[Differential] [Request, 10 lines] D1524: ar: Disallow directory traversal

[emaste (Ed Maste)]

emaste created this revision.
emaste added a subscriber: freebsd-toolchain.

REVISION SUMMARY
  Set ARCHIVE_EXTRACT_SECURE_SYMLINKS and ARCHIVE_EXTRACT_SECURE_NODOTDOT as in bsdtar to prevent extraction of archive entries whose pathnames contain .. or whose target directory would be altered by a symlink. Also disallow absolute pathnames.
  
  We don't currently provide an option to disable this behaviour (as bsdtar's -P does). It is unlikely to be a problem in practice for ar(1), but the -P option is available if we want to allow it.
  
  Reported by: Alexander Cherepanov <cherepan at mccme.ru>
  Elftoolchain ticket: 474

TEST PLAN
  From https://sourceforge.net/p/elftoolchain/tickets/474/
  
  ~~~
  printf '!<arch>\n%-48s%-10s`\n%-48s%-10s`\n' /tmp/file 0 ../file 0 > test.a
  n% ./ar -xv test.a
  x - /tmp/file
  ar: warning: Absolute path '/tmp/file'
  x - ../file
  ar: warning: Path contains '..'
  ~~~

REVISION DETAIL
  https://reviews.freebsd.org/D1524

AFFECTED FILES
  usr.bin/ar/read.c

To: emaste
Cc: freebsd-toolchain