linux-kernel - Re: [PATCH v4 3/3] LSM: Add context interface for proc attrs

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Message-ID: <2997f1cb-bc7e-3517-28b5-171f83888ba1@schaufler-ca.com>
Date:	Fri, 24 Jun 2016 12:56:26 -0700
From:	Casey Schaufler <casey@...aufler-ca.com>
To:	Paul Moore <paul@...l-moore.com>
Cc:	LSM <linux-security-module@...r.kernel.org>,
	James Morris <jmorris@...ei.org>,
	John Johansen <john.johansen@...onical.com>,
	Stephen Smalley <sds@...ho.nsa.gov>,
	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
	Kees Cook <keescook@...omium.org>,
	LKLM <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 3/3] LSM: Add context interface for proc attrs

On 6/24/2016 12:15 PM, Paul Moore wrote:
> On Thu, Jun 23, 2016 at 5:11 PM, Casey Schaufler <casey@...aufler-ca.com> wrote:
>> Subject: [PATCH v4 3/3] LSM: Add context interface for proc attrs
>>
>> The /proc/.../attr/current interface is used by all three
>> Linux security modules (SELinux, Smack and AppArmor) to
>> report and modify the process security attribute. This is
>> all fine when there is exactly one of these modules active
>> and the userspace code knows which it module it is.
>> It would require a major change to the "current" interface
>> to provide information about more than one set of process
>> security attributes. Instead, a "context" attribute is
>> added, which identifies the security module that the
>> information applies to. The format is:
>>
>>         lsmname='context-value'
>>
>> When multiple concurrent modules are supported the
>> /proc/.../attr/context interface will include the data
>> for all of the active modules.
>>
>>         lsmname1='context-value1'lsmname2='context-value2'
>>
>> The module specific subdirectories under attr contain context
>> entries that report the information for that specific module
>> in the same format.
> I think a delimiter between the different LSMs would be a good idea.
> A comma seems like a safe choice at the moment.

It's unnecessary and makes for more complicated code in
both directions, but everyone seems wedded to a delimiter.
I'll propose a v5 with a delimiter.

>