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77 lines
2.2 KiB
77 lines
2.2 KiB
3 years ago
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import hashlib
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import hmac
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import os
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from jose.backends.base import Key
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from jose.constants import ALGORITHMS
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from jose.exceptions import JWKError
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from jose.utils import base64url_decode, base64url_encode
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def get_random_bytes(num_bytes):
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return bytes(os.urandom(num_bytes))
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class HMACKey(Key):
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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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HASHES = {ALGORITHMS.HS256: hashlib.sha256, ALGORITHMS.HS384: hashlib.sha384, ALGORITHMS.HS512: hashlib.sha512}
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def __init__(self, key, algorithm):
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if algorithm not in ALGORITHMS.HMAC:
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raise JWKError("hash_alg: %s is not a valid hash algorithm" % algorithm)
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self._algorithm = algorithm
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self._hash_alg = self.HASHES.get(algorithm)
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if isinstance(key, dict):
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self.prepared_key = self._process_jwk(key)
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return
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if not isinstance(key, str) and not isinstance(key, bytes):
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raise JWKError("Expecting a string- or bytes-formatted key.")
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if isinstance(key, str):
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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 RSA 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 JWKError(
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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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)
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self.prepared_key = key
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def _process_jwk(self, jwk_dict):
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if not jwk_dict.get("kty") == "oct":
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raise JWKError("Incorrect key type. Expected: 'oct', Received: %s" % jwk_dict.get("kty"))
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k = jwk_dict.get("k")
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k = k.encode("utf-8")
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k = bytes(k)
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k = base64url_decode(k)
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return k
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def sign(self, msg):
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return hmac.new(self.prepared_key, msg, self._hash_alg).digest()
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def verify(self, msg, sig):
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return hmac.compare_digest(sig, self.sign(msg))
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def to_dict(self):
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return {
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"alg": self._algorithm,
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"kty": "oct",
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"k": base64url_encode(self.prepared_key).decode("ASCII"),
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}
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