From 841ac8318afb0dada6505d24208926abbf564f77 Mon Sep 17 00:00:00 2001 From: Alex Price Date: Wed, 21 Aug 2019 15:14:08 +1000 Subject: [PATCH] docs: add documentation for privileged and host devices This commit adds documentation for privileged containers and the mounting of host devices when privileged is used. It has instructions for disabling this functionality when using Containerd and CRI. Fixes #529 Signed-off-by: Alex Price --- Limitations.md | 2 ++ how-to/README.md | 1 + how-to/privileged.md | 46 ++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 49 insertions(+) create mode 100644 how-to/privileged.md diff --git a/Limitations.md b/Limitations.md index 3af550736..c5f49c572 100644 --- a/Limitations.md +++ b/Limitations.md @@ -231,6 +231,8 @@ This is also true with using `securityContext privileged=true` with Kubernetes. The container may also be granted full access to a subset of host devices (https://github.com/kata-containers/runtime/issues/1568). +See [Privileged Kata Containers](how-to/privileged.md) for how to configure some of this behavior. + # Miscellaneous This section lists limitations where the possible solutions are uncertain. diff --git a/how-to/README.md b/how-to/README.md index a49c50a9d..5ed416a90 100644 --- a/how-to/README.md +++ b/how-to/README.md @@ -9,3 +9,4 @@ - [Setting Sysctls with Kata](how-to-use-sysctls-with-kata.md) - [What Is VMCache and How To Enable It](what-is-vm-cache-and-how-do-I-use-it.md) - [What Is VM Templating and How To Enable It](what-is-vm-templating-and-how-do-I-use-it.md) +- [Privileged Kata Containers](privileged.md) diff --git a/how-to/privileged.md b/how-to/privileged.md new file mode 100644 index 000000000..3a4733bce --- /dev/null +++ b/how-to/privileged.md @@ -0,0 +1,46 @@ +# Privileged Kata Containers + +Kata Containers supports creation of containers that are "privileged" (i.e. have additional capabilities and access +that is not normally granted). + +* [Warnings](#warnings) + * [Host Devices](#host-devices) + * [Containerd and CRI](#containerd-and-cri) + +## Warnings + +**Warning:** Whilst this functionality is supported, it can decrease the security of Kata Containers if not configured +correctly. + +### Host Devices + +By default, when privileged is enabled for a container, all the `/dev/*` block devices from the host are mounted +into the guest. This will allow the privileged container inside the Kata guest to gain access to mount any block device +from the host, a potentially undesirable side-effect that decreases the security of Kata. + +The following sections document how to configure this behavior in different container runtimes. + +#### Containerd and CRI + +The Containerd CRI allows configuring the privileged host devices behavior for each runtime in the CRI config. This is +done with the `privileged_without_host_devices` option. Setting this to `true` will disable hot plugging of the host +devices into the guest, even when privileged is enabled. + +See below example config: + +```toml +[plugins] + [plugins.cri] + [plugins.cri.containerd] + [plugins.cri.containerd.runtimes.runc] + runtime_type = "io.containerd.runc.v1" + privileged_without_host_devices = false + [plugins.cri.containerd.runtimes.kata] + runtime_type = "io.containerd.kata.v2" + privileged_without_host_devices = true + [plugins.cri.containerd.runtimes.kata.options] + ConfigPath = "/opt/kata/share/defaults/kata-containers/configuration.toml" +``` + + - [Kata Containers with Containerd and CRI documentation](how-to-use-k8s-with-cri-containerd-and-kata.md) + - [Containerd CRI config documentation](https://github.com/containerd/cri/blob/master/docs/config.md)