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List:       busybox
Subject:    RE: ftpd authentication
From:       Morten Kvistgaard <MK () pch-engineering ! dk>
Date:       2014-09-16 7:10:02
Message-ID: 0855BDD4CF82174A8BE362DE9F27C3BF026F86BF2A03 () pche-exchange
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> On Monday 15 September 2014 16:34, Morten Kvistgaard wrote:
> > Hello Denys,
> > 
> > I've studied the last patch you applied to ftpd.
> > 
> > The patch can be fixed if you reorder the "change_identity" to beneath the
> jail.
> 
> Fix in what way? What is the bug?

The bug is that if you use the authentication + chroot feature, the server will crash \
at login. (Connection closes.) The current code goes like this:

...
change_identity(pw);
...
xchroot(argv[0]);
...

According to doc, http://linux.die.net/man/2/chroot, only privileged processes may \
call chroot. So the crash makes sence.


> 
> > Also the "change_identity" ought to conflict with the NOMMU jail break.
> > However a carefully placed call to "getpwuid" seems to somehow solve
> this. (wtf?) I've tested it on Ubuntu + uClinux.
> 
> What is the bug?


The same issue arise when the NOMMU has to break out of jail. (chroot again.) You \
need to regain privileges before you can break out.


 
 
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