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Re: OpenSSH - sftp not working for non-Administrator users


Doug Lim wrote:
Christopher Faylor wrote:
On Sun, Jul 19, 2009 at 08:50:47PM -0500, Doug Lim wrote:
After a bit more research on the problem, I found a discussion thread on the web discussing a similar problem from 2006. The difference is that the thread discusses scp connections dropping immediately after non-administrator authentication.

http://winscp.net/forum/viewtopic.php?t=3782

A response to a thread from March of this year indicates that copying all of the DLL files from cygwin\usr\bin to cygwin\usr\sbin as a workaround. I've copied the DLL files on my server per the workaround and now non-administrator users are able to use sftp.

I've attached a copy of cygcheck.out from the server where this is happening.

That sounds like a pretty <insert negative adjective here> workaround.


Just setting the PATH to include cygwin's bin directory is likely to
work better.  I know that someone in that thread said that they did that
already but I'm not convinced that they really knew what they were
doing.

cgf

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Except, cygwin\bin was already in the path as indicated in the cygcheck.out I attached. It doesn't explain why users belonging to the Local Administrators group would be able to maintain an SFTP connection while non-Administrators would get dropped immediately following authentication.


I just reconfirmed. I left cygwin\bin in the path and took the DLLs back out of cygwin\usr\sbin. Non-Administrator users are again dropped immediately after authentication.

Here's the sftp debug output with the DLLs removed from cygwin\usr\sbin on the server

dlim@vorlon ~ $ sftp -v <nonpriv-user>@<host>
Connecting to <host>...
OpenSSH_5.2p1, OpenSSL 0.9.8k 25 Mar 2009
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Connecting to <host> [xx.xx.xx.xx] port 22.
debug1: Connection established.
debug1: identity file /home/dlim/.ssh/id_rsa type -1
debug1: identity file /home/dlim/.ssh/id_dsa type -1
debug1: Remote protocol version 2.0, remote software version OpenSSH_5.1
debug1: match: OpenSSH_5.1 pat OpenSSH*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.2
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: server->client aes128-ctr hmac-md5 none
debug1: kex: client->server aes128-ctr hmac-md5 none
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP
debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY
debug1: Host '<host>' is known and matches the RSA host key.
debug1: Found key in /home/dlim/.ssh/known_hosts:21
debug1: ssh_rsa_verify: signature correct
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey,password,keyboard-interactive
debug1: Next authentication method: publickey
debug1: Trying private key: /home/dlim/.ssh/id_rsa
debug1: Trying private key: /home/dlim/.ssh/id_dsa
debug1: Next authentication method: keyboard-interactive
debug1: Authentications that can continue: publickey,password,keyboard-interactive
debug1: Next authentication method: password
<nonpriv-user>@<host>'s password:
debug1: Authentication succeeded (password).
debug1: channel 0: new [client-session]
debug1: Requesting no-more-sessions@openssh.com
debug1: Entering interactive session.
debug1: Sending subsystem: sftp
debug1: client_input_channel_req: channel 0 rtype exit-status reply 0
debug1: client_input_channel_req: channel 0 rtype eow@openssh.com reply 0
debug1: channel 0: free: client-session, nchannels 1
debug1: fd 0 clearing O_NONBLOCK
Transferred: sent 1584, received 2104 bytes, in 1.6 seconds
Bytes per second: sent 991.7, received 1317.2
debug1: Exit status 128
Connection closed



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More information about the problem. Having to copy all of the DLLs from cygwin\bin to cygwin\usr\sbin is overkill. I started removing DLL copies from cygwin\usr\sbin until non-admin users started getting dropped from sftp after authentication. I was able to remove all of the DLLs except cygwin1.dll. As soon as I removed cygwin1.dll from cygwin\usr\sbin non-admin users started getting dropped from sftp sessions immediately after authentication again.



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