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Improve validation of field size limits in events. (#14664)

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reivilibre 2022-12-13 13:19:19 +00:00 committed by GitHub
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commit 62ed877433
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8 changed files with 123 additions and 34 deletions
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1
changelog.d/14664.bugfix Normal file
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@ -0,0 +1 @@
Improve validation of field size limits in events.

2
stubs/synapse/synapse_rust/push.pyi
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@ -45,7 +45,7 @@ class PushRuleEvaluator:
notification_power_levels: Mapping[str, int],
related_events_flattened: Mapping[str, Mapping[str, str]],
related_event_match_enabled: bool,
room_version_feature_flags: list[str],
room_version_feature_flags: Tuple[str, ...],
msc3931_enabled: bool,
): ...
def run(

1
synapse/api/constants.py
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@ -152,6 +152,7 @@ class EduTypes:
class RejectedReason:
AUTH_ERROR: Final = "auth_error"
OVERSIZED_EVENT: Final = "oversized_event"
class RoomCreationPreset:

11
synapse/api/errors.py
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@ -424,8 +424,17 @@ class ResourceLimitError(SynapseError):
class EventSizeError(SynapseError):
"""An error raised when an event is too big."""
def __init__(self, msg: str):
def __init__(self, msg: str, unpersistable: bool):
"""
unpersistable:
if True, the PDU must not be persisted, not even as a rejected PDU
when received over federation.
This is notably true when the entire PDU exceeds the size limit for a PDU,
(as opposed to an individual key's size limit being exceeded).
"""
super().__init__(413, msg, Codes.TOO_LARGE)
self.unpersistable = unpersistable
class LoginError(SynapseError):

32
synapse/api/room_versions.py
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@ -12,7 +12,7 @@
# See the License for the specific language governing permissions and
# limitations under the License.
from typing import Callable, Dict, List, Optional
from typing import Callable, Dict, Optional, Tuple
import attr
@ -103,7 +103,7 @@ class RoomVersion:
# is not enough to mark it "supported": the push rule evaluator also needs to
# support the flag. Unknown flags are ignored by the evaluator, making conditions
# fail if used.
msc3931_push_features: List[str] # values from PushRuleRoomFlag
msc3931_push_features: Tuple[str, ...] # values from PushRuleRoomFlag
class RoomVersions:
@ -124,7 +124,7 @@ class RoomVersions:
msc2716_redactions=False,
msc3787_knock_restricted_join_rule=False,
msc3667_int_only_power_levels=False,
msc3931_push_features=[],
msc3931_push_features=(),
)
V2 = RoomVersion(
"2",
@ -143,7 +143,7 @@ class RoomVersions:
msc2716_redactions=False,
msc3787_knock_restricted_join_rule=False,
msc3667_int_only_power_levels=False,
msc3931_push_features=[],
msc3931_push_features=(),
)
V3 = RoomVersion(
"3",
@ -162,7 +162,7 @@ class RoomVersions:
msc2716_redactions=False,
msc3787_knock_restricted_join_rule=False,
msc3667_int_only_power_levels=False,
msc3931_push_features=[],
msc3931_push_features=(),
)
V4 = RoomVersion(
"4",
@ -181,7 +181,7 @@ class RoomVersions:
msc2716_redactions=False,
msc3787_knock_restricted_join_rule=False,
msc3667_int_only_power_levels=False,
msc3931_push_features=[],
msc3931_push_features=(),
)
V5 = RoomVersion(
"5",
@ -200,7 +200,7 @@ class RoomVersions:
msc2716_redactions=False,
msc3787_knock_restricted_join_rule=False,
msc3667_int_only_power_levels=False,
msc3931_push_features=[],
msc3931_push_features=(),
)
V6 = RoomVersion(
"6",
@ -219,7 +219,7 @@ class RoomVersions:
msc2716_redactions=False,
msc3787_knock_restricted_join_rule=False,
msc3667_int_only_power_levels=False,
msc3931_push_features=[],
msc3931_push_features=(),
)
MSC2176 = RoomVersion(
"org.matrix.msc2176",
@ -238,7 +238,7 @@ class RoomVersions:
msc2716_redactions=False,
msc3787_knock_restricted_join_rule=False,
msc3667_int_only_power_levels=False,
msc3931_push_features=[],
msc3931_push_features=(),
)
V7 = RoomVersion(
"7",
@ -257,7 +257,7 @@ class RoomVersions:
msc2716_redactions=False,
msc3787_knock_restricted_join_rule=False,
msc3667_int_only_power_levels=False,
msc3931_push_features=[],
msc3931_push_features=(),
)
V8 = RoomVersion(
"8",
@ -276,7 +276,7 @@ class RoomVersions:
msc2716_redactions=False,
msc3787_knock_restricted_join_rule=False,
msc3667_int_only_power_levels=False,
msc3931_push_features=[],
msc3931_push_features=(),
)
V9 = RoomVersion(
"9",
@ -295,7 +295,7 @@ class RoomVersions:
msc2716_redactions=False,
msc3787_knock_restricted_join_rule=False,
msc3667_int_only_power_levels=False,
msc3931_push_features=[],
msc3931_push_features=(),
)
MSC3787 = RoomVersion(
"org.matrix.msc3787",
@ -314,7 +314,7 @@ class RoomVersions:
msc2716_redactions=False,
msc3787_knock_restricted_join_rule=True,
msc3667_int_only_power_levels=False,
msc3931_push_features=[],
msc3931_push_features=(),
)
V10 = RoomVersion(
"10",
@ -333,7 +333,7 @@ class RoomVersions:
msc2716_redactions=False,
msc3787_knock_restricted_join_rule=True,
msc3667_int_only_power_levels=True,
msc3931_push_features=[],
msc3931_push_features=(),
)
MSC2716v4 = RoomVersion(
"org.matrix.msc2716v4",
@ -352,7 +352,7 @@ class RoomVersions:
msc2716_redactions=True,
msc3787_knock_restricted_join_rule=False,
msc3667_int_only_power_levels=False,
msc3931_push_features=[],
msc3931_push_features=(),
)
MSC1767v10 = RoomVersion(
# MSC1767 (Extensible Events) based on room version "10"
@ -372,7 +372,7 @@ class RoomVersions:
msc2716_redactions=False,
msc3787_knock_restricted_join_rule=True,
msc3667_int_only_power_levels=True,
msc3931_push_features=[PushRuleRoomFlag.EXTENSIBLE_EVENTS],
msc3931_push_features=(PushRuleRoomFlag.EXTENSIBLE_EVENTS,),
)

84
synapse/event_auth.py
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@ -52,6 +52,7 @@ from synapse.api.room_versions import (
KNOWN_ROOM_VERSIONS,
EventFormatVersions,
RoomVersion,
RoomVersions,
)
from synapse.storage.databases.main.events_worker import EventRedactBehaviour
from synapse.types import MutableStateMap, StateMap, UserID, get_domain_from_id
@ -341,19 +342,80 @@ def check_state_dependent_auth_rules(
logger.debug("Allowing! %s", event)
# Set of room versions where Synapse did not apply event key size limits
# in bytes, but rather in codepoints.
# In these room versions, we are more lenient with event size validation.
LENIENT_EVENT_BYTE_LIMITS_ROOM_VERSIONS = {
RoomVersions.V1,
RoomVersions.V2,
RoomVersions.V3,
RoomVersions.V4,
RoomVersions.V5,
RoomVersions.V6,
RoomVersions.MSC2176,
RoomVersions.V7,
RoomVersions.V8,
RoomVersions.V9,
RoomVersions.MSC3787,
RoomVersions.V10,
RoomVersions.MSC2716v4,
RoomVersions.MSC1767v10,
}
def _check_size_limits(event: "EventBase") -> None:
if len(event.user_id) > 255:
raise EventSizeError("'user_id' too large")
if len(event.room_id) > 255:
raise EventSizeError("'room_id' too large")
if event.is_state() and len(event.state_key) > 255:
raise EventSizeError("'state_key' too large")
if len(event.type) > 255:
raise EventSizeError("'type' too large")
if len(event.event_id) > 255:
raise EventSizeError("'event_id' too large")
"""
Checks the size limits in a PDU.
The entire size limit of the PDU is checked first.
Then the size of fields is checked, first in codepoints and then in bytes.
The codepoint size limits are only for Synapse compatibility.
Raises:
EventSizeError:
when a size limit has been violated.
unpersistable=True if Synapse never would have accepted the event and
the PDU must NOT be persisted.
unpersistable=False if a prior version of Synapse would have accepted the
event and so the PDU must be persisted as rejected to avoid
breaking the room.
"""
# Whole PDU check
if len(encode_canonical_json(event.get_pdu_json())) > MAX_PDU_SIZE:
raise EventSizeError("event too large")
raise EventSizeError("event too large", unpersistable=True)
# Codepoint size check: Synapse always enforced these limits, so apply
# them strictly.
if len(event.user_id) > 255:
raise EventSizeError("'user_id' too large", unpersistable=True)
if len(event.room_id) > 255:
raise EventSizeError("'room_id' too large", unpersistable=True)
if event.is_state() and len(event.state_key) > 255:
raise EventSizeError("'state_key' too large", unpersistable=True)
if len(event.type) > 255:
raise EventSizeError("'type' too large", unpersistable=True)
if len(event.event_id) > 255:
raise EventSizeError("'event_id' too large", unpersistable=True)
strict_byte_limits = (
event.room_version not in LENIENT_EVENT_BYTE_LIMITS_ROOM_VERSIONS
)
# Byte size check: if these fail, then be lenient to avoid breaking rooms.
if len(event.user_id.encode("utf-8")) > 255:
raise EventSizeError("'user_id' too large", unpersistable=strict_byte_limits)
if len(event.room_id.encode("utf-8")) > 255:
raise EventSizeError("'room_id' too large", unpersistable=strict_byte_limits)
if event.is_state() and len(event.state_key.encode("utf-8")) > 255:
raise EventSizeError("'state_key' too large", unpersistable=strict_byte_limits)
if len(event.type.encode("utf-8")) > 255:
raise EventSizeError("'type' too large", unpersistable=strict_byte_limits)
if len(event.event_id.encode("utf-8")) > 255:
raise EventSizeError("'event_id' too large", unpersistable=strict_byte_limits)
def _check_create(event: "EventBase") -> None:

20
synapse/handlers/federation_event.py
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@ -43,6 +43,7 @@ from synapse.api.constants import (
from synapse.api.errors import (
AuthError,
Codes,
EventSizeError,
FederationError,
FederationPullAttemptBackoffError,
HttpResponseException,
@ -1736,6 +1737,15 @@ class FederationEventHandler:
except AuthError as e:
logger.warning("Rejecting %r because %s", event, e)
context.rejected = RejectedReason.AUTH_ERROR
except EventSizeError as e:
if e.unpersistable:
# This event is completely unpersistable.
raise e
# Otherwise, we are somewhat lenient and just persist the event
# as rejected, for moderate compatibility with older Synapse
# versions.
logger.warning("While validating received event %r: %s", event, e)
context.rejected = RejectedReason.OVERSIZED_EVENT
events_and_contexts_to_persist.append((event, context))
@ -1781,6 +1791,16 @@ class FederationEventHandler:
# TODO: use a different rejected reason here?
context.rejected = RejectedReason.AUTH_ERROR
return
except EventSizeError as e:
if e.unpersistable:
# This event is completely unpersistable.
raise e
# Otherwise, we are somewhat lenient and just persist the event
# as rejected, for moderate compatibility with older Synapse
# versions.
logger.warning("While validating received event %r: %s", event, e)
context.rejected = RejectedReason.OVERSIZED_EVENT
return
# next, check that we have all of the event's auth events.
#

6
synapse/push/bulk_push_rule_evaluator.py
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@ -342,10 +342,6 @@ class BulkPushRuleEvaluator:
for user_id, level in notification_levels.items():
notification_levels[user_id] = int(level)
room_version_features = event.room_version.msc3931_push_features
if not room_version_features:
room_version_features = []
evaluator = PushRuleEvaluator(
_flatten_dict(event, room_version=event.room_version),
room_member_count,
@ -353,7 +349,7 @@ class BulkPushRuleEvaluator:
notification_levels,
related_events,
self._related_event_match_enabled,
room_version_features,
event.room_version.msc3931_push_features,
self.hs.config.experimental.msc1767_enabled, # MSC3931 flag
)