linux-kernel - Re: [PATCH v4 1/6] x86/ima: define arch_ima_get

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Date:   Thu, 27 Sep 2018 07:33:01 -0400
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Nayna Jain <nayna@...ux.vnet.ibm.com>,
        linux-integrity@...r.kernel.org
Cc:     linux-security-module@...r.kernel.org, linux-efi@...r.kernel.org,
        linux-kernel@...r.kernel.org, dhowells@...hat.com,
        jforbes@...hat.com, Seth Forshee <seth.forshee@...onical.com>,
        kexec <kexec@...ts.infradead.org>
Subject: Re: [PATCH v4 1/6] x86/ima: define arch_ima_get_secureboot

[Cc'ing the kexec mailing list, and Seth]

On Wed, 2018-09-26 at 17:52 +0530, Nayna Jain wrote:
> Distros are concerned about totally disabling the kexec_load syscall.
> As a compromise, the kexec_load syscall will only be disabled when
> CONFIG_KEXEC_VERIFY_SIG is configured and the system is booted with
> secureboot enabled.
> 
> This patch defines the new arch specific function called
> arch_ima_get_secureboot() to retrieve the secureboot state of the system.
> 
> Signed-off-by: Nayna Jain <nayna@...ux.vnet.ibm.com>
> Suggested-by: Seth Forshee <seth.forshee@...onical.com>

Nice!

Mimi

> ---
>  arch/x86/kernel/Makefile   |  2 ++
>  arch/x86/kernel/ima_arch.c | 17 +++++++++++++++++
>  include/linux/ima.h        |  9 +++++++++
>  3 files changed, 28 insertions(+)
>  create mode 100644 arch/x86/kernel/ima_arch.c
> 
> diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
> index 02d6f5cf4e70..f32406e51424 100644
> --- a/arch/x86/kernel/Makefile
> +++ b/arch/x86/kernel/Makefile
> @@ -149,3 +149,5 @@ ifeq ($(CONFIG_X86_64),y)
>  	obj-$(CONFIG_MMCONF_FAM10H)	+= mmconf-fam10h_64.o
>  	obj-y				+= vsmp_64.o
>  endif
> +
> +obj-$(CONFIG_IMA)			+= ima_arch.o
> diff --git a/arch/x86/kernel/ima_arch.c b/arch/x86/kernel/ima_arch.c
> new file mode 100644
> index 000000000000..bb5a88d2b271
> --- /dev/null
> +++ b/arch/x86/kernel/ima_arch.c
> @@ -0,0 +1,17 @@
> +/* SPDX-License-Identifier: GPL-2.0+ */
> +/*
> + * Copyright (C) 2018 IBM Corporation
> + */
> +#include <linux/efi.h>
> +#include <linux/ima.h>
> +
> +extern struct boot_params boot_params;
> +
> +bool arch_ima_get_secureboot(void)
> +{
> +	if (efi_enabled(EFI_BOOT) &&
> +		(boot_params.secure_boot == efi_secureboot_mode_enabled))
> +		return true;
> +	else
> +		return false;
> +}
> diff --git a/include/linux/ima.h b/include/linux/ima.h
> index 84806b54b50a..4852255aa4f4 100644
> --- a/include/linux/ima.h
> +++ b/include/linux/ima.h
> @@ -30,6 +30,15 @@ extern void ima_post_path_mknod(struct dentry *dentry);
>  extern void ima_add_kexec_buffer(struct kimage *image);
>  #endif
>  
> +#ifdef CONFIG_X86
> +extern bool arch_ima_get_secureboot(void);
> +#else
> +static inline bool arch_ima_get_secureboot(void)
> +{
> +	return false;
> +}
> +#endif
> +
>  #else
>  static inline int ima_bprm_check(struct linux_binprm *bprm)
>  {