Re: [PATCH v4 2/3] ima: generalize x86/EFI arch glue for other EFI architectures

[Chester Lin <clin@suse.com>]

Hi Ard,

On Mon, Nov 02, 2020 at 11:37:59PM +0100, Ard Biesheuvel wrote:
> From: Chester Lin <clin@suse.com>
> 
> Move the x86 IMA arch code into security/integrity/ima/ima_efi.c,
> so that we will be able to wire it up for arm64 in a future patch.
> 
> Co-developed-by: Chester Lin <clin@suse.com>
> Signed-off-by: Chester Lin <clin@suse.com>
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> ---
>  arch/x86/include/asm/efi.h                                     |  3 ++
>  arch/x86/kernel/Makefile                                       |  2 -
>  security/integrity/ima/Makefile                                |  4 ++
>  arch/x86/kernel/ima_arch.c => security/integrity/ima/ima_efi.c | 45 ++++++--------------
>  4 files changed, 19 insertions(+), 35 deletions(-)
> 
> diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h
> index 7673dc833232..c98f78330b09 100644
> --- a/arch/x86/include/asm/efi.h
> +++ b/arch/x86/include/asm/efi.h
> @@ -380,4 +380,7 @@ static inline void efi_fake_memmap_early(void)
>  }
>  #endif
>  
> +#define arch_ima_efi_boot_mode	\
> +	({ extern struct boot_params boot_params; boot_params.secure_boot; })
> +
>  #endif /* _ASM_X86_EFI_H */
> diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
> index 68608bd892c0..5eeb808eb024 100644
> --- a/arch/x86/kernel/Makefile
> +++ b/arch/x86/kernel/Makefile
> @@ -161,5 +161,3 @@ ifeq ($(CONFIG_X86_64),y)
>  	obj-$(CONFIG_MMCONF_FAM10H)	+= mmconf-fam10h_64.o
>  	obj-y				+= vsmp_64.o
>  endif
> -
> -obj-$(CONFIG_IMA_SECURE_AND_OR_TRUSTED_BOOT)	+= ima_arch.o
> diff --git a/security/integrity/ima/Makefile b/security/integrity/ima/Makefile
> index 67dabca670e2..2499f2485c04 100644
> --- a/security/integrity/ima/Makefile
> +++ b/security/integrity/ima/Makefile
> @@ -14,3 +14,7 @@ ima-$(CONFIG_HAVE_IMA_KEXEC) += ima_kexec.o
>  ima-$(CONFIG_IMA_BLACKLIST_KEYRING) += ima_mok.o
>  ima-$(CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS) += ima_asymmetric_keys.o
>  ima-$(CONFIG_IMA_QUEUE_EARLY_BOOT_KEYS) += ima_queue_keys.o
> +
> +ifeq ($(CONFIG_EFI),y)
> +ima-$(CONFIG_IMA_SECURE_AND_OR_TRUSTED_BOOT) += ima_efi.o
> +endif
> diff --git a/arch/x86/kernel/ima_arch.c b/security/integrity/ima/ima_efi.c
> similarity index 60%
> rename from arch/x86/kernel/ima_arch.c
> rename to security/integrity/ima/ima_efi.c
> index 7dfb1e808928..233627a9d4b8 100644
> --- a/arch/x86/kernel/ima_arch.c
> +++ b/security/integrity/ima/ima_efi.c
> @@ -5,50 +5,29 @@
>  #include <linux/efi.h>
>  #include <linux/module.h>
>  #include <linux/ima.h>
> +#include <asm/efi.h>
>  
> -extern struct boot_params boot_params;
> +#ifndef arch_ima_efi_boot_mode
> +#define arch_ima_efi_boot_mode efi_secureboot_mode_unknown

I think this should be "efi_secureboot_mode_unset" otherwise the get_sb_mode()
will never be called. The others look good to me, thanks for your help.

Regards,
Chester

> +#endif
>  
>  static enum efi_secureboot_mode get_sb_mode(void)
>  {
> -	efi_guid_t efi_variable_guid = EFI_GLOBAL_VARIABLE_GUID;
> -	efi_status_t status;
> -	unsigned long size;
> -	u8 secboot, setupmode;
> -
> -	size = sizeof(secboot);
> +	enum efi_secureboot_mode mode;
>  
>  	if (!efi_rt_services_supported(EFI_RT_SUPPORTED_GET_VARIABLE)) {
>  		pr_info("ima: secureboot mode unknown, no efi\n");
>  		return efi_secureboot_mode_unknown;
>  	}
>  
> -	/* Get variable contents into buffer */
> -	status = efi.get_variable(L"SecureBoot", &efi_variable_guid,
> -				  NULL, &size, &secboot);
> -	if (status == EFI_NOT_FOUND) {
> +	mode = efi_get_secureboot_mode(efi.get_variable);
> +	if (mode == efi_secureboot_mode_disabled)
>  		pr_info("ima: secureboot mode disabled\n");
> -		return efi_secureboot_mode_disabled;
> -	}
> -
> -	if (status != EFI_SUCCESS) {
> +	else if (mode == efi_secureboot_mode_unknown)
>  		pr_info("ima: secureboot mode unknown\n");
> -		return efi_secureboot_mode_unknown;
> -	}
> -
> -	size = sizeof(setupmode);
> -	status = efi.get_variable(L"SetupMode", &efi_variable_guid,
> -				  NULL, &size, &setupmode);
> -
> -	if (status != EFI_SUCCESS)	/* ignore unknown SetupMode */
> -		setupmode = 0;
> -
> -	if (secboot == 0 || setupmode == 1) {
> -		pr_info("ima: secureboot mode disabled\n");
> -		return efi_secureboot_mode_disabled;
> -	}
> -
> -	pr_info("ima: secureboot mode enabled\n");
> -	return efi_secureboot_mode_enabled;
> +	else
> +		pr_info("ima: secureboot mode enabled\n");
> +	return mode;
>  }
>  
>  bool arch_ima_get_secureboot(void)
> @@ -57,7 +36,7 @@ bool arch_ima_get_secureboot(void)
>  	static bool initialized;
>  
>  	if (!initialized && efi_enabled(EFI_BOOT)) {
> -		sb_mode = boot_params.secure_boot;
> +		sb_mode = arch_ima_efi_boot_mode;
>  
>  		if (sb_mode == efi_secureboot_mode_unset)
>  			sb_mode = get_sb_mode();
> -- 
> 2.17.1
>