Re: [devel] [PATCH hasher-priv v1 0/3] Make a daemon from the hasher-priv

[Arseny Maslennikov <arseny@altlinux.org>]

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On Thu, Oct 01, 2020 at 07:21:11PM +0200, Alexey Gladkov wrote:
> On Thu, Sep 17, 2020 at 04:09:35PM +0300, Arseny Maslennikov wrote:
> > On Fri, Dec 13, 2019 at 12:42:02PM +0100, Alex Gladkov wrote:
> > > From: Alexey Gladkov <legion@altlinux.org>
> > > 
> > > The hasher-priv is a SUID utility. This is not good. Separation of the
> > > server and client parts will allow us to remove SUID flag.
> > > 
> > > The separation of server and client is not intended to give clients
> > > access over the network. This separation is only necessary to distinguish
> > > privileges. Only UNIX domain socket is used.
> > > 
> > > A separate session process is created for each connected user. Each such
> > > process ends after a certain period of inactivity.
> > 
> > Thank you for trying this idea out; despite the trolling attempts, this
> > effort is long welcome.
> 
> I created this patchset a long time ago. I've already lost my context. It
> might be better if you keep working on this patch.
> 

Great! I'd like to work on this further.

> > There are some issues with the patchset, which I intend to cover in
> > subsequent emails. I have published[1] some fix-up commits on top of
> > these patches in an attempt to ensure that, barring the issues with a
> > known fix, this works; however, some bugs are definitely still unsolved
> > by now, so I decided to discuss the more apparent points first.
> > 
> > [1] http://git.altlinux.org/people/arseny/packages/hasher-priv.git?a=summary
> 
> It looks like you've already started working on finalizing this patch :)
> 
> > There's an issue when hasher-privd tries to fulfill a chrootuid{1,2}
> > request: the (eventually) unprivileged task executor process
> > successfully invokes waitpid() or the likes on a child process,
> > select()s on I/O descriptors, but gets CHLD later — and it looks like
> > the inherited signal handler causes it to wait again.
> 
> Hm...
> 
> > I've not yet found a decent reproducer — the following command:
> > `hsh-shell $workdir'
> 
> There is no such command. You need to send command to run /bin/sh.

Yes, there's no such IPC command, I was referring to a shell command run
in the host system by the caller user.

> 
> > reproduces the issue reliably for me, but hsh-mkchroot, hsh-rmchroot,
> > hsh-install are all OK. The root cause nevertheless is not yet
> > established. It looks like this has to be patched somewhere in
> > chrootuid(), but I might be wrong on this one.
> > 

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