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powerpc/ima: Add support to initialize ima policy rules

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PowerNV systems use a Linux-based bootloader, which rely on the IMA
subsystem to enforce different secure boot modes. Since the
verification policy may differ based on the secure boot mode of the
system, the policies must be defined at runtime.

This patch implements arch-specific support to define IMA policy rules
based on the runtime secure boot mode of the system.

This patch provides arch-specific IMA policies if PPC_SECURE_BOOT
config is enabled.

Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1572492694-6520-3-git-send-email-zohar@linux.ibm.com
This commit is contained in:
Nayna Jain 2019-10-30 23:31:27 -04:00 committed by Michael Ellerman
parent 1a8916ee3a
commit 4238fad366
4 changed files with 47 additions and 2 deletions
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1
arch/powerpc/Kconfig
View File

@ -938,6 +938,7 @@ config PPC_SECURE_BOOT
prompt "Enable secure boot support"
bool
depends on PPC_POWERNV
depends on IMA_ARCH_POLICY
help
Systems with firmware secure boot enabled need to define security
policies to extend secure boot to the OS. This config allows a user

2
arch/powerpc/kernel/Makefile
View File

@ -161,7 +161,7 @@ ifneq ($(CONFIG_PPC_POWERNV)$(CONFIG_PPC_SVM),)
obj-y += ucall.o
endif
obj-$(CONFIG_PPC_SECURE_BOOT) += secure_boot.o
obj-$(CONFIG_PPC_SECURE_BOOT) += secure_boot.o ima_arch.o
# Disable GCOV, KCOV & sanitizers in odd or sensitive code
GCOV_PROFILE_prom_init.o := n

43
arch/powerpc/kernel/ima_arch.c Normal file
View File

@ -0,0 +1,43 @@
// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2019 IBM Corporation
* Author: Nayna Jain
*/
#include <linux/ima.h>
#include <asm/secure_boot.h>
bool arch_ima_get_secureboot(void)
{
return is_ppc_secureboot_enabled();
}
/*
* The "secure_rules" are enabled only on "secureboot" enabled systems.
* These rules verify the file signatures against known good values.
* The "appraise_type=imasig|modsig" option allows the known good signature
* 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
* is not enabled.
*/
static const char *const secure_rules[] = {
"appraise func=KEXEC_KERNEL_CHECK appraise_type=imasig|modsig",
#ifndef CONFIG_MODULE_SIG_FORCE
"appraise func=MODULE_CHECK appraise_type=imasig|modsig",
#endif
NULL
};
/*
* Returns the relevant IMA arch-specific policies based on the system secure
* boot state.
*/
const char *const *arch_get_ima_policy(void)
{
if (is_ppc_secureboot_enabled())
return secure_rules;
return NULL;
}

3
include/linux/ima.h
View File

@ -29,7 +29,8 @@ extern void ima_kexec_cmdline(const void *buf, int size);
extern void ima_add_kexec_buffer(struct kimage *image);
#endif
#if (defined(CONFIG_X86) && defined(CONFIG_EFI)) || defined(CONFIG_S390)
#if (defined(CONFIG_X86) && defined(CONFIG_EFI)) || defined(CONFIG_S390) \
|| defined(CONFIG_PPC_SECURE_BOOT)
extern bool arch_ima_get_secureboot(void);
extern const char * const *arch_get_ima_policy(void);
#else