ftpd authentication

[Morten Kvistgaard]

> 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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