Re: [PATCH v3 3/3] powerpc: Add support to initialize ima policy rules

[Satheesh Rajendran]

On Mon, Jun 10, 2019 at 04:33:57PM -0400, Nayna Jain wrote:
> PowerNV secure boot relies on the kernel IMA security subsystem to
> perform the OS kernel image signature verification. Since each secure
> boot mode has different IMA policy requirements, dynamic definition of
> the policy rules based on the runtime secure boot mode of the system is
> required. On systems that support secure boot, but have it disabled,
> only measurement policy rules of the kernel image and modules are
> defined.
> 
> This patch defines the arch-specific implementation to retrieve the
> secure boot mode of the system and accordingly configures the IMA policy
> rules.
> 
> This patch provides arch-specific IMA policies if PPC_SECURE_BOOT
> config is enabled.
> 
> Signed-off-by: Nayna Jain <nayna@xxxxxxxxxxxxx>
> ---
>  arch/powerpc/Kconfig           | 14 +++++++++
>  arch/powerpc/kernel/Makefile   |  1 +
>  arch/powerpc/kernel/ima_arch.c | 54 ++++++++++++++++++++++++++++++++++
>  include/linux/ima.h            |  3 +-
>  4 files changed, 71 insertions(+), 1 deletion(-)
>  create mode 100644 arch/powerpc/kernel/ima_arch.c

Hi,

This series failed to build against linuxppc/merge tree with `ppc64le_defconfig`,

arch/powerpc/platforms/powernv/secboot.c:14:6: error: redefinition of 'get_powerpc_sb_mode'
   14 | bool get_powerpc_sb_mode(void)
      |      ^~~~~~~~~~~~~~~~~~~
In file included from arch/powerpc/platforms/powernv/secboot.c:11:
./arch/powerpc/include/asm/secboot.h:15:20: note: previous definition of 'get_powerpc_sb_mode' was here
   15 | static inline bool get_powerpc_sb_mode(void)
      |                    ^~~~~~~~~~~~~~~~~~~
make[3]: *** [scripts/Makefile.build:278: arch/powerpc/platforms/powernv/secboot.o] Error 1
make[3]: *** Waiting for unfinished jobs....
make[2]: *** [scripts/Makefile.build:489: arch/powerpc/platforms/powernv] Error 2
make[1]: *** [scripts/Makefile.build:489: arch/powerpc/platforms] Error 2
make: *** [Makefile:1071: arch/powerpc] Error 2
make: *** Waiting for unfinished jobs....

Regards,
-Satheesh

> 
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 8c1c636308c8..9de77bb14f54 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -902,6 +902,20 @@ config PPC_MEM_KEYS
> 
>  	  If unsure, say y.
> 
> +config PPC_SECURE_BOOT
> +	prompt "Enable PowerPC Secure Boot"
> +	bool
> +	default n
> +	depends on PPC64
> +	depends on OPAL_SECVAR
> +	depends on IMA
> +	depends on IMA_ARCH_POLICY
> +	help
> +	  Linux on POWER with firmware secure boot enabled needs to define
> +	  security policies to extend secure boot to the OS.This config
> +	  allows user to enable OS Secure Boot on PowerPC systems that
> +	  have firmware secure boot support.
> +
>  endmenu
> 
>  config ISA_DMA_API
> diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
> index 0ea6c4aa3a20..75c929b41341 100644
> --- a/arch/powerpc/kernel/Makefile
> +++ b/arch/powerpc/kernel/Makefile
> @@ -131,6 +131,7 @@ ifdef CONFIG_IMA
>  obj-y				+= ima_kexec.o
>  endif
>  endif
> +obj-$(CONFIG_PPC_SECURE_BOOT)	+= ima_arch.o
> 
>  obj-$(CONFIG_AUDIT)		+= audit.o
>  obj64-$(CONFIG_AUDIT)		+= compat_audit.o
> diff --git a/arch/powerpc/kernel/ima_arch.c b/arch/powerpc/kernel/ima_arch.c
> new file mode 100644
> index 000000000000..1767bf6e6550
> --- /dev/null
> +++ b/arch/powerpc/kernel/ima_arch.c
> @@ -0,0 +1,54 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2019 IBM Corporation
> + * Author: Nayna Jain <nayna@xxxxxxxxxxxxx>
> + *
> + * ima_arch.c
> + *      - initialize ima policies for PowerPC Secure Boot
> + */
> +
> +#include <linux/ima.h>
> +#include <asm/secboot.h>
> +
> +bool arch_ima_get_secureboot(void)
> +{
> +	bool sb_mode;
> +
> +	sb_mode = get_powerpc_sb_mode();
> +	if (sb_mode)
> +		return true;
> +	else
> +		return false;
> +}
> +
> +/*
> + * File signature verification is not needed, include only measurements
> + */
> +static const char *const default_arch_rules[] = {
> +	"measure func=KEXEC_KERNEL_CHECK template=ima-modsig",
> +	"measure func=MODULE_CHECK template=ima-modsig",
> +	NULL
> +};
> +
> +/* Both file signature verification and measurements are needed */
> +static const char *const sb_arch_rules[] = {
> +	"measure func=KEXEC_KERNEL_CHECK template=ima-modsig",
> +	"measure func=MODULE_CHECK template=ima-modsig",
> +	"appraise func=KEXEC_KERNEL_CHECK appraise_type=imasig|modsig template=ima-modsig",
> +#if !IS_ENABLED(CONFIG_MODULE_SIG)
> +	"appraise func=MODULE_CHECK appraise_type=imasig|modsig template=ima-modsig",
> +#endif
> +	NULL
> +};
> +
> +/*
> + * On PowerPC, file measurements are to be added to the IMA measurement list
> + * irrespective of the secure boot state of the system. Signature verification
> + * is conditionally enabled based on the secure boot state.
> + */
> +const char *const *arch_get_ima_policy(void)
> +{
> +	if (IS_ENABLED(CONFIG_IMA_ARCH_POLICY) && arch_ima_get_secureboot())
> +		return sb_arch_rules;
> +	return default_arch_rules;
> +}
> diff --git a/include/linux/ima.h b/include/linux/ima.h
> index fd9f7cf4cdf5..a01df076ecae 100644
> --- a/include/linux/ima.h
> +++ b/include/linux/ima.h
> @@ -31,7 +31,8 @@ extern void ima_post_path_mknod(struct dentry *dentry);
>  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
> -- 
> 2.20.1
>