Re: [PATCH ima-evm-utils v5] Add tests for MMAP_CHECK and MMAP_CHECK_REQPROT hooks

On Mon, 2023-02-06 at 08:20 -0500, Mimi Zohar wrote:

On Fri, 2023-02-03 at 13:56 +0100, Roberto Sassu wrote:

quoted

From: Roberto Sassu <roberto.sassu@huawei.com>

Add tests to ensure that, after applying the kernel patch 'ima: Align
ima_file_mmap() parameters with mmap_file LSM hook', the MMAP_CHECK hook
checks the protections applied by the kernel and not those requested by the
application.

Also ensure that after applying 'ima: Introduce MMAP_CHECK_REQPROT hook',
the MMAP_CHECK_REQPROT hook checks the protections requested by the
application.

Test both with the test_mmap application that by default requests the
PROT_READ protection flag. Its syntax is:

test_mmap <file> <mode>

where mode can be:
- exec: adds the PROT_EXEC protection flag to mmap()
- read_implies_exec: calls the personality() system call with
                     READ_IMPLIES_EXEC as the first argument before mmap()
- mprotect: adds the PROT_EXEC protection flag to a memory area in addition
            to PROT_READ
- exec_on_writable: calls mmap() with PROT_EXEC on a file which has a
                    writable mapping

Check the different combinations of hooks/modes and ensure that a
measurement entry is found in the IMA measurement list only when it is
expected. No measurement entry should be found when only the PROT_READ
protection flag is requested or the matching policy rule has the
MMAP_CHECK_REQPROT hook and the personality() system call was called with
READ_IMPLIES_EXEC.

mprotect() with PROT_EXEC on an existing memory area protected with
PROT_READ should be denied (with an appraisal rule), regardless of the MMAP
hook specified in the policy. The same applies for mmap() with PROT_EXEC on
a file with a writable mapping.

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>

Thanks, Roberto.  Other than the one comment below, it looks good.

quoted

+
+if ! awk '$0 ~ /^(measure|appraise)/ && $0 !~ /fsuuid=/ && $0 !~ /fowner=/ { exit 1 }' < /sys/kernel/security/ima/policy; then
+	echo "${CYAN}IMA policy rules without fsuuid= and fowner=, cannot continue due to possible interference with the tests${NORM}"
+	exit "$SKIP"
+fi

The test should be limited to just MMAP_CHECK and MMAP_CHECK_REQPROT
policy rules.

+if ! awk '$0 ~ /^(measure|appraise)/ && $0 ~ /func=MMAP_CHECK/ && $0 !~ /fsuuid=/ && ...

Oh, yes. Better.

Thanks

Roberto