219 lines
7.3 KiB
Python
219 lines
7.3 KiB
Python
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import hashlib
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import time
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from datetime import datetime
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from ._compat import number_types
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from ._json import _CompactJSON
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from ._json import json
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from .encoding import base64_decode
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from .encoding import base64_encode
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from .encoding import want_bytes
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from .exc import BadData
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from .exc import BadHeader
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from .exc import BadPayload
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from .exc import BadSignature
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from .exc import SignatureExpired
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from .serializer import Serializer
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from .signer import HMACAlgorithm
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from .signer import NoneAlgorithm
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class JSONWebSignatureSerializer(Serializer):
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"""This serializer implements JSON Web Signature (JWS) support. Only
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supports the JWS Compact Serialization.
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"""
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jws_algorithms = {
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"HS256": HMACAlgorithm(hashlib.sha256),
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"HS384": HMACAlgorithm(hashlib.sha384),
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"HS512": HMACAlgorithm(hashlib.sha512),
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"none": NoneAlgorithm(),
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}
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#: The default algorithm to use for signature generation
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default_algorithm = "HS512"
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default_serializer = _CompactJSON
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def __init__(
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self,
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secret_key,
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salt=None,
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serializer=None,
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serializer_kwargs=None,
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signer=None,
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signer_kwargs=None,
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algorithm_name=None,
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):
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Serializer.__init__(
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self,
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secret_key=secret_key,
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salt=salt,
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serializer=serializer,
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serializer_kwargs=serializer_kwargs,
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signer=signer,
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signer_kwargs=signer_kwargs,
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)
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if algorithm_name is None:
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algorithm_name = self.default_algorithm
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self.algorithm_name = algorithm_name
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self.algorithm = self.make_algorithm(algorithm_name)
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def load_payload(self, payload, serializer=None, return_header=False):
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payload = want_bytes(payload)
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if b"." not in payload:
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raise BadPayload('No "." found in value')
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base64d_header, base64d_payload = payload.split(b".", 1)
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try:
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json_header = base64_decode(base64d_header)
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except Exception as e:
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raise BadHeader(
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"Could not base64 decode the header because of an exception",
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original_error=e,
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)
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try:
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json_payload = base64_decode(base64d_payload)
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except Exception as e:
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raise BadPayload(
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"Could not base64 decode the payload because of an exception",
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original_error=e,
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)
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try:
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header = Serializer.load_payload(self, json_header, serializer=json)
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except BadData as e:
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raise BadHeader(
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"Could not unserialize header because it was malformed",
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original_error=e,
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)
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if not isinstance(header, dict):
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raise BadHeader("Header payload is not a JSON object", header=header)
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payload = Serializer.load_payload(self, json_payload, serializer=serializer)
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if return_header:
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return payload, header
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return payload
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def dump_payload(self, header, obj):
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base64d_header = base64_encode(
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self.serializer.dumps(header, **self.serializer_kwargs)
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)
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base64d_payload = base64_encode(
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self.serializer.dumps(obj, **self.serializer_kwargs)
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)
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return base64d_header + b"." + base64d_payload
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def make_algorithm(self, algorithm_name):
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try:
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return self.jws_algorithms[algorithm_name]
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except KeyError:
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raise NotImplementedError("Algorithm not supported")
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def make_signer(self, salt=None, algorithm=None):
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if salt is None:
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salt = self.salt
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key_derivation = "none" if salt is None else None
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if algorithm is None:
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algorithm = self.algorithm
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return self.signer(
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self.secret_key,
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salt=salt,
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sep=".",
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key_derivation=key_derivation,
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algorithm=algorithm,
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)
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def make_header(self, header_fields):
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header = header_fields.copy() if header_fields else {}
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header["alg"] = self.algorithm_name
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return header
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def dumps(self, obj, salt=None, header_fields=None):
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"""Like :meth:`.Serializer.dumps` but creates a JSON Web
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Signature. It also allows for specifying additional fields to be
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included in the JWS header.
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"""
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header = self.make_header(header_fields)
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signer = self.make_signer(salt, self.algorithm)
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return signer.sign(self.dump_payload(header, obj))
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def loads(self, s, salt=None, return_header=False):
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"""Reverse of :meth:`dumps`. If requested via ``return_header``
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it will return a tuple of payload and header.
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"""
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payload, header = self.load_payload(
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self.make_signer(salt, self.algorithm).unsign(want_bytes(s)),
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return_header=True,
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)
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if header.get("alg") != self.algorithm_name:
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raise BadHeader("Algorithm mismatch", header=header, payload=payload)
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if return_header:
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return payload, header
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return payload
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def loads_unsafe(self, s, salt=None, return_header=False):
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kwargs = {"return_header": return_header}
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return self._loads_unsafe_impl(s, salt, kwargs, kwargs)
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class TimedJSONWebSignatureSerializer(JSONWebSignatureSerializer):
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"""Works like the regular :class:`JSONWebSignatureSerializer` but
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also records the time of the signing and can be used to expire
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signatures.
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JWS currently does not specify this behavior but it mentions a
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possible extension like this in the spec. Expiry date is encoded
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into the header similar to what's specified in `draft-ietf-oauth
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-json-web-token <http://self-issued.info/docs/draft-ietf-oauth-json
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-web-token.html#expDef>`_.
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"""
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DEFAULT_EXPIRES_IN = 3600
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def __init__(self, secret_key, expires_in=None, **kwargs):
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JSONWebSignatureSerializer.__init__(self, secret_key, **kwargs)
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if expires_in is None:
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expires_in = self.DEFAULT_EXPIRES_IN
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self.expires_in = expires_in
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def make_header(self, header_fields):
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header = JSONWebSignatureSerializer.make_header(self, header_fields)
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iat = self.now()
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exp = iat + self.expires_in
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header["iat"] = iat
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header["exp"] = exp
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return header
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def loads(self, s, salt=None, return_header=False):
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payload, header = JSONWebSignatureSerializer.loads(
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self, s, salt, return_header=True
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)
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if "exp" not in header:
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raise BadSignature("Missing expiry date", payload=payload)
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int_date_error = BadHeader("Expiry date is not an IntDate", payload=payload)
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try:
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header["exp"] = int(header["exp"])
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except ValueError:
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raise int_date_error
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if header["exp"] < 0:
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raise int_date_error
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if header["exp"] < self.now():
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raise SignatureExpired(
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"Signature expired",
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payload=payload,
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date_signed=self.get_issue_date(header),
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)
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if return_header:
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return payload, header
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return payload
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def get_issue_date(self, header):
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rv = header.get("iat")
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if isinstance(rv, number_types):
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return datetime.utcfromtimestamp(int(rv))
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def now(self):
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return int(time.time())
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