Messages in this thread | | | Subject | Re: [PATCH bpf-next v2 3/3] bpf: Update LSM selftests for bpf_ima_inode_hash | From | Mimi Zohar <> | Date | Mon, 23 Nov 2020 10:10:26 -0500 |
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[Cc'ing Petr Vorel]
On Mon, 2020-11-23 at 15:06 +0100, KP Singh wrote: > On Mon, Nov 23, 2020 at 2:24 PM Mimi Zohar <zohar@linux.ibm.com> wrote: > > > > On Sat, 2020-11-21 at 00:50 +0000, KP Singh wrote: > > > From: KP Singh <kpsingh@google.com> > > > > > > - Update the IMA policy before executing the test binary (this is not an > > > override of the policy, just an append that ensures that hashes are > > > calculated on executions). > > > > Assuming the builtin policy has been replaced with a custom policy and > > CONFIG_IMA_WRITE_POLICY is enabled, then yes the rule is appended. If > > a custom policy has not yet been loaded, loading this rule becomes the > > defacto custom policy. > > > > 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.
Mimi
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