More on SSHD [SOLVED]

[iz0eyj]

Hi,
on the last build 14926 (I'm testing Xenial) the sshd starts without errors, but is impossible to connect because it kills the connection.
This is the debug if I try to connect WSL side from Win side using Putty.

federico@Bestia:~/.ssh$ sudo /usr/sbin/sshd -d
debug1: sshd version OpenSSH_7.2, OpenSSL 1.0.2g-fips 1 Mar 2016
debug1: private host key #0: ssh-rsa SHA256:4/+AwrJXQa8j1xlpQKrumig/dS7qYbsfD1lnpQ8BAkY
debug1: private host key #1: ssh-dss SHA256:VxOUVbEOLTzHyH4LzIYMYlEmos/kUj6NPyhZjncnuRA
debug1: private host key #2: ecdsa-sha2-nistp256 SHA256:KmxxQj//PiHC0JQwfa7pSwevEclSxjo9J4387sSv4JM
debug1: private host key #3: ssh-ed25519 SHA256:gwVzNBu5KSpftqaCzLgIXhsOcd7eG6TWCNiLM6sckUc
debug1: rexec_argv[0]='/usr/sbin/sshd'
debug1: rexec_argv[1]='-d'
debug1: Set /proc/self/oom_adj from 0 to -17
debug1: Bind to port 22 on 0.0.0.0.
Server listening on 0.0.0.0 port 22.
debug1: Bind to port 22 on ::.
Bind to port 22 on :: failed: Address already in use. I THINK YOU CAN IGNORE THIS

AT THIS POINT THE SSH SERVER IS UP AND I START CONNECT IT FROM PUTTY

debug1: Server will not fork when running in debugging mode.
debug1: rexec start in 4 out 4 newsock 4 pipe -1 sock 7
debug1: inetd sockets after dupping: 3, 3
Connection from 127.0.0.1 port 5261 on 127.0.0.1 port 22
debug1: Client protocol version 2.0; client software version PuTTY_Release_0.67
debug1: no match: PuTTY_Release_0.67
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.2p2 Ubuntu-4ubuntu2.1
chroot("/var/run/sshd"): Function not implemented [preauth]
debug1: do_cleanup [preauth]
debug1: monitor_read_log: child log fd closed
debug1: do_cleanup
debug1: Killing privsep child 4572
debug1: audit_event: unhandled event 12
federico@Bestia:~/.ssh$

[aseering]

Hi @iz0eyj -- for what it's worth, I think I remember some discussion somewhere about needing to modify /etc/ssh/sshd_config to disable the chroot(). Unfortunately, I can't seem to find that discussion...

[iz0eyj]

@aseering Many thanks for answer, I found it (#300).
The suggested workarond "change UsePrivilegeSeparation to no in /etc/ssh/sshd_config" seems good.
Now I have some problem with keys:

debug1: sshd version OpenSSH_7.2, OpenSSL 1.0.2g-fips 1 Mar 2016
debug1: key_load_private: No such file or directory
debug1: key_load_public: No such file or directory
Could not load host key: /etc/ssh/ssh_host_key
debug1: rexec_argv[0]='/usr/sbin/sshd'
debug1: rexec_argv[1]='-f'
debug1: rexec_argv[2]='/etc/ssh/ssh_config'
debug1: rexec_argv[3]='-d'
debug1: Set /proc/self/oom_adj from 0 to -17
debug1: Bind to port 22 on 127.0.0.1.
Server listening on 127.0.0.1 port 22.
debug1: Server will not fork when running in debugging mode.
debug1: rexec start in 4 out 4 newsock 4 pipe -1 sock 7
debug1: inetd sockets after dupping: 3, 3

Connection from 127.0.0.1 port 12511 on 127.0.0.1 port 22
debug1: Client protocol version 2.0; client software version PuTTY_Release_0.67
debug1: no match: PuTTY_Release_0.67
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.2p2 Ubuntu-4ubuntu2.1
debug1: list_hostkey_types:
No supported key exchange algorithms
debug1: do_cleanup
debug1: audit_event: unhandled event 12
federico@Bestia:/etc/ssh$

[aseering]

@iz0eyj -- hm... It sounds like you don't have an ssh host key for some reason. Normally those are generated when the openssh package is installed. Maybe it didn't finish installing correctly? If you run sudo apt-get -f install, does it try to finish installing any packages?

You could also try regenerating the host key. Various places online have instructions for doing that; for example:
http://www.cyberciti.biz/faq/howto-regenerate-openssh-host-keys/

[iz0eyj]

@aseering ok, all works now, something wrong during the first sshd installation.
Many thanks for your suggestion, for me sshd is important to use VisualGDB.