[scponly] chroot fails without warning - everything still works

[Kaleb Pederson]

Hmm.... not sure what to think.  Using version 4.6 of scponly, this is what I 
see when I connect using a chroot with /home/scponly as the chroot and home 
directory:

scponly[2535]: chrooted binary in place, will chroot()
scponly[2535]: 3 arguments in total.
scponly[2535]:    arg 0 is scponlyc
scponly[2535]:    arg 1 is -c
scponly[2535]:    arg 2 is /usr/lib/misc/sftp-server
scponly[2535]: opened log at LOG_AUTHPRIV, opts 0x00000009
scponly[2535]: retrieved home directory of "/home/scponly" for user "scponly"
scponly[2535]: chrooting to dir: "/home/scponly"
scponly[2535]: chdiring to dir: "/"
scponly[2535]: setting uid to 1015
scponly[2535]: processing request: "/usr/lib/misc/sftp-server"
scponly[2535]: running: /usr/lib/misc/sftp-server (username: scponly(1015), 
IP/port: 10.10.10.1 54861 22)

Actually, I notice one difference.  I have 'scponlyc' as the firs argument, 
you have '/usr/local/sbin/scponlyc'.  The comparison happens as follows:

strncmp(argv[0],CHROOTED_NAME,FILENAME_MAX))

So, that would be the problem.  You would have to 
have /usr/local/sbin/scponlyc as your CHROOTED_NAME for it to match.  I'm not 
sure why it would show up that way.  This is what I have for the user 
account:

scponly:x:1015:1021::/home/scponly:/usr/local/sbin/scponlyc

I guess it's reasonable that the compare strips the directory prefix, but this 
is the first case where I have seen this problem. 

Could you try with a couple of other sftp clients and see what happens?

Thanks.

--Kaleb


On Saturday 17 June 2006 4:40 am, Fred Fiat wrote:
> >> Jun 16 17:00:53 HOST scponly[8806]: 3 arguments in total.
> >> Jun 16 17:00:53 HOST scponly[8806]:  arg 0 is /usr/local/sbin/scponlyc
> >> Jun 16 17:00:53 HOST scponly[8806]:  arg 1 is -c
> >> Jun 16 17:00:53 HOST scponly[8806]:  arg 2 is sftp-server
> >> Jun 16 17:00:53 HOST scponly[8806]: opened log at LOG_AUTHPRIV, opts
> >> 0x00000009
> >> Jun 16 17:00:53 HOST scponly[8806]: retrieved home directory of
> >> "/home/test1" for user "test1"
> >> Jun 16 17:00:53 HOST scponly[8806]: setting uid to 1035
> >> Jun 16 17:00:53 HOST scponly[8806]: processing request: "sftp-server"
> >> Jun 16 17:00:53 HOST scponly[8806]: running: /usr/bin/sftp-server
> >> (username: test1(1035), IP/port: ::1 51149 ::1 22)
> >
> > Fred,
> > Quick sanity check:  Where there other scponly syslog lines?  In a
> > chrooted environment
> > there would have been a set starting with:
> >   "chrooted binary in place, will chroot()"
> > 	and ending with
> >   "chrooting to dir: ..."
> >   {and a couple of chdir messages}
>
> Yes, they were the only lines.
>
> > If they weren't there (I doubt they were) please check the value of
> > CHROOTED_NAME in
> > config.h.  {i.e. It sounds like there may be one more thing going on in
> > your case.}
>
> I have "scponlyc" as the CHROOTED_NAME in config.h
>
> > The trace above indicates that a full path is seen for scponlyc.  That
> > would in fact
> > disable the chroot since the code checks argv[0] for the exact string in
> > CHROOTED_NAME
> > and that is normally "scponlyc".
> >
> > What is the OS?  (The quick fix >might< be to change CHROOTED_NAME but it
> > would be
> > better to find out exactly what is happening.)
>
> Suse 7.3
>
> >     Paul Hyder
> >     NOAA Earth System Research Laboratory, Global Systems Division, HPC
> >     Boulder, CO
>
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