[Savannah-hackers] possible fix for sftp on Savannah; please try

[Jonathan Walther]

I am back from the farm now, and have turned my thoughts to the problems
of chrooting sftp.

You have the following in /usr/local/bin/cvssh:

'X'*'sftp-server'*)
 # Actually run it.
 valid=yes
 /usr/sbin/chroot /upload /usr/lib/sftp-server
 ;;

I suggest you replace the chroot line with the following:

 exec /usr/local/bin/chroot-sftp

You will find chroot-sftp.c in ~djw; you can "make chroot-sftp" to make
the binary, then copy it to /usr/local/bin.

I notice that when sftp aborts the connection, it says something about
"file descriptor 4".  When the shell invokes chroot, it is not tying
it's file descriptor 4 to that of the chroot process.  By using "exec",
this should work.

In case you are interested, here is the source for chroot-sftp.c:

-------- chroot-sftp.c ---------

#include <unistd.h>

int
main(int argc, char** argv)
{
       chroot("/upload");
       execl("/usr/lib/sftp-server", "/usr/lib/sftp-server", NULL);
}

-------- chroot-sftp.c ---------

If this doesn't fix sftp, then we need to try the following:

In /etc/ssh/sshd_config, change the line that reads:

 Subsystem sftp /usr/local/bin/cvssh

To read:

 Subsystem sftp /usr/local/bin/chroot-sftp

Please let me know how this works; I know you are busy, and if I can do
anything at all to help you try this out faster, please let me know.

Sincerely,

Jonathan Walther
Xouvert Project Coordinator

--

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