You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
296 lines
11 KiB
Python
296 lines
11 KiB
Python
2 years ago
|
import json
|
||
|
|
import typing as _t
|
||
|
|
|
||
|
|
from .encoding import want_bytes
|
||
|
|
from .exc import BadPayload
|
||
|
|
from .exc import BadSignature
|
||
|
|
from .signer import _make_keys_list
|
||
|
|
from .signer import Signer
|
||
|
|
|
||
|
|
_t_str_bytes = _t.Union[str, bytes]
|
||
|
|
_t_opt_str_bytes = _t.Optional[_t_str_bytes]
|
||
|
|
_t_kwargs = _t.Dict[str, _t.Any]
|
||
|
|
_t_opt_kwargs = _t.Optional[_t_kwargs]
|
||
|
|
_t_signer = _t.Type[Signer]
|
||
|
|
_t_fallbacks = _t.List[_t.Union[_t_kwargs, _t.Tuple[_t_signer, _t_kwargs], _t_signer]]
|
||
|
|
_t_load_unsafe = _t.Tuple[bool, _t.Any]
|
||
|
|
_t_secret_key = _t.Union[_t.Iterable[_t_str_bytes], _t_str_bytes]
|
||
|
|
|
||
|
|
|
||
|
|
def is_text_serializer(serializer: _t.Any) -> bool:
|
||
|
|
"""Checks whether a serializer generates text or binary."""
|
||
|
|
return isinstance(serializer.dumps({}), str)
|
||
|
|
|
||
|
|
|
||
|
|
class Serializer:
|
||
|
|
"""A serializer wraps a :class:`~itsdangerous.signer.Signer` to
|
||
|
|
enable serializing and securely signing data other than bytes. It
|
||
|
|
can unsign to verify that the data hasn't been changed.
|
||
|
|
|
||
|
|
The serializer provides :meth:`dumps` and :meth:`loads`, similar to
|
||
|
|
:mod:`json`, and by default uses :mod:`json` internally to serialize
|
||
|
|
the data to bytes.
|
||
|
|
|
||
|
|
The secret key should be a random string of ``bytes`` and should not
|
||
|
|
be saved to code or version control. Different salts should be used
|
||
|
|
to distinguish signing in different contexts. See :doc:`/concepts`
|
||
|
|
for information about the security of the secret key and salt.
|
||
|
|
|
||
|
|
:param secret_key: The secret key to sign and verify with. Can be a
|
||
|
|
list of keys, oldest to newest, to support key rotation.
|
||
|
|
:param salt: Extra key to combine with ``secret_key`` to distinguish
|
||
|
|
signatures in different contexts.
|
||
|
|
:param serializer: An object that provides ``dumps`` and ``loads``
|
||
|
|
methods for serializing data to a string. Defaults to
|
||
|
|
:attr:`default_serializer`, which defaults to :mod:`json`.
|
||
|
|
:param serializer_kwargs: Keyword arguments to pass when calling
|
||
|
|
``serializer.dumps``.
|
||
|
|
:param signer: A ``Signer`` class to instantiate when signing data.
|
||
|
|
Defaults to :attr:`default_signer`, which defaults to
|
||
|
|
:class:`~itsdangerous.signer.Signer`.
|
||
|
|
:param signer_kwargs: Keyword arguments to pass when instantiating
|
||
|
|
the ``Signer`` class.
|
||
|
|
:param fallback_signers: List of signer parameters to try when
|
||
|
|
unsigning with the default signer fails. Each item can be a dict
|
||
|
|
of ``signer_kwargs``, a ``Signer`` class, or a tuple of
|
||
|
|
``(signer, signer_kwargs)``. Defaults to
|
||
|
|
:attr:`default_fallback_signers`.
|
||
|
|
|
||
|
|
.. versionchanged:: 2.0
|
||
|
|
Added support for key rotation by passing a list to
|
||
|
|
``secret_key``.
|
||
|
|
|
||
|
|
.. versionchanged:: 2.0
|
||
|
|
Removed the default SHA-512 fallback signer from
|
||
|
|
``default_fallback_signers``.
|
||
|
|
|
||
|
|
.. versionchanged:: 1.1
|
||
|
|
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.
|
||
|
|
|
||
|
|
.. versionchanged:: 0.14
|
||
|
|
The ``signer`` and ``signer_kwargs`` parameters were added to
|
||
|
|
the constructor.
|
||
|
|
"""
|
||
|
|
|
||
|
|
#: The default serialization module to use to serialize data to a
|
||
|
|
#: string internally. The default is :mod:`json`, but can be changed
|
||
|
|
#: to any object that provides ``dumps`` and ``loads`` methods.
|
||
|
|
default_serializer: _t.Any = json
|
||
|
|
|
||
|
|
#: The default ``Signer`` class to instantiate when signing data.
|
||
|
|
#: The default is :class:`itsdangerous.signer.Signer`.
|
||
|
|
default_signer: _t_signer = Signer
|
||
|
|
|
||
|
|
#: The default fallback signers to try when unsigning fails.
|
||
|
|
default_fallback_signers: _t_fallbacks = []
|
||
|
|
|
||
|
|
def __init__(
|
||
|
|
self,
|
||
|
|
secret_key: _t_secret_key,
|
||
|
|
salt: _t_opt_str_bytes = b"itsdangerous",
|
||
|
|
serializer: _t.Any = None,
|
||
|
|
serializer_kwargs: _t_opt_kwargs = None,
|
||
|
|
signer: _t.Optional[_t_signer] = None,
|
||
|
|
signer_kwargs: _t_opt_kwargs = None,
|
||
|
|
fallback_signers: _t.Optional[_t_fallbacks] = None,
|
||
|
|
):
|
||
|
|
#: The list of secret keys to try for verifying signatures, from
|
||
|
|
#: oldest to newest. The newest (last) key is used for signing.
|
||
|
|
#:
|
||
|
|
#: This allows a key rotation system to keep a list of allowed
|
||
|
|
#: keys and remove expired ones.
|
||
|
|
self.secret_keys: _t.List[bytes] = _make_keys_list(secret_key)
|
||
|
|
|
||
|
|
if salt is not None:
|
||
|
|
salt = want_bytes(salt)
|
||
|
|
# if salt is None then the signer's default is used
|
||
|
|
|
||
|
|
self.salt = salt
|
||
|
|
|
||
|
|
if serializer is None:
|
||
|
|
serializer = self.default_serializer
|
||
|
|
|
||
|
|
self.serializer: _t.Any = serializer
|
||
|
|
self.is_text_serializer: bool = is_text_serializer(serializer)
|
||
|
|
|
||
|
|
if signer is None:
|
||
|
|
signer = self.default_signer
|
||
|
|
|
||
|
|
self.signer: _t_signer = signer
|
||
|
|
self.signer_kwargs: _t_kwargs = signer_kwargs or {}
|
||
|
|
|
||
|
|
if fallback_signers is None:
|
||
|
|
fallback_signers = list(self.default_fallback_signers or ())
|
||
|
|
|
||
|
|
self.fallback_signers: _t_fallbacks = fallback_signers
|
||
|
|
self.serializer_kwargs: _t_kwargs = serializer_kwargs or {}
|
||
|
|
|
||
|
|
@property
|
||
|
|
def secret_key(self) -> bytes:
|
||
|
|
"""The newest (last) entry in the :attr:`secret_keys` list. This
|
||
|
|
is for compatibility from before key rotation support was added.
|
||
|
|
"""
|
||
|
|
return self.secret_keys[-1]
|
||
|
|
|
||
|
|
def load_payload(
|
||
|
|
self, payload: bytes, serializer: _t.Optional[_t.Any] = None
|
||
|
|
) -> _t.Any:
|
||
|
|
"""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:
|
||
|
|
return serializer.loads(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,
|
||
|
|
) from e
|
||
|
|
|
||
|
|
def dump_payload(self, obj: _t.Any) -> bytes:
|
||
|
|
"""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: _t_opt_str_bytes = None) -> Signer:
|
||
|
|
"""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_keys, salt=salt, **self.signer_kwargs)
|
||
|
|
|
||
|
|
def iter_unsigners(self, salt: _t_opt_str_bytes = None) -> _t.Iterator[Signer]:
|
||
|
|
"""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 isinstance(fallback, dict):
|
||
|
|
kwargs = fallback
|
||
|
|
fallback = self.signer
|
||
|
|
elif isinstance(fallback, tuple):
|
||
|
|
fallback, kwargs = fallback
|
||
|
|
else:
|
||
|
|
kwargs = self.signer_kwargs
|
||
|
|
|
||
|
|
for secret_key in self.secret_keys:
|
||
|
|
yield fallback(secret_key, salt=salt, **kwargs)
|
||
|
|
|
||
|
|
def dumps(self, obj: _t.Any, salt: _t_opt_str_bytes = None) -> _t_str_bytes:
|
||
|
|
"""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:
|
||
|
|
return rv.decode("utf-8")
|
||
|
|
|
||
|
|
return rv
|
||
|
|
|
||
|
|
def dump(self, obj: _t.Any, f: _t.IO, salt: _t_opt_str_bytes = None) -> 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: _t_str_bytes, salt: _t_opt_str_bytes = None, **kwargs: _t.Any
|
||
|
|
) -> _t.Any:
|
||
|
|
"""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 _t.cast(BadSignature, last_exception)
|
||
|
|
|
||
|
|
def load(self, f: _t.IO, salt: _t_opt_str_bytes = None) -> _t.Any:
|
||
|
|
"""Like :meth:`loads` but loads from a file."""
|
||
|
|
return self.loads(f.read(), salt)
|
||
|
|
|
||
|
|
def loads_unsafe(
|
||
|
|
self, s: _t_str_bytes, salt: _t_opt_str_bytes = None
|
||
|
|
) -> _t_load_unsafe:
|
||
|
|
"""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: _t_str_bytes,
|
||
|
|
salt: _t_opt_str_bytes,
|
||
|
|
load_kwargs: _t_opt_kwargs = None,
|
||
|
|
load_payload_kwargs: _t_opt_kwargs = None,
|
||
|
|
) -> _t_load_unsafe:
|
||
|
|
"""Low level helper function to implement :meth:`loads_unsafe`
|
||
|
|
in serializer subclasses.
|
||
|
|
"""
|
||
|
|
if load_kwargs is None:
|
||
|
|
load_kwargs = {}
|
||
|
|
|
||
|
|
try:
|
||
|
|
return True, self.loads(s, salt=salt, **load_kwargs)
|
||
|
|
except BadSignature as e:
|
||
|
|
if e.payload is None:
|
||
|
|
return False, None
|
||
|
|
|
||
|
|
if load_payload_kwargs is None:
|
||
|
|
load_payload_kwargs = {}
|
||
|
|
|
||
|
|
try:
|
||
|
|
return (
|
||
|
|
False,
|
||
|
|
self.load_payload(e.payload, **load_payload_kwargs),
|
||
|
|
)
|
||
|
|
except BadPayload:
|
||
|
|
return False, None
|
||
|
|
|
||
|
|
def load_unsafe(self, f: _t.IO, salt: _t_opt_str_bytes = None) -> _t_load_unsafe:
|
||
|
|
"""Like :meth:`loads_unsafe` but loads from a file.
|
||
|
|
|
||
|
|
.. versionadded:: 0.15
|
||
|
|
"""
|
||
|
|
return self.loads_unsafe(f.read(), salt=salt)
|