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