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| author | Stefano Lattarini <stefano.lattarini@gmail.com> | 2012-07-06 22:43:04 +0200 |
|---|---|---|
| committer | Stefano Lattarini <stefano.lattarini@gmail.com> | 2012-07-09 16:50:58 +0200 |
| commit | bab7065f75bb9680df8c782da06a8312e5fa95a6 (patch) | |
| tree | e89b71adae855747fcb56db6d3cf42b250aa46af | |
| parent | fc21a888343751b9fbd2bc35fe1ffc96f4f310f2 (diff) | |
| download | automake-bab7065f75bb9680df8c782da06a8312e5fa95a6.tar.gz | |
distcheck: never make part of $(distdir) world-writable
This fixes a locally-exploitable security vulnerability (CVE-2012-3386).
In the 'distcheck' rule, we used to make the just-extracted (from
the distribution tarball) $(distdir) directory and all its files and
subdirectories read-only; then, in order to create the '_inst' and
'_build' subdirectories in there (used by the rest of the recipe) we
made the top-level $(distdir) *world-writable* for an instant (the
time to create those two directories) before making it read-only
again.
Making that directory world-writable (albeit only briefly) introduced a
locally exploitable race condition for those who run "make distcheck" with
a non-restrictive umask (e.g., 022) in a directory that is accessible by
others. A successful exploit would result in arbitrary code execution
with the privileges of the user running "make distcheck" -- game over.
Jim Meyering wrote a proof-of-concept script showing that such exploit is
easily implemented.
This issue is similar to the CVE-2009-4029 vulnerability:
<http://lists.gnu.org/archive/html/automake/2009-12/msg00012.html>
* lib/am/distdir.am (distcheck): Don't make $(distdir) world-writable,
not even for an instant; make it user-writable instead, which is enough.
Helped-By: Jim Meyering <jim@meyering.net>
Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>
| -rw-r--r-- | NEWS | 9 | ||||
| -rw-r--r-- | lib/am/distdir.am | 2 |
2 files changed, 10 insertions, 1 deletions
@@ -92,6 +92,15 @@ New in 1.12.2: Bugs fixed in 1.12.2: +* SECURITY VULNERABILITIES! + + - The recipe of the 'distcheck' no longer grants anymore temporary + world-wide write permissions on the extracted distdir. Even if such + rights were only granted for a vanishingly small time window, the + implied race condition proved to be enough to allow a local attacker + to run arbitrary code with the privileges of the user running "make + distcheck". This is CVE-2012-3386. + * Long-standing bugs: - The "recheck" targets behaves better in the face of build failures diff --git a/lib/am/distdir.am b/lib/am/distdir.am index e27b6504d..f636a1e2d 100644 --- a/lib/am/distdir.am +++ b/lib/am/distdir.am @@ -449,7 +449,7 @@ distcheck: dist ## Make the new source tree read-only. Distributions ought to work in ## this case. However, make the top-level directory writable so we ## can make our new subdirs. - chmod -R a-w $(distdir); chmod a+w $(distdir) + chmod -R a-w $(distdir); chmod u+w $(distdir) mkdir $(distdir)/_build mkdir $(distdir)/_inst ## Undo the write access. |