FYI, this was discovered because of https://forum.snapcraft.io/t/2-0
-lxd-snap-fails-on-sytems-with-partial-apparmor-support/4707
** Description changed:
- Somewhere between 3.13 and 4.4, the scrubbing behavior of ix changed
- when going through aa-exec. For example, on Ubuntu 12.04 and 14.04 we
- have:
+ Somewhere between 3.13 and 4.4, the scrubbing behavior of ix changed.
+ For example, on Ubuntu 12.04 and 14.04 we have:
* ux does not scrub
* Ux does scrub
* ix does not scrub
but in 16.04 and later we have:
* ux does not scrub
* Ux does scrub
* ix does scrub # WRONG
I discussed this with jjohansen some time ago (just now filing the bug)
and we concluded that ix shouldn't scrub and the behavior change was
unintentional, but that this needed to be investigated.
Attached is a reproducer:
$ tar -zxvf ./reproducer.tar.gz
reproducer/
reproducer/test.sh
reproducer/driver.sh
reproducer/profile
$ cd reproducer && ./driver.sh
Loading apparmor profiles...
...
ix should scrub: FAIL: ix scrubs
Ux should scrub: PASS
ux should not scrub: PASS
FAIL
[1]
The separate reproducer is:
$ cat ./profile
#include <tunables/global>
profile aaexec-ix {
#include <abstractions/base>
#include <abstractions/bash>
#include <abstractions/perl>
/bin/dash ixr,
/bin/grep ixr,
/**/test.sh r,
@{PROC}/*/attr/exec rw,
change_profile -> unconfined,
/usr/{,s}bin/aa-exec ixr,
}
+ $ cat ./test.sh
+ #!/bin/sh
+ set -e
+
+ export LD_LIBRARY_PATH="foo"
+ aa-exec -p unconfined -- /bin/dash -c 'env' | grep LD_
+
+
$ sudo apparmor_parser -r ./profile
$ export LD_LIBRARY_PATH=foo
Then on (at least) 4.4 and higher:
$ aa-exec -p aaexec-ix -- ./test.sh | grep foo
[1]
$
and on (at least) 3.13 and below:
$ aa-exec -p aaexec-ix -- ./test.sh | grep foo
LD_LIBRARY_PATH=foo
$
- Importantly, this behavior does *NOT* affect normal fork/exec. Eg, if
- run '/bin/sh -c env | grep LD_' without the aa-exec, everything works
- fine. The aa-exec call is needed to demonstrate the bug.
+ Note: I also tested the perl aa-exec on newer releases and it shows the
+ same ix scrubbing behavior as the binutils aa-exec.
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https://bugs.launchpad.net/bugs/1759346
Title:
ix scrubs environment when it shouldn't when going through aa-exec
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