10 files changed, 1075 insertions, 0 deletions
diff --git a/python/itsdangerous/__init__.py b/python/itsdangerous/__init__.py
new file mode 100644
index 0000000..0fcd8c1
--- /dev/null
+++ b/python/itsdangerous/__init__.py
@@ -0,0 +1,22 @@
+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 BadTimeSignature
+from .exc import SignatureExpired
+from .jws import JSONWebSignatureSerializer
+from .jws import TimedJSONWebSignatureSerializer
+from .serializer import Serializer
+from .signer import HMACAlgorithm
+from .signer import NoneAlgorithm
+from .signer import Signer
+from .timed import TimedSerializer
+from .timed import TimestampSigner
+from .url_safe import URLSafeSerializer
+from .url_safe import URLSafeTimedSerializer
+
+__version__ = "1.1.0"
diff --git a/python/itsdangerous/_compat.py b/python/itsdangerous/_compat.py
new file mode 100644
index 0000000..2291bce
--- /dev/null
+++ b/python/itsdangerous/_compat.py
@@ -0,0 +1,46 @@
+import decimal
+import hmac
+import numbers
+import sys
+
+PY2 = sys.version_info[0] == 2
+
+if PY2:
+    from itertools import izip
+
+    text_type = unicode  # noqa: 821
+else:
+    izip = zip
+    text_type = str
+
+number_types = (numbers.Real, decimal.Decimal)
+
+
+def _constant_time_compare(val1, val2):
+    """Return ``True`` if the two strings are equal, ``False``
+    otherwise.
+
+    The time taken is independent of the number of characters that
+    match. Do not use this function for anything else than comparision
+    with known length targets.
+
+    This is should be implemented in C in order to get it completely
+    right.
+
+    This is an alias of :func:`hmac.compare_digest` on Python>=2.7,3.3.
+    """
+    len_eq = len(val1) == len(val2)
+    if len_eq:
+        result = 0
+        left = val1
+    else:
+        result = 1
+        left = val2
+    for x, y in izip(bytearray(left), bytearray(val2)):
+        result |= x ^ y
+    return result == 0
+
+
+# Starting with 2.7/3.3 the standard library has a c-implementation for
+# constant time string compares.
+constant_time_compare = getattr(hmac, "compare_digest", _constant_time_compare)
diff --git a/python/itsdangerous/_json.py b/python/itsdangerous/_json.py
new file mode 100644
index 0000000..426b36e
--- /dev/null
+++ b/python/itsdangerous/_json.py
@@ -0,0 +1,18 @@
+try:
+    import simplejson as json
+except ImportError:
+    import json
+
+
+class _CompactJSON(object):
+    """Wrapper around json module that strips whitespace."""
+
+    @staticmethod
+    def loads(payload):
+        return json.loads(payload)
+
+    @staticmethod
+    def dumps(obj, **kwargs):
+        kwargs.setdefault("ensure_ascii", False)
+        kwargs.setdefault("separators", (",", ":"))
+        return json.dumps(obj, **kwargs)
diff --git a/python/itsdangerous/encoding.py b/python/itsdangerous/encoding.py
new file mode 100644
index 0000000..1e28969
--- /dev/null
+++ b/python/itsdangerous/encoding.py
@@ -0,0 +1,49 @@
+import base64
+import string
+import struct
+
+from ._compat import text_type
+from .exc import BadData
+
+
+def want_bytes(s, encoding="utf-8", errors="strict"):
+    if isinstance(s, text_type):
+        s = s.encode(encoding, errors)
+    return s
+
+
+def base64_encode(string):
+    """Base64 encode a string of bytes or text. The resulting bytes are
+    safe to use in URLs.
+    """
+    string = want_bytes(string)
+    return base64.urlsafe_b64encode(string).rstrip(b"=")
+
+
+def base64_decode(string):
+    """Base64 decode a URL-safe string of bytes or text. The result is
+    bytes.
+    """
+    string = want_bytes(string, encoding="ascii", errors="ignore")
+    string += b"=" * (-len(string) % 4)
+
+    try:
+        return base64.urlsafe_b64decode(string)
+    except (TypeError, ValueError):
+        raise BadData("Invalid base64-encoded data")
+
+
+# The alphabet used by base64.urlsafe_*
+_base64_alphabet = (string.ascii_letters + string.digits + "-_=").encode("ascii")
+
+_int64_struct = struct.Struct(">Q")
+_int_to_bytes = _int64_struct.pack
+_bytes_to_int = _int64_struct.unpack
+
+
+def int_to_bytes(num):
+    return _int_to_bytes(num).lstrip(b"\x00")
+
+
+def bytes_to_int(bytestr):
+    return _bytes_to_int(bytestr.rjust(8, b"\x00"))[0]
diff --git a/python/itsdangerous/exc.py b/python/itsdangerous/exc.py
new file mode 100644
index 0000000..287d691
--- /dev/null
+++ b/python/itsdangerous/exc.py
@@ -0,0 +1,98 @@
+from ._compat import PY2
+from ._compat import text_type
+
+
+class BadData(Exception):
+    """Raised if bad data of any sort was encountered. This is the base
+    for all exceptions that itsdangerous defines.
+
+    .. versionadded:: 0.15
+    """
+
+    message = None
+
+    def __init__(self, message):
+        super(BadData, self).__init__(self, message)
+        self.message = message
+
+    def __str__(self):
+        return text_type(self.message)
+
+    if PY2:
+        __unicode__ = __str__
+
+        def __str__(self):
+            return self.__unicode__().encode("utf-8")
+
+
+class BadSignature(BadData):
+    """Raised if a signature does not match."""
+
+    def __init__(self, message, payload=None):
+        BadData.__init__(self, message)
+
+        #: The payload that failed the signature test. In some
+        #: situations you might still want to inspect this, even if
+        #: you know it was tampered with.
+        #:
+        #: .. versionadded:: 0.14
+        self.payload = payload
+
+
+class BadTimeSignature(BadSignature):
+    """Raised if a time-based signature is invalid. This is a subclass
+    of :class:`BadSignature`.
+    """
+
+    def __init__(self, message, payload=None, date_signed=None):
+        BadSignature.__init__(self, message, payload)
+
+        #: If the signature expired this exposes the date of when the
+        #: signature was created. This can be helpful in order to
+        #: tell the user how long a link has been gone stale.
+        #:
+        #: .. versionadded:: 0.14
+        self.date_signed = date_signed
+
+
+class SignatureExpired(BadTimeSignature):
+    """Raised if a signature timestamp is older than ``max_age``. This
+    is a subclass of :exc:`BadTimeSignature`.
+    """
+
+
+class BadHeader(BadSignature):
+    """Raised if a signed header is invalid in some form. This only
+    happens for serializers that have a header that goes with the
+    signature.
+
+    .. versionadded:: 0.24
+    """
+
+    def __init__(self, message, payload=None, header=None, original_error=None):
+        BadSignature.__init__(self, message, payload)
+
+        #: If the header is actually available but just malformed it
+        #: might be stored here.
+        self.header = header
+
+        #: If available, the error that indicates why the payload was
+        #: not valid. This might be ``None``.
+        self.original_error = original_error
+
+
+class BadPayload(BadData):
+    """Raised if a payload is invalid. This could happen if the payload
+    is loaded despite an invalid signature, or if there is a mismatch
+    between the serializer and deserializer. The original exception
+    that occurred during loading is stored on as :attr:`original_error`.
+
+    .. versionadded:: 0.15
+    """
+
+    def __init__(self, message, original_error=None):
+        BadData.__init__(self, message)
+
+        #: If available, the error that indicates why the payload was
+        #: not valid. This might be ``None``.
+        self.original_error = original_error
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())
diff --git a/python/itsdangerous/serializer.py b/python/itsdangerous/serializer.py
new file mode 100644
index 0000000..12c20f4
--- /dev/null
+++ b/python/itsdangerous/serializer.py
@@ -0,0 +1,233 @@
+import hashlib
+
+from ._compat import text_type
+from ._json import json
+from .encoding import want_bytes
+from .exc import BadPayload
+from .exc import BadSignature
+from .signer import Signer
+
+
+def is_text_serializer(serializer):
+    """Checks whether a serializer generates text or binary."""
+    return isinstance(serializer.dumps({}), text_type)
+
+
+class Serializer(object):
+    """This class provides a serialization interface on top of the
+    signer. It provides a similar API to json/pickle and other modules
+    but is structured differently internally. If you want to change the
+    underlying implementation for parsing and loading you have to
+    override the :meth:`load_payload` and :meth:`dump_payload`
+    functions.
+
+    This implementation uses simplejson if available for dumping and
+    loading and will fall back to the standard library's json module if
+    it's not available.
+
+    You do not need to subclass this class in order to switch out or
+    customize the :class:`.Signer`. You can instead pass a different
+    class to the constructor as well as keyword arguments as a dict that
+    should be forwarded.
+
+    .. code-block:: python
+
+        s = Serializer(signer_kwargs={'key_derivation': 'hmac'})
+
+    You may want to upgrade the signing parameters without invalidating
+    existing signatures that are in use. Fallback signatures can be
+    given that will be tried if unsigning with the current signer fails.
+
+    Fallback signers can be defined by providing a list of
+    ``fallback_signers``. Each item can be one of the following: a
+    signer class (which is instantiated with ``signer_kwargs``,
+    ``salt``, and ``secret_key``), a tuple
+    ``(signer_class, signer_kwargs)``, or a dict of ``signer_kwargs``.
+
+    For example, this is a serializer that signs using SHA-512, but will
+    unsign using either SHA-512 or SHA1:
+
+    .. code-block:: python
+
+        s = Serializer(
+            signer_kwargs={"digest_method": hashlib.sha512},
+            fallback_signers=[{"digest_method": hashlib.sha1}]
+        )
+
+    .. versionchanged:: 0.14:
+        The ``signer`` and ``signer_kwargs`` parameters were added to
+        the constructor.
+
+    .. versionchanged:: 1.1.0:
+        Added support for ``fallback_signers`` and configured a default
+        SHA-512 fallback. This fallback is for users who used the yanked
+        1.0.0 release which defaulted to SHA-512.
+    """
+
+    #: If a serializer module or class is not passed to the constructor
+    #: this one is picked up. This currently defaults to :mod:`json`.
+    default_serializer = json
+
+    #: The default :class:`Signer` class that is being used by this
+    #: serializer.
+    #:
+    #: .. versionadded:: 0.14
+    default_signer = Signer
+
+    #: The default fallback signers.
+    default_fallback_signers = [{"digest_method": hashlib.sha512}]
+
+    def __init__(
+        self,
+        secret_key,
+        salt=b"itsdangerous",
+        serializer=None,
+        serializer_kwargs=None,
+        signer=None,
+        signer_kwargs=None,
+        fallback_signers=None,
+    ):
+        self.secret_key = want_bytes(secret_key)
+        self.salt = want_bytes(salt)
+        if serializer is None:
+            serializer = self.default_serializer
+        self.serializer = serializer
+        self.is_text_serializer = is_text_serializer(serializer)
+        if signer is None:
+            signer = self.default_signer
+        self.signer = signer
+        self.signer_kwargs = signer_kwargs or {}
+        if fallback_signers is None:
+            fallback_signers = list(self.default_fallback_signers or ())
+        self.fallback_signers = fallback_signers
+        self.serializer_kwargs = serializer_kwargs or {}
+
+    def load_payload(self, payload, serializer=None):
+        """Loads the encoded object. This function raises
+        :class:`.BadPayload` if the payload is not valid. The
+        ``serializer`` parameter can be used to override the serializer
+        stored on the class. The encoded ``payload`` should always be
+        bytes.
+        """
+        if serializer is None:
+            serializer = self.serializer
+            is_text = self.is_text_serializer
+        else:
+            is_text = is_text_serializer(serializer)
+        try:
+            if is_text:
+                payload = payload.decode("utf-8")
+            return serializer.loads(payload)
+        except Exception as e:
+            raise BadPayload(
+                "Could not load the payload because an exception"
+                " occurred on unserializing the data.",
+                original_error=e,
+            )
+
+    def dump_payload(self, obj):
+        """Dumps the encoded object. The return value is always bytes.
+        If the internal serializer returns text, the value will be
+        encoded as UTF-8.
+        """
+        return want_bytes(self.serializer.dumps(obj, **self.serializer_kwargs))
+
+    def make_signer(self, salt=None):
+        """Creates a new instance of the signer to be used. The default
+        implementation uses the :class:`.Signer` base class.
+        """
+        if salt is None:
+            salt = self.salt
+        return self.signer(self.secret_key, salt=salt, **self.signer_kwargs)
+
+    def iter_unsigners(self, salt=None):
+        """Iterates over all signers to be tried for unsigning. Starts
+        with the configured signer, then constructs each signer
+        specified in ``fallback_signers``.
+        """
+        if salt is None:
+            salt = self.salt
+        yield self.make_signer(salt)
+        for fallback in self.fallback_signers:
+            if type(fallback) is dict:
+                kwargs = fallback
+                fallback = self.signer
+            elif type(fallback) is tuple:
+                fallback, kwargs = fallback
+            else:
+                kwargs = self.signer_kwargs
+            yield fallback(self.secret_key, salt=salt, **kwargs)
+
+    def dumps(self, obj, salt=None):
+        """Returns a signed string serialized with the internal
+        serializer. The return value can be either a byte or unicode
+        string depending on the format of the internal serializer.
+        """
+        payload = want_bytes(self.dump_payload(obj))
+        rv = self.make_signer(salt).sign(payload)
+        if self.is_text_serializer:
+            rv = rv.decode("utf-8")
+        return rv
+
+    def dump(self, obj, f, salt=None):
+        """Like :meth:`dumps` but dumps into a file. The file handle has
+        to be compatible with what the internal serializer expects.
+        """
+        f.write(self.dumps(obj, salt))
+
+    def loads(self, s, salt=None):
+        """Reverse of :meth:`dumps`. Raises :exc:`.BadSignature` if the
+        signature validation fails.
+        """
+        s = want_bytes(s)
+        last_exception = None
+        for signer in self.iter_unsigners(salt):
+            try:
+                return self.load_payload(signer.unsign(s))
+            except BadSignature as err:
+                last_exception = err
+        raise last_exception
+
+    def load(self, f, salt=None):
+        """Like :meth:`loads` but loads from a file."""
+        return self.loads(f.read(), salt)
+
+    def loads_unsafe(self, s, salt=None):
+        """Like :meth:`loads` but without verifying the signature. This
+        is potentially very dangerous to use depending on how your
+        serializer works. The return value is ``(signature_valid,
+        payload)`` instead of just the payload. The first item will be a
+        boolean that indicates if the signature is valid. This function
+        never fails.
+
+        Use it for debugging only and if you know that your serializer
+        module is not exploitable (for example, do not use it with a
+        pickle serializer).
+
+        .. versionadded:: 0.15
+        """
+        return self._loads_unsafe_impl(s, salt)
+
+    def _loads_unsafe_impl(self, s, salt, load_kwargs=None, load_payload_kwargs=None):
+        """Low level helper function to implement :meth:`loads_unsafe`
+        in serializer subclasses.
+        """
+        try:
+            return True, self.loads(s, salt=salt, **(load_kwargs or {}))
+        except BadSignature as e:
+            if e.payload is None:
+                return False, None
+            try:
+                return (
+                    False,
+                    self.load_payload(e.payload, **(load_payload_kwargs or {})),
+                )
+            except BadPayload:
+                return False, None
+
+    def load_unsafe(self, f, *args, **kwargs):
+        """Like :meth:`loads_unsafe` but loads from a file.
+
+        .. versionadded:: 0.15
+        """
+        return self.loads_unsafe(f.read(), *args, **kwargs)
diff --git a/python/itsdangerous/signer.py b/python/itsdangerous/signer.py
new file mode 100644
index 0000000..6bddc03
--- /dev/null
+++ b/python/itsdangerous/signer.py
@@ -0,0 +1,179 @@
+import hashlib
+import hmac
+
+from ._compat import constant_time_compare
+from .encoding import _base64_alphabet
+from .encoding import base64_decode
+from .encoding import base64_encode
+from .encoding import want_bytes
+from .exc import BadSignature
+
+
+class SigningAlgorithm(object):
+    """Subclasses must implement :meth:`get_signature` to provide
+    signature generation functionality.
+    """
+
+    def get_signature(self, key, value):
+        """Returns the signature for the given key and value."""
+        raise NotImplementedError()
+
+    def verify_signature(self, key, value, sig):
+        """Verifies the given signature matches the expected
+        signature.
+        """
+        return constant_time_compare(sig, self.get_signature(key, value))
+
+
+class NoneAlgorithm(SigningAlgorithm):
+    """Provides an algorithm that does not perform any signing and
+    returns an empty signature.
+    """
+
+    def get_signature(self, key, value):
+        return b""
+
+
+class HMACAlgorithm(SigningAlgorithm):
+    """Provides signature generation using HMACs."""
+
+    #: The digest method to use with the MAC algorithm. This defaults to
+    #: SHA1, but can be changed to any other function in the hashlib
+    #: module.
+    default_digest_method = staticmethod(hashlib.sha1)
+
+    def __init__(self, digest_method=None):
+        if digest_method is None:
+            digest_method = self.default_digest_method
+        self.digest_method = digest_method
+
+    def get_signature(self, key, value):
+        mac = hmac.new(key, msg=value, digestmod=self.digest_method)
+        return mac.digest()
+
+
+class Signer(object):
+    """This class can sign and unsign bytes, validating the signature
+    provided.
+
+    Salt can be used to namespace the hash, so that a signed string is
+    only valid for a given namespace. Leaving this at the default value
+    or re-using a salt value across different parts of your application
+    where the same signed value in one part can mean something different
+    in another part is a security risk.
+
+    See :ref:`the-salt` for an example of what the salt is doing and how
+    you can utilize it.
+
+    .. versionadded:: 0.14
+        ``key_derivation`` and ``digest_method`` were added as arguments
+        to the class constructor.
+
+    .. versionadded:: 0.18
+        ``algorithm`` was added as an argument to the class constructor.
+    """
+
+    #: The digest method to use for the signer.  This defaults to
+    #: SHA1 but can be changed to any other function in the hashlib
+    #: module.
+    #:
+    #: .. versionadded:: 0.14
+    default_digest_method = staticmethod(hashlib.sha1)
+
+    #: Controls how the key is derived. The default is Django-style
+    #: concatenation. Possible values are ``concat``, ``django-concat``
+    #: and ``hmac``. This is used for deriving a key from the secret key
+    #: with an added salt.
+    #:
+    #: .. versionadded:: 0.14
+    default_key_derivation = "django-concat"
+
+    def __init__(
+        self,
+        secret_key,
+        salt=None,
+        sep=".",
+        key_derivation=None,
+        digest_method=None,
+        algorithm=None,
+    ):
+        self.secret_key = want_bytes(secret_key)
+        self.sep = want_bytes(sep)
+        if self.sep in _base64_alphabet:
+            raise ValueError(
+                "The given separator cannot be used because it may be"
+                " contained in the signature itself. Alphanumeric"
+                " characters and `-_=` must not be used."
+            )
+        self.salt = "itsdangerous.Signer" if salt is None else salt
+        if key_derivation is None:
+            key_derivation = self.default_key_derivation
+        self.key_derivation = key_derivation
+        if digest_method is None:
+            digest_method = self.default_digest_method
+        self.digest_method = digest_method
+        if algorithm is None:
+            algorithm = HMACAlgorithm(self.digest_method)
+        self.algorithm = algorithm
+
+    def derive_key(self):
+        """This method is called to derive the key. The default key
+        derivation choices can be overridden here. Key derivation is not
+        intended to be used as a security method to make a complex key
+        out of a short password. Instead you should use large random
+        secret keys.
+        """
+        salt = want_bytes(self.salt)
+        if self.key_derivation == "concat":
+            return self.digest_method(salt + self.secret_key).digest()
+        elif self.key_derivation == "django-concat":
+            return self.digest_method(salt + b"signer" + self.secret_key).digest()
+        elif self.key_derivation == "hmac":
+            mac = hmac.new(self.secret_key, digestmod=self.digest_method)
+            mac.update(salt)
+            return mac.digest()
+        elif self.key_derivation == "none":
+            return self.secret_key
+        else:
+            raise TypeError("Unknown key derivation method")
+
+    def get_signature(self, value):
+        """Returns the signature for the given value."""
+        value = want_bytes(value)
+        key = self.derive_key()
+        sig = self.algorithm.get_signature(key, value)
+        return base64_encode(sig)
+
+    def sign(self, value):
+        """Signs the given string."""
+        return want_bytes(value) + want_bytes(self.sep) + self.get_signature(value)
+
+    def verify_signature(self, value, sig):
+        """Verifies the signature for the given value."""
+        key = self.derive_key()
+        try:
+            sig = base64_decode(sig)
+        except Exception:
+            return False
+        return self.algorithm.verify_signature(key, value, sig)
+
+    def unsign(self, signed_value):
+        """Unsigns the given string."""
+        signed_value = want_bytes(signed_value)
+        sep = want_bytes(self.sep)
+        if sep not in signed_value:
+            raise BadSignature("No %r found in value" % self.sep)
+        value, sig = signed_value.rsplit(sep, 1)
+        if self.verify_signature(value, sig):
+            return value
+        raise BadSignature("Signature %r does not match" % sig, payload=value)
+
+    def validate(self, signed_value):
+        """Only validates the given signed value. Returns ``True`` if
+        the signature exists and is valid.
+        """
+        try:
+            self.unsign(signed_value)
+            return True
+        except BadSignature:
+            return False
diff --git a/python/itsdangerous/timed.py b/python/itsdangerous/timed.py
new file mode 100644
index 0000000..4c117e4
--- /dev/null
+++ b/python/itsdangerous/timed.py
@@ -0,0 +1,147 @@
+import time
+from datetime import datetime
+
+from ._compat import text_type
+from .encoding import base64_decode
+from .encoding import base64_encode
+from .encoding import bytes_to_int
+from .encoding import int_to_bytes
+from .encoding import want_bytes
+from .exc import BadSignature
+from .exc import BadTimeSignature
+from .exc import SignatureExpired
+from .serializer import Serializer
+from .signer import Signer
+
+
+class TimestampSigner(Signer):
+    """Works like the regular :class:`.Signer` but also records the time
+    of the signing and can be used to expire signatures. The
+    :meth:`unsign` method can raise :exc:`.SignatureExpired` if the
+    unsigning failed because the signature is expired.
+    """
+
+    def get_timestamp(self):
+        """Returns the current timestamp. The function must return an
+        integer.
+        """
+        return int(time.time())
+
+    def timestamp_to_datetime(self, ts):
+        """Used to convert the timestamp from :meth:`get_timestamp` into
+        a datetime object.
+        """
+        return datetime.utcfromtimestamp(ts)
+
+    def sign(self, value):
+        """Signs the given string and also attaches time information."""
+        value = want_bytes(value)
+        timestamp = base64_encode(int_to_bytes(self.get_timestamp()))
+        sep = want_bytes(self.sep)
+        value = value + sep + timestamp
+        return value + sep + self.get_signature(value)
+
+    def unsign(self, value, max_age=None, return_timestamp=False):
+        """Works like the regular :meth:`.Signer.unsign` but can also
+        validate the time. See the base docstring of the class for
+        the general behavior. If ``return_timestamp`` is ``True`` the
+        timestamp of the signature will be returned as a naive
+        :class:`datetime.datetime` object in UTC.
+        """
+        try:
+            result = Signer.unsign(self, value)
+            sig_error = None
+        except BadSignature as e:
+            sig_error = e
+            result = e.payload or b""
+        sep = want_bytes(self.sep)
+
+        # If there is no timestamp in the result there is something
+        # seriously wrong. In case there was a signature error, we raise
+        # that one directly, otherwise we have a weird situation in
+        # which we shouldn't have come except someone uses a time-based
+        # serializer on non-timestamp data, so catch that.
+        if sep not in result:
+            if sig_error:
+                raise sig_error
+            raise BadTimeSignature("timestamp missing", payload=result)
+
+        value, timestamp = result.rsplit(sep, 1)
+        try:
+            timestamp = bytes_to_int(base64_decode(timestamp))
+        except Exception:
+            timestamp = None
+
+        # Signature is *not* okay. Raise a proper error now that we have
+        # split the value and the timestamp.
+        if sig_error is not None:
+            raise BadTimeSignature(
+                text_type(sig_error), payload=value, date_signed=timestamp
+            )
+
+        # Signature was okay but the timestamp is actually not there or
+        # malformed. Should not happen, but we handle it anyway.
+        if timestamp is None:
+            raise BadTimeSignature("Malformed timestamp", payload=value)
+
+        # Check timestamp is not older than max_age
+        if max_age is not None:
+            age = self.get_timestamp() - timestamp
+            if age > max_age:
+                raise SignatureExpired(
+                    "Signature age %s > %s seconds" % (age, max_age),
+                    payload=value,
+                    date_signed=self.timestamp_to_datetime(timestamp),
+                )
+
+        if return_timestamp:
+            return value, self.timestamp_to_datetime(timestamp)
+        return value
+
+    def validate(self, signed_value, max_age=None):
+        """Only validates the given signed value. Returns ``True`` if
+        the signature exists and is valid."""
+        try:
+            self.unsign(signed_value, max_age=max_age)
+            return True
+        except BadSignature:
+            return False
+
+
+class TimedSerializer(Serializer):
+    """Uses :class:`TimestampSigner` instead of the default
+    :class:`.Signer`.
+    """
+
+    default_signer = TimestampSigner
+
+    def loads(self, s, max_age=None, return_timestamp=False, salt=None):
+        """Reverse of :meth:`dumps`, raises :exc:`.BadSignature` if the
+        signature validation fails. If a ``max_age`` is provided it will
+        ensure the signature is not older than that time in seconds. In
+        case the signature is outdated, :exc:`.SignatureExpired` is
+        raised. All arguments are forwarded to the signer's
+        :meth:`~TimestampSigner.unsign` method.
+        """
+        s = want_bytes(s)
+        last_exception = None
+        for signer in self.iter_unsigners(salt):
+            try:
+                base64d, timestamp = signer.unsign(s, max_age, return_timestamp=True)
+                payload = self.load_payload(base64d)
+                if return_timestamp:
+                    return payload, timestamp
+                return payload
+            # If we get a signature expired it means we could read the
+            # signature but it's invalid.  In that case we do not want to
+            # try the next signer.
+            except SignatureExpired:
+                raise
+            except BadSignature as err:
+                last_exception = err
+        raise last_exception
+
+    def loads_unsafe(self, s, max_age=None, salt=None):
+        load_kwargs = {"max_age": max_age}
+        load_payload_kwargs = {}
+        return self._loads_unsafe_impl(s, salt, load_kwargs, load_payload_kwargs)
diff --git a/python/itsdangerous/url_safe.py b/python/itsdangerous/url_safe.py
new file mode 100644
index 0000000..fcaa011
--- /dev/null
+++ b/python/itsdangerous/url_safe.py
@@ -0,0 +1,65 @@
+import zlib
+
+from ._json import _CompactJSON
+from .encoding import base64_decode
+from .encoding import base64_encode
+from .exc import BadPayload
+from .serializer import Serializer
+from .timed import TimedSerializer
+
+
+class URLSafeSerializerMixin(object):
+    """Mixed in with a regular serializer it will attempt to zlib
+    compress the string to make it shorter if necessary. It will also
+    base64 encode the string so that it can safely be placed in a URL.
+    """
+
+    default_serializer = _CompactJSON
+
+    def load_payload(self, payload, *args, **kwargs):
+        decompress = False
+        if payload.startswith(b"."):
+            payload = payload[1:]
+            decompress = True
+        try:
+            json = base64_decode(payload)
+        except Exception as e:
+            raise BadPayload(
+                "Could not base64 decode the payload because of an exception",
+                original_error=e,
+            )
+        if decompress:
+            try:
+                json = zlib.decompress(json)
+            except Exception as e:
+                raise BadPayload(
+                    "Could not zlib decompress the payload before decoding the payload",
+                    original_error=e,
+                )
+        return super(URLSafeSerializerMixin, self).load_payload(json, *args, **kwargs)
+
+    def dump_payload(self, obj):
+        json = super(URLSafeSerializerMixin, self).dump_payload(obj)
+        is_compressed = False
+        compressed = zlib.compress(json)
+        if len(compressed) < (len(json) - 1):
+            json = compressed
+            is_compressed = True
+        base64d = base64_encode(json)
+        if is_compressed:
+            base64d = b"." + base64d
+        return base64d
+
+
+class URLSafeSerializer(URLSafeSerializerMixin, Serializer):
+    """Works like :class:`.Serializer` but dumps and loads into a URL
+    safe string consisting of the upper and lowercase character of the
+    alphabet as well as ``'_'``, ``'-'`` and ``'.'``.
+    """
+
+
+class URLSafeTimedSerializer(URLSafeSerializerMixin, TimedSerializer):
+    """Works like :class:`.TimedSerializer` but dumps and loads into a
+    URL safe string consisting of the upper and lowercase character of
+    the alphabet as well as ``'_'``, ``'-'`` and ``'.'``.
+    """