Re: [PATCH] contrib/selinux: use regex instead of non-standard bash macro

[Danish Prakash <contact@danishpraka.sh>]

On 10/27/25 2:37 PM, Stefano Brivio wrote:
> Hi Danish,
> 
> On Mon, 27 Oct 2025 14:19:14 +0530
> Danish Prakash <contact@danishpraka.sh> wrote:
> 
>> On 10/16/25 4:26 PM, Max Chernoff wrote:
>>> Hi Stefano,
>>>
>>> On Thu, 2025-10-16 at 10:21 +0200, Stefano Brivio wrote:  
>>>> On Thu, 16 Oct 2025 13:10:41 +0530
>>>> Danish Prakash <contact@danishpraka.sh> wrote:  
>>>>> It might be possible to avoid using non-standard bash macro (%USERID),  
>>>
>>> It's not a Bash macro, it's a SELinux template. This doesn't seem to be
>>> documented anywhere (which isn't terribly surprising with SELinux), but
>>> it's defined in this file:
>>>
>>>     https://github.com/SELinuxProject/selinux/blob/ceb5b221/libsemanage/src/genhomedircon.c  
>>
>> Thanks Max, I wasn't aware of it being an SELinux template.
>>
>>>   
>>>> I wonder if
>>>> Max remembers any reason why we couldn't do this in the first place.  
>>>
>>> The Fedora SELinux policy always uses %{USERID}, and so I copied it from
>>> there:
>>>
>>>     $ grep -RnF '%{USERID}' policy/
>>>     policy/modules/contrib/dbus.fc:29:/run/user/%{USERID}/bus	-s	gen_context(system_u:object_r:session_dbusd_tmp_t,s0)
>>>     policy/modules/contrib/dbus.fc:30:/run/user/%{USERID}/dbus(/.*)? 	gen_context(system_u:object_r:session_dbusd_tmp_t,s0)
>>>     policy/modules/contrib/dbus.fc:31:/run/user/%{USERID}/dbus-1(/.*)? 	gen_context(system_u:object_r:session_dbusd_tmp_t,s0)
>>>     policy/modules/contrib/gnome.fc:25:/run/user/%{USERID}/\.orc(/.*)?		gen_context(system_u:object_r:gstreamer_home_t,s0)
>>>     policy/modules/contrib/gnome.fc:26:/run/user/%{USERID}/dconf(/.*)?	gen_context(system_u:object_r:config_home_t,s0)
>>>     policy/modules/contrib/gnome.fc:27:/run/user/%{USERID}/keyring.*	gen_context(system_u:object_r:gkeyringd_tmp_t,s0)
>>>     policy/modules/kernel/filesystem.fc:17:/run/user/%{USERID}/gvfs		-d	gen_context(system_u:object_r:fusefs_t,s0)
>>>     policy/modules/kernel/filesystem.fc:18:/run/user/%{USERID}/gvfs/.*	<<none>>
>>>     policy/modules/system/userdomain.fc:38:/run/user/%{USERID}	-d	gen_context(system_u:object_r:user_tmp_t,s0)
>>>     policy/modules/system/userdomain.fc:39:/run/user/%{USERID}/.+	<<none>>
>>>
>>>     $ grep -RnF '[0-9]+' policy/  | grep -v /dev/
>>>     policy/modules/contrib/rpm.fc:52:/usr/bin/rhn_check-[0-9]+\.[0-9]+		--	gen_context(system_u:object_r:rpm_exec_t,s0)
>>>     policy/modules/contrib/soundserver.fc:12:/run/yiff-[0-9]+\.pid	--	gen_context(system_u:object_r:soundd_var_run_t,s0)
>>>     policy/modules/kernel/devices.if:6958:##	Allow read the hfi1_[0-9]+ devices
>>>   
>>>>> diff --git a/contrib/fedora/passt.spec b/contrib/fedora/passt.spec
>>>>> index 663289f53d97..d1bcf4a74338 100644
>>>>> --- a/contrib/fedora/passt.spec
>>>>> +++ b/contrib/fedora/passt.spec
>>>>> [...]  
>>>>
>>>> At a glance, this looks like a better solution regardless of the
>>>> reported issue. It sounds too good to be true, though  
>>>
>>> I agree that it looks like a good solution, which makes me wonder why
>>> the base SELinux policies don't do it that way. The containers SELinux
>>> policy appears to do things this way
>>>
>>>     $ grep -RnF '[0-9]+'
>>>     container_selinux.8:166:	/run/user/[0-9]+/gvfs
>>>     $ grep -RnF '%{USERID}'; echo $?
>>>     1
>>>
>>> so it's probably (?) okay though.  
>>
>> That's helpful, I guess we can go ahead with this. Stefano, Paul?
> 
> Sure. But back to my question about the original problem... what was
> the original problem? :) Could it be something similar to:
> 
>   https://bugzilla.redhat.com/show_bug.cgi?id=2401764
> 
> ?

Ah, sorry about that. No, it's not a functionality issue or a bug. It
was merely a few suggestions to improve the passt SUSE package from the
SELinux team at SUSE. Here are the suggestions:

1. building twice is quite a hack, setting a hardlink as in apparmor
would probably work as well and is less confusing
2.  running restorecon would be unnecessary if the passt upstream
selinux module would not use ${USERID} in pasta.fc (gets converted to
[0-9]+ anyway)
3. there is a %selinux_requires macro in selinux-policy-devel that
likely could be used instead of listing the Requires:, but okay we dont
enforce that atm

For #1 I can see that building twice is required in this case, and
unlike apparmor which can work with hardlinks, doing the same for
SELinux isn't possible with inodes in the picture.

#2 is what this patch is about, and #3 is SUSE-exclusive which I'm
fixing in parallel.


> 
> In general, there are a bunch of current SELinux issues reported on
> Fedora/RHEL (and I assume they would be exactly the same on
> openSUSE/SLES):
> 
>   https://bugzilla.redhat.com/buglist.cgi?bug_status=__open__&columnlist=short_desc%2Cchangeddate%2Cbug_severity&component=passt&product=Fedora
> 
> and I'm trying to find out if this change might fix some of them. Most
> of those are stuff I didn't investigate yet.
> 

Unfortunately no, I was notified of a few spec related errors from
colleagues, but I'm sure the errors would overlap, as you said. If
there's something I can help, please let me know, I'll be happy to
contribute.

regards
-- 
danishpraka.sh