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bazarr/libs/itsdangerous/timed.py

148 lines
5.5 KiB

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)