Possible bypass of token claim validation when OAuth2 Introspection caching is enabled

Overview

Impact

When you make a request to an endpoint that requires the scope foo using an access token granted with that foo scope, introspection will be valid and that token will be cached. The problem comes when a second requests to an endpoint that requires the scope bar is made before the cache has expired. Whether the token is granted or not to the bar scope, introspection will be valid.

Patches

A patch will be released with v0.38.12-beta.1.

Workarounds

Per default, caching is disabled for the oauth2_introspection authenticator. When caching is disabled, this vulnerability does not exist.

Trace

The cache is checked in func (a *AuthenticatorOAuth2Introspection) Authenticate(...). From tokenFromCache() it seems that it only validates the token expiration date, but ignores whether the token has or not the proper scopes.

Post-Mortem

The vulnerability was introduced in PR #424. During review, we failed to require appropriate test coverage by the submitter which is the primary reason that the vulnerability passed the review process.

To avoid this from happening again we enabled codecov with a strict policy on the Ory Oathkeeper repository: Without an increase in code coverage the PR can not be merged.

To address this issue and any regressions we have added a test suite ensuring that the cache behaviour is correct in the different scenarios:

• Scope strategy is none, cache is enabled, and requested_scope is not empty -> cache will not be used;
• Scope strategy is none, cache is enabled, and requested_scope is empty -> cache will be used;
• Scope strategy is not none, cache is enabled, and requested_scope is not empty -> cache will be used;

as well as validating if iss, aud, exp, token_use, and scope are validated.

Additionally, we added CodeQL scanning to the CI.

Affected packages

• github.com/ory/oathkeeper >= 0.38.0-beta.2, < 0.38.12-beta.1

Remediation

Upgrade to a patched release:

• github.com/ory/oathkeeper 0.38.12-beta.1