**Background**
User groups are expected to comply with the DAG constraint for the
many-to-many inter-group membership. The check for this constraint has
to be performed recursively so that we can find all direct and indirect
subgroups of the user group to be added.
This kind of check is vulnerable to phantom reads which is possible at
the default read committed isolation level because we cannot guarantee
that the check is still valid when we are adding the subgroups to the
user group.
**Solution**
To avoid having another transaction concurrently update one of the
to-be-subgroup after the recursive check is done, and before the subgroup
is added, we use SELECT FOR UPDATE to lock the user group rows.
The lock needs to be acquired before a group membership change is about
to occur before any check has been conducted.
Suppose that we are adding subgroup B to supergroup A, the locking protocol
is specified as follows:
1. Acquire a lock for B and all its direct and indirect subgroups.
2. Acquire a lock for A.
For the removal of user groups, we acquire a lock for the user group to
be removed with all its direct and indirect subgroups. This is the special
case A=B, which is still complaint with the protocol.
**Error handling**
We currently rely on Postgres' deadlock detection to abort transactions
and show an error for the users. In the future, we might need some
recovery mechanism or at least better error handling.
**Notes**
An important note is that we need to reuse the recursive CTE query that
finds the direct and indirect subgroups when applying the lock on the
rows. And the lock needs to be acquired the same way for the addition and
removal of direct subgroups.
User membership change (as opposed to user group membership) is not
affected. Read-only queries aren't either. The locks only protect
critical regions where the user group dependency graph might violate
the DAG constraint, where users are not participating.
**Testing**
We implement a transaction test case targeting some typical scenarios
when an internal server error is expected to happen (this means that the
user group view makes the correct decision to abort the transaction when
something goes wrong with locks).
To achieve this, we add a development view intended only for unit tests.
It has a global BARRIER that can be shared across threads, so that we
can synchronize them to consistently reproduce certain potential race
conditions prevented by the database locks.
The transaction test case lanuches pairs of threads initiating possibly
conflicting requests at the same time. The tests are set up such that exactly N
of them are expected to succeed with a certain error message (while we don't
know each one).
**Security notes**
get_recursive_subgroups_for_groups will no longer fetch user groups from
other realms. As a result, trying to add/remove a subgroup from another
realm results in a UserGroup not found error response.
We also implement subgroup-specific checks in has_user_group_access to
keep permission managing in a single place. Do note that the API
currently don't have a way to violate that check because we are only
checking the realm ID now.
We want to make the callers be more explicit about the use of the
user group being accessed, so that the later implemented database lock
can be benefited from the visibility.
This migration applies under the assumption that extra_data_json has
been populated for all existing and coming audit log entries.
- This removes the manual conversions back and forth for extra_data
throughout the codebase including the orjson.loads(), orjson.dumps(),
and str() calls.
- The custom handler used for converting Decimal is removed since
DjangoJSONEncoder handles that for extra_data.
- We remove None-checks for extra_data because it is now no longer
nullable.
- Meanwhile, we want the bouncer to support processing RealmAuditLog entries for
remote servers before and after the JSONField migration on extra_data.
- Since now extra_data should always be a dict for the newer remote
server, which is now migrated, the test cases are updated to create
RealmAuditLog objects by passing a dict for extra_data before
sending over the analytics data. Note that while JSONField allows for
non-dict values, a proper remote server always passes a dict for
extra_data.
- We still test out the legacy extra_data format because not all
remote servers have migrated to use JSONField extra_data.
This verifies that support for extra_data being a string or None has not
been dropped.
Co-authored-by: Siddharth Asthana <siddharthasthana31@gmail.com>
Signed-off-by: Zixuan James Li <p359101898@gmail.com>
Earlier the API endpoints related to user_group accepts and returns a
field `can_mention_group_id` which represents the ID
of user_group whose members can mention the group.
This commit renames this field to `can_mention_group`.
Translators benefit from the extra information in the field names, and
need the reordering freedom that isn’t available with multiple
positional fields.
Signed-off-by: Anders Kaseorg <anders@zulip.com>
This add audit log entries when any group based setting of a user group
is updated. We store both the old and new values in extra_data, along
with the name of that setting. Entries populated during user group creation
are hardcoded to track "can_mention_group".
Potentially we can adjust "set_defaults_for_group_settings" so that it
populates realm audit logs with it, but that is out of scope for this change.
We use an atomic transaction so that the audit logs are committed
together with the updates.
Signed-off-by: Zixuan James Li <p359101898@gmail.com>
This add audit log entries when the name or description of a user group
is updated. We store both the old and new values in extra_data. We wrap
the functions inside an atomic transaction so that the audit logs and
the updates are committed together.
Signed-off-by: Zixuan James Li <p359101898@gmail.com>
This is mostly the same as tracking subgroup changes, except that now
modified_user_group is the subgroup.
Signed-off-by: Zixuan James Li <p359101898@gmail.com>
It's worth noting that instead of adding another field to the
RealmAuditLog model, we store the modified subgroup ids in extra_data as
a JSON encoded dict with the key "subgroup_ids". We don't create audit
log entries for supergroup changes at this point.
Signed-off-by: Zixuan James Li <p359101898@gmail.com>
This also add audit log entries during user creation and role change,
because we modify system group memberships there.
Signed-off-by: Zixuan James Li <p359101898@gmail.com>
We also create RealmAuditLog entries for the initial memberships that
get added along with the creation of a UserGroup. System user groups are
not created with members so no audit logs are populated for that.
Signed-off-by: Zixuan James Li <p359101898@gmail.com>
This commit adds code to include can_mention_group_id field to
UserGroup objects passed with response of various endpoints
including "/register" endpoint and also in the group object
send with user group creation event.
Fixes a part of #25927.
django-stubs 4.2.1 gives transaction.on_commit a more accurate type
annotation, but this exposed that mypy can’t handle the lambda default
parameters that we use to recapture loop variables such as
for stream_id in public_stream_ids:
peer_user_ids = …
event = …
transaction.on_commit(
lambda event=event, peer_user_ids=peer_user_ids: send_event(
realm, event, peer_user_ids
)
)
https://github.com/python/mypy/issues/15459
A workaround that mypy accepts is
transaction.on_commit(
(
lambda event, peer_user_ids: lambda: send_event(
realm, event, peer_user_ids
)
)(event, peer_user_ids)
)
But that’s kind of ugly and potentially error-prone, so let’s make a
helper function for this very common pattern.
send_event_on_commit(realm, event, peer_user_ids)
Signed-off-by: Anders Kaseorg <anders@zulip.com>
To avoid people calling "create_user_group" instead of
"check_add_user_group", we rename it to make its purpose clearer.
Signed-off-by: Zixuan James Li <p359101898@gmail.com>
"check_add_user_group" is a safer helper function than
"create_user_group" to use when creating user_groups. It does
error handling and notify the client with the appropriate event.
Note that the populate_db command still uses "create_user_group"
because we do not need to enqueue events at that point.
Signed-off-by: Zixuan James Li <p359101898@gmail.com>
Since this function creates a new user group into the database,
it is more appropriate to have it not as a generic "lib" function
but as an "action".
Signed-off-by: Zixuan James Li <p359101898@gmail.com>
We now use MEMBERS_GROUP_NAME instead of writing
the actual group name at multiple places, so that we
can have all the group names coded at one place only.
We now use FULL_MEMBERS_GROUP_NAME instead of
writing the actual full members system group
name at multiple places, so that we can have
all the group names coded at one place only.
This commit also adds 'subgroups' field to the user_group present
in the event sent on creating a user group. We do not allow passing
the subgroups while creating a user group as of this commit, but added
the field in the event object to pass tests.
Zixuan James Li
Anders Kaseorg
Ujjawal Modi
Sahil Batra