Описание
Capsule Proxy Authentication bypass using an empty token
The privilege escalation is based on a missing check if the user is authenticated based on the TokenReview result.
All the clusters running with the anonymous-auth Kubernetes API Server setting disable (set to false) are affected since it would be possible to bypass the token review mechanism, interacting with the upper Kubernetes API Server.
PoC
Start a KinD cluster with the anonymous-auth value to false.
If it is true, it uses anonymous permissions which are very limited by default
Install capsule and capsule-proxy
Then query the proxy
Impact
The whole cluster is exposed to unauthorised users.
This privilege escalation cannot be exploited if you're relying only on client certificates (SSL/TLS).
Пакеты
github.com/projectcapsule/capsule-proxy
<= 0.4.5
0.4.6
github.com/clastix/capsule-proxy
<= 0.4.5
0.4.6
Связанные уязвимости
capsule-proxy is a reverse proxy for the capsule operator project. Affected versions are subject to a privilege escalation vulnerability which is based on a missing check if the user is authenticated based on the `TokenReview` result. All the clusters running with the `anonymous-auth` Kubernetes API Server setting disable (set to `false`) are affected since it would be possible to bypass the token review mechanism, interacting with the upper Kubernetes API Server. This privilege escalation cannot be exploited if you're relying only on client certificates (SSL/TLS). This vulnerability has been addressed in version 0.4.6. Users are advised to upgrade.