9bbeb35c08
Fixed an issue that prevented the password reset tokens from working. Added email templates for password reset success and new account creation. Added more dynamic email template support.
257 lines
9.1 KiB
Python
257 lines
9.1 KiB
Python
import hashlib
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import hmac
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import typing as _t
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from .encoding import _base64_alphabet
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from .encoding import base64_decode
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from .encoding import base64_encode
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from .encoding import want_bytes
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from .exc import BadSignature
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_t_str_bytes = _t.Union[str, bytes]
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_t_opt_str_bytes = _t.Optional[_t_str_bytes]
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_t_secret_key = _t.Union[_t.Iterable[_t_str_bytes], _t_str_bytes]
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class SigningAlgorithm:
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"""Subclasses must implement :meth:`get_signature` to provide
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signature generation functionality.
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"""
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def get_signature(self, key: bytes, value: bytes) -> bytes:
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"""Returns the signature for the given key and value."""
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raise NotImplementedError()
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def verify_signature(self, key: bytes, value: bytes, sig: bytes) -> bool:
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"""Verifies the given signature matches the expected
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signature.
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"""
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return hmac.compare_digest(sig, self.get_signature(key, value))
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class NoneAlgorithm(SigningAlgorithm):
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"""Provides an algorithm that does not perform any signing and
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returns an empty signature.
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"""
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def get_signature(self, key: bytes, value: bytes) -> bytes:
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return b""
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class HMACAlgorithm(SigningAlgorithm):
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"""Provides signature generation using HMACs."""
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#: The digest method to use with the MAC algorithm. This defaults to
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#: SHA1, but can be changed to any other function in the hashlib
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#: module.
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default_digest_method: _t.Any = staticmethod(hashlib.sha1)
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def __init__(self, digest_method: _t.Any = None):
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if digest_method is None:
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digest_method = self.default_digest_method
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self.digest_method: _t.Any = digest_method
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def get_signature(self, key: bytes, value: bytes) -> bytes:
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mac = hmac.new(key, msg=value, digestmod=self.digest_method)
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return mac.digest()
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def _make_keys_list(secret_key: _t_secret_key) -> _t.List[bytes]:
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if isinstance(secret_key, (str, bytes)):
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return [want_bytes(secret_key)]
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return [want_bytes(s) for s in secret_key]
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class Signer:
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"""A signer securely signs bytes, then unsigns them to verify that
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the value hasn't been changed.
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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 sep: Separator between the signature and value.
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:param key_derivation: How to derive the signing key from the secret
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key and salt. Possible values are ``concat``, ``django-concat``,
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or ``hmac``. Defaults to :attr:`default_key_derivation`, which
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defaults to ``django-concat``.
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:param digest_method: Hash function to use when generating the HMAC
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signature. Defaults to :attr:`default_digest_method`, which
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defaults to :func:`hashlib.sha1`. Note that the security of the
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hash alone doesn't apply when used intermediately in HMAC.
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:param algorithm: A :class:`SigningAlgorithm` instance to use
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instead of building a default :class:`HMACAlgorithm` with the
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``digest_method``.
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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:: 0.18
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``algorithm`` was added as an argument to the class constructor.
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.. versionchanged:: 0.14
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``key_derivation`` and ``digest_method`` were added as arguments
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to the class constructor.
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"""
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#: The default digest method to use for the signer. The default is
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#: :func:`hashlib.sha1`, but can be changed to any :mod:`hashlib` or
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#: compatible object. Note that the security of the hash alone
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#: doesn't apply when used intermediately in HMAC.
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#:
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#: .. versionadded:: 0.14
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default_digest_method: _t.Any = staticmethod(hashlib.sha1)
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#: The default scheme to use to derive the signing key from the
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#: secret key and salt. The default is ``django-concat``. Possible
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#: values are ``concat``, ``django-concat``, and ``hmac``.
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#:
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#: .. versionadded:: 0.14
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default_key_derivation: str = "django-concat"
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def __init__(
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self,
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secret_key: _t_secret_key,
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salt: _t_opt_str_bytes = b"itsdangerous.Signer",
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sep: _t_str_bytes = b".",
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key_derivation: _t.Optional[str] = None,
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digest_method: _t.Optional[_t.Any] = None,
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algorithm: _t.Optional[SigningAlgorithm] = 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: _t.List[bytes] = _make_keys_list(secret_key)
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self.sep: bytes = want_bytes(sep)
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if self.sep in _base64_alphabet:
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raise ValueError(
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"The given separator cannot be used because it may be"
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" contained in the signature itself. ASCII letters,"
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" digits, and '-_=' must not be used."
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)
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if salt is not None:
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salt = want_bytes(salt)
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else:
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salt = b"itsdangerous.Signer"
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self.salt = salt
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if key_derivation is None:
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key_derivation = self.default_key_derivation
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self.key_derivation: str = key_derivation
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if digest_method is None:
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digest_method = self.default_digest_method
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self.digest_method: _t.Any = digest_method
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if algorithm is None:
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algorithm = HMACAlgorithm(self.digest_method)
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self.algorithm: SigningAlgorithm = algorithm
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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 derive_key(self, secret_key: _t_opt_str_bytes = None) -> bytes:
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"""This method is called to derive the key. The default key
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derivation choices can be overridden here. Key derivation is not
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intended to be used as a security method to make a complex key
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out of a short password. Instead you should use large random
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secret keys.
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:param secret_key: A specific secret key to derive from.
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Defaults to the last item in :attr:`secret_keys`.
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.. versionchanged:: 2.0
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Added the ``secret_key`` parameter.
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"""
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if secret_key is None:
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secret_key = self.secret_keys[-1]
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else:
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secret_key = want_bytes(secret_key)
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if self.key_derivation == "concat":
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return _t.cast(bytes, self.digest_method(self.salt + secret_key).digest())
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elif self.key_derivation == "django-concat":
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return _t.cast(
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bytes, self.digest_method(self.salt + b"signer" + secret_key).digest()
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)
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elif self.key_derivation == "hmac":
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mac = hmac.new(secret_key, digestmod=self.digest_method)
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mac.update(self.salt)
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return mac.digest()
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elif self.key_derivation == "none":
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return secret_key
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else:
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raise TypeError("Unknown key derivation method")
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def get_signature(self, value: _t_str_bytes) -> bytes:
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"""Returns the signature for the given value."""
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value = want_bytes(value)
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key = self.derive_key()
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sig = self.algorithm.get_signature(key, value)
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return base64_encode(sig)
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def sign(self, value: _t_str_bytes) -> bytes:
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"""Signs the given string."""
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value = want_bytes(value)
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return value + self.sep + self.get_signature(value)
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def verify_signature(self, value: _t_str_bytes, sig: _t_str_bytes) -> bool:
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"""Verifies the signature for the given value."""
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try:
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sig = base64_decode(sig)
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except Exception:
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return False
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value = want_bytes(value)
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for secret_key in reversed(self.secret_keys):
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key = self.derive_key(secret_key)
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if self.algorithm.verify_signature(key, value, sig):
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return True
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return False
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def unsign(self, signed_value: _t_str_bytes) -> bytes:
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"""Unsigns the given string."""
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signed_value = want_bytes(signed_value)
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if self.sep not in signed_value:
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raise BadSignature(f"No {self.sep!r} found in value")
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value, sig = signed_value.rsplit(self.sep, 1)
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if self.verify_signature(value, sig):
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return value
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raise BadSignature(f"Signature {sig!r} does not match", payload=value)
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def validate(self, signed_value: _t_str_bytes) -> bool:
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"""Only validates the given signed value. Returns ``True`` if
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the signature exists and is valid.
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"""
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try:
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self.unsign(signed_value)
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return True
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except BadSignature:
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return False
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