lkml.org 
[lkml]   [2020]   [Mar]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH bpf-next v7 4/8] bpf: lsm: Implement attach, detach and execution
From
Date
On 3/27/20 8:41 AM, KP Singh wrote:
> On 27-Mär 08:27, Stephen Smalley wrote:
>> On 3/26/20 8:24 PM, James Morris wrote:
>>> On Thu, 26 Mar 2020, KP Singh wrote:
>>>
>>>> +int bpf_lsm_verify_prog(struct bpf_verifier_log *vlog,
>>>> + const struct bpf_prog *prog)
>>>> +{
>>>> + /* Only CAP_MAC_ADMIN users are allowed to make changes to LSM hooks
>>>> + */
>>>> + if (!capable(CAP_MAC_ADMIN))
>>>> + return -EPERM;
>>>> +
>>>
>>> Stephen, can you confirm that your concerns around this are resolved
>>> (IIRC, by SELinux implementing a bpf_prog callback) ?
>>
>> I guess the only residual concern I have is that CAP_MAC_ADMIN means
>> something different to SELinux (ability to get/set file security contexts
>> unknown to the currently loaded policy), so leaving the CAP_MAC_ADMIN check
>> here (versus calling a new security hook here and checking CAP_MAC_ADMIN in
>> the implementation of that hook for the modules that want that) conflates
>> two very different things. Prior to this patch, there are no users of
>> CAP_MAC_ADMIN outside of individual security modules; it is only checked in
>> module-specific logic within apparmor, safesetid, selinux, and smack, so the
>> meaning was module-specific.
>
> As we had discussed, We do have a security hook as well:
>
> https://lore.kernel.org/bpf/20200324180652.GA11855@chromium.org/
>
> The bpf_prog hook which can check for BPF_PROG_TYPE_LSM and implement
> module specific logic for LSM programs. I thougt that was okay?
>
> Kees was in favor of keeping the CAP_MAC_ADMIN check here:
>
> https://lore.kernel.org/bpf/202003241133.16C02BE5B@keescook
>
> If you feel strongly and Kees agrees, we can remove the CAP_MAC_ADMIN
> check here, but given that we already have a security hook that meets
> the requirements, we probably don't need another one.

I would favor removing the CAP_MAC_ADMIN check here, and implementing it
in a bpf_prog hook for Smack and AppArmor if they want that. SELinux
would implement its own check in its existing bpf_prog hook.



\
 
 \ /
  Last update: 2020-03-27 14:43    [W:0.100 / U:11.360 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site