[PATCH AUTOSEL 5.6 070/606] powerpc/ima: Fix secure boot rules in ima arch policy

Sasha Levin
2020-06-09T00:38:13Z

From: Nayna Jain <nayna@linux.ibm.com>

commit fa4f3f56ccd28ac031ab275e673ed4098855fed4 upstream.

To prevent verifying the kernel module appended signature
twice (finit_module), once by the module_sig_check() and again by IMA,
powerpc secure boot rules define an IMA architecture specific policy
rule only if CONFIG_MODULE_SIG_FORCE is not enabled. This,
unfortunately, does not take into account the ability of enabling
"sig_enforce" on the boot command line (module.sig_enforce=1).

Including the IMA module appraise rule results in failing the
finit_module syscall, unless the module signing public key is loaded
onto the IMA keyring.

This patch fixes secure boot policy rules to be based on
CONFIG_MODULE_SIG instead.

Fixes: 4238fad366a6 ("powerpc/ima: Add support to initialize ima policy rules")
Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
Link: https://lore.kernel.org/r/1588342612-14532-1-git-send-email-nayna@linux.ibm.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/powerpc/kernel/ima_arch.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kernel/ima_arch.c b/arch/powerpc/kernel/ima_arch.c
index e34116255ced..957abd592075 100644
--- a/arch/powerpc/kernel/ima_arch.c
+++ b/arch/powerpc/kernel/ima_arch.c
@@ -19,12 +19,12 @@ bool arch_ima_get_secureboot(void)
* to be stored as an xattr or as an appended signature.
*
* To avoid duplicate signature verification as much as possible, the IMA
- * policy rule for module appraisal is added only if CONFIG_MODULE_SIG_FORCE
+ * policy rule for module appraisal is added only if CONFIG_MODULE_SIG
* is not enabled.
*/
static const char *const secure_rules[] = {
"appraise func=KEXEC_KERNEL_CHECK appraise_flag=check_blacklist appraise_type=imasig|modsig",
-#ifndef CONFIG_MODULE_SIG_FORCE
+#ifndef CONFIG_MODULE_SIG
"appraise func=MODULE_CHECK appraise_flag=check_blacklist appraise_type=imasig|modsig",
#endif
NULL
@@ -50,7 +50,7 @@ static const char *const secure_and_trusted_rules[] = {
"measure func=KEXEC_KERNEL_CHECK template=ima-modsig",
"measure func=MODULE_CHECK template=ima-modsig",
"appraise func=KEXEC_KERNEL_CHECK appraise_flag=check_blacklist appraise_type=imasig|modsig",
-#ifndef CONFIG_MODULE_SIG_FORCE
+#ifndef CONFIG_MODULE_SIG
"appraise func=MODULE_CHECK appraise_flag=check_blacklist appraise_type=imasig|modsig",
#endif
NULL
--
2.25.1