Re: [PATCH v3 2/2] selftests/kexec: enable lockdown tests

Hi Coiby,

On Fri, 2022-12-30 at 14:58 +0800, Coiby Xu wrote:

When lockdown is enabled, kexec_load syscall should always fail.

For kexec_file_load, when lockdown is enabled, it should

• fail of missing PE signature when KEXEC_SIG is enabled
• fail of missing IMA signature when KEXEC_SIG is disabled

Appended kernel image signatures are supported, but differently on powerpc and s390. For s390, KEXEC_SIG is enabled. For completeness the above statements should reflect appended signatures.

Before this patch, test_kexec_load.sh fails (false positive) and test_kexec_file_load.sh fails without a reason when lockdown enabled and KEXEC_SIG disabled,

# kexec_load failed [FAIL]
not ok 1 selftests: kexec: test_kexec_load.sh # exit=1
# kexec_file_load failed [PASS]
ok 2 selftests: kexec: test_kexec_file_load.sh

After this patch, test_kexec_load.sh succeeds and test_kexec_file_load.sh fails with the correct reason when lockdown enabled and KEXEC_SIG disabled,

# kexec_load failed [PASS]
ok 1 selftests: kexec: test_kexec_load.sh
# kexec_file_load failed (missing IMA sig) [PASS]
ok 2 selftests: kexec: test_kexec_file_load.sh

Cc: kexec@lists.infradead.org Cc: linux-integrity@vger.kernel.org Suggested-by: Mimi Zohar zohar@linux.ibm.com Signed-off-by: Coiby Xu coxu@redhat.com

---

.../selftests/kexec/kexec_common_lib.sh | 16 +++++++++++ .../selftests/kexec/test_kexec_file_load.sh | 27 +++++++++++++++++++ .../selftests/kexec/test_kexec_load.sh | 12 ++++++--- 3 files changed, 52 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/kexec/kexec_common_lib.sh b/tools/testing/selftests/kexec/kexec_common_lib.sh index 641ef05863b2..06c298b46788 100755 --- a/tools/testing/selftests/kexec/kexec_common_lib.sh +++ b/tools/testing/selftests/kexec/kexec_common_lib.sh @@ -110,6 +110,22 @@ get_secureboot_mode() return $secureboot_mode; } +is_lockdown_enabled() +{

• local ret=0
• if [ -f /sys/kernel/security/lockdown ] \

•     && ! grep -qs "\[none\]" /sys/kernel/security/lockdown; then
  

• ret=1
  

• fi
• if [ $ret -eq 0 ]; then

• log_info "lockdown not enabled"
  

• fi
• return $ret

+}

require_root_privileges() { if [ $(id -ru) -ne 0 ]; then diff --git a/tools/testing/selftests/kexec/test_kexec_file_load.sh b/tools/testing/selftests/kexec/test_kexec_file_load.sh index c9ccb3c93d72..790f96938083 100755 --- a/tools/testing/selftests/kexec/test_kexec_file_load.sh +++ b/tools/testing/selftests/kexec/test_kexec_file_load.sh @@ -139,6 +139,16 @@ kexec_file_load_test() log_fail "$succeed_msg (missing IMA sig)" fi

• if [ $lockdown -eq 1 ] && [ $kexec_sig_enabled -eq 1 ] \
  

•      && [ $pe_signed -eq 0 ]; then
  

• 	log_fail "$succeed_msg (missing PE sig)"
  

• fi
  

CONFIG_KEXEC_SIG being enabled does not require signature verification to be enforced. When the CONFIG_IMA_ARCH_POLICY is enabled, IMA requires kexec signature verification. Also on s390, CONFIG_KEXEC_SIG verifies an appended signature, not a PE signature. Instead of the "missing PE sig" message, perhaps indicate lockdown requires kexec signature verification.

• if [ $lockdown -eq 1 ] && [ $kexec_sig_enabled -eq 0 ] && [ $ima_signed -eq 0 ] \
  

•      && [ $ima_modsig -eq 0 ]; then
  

• 	log_fail "$succeed_msg (missing IMA sig)"
  

• fi
  

Similarly, only if IMA is enabled and requires the kexec signature verficiation should this message be emitted. Perhaps a single generic lockdown message would be sufficient for both.

if [ $pe_sig_required -eq 0 ] && [ $ima_appraise -eq 1 ] \
    && [ $ima_sig_required -eq 0 ] && [ $ima_signed -eq 0 ] \
           && [ $ima_read_policy -eq 0 ]; then

@@ -181,6 +191,16 @@ kexec_file_load_test() log_pass "$failed_msg (possibly missing IMA sig)" fi

• if [ $lockdown -eq 1 ] && [ $kexec_sig_enabled -eq 1 ] \

•    && [ $pe_signed -eq 0 ]; then
  

• log_pass "$failed_msg (missing PE sig)"
  

• fi
• if [ $lockdown -eq 1 ] && [ $kexec_sig_enabled -eq 0 ] \

•    && [ $ima_signed -eq 0 ] && [ $ima_modsig -eq 0 ]; then
  

• log_pass "$failed_msg (missing IMA sig)"
  

• fi

Similar comments as above.