1 files changed, 218 insertions, 0 deletions
diff --git a/python/itsdangerous/jws.py b/python/itsdangerous/jws.py
new file mode 100644
index 0000000..92e9ec8
--- /dev/null
+++ b/python/itsdangerous/jws.py
@@ -0,0 +1,218 @@
+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())