Re: [PATCH v3] ima: add a new CONFIG for loading arch-specific policies

Every time a new architecture defines the IMA architecture specific
functions - arch_ima_get_secureboot() and arch_ima_get_policy(), the IMA
include file needs to be updated. To avoid this "noise", this patch
defines a new IMA Kconfig IMA_SECURE_AND_OR_TRUSTED_BOOT option, allowing
the different architectures to select it.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Philipp Rudo <redacted>
Cc: Michael Ellerman <mpe@ellerman.id.au>
---
v3:
* Updated and tested the patch with improvements suggested by Michael.
It now uses "imply" instead of "select". Thanks Michael.
* Have missed replacing the CONFIG_IMA in x86 and s390 with new config,
that was resulting in redefinition when the IMA_SECURE_AND_OR_TRUSTED_BOOT
is not enabled. Thanks to Mimi for recognizing the problem.

v2:
* Fixed the issue identified by Mimi. Thanks Mimi, Ard, Heiko and Michael for
discussing the fix.

  arch/powerpc/Kconfig           | 1 +
  arch/s390/Kconfig              | 1 +
  arch/s390/kernel/Makefile      | 2 +-
  arch/x86/Kconfig               | 1 +
  arch/x86/kernel/Makefile       | 2 +-
  include/linux/ima.h            | 3 +--
  security/integrity/ima/Kconfig | 8 ++++++++
  7 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 497b7d0b2d7e..a5cfde432983 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig

@@ -979,6 +979,7 @@ config PPC_SECURE_BOOT
  	bool
  	depends on PPC_POWERNV
  	depends on IMA_ARCH_POLICY
+	select IMA_SECURE_AND_OR_TRUSTED_BOOT
  	help
  	  Systems with firmware secure boot enabled need to define security
  	  policies to extend secure boot to the OS. This config allows a user

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 8abe77536d9d..4a502fbcb800 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig

@@ -195,6 +195,7 @@ config S390
  	select ARCH_HAS_FORCE_DMA_UNENCRYPTED
  	select SWIOTLB
  	select GENERIC_ALLOCATOR
+	select IMA_SECURE_AND_OR_TRUSTED_BOOT if IMA_ARCH_POLICY
  
  
  config SCHED_OMIT_FRAME_POINTER

diff --git a/arch/s390/kernel/Makefile b/arch/s390/kernel/Makefile
index 2b1203cf7be6..578a6fa82ea4 100644
--- a/arch/s390/kernel/Makefile
+++ b/arch/s390/kernel/Makefile

@@ -70,7 +70,7 @@ obj-$(CONFIG_JUMP_LABEL)	+= jump_label.o
  obj-$(CONFIG_KEXEC_FILE)	+= machine_kexec_file.o kexec_image.o
  obj-$(CONFIG_KEXEC_FILE)	+= kexec_elf.o
  
-obj-$(CONFIG_IMA)		+= ima_arch.o
+obj-$(CONFIG_IMA_SECURE_AND_OR_TRUSTED_BOOT)	+= ima_arch.o
  
  obj-$(CONFIG_PERF_EVENTS)	+= perf_event.o perf_cpum_cf_common.o
  obj-$(CONFIG_PERF_EVENTS)	+= perf_cpum_cf.o perf_cpum_sf.o

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index beea77046f9b..7f5bfaf0cbd2 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig

@@ -230,6 +230,7 @@ config X86
  	select VIRT_TO_BUS
  	select X86_FEATURE_NAMES		if PROC_FS
  	select PROC_PID_ARCH_STATUS		if PROC_FS
+	select IMA_SECURE_AND_OR_TRUSTED_BOOT	if EFI && IMA_ARCH_POLICY
  
  config INSTRUCTION_DECODER
  	def_bool y

diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 9b294c13809a..7f131ceba136 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile

@@ -155,5 +155,5 @@ ifeq ($(CONFIG_X86_64),y)
  endif
  
  ifdef CONFIG_EFI
-obj-$(CONFIG_IMA)			+= ima_arch.o
+obj-$(CONFIG_IMA_SECURE_AND_OR_TRUSTED_BOOT)	+= ima_arch.o
  endif

diff --git a/include/linux/ima.h b/include/linux/ima.h
index 1659217e9b60..aefe758f4466 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h

@@ -30,8 +30,7 @@ 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) \
-	|| defined(CONFIG_PPC_SECURE_BOOT)
+#ifdef CONFIG_IMA_SECURE_AND_OR_TRUSTED_BOOT
  extern bool arch_ima_get_secureboot(void);
  extern const char * const *arch_get_ima_policy(void);
  #else

diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig
index 3f3ee4e2eb0d..2baaf196c6d8 100644
--- a/security/integrity/ima/Kconfig
+++ b/security/integrity/ima/Kconfig

@@ -327,3 +327,11 @@ config IMA_QUEUE_EARLY_BOOT_KEYS
  	depends on IMA_MEASURE_ASYMMETRIC_KEYS
  	depends on SYSTEM_TRUSTED_KEYRING
  	default y
+
+config IMA_SECURE_AND_OR_TRUSTED_BOOT
+	bool
+	depends on IMA_ARCH_POLICY
+	default n
+	help
+	   This option is selected by architectures to enable secure and/or
+	   trusted boot based on IMA runtime policies.