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android / platform / external / minijail / 93fe88646ac637a04909fb3dd2ccae735509b0f5
commit93fe88646ac637a04909fb3dd2ccae735509b0f5[log] [tgz]
authorJunichi Uekawa <[email protected]>Tue Jul 12 21:40:42 2022 +0900
committerChromeos LUCI <[email protected]>Mon Aug 22 08:32:45 2022 +0000
tree212e44361c50ca94a8f90ffc70f7e86ad07ccdd7
parentddc532c07a25769b350e92b0a22d0e23e66a5395 [diff]
rust/minijail: Add a note on how unsafe fork() is.

Fork() closes FDs but more importantly, it consumes the Minijail object
and cannot run the second time.

BUG=b:238646369
TEST=read it.

Change-Id: Ieec74056c35fa42abe8e7df1f86f5691c61d4e57
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/minijail/+/3833624
Reviewed-by: Daniel Verkamp <[email protected]>
Tested-by: Junichi Uekawa <[email protected]>
Reviewed-by: Allen Webb <[email protected]>
Commit-Queue: Junichi Uekawa <[email protected]>
1 file changed
tree: 212e44361c50ca94a8f90ffc70f7e86ad07ccdd7
  1. .github/
  2. examples/
  3. linux-x86/
  4. rust/
  5. test/
  6. tools/
  7. .clang-format
  8. .gitignore
  9. Android.bp
  10. arch.h
  11. bpf.c
  12. bpf.h
  13. CleanSpec.mk
  14. common.mk
  15. config_parser.c
  16. config_parser.h
  17. config_parser_unittest.cc
  18. CPPLINT.cfg
  19. DIR_METADATA
  20. dump_constants.cc
  21. elfparse.c
  22. elfparse.h
  23. gen_constants-inl.h
  24. gen_constants.c
  25. gen_constants.sh
  26. gen_syscalls-inl.h
  27. gen_syscalls.c
  28. gen_syscalls.sh
  29. get_googletest.sh
  30. HACKING.md
  31. landlock.h
  32. landlock_util.c
  33. landlock_util.h
  34. libconstants.h
  35. libminijail-private.h
  36. libminijail.c
  37. libminijail.h
  38. libminijail.pc.in
  39. libminijail_unittest.cc
  40. libminijailpreload.c
  41. libsyscalls.h
  42. LICENSE
  43. Makefile
  44. METADATA
  45. minijail0.1
  46. minijail0.5
  47. minijail0.c
  48. minijail0.sh
  49. minijail0_cli.c
  50. minijail0_cli.h
  51. minijail0_cli_unittest.cc
  52. MODULE_LICENSE_BSD
  53. navbar.md
  54. NOTICE
  55. OWNERS
  56. OWNERS_GENERAL
  57. parse_seccomp_policy.cc
  58. platform2_preinstall.sh
  59. PRESUBMIT.cfg
  60. PREUPLOAD.cfg
  61. README.md
  62. RELEASE.md
  63. scoped_minijail.h
  64. setup.py
  65. signal_handler.c
  66. signal_handler.h
  67. syscall_filter.c
  68. syscall_filter.h
  69. syscall_filter_unittest.cc
  70. syscall_filter_unittest_macros.h
  71. syscall_wrapper.c
  72. syscall_wrapper.h
  73. system.c
  74. system.h
  75. system_unittest.cc
  76. TEST_MAPPING
  77. test_util.cc
  78. test_util.h
  79. testrunner.cc
  80. unittest_util.h
  81. util.c
  82. util.h
  83. util_unittest.cc
README.md

Minijail

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

The main source repo is https://chromium.googlesource.com/chromiumos/platform/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://chromium.googlesource.com/chromiumos/platform/minijail
$ cd minijail

Releases are tagged as linux-vXX: https://chromium.googlesource.com/chromiumos/platform/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@.