Re: [PATCH v6 4/4] IMA: Add test for kexec cmdline measurement

[Lachlan Sneff <t-josne@linux.microsoft.com>]

Looks great, thank you for working on this, Petr!

On 7/27/20 8:13 PM, Petr Vorel wrote:
> From: Lachlan Sneff <t-josne@linux.microsoft.com>
>
> IMA policy can be set to measure the command line passed in the kexec
> system call. Add a testcase that verifies that the IMA subsystem
> correctly measure the cmdline specified during a kexec.
>
> Reviewed-by: Petr Vorel <pvorel@suse.cz>
> Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
> Signed-off-by: Lachlan Sneff <t-josne@linux.microsoft.com>
> [ pvorel: improved setup, various LTP API cleanup ]
> Signed-off-by: Petr Vorel <pvorel@suse.cz>
> ---
> Changes v5->v6:
> * move --reuse-cmdline from setup to kexec_test()
>
> Sorry for the noise.
>
> Kind regards,
> Petr
>
>   runtest/ima                                   |   1 +
>   .../kernel/security/integrity/ima/README.md   |   8 ++
>   .../integrity/ima/datafiles/kexec.policy      |   1 +
>   .../security/integrity/ima/tests/ima_kexec.sh | 120 ++++++++++++++++++
>   4 files changed, 130 insertions(+)
>   create mode 100644 testcases/kernel/security/integrity/ima/datafiles/kexec.policy
>   create mode 100755 testcases/kernel/security/integrity/ima/tests/ima_kexec.sh
>
> diff --git a/runtest/ima b/runtest/ima
> index 309d47420..5f4b4a7a1 100644
> --- a/runtest/ima
> +++ b/runtest/ima
> @@ -4,4 +4,5 @@ ima_policy ima_policy.sh
>   ima_tpm ima_tpm.sh
>   ima_violations ima_violations.sh
>   ima_keys ima_keys.sh
> +ima_kexec ima_kexec.sh
>   evm_overlay evm_overlay.sh
> diff --git a/testcases/kernel/security/integrity/ima/README.md b/testcases/kernel/security/integrity/ima/README.md
> index 732cd912f..d4644ba39 100644
> --- a/testcases/kernel/security/integrity/ima/README.md
> +++ b/testcases/kernel/security/integrity/ima/README.md
> @@ -36,6 +36,14 @@ CONFIG_SYSTEM_TRUSTED_KEYS="/etc/keys/ima-local-ca.pem"
>   
>   Test also requires loaded policy with `func=KEY_CHECK`, see example in `keycheck.policy`.
>   
> +### IMA kexec test
> +
> +`ima_kexec.sh` requires loaded policy which contains `measure func=KEXEC_CMDLINE`,
> +see example in `kexec.policy`.
> +
> +The test attempts to kexec the existing running kernel image.
> +To kexec a different kernel image export `IMA_KEXEC_IMAGE=<pathname>`.
> +
>   ## EVM tests
>   
>   `evm_overlay.sh` requires a builtin IMA appraise tcb policy (e.g. `ima_policy=appraise_tcb`
> diff --git a/testcases/kernel/security/integrity/ima/datafiles/kexec.policy b/testcases/kernel/security/integrity/ima/datafiles/kexec.policy
> new file mode 100644
> index 000000000..58d66369e
> --- /dev/null
> +++ b/testcases/kernel/security/integrity/ima/datafiles/kexec.policy
> @@ -0,0 +1 @@
> +measure func=KEXEC_CMDLINE
> diff --git a/testcases/kernel/security/integrity/ima/tests/ima_kexec.sh b/testcases/kernel/security/integrity/ima/tests/ima_kexec.sh
> new file mode 100755
> index 000000000..30bbd066e
> --- /dev/null
> +++ b/testcases/kernel/security/integrity/ima/tests/ima_kexec.sh
> @@ -0,0 +1,120 @@
> +#!/bin/sh
> +# SPDX-License-Identifier: GPL-2.0-or-later
> +# Copyright (c) 2020 Microsoft Corporation
> +# Copyright (c) 2020 Petr Vorel <pvorel@suse.cz>
> +# Author: Lachlan Sneff <t-josne@linux.microsoft.com>
> +#
> +# Verify that kexec cmdline is measured correctly.
> +# Test attempts to kexec the existing running kernel image.
> +# To kexec a different kernel image export IMA_KEXEC_IMAGE=<pathname>.
> +
> +TST_NEEDS_CMDS="grep kexec sed"
> +TST_CNT=3
> +TST_NEEDS_DEVICE=1
> +TST_SETUP="setup"
> +
> +. ima_setup.sh
> +
> +IMA_KEXEC_IMAGE="${IMA_KEXEC_IMAGE:-/boot/vmlinuz-$(uname -r)}"
> +REQUIRED_POLICY='^measure.*func=KEXEC_CMDLINE'
> +
> +measure()
> +{
> +	local cmdline="$1"
> +	local algorithm digest expected_digest found
> +
> +	printf "$cmdline" > file1
> +	grep "kexec-cmdline" $ASCII_MEASUREMENTS > file2
> +
> +	while read found
> +	do
> +		algorithm=$(echo "$found" | cut -d' ' -f4 | cut -d':' -f1)
> +		digest=$(echo "$found" | cut -d' ' -f4 | cut -d':' -f2)
> +
> +		expected_digest=$(compute_digest $algorithm file1)
> +
> +		if [ "$digest" = "$expected_digest" ]; then
> +			return 0
> +		fi
> +	done < file2
> +
> +	return 1
> +}
> +
> +setup()
> +{
> +	tst_res TINFO "using kernel $IMA_KEXEC_IMAGE"
> +
> +	if [ ! -f "$IMA_KEXEC_IMAGE" ]; then
> +		tst_brk TCONF "kernel image not found, specify path in \$IMA_KEXEC_IMAGE"
> +	fi
> +
> +	if check_policy_readable; then
> +		require_ima_policy_content "$REQUIRED_POLICY"
> +		policy_readable=1
> +	fi
> +}
> +
> +kexec_failure_hint()
> +{
> +	local sb_enabled
> +
> +	if tst_cmd_available bootctl; then
> +		if bootctl status 2>/dev/null | grep -qi 'Secure Boot: enabled'; then
> +			sb_enabled=1
> +		fi
> +	elif tst_cmd_available dmesg; then
> +		if dmesg | grep -qi 'Secure boot enabled'; then
> +			sb_enabled=1
> +		fi
> +	fi
> +	if [ "$sb_enabled" ]; then
> +		tst_res TWARN "secure boot is enabled, kernel image may not be signed"
> +	fi
> +
> +	if check_ima_policy_content '^appraise.*func=KEXEC_KERNEL_CHECK'; then
> +		tst_res TWARN "'func=KEXEC_KERNEL_CHECK' appraise policy loaded, kernel image may not be signed"
> +	fi
> +}
> +
> +kexec_test()
> +{
> +	local param="$1"
> +	local cmdline="$2"
> +	local res=TFAIL
> +	local kexec_cmd
> +
> +	kexec_cmd="$param=$cmdline"
> +	if [ "$param" = '--reuse-cmdline' ]; then
> +		cmdline="$(sed 's/BOOT_IMAGE=[^ ]* //' /proc/cmdline)"
> +		kexec_cmd="$param"
> +	fi
> +
> +	kexec_cmd="kexec -s -l $IMA_KEXEC_IMAGE $kexec_cmd"
> +	tst_res TINFO "testing $kexec_cmd"
> +	if ! $kexec_cmd 2>err; then
> +		kexec_failure_hint
> +		tst_brk TBROK "kexec failed: $(cat err)"
> +	fi
> +
> +	ROD kexec -su
> +	if ! measure "$cmdline"; then
> +		if [ "$policy_readable" != 1 ]; then
> +			tst_res TWARN "policy not readable, it might not contain required policy '$REQUIRED_POLICY'"
> +			res=TBROK
> +		fi
> +		tst_brk $res "unable to find a correct measurement"
> +	fi
> +	tst_res TPASS "kexec cmdline was measured correctly"
> +}
> +
> +test()
> +{
> +	case $1 in
> +	1) kexec_test '--reuse-cmdline';;
> +	2) kexec_test '--append' 'foo';;
> +	3) kexec_test '--command-line' 'bar';;
> +	esac
> +}
> +
> +tst_run