Re: context of socket passed between processes

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On Thu, Sep 8, 2022 at 9:28 AM Ondrej Mosnacek <omosnace@xxxxxxxxxx> wrote:
>
> On Thu, Sep 8, 2022 at 4:15 PM Ted Toth <txtoth@xxxxxxxxx> wrote:
> >
> > On Thu, Sep 8, 2022 at 8:43 AM Ted Toth <txtoth@xxxxxxxxx> wrote:
> > >
> > > On Wed, Sep 7, 2022 at 5:48 PM Paul Moore <paul@xxxxxxxxxxxxxx> wrote:
> > > >
> > > > On Wed, Sep 7, 2022 at 4:56 PM Dominick Grift
> > > > <dominick.grift@xxxxxxxxxxx> wrote:
> > > > > Ted Toth <txtoth@xxxxxxxxx> writes:
> > > > > > systemd uses a helper process (sd-listen) to create sockets and pass
> > > > > > their fds back to its parent. I've patched systemd to call semanage to
> > > > > > get the context for the port if it exists and create a context using
> > > > > > the returned type when calling setsockcreatecon. Everything looks
> > > > > > right i.e. the port type is retrieved, the context is created and
> > > > > > setsockcreatecon is called without errors. However 'netstat -Z' shows
> > > > > > the listening sockets type as init_t and not the type in the
> > > > > > setsockcreatecon call, is this the expected behavior? Can anyone help
> > > > > > me understand why this is happening?
> > > > >
> > > > > It is probably the context of the process listening on the port and not
> > > > > the context of the socket that binds to the port
> > > >
> > > > That's a good point, I would have thought it would have looked at the
> > > > socket itself but perhaps it is the calling process' label.  Actually,
> > > > it might be the fd's label associated with the socket; that would
> > > > explain it.  Someone would need to look at the netstat sources to
> > > > confirm.
> > >
> > > Is there an API to query the context of a socket fd?
> >
> > I wrote a client which connects and calls getpeercon and indeed the
> > context is what was set via setsockcreatecon so that's reassuring.
> > Unfortunately it seems that netstat, ss and lsof don't have a way to
> > query the context of the listening socket :( I'd like to see a
> > getsockcon function (taking an fd as its argument) added to libselinux
> > if it can be written.
>
> There is a way to see a socket's context, though it's a bit obscure:
>
> ls -ZL /proc/<PID>/fd/<FD>

Yes I did that too but it does not show the context set in the
setsockcreatecon call, only the client getpeercon returned the context
set on create.


>
> --
> Ondrej Mosnacek
> Senior Software Engineer, Linux Security - SELinux kernel
> Red Hat, Inc.
>



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