linux-kernel - Re: [PATCH ima-evm-utils v5] Add tests for MMAP_CHECK and MMAP_CHECK

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Message-ID: <cd21f0d2a65f9673a0abe7f0a7219d5f1fe55911.camel@linux.ibm.com>
Date:   Mon, 06 Feb 2023 08:20:16 -0500
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Roberto Sassu <roberto.sassu@...weicloud.com>,
        dmitry.kasatkin@...il.com, jmorris@...ei.org, serge@...lyn.com
Cc:     linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, stefanb@...ux.ibm.com,
        viro@...iv.linux.org.uk, pvorel@...e.cz,
        Roberto Sassu <roberto.sassu@...wei.com>
Subject: Re: [PATCH ima-evm-utils v5] Add tests for MMAP_CHECK and
 MMAP_CHECK_REQPROT hooks

On Fri, 2023-02-03 at 13:56 +0100, Roberto Sassu wrote:
> From: Roberto Sassu <roberto.sassu@...wei.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@...wei.com>

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

> +
> +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=/ && ...

Mimi