Re: Chrooted OpenSSH for Windows (rssh sftp cygwin)
John M. L. john at recaffeinated.com writes: I've been trying to implement an sftp server using OpenSSH for Windows (http://sshwindows.sourceforge.net). I haven't found much recent discussion on th topic of running OpenSSH in a chrooted jail on cygwin, but the following messages from a year ago have shed some light on the topic: I solved exactly the same problem using scponly (http://www.sublimation.org/scponly/) . The current version compiles easily under recent Cygwin releases. You only have to modify the Makefile to include some libraries explicitly. Id always try to have a binary as a chroot stub and not a shell script. If you use a shell script, you need bash and several supplemental programs in the chroot jail which all may contain security leaks. The tool that I used has a make option to prepare the chroot jail. It copies all required files to the jail. So you may learn from it even if you decide to stay with rssh. Youve to make another decision: Do you only need to support sftp protocol version 2 or also older versions. In the first case it should be sufficient to have sftp-server.exe in the chroot jail (plus a passwd group). In the second case, youll need to have things like bash, ls, rm and others again. Hope this helps a bit! Christian -- Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple Problem reports: http://cygwin.com/problems.html Documentation: http://cygwin.com/docs.html FAQ: http://cygwin.com/faq/
Re: Chrooted OpenSSH for Windows (rssh sftp cygwin)
Thanks, Christian! I actually got the chrooted sftp session to *work* (! shell commands still work). I made these changes: -- chroot /cygdrive/c/StudentsShare /usr/sbin/sftp-server -- Basically, I removed the 'exec' from the chroot call. I thought maybe there were insufficient dll's in the chroot C:\StudentsShare. I copied all the local files from the /usr, /bin and /etc folders to my chroot and still had the same problem with including the 'exec'. Does anyone know how the exec effects chroot call? I dont understand how the exec makes it more secure by replacing the current script process. However, this doesn't stop a user from entering a ! command at the sftp prompt. I had some luck setting file privileges/ownership but that seems like a dangerous move to chmod/chown all the files outside of C:\StudentsShare. Any ideas are welcome. Also (in response to Christian Weinberger), I only need SFTP protocol 2. I prefer to stick to SFTP just because it's easier to transfer a group of files and manipulate folders etc. With time permitting for my project I may give scponly a try. Christian Weinberger wrote: John M. L. john at recaffeinated.com writes: I've been trying to implement an sftp server using OpenSSH for Windows (http://sshwindows.sourceforge.net). I haven't found much recent discussion on th topic of running OpenSSH in a chrooted jail on cygwin, but the following messages from a year ago have shed some light on the topic: I solved exactly the same problem using scponly (http://www.sublimation.org/scponly/) . The current version compiles easily under recent Cygwin releases. You only have to modify the Makefile to include some libraries explicitly. Id always try to have a binary as a chroot stub and not a shell script. If you use a shell script, you need bash and several supplemental programs in the chroot jail which all may contain security leaks. The tool that I used has a make option to prepare the chroot jail. It copies all required files to the jail. So you may learn from it even if you decide to stay with rssh. Youve to make another decision: Do you only need to support sftp protocol version 2 or also older versions. In the first case it should be sufficient to have sftp-server.exe in the chroot jail (plus a passwd group). In the second case, youll need to have things like bash, ls, rm and others again. Hope this helps a bit! Christian -- Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple Problem reports: http://cygwin.com/problems.html Documentation: http://cygwin.com/docs.html FAQ: http://cygwin.com/faq/
Chrooted OpenSSH for Windows (rssh sftp cygwin)
I've been trying to implement an sftp server using OpenSSH for Windows (http://sshwindows.sourceforge.net). I haven't found much recent discussion on th topic of running OpenSSH in a chrooted jail on cygwin, but the following messages from a year ago have shed some light on the topic: http://archive.erdelynet.com/ssh-l/2003-10/msg00057.php http://www.cygwin.com/ml/cygwin/2003-08/msg00738.html http://cygwin.com/ml/cygwin/2003-07/msg01500.html I almost have the system running on Windows 2000 Server. Using the ssh server without chroot is fine. However, when I try to connect using the chrooted sftp shell it automatically disconnects the user. Using WinSCP3 to connect returns at cryptic error code 127 and a command line sftp just dies silently with no explanation. Here's my current login shell script for users: #!/bin/sh #echo Parameters: $@ /home/sshlogin.log if [ $* != -c /usr/sbin/sftp-server ]; then echo Sorry, sftp only! exit 1 fi #without chroot works! exec /bin/sh -i $@ #with chroot no such luck #chroot /cygdrive/c/StudentsShare exec /bin/sh -i $@ I'm assuming part of the problem may be the required files for the /bin/sh call are not inside the chroot jail /cygdrive/c/StudentsShare. If this is the case, I would like to know if anyone could let me know what files should be included. At first I got Cygwin dll errors stating that cyg*.* could not be found. They stopped once I moved the files into the jail and/or fixed environment path variables. I have two log files using sshd -d -d -d for high debug output. They can be found here: Chrooted log: http://john.isosceles7.com/files/login_chroot.txt Un Chrooted log http://john.isosceles7.com/files/login_nochroot.txt The debug is cryptic, but if I think the error in the chroot is around line 116. Here's an excerpt of this piece Chrooted log (lines 112-126): subsystem request for sftp debug1: subsystem: exec() /usr/sbin/sftp-server debug2: fd 10 setting O_NONBLOCK debug2: fd 9 setting O_NONBLOCK debug2: channel 0: read=0 rfd 10 len 0 debug1: Received SIGCHLD. debug2: channel 0: read failed debug2: channel 0: close_read debug2: channel 0: input open - drain debug2: channel 0: ibuf empty debug2: channel 0: send eof debug2: channel 0: input drain - closed debug2: notify_done: reading debug1: session_by_pid: pid 1364 debug1: session_exit_message: session 0 channel 0 pid 1364 Un Chrooted log (lines 112-126): subsystem request for sftp debug1: subsystem: exec() /usr/sbin/sftp-server debug2: fd 10 setting O_NONBLOCK debug2: fd 9 setting O_NONBLOCK debug2: channel 0: rcvd eof debug2: channel 0: output open - drain debug2: channel 0: obuf empty debug2: channel 0: close_write debug2: channel 0: output drain - closed debug1: Received SIGCHLD. debug1: session_by_pid: pid 1368 debug1: session_exit_message: session 0 channel 0 pid 1368 debug2: channel 0: request exit-status debug1: session_exit_message: release channel 0 debug1: session_close: session 0 pid 1368 Any help on my problem would be appreciated! Of course if any other background information is helpful I will gladly contribute! ... An additional note: The new cygwin dll 1.5.12-1 source includes wordexp.h which was a problem that prohibited using rssh (http://www.pizzashack.org) instead of chrooting openssh. Does anyone know how this will affect rssh? Thanks, John M Lauck -- Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple Problem reports: http://cygwin.com/problems.html Documentation: http://cygwin.com/docs.html FAQ: http://cygwin.com/faq/
