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

High severity GitHub Reviewed Published Jun 22, 2021 in ory/oathkeeper • Updated Jan 9, 2023

Package

gomod github.com/ory/oathkeeper (Go)

Affected versions

>= 0.38.0-beta.2, <= 0.38.11-beta.1

Patched versions

0.38.12-beta.1

Description

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.

References

@aeneasr aeneasr published to ory/oathkeeper Jun 22, 2021
Reviewed Jun 22, 2021
Published to the GitHub Advisory Database Jun 23, 2021
Last updated Jan 9, 2023

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Weaknesses

CVE ID

No known CVE

GHSA ID

GHSA-qvp4-rpmr-xwrr

Source code

No known source code

Credits

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