Ian Lewis Developer Advocate, Google Cloud Platform The Enemy Within Running Untrusted Code in Kubernetes

2 gVisor Ian Lewis (@IanMLewis) Developer Advocate, Google

3 gVisor ● Running untrusted code ● Third-party/User uploaded code ○ Vendor-built apps ○ SaaS/Serverless ● Complex code/Complex user input ○ Video/Image transcoding ○ Machine learning ● Code you wrote but you don't trust yourself…. So you want to run some code...

4 gVisor Too much privileged code Application Host Kernel

5 gVisor Too much privileged code Application Host Kernel open("/path/to/file", O_RDWR)

6 gVisor Too much privileged code Application Host Kernel

7 gVisor Too much privileged code Application Host Kernel file descriptor

8 gVisor Too much privileged code Application Host Kernel Application

9 gVisor Too much privileged code Host Kernel open("/../\x00...", O_RDWR) Application Application

10 gVisor Too much privileged code Host Kernel Application Application

11 gVisor Too much privileged code Host Kernel Application Application

12 gVisor

13 gVisor ● Protects attackers from escaping the runtime environment ● Code running in the sandbox is untrusted ● Goal: Reduce the attack surface for untrusted code ● Method: Reduce the amount of trusted or privileged code (e.g. kernel code) that gets run. ○ Achieved through abstraction/virtualization of host. Container Sandboxes

14 gVisor Containers & Seccomp sandboxes Application Host Kernel Namespace

15 gVisor ● Pros ○ Same performance as normal processes ○ Uses built-in OS features. ● Cons ○ They aren't good security isolation boundaries ○ Any one bug in the host kernel could lead to a full host compromise ○ Seccomp sandboxes must be tweaked per application Containers & Seccomp sandboxes

16 gVisor Unikernels Application Host Kernel Guest OS Hypervisor

17 gVisor ● Pros ○ Reasonably fast ○ Low overhead/startup ○ Good compatibility ● Cons ○ Can't bring your own container (must be specially crafted) ○ Many limitations (fork, dynamic loading of libraries, etc.) Unikernels

18 gVisor Nabla Containers (nabla-containers.github.io)

19 gVisor Virtual Machines Application OS Virtualized Hardware

20 gVisor ● Pros ○ Hardware acceleration. Raw-performance is good ○ Maintenance is well understood ● Cons ○ Security implications often not well understood ○ Nested virtualization slow & source of security bugs ○ Resource management difficult ○ Often requires layers of indirection and proxies Virtual Machines

21 gVisor Kata Containers (katacontainers.io)

22 gVisor ● Hybrid approach = Virtualization w/ Host Resources ● Uses the same principle of virtualization as VMs ○ Virtualization at the OS; Linux Syscall layer ● Reduces the host attack surface ○ Calls to the host OS are controlled by the Sentry ○ Most syscall logic handled by Sentry ○ No syscalls are "passed through". Applications cannot pass arbitrary arguments to the host kernel. gVisor (gvisor.dev)

23 gVisor Hardware Virtualization Application OS Virtualized Hardware

24 gVisor OS Virtualization Application Virtualized OS

25 gVisor gVisor (gvisor.dev) KVM/ptrace Gofer Gofer Gofers Containers Containers Host Linux Kernel Containers Sentry Sandbox User Kernel 9P runsc OCI seccomp + ns seccomp + ns

26 gVisor ● Container-Native ○ Built from the ground up for containers ○ Host process - resource limits, secrets, volumes, etc. ● Portable ○ Can run inside of VMs ○ Doesn't need hardware support but can use it if available ● Resource Efficient ○ Able to use the host OS for resource management ○ Workloads can be tightly packed gVisor (gvisor.dev)

27 gVisor ● Cons ○ Compatibility (always getting better) ○ I/O Performance (also being improved) gVisor (gvisor.dev)

28 gVisor apiVersion: node.k8s.io/v1beta1 kind: RuntimeClass metadata: name: myclass # The name of the corresponding CRI configuration handler: myhandler Runtimes & Kubernetes

29 gVisor Runtimes & Kubernetes myhandler shim OCI Kubernetes myhandler runtime CRI handler: myhandler

30 gVisor ● Be aware of defaults ○ K8s is optimized for ease-of-use, not security ○ CPU/Memory/Disk limits ● Network/Disk isolation ○ Network access: Use NetworkPolicy ○ Arbitrary packet injection ○ File writes/permissions: Use read-only filesystems ○ No throttling mechanism: use cgroups What's not protected?

31 gVisor gVisor https://gvisor.dev/ Gitter: https://gitter.im/gvisor/community Mailing lists: gvisor-users, gvisor-dev Thanks! https://katacontainers.io/ Nabla Containers https://nabla-containers.github.io/