A talk given at the Google-hosted Container Security Summit on Wednesday, February 12th, 2020 in Seattle, Washington. This talk covered the impact of work done at the lower-level runtimes layer and up through layers like cri-o, containerd, and Docker to bring specific security features to overall platforms like Kubernetes.

1. @estesp
Enabling security via runtimes
A container runtime perspective on security
Phil Estes
Distinguished Engineer & CTO, IBM Cloud Platform
CNCF containerd project maintainer
OCI Technical Oversight Board chair

2. @estesp
Runtimes circa 2014
● No seccomp
● No pids limit
● No user namespaces
● No rootless
● No content-addressable image format
● No sandboxes
● ...

3. @estesp
Runtime Reorganization
● Open Container Initiative (OCI) and CNCF formed: Summer 2015
● libcontainer project donated to become “runc”
● Docker architecturally splits into the engine, containerd, and runc
● Later, containerd and cri-o emerge as standalone runtimes without
Docker engine

4. @estesp
Runtime Security Progress
Late 20162015
Early 2016 2017
PIDS controller
SECCOMP support
Docker 1.10
● user namespaces, seccomp
profiles, auth plugins
● New content-addressable
image format (v2.2)
No new privs support
User NS nesting
Ambient caps
readonly+userns
rootless runc

5. @estesp
Secure image layer hashes, new manifest

6. @estesp
User namespaces, Phase 1

7. @estesp
Resources, Attack Surface, ...Privilege!
Rootless containers refers to the ability for an unprivileged user to create, run and
otherwise manage containers.
● Docker “Shocker” 2014
● Docker CVE-2014-9357
● Containerd #2001 (2018)
● Runc #1962 (2019)
● K8s CVE-2017-1002101, CVE-2017-1002102
● K8s CVE-2018-1002105
● …?

8. @estesp
Rootless Containers
● Built on Linux kernel user namespaces functionality
○ An unprivileged user manages a user and group range in which containers
will run
● Limitations for privileged actions handled via userspace
functionality
○ slirp4netns - required for network creation/interactions
○ fuse-overlayfs - required for root filesystem interactions and handles
UID/GID shifts
○ cgroups - cannot manage cgroups in rootless containers, v2 is solution
● Upstream kernel and related projects (overlayfs) continue
work to remove limitations/performance impacts
● Available at all levels (runc, container runtimes, builders,
Kubernetes***)

9. @estesp
Are we done yet? 😅

10. @estesp
Sandboxes: Linux Containers++
What if we could consolidate the developer experience of
containers with the isolation guarantees of virtual machines?

11. @estesp
Runtime shim v2 API
● Minimal and scoped to the execution lifecycle of a container
● Binary naming convention
○ Type io.containerd.runsc.v1 -> Binary containerd-shim-runsc-v1

12. @estesp
Runtime Plugins - Task Service
service Task {
rpc State(StateRequest) returns (StateResponse);
rpc Create(CreateTaskRequest) returns (CreateTaskResponse);
rpc Start(StartRequest) returns (StartResponse);
rpc Delete(DeleteRequest) returns (DeleteResponse);
rpc Pids(PidsRequest) returns (PidsResponse);
rpc Pause(PauseRequest) returns (google.protobuf.Empty);
rpc Resume(ResumeRequest) returns (google.protobuf.Empty);
rpc Checkpoint(CheckpointTaskRequest) returns (google.protobuf.Empty);
rpc Kill(KillRequest) returns (google.protobuf.Empty);
rpc Exec(ExecProcessRequest) returns (google.protobuf.Empty);
rpc ResizePty(ResizePtyRequest) returns (google.protobuf.Empty);
rpc CloseIO(CloseIORequest) returns (google.protobuf.Empty);
rpc Update(UpdateTaskRequest) returns (google.protobuf.Empty);
rpc Wait(WaitRequest) returns (WaitResponse);
rpc Stats(StatsRequest) returns (StatsResponse);
rpc Connect(ConnectRequest) returns (ConnectResponse);
rpc Shutdown(ShutdownRequest) returns (google.protobuf.Empty);
}

13. @estesp
Using Sandboxes
● RuntimeClass + CRI provide a way to utilize custom sandboxes

14. @estesp
Encrypted Container Layers
● Provide a method to encrypt specific image layers with target keys for
secure delivery to approved runtime nodes
● Implemented components available/underway in:
○ containers/image, cri-o, buildah, containerd, generic library implementation
○ Kubernetes KEP under review (https://github.com/kubernetes/enhancements/pull/1066)
○ Proposed update to OCI image-spec (https://github.com/opencontainers/image-spec/pull/775)

15. @estesp
What’s Left?

16. @estesp
Thank You!