linux-kernel - Re: IMA: How to manage user space signing policy with others

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Date:	Tue, 05 Mar 2013 15:40:18 -0500
From:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:	Vivek Goyal <vgoyal@...hat.com>
Cc:	Eric Paris <eparis@...isplace.org>,
	linux kernel mailing list <linux-kernel@...r.kernel.org>,
	LSM List <linux-security-module@...r.kernel.org>
Subject: Re: IMA: How to manage user space signing policy with others

On Tue, 2013-03-05 at 10:18 -0500, Vivek Goyal wrote:

> Can we do following. (Just modifying your proposal little bit).
> 
> - Implement a new policy say ima_mem_exec. This policy can vary based on
>   config options. This will be the default policy. 

Just to clarify, the default is the existing null policy.  When
'secureboot' is enabled, ima_mem_exec will be the default policy.

> - ima_mem_exec will be default policy and it can be disabled by passing
>   a command line option ima_mem_exec_disable.
> 
> - If user wants to use ima_apprase_tcb policy, they can pass two command
>   line option. (ima_mem_exec_disable  and ima_appraise_tcb).

Both aren't really needed.   Nothing changes for existing users, if
'ima_appraise_tcb' replaces the ima_mem_exec policy. 

> - Similary if user wants to put its own policy using "policy" interface,
>   they need to boot kernel with command line option "ima_mem_exec_disable".

Not a good idea, as this would be a new requirement for existing users.
Invert the logic.

> In the end, this is again "either A or B"  mechanism. Both ima_mem_exec
> and ima_appraise_tcb are not co-existing. Comand line option just enables
> choosing one over other.

Does this impact 'ima_tcb' or only 'ima_appraise_tcb'?

> The fact that we are able to replace ima_mem_exec policy using command
> line, binary loader will need a way to query IMA to find what's the
> current policy. If ima_mem_exec has been replaced, then binary loader
> will not memlock files and will not raise extra capability to binary. And
> this will disable kdump functionality on secureboot platforms. (Something
> which I don't like much).

Ok

thanks,

Mimi

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