SpiceDB: LookupSubjects may return partial results if a specific kind of relation is used

Vulnerability Description

SpiceDB is a graph database purpose-built for storing and evaluating access control data. Use of a relation of the form: `relation folder: folder | folder#parent` with an arrow such as `folder->view` can cause LookupSubjects to only return the subjects found under subjects for either `folder` or `folder#parent`. This bug only manifests if the same subject type is used multiple types in a relation, relationships exist for both subject types and an arrow is used over the relation. Any user making a negative authorization decision based on the results of a LookupSubjects request with version before v1.30.1 is affected. Version 1.30.1 contains a patch for the issue. As a workaround, avoid using LookupSubjects for negative authorization decisions and/or avoid using the broken schema.

References

• https://github.com/authzed/spicedb/security/advisories/GHSA-j85q-46hg-36p2
• https://github.com/authzed/spicedb/commit/a244ed1edfaf2382711dccdb699971ec97190c7b
• https://github.com/authzed/spicedb/releases/tag/v1.30.1