On (29/11/16 10:30), Jakub Hrozek wrote:
>On Tue, Nov 29, 2016 at 10:24:03AM +0100, Fabiano Fidêncio wrote:
>> On Tue, Nov 29, 2016 at 10:01 AM, Lukas Slebodnik <[email protected]> 
>> wrote:
>> > On (28/11/16 11:27), Jakub Hrozek wrote:
>> >>On Mon, Nov 28, 2016 at 10:57:44AM +0100, Pavel Březina wrote:
>> >>> On 11/28/2016 10:47 AM, Jakub Hrozek wrote:
>> >>> > On Thu, Nov 24, 2016 at 02:33:04PM +0100, Fabiano Fidêncio wrote:
>> >>> > > The design page is done [0] and it's based on this discussion [1] we
>> >>> > > had on this very same mailing list. A pull-request with the
>> >>> > > implementation is already opened [2].
>> >>> > >
>> >>> > > [0]: 
>> >>> > > https://fedorahosted.org/sssd/wiki/DesignDocs/SocketActivatableResponders
>> >>> > > [1]: 
>> >>> > > https://lists.fedorahosted.org/archives/list/[email protected]/message/H6JOF5SGGSIJUIWYNANDA73ODHWBS7J2/
>> >>> > > [2]: https://github.com/SSSD/sssd/pull/84
>> >>> > >
>> >>> > > The full text of c&p here:
>> >>> >
>> >>> > In general looks good to me, but note that I was involved a bit with
>> >>> > Fabiano in the discussion, so my view might be tainted.
>> >>>
>> >>> I finally got to it. The design page looks good and I'll start reviewing 
>> >>> the
>> >>> patches.
>> >>>
>> >>> The only think I wonder about is whether we want to pass parameters " 
>> >>> --uid
>> >>> 0 --gid 0 --debug-to-files" or we will read the from sssd.conf? I prefer
>> >>> reading them.
>> >>>
>> >>> Also what do we use the private sockets for? It is used only for root?
>> >>
>> >>Yes, that's where we route PAM requests started by UID 0 to.
>> >>
>> > For example. The nss responder need't run as root. It does not require
>> > any extra privileges. And the privileges are dropped as soon as possible.
>> > The only issue might be with switching from root to non-root.
>> > A responder need to change owner of log files.
>> > But it could be solved with ExecStartPre in service file
>> >
>> > e.g.
>> > ExecStartPre=/usr/bin/chown sssd:sssd /var/log/sssd/sssd_nss.log
>> > ExecStart=/usr/libexec/sssd/sssd_nss --debug-to-files
>> > User=sssd
>> > Group=sssd
>> > PermissionsStartOnly=true
>> >
>> > @see the explanation of PermissionsStartOnly in man 5 systemd.service
>> 
>> I like the suggestion. But I also would like to ask which are the
>> responders that have to executed as root?
>
>I guess ideally none, especially some security certifications require
>that no code that authenticates users runs as root. But we're not there yet,
>see for example:
>    https://fedorahosted.org/sssd/ticket/3014
it iss not related to responder.
>or:
>    https://fedorahosted.org/sssd/ticket/3099
>
it is not related to responder either.

>btw now that you nuked the config changing API in IFP, it should be
>possible for IFP to drop privileges after it connects to the system bus
>(or even before? I'm really not sure anymore).
>
>Can we have a ticket to examine if we can start IFP as the sssd user?
ifp responder can be started with --uid 0 --gid 0 and not
with --unprivileged-start. We can convert to unprivileged-start
later if possible.

So far I cannot see any big issue.
Circular dependency between resolving sssd user and files provider
and be solved with hardcoded UID GID.

LS
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