linux-kernel - Re: [PATCH ima-evm-utils v2] Add tests for MMAP_CHECK and MMAP_CHECK

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Date:   Wed, 01 Feb 2023 18:29:21 +0100
From:   Roberto Sassu <roberto.sassu@...weicloud.com>
To:     Mimi Zohar <zohar@...ux.ibm.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 v2] Add tests for MMAP_CHECK and
 MMAP_CHECK_REQPROT hooks

On Tue, 2023-01-31 at 22:02 -0500, Mimi Zohar wrote:
> Hi Roberto,
> 
> > +check_mmap() {
> > +	local hook="$1"
> > +	local arg="$2"
> > +	local test_file fowner rule result test_file_entry
> > +
> > +	echo -e "\nTest: ${FUNCNAME[0]} (hook=\"$hook\", test_mmap arg: \"$arg\")"
> > +
> > +	if ! test_file=$(mktemp -p "$PWD"); then
> > +		echo "${RED}Cannot write $test_file${NORM}"
> > +		return "$HARDFAIL"
> > +	fi
> > +
> > +	fowner="$MMAP_CHECK_FOWNER"
> > +	rule="$MEASURE_MMAP_CHECK_RULE"
> > +
> > +	if [ "$hook" = "MMAP_CHECK_REQPROT" ]; then
> > +		fowner="$MMAP_CHECK_REQPROT_FOWNER"
> > +		rule="$MEASURE_MMAP_CHECK_REQPROT_RULE"
> > +	fi
> > +
> > +	if ! chown "$fowner" "$test_file"; then
> > +		echo "${RED}Cannot change owner of $test_file${NORM}"
> > +		return "$HARDFAIL"
> > +	fi
> > +
> > +	check_load_ima_rule "$rule"
> > +	result=$?
> > +	if [ $result -ne "$OK" ]; then
> > +		return $result
> > +	fi
> > +
> > +	test_mmap "$test_file" "$arg"
> > +
> > +	if [ "$TFAIL" != "yes" ]; then
> > +		echo -n "Result (expect found): "
> > +	else
> > +		echo -n "Result (expect not found): "
> > +	fi
> > +
> > +	test_file_entry=$(awk '$5 == "'"$test_file"'"' < /sys/kernel/security/ima/ascii_runtime_measurements)
> > +	if [ -z "$test_file_entry" ]; then
> > +		echo "not found"
> > +		return "$FAIL"
> > +	fi
> 
> Using temporary files should prevent having multiple records.  Having a
> verbose option to show the actual matching measurement list record
> would be nice.
> 
> > +
> > +	echo "found"
> > +	return "$OK"
> > +}
> > +
> 
> 
> > +
> > +# Run in the new environment if TST_ENV is set.
> > +_run_env "$TST_KERNEL" "$PWD/$(basename "$0")" "TST_ENV=$TST_ENV TST_KERNEL=$TST_KERNEL PATH=$PATH LD_LIBRARY_PATH=$LD_LIBRARY_PATH VERBOSE=$VERBOSE"
> > +
> > +# Exit from the creator of the new environment.
> > +_exit_env "$TST_KERNEL"
> > +
> > +# Mount filesystems in the new environment.
> > +_init_env
> > +
> > +if [ "$(whoami)" != "root" ]; then
> > +	echo "${CYAN}This script must be executed as root${NORM}"
> > +	exit "$SKIP"
> > +fi
> > +
> > +if [ ! -f /sys/kernel/security/ima/policy ]; then
> > +	echo "${CYAN}IMA policy file not found${NORM}"
> > +	exit "$SKIP"
> > +fi
> > +
> > +if ! cat /sys/kernel/security/ima/policy &> /dev/null; then
> > +	echo "${CYAN}IMA policy file is not readable${NORM}"
> > +	exit "$SKIP"
> > +fi
> 
> An existing policy with an mmap rule would affect this test.  Check to
> see if one already exists.

Not sure about this. We are specifying the filesystem UUID and the file
owner. Should be enough to avoid interferences. Also
check_load_ima_rule() avoids duplicated rules.

Roberto

> > +
> > +if [ -n "$TST_KEY_PATH" ]; then
> > +	if [ "${TST_KEY_PATH:0:1}" != "/" ]; then
> > +		echo "${RED}Absolute path required for the signing key${NORM}"
> > +		exit "$FAIL"
> > +	fi
> >