407 lines
15 KiB
Python
407 lines
15 KiB
Python
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from __future__ import annotations
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import collections.abc as cabc
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import json
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import typing as t
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from .encoding import want_bytes
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from .exc import BadPayload
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from .exc import BadSignature
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from .signer import _make_keys_list
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from .signer import Signer
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if t.TYPE_CHECKING:
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import typing_extensions as te
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# This should be either be str or bytes. To avoid having to specify the
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# bound type, it falls back to a union if structural matching fails.
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_TSerialized = te.TypeVar(
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"_TSerialized", bound=t.Union[str, bytes], default=t.Union[str, bytes]
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)
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else:
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# Still available at runtime on Python < 3.13, but without the default.
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_TSerialized = t.TypeVar("_TSerialized", bound=t.Union[str, bytes])
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class _PDataSerializer(t.Protocol[_TSerialized]):
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def loads(self, payload: _TSerialized, /) -> t.Any: ...
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# A signature with additional arguments is not handled correctly by type
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# checkers right now, so an overload is used below for serializers that
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# don't match this strict protocol.
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def dumps(self, obj: t.Any, /) -> _TSerialized: ...
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# Use TypeIs once it's available in typing_extensions or 3.13.
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def is_text_serializer(
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serializer: _PDataSerializer[t.Any],
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) -> te.TypeGuard[_PDataSerializer[str]]:
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"""Checks whether a serializer generates text or binary."""
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return isinstance(serializer.dumps({}), str)
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class Serializer(t.Generic[_TSerialized]):
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"""A serializer wraps a :class:`~itsdangerous.signer.Signer` to
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enable serializing and securely signing data other than bytes. It
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can unsign to verify that the data hasn't been changed.
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The serializer provides :meth:`dumps` and :meth:`loads`, similar to
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:mod:`json`, and by default uses :mod:`json` internally to serialize
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the data to bytes.
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The secret key should be a random string of ``bytes`` and should not
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be saved to code or version control. Different salts should be used
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to distinguish signing in different contexts. See :doc:`/concepts`
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for information about the security of the secret key and salt.
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:param secret_key: The secret key to sign and verify with. Can be a
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list of keys, oldest to newest, to support key rotation.
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:param salt: Extra key to combine with ``secret_key`` to distinguish
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signatures in different contexts.
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:param serializer: An object that provides ``dumps`` and ``loads``
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methods for serializing data to a string. Defaults to
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:attr:`default_serializer`, which defaults to :mod:`json`.
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:param serializer_kwargs: Keyword arguments to pass when calling
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``serializer.dumps``.
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:param signer: A ``Signer`` class to instantiate when signing data.
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Defaults to :attr:`default_signer`, which defaults to
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:class:`~itsdangerous.signer.Signer`.
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:param signer_kwargs: Keyword arguments to pass when instantiating
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the ``Signer`` class.
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:param fallback_signers: List of signer parameters to try when
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unsigning with the default signer fails. Each item can be a dict
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of ``signer_kwargs``, a ``Signer`` class, or a tuple of
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``(signer, signer_kwargs)``. Defaults to
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:attr:`default_fallback_signers`.
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.. versionchanged:: 2.0
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Added support for key rotation by passing a list to
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``secret_key``.
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.. versionchanged:: 2.0
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Removed the default SHA-512 fallback signer from
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``default_fallback_signers``.
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.. versionchanged:: 1.1
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Added support for ``fallback_signers`` and configured a default
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SHA-512 fallback. This fallback is for users who used the yanked
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1.0.0 release which defaulted to SHA-512.
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.. versionchanged:: 0.14
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The ``signer`` and ``signer_kwargs`` parameters were added to
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the constructor.
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"""
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#: The default serialization module to use to serialize data to a
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#: string internally. The default is :mod:`json`, but can be changed
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#: to any object that provides ``dumps`` and ``loads`` methods.
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default_serializer: _PDataSerializer[t.Any] = json
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#: The default ``Signer`` class to instantiate when signing data.
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#: The default is :class:`itsdangerous.signer.Signer`.
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default_signer: type[Signer] = Signer
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#: The default fallback signers to try when unsigning fails.
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default_fallback_signers: list[
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dict[str, t.Any] | tuple[type[Signer], dict[str, t.Any]] | type[Signer]
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] = []
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# Serializer[str] if no data serializer is provided, or if it returns str.
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@t.overload
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def __init__(
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self: Serializer[str],
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secret_key: str | bytes | cabc.Iterable[str] | cabc.Iterable[bytes],
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salt: str | bytes | None = b"itsdangerous",
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serializer: None | _PDataSerializer[str] = None,
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serializer_kwargs: dict[str, t.Any] | None = None,
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signer: type[Signer] | None = None,
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signer_kwargs: dict[str, t.Any] | None = None,
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fallback_signers: list[
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dict[str, t.Any] | tuple[type[Signer], dict[str, t.Any]] | type[Signer]
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]
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| None = None,
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): ...
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# Serializer[bytes] with a bytes data serializer positional argument.
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@t.overload
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def __init__(
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self: Serializer[bytes],
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secret_key: str | bytes | cabc.Iterable[str] | cabc.Iterable[bytes],
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salt: str | bytes | None,
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serializer: _PDataSerializer[bytes],
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serializer_kwargs: dict[str, t.Any] | None = None,
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signer: type[Signer] | None = None,
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signer_kwargs: dict[str, t.Any] | None = None,
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fallback_signers: list[
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dict[str, t.Any] | tuple[type[Signer], dict[str, t.Any]] | type[Signer]
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]
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| None = None,
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): ...
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# Serializer[bytes] with a bytes data serializer keyword argument.
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@t.overload
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def __init__(
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self: Serializer[bytes],
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secret_key: str | bytes | cabc.Iterable[str] | cabc.Iterable[bytes],
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salt: str | bytes | None = b"itsdangerous",
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*,
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serializer: _PDataSerializer[bytes],
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serializer_kwargs: dict[str, t.Any] | None = None,
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signer: type[Signer] | None = None,
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signer_kwargs: dict[str, t.Any] | None = None,
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fallback_signers: list[
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dict[str, t.Any] | tuple[type[Signer], dict[str, t.Any]] | type[Signer]
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]
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| None = None,
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): ...
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# Fall back with a positional argument. If the strict signature of
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# _PDataSerializer doesn't match, fall back to a union, requiring the user
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# to specify the type.
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@t.overload
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def __init__(
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self,
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secret_key: str | bytes | cabc.Iterable[str] | cabc.Iterable[bytes],
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salt: str | bytes | None,
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serializer: t.Any,
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serializer_kwargs: dict[str, t.Any] | None = None,
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signer: type[Signer] | None = None,
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signer_kwargs: dict[str, t.Any] | None = None,
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fallback_signers: list[
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dict[str, t.Any] | tuple[type[Signer], dict[str, t.Any]] | type[Signer]
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]
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| None = None,
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): ...
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# Fall back with a keyword argument.
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@t.overload
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def __init__(
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self,
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secret_key: str | bytes | cabc.Iterable[str] | cabc.Iterable[bytes],
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salt: str | bytes | None = b"itsdangerous",
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*,
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serializer: t.Any,
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serializer_kwargs: dict[str, t.Any] | None = None,
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signer: type[Signer] | None = None,
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signer_kwargs: dict[str, t.Any] | None = None,
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fallback_signers: list[
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dict[str, t.Any] | tuple[type[Signer], dict[str, t.Any]] | type[Signer]
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]
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| None = None,
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): ...
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def __init__(
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self,
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secret_key: str | bytes | cabc.Iterable[str] | cabc.Iterable[bytes],
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salt: str | bytes | None = b"itsdangerous",
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serializer: t.Any | None = None,
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serializer_kwargs: dict[str, t.Any] | None = None,
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signer: type[Signer] | None = None,
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signer_kwargs: dict[str, t.Any] | None = None,
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fallback_signers: list[
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dict[str, t.Any] | tuple[type[Signer], dict[str, t.Any]] | type[Signer]
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]
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| None = None,
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):
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#: The list of secret keys to try for verifying signatures, from
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#: oldest to newest. The newest (last) key is used for signing.
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#:
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#: This allows a key rotation system to keep a list of allowed
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#: keys and remove expired ones.
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self.secret_keys: list[bytes] = _make_keys_list(secret_key)
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if salt is not None:
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salt = want_bytes(salt)
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# if salt is None then the signer's default is used
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self.salt = salt
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if serializer is None:
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serializer = self.default_serializer
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self.serializer: _PDataSerializer[_TSerialized] = serializer
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self.is_text_serializer: bool = is_text_serializer(serializer)
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if signer is None:
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signer = self.default_signer
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self.signer: type[Signer] = signer
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self.signer_kwargs: dict[str, t.Any] = signer_kwargs or {}
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if fallback_signers is None:
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fallback_signers = list(self.default_fallback_signers)
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self.fallback_signers: list[
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dict[str, t.Any] | tuple[type[Signer], dict[str, t.Any]] | type[Signer]
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] = fallback_signers
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self.serializer_kwargs: dict[str, t.Any] = serializer_kwargs or {}
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@property
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def secret_key(self) -> bytes:
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"""The newest (last) entry in the :attr:`secret_keys` list. This
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is for compatibility from before key rotation support was added.
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"""
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return self.secret_keys[-1]
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def load_payload(
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self, payload: bytes, serializer: _PDataSerializer[t.Any] | None = None
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) -> t.Any:
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"""Loads the encoded object. This function raises
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:class:`.BadPayload` if the payload is not valid. The
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``serializer`` parameter can be used to override the serializer
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stored on the class. The encoded ``payload`` should always be
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bytes.
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"""
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if serializer is None:
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use_serializer = self.serializer
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is_text = self.is_text_serializer
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else:
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use_serializer = serializer
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is_text = is_text_serializer(serializer)
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try:
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if is_text:
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return use_serializer.loads(payload.decode("utf-8")) # type: ignore[arg-type]
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return use_serializer.loads(payload) # type: ignore[arg-type]
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except Exception as e:
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raise BadPayload(
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"Could not load the payload because an exception"
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" occurred on unserializing the data.",
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original_error=e,
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) from e
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def dump_payload(self, obj: t.Any) -> bytes:
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"""Dumps the encoded object. The return value is always bytes.
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If the internal serializer returns text, the value will be
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encoded as UTF-8.
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"""
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return want_bytes(self.serializer.dumps(obj, **self.serializer_kwargs))
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def make_signer(self, salt: str | bytes | None = None) -> Signer:
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"""Creates a new instance of the signer to be used. The default
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implementation uses the :class:`.Signer` base class.
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"""
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if salt is None:
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salt = self.salt
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return self.signer(self.secret_keys, salt=salt, **self.signer_kwargs)
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def iter_unsigners(self, salt: str | bytes | None = None) -> cabc.Iterator[Signer]:
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"""Iterates over all signers to be tried for unsigning. Starts
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with the configured signer, then constructs each signer
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specified in ``fallback_signers``.
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"""
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if salt is None:
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salt = self.salt
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yield self.make_signer(salt)
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for fallback in self.fallback_signers:
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if isinstance(fallback, dict):
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kwargs = fallback
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fallback = self.signer
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elif isinstance(fallback, tuple):
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fallback, kwargs = fallback
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else:
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kwargs = self.signer_kwargs
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for secret_key in self.secret_keys:
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yield fallback(secret_key, salt=salt, **kwargs)
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def dumps(self, obj: t.Any, salt: str | bytes | None = None) -> _TSerialized:
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"""Returns a signed string serialized with the internal
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serializer. The return value can be either a byte or unicode
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string depending on the format of the internal serializer.
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"""
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payload = want_bytes(self.dump_payload(obj))
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rv = self.make_signer(salt).sign(payload)
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if self.is_text_serializer:
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return rv.decode("utf-8") # type: ignore[return-value]
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return rv # type: ignore[return-value]
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def dump(self, obj: t.Any, f: t.IO[t.Any], salt: str | bytes | None = None) -> None:
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"""Like :meth:`dumps` but dumps into a file. The file handle has
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to be compatible with what the internal serializer expects.
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"""
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f.write(self.dumps(obj, salt))
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def loads(
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self, s: str | bytes, salt: str | bytes | None = None, **kwargs: t.Any
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) -> t.Any:
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"""Reverse of :meth:`dumps`. Raises :exc:`.BadSignature` if the
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signature validation fails.
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"""
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s = want_bytes(s)
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last_exception = None
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for signer in self.iter_unsigners(salt):
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try:
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return self.load_payload(signer.unsign(s))
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except BadSignature as err:
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last_exception = err
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raise t.cast(BadSignature, last_exception)
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def load(self, f: t.IO[t.Any], salt: str | bytes | None = None) -> t.Any:
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"""Like :meth:`loads` but loads from a file."""
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return self.loads(f.read(), salt)
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|
|
|
||
|
|
def loads_unsafe(
|
||
|
|
self, s: str | bytes, salt: str | bytes | None = None
|
||
|
|
) -> tuple[bool, t.Any]:
|
||
|
|
"""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: str | bytes,
|
||
|
|
salt: str | bytes | None,
|
||
|
|
load_kwargs: dict[str, t.Any] | None = None,
|
||
|
|
load_payload_kwargs: dict[str, t.Any] | None = None,
|
||
|
|
) -> tuple[bool, t.Any]:
|
||
|
|
"""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[t.Any], salt: str | bytes | None = None
|
||
|
|
) -> tuple[bool, t.Any]:
|
||
|
|
"""Like :meth:`loads_unsafe` but loads from a file.
|
||
|
|
|
||
|
|
.. versionadded:: 0.15
|
||
|
|
"""
|
||
|
|
return self.loads_unsafe(f.read(), salt=salt)
|