Zulip attempts to validate that the regular expressions that admins
enter for linkifiers are well-formatted, and only contain a specific
subset of regex grammar. The process of checking these
properties (via a regex!) can cause denial-of-service via
backtracking.
Furthermore, this validation itself does not prevent the creation of
linkifiers which themselves cause denial-of-service when they are
executed. As the validator accepts literally anything inside of a
`(?P<word>...)` block, any quadratic backtracking expression can be
hidden therein.
Switch user-provided linkifier patterns to be matched in the Markdown
processor by the `re2` library, which is guaranteed constant-time.
This somewhat limits the possible features of the regular
expression (notably, look-head and -behind, and back-references);
however, these features had never been advertised as working in the
context of linkifiers.
A migration removes any existing linkifiers which would not function
under re2, after printing them for posterity during the upgrade; they
are unlikely to be common, and are impossible to fix automatically.
The denial-of-service in the linkifier validator was discovered by
@erik-krogh and @yoff, as GHSL-2021-118.
We now validate the linkifier urls and patterns together, and add
the following additional checks:
1. All groups in the pattern must be used in the URL format string.
2. All groups in the URL format string must be declared in the pattern.
Linkifier pattern is now validated inside the `clean` method.
`filter_pattern_validator` is moved from `clean_fields` to `clean`
method as a safe check. As a result of this, a Puppeteer test case
is updated.
NOTE: The changes here are IN ADDITION to the existing validations.
Fixes#16482.
Co-authored-by: akshatdalton <akshat.dak@students.iiit.ac.in>
This commit adds an API to `zproject/urls.py` to edit/update
the realm linkifier. Its helper function to update the
database is added in `zerver/lib/actions.py`.
`zulip.yaml` is documented accordingly as well, clearly
stating that this API updates one linkifier at a time.
The tests are added for the API and helper function which
updates the realm linkifier.
Fixes#10830.
Use backend-endpoint function instead of helper function in
`test_realm_linkifiers.py` so that tests are more end-to-end.
The removed helper function: `do_add_linkifier` is tested in
`zerver/tests/test_events.py`.
Linkifier error message: `Filter not found` is
updated to `Linkifier not found.`.
Similarly, `filter_id` description is updated to:
`The ID of the linkifier that you want to remove.`,
renamed the term `filter` with `linkifier`, in `zulip.yaml`.
* This introduces a new event type `realm_linkifiers` and
a new key for the initial data fetch of the same name.
Newer clients will be expected to use these.
* Backwards compatibility is ensured by changing neither
the current event nor the /register key. The data which
these hold is the same as before, but internally, it is
generated by processing the `realm_linkifiers` data.
We send both the old and the new event types to clients
whenever the linkifiers are changed.
Older clients will simply ignore the new event type, and
vice versa.
* The `realm/filters:GET` endpoint (which returns tuples)
is currently used by none of the official Zulip clients.
This commit replaces it with `realm/linkifiers:GET` which
returns data in the new dictionary format.
TODO: Update the `get_realm_filters` method in the API
bindings, to hit this new URL instead of the old one.
* This also updates the webapp frontend to use the newer
events and keys.
This is a prep change to eventually completely
replace the term "filter" with "linkifier" in
the codebase.
This only renames files. Code changes will be
done in further commits.
Alex Vandiver
Rohitt Vashishtha
Abhijeet Prasad Bodas
akshatdalton