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Subject: Re: [PATCH security-next v2 26/26] LSM: Add all exclusive LSMs to
 ordered initialization
To:     Kees Cook <keescook@chromium.org>
Cc:     Casey Schaufler <casey@schaufler-ca.com>,
        James Morris <jmorris@namei.org>,
        Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
        Paul Moore <paul@paul-moore.com>,
        Stephen Smalley <sds@tycho.nsa.gov>,
        "Schaufler, Casey" <casey.schaufler@intel.com>,
        LSM <linux-security-module@vger.kernel.org>,
        Jonathan Corbet <corbet@lwn.net>,
        "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
        linux-arch <linux-arch@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
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From:   John Johansen <john.johansen@canonical.com>
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Organization: Canonical
Message-ID: <74ecd4ec-491b-93d7-4e3f-46f92121130b@canonical.com>
Date:   Thu, 20 Sep 2018 19:14:47 -0700
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On 09/20/2018 07:05 PM, Kees Cook wrote:
> On Thu, Sep 20, 2018 at 6:39 PM, John Johansen
> <john.johansen@canonical.com> wrote:
>> On 09/20/2018 06:10 PM, Casey Schaufler wrote:
>>> On 9/20/2018 5:45 PM, Kees Cook wrote:
>>>> On Thu, Sep 20, 2018 at 5:25 PM, Casey Schaufler <casey@schaufler-ca.com> wrote:
>>>>> On 9/20/2018 9:23 AM, Kees Cook wrote:
>>>>>>  config LSM_ORDER
>>>>>>       string "Default initialization order of builtin LSMs"
>>>>>> -     default "yama,loadpin,integrity"
>>>>>> +     default "yama,loadpin,integrity,selinux,smack,tomoyo,apparmor"
>>>>> If I want to compile all the major modules into my kernel and use
>>>>> AppArmor by default would I use
>>>>>
>>>>>         default "yama,loadpin,integrity,apparmor,selinux,smack,tomoyo"
>>>>>
>>>>> or
>>>>>
>>>>>         default "yama,loadpin,integrity,apparmor"
>>>> I was expecting the former, but the latter will have the same result.
>>
>> t find having the two be equivalent violates expectations. At least
>> when considering the end goal of full/extreme stacking, its trivially
>> the same with current major lsms being exclusive
> 
> This mixes "enablement" with "ordering", though, and I think the past
> threads have shown this to be largely problematic.
> 
> However, with CONFIG_LSM_ENABLED, we get the effect you're looking for, IIUC.

no, I was just stating in a world where we have full stacking those two
are not equivalent, as I would assume the order of any lsm not listed
may end up being different.

> 
>>>>> When we have "blob-sharing" how could I compile in tomoyo,
>>>>> but exclude it without a boot line option?
>>>> Ooh, yes, this series has no way to do that. Perhaps
>>>> CONFIG_LSM_DISABLE in the same form as CONFIG_LSM_ORDER? I would
>>>> totally remove LoadPin's CONFIG for this in favor it.
>>>
>>> I would generally prefer an optional CONFIG_LSM_ENABLE to
>>> CONFIG_LSM_DISABLE, but I understand the logic behind your
>>> approach. I would be looking for something like
>>>
>> +1 on the CONFIG_LSM_ENABLE ove DISABLE
>>
>>> CONFIG LSM_ENABLE
>>>       string "Default set of enabled LSMs"
>>>       default ""
>>>
>>> as opposed to
>>>
>>> CONFIG LSM_DISABLE
>>>       string "Default set of disabled LSMs"
>>>       default ""
>>>
>>> where an empty string is interpreted as "use 'em all"
>>> in either case.
> 
> Yes, I like CONFIG_LSM_ENABLE if "empty" means "enable all". Should
> CONFIG_LSM_ENABLE replace all the other CONFIG-based LSM
> enabling/disabling?

I don't particularly like "empty" being "enable all". With that
how would I disable all builtin lsms so that I just boot with
capability.

An option of all or even * is more explicit and leaves the empty
set to mean disable everything

> 
>>>>> When we have full stacking, how could I compile in selinux
>>>>> but exclude it?
>>>> Yup, same problem. Same suggested solution?
>>>>
>>>> Should lsm.enable/disable= also become a comma-separated list, or
>>>> should I leave it as a multi-instance thing like I have it?
>>>
>>> I prefer the multi-instance
>>>       lsm.disable=selinux lsm.disable=yama
>>> to the list
>>>       lsm.disable=selinux,yama
>>>
>>> but at this point I don't really care all that much.
>>
>> the comma separated list however is consistent with what is being
>> done for default order
> 
> Yeah, and it would match the new CONFIG_LSM_ENABLE.
> 
> FWIW, it was tedious to type "lsm.enable" and "lsm.disable" over and
> over when doing testing, so I almost prefer the comma separated list
> at the end of the day. I'll ponder this a bit.
> 
> -Kees
>