cygwin SSHD auto closes the connection upon connection

I run cygwin/sshd on Windows Vista. I used to be able to use ssh to connect to my computer alright, until recently it started not working (I think I installed and removed some other cygwin packages)

For example, I would run

ssh localhost -l kizzx2

after keying in the password, I would be seeing this

Last login: Sat Dec  5 02:44:11 2009 from 127.0.0.1
Connection to localhost closed.

The strange problem is, if I connect using another account, I would be able to log-in alright! Which means:

ssh localhost -l Administrator

This would get me in an interactive shell!.

It looks like that some profile or environment settings of my user's profile is broken or something, but I don't want to re-build my user profile from scratch by creating a new account.

Any ideas?

Update: Just for information, I have tried replacing ~/.ssh with clean one (let ssh build one from scratch). It didn't seem to do the trick.

Here's the full dump of running ssh with -vvv:

$ ssh localhost -p 22 -vvv
OpenSSH_5.1p1, OpenSSL 0.9.8l 5 Nov 2009
debug1: Reading configuration data /cygdrive/k/.ssh/config
debug1: Reading configuration data /etc/ssh_config
debug2: ssh_connect: needpriv 0
debug1: Connecting to localhost [127.0.0.1] port 22.
debug1: Connection established.
debug1: identity file /cygdrive/k/.ssh/identity type -1
debug3: Not a RSA1 key file /cygdrive/k/.ssh/id_rsa.
debug2: key_type_from_name: unknown key type '-----BEGIN'
debug3: key_read: missing keytype
debug2: key_type_from_name: unknown key type 'Proc-Type:'
debug3: key_read: missing keytype
debug2: key_type_from_name: unknown key type 'DEK-Info:'
debug3: key_read: missing keytype
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug2: key_type_from_name: unknown key type '-----END'
debug3: key_read: missing keytype
debug1: identity file /cygdrive/k/.ssh/id_rsa type 1
debug1: identity file /cygdrive/k/.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_5.1
debug2: fd 3 setting O_NONBLOCK
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug2: kex_parse_kexinit: diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
debug2: kex_parse_kexinit: ssh-rsa,ssh-dss
debug2: kex_parse_kexinit: aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour128,arcfour256,arcfour,aes192-cbc,aes256-cbc,[email protected],aes128-ctr,aes192-ctr,aes256-ctr
debug2: kex_parse_kexinit: aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour128,arcfour256,arcfour,aes192-cbc,aes256-cbc,[email protected],aes128-ctr,aes192-ctr,aes256-ctr
debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: none,[email protected],zlib
debug2: kex_parse_kexinit: none,[email protected],zlib
debug2: kex_parse_kexinit: 
debug2: kex_parse_kexinit: 
debug2: kex_parse_kexinit: first_kex_follows 0 
debug2: kex_parse_kexinit: reserved 0 
debug2: kex_parse_kexinit: diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
debug2: kex_parse_kexinit: ssh-rsa,ssh-dss
debug2: kex_parse_kexinit: aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour128,arcfour256,arcfour,aes192-cbc,aes256-cbc,[email protected],aes128-ctr,aes192-ctr,aes256-ctr
debug2: kex_parse_kexinit: aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour128,arcfour256,arcfour,aes192-cbc,aes256-cbc,[email protected],aes128-ctr,aes192-ctr,aes256-ctr
debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: none,[email protected]
debug2: kex_parse_kexinit: none,[email protected]
debug2: kex_parse_kexinit: 
debug2: kex_parse_kexinit: 
debug2: kex_parse_kexinit: first_kex_follows 0 
debug2: kex_parse_kexinit: reserved 0 
debug2: mac_setup: found hmac-md5
debug1: kex: server->client aes128-cbc hmac-md5 none
debug2: mac_setup: found hmac-md5
debug1: kex: client->server aes128-cbc hmac-md5 none
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP
debug2: dh_gen_key: priv key bits set: 123/256
debug2: bits set: 516/1024
debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY
debug3: put_host_port: [127.0.0.1]:22
debug3: put_host_port: [localhost]:22
debug3: check_host_in_hostfile: filename /cygdrive/k/.ssh/known_hosts
debug3: check_host_in_hostfile: match line 12
debug1: Host '[localhost]:22' is known and matches the RSA host key.
debug1: Found key in /cygdrive/k/.ssh/known_hosts:12
debug2: bits set: 521/1024
debug1: ssh_rsa_verify: signature correct
debug2: kex_derive_keys
debug2: set_newkeys: mode 1
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug2: set_newkeys: mode 0
debug1: SSH2_MSG_NEWKEYS received
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug2: key: /cygdrive/k/.ssh/identity (0x0)
debug2: key: /cygdrive/k/.ssh/id_rsa (0x1052b88)
debug2: key: /cygdrive/k/.ssh/id_dsa (0x0)
debug1: Authentications that can continue: password,keyboard-interactive
debug3: start over, passed a different list password,keyboard-interactive
debug3: preferred publickey,keyboard-interactive,password
debug3: authmethod_lookup keyboard-interactive
debug3: remaining preferred: password
debug3: authmethod_is_enabled keyboard-interactive
debug1: Next authentication method: keyboard-interactive
debug2: userauth_kbdint
debug2: we sent a keyboard-interactive packet, wait for reply
debug1: Authentications that can continue: password,keyboard-interactive
debug3: userauth_kbdint: disable: no info_req_seen
debug2: we did not send a packet, disable method
debug3: authmethod_lookup password
debug3: remaining preferred: 
debug3: authmethod_is_enabled password
debug1: Next authentication method: password
kizzx2@localhost's password: 
debug3: packet_send2: adding 64 (len 58 padlen 6 extra_pad 64)
debug2: we sent a password packet, wait for reply
debug1: Authentication succeeded (password).
debug1: channel 0: new [client-session]
debug3: ssh_session2_open: channel_new: 0
debug2: channel 0: send open
debug1: Requesting [email protected]
debug1: Entering interactive session.
debug2: callback start
debug2: client_session2_setup: id 0
debug2: channel 0: request pty-req confirm 1
debug3: tty_make_modes: ospeed 38400
debug3: tty_make_modes: ispeed 38400
debug2: channel 0: request shell confirm 1
debug2: fd 3 setting TCP_NODELAY
debug2: callback done
debug2: channel 0: open confirm rwindow 0 rmax 32768
debug2: channel_input_confirm: type 99 id 0
debug2: PTY allocation request accepted on channel 0
debug2: channel 0: rcvd adjust 2097152
debug2: channel_input_confirm: type 99 id 0
debug2: shell request accepted on channel 0
Last login: Sat Dec  5 02:44:11 2009 from 127.0.0.1
debug1: client_input_channel_req: channel 0 rtype exit-status reply 0
debug1: client_input_channel_req: channel 0 rtype [email protected] reply 0
debug2: channel 0: rcvd eow
debug2: channel 0: close_read
debug2: channel 0: input open -> closed
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
debug2: channel 0: rcvd close
debug3: channel 0: will not send data after close
debug2: channel 0: almost dead
debug2: channel 0: gc: notify user
debug2: channel 0: gc: user detached
debug2: channel 0: send close
debug2: channel 0: is dead
debug2: channel 0: garbage collecting
debug1: channel 0: free: client-session, nchannels 1
debug3: channel 0: status: The following connections are open:
  #0 client-session (t4 r0 i3/0 o3/0 fd -1/-1 cfd -1)

debug3: channel 0: close_fds r -1 w -1 e 6 c -1
Connection to localhost closed.
Transferred: sent 1712, received 2104 bytes, in 0.2 seconds
Bytes per second: sent 6875.5, received 8449.8
debug1: Exit status 0

I finally got it working:

I was trying to get better debug output then ssh -vvv, so I tried running

/usr/sbin/sshd -d

to catch the output on screen. To my surprise, when I ran sshd like that (not as a service as I usually would with net start sshd), I could log in as any user alright.

That led me to believe that the problem lied in the way the service was set up. So I deleted the service and ran the config script again. Bam! It's done!

cygrunsrv -R sshd
ssh-host-config
# it's fixed!

Edit: It looks like that the reason is that the privilege separation user cannot be disabled in Windows. It used to be OK for me to disable that privilege separation user and still get it to work, but oh well.

This is a typical effect of running the ssh-host-config script once, using typical default selections. What happens is that two new Cygwin user accounts are created, but their settings in /etc/passwd (and possibly /etc/groups) seem temporary. After first run you have the SHELL set to /bin/false and if you compare this to mkpasswd -l -u cyg_server you will see /bin/bash. So either logoff and logon as and run Cygwin as admin, or just make the change in /etc/passwd and restart sshd service.