Clone this repo:
  1. 4ab1a2c Add riscv64 support by Dylan Reid · 3 months ago master
  2. fdc98d6 run clang-format over minijial0_cli.c by Zi Lin · 2 days ago
  3. a9e7226 Add two compile-flag protected security checks on the conf file. by Zi Lin · 11 days ago
  4. 4170a27 rust/minijail: add Minijail::run_command by Chia-I Wu · 5 weeks ago
  5. 50e99bf rust/minijail: add minijail::Command::envs by Chia-I Wu · 5 weeks ago

Minijail

The Minijail homepage is https://google.github.io/minijail/.

The main source repo is https://android.googlesource.com/platform/external/minijail/.

There might be other copies floating around, but this is the official one!

What is it?

Minijail is a sandboxing and containment tool used in Chrome OS and Android. It provides an executable that can be used to launch and sandbox other programs, and a library that can be used by code to sandbox itself.

Getting the code

You're one git clone away from happiness.

$ git clone https://android.googlesource.com/platform/external/minijail
$ cd minijail

Releases are tagged as linux-vXX: https://android.googlesource.com/platform/external/minijail/+refs

Building

See the HACKING.md document for more details.

Release process

See the RELEASE.md document for more details.

Additional tools

See the tools/README.md document for more details.

Contact

We've got a couple of contact points.

Talks and presentations

The following talk serves as a good introduction to Minijail and how it can be used.

Video, slides.

Example usage

The Chromium OS project has a comprehensive sandboxing document that is largely based on Minijail.

After you play with the simple examples below, you should check that out.

Change root to any user

# id
uid=0(root) gid=0(root) groups=0(root),128(pkcs11)
# minijail0 -u jorgelo -g 5000 /usr/bin/id
uid=72178(jorgelo) gid=5000(eng) groups=5000(eng)

Drop root while keeping some capabilities

# minijail0 -u jorgelo -c 3000 -- /bin/cat /proc/self/status
Name: cat
...
CapInh: 0000000000003000
CapPrm: 0000000000003000
CapEff: 0000000000003000
CapBnd: 0000000000003000

Historical notes

Q. “Why is it called minijail0?”

A. It is minijail0 because it was a rewrite of an earlier program named minijail, which was considerably less mini, and in particular had a dependency on libchrome (the Chrome OS packaged version of Chromium's //base). We needed a new name to not collide with the deprecated one.

We didn‘t want to call it minijail2 or something that would make people start using it before we were ready, and it was also concretely less since it dropped libbase, etc. Technically, we needed to be able to fork/preload with minimal extra syscall noise which was too hard with libbase at the time (onexit handlers, etc that called syscalls we didn’t want to allow). Also, Elly made a strong case that C would be the right choice for this for linking and ease of controlled surprise system call use.

https://crrev.com/c/4585/ added the original implementation.

Source: Conversations with original authors, ellyjones@ and wad@.

How to manually upgrade Minijail on Chrome OS

Minijail is manually upgraded on Chrome OS so that there is a way to test changes in the Chrome OS commit queue. Committed changes have already passed Android's presubmit checks, but the ebuild upgrade CL goes through the Chrome OS commit queue and must pass the tests before any additional changes are available for use on Chrome OS. To upgrade minijail on Chrome OS, complete the following steps.

# Sync Minijail repo
cd ~/chromiumos/src/aosp/external/minijail
git checkout m/main
repo sync .

# Set up local branch.
cd ~/trunk/src/third_party/chromiumos-overlay/
repo start minijail .  # replace minijail with the local branch name you want.

# Run upgrade script.
~/trunk/chromite/scripts/cros_uprev --force --overlay-type public \
  --packages chromeos-base/minijail:dev-rust/minijail-sys:dev-rust/minijail

At this point the Minijail-related packages should be upgraded, so you may want to add the changes to a commit and do some local testing before uploading a change list. Here are the recommended local tests to try (make sure you are not working on the minijail packages first i.e. cros_workon list-all):

# Check build.
./build_packages --board=${BOARD}

# Check unit tests.
FEATURES=test emerge-${BOARD} chromeos-base/minijail dev-rust/minijail-sys \
  dev-rust/minijail

# Check integration tests.
cros deploy <DUT> chromeos-base/minijail
tast run <DUT> security.Minijail security.MinijailSeccomp

Finally, when uploading the CL make sure to include the list of changes since the last uprev. The command to generate the list is as follows:

git log --oneline --no-merges <previous hash in ebuild file>..HEAD