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@xxxxxxxxxxxxxxxxxxx
> Cc: linux-integrity@xxxxxxxxxxxxxxx
> Suggested-by: Mimi Zohar <zohar@xxxxxxxxxxxxx>
> Signed-off-by: Coiby Xu <coxu@xxxxxxxxxx>
> ---
> .../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.
--
thanks,
Mimi
