[PATCH v5 4/4] IMA: Add test for kexec cmdline measurement

[Petr Vorel <pvorel@suse.cz>]

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 v4->v5:

* added kexec.policy, please check it (for lazy people, I still plan
some automatic mechanism for loading policies on CONFIG_IMA_WRITE_POLICY)

* rewritten checks in setup:
  - simplify secure boot bootctl verification
  - try dmesg when bootctl not available
  - check on failure also ^appraise.*func=KEXEC_KERNEL_CHECK policy
  - improve logic for func=KEXEC_CMDLINE check (instead of requiring
	policy to be readable check only when readable, otherwise TWARN, ...)
  - TWARN on failures in setup => TWARN is kind of error as it exit with
	non-zero, but these cases are failures thus don't hide them)

* added cleanup commit (adding helpers)

* various LTP API cleanup:
  - added setup into separate function
  - reuse test code with kexec_test()

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 | 111 ++++++++++++++++++
 4 files changed, 121 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..fbad9b425
--- /dev/null
+++ b/testcases/kernel/security/integrity/ima/tests/ima_kexec.sh
@@ -0,0 +1,111 @@
+#!/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=2
+TST_NEEDS_DEVICE=1
+TST_SETUP="setup"
+
+. ima_setup.sh
+
+IMA_KEXEC_IMAGE="${IMA_KEXEC_IMAGE:-/boot/vmlinuz-$(uname -r)}"
+
+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" = "$expected_digest" ]; then
+			return 0
+		fi
+	done < file2
+
+	return 1
+}
+
+setup()
+{
+	local cmdline="$(sed 's/BOOT_IMAGE=[^ ]* //' /proc/cmdline)"
+	local res=TBROK
+	local sb_enabled
+
+	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 '^measure.*func=KEXEC_CMDLINE'
+		res=TFAIL
+	fi
+
+	tst_res TINFO "loading kernel $IMA_KEXEC_IMAGE, cmdline: $cmdline"
+	if kexec -s -l $IMA_KEXEC_IMAGE --reuse-cmdline 2>err; then
+		ROD kexec -su
+		if ! measure "$cmdline"; then
+			if [ "$res" = TBROK ]; then
+				tst_res TWARN "policy not readable, it might not contain required measure func=KEXEC_CMDLINE"
+			fi
+			tst_brk $res "unable to find a correct entry for --reuse-cmdline"
+		fi
+		return
+	fi
+
+	if tst_cmd_available bootctl; then
+		if bootctl status 2>/dev/null | grep -qi 'Secure Boot: enabled'; then
+			sb_enabled=1
+		fi
+	elif tst_cmd_available dmesg; then
+		if dmesg | grep -qi 'Secure boot enabled'; then
+			sb_enabled=1
+		fi
+	fi
+	if [ "$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
+
+	tst_brk TBROK "kexec failed: $(cat err)"
+}
+
+kexec_test()
+{
+	local cmdline="$1"
+	local param="$2"
+
+	EXPECT_PASS_BRK kexec -s -l $IMA_KEXEC_IMAGE $param=$cmdline
+	ROD kexec -su
+	if ! measure "$cmdline"; then
+		tst_brk TFAIL "unable to find a correct entry for $param=$cmdline"
+	fi
+	tst_res TPASS "kexec cmdline for $param=$cmdline was measured correctly"
+}
+
+test()
+{
+	case $1 in
+	1) kexec_test 'foo' '--append';;
+	2) kexec_test 'bar' '--command-line';;
+	esac
+}
+
+tst_run
-- 
2.27.0