linux-kernel - Re: [PATCH v2 5/5] selftests/ima: loading kernel modules

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Message-ID: <20190228223255.GE20335@dell5510>
Date:   Thu, 28 Feb 2019 23:32:55 +0100
From:   Petr Vorel <pvorel@...e.cz>
To:     Mimi Zohar <zohar@...ux.ibm.com>
Cc:     linux-kselftest@...r.kernel.org, Shuah Khan <shuah@...nel.org>,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 5/5] selftests/ima: loading kernel modules

Hi Mimi,

> While the appended kernel module signature can be verified, when loading
> a kernel module via either the init_module or the finit_module syscall,
> verifying the IMA signature requires access to the file descriptor,
> which is only available via the finit_module syscall.  As "modprobe"
> does not provide a flag allowing the syscall - init_module or
> finit_module - to be specified, this patch does not load a kernel
> module.

> This test simply verifies that on secure boot enabled systems with
> "CONFIG_IMA_ARCH_POLICY" configured, that at least an appended kernel
> module signature or an IMA signature is required based on the Kconfig
> and the runtime IMA policy.

> Signed-off-by: Mimi Zohar <zohar@...ux.ibm.com>
Reviewed-by: Petr Vorel <pvorel@...e.cz>

...
> diff --git a/tools/testing/selftests/ima/test_kernel_module.sh b/tools/testing/selftests/ima/test_kernel_module.sh
...
> +# Are appended signatures required?
> +if [ -e /sys/module/module/parameters/sig_enforce ]; then
> +	sig_enforce=$(cat /sys/module/module/parameters/sig_enforce)
> +	if [ $sig_enforce = "Y" ]; then
> +		log_pass "appended kernel module signature required"
> +	fi
> +fi
Another possible helper [1]:
is_enabled() # or sysfs_enabled
{
	[ -f "$1" ] && [ "$(cat $1)" = "Y" -o "$(cat $1)" = "1" ]
}

is_enabled /sys/module/module/parameters/sig_enforce && \
	log_pass "appended kernel module signature required"

...


Kind regards,
Petr

[1] https://github.com/linux-test-project/ltp/blob/master/ver_linux#L30