Rancher API and cluster.management.cattle.io object vulnerable to plaintext storage and exposure of credentials

Affecting github.com/rancher/rancher package on Go

Context / Overview

Impact

An issue was discovered in Rancher versions up to and including 2.5.15 and 2.6.6 where sensitive fields, like passwords, API keys and Rancher's service account token (used to provision clusters), were stored in plaintext directly on Kubernetes objects like Clusters, for example cluster.management.cattle.io. Anyone with read access to those objects in the Kubernetes API could retrieve the plaintext version of those sensitive data.

The exposed credentials are visible in Rancher to authenticated Cluster Owners, Cluster Members, Project Owners, Project Members and User Base on the endpoints:

/v1/management.cattle.io.catalogs
/v1/management.cattle.io.cluster
/v1/management.cattle.io.clustertemplates
/v1/management.cattle.io.notifiers
/v1/project.cattle.io.sourcecodeproviderconfig
/k8s/clusters/local/apis/management.cattle.io/v3/catalogs
/k8s/clusters/local/apis/management.cattle.io/v3/clusters
/k8s/clusters/local/apis/management.cattle.io/v3/clustertemplates
/k8s/clusters/local/apis/management.cattle.io/v3/notifiers
/k8s/clusters/local/apis/project.cattle.io/v3/sourcecodeproviderconfigs

Sensitive fields are now stripped from Clusters and other objects and moved to a Secret before the object is stored. The Secret is retrieved when the credential is needed. For objects that existed before this security fix, a one-time migration happens on startup.

Important:

The exposure of Rancher's serviceAccountToken allows any standard user to escalate its privileges to cluster administrator in Rancher.
For the exposure of credentials not related to Rancher, the final impact severity for confidentiality, integrity and availability is dependent on the permissions that the leaked credentials have on their own services.

The fields that have been addressed by this security fix are:

Notifier.SMTPConfig.Password
Notifier.WechatConfig.Secret
Notifier.DingtalkConfig.Secret
Catalog.Spec.Password
SourceCodeProviderConfig.GithubPipelineConfig.ClientSecret
SourceCodeProviderConfig.GitlabPipelineConfig.ClientSecret
SourceCodeProviderConfig.BitbucketCloudPipelineConfig.ClientSecret
SourceCodeProviderConfig.BitbucketServerPipelineConfig.PrivateKey
Cluster.Spec.RancherKubernetesEngineConfig.BackupConfig.S3BackupConfig.SecretKey
Cluster.Spec.RancherKubernetesEngineConfig.PrivateRegistries.Password
Cluster.Spec.RancherKubernetesEngineConfig.Network.WeaveNetworkProvider.Password
Cluster.Spec.RancherKubernetesEngineConfig.CloudProvider.VsphereCloudProvider.Global.Password
Cluster.Spec.RancherKubernetesEngineConfig.CloudProvider.VsphereCloudProvider.VirtualCenter.Password
Cluster.Spec.RancherKubernetesEngineConfig.CloudProvider.OpenstackCloudProvider.Global.Password
Cluster.Spec.RancherKubernetesEngineConfig.CloudProvider.AzureCloudProvider.AADClientSecret
Cluster.Spec.RancherKubernetesEngineConfig.CloudProvider.AzureCloudProvider.AADClientCertPassword
Cluster.Status.ServiceAccountToken
ClusterTemplate.Spec.ClusterConfig.RancherKubernetesEngineConfig.PrivateRegistries.Password
ClusterTemplate.Spec.ClusterConfig.RancherKubernetesEngineConfig.Network.WeaveNetworkProvider.Password
ClusterTemplate.Spec.ClusterConfig.RancherKubernetesEngineConfig.CloudProvider.VsphereCloudProvider.Global.Password
ClusterTemplate.Spec.ClusterConfig.RancherKubernetesEngineConfig.CloudProvider.VsphereCloudProvider.VirtualCenter.Password
ClusterTemplate.Spec.ClusterConfig.RancherKubernetesEngineConfig.CloudProvider.OpenstackCloudProvider.Global.Password
ClusterTemplate.Spec.ClusterConfig.RancherKubernetesEngineConfig.CloudProvider.AzureCloudProvider.AADClientSecret
ClusterTemplate.Spec.ClusterConfig.RancherKubernetesEngineConfig.CloudProvider.AzureCloudProvider.AADClientCertPassword

Patches

Patched versions include releases 2.5.16, 2.6.7 and later versions.

After upgrading to a patched version, it is important to check for the SecretsMigrated condition on Clusters, ClusterTemplates, and Catalogs to confirm when secrets have been fully migrated off of those objects and the objects scoped within them (Notifiers and SourceCodeProviderConfigs).

Workarounds

Limit access in Rancher to trusted users. There is not a direct mitigation besides upgrading to the patched Rancher versions.

Important:

It is highly advised to rotate Rancher's serviceAccountToken. This rotation is not done by the version upgrade. Please see the helper script below.
The local and downstream clusters should be checked for potential unrecognized services (pods), users and API keys.
It is recommended to review for potential leaked credentials in this scenario, that are not directly related to Rancher, and to change them if deemed necessary.

The script available in rancherlabs/support-tools/rotate-tokens repository can be used as a helper to rotate the service account token (used to provision clusters). The script requires a valid Rancher API token, kubectl access to the local cluster and the jq command.

Credits

We would like to recognize and appreciate Florian Struck (from Continum AG) and Marco Stuurman (from Shock Media B.V.) for the responsible disclosure of this security issue.

For more information

If you have any questions or comments about this advisory:

Reach out to SUSE Rancher Security team for security related inquiries.
Open an issue in Rancher repository.
Verify our support matrix and product support lifecycle.

Jit Recommended Tools

OSV-Scanner

Objective: Dependency check (SCA)

Description: OSV-Scanner provides an officially supported frontend to the OSV database that connects a project’s list of dependencies with the vulnerabilities that affect them. Since the OSV.dev database is open source and distributed, it has several benefits in comparison with closed source advisory databases and scanners:

Vulnerability Layer - SCA

SCA Dependency Check is one of the important tools used to identify vulnerabilities in open-source components used in software applications. However, it primarily focuses on identifying vulnerabilities in the dependency layer of the software application. In contrast, code vulnerability layer analysis is focused on identifying vulnerabilities in the source code of the application itself, rather than the dependencies it uses. It typically involves analyzing the source code to identify security issues such as buffer overflows, injection vulnerabilities, and authentication issues, among others. While SCA Dependency Check is an important tool in identifying vulnerabilities in open-source dependencies, it may not be sufficient to ensure the overall security of the software application. To ensure comprehensive security, it is important to also perform code vulnerability layer analysis to identify vulnerabilities in the source code of the application. Incorporating both SCA Dependency Check and code vulnerability layer analysis into the software development lifecycle can help ensure that vulnerabilities are identified and remediated at both the dependency and code layers of the application. This can help prevent security issues from being introduced into the final product and improve the overall security posture of the software application.