Exposure of Sensitive Information to an Unauthorized Actor

Summary

The Bare Metal Operator (BMO) implements a Kubernetes API for managing bare metal hosts in Metal3. The "BareMetalHost" (BMH) CRD allows the "userData", "metaData", and "networkData" for the provisioned host to be specified as links to Kubernetes Secrets. There are fields for both the "Name" and "Namespace" of the Secret, meaning that versions of the github.com/metal3-io/baremetal-operator package through 0.5.1, 0.6.0 through 0.6.1, 0.7.0-rc.0 through 0.8.0-rc.0, will read a "Secret" from any namespace. A user with access to create or edit a "BareMetalHost" can thus exfiltrate a "Secret" from another namespace by using it as e.g. the "userData" for provisioning some host (note that this need not be a real host, it could be a VM somewhere). BMO will only read a key with the name "value" (or "userData", "metaData", or "networkData"), so that limits the exposure somewhat. "value" is probably a pretty common key though. Secrets used by other "BareMetalHost"s in different namespaces are always vulnerable. It is probably relatively unusual for anyone other than cluster administrators to have RBAC access to create/edit a "BareMetalHost". This vulnerability is only meaningful if the cluster has users other than administrators and users' privileges are limited to their respective namespaces. The patch prevents BMO from accepting links to Secrets from other namespaces as BMH input. Any BMH configuration is only read from the same namespace. The problem is patched in BMO releases v0.8.0, v0.6.2, and v0.5.2 and users should upgrade to those versions. Prior to upgrading, duplicate the BMC Secrets to the namespace where the corresponding BMH is. After upgrading, remove the old secrets. As a workaround, an operator can configure BMO RBAC to be namespace scoped for Secrets, instead of cluster scoped, to prevent BMO from accessing Secrets from other namespaces.