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import hashlib
import hmac
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
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
)
from cryptography.hazmat.primitives.asymmetric.ec import (
EllipticCurvePrivateKey, EllipticCurvePublicKey
)
from cryptography.hazmat.primitives.asymmetric import ec, padding
from cryptography.hazmat.backends import default_backend
from cryptography.exceptions import InvalidSignature
has_crypto = True
except ImportError:
has_crypto = False
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),
'ES384': ECAlgorithm(ECAlgorithm.SHA384),
'ES512': ECAlgorithm(ECAlgorithm.SHA512),
'PS256': RSAPSSAlgorithm(RSAPSSAlgorithm.SHA256),
'PS384': RSAPSSAlgorithm(RSAPSSAlgorithm.SHA384),
'PS512': RSAPSSAlgorithm(RSAPSSAlgorithm.SHA512)
})
return default_algorithms
class Algorithm(object):
"""
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
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):
if not isinstance(key, string_types) and not isinstance(key, bytes):
raise TypeError('Expecting a string- or bytes-formatted key.')
if isinstance(key, text_type):
key = key.encode('utf-8')
invalid_strings = [
b'-----BEGIN PUBLIC KEY-----',
b'-----BEGIN CERTIFICATE-----',
b'ssh-rsa'
]
if any([string_value in key for string_value in invalid_strings]):
raise InvalidKeyError(
'The specified key is an asymmetric key or x509 certificate and'
' should not be used as an HMAC secret.')
return key
def sign(self, msg, key):
return hmac.new(key, msg, self.hash_alg).digest()
def verify(self, msg, key, sig):
return constant_time_compare(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) or \
isinstance(key, RSAPublicKey):
return key
if isinstance(key, string_types):
if isinstance(key, text_type):
key = key.encode('utf-8')
try:
if key.startswith(b'ssh-rsa'):
key = load_ssh_public_key(key, backend=default_backend())
else:
key = load_pem_private_key(key, password=None, backend=default_backend())
except ValueError:
key = load_pem_public_key(key, backend=default_backend())
else:
raise TypeError('Expecting a PEM-formatted key.')
return key
def sign(self, msg, key):
signer = key.signer(
padding.PKCS1v15(),
self.hash_alg()
)
signer.update(msg)
return signer.finalize()
def verify(self, msg, key, sig):
verifier = key.verifier(
sig,
padding.PKCS1v15(),
self.hash_alg()
)
verifier.update(msg)
try:
verifier.verify()
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) or \
isinstance(key, EllipticCurvePublicKey):
return key
if isinstance(key, string_types):
if isinstance(key, text_type):
key = key.encode('utf-8')
# 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:
key = load_pem_public_key(key, backend=default_backend())
except ValueError:
key = load_pem_private_key(key, password=None, backend=default_backend())
else:
raise TypeError('Expecting a PEM-formatted key.')
return key
def sign(self, msg, key):
signer = key.signer(ec.ECDSA(self.hash_alg()))
signer.update(msg)
der_sig = signer.finalize()
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
verifier = key.verifier(der_sig, ec.ECDSA(self.hash_alg()))
verifier.update(msg)
try:
verifier.verify()
return True
except InvalidSignature:
return False
class RSAPSSAlgorithm(RSAAlgorithm):
"""
Performs a signature using RSASSA-PSS with MGF1
"""
def sign(self, msg, key):
signer = key.signer(
padding.PSS(
mgf=padding.MGF1(self.hash_alg()),
salt_length=self.hash_alg.digest_size
),
self.hash_alg()
)
signer.update(msg)
return signer.finalize()
def verify(self, msg, key, sig):
verifier = key.verifier(
sig,
padding.PSS(
mgf=padding.MGF1(self.hash_alg()),
salt_length=self.hash_alg.digest_size
),
self.hash_alg()
)
verifier.update(msg)
try:
verifier.verify()
return True
except InvalidSignature:
return False
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