kata-containers/docs/how-to/how-to-use-seccomp-with-runtime-rs.md

Introduction

To enhance security, Kata Containers supports using seccomp to restrict the hypervisor's system calls. Previously, this was only supported for a subset of hypervisors in runtime-go. Now, the runtime-rs also supports seccomp. This document describes how to enable/disable the seccomp feature for the corresponding hypervisor in runtime-rs.

Pre-requisites

1. Ensure your system's kernel supports seccomp.
2. Confirm that each of the following virtual machines can run correctly on your system.

Configure seccomp

With the exception of qemu, seccomp is enabled by default for all other supported hypervisors. Their corresponding built-in functionalities are also enabled by default.

QEMU

As with runtime-go, you need to modify the following in your configuration file. These parameters will be passed directly to the qemu startup command line. For more details on the parameters, you can refer to: https://www.qemu.org/docs/master/system/qemu-manpage.html

# Qemu seccomp sandbox feature
# comma-separated list of seccomp sandbox features to control the syscall access.
# For example, `seccompsandbox= "on,obsolete=deny,spawn=deny,resourcecontrol=deny"`
# Note: "elevateprivileges=deny" doesn't work with daemonize option, so it's removed from the seccomp sandbox
# Another note: enabling this feature may reduce performance, you may enable
# /proc/sys/net/core/bpf_jit_enable to reduce the impact. see https://man7.org/linux/man-pages/man8/bpfc.8.html
seccompsandbox="on,obsolete=deny,spawn=deny,resourcecontrol=deny"

Cloud Hypervisor, Firecracker and Dragonball

The seccomp functionality is enabled by default for the following three hypervisors: cloud hypervisor, firecracker, and dragonball.

The seccomp rules for cloud hypervisor and firecracker are built directly into their executable files. For dragonball, the relevant configuration is currently located at src/runtime-rs/crates/hypervisor/src/dragonball/seccomp.rs.

To disable this functionality for these hypervisors, you can modify the following configuration options in your configuration file.

# Disable the 'seccomp' feature from Cloud Hypervisor, firecracker or dragonball, default false
disable_seccomp = true

Implementation details

For qemu, cloud hypervisor, and firecracker, their seccomp functionality is built into the respective executable files you are using. runtime-rs simply provides command-line arguments for their launch based on the configuration file.

For dragonball, a set of allowed system calls is currently provided for the entire runtime-rs process, and the process is prevented from using any system calls outside of this whitelist. As mentioned above, this set is located at src/runtime-rs/crates/hypervisor/src/dragonball/seccomp.rs.