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android / platform / external / minijail / 2337f80306755f8577adb7ac7bd5a5ee4f035e02
commit2337f80306755f8577adb7ac7bd5a5ee4f035e02[log] [tgz]
authorJorge Lucangeli Obes <[email protected]>Thu Jul 18 14:46:03 2019 -0400
committerJorge Lucangeli Obes <[email protected]>Thu Jul 18 14:46:03 2019 -0400
tree15deb040c1cf81aac7d474ba3a63d1bbb23d93bb
parent52f6adabb6f44761cc23a226cc396bd5c664641c [diff]
Preserve namespace file descriptors.

The code in libminijail.c will attempt to close file descriptors (if
instructed to do so) before minijail_enter() attempts to enter the
required namespaces. This is problematic because minijail_enter() will
then fail to call nsenter(2) because the namespace file descriptor has
been closed.

We could move the call to close_open_fds() after minijail_enter() but
this would require every user of Minijail to include the syscalls made
by close_open_fds() in their seccomp policy. Instead, preserve the file
descriptors used to enter mount and network namespaces. It's not really
a problem for these to end up in the child, since
/proc/<pid>/ns/{mnt,net} in the child will give access to the same
resource.

Bug: https://crbug.com/985467
Test: Unit tests pass.
Test: With https://chromium-review.googlesource.com/c/chromiumos/platform2/+/1614745,
Test: Chrome OS can start a guest session.
Change-Id: I2ecf41c148deb5650ebb00f5f35d78f314865c6a
1 file changed
tree: 15deb040c1cf81aac7d474ba3a63d1bbb23d93bb
  1. examples/
  2. linux-x86/
  3. test/
  4. tools/
  5. .clang-format
  6. .gitignore
  7. Android.bp
  8. arch.h
  9. bpf.c
  10. bpf.h
  11. CleanSpec.mk
  12. common.mk
  13. CPPLINT.cfg
  14. dump_constants.cc
  15. elfparse.c
  16. elfparse.h
  17. gen_constants-inl.h
  18. gen_constants.c
  19. gen_constants.sh
  20. gen_syscalls.c
  21. gen_syscalls.sh
  22. get_googletest.sh
  23. HACKING.md
  24. libconstants.h
  25. libminijail-private.h
  26. libminijail.c
  27. libminijail.h
  28. libminijail.pc.in
  29. libminijail_unittest.cc
  30. libminijailpreload.c
  31. libsyscalls.h
  32. LICENSE
  33. Makefile
  34. minijail0.1
  35. minijail0.5
  36. minijail0.c
  37. minijail0_cli.c
  38. minijail0_cli.h
  39. minijail0_cli_unittest.cc
  40. MODULE_LICENSE_BSD
  41. navbar.md
  42. NOTICE
  43. OWNERS
  44. parse_seccomp_policy.cc
  45. platform2_preinstall.sh
  46. PRESUBMIT.cfg
  47. PREUPLOAD.cfg
  48. README.md
  49. RELEASE.md
  50. scoped_minijail.h
  51. signal_handler.c
  52. signal_handler.h
  53. syscall_filter.c
  54. syscall_filter.h
  55. syscall_filter_unittest.cc
  56. syscall_filter_unittest_macros.h
  57. syscall_wrapper.c
  58. syscall_wrapper.h
  59. system.c
  60. system.h
  61. system_unittest.cc
  62. testrunner.cc
  63. util.c
  64. util.h
  65. util_unittest.cc
README.md

Minijail

The Minijail homepage and main 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.

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