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powerpc/ima: Fix secure boot rules in ima arch policy 

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: 4238fad366 ("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
This commit is contained in:
Nayna Jain 2020-05-01 10:16:52 -04:00 committed by Michael Ellerman
parent c44dc6323c
commit fa4f3f56cc
1 changed files with 3 additions and 3 deletions
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6
arch/powerpc/kernel/ima_arch.c
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@ -19,12 +19,12 @@ bool arch_ima_get_secureboot(void)
* to be stored as an xattr or as an appended signature. * to be stored as an xattr or as an appended signature.
* *
* To avoid duplicate signature verification as much as possible, the IMA * 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. * is not enabled.
*/ */
static const char *const secure_rules[] = { static const char *const secure_rules[] = {
"appraise func=KEXEC_KERNEL_CHECK appraise_flag=check_blacklist appraise_type=imasig|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", "appraise func=MODULE_CHECK appraise_flag=check_blacklist appraise_type=imasig|modsig",
#endif #endif
NULL NULL
@ -50,7 +50,7 @@ static const char *const secure_and_trusted_rules[] = {
"measure func=KEXEC_KERNEL_CHECK template=ima-modsig", "measure func=KEXEC_KERNEL_CHECK template=ima-modsig",
"measure func=MODULE_CHECK template=ima-modsig", "measure func=MODULE_CHECK template=ima-modsig",
"appraise func=KEXEC_KERNEL_CHECK appraise_flag=check_blacklist appraise_type=imasig|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", "appraise func=MODULE_CHECK appraise_flag=check_blacklist appraise_type=imasig|modsig",
#endif #endif
NULL NULL