mirrors/crosvm
1
0
Fork 0
mirror of https://chromium.googlesource.com/crosvm/crosvm synced 2025-02-08 19:33:07 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions
crosvm/seccomp
History
Dennis Kempin a0dcf8ab13 Generate constants.json offline 
The constants.json file is generated for compiling seccomp polices,
but is only ever added to in newer versions of linux.
Generating them in build.rs will cause the seccomp compiler to only
understand constants and syscalls available on the build machine
and fail if policy files try to allow syscalls not available.

Putting the constants in version control will allow us to compile
the policies regardless of how old the kernel headers on the build
machine are.

BUG=b:235858187
TEST=presubmit

Change-Id: I1cfbb38f4687eb68b141f62c1c5fe6104b3f6456
Reviewed-on: https://chromium-review.googlesource.com/c/crosvm/crosvm/+/3988899
Commit-Queue: Daniel Verkamp <dverkamp@chromium.org>
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>
Auto-Submit: Dennis Kempin <denniskempin@google.com>
2022-11-02 00:13:08 +00:00
..
aarch64 Generate constants.json offline 2022-11-02 00:13:08 +00:00
arm Generate constants.json offline 2022-11-02 00:13:08 +00:00
x86_64 Generate constants.json offline 2022-11-02 00:13:08 +00:00
generate_constants.sh Generate constants.json offline 2022-11-02 00:13:08 +00:00
README.md seccomp: define naming rules for policy files 2022-06-17 04:35:09 +00:00

README.md

Policy files for crosvm

This folder holds the seccomp policies for crosvm devices, organized by architecture.

Each crosvm device can run within its owned jailed process. A jailed process is only able to perform the system calls specified in the seccomp policy file the jail has been created with, which improves security as a rogue process cannot perform any system call it wants.

Each device can run from different contexts, which require a different set of authorized system calls. This file explains how the policy files are named in order to allow these various scenario.

Naming conventions

Since Minijail only allows for one level of policy inclusion, we need to be a little bit creative in order to minimize policy duplication.

  • common_device.policy contains a set of syscalls that are common to all devices, and is never loaded directly - only included from other policy files.
  • foo.policy contains the set of syscalls that device foo is susceptible to use, regardless of the underlying virtio transport. This policy is also never loaded directly.
  • foo_device.policy is the policy that is loaded when device foo is used as an in-VMM (i.e. regular virtio) device. It will generally simply include common_device.policy as well as foo.policy.

When using vhost-user, the virtio protocol needs to be sent over a different medium, e.g. a Unix socket. Supporting this transport requires some extra system calls after the device is jailed, and thus dedicated policies:

  • vhost_user.policy contains the set of syscalls required by the regular (i.e. socket-based) vhost-user listener. It is never loaded directly.
  • vvu.policy contains the set of syscalls required by the VFIO-based vhost-user (aka Virtio-Vhost-User) listener. It is also never loaded directly.
  • foo_device_vhost_user.policy is the policy that is loaded when device foo is used as a regular vhost-user device. It will generally include common_device.policy, vhost_user.policy and foo.policy.
  • foo_device_vvu.policy is the policy that is loaded when device foo is used as a VVU device. It will generally include common_device.policy, vvu.policy and foo.policy.