linux-kernel - Re: [PATCH V2 07/10] Secure boot: Add a dummy kernel parameter that will switch on Secure Boot mode

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Message-ID: <20120928032000.GB5478@sergelap>
Date:	Thu, 27 Sep 2012 22:20:00 -0500
From:	Serge Hallyn <serge.hallyn@...onical.com>
To:	Matthew Garrett <mjg@...hat.com>
Cc:	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org, linux-efi@...r.kernel.org,
	Josh Boyer <jwboyer@...hat.com>
Subject: Re: [PATCH V2 07/10] Secure boot: Add a dummy kernel parameter that
 will switch on Secure Boot mode

Quoting Matthew Garrett (mjg@...hat.com):
> From: Josh Boyer <jwboyer@...hat.com>
> 
> This forcibly drops CAP_COMPROMISE_KERNEL from both cap_permitted and cap_bset
> in the init_cred struct, which everything else inherits from.  This works on
> any machine and can be used to develop even if the box doesn't have UEFI.
> 
> Signed-off-by: Josh Boyer <jwboyer@...hat.com>

Acked-by: Serge E. Hallyn <serge.hallyn@...ntu.com>

> ---
>  kernel/cred.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/kernel/cred.c b/kernel/cred.c
> index de728ac..7e6e83f 100644
> --- a/kernel/cred.c
> +++ b/kernel/cred.c
> @@ -623,6 +623,23 @@ void __init cred_init(void)
>  				     0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
>  }
>  
> +void __init secureboot_enable()
> +{
> +	pr_info("Secure boot enabled\n");
> +	cap_lower((&init_cred)->cap_bset, CAP_COMPROMISE_KERNEL);
> +	cap_lower((&init_cred)->cap_permitted, CAP_COMPROMISE_KERNEL);
> +}
> +
> +/* Dummy Secure Boot enable option to fake out UEFI SB=1 */
> +static int __init secureboot_enable_opt(char *str)
> +{
> +	int sb_enable = !!simple_strtol(str, NULL, 0);
> +	if (sb_enable)
> +		secureboot_enable();
> +	return 1;
> +}
> +__setup("secureboot_enable=", secureboot_enable_opt);
> +
>  /**
>   * prepare_kernel_cred - Prepare a set of credentials for a kernel service
>   * @daemon: A userspace daemon to be used as a reference
> -- 
> 1.7.11.4
> 
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