MatrixSynapse/synapse/events/validator.py

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# Copyright 2014-2016 OpenMarket Ltd
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#
# 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.
import collections.abc
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from typing import Iterable, Type, Union, cast
import jsonschema
from synapse.api.constants import MAX_ALIAS_LENGTH, EventTypes, Membership
from synapse.api.errors import Codes, SynapseError
from synapse.api.room_versions import EventFormatVersions
from synapse.config.homeserver import HomeServerConfig
from synapse.events import EventBase
from synapse.events.builder import EventBuilder
from synapse.events.utils import (
CANONICALJSON_MAX_INT,
CANONICALJSON_MIN_INT,
validate_canonicaljson,
)
from synapse.federation.federation_server import server_matches_acl_event
from synapse.types import EventID, JsonDict, RoomID, UserID
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class EventValidator:
def validate_new(self, event: EventBase, config: HomeServerConfig) -> None:
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"""Validates the event has roughly the right format
Suitable for checking a locally-created event. It has stricter checks than
is appropriate for an event received over federation (for which, see
event_auth.validate_event_for_room_version)
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Args:
event: The event to validate.
config: The homeserver's configuration.
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"""
self.validate_builder(event)
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if event.format_version == EventFormatVersions.ROOM_V1_V2:
EventID.from_string(event.event_id)
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required = [
"auth_events",
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"content",
"hashes",
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"origin",
"prev_events",
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"sender",
"type",
]
for k in required:
if k not in event:
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raise SynapseError(400, "Event does not have key %s" % (k,))
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# Check that the following keys have string values
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event_strings = ["origin"]
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for s in event_strings:
if not isinstance(getattr(event, s), str):
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raise SynapseError(400, "'%s' not a string type" % (s,))
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# Depending on the room version, ensure the data is spec compliant JSON.
if event.room_version.strict_canonicaljson:
# Note that only the client controlled portion of the event is
# checked, since we trust the portions of the event we created.
validate_canonicaljson(event.content)
if event.type == EventTypes.Aliases:
if "aliases" in event.content:
for alias in event.content["aliases"]:
if len(alias) > MAX_ALIAS_LENGTH:
raise SynapseError(
400,
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(
"Can't create aliases longer than"
" %d characters" % (MAX_ALIAS_LENGTH,)
),
Codes.INVALID_PARAM,
)
if event.type == EventTypes.Retention:
self._validate_retention(event)
if event.type == EventTypes.ServerACL:
if not server_matches_acl_event(config.server.server_name, event):
raise SynapseError(
400, "Can't create an ACL event that denies the local server"
)
if event.type == EventTypes.PowerLevels:
try:
jsonschema.validate(
instance=event.content,
schema=POWER_LEVELS_SCHEMA,
cls=plValidator,
)
except jsonschema.ValidationError as e:
if e.path:
# example: "users_default": '0' is not of type 'integer'
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# cast safety: path entries can be integers, if we fail to validate
# items in an array. However the POWER_LEVELS_SCHEMA doesn't expect
# to see any arrays.
message = (
'"' + cast(str, e.path[-1]) + '": ' + e.message # noqa: B306
)
# jsonschema.ValidationError.message is a valid attribute
else:
# example: '0' is not of type 'integer'
message = e.message # noqa: B306
# jsonschema.ValidationError.message is a valid attribute
raise SynapseError(
code=400,
msg=message,
errcode=Codes.BAD_JSON,
)
def _validate_retention(self, event: EventBase) -> None:
"""Checks that an event that defines the retention policy for a room respects the
format enforced by the spec.
Args:
event: The event to validate.
"""
if not event.is_state():
raise SynapseError(code=400, msg="must be a state event")
min_lifetime = event.content.get("min_lifetime")
max_lifetime = event.content.get("max_lifetime")
if min_lifetime is not None:
if type(min_lifetime) is not int:
raise SynapseError(
code=400,
msg="'min_lifetime' must be an integer",
errcode=Codes.BAD_JSON,
)
if max_lifetime is not None:
if type(max_lifetime) is not int:
raise SynapseError(
code=400,
msg="'max_lifetime' must be an integer",
errcode=Codes.BAD_JSON,
)
if (
min_lifetime is not None
and max_lifetime is not None
and min_lifetime > max_lifetime
):
raise SynapseError(
code=400,
msg="'min_lifetime' can't be greater than 'max_lifetime",
errcode=Codes.BAD_JSON,
)
def validate_builder(self, event: Union[EventBase, EventBuilder]) -> None:
"""Validates that the builder/event has roughly the right format. Only
checks values that we expect a proto event to have, rather than all the
fields an event would have
"""
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strings = ["room_id", "sender", "type"]
if hasattr(event, "state_key"):
strings.append("state_key")
for s in strings:
if not isinstance(getattr(event, s), str):
raise SynapseError(400, "Not '%s' a string type" % (s,))
RoomID.from_string(event.room_id)
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UserID.from_string(event.sender)
if event.type == EventTypes.Message:
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strings = ["body", "msgtype"]
self._ensure_strings(event.content, strings)
elif event.type == EventTypes.Topic:
self._ensure_strings(event.content, ["topic"])
self._ensure_state_event(event)
elif event.type == EventTypes.Name:
self._ensure_strings(event.content, ["name"])
self._ensure_state_event(event)
elif event.type == EventTypes.Member:
if "membership" not in event.content:
raise SynapseError(400, "Content has not membership key")
if event.content["membership"] not in Membership.LIST:
raise SynapseError(400, "Invalid membership key")
self._ensure_state_event(event)
elif event.type == EventTypes.Tombstone:
if "replacement_room" not in event.content:
raise SynapseError(400, "Content has no replacement_room key")
if event.content["replacement_room"] == event.room_id:
raise SynapseError(
400, "Tombstone cannot reference the room it was sent in"
)
self._ensure_state_event(event)
def _ensure_strings(self, d: JsonDict, keys: Iterable[str]) -> None:
for s in keys:
if s not in d:
raise SynapseError(400, "'%s' not in content" % (s,))
if not isinstance(d[s], str):
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raise SynapseError(400, "'%s' not a string type" % (s,))
def _ensure_state_event(self, event: Union[EventBase, EventBuilder]) -> None:
if not event.is_state():
raise SynapseError(400, "'%s' must be state events" % (event.type,))
POWER_LEVELS_SCHEMA = {
"type": "object",
"properties": {
"ban": {"$ref": "#/definitions/int"},
"events": {"$ref": "#/definitions/objectOfInts"},
"events_default": {"$ref": "#/definitions/int"},
"invite": {"$ref": "#/definitions/int"},
"kick": {"$ref": "#/definitions/int"},
"notifications": {"$ref": "#/definitions/objectOfInts"},
"redact": {"$ref": "#/definitions/int"},
"state_default": {"$ref": "#/definitions/int"},
"users": {"$ref": "#/definitions/objectOfInts"},
"users_default": {"$ref": "#/definitions/int"},
},
"definitions": {
"int": {
"type": "integer",
"minimum": CANONICALJSON_MIN_INT,
"maximum": CANONICALJSON_MAX_INT,
},
"objectOfInts": {
"type": "object",
"additionalProperties": {"$ref": "#/definitions/int"},
},
},
}
# This could return something newer than Draft 7, but that's the current "latest"
# validator.
def _create_power_level_validator() -> Type[jsonschema.Draft7Validator]:
validator = jsonschema.validators.validator_for(POWER_LEVELS_SCHEMA)
# by default jsonschema does not consider a frozendict to be an object so
# we need to use a custom type checker
# https://python-jsonschema.readthedocs.io/en/stable/validate/?highlight=object#validating-with-additional-types
type_checker = validator.TYPE_CHECKER.redefine(
"object", lambda checker, thing: isinstance(thing, collections.abc.Mapping)
)
return jsonschema.validators.extend(validator, type_checker=type_checker)
plValidator = _create_power_level_validator()