Commit 4238fad3 authored by Nayna Jain's avatar Nayna Jain Committed by Michael Ellerman
Browse files

powerpc/ima: Add support to initialize ima policy rules 



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: default avatarNayna Jain <nayna@linux.ibm.com>
Signed-off-by: default avatarMimi Zohar <zohar@linux.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1572492694-6520-3-git-send-email-zohar@linux.ibm.com
parent 1a8916ee

arch/powerpc/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -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

arch/powerpc/kernel/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -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

arch/powerpc/kernel/ima_arch.c

0 → 100644
+43 −0
Original line number Diff line number Diff line 
// 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;

}

include/linux/ima.h

+2 −1
Original line number Diff line number Diff line
@@ -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

CRA Git | Maintained and supported by SUSTech CRA and CCSE