From: guido@trentalancia.com (Guido Trentalancia)
Date: Mon, 03 Sep 2012 11:26:22 +0200
Subject: [refpolicy] [PATCH v1 5/5] Udev's tables (run data) is stored
 in directories
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Message-ID: <504477BE.9020702@trentalancia.com>
To: refpolicy@oss.tresys.com
List-Id: refpolicy.oss.tresys.com

On 02/09/2012 21:51, Dominick Grift wrote:
>
>
> On Sun, 2012-09-02 at 14:06 +0200, Guido Trentalancia wrote:
>> On Wed, 2012-08-29 at 22:31 +0200, Dominick Grift wrote:
>>>
>>> On Wed, 2012-08-29 at 22:20 +0200, Dominick Grift wrote:
>>>>
>>>> On Wed, 2012-08-29 at 22:04 +0200, Dominick Grift wrote:
>>>>>
>>>>> On Wed, 2012-08-29 at 21:55 +0200, Sven Vermeulen wrote:
>>>>>> On Wed, Aug 29, 2012 at 09:37:55PM +0200, Dominick Grift wrote:
>>>>>>>> -# create udev database in /dev/.udevdb
>>>>>>>> -allow udev_t udev_tbl_t:file manage_file_perms;
>>>>>>>> +allow udev_t udev_tbl_t:dir relabelto;
>>>>>>>> +manage_dirs_pattern(udev_t, udev_tbl_t, udev_tbl_t)
>>>>>>>> +manage_files_pattern(udev_t, udev_tbl_t, udev_tbl_t)
>>>>>>>> +manage_lnk_files_pattern(udev_t, udev_tbl_t, udev_tbl_t)
>>>>>>>> +
>>>>>>>>   dev_filetrans(udev_t, udev_tbl_t, file)
>>>>>>>
>>>>>>> This doesnt make sense to me.
>>
>> [cut]
>>
>>>>>> Well, the udev code (looking at udev-182 here) has the code for relabeling
>>>>>> in it. For instance, when copy_dev_dir is called, it has
>>>>>>
>>>>>> #v+
>>>>>>                          udev_selinux_setfscreateconat(udev, dirfd(dir_to), dent->d_name, S_IFDIR|0755);
>>>>>>                          mkdirat(dirfd(dir_to), dent->d_name, 0755);
>>>>>>                          udev_selinux_resetfscreatecon(udev);
>>>>>> #v-
>>>>>>
>>>>>> I believe this is the source, but I'm no master in this. I mainly based
>>>>>> myself on the denials and errors I got. If I put in an "auditallow" to show
>>>>>> this, this is the result:
>>
>> At a quick look, the code in most recent versions (the one merged in
>> systemd) apparently has been extended even further in that direction by
>> adding a shared label.c source file.
>>
>> As for such labelling issue, since it is usually always preferable that
>> each one sticks to its own job, perhaps it can be dontaudited and then
>> the relevant "dynamic" path added to restorecond.conf ?
>>
>> The strange thing is that I am running latest udev without any of these
>> modifications (thus including the relabel permission)...

I am not 100% sure yet about the above because I still need to complete 
one more test, nevertheless I am a bit sceptic about it.

Relabelling is somewhat critical when done externally by other entities.

Also, as already pointed out, the opportunity that each one should stick 
to its own job if possible is a very good idea.

We have restorecond for setting the context of newly created files in 
paths that contain such "dynamic" files. There is no proved reason at 
the moment to think that restorecond (if started at the right time) is 
not up the job.

> I am currently rewriting udev policy as part of my project to write a
> systemd policy and i havent noticed this either yet, although it is
> hinting at it (it needs setfscreate capability and so does systemd by
> the way)
>
> I am not letting these daemons run my security though.

Yes, let's see how it goes. Perhaps we can come up with something better...

Regards,

Guido