On 11/23/20 10:46 AM, KP Singh wrote:
On Mon, Nov 23, 2020 at 7:36 PM Yonghong Song <y...@fb.com> wrote:
On 11/23/20 10:27 AM, KP Singh wrote:
[...]
Even if a custom policy has been loaded, potentially additional
measurements unrelated to this test would be included the measurement
list. One way of limiting a rule to a specific test is by loopback
mounting a file system and defining a policy rule based on the loopback
mount unique uuid.
Thanks Mimi!
I wonder if we simply limit this to policy to /tmp and run an executable
from /tmp (like test_local_storage.c does).
The only side effect would be of extra hashes being calculated on
binaries run from /tmp which is not too bad I guess?
The builtin measurement policy (ima_policy=tcb") explicitly defines a
rule to not measure /tmp files. Measuring /tmp results in a lot of
measurements.
{.action = DONT_MEASURE, .fsmagic = TMPFS_MAGIC, .flags = IMA_FSMAGIC},
We could do the loop mount too, but I am guessing the most clean way
would be to shell out to mount from the test? Are there some other examples
of IMA we could look at?
LTP loopback mounts a filesystem, since /tmp is not being measured with
the builtin "tcb" policy. Defining new policy rules should be limited
to the loopback mount. This would pave the way for defining IMA-
appraisal signature verification policy rules, without impacting the
running system.
+Andrii
Do you think we can split the IMA test out,
have a little shell script that does the loopback mount, gets the
FS UUID, updates the IMA policy and then runs a C program?
This would also allow "test_progs" to be independent of CONFIG_IMA.
I am guessing the structure would be something similar
to test_xdp_redirect.sh
Look at sk_assign test.
sk_assign.c: if (CHECK_FAIL(system("ip link set dev lo up")))
sk_assign.c: if (CHECK_FAIL(system("ip route add local default dev lo")))
sk_assign.c: if (CHECK_FAIL(system("ip -6 route add local default dev
lo")))
sk_assign.c: if (CHECK_FAIL(system("tc qdisc add dev lo clsact")))
sk_assign.c: if (CHECK(system(tc_cmd), "BPF load failed;"
You can use "system" to invoke some bash commands to simulate a script
in the tests.
Heh, that's what I was trying to avoid, I need to parse the output to the get
the name of which loop device was assigned and then call a command like:
# blkid /dev/loop0
/dev/loop0: UUID="607ed7ce-3fad-4236-8faf-8ab744f23e01" TYPE="ext3"
Running simple commands with "system" seems okay but parsing output
is a bit too much :)
I read about:
https://man7.org/linux/man-pages/man4/loop.4.html
But I still need to create a backing file, format it and then get the UUID.
Any simple trick that I may be missing?
Maybe you can create a bash script on your prog_test files and do
system("./<>.sh"). In the shell script, you can use all the bash magic
(sed, awk, etc) to parse and store the needed result in a temp file, and
after a successful system(""), you just read that temp file. Does this work?
- KP
- KP
Mimi
