Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH security-next v4 23/32] selinux: Remove boot parameter
To:     Kees Cook <keescook@chromium.org>
Cc:     Jordan Glover <Golden_Miller83@protonmail.ch>,
        Stephen Smalley <sds@tycho.nsa.gov>,
        Paul Moore <paul@paul-moore.com>,
        James Morris <jmorris@namei.org>,
        Casey Schaufler <casey@schaufler-ca.com>,
        Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
        "Schaufler, Casey" <casey.schaufler@intel.com>,
        linux-security-module <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>
References: <20181002005505.6112-1-keescook@chromium.org>
 <20181002005505.6112-24-keescook@chromium.org>
 <CAHC9VhQjMfH6Q+Tif8nBknZojgxrb6x+oDz4vHRiZN8rb8MZ5Q@mail.gmail.com>
 <785ef6a9-ae46-3533-0348-74bcf6f10928@tycho.nsa.gov>
 <CAGXu5jKNzG3rGUAV39D0w4txHRG3H2qU1Z1e_b+03OgycTaWqA@mail.gmail.com>
 <809f1cfd-077b-ee58-51ba-b22daf46d12b@tycho.nsa.gov>
 <QpdcE4QSCQKJqDmB2QBEGBlnlioHuRHlM0g5HF8KbHjU1zIUAOjnQ2r9EIMu3m0S2OWNR3_M_TSp_M6CVDqkp6kKuFPUvegsyDPNw1AGju4=@protonmail.ch>
 <CAGXu5jKqXNbEvPr1axQtGCCnWsGhDgjynW5u326mcx4vZ1oH8g@mail.gmail.com>
 <abe03d09-4dcb-2b02-4102-5e108d617a42@canonical.com>
 <CAGXu5jJtC1gkJ0ZKDFroL8UzvjiPfmC+6EsrzyB0j0oETdSQQg@mail.gmail.com>
From:   John Johansen <john.johansen@canonical.com>
Openpgp: preference=signencrypt
Autocrypt: addr=john.johansen@canonical.com; prefer-encrypt=mutual; keydata=
 xsFNBE5mrPoBEADAk19PsgVgBKkImmR2isPQ6o7KJhTTKjJdwVbkWSnNn+o6Up5knKP1f49E
 BQlceWg1yp/NwbR8ad+eSEO/uma/K+PqWvBptKC9SWD97FG4uB4/caomLEU97sLQMtnvGWdx
 rxVRGM4anzWYMgzz5TZmIiVTZ43Ou5VpaS1Vz1ZSxP3h/xKNZr/TcW5WQai8u3PWVnbkjhSZ
 PHv1BghN69qxEPomrJBm1gmtx3ZiVmFXluwTmTgJOkpFol7nbJ0ilnYHrA7SX3CtR1upeUpM
 a/WIanVO96WdTjHHIa43fbhmQube4txS3FcQLOJVqQsx6lE9B7qAppm9hQ10qPWwdfPy/+0W
 6AWtNu5ASiGVCInWzl2HBqYd/Zll93zUq+NIoCn8sDAM9iH+wtaGDcJywIGIn+edKNtK72AM
 gChTg/j1ZoWH6ZeWPjuUfubVzZto1FMoGJ/SF4MmdQG1iQNtf4sFZbEgXuy9cGi2bomF0zvy
 BJSANpxlKNBDYKzN6Kz09HUAkjlFMNgomL/cjqgABtAx59L+dVIZfaF281pIcUZzwvh5+JoG
 eOW5uBSMbE7L38nszooykIJ5XrAchkJxNfz7k+FnQeKEkNzEd2LWc3QF4BQZYRT6PHHga3Rg
 ykW5+1wTMqJILdmtaPbXrF3FvnV0LRPcv4xKx7B3fGm7ygdoowARAQABzR1Kb2huIEpvaGFu
 c2VuIDxqb2huQGpqbXgubmV0PsLBegQTAQoAJAIbAwULCQgHAwUVCgkICwUWAgMBAAIeAQIX
 gAUCTo0YVwIZAQAKCRAFLzZwGNXD2LxJD/9TJZCpwlncTgYeraEMeDfkWv8c1IsM1j0AmE4V
 tL+fE780ZVP9gkjgkdYSxt7ecETPTKMaZSisrl1RwqU0oogXdXQSpxrGH01icu/2n0jcYSqY
 KggPxy78BGs2LZq4XPfJTZmHZGnXGq/eDr/mSnj0aavBJmMZ6jbiPz6yHtBYPZ9fdo8btczw
 P41YeWoIu26/8II6f0Xm3VC5oAa8v7Rd+RWZa8TMwlhzHExxel3jtI7IzzOsnmE9/8Dm0ARD
 5iTLCXwR1cwI/J9BF/S1Xv8PN1huT3ItCNdatgp8zqoJkgPVjmvyL64Q3fEkYbfHOWsaba9/
 kAVtBNz9RTFh7IHDfECVaToujBd7BtPqr+qIjWFadJD3I5eLCVJvVrrolrCATlFtN3YkQs6J
 n1AiIVIU3bHR8Gjevgz5Ll6SCGHgRrkyRpnSYaU/uLgn37N6AYxi/QAL+by3CyEFLjzWAEvy
 Q8bq3Iucn7JEbhS/J//dUqLoeUf8tsGi00zmrITZYeFYARhQMtsfizIrVDtz1iPf/ZMp5gRB
 niyjpXn131cm3M3gv6HrQsAGnn8AJru8GDi5XJYIco/1+x/qEiN2nClaAOpbhzN2eUvPDY5W
 0q3bA/Zp2mfG52vbRI+tQ0Br1Hd/vsntUHO903mMZep2NzN3BZ5qEvPvG4rW5Zq2DpybWc7B
 TQROZqz6ARAAoqw6kkBhWyM1fvgamAVjeZ6nKEfnRWbkC94L1EsJLup3Wb2X0ABNOHSkbSD4
 pAuC2tKF/EGBt5CP7QdVKRGcQzAd6b2c1Idy9RLw6w4gi+nn/d1Pm1kkYhkSi5zWaIg0m5RQ
 Uk+El8zkf5tcE/1N0Z5OK2JhjwFu5bX0a0l4cFGWVQEciVMDKRtxMjEtk3SxFalm6ZdQ2pp2
 822clnq4zZ9mWu1d2waxiz+b5Ia4weDYa7n41URcBEUbJAgnicJkJtCTwyIxIW2KnVyOrjvk
 QzIBvaP0FdP2vvZoPMdlCIzOlIkPLgxE0IWueTXeBJhNs01pb8bLqmTIMlu4LvBELA/veiaj
 j5s8y542H/aHsfBf4MQUhHxO/BZV7h06KSUfIaY7OgAgKuGNB3UiaIUS5+a9gnEOQLDxKRy/
 a7Q1v9S+Nvx+7j8iH3jkQJhxT6ZBhZGRx0gkH3T+F0nNDm5NaJUsaswgJrqFZkUGd2Mrm1qn
 KwXiAt8SIcENdq33R0KKKRC80Xgwj8Jn30vXLSG+NO1GH0UMcAxMwy/pvk6LU5JGjZR73J5U
 LVhH4MLbDggD3mPaiG8+fotTrJUPqqhg9hyUEPpYG7sqt74Xn79+CEZcjLHzyl6vAFE2W0kx
 lLtQtUZUHO36afFv8qGpO3ZqPvjBUuatXF6tvUQCwf3H6XMAEQEAAcLBXwQYAQoACQUCTmas
 +gIbDAAKCRAFLzZwGNXD2D/XD/0ddM/4ai1b+Tl1jznKajX3kG+MeEYeI4f40vco3rOLrnRG
 FOcbyyfVF69MKepie4OwoI1jcTU0ADecnbWnDNHpr0SczxBMro3bnrLhsmvjunTYIvssBZtB
 4aVJjuLILPUlnhFqa7fbVq0ZQjbiV/rt2jBENdm9pbJZ6GjnpYIcAbPCCa/ffL4/SQRSYHXo
 hGiiS4y5jBTmK5ltfewLOw02fkexH+IJFrrGBXDSg6n2Sgxnn++NF34fXcm9piaw3mKsICm+
 0hdNh4afGZ6IWV8PG2teooVDp4dYih++xX/XS8zBCc1O9w4nzlP2gKzlqSWbhiWpifRJBFa4
 WtAeJTdXYd37j/BI4RWWhnyw7aAPNGj33ytGHNUf6Ro2/jtj4tF1y/QFXqjJG/wGjpdtRfbt
 UjqLHIsvfPNNJq/958p74ndACidlWSHzj+Op26KpbFnmwNO0psiUsnhvHFwPO/vAbl3RsR5+
 0Ro+hvs2cEmQuv9r/bDlCfpzp2t3cK+rhxUqisOx8DZfz1BnkaoCRFbvvvk+7L/fomPntGPk
 qJciYE8TGHkZw1hOku+4OoM2GB5nEDlj+2TF/jLQ+EipX9PkPJYvxfRlC6dK8PKKfX9KdfmA
 IcgHfnV1jSn+8yH2djBPtKiqW0J69aIsyx7iV/03paPCjJh7Xq9vAzydN5U/UA==
Organization: Canonical
Message-ID: <125243f2-8532-c0c0-0b0e-d28b3ecb910e@canonical.com>
Date:   Tue, 2 Oct 2018 12:47:53 -0700
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101
 Thunderbird/52.9.1
MIME-Version: 1.0
In-Reply-To: <CAGXu5jJtC1gkJ0ZKDFroL8UzvjiPfmC+6EsrzyB0j0oETdSQQg@mail.gmail.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-GB
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 10/02/2018 12:17 PM, Kees Cook wrote:
> On Tue, Oct 2, 2018 at 11:57 AM, John Johansen
> <john.johansen@canonical.com> wrote:
>> Under the current scheme
>>
>> lsm.enabled=selinux
>>
>> could actually mean selinux,yama,loadpin,something_else are
>> enabled. If we extend this behavior to when full stacking lands
>>
>> lsm.enabled=selinux,yama
>>
>> might mean selinux,yama,apparmor,loadpin,something_else
>>
>> and what that list is will vary from kernel to kernel, which I think
>> is harder for the user than the lsm.enabled list being what is
>> actually enabled at boot
> 
> Ah, I think I missed this in your earlier emails. What you don't like
> here is that "lsm.enable=" is additive. You want it to be explicit.
> 
> Are you okay with lsm.order= having fallback?
> 

yeah, if we are going to separate order, fallbacks are fine for
anything that isn't specified.

I am still not convinced that separating order from enablement is
right, but its generally something a user should care about so I can
live with it.

> The situation we were trying to solve was with new LSMs getting
> implicitly disabled if someone is booting with an explicit list. For
> example:
> 
> lsm.enable=yama,apparmor
> 
> means when "landlock" gets added to the kernel, it will be implicitly disabled.
> 

And here is the point of contention, I wouldn't call that implicitly
disabled. The user explicitly selected a set of LSMs to enable. Having
other LSMs enable when they aren't specified is confusing to a user,
as now they have to consider what is enabled by default in the
Kconfig.

I think requiring distros/builders to consider Kconfig options is
fine, but its a lot higher hurdle for regular users.


>> If we have to have multiple kernel parameter, I prefer a behvior where
>> if you hav conflicting kernel parameters specified
>>
>>   apparmor=0 lsm.enabled=apparmor
>>
>> that the conflict is logged and the lsm is left disabled, as I think
>> it is easier for users to understand than the overrides scheme of v3,
>> and sans logging of the conflict is effectively what we had in the
>> past
>>
>>   apparmor=0 security=apparmor
>> or
>>   apparmor=1 security=selinux
>>
>> would result in apparmor being disabed
> 
> Okay, so for this part you want per-LSM boot param to have priority
> (which seems to match SELinux's concerns), possibly logging the

hrmmm I wouldn't call it priority :)

If you look at the above logic its a boolean AND operation. The LSM is
only enabled if $LSM=1 AND security=$LSM all other combinations result
in $LSM being disabled

> conflict, but still accepting the apparmor= and selinux= state.

logging is nice for the user but certainly isn't required and is more
than we are doing today

> security= would still driving initialization ordering (so I think the
> behavior I have in the series would be correct).
> 
>> That being said I get we have a mess currently, and there really
>> doesn't seem to be a good way to fix it. I think getting this right
>> for the user is important enough that I am willing to break current
>> apparmor userspace api. While apparmor=0 is documented we have also
>> documented security=X for years and apparmor=0 isn't used too often
>> so I think we can drop it to help clean this mess up abit.
>>
>> I am not going to Nak, or block on v3 behavior if that is considered
>> the best path forward after this discussion/rant.
> 
> I could define CONFIG_LSM_ENABLE as being "additive" to
> SECURITY_APPARMOR_BOOTPARAM_VALUE and
> SECURITY_SELINUX_BOOTPARAM_VALUE?
> 

Oh sure lets deal with my complaint about too many ways to configure
this beast by adding yet another config option :P

seriously though, please no. That just adds another layer of confusion
even if it is only being foisted on the distro/builder