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# Copyright 2019 PrivateStorage.io, LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""
A Tahoe-LAFS RIStorageServer-alike which authorizes writes and lease
updates using a per-call token.
This is the server part of a storage access protocol. The client part is
implemented in ``_storage_client.py``.
import attr
from attr.validators import (
provides,
)
)
from foolscap.constraint import (
ByteStringConstraint,
)
from foolscap.api import (
ListOf,
from foolscap.ipb import (
IReferenceable,
IRemotelyCallable,
)
from foolscap.remoteinterface import (
RemoteMethodSchema,
RemoteInterface,
)
from allmydata.interfaces import (
RIStorageServer,
)
# The Foolscap convention seems to be to try to constrain inputs to valid
# values. So we'll try to limit the number of tokens a client can supply.
# Foolscap may be moving away from this so we may eventually drop this as
# well. Though it may still make sense on a non-Foolscap protocol (eg HTTP)
# which Tahoe-LAFS may eventually support.
#
# In any case, for now, pick some fairly arbitrary value. I am deliberately
# picking a small number here and expect to have to raise. However, ideally,
# a client could accomplish a lot with a few tokens while also not wasting a
# lot of value.
# This is the length of a serialized PrivacyPass pass (there's a lot of
# confusion between "tokens" and "passes" here, sadly).
# Take those values and turn them into the appropriate Foolscap constraint
# objects. Foolscap seems to have a convention of representing these as
# CamelCase module-level values so I replicate that here.
Token = ByteStringConstraint(maxLength=TOKEN_LENGTH, minLength=TOKEN_LENGTH)
TokenList = ListOf(Token, maxLength=MAXIMUM_TOKENS_PER_CALL)
def add_tokens(schema):
"""
Add a ``tokens`` parameter to the given method schema.
:param foolscap.remoteinterface.RemoteMethodSchema schema: An existing
method schema to modify.
:return foolscap.remoteinterface.RemoteMethodSchema: A schema like
``schema`` but with one additional required argument.
"""
return add_arguments(schema, [(b"tokens", TokenList)])
def add_arguments(schema, kwargs):
"""
Create a new schema like ``schema`` but with the arguments given by
``kwargs`` prepended to the signature.
:param foolscap.remoteinterface.RemoteMethodSchema schema: The existing
schema.
:param list[(bytes, foolscap.IConstraint)] kwargs: The arguments to
prepend to the signature of ``schema``.
:return foolscap.remoteinterface.RemoteMethodSchema: The new schema
object.
"""
new_kwargs = dict(schema.argConstraints)
new_kwargs.update(kwargs)
modified_schema = RemoteMethodSchema(**new_kwargs)
# Initialized from **new_kwargs, RemoteMethodSchema.argumentNames is in
# some arbitrary, probably-incorrect order. This breaks user code which
# tries to use positional arguments. Put them back in the order they were
# in originally (in the input ``schema``), prepended with the newly added
# arguments.
modified_schema.argumentNames = (
list(argName for (argName, _) in kwargs) +
# The original arguments in the original order
schema.argumentNames
)
return modified_schema
class RITokenAuthorizedStorageServer(RemoteInterface):
"""
An object which can store and retrieve shares, subject to token-based
authorization.
This is much the same as ``allmydata.interfaces.RIStorageServer`` but
several of its methods take an additional ``tokens`` parameter. Clients
are expected to supply suitable tokens and only after the tokens have been
validated is service provided.
"""
__remote_name__ = (
"RITokenAuthorizedStorageServer.tahoe.privatestorage.io"
)
get_version = RIStorageServer["get_version"]
allocate_buckets = add_tokens(RIStorageServer["allocate_buckets"])
add_lease = add_tokens(RIStorageServer["add_lease"])
renew_lease = add_tokens(RIStorageServer["renew_lease"])
get_buckets = RIStorageServer["get_buckets"]
slot_readv = RIStorageServer["slot_readv"]
slot_testv_and_readv_and_writev = add_tokens(
RIStorageServer["slot_testv_and_readv_and_writev"],
)
advise_corrupt_share = RIStorageServer["advise_corrupt_share"]
@implementer_only(RITokenAuthorizedStorageServer, IReferenceable, IRemotelyCallable)
# It would be great to use `frozen=True` (value-based hashing) instead of
# `cmp=False` (identity based hashing) but Referenceable wants to set some
# attributes on self and it's hard to avoid that.
@attr.s(cmp=False)
class ZKAPAuthorizerStorageServer(Referenceable):
"""
A class which wraps an ``RIStorageServer`` to insert token validity checks
before allowing certain functionality.
"""
_original = attr.ib(validator=provides(RIStorageServer))
def _validate_tokens(self, tokens):
"""
Check that all of the given tokens are valid.
:raise InvalidToken: If any token in ``tokens`` is not valid.
:return NoneType: If all of the tokens in ``tokens`` are valid.
:note: This is yet to be implemented so it always returns ``None``.
"""
return None
"""
Pass through without token check to allow clients to learn about our
version and configuration in case it helps them decide how to behave.
"""
return self._original.remote_get_version()
def remote_allocate_buckets(self, tokens, *a, **kw):
"""
Pass through after a token check to ensure that clients can only allocate
storage for immutable shares if they present valid tokens.
"""
return self._original.remote_allocate_buckets(*a, **kw)
def remote_get_buckets(self, storage_index):
"""
Pass through without token check to let clients read immutable shares as
long as those shares exist.
"""
return self._original.remote_get_buckets(storage_index)
def remote_add_lease(self, tokens, *a, **kw):
"""
Pass through after a token check to ensure clients can only extend the
duration of share storage if they present valid tokens.
"""
return self._original.remote_add_lease(*a, **kw)
"""
Pass through after a token check to ensure clients can only extend the
duration of share storage if they present valid tokens.
"""
self._validate_tokens(tokens)
return self._original.remote_renew_lease(*a, **kw)
def remote_advise_corrupt_share(self, *a, **kw):
"""
Pass through without a token check to let clients inform us of possible
issues with the system without incurring any cost to themselves.
"""
return self._original.remote_advise_corrupt_share(*a, **kw)
def remote_slot_testv_and_readv_and_writev(self, tokens, *a, **kw):
"""
Pass through after a token check to ensure clients can only allocate
storage for mutable shares if they present valid tokens.
:note: This method can be used both to allocate storage and to rewrite
data in already-allocated storage. These cases may not be the
same from the perspective of token validation.
"""
self._validate_tokens(tokens)
# Skip over the remotely exposed method and jump to the underlying
# implementation which accepts one additional parameter that we know
# about (and don't expose over the network): renew_leases. We always
# pass False for this because we want to manage leases completely
# separately from writes.
kw["renew_leases"] = False
return self._original.slot_testv_and_readv_and_writev(*a, **kw)
def remote_slot_readv(self, *a, **kw):
"""
Pass through without a token check to let clients read mutable shares as
long as those shares exist.
"""
return self._original.remote_slot_readv(*a, **kw)
# I don't understand why this is required.
# ZKAPAuthorizerStorageServer is-a Referenceable. It seems like
# the built in adapter should take care of this case.
from twisted.python.components import (
registerAdapter,
)
from foolscap.referenceable import (
ReferenceableSlicer,
)
from foolscap.ipb import (
ISlicer,
)
registerAdapter(ReferenceableSlicer, ZKAPAuthorizerStorageServer, ISlicer)