v15(), self.hash_alg())
return True
except InvalidSignature:
return False
class ECAlgorithm(Algorithm):
"""
Performs signing and verification operations using
ECDSA and the specified hash function
"""
SHA256 = hashes.SHA256
SHA384 = hashes.SHA384
SHA512 = hashes.SHA512
def __init__(self, hash_alg):
self.hash_alg = hash_alg
def prepare_key(self, key):
if isinstance(key, (EllipticCurvePrivateKey, EllipticCurvePublicKey)):
return key
if not isinstance(key, (bytes, str)):
raise TypeError("Expecting a PEM-formatted key.")
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
# the Verifying Key first.
try:
if key.startswith(b"ecdsa-sha2-"):
key = load_ssh_public_key(key)
else:
key = load_pem_public_key(key)
except ValueError:
key = load_pem_private_key(key, password=None)
return key
def sign(self, msg, key):
der_sig = key.sign(msg, ec.ECDSA(self.hash_alg()))
return der_to_raw_signature(der_sig, key.curve)
def verify(self, msg, key, sig):
try:
der_sig = raw_to_der_signature(sig, key.curve)
except ValueError:
return False
try:
if isinstance(key, EllipticCurvePrivateKey):
key = key.public_key()
key.verify(der_sig, msg, ec.ECDSA(self.hash_alg()))
return True
except InvalidSignature:
return False
@staticmethod
def from_jwk(jwk):
try:
if isinstance(jwk, str):
obj = json.loads(jwk)
elif isinstance(jwk, dict):
obj = jwk
else:
raise ValueError
except ValueError:
raise InvalidKeyError("Key is not valid JSON")
if obj.get("kty") != "EC":
raise InvalidKeyError("Not an Elliptic curve key")
if "x" not in obj or "y" not in obj:
raise InvalidKeyError("Not an Elliptic curve key")
x = base64url_decode(obj.get("x"))
y = base64url_decode(obj.get("y"))
curve = obj.get("crv")
if curve == "P-256":
if len(x) == len(y) == 32:
curve_obj = ec.SECP256R1()
else:
raise InvalidKeyError("Coords should be 32 bytes for curve P-256")
elif curve == "P-384":
if len(x) == len(y) == 48:
curve_obj = ec.SECP384R1()
else:
raise InvalidKeyError("Coords should be 48 bytes for curve P-384")
elif curve == "P-521":
if len(x) == len(y) == 66:
curve_obj = ec.SECP521R1()
else:
raise InvalidKeyError("Coords should be 66 bytes for curve P-521")
elif curve == "secp256k1":
if len(x) == len(y) == 32:
curve_obj = ec.SECP256K1()
else:
raise InvalidKeyError(
"Coords should be 32 bytes for curve secp256k1"
)
else:
raise InvalidKeyError(f"Invalid curve: {curve}")
public_numbers = ec.EllipticCurvePublicNumbers(
x=int.from_bytes(x, byteorder="big"),
y=int.from_bytes(y, byteorder="big"),
curve=curve_obj,
)
if "d" not in obj:
return public_numbers.public_key()
d = base64url_decode(obj.get("d"))
if len(d) != len(x):
raise InvalidKeyError(
"D should be {} bytes for curve {}", len(x), curve
)
return ec.EllipticCurvePrivateNumbers(
int.from_bytes(d, byteorder="big"), public_numbers
).private_key()
class RSAPSSAlgorithm(RSAAlgorithm):
"""
Performs a signature using RSASSA-PSS with MGF1
"""
def sign(self, msg, key):
return key.sign(
msg,
padding.PSS(
mgf=padding.MGF1(self.hash_alg()),
salt_length=self.hash_alg.digest_size,
),
self.hash_alg(),
)
def verify(self, msg, key, sig):
try:
key.verify(
sig,
msg,
padding.PSS(
mgf=padding.MGF1(self.hash_alg()),
salt_length=self.hash_alg.digest_size,
),
self.hash_alg(),
)
return True
except InvalidSignature:
return False
class OKPAlgorithm(Algorithm):
"""
Performs signing and verification operations using EdDSA
This class requires ``cryptography>=2.6`` to be installed.
"""
def __init__(self, **kwargs):
pass
def prepare_key(self, key):
if isinstance(key, (bytes, str)):
if isinstance(key, str):
key = key.encode("utf-8")
str_key = key.decode("utf-8")
if "-----BEGIN PUBLIC" in str_key:
key = load_pem_public_key(key)
elif "-----BEGIN PRIVATE" in str_key:
key = load_pem_private_key(key, password=None)
elif str_key[0:4] == "ssh-":
key = load_ssh_public_key(key)
# Explicit check the key to prevent confusing errors from cryptography
if not isinstance(
key,
(Ed25519PrivateKey, Ed25519PublicKey, Ed448PrivateKey, Ed448PublicKey),
):
raise InvalidKeyError(
"Expecting a EllipticCurvePrivateKey/EllipticCurvePublicKey. Wrong key provided for EdDSA algorithms"
)
return key
def sign(self, msg, key):
"""
Sign a message ``msg`` using the EdDSA private key ``key``
:param str|bytes msg: Message to sign
:param Ed25519PrivateKey}Ed448PrivateKey key: A :class:`.Ed25519PrivateKey`
or :class:`.Ed448PrivateKey` iinstance
:return bytes signature: The signature, as bytes
"""
msg = bytes(msg, "utf-8") if type(msg) is not bytes else msg
return key.sign(msg)
def verify(self, msg, key, sig):
"""
Verify a given ``msg`` against a signature ``sig`` using the EdDSA key ``key``
:param str|bytes sig: EdDSA signature to check ``msg`` against
:param str|bytes msg: Message to sign
:param Ed25519PrivateKey|Ed25519PublicKey|Ed448PrivateKey|Ed448PublicKey key:
A private or public EdDSA key instance
:return bool verified: True if signature is valid, False if not.
"""
try:
msg = bytes(msg, "utf-8") if type(msg) is not bytes else msg
sig = bytes(sig, "utf-8") if type(sig) is not bytes else sig
if isinstance(key, (Ed25519PrivateKey, Ed448PrivateKey)):
key = key.public_key()
key.verify(sig, msg)
return True # If no exception was raised, the signature is valid.
except cryptography.exceptions.InvalidSignature:
return False
@staticmethod
def to_jwk(key):
if isinstance(key, (Ed25519PublicKey, Ed448PublicKey)):
x = key.public_bytes(
encoding=Encoding.Raw,
format=PublicFormat.Raw,
)
crv = "Ed25519" if isinstance(key, Ed25519PublicKey) else "Ed448"
return json.dumps(
{
"x": base64url_encode(force_bytes(x)).decode(),
"kty": "OKP",
"crv": crv,
}
)
if isinstance(key, (Ed25519PrivateKey, Ed448PrivateKey)):
d = key.private_bytes(
encoding=Encoding.Raw,
format=PrivateFormat.Raw,
encryption_algorithm=NoEncryption(),
)
x = key.public_key().public_bytes(
encoding=Encoding.Raw,
format=PublicFormat.Raw,
)
crv = "Ed25519" if isinstance(key, Ed25519PrivateKey) else "Ed448"
return json.dumps(
{
"x": base64url_encode(force_bytes(x)).decode(),
"d": base64url_encode(force_bytes(d)).decode(),
"kty": "OKP",
"crv": crv,
}
)
raise InvalidKeyError("Not a public or private key")
@staticmethod
def from_jwk(jwk):
try:
if isinstance(jwk, str):
obj = json.loads(jwk)
elif isinstance(jwk, dict):
obj = jwk
else:
raise ValueError
except ValueError:
raise InvalidKeyError("Key is not valid JSON")
if obj.get("kty") != "OKP":
raise InvalidKeyError("Not an Octet Key Pair")
curve = obj.get("crv")
if curve != "Ed25519" and curve != "Ed448":
raise InvalidKeyError(f"Invalid curve: {curve}")
if "x" not in obj:
raise InvalidKeyError('OKP should have "x" parameter')
x = base64url_decode(obj.get("x"))
try:
if "d" not in obj:
if curve == "Ed25519":
return Ed25519PublicKey.from_public_bytes(x)
return Ed448PublicKey.from_public_bytes(x)
d = base64url_decode(obj.get("d"))
if curve == "Ed25519":
return Ed25519PrivateKey.from_private_bytes(d)
return Ed448PrivateKey.from_private_bytes(d)
except ValueError as err:
raise InvalidKeyError("Invalid key parameter") from err