291 lines
8.5 KiB
Python
291 lines
8.5 KiB
Python
import hashlib
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import hmac
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from .compat import binary_type, constant_time_compare, is_string_type
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from .exceptions import InvalidKeyError
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from .utils import der_to_raw_signature, raw_to_der_signature
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try:
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from cryptography.hazmat.primitives import hashes
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from cryptography.hazmat.primitives.serialization import (
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load_pem_private_key, load_pem_public_key, load_ssh_public_key
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)
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from cryptography.hazmat.primitives.asymmetric.rsa import (
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RSAPrivateKey, RSAPublicKey
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)
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from cryptography.hazmat.primitives.asymmetric.ec import (
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EllipticCurvePrivateKey, EllipticCurvePublicKey
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)
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from cryptography.hazmat.primitives.asymmetric import ec, padding
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from cryptography.hazmat.backends import default_backend
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from cryptography.exceptions import InvalidSignature
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has_crypto = True
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except ImportError:
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has_crypto = False
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def get_default_algorithms():
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"""
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Returns the algorithms that are implemented by the library.
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"""
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default_algorithms = {
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'none': NoneAlgorithm(),
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'HS256': HMACAlgorithm(HMACAlgorithm.SHA256),
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'HS384': HMACAlgorithm(HMACAlgorithm.SHA384),
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'HS512': HMACAlgorithm(HMACAlgorithm.SHA512)
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}
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if has_crypto:
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default_algorithms.update({
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'RS256': RSAAlgorithm(RSAAlgorithm.SHA256),
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'RS384': RSAAlgorithm(RSAAlgorithm.SHA384),
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'RS512': RSAAlgorithm(RSAAlgorithm.SHA512),
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'ES256': ECAlgorithm(ECAlgorithm.SHA256),
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'ES384': ECAlgorithm(ECAlgorithm.SHA384),
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'ES512': ECAlgorithm(ECAlgorithm.SHA512),
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'PS256': RSAPSSAlgorithm(RSAPSSAlgorithm.SHA256),
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'PS384': RSAPSSAlgorithm(RSAPSSAlgorithm.SHA384),
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'PS512': RSAPSSAlgorithm(RSAPSSAlgorithm.SHA512)
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})
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return default_algorithms
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class Algorithm(object):
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"""
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The interface for an algorithm used to sign and verify tokens.
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"""
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def prepare_key(self, key):
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"""
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Performs necessary validation and conversions on the key and returns
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the key value in the proper format for sign() and verify().
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"""
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raise NotImplementedError
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def sign(self, msg, key):
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"""
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Returns a digital signature for the specified message
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using the specified key value.
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"""
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raise NotImplementedError
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def verify(self, msg, key, sig):
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"""
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Verifies that the specified digital signature is valid
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for the specified message and key values.
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"""
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raise NotImplementedError
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class NoneAlgorithm(Algorithm):
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"""
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Placeholder for use when no signing or verification
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operations are required.
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"""
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def prepare_key(self, key):
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if key == '':
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key = None
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if key is not None:
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raise InvalidKeyError('When alg = "none", key value must be None.')
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return key
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def sign(self, msg, key):
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return b''
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def verify(self, msg, key, sig):
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return False
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class HMACAlgorithm(Algorithm):
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"""
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Performs signing and verification operations using HMAC
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and the specified hash function.
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"""
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SHA256 = hashlib.sha256
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SHA384 = hashlib.sha384
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SHA512 = hashlib.sha512
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def __init__(self, hash_alg):
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self.hash_alg = hash_alg
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def prepare_key(self, key):
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if not is_string_type(key):
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raise TypeError('Expecting a string- or bytes-formatted key.')
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if not isinstance(key, binary_type):
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key = key.encode('utf-8')
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invalid_strings = [
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b'-----BEGIN PUBLIC KEY-----',
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b'-----BEGIN CERTIFICATE-----',
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b'ssh-rsa'
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]
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if any([string_value in key for string_value in invalid_strings]):
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raise InvalidKeyError(
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'The specified key is an asymmetric key or x509 certificate and'
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' should not be used as an HMAC secret.')
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return key
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def sign(self, msg, key):
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return hmac.new(key, msg, self.hash_alg).digest()
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def verify(self, msg, key, sig):
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return constant_time_compare(sig, self.sign(msg, key))
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if has_crypto:
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class RSAAlgorithm(Algorithm):
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"""
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Performs signing and verification operations using
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RSASSA-PKCS-v1_5 and the specified hash function.
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"""
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SHA256 = hashes.SHA256
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SHA384 = hashes.SHA384
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SHA512 = hashes.SHA512
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def __init__(self, hash_alg):
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self.hash_alg = hash_alg
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def prepare_key(self, key):
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if isinstance(key, RSAPrivateKey) or \
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isinstance(key, RSAPublicKey):
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return key
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if is_string_type(key):
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if not isinstance(key, binary_type):
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key = key.encode('utf-8')
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try:
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if key.startswith(b'ssh-rsa'):
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key = load_ssh_public_key(key, backend=default_backend())
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else:
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key = load_pem_private_key(key, password=None, backend=default_backend())
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except ValueError:
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key = load_pem_public_key(key, backend=default_backend())
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else:
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raise TypeError('Expecting a PEM-formatted key.')
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return key
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def sign(self, msg, key):
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signer = key.signer(
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padding.PKCS1v15(),
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self.hash_alg()
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)
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signer.update(msg)
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return signer.finalize()
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def verify(self, msg, key, sig):
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verifier = key.verifier(
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sig,
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padding.PKCS1v15(),
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self.hash_alg()
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)
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verifier.update(msg)
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try:
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verifier.verify()
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return True
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except InvalidSignature:
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return False
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class ECAlgorithm(Algorithm):
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"""
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Performs signing and verification operations using
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ECDSA and the specified hash function
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"""
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SHA256 = hashes.SHA256
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SHA384 = hashes.SHA384
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SHA512 = hashes.SHA512
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def __init__(self, hash_alg):
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self.hash_alg = hash_alg
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def prepare_key(self, key):
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if isinstance(key, EllipticCurvePrivateKey) or \
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isinstance(key, EllipticCurvePublicKey):
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return key
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if is_string_type(key):
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if not isinstance(key, binary_type):
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key = key.encode('utf-8')
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# Attempt to load key. We don't know if it's
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# a Signing Key or a Verifying Key, so we try
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# the Verifying Key first.
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try:
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key = load_pem_public_key(key, backend=default_backend())
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except ValueError:
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key = load_pem_private_key(key, password=None, backend=default_backend())
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else:
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raise TypeError('Expecting a PEM-formatted key.')
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return key
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def sign(self, msg, key):
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signer = key.signer(ec.ECDSA(self.hash_alg()))
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signer.update(msg)
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der_sig = signer.finalize()
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return der_to_raw_signature(der_sig, key.curve)
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def verify(self, msg, key, sig):
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try:
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der_sig = raw_to_der_signature(sig, key.curve)
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except ValueError:
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return False
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verifier = key.verifier(der_sig, ec.ECDSA(self.hash_alg()))
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verifier.update(msg)
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try:
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verifier.verify()
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return True
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except InvalidSignature:
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return False
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class RSAPSSAlgorithm(RSAAlgorithm):
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"""
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Performs a signature using RSASSA-PSS with MGF1
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"""
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def sign(self, msg, key):
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signer = key.signer(
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padding.PSS(
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mgf=padding.MGF1(self.hash_alg()),
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salt_length=self.hash_alg.digest_size
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),
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self.hash_alg()
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)
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signer.update(msg)
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return signer.finalize()
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def verify(self, msg, key, sig):
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verifier = key.verifier(
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sig,
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padding.PSS(
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mgf=padding.MGF1(self.hash_alg()),
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salt_length=self.hash_alg.digest_size
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),
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self.hash_alg()
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)
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verifier.update(msg)
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try:
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verifier.verify()
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return True
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except InvalidSignature:
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return False
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