linux-kernel - Re: [PATCH 01/12] Add support for indicating that the booted kernel is externally trusted

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Message-ID: <20140331144927.GA21805@xo-6d-61-c0.localdomain>
Date:	Mon, 31 Mar 2014 16:49:27 +0200
From:	Pavel Machek <pavel@....cz>
To:	Matthew Garrett <matthew.garrett@...ula.com>
Cc:	linux-kernel@...r.kernel.org, keescook@...omium.org,
	gregkh@...uxfoundation.org, hpa@...or.com,
	linux-efi@...r.kernel.org, jmorris@...ei.org,
	linux-security-module@...r.kernel.org
Subject: Re: [PATCH 01/12] Add support for indicating that the booted kernel
 is externally trusted

On Wed 2014-02-26 15:11:02, Matthew Garrett wrote:
> Provide a boolean runtime configuration option for restricting userspace's
> ability to modify the running kernel. This can be used when some external
> validation of the kernel's state has been performed.

I still don't like the idea, but...

> +Once enabled. trusted kernel support may not be disabled without rebooting
> +the system.

"enabled,"

> @@ -3091,6 +3091,14 @@ static inline void security_audit_rule_free(void *lsmrule)
>  #endif /* CONFIG_SECURITY */
>  #endif /* CONFIG_AUDIT */
>  
> +#ifdef CONFIG_SECURITY_TRUSTED_KERNEL
> +extern bool get_trusted_kernel(void);
> +extern int set_trusted_kernel(bool new_trusted_kernel);
> +#else
> +static inline bool get_trusted_kernel(void) { return 0; }
> +static inline int set_trusted_kernel(bool new_trusted_kernel) { return 0; }
> +#endif /* CONFIG_TRUSTED_KERNEL */

comment does not match ifdef. (And _SECURITY is really superfluous here, maybe shorter
option would be better?)

> +	length = -EINVAL;
> +	if (sscanf(page, "%d", &new_trusted_kernel) != 1)
> +		goto out;
> +
> +	length = set_trusted_kernel(!!new_trusted_kernel);

If someone writes 2 to the sysfs, it would be better to return einval than trying
to second guess him...

								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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