Comment 21 for bug 2011458

I verified the fix using openssh-server 1:9.0p1-1ubuntu7.2 from kinetic-proposed:

Test 1:

root@kinetic:~# apt-cache policy openssh-server
openssh-server:
  Installed: 1:9.0p1-1ubuntu7.2
  Candidate: 1:9.0p1-1ubuntu7.2
  Version table:
 *** 1:9.0p1-1ubuntu7.2 500
        500 http://archive.ubuntu.com/ubuntu kinetic-proposed/main amd64 Packages
        100 /var/lib/dpkg/status
     1:9.0p1-1ubuntu7.1 500
        500 http://archive.ubuntu.com/ubuntu kinetic-updates/main amd64 Packages
     1:9.0p1-1ubuntu7 500
        500 http://archive.ubuntu.com/ubuntu kinetic/main amd64 Packages
root@kinetic:~# ssh localhost
The authenticity of host 'localhost (::1)' can't be established.
ED25519 key fingerprint is SHA256:DduZSXZNbtS3h9D91h0NQfRK7wnuxpWrj3f8/0J4ajc.
This key is not known by any other names
Are you sure you want to continue connecting (yes/no/[fingerprint])? no
Host key verification failed.
root@kinetic:~# systemctl status ssh.service
● ssh.service - OpenBSD Secure Shell server
     Loaded: loaded (/lib/systemd/system/ssh.service; disabled; preset: enabled)
    Drop-In: /etc/systemd/system/ssh.service.d
             └─00-socket.conf
             /run/systemd/system/service.d
             └─zzz-lxc-service.conf
     Active: active (running) since Mon 2023-05-15 14:00:03 UTC; 11s ago
TriggeredBy: ● ssh.socket
       Docs: man:sshd(8)
             man:sshd_config(5)
    Process: 1013 ExecStartPre=/usr/sbin/sshd -t (code=exited, status=0/SUCCESS)
   Main PID: 1014 (sshd)
      Tasks: 1 (limit: 18854)
     Memory: 1.3M
        CPU: 40ms
     CGroup: /system.slice/ssh.service
             └─1014 "sshd: /usr/sbin/sshd -D [listener] 0 of 10-100 startups"

May 15 14:00:03 kinetic systemd[1]: Starting OpenBSD Secure Shell server...
May 15 14:00:03 kinetic sshd[1014]: Server listening on :: port 22.
May 15 14:00:03 kinetic systemd[1]: Started OpenBSD Secure Shell server.
May 15 14:00:04 kinetic sshd[1015]: Connection closed by ::1 port 43046 [preauth]
root@kinetic:~# systemctl reload ssh.service
root@kinetic:~# systemctl status ssh.service
● ssh.service - OpenBSD Secure Shell server
     Loaded: loaded (/lib/systemd/system/ssh.service; disabled; preset: enabled)
    Drop-In: /etc/systemd/system/ssh.service.d
             └─00-socket.conf
             /run/systemd/system/service.d
             └─zzz-lxc-service.conf
     Active: active (running) since Mon 2023-05-15 14:00:03 UTC; 22s ago
TriggeredBy: ● ssh.socket
       Docs: man:sshd(8)
             man:sshd_config(5)
    Process: 1013 ExecStartPre=/usr/sbin/sshd -t (code=exited, status=0/SUCCESS)
    Process: 1021 ExecReload=/usr/sbin/sshd -t (code=exited, status=0/SUCCESS)
    Process: 1022 ExecReload=/bin/kill -HUP $MAINPID (code=exited, status=0/SUCCESS)
   Main PID: 1014 (sshd)
      Tasks: 1 (limit: 18854)
     Memory: 1.4M
        CPU: 97ms
     CGroup: /system.slice/ssh.service
             └─1014 "sshd: /usr/sbin/sshd -D [listener] 0 of 10-100 startups"

May 15 14:00:03 kinetic systemd[1]: Starting OpenBSD Secure Shell server...
May 15 14:00:03 kinetic sshd[1014]: Server listening on :: port 22.
May 15 14:00:03 kinetic systemd[1]: Started OpenBSD Secure Shell server.
May 15 14:00:04 kinetic sshd[1015]: Connection closed by ::1 port 43046 [preauth]
May 15 14:00:23 kinetic systemd[1]: Reloading OpenBSD Secure Shell server...
May 15 14:00:23 kinetic sshd[1014]: Received SIGHUP; restarting.
May 15 14:00:23 kinetic systemd[1]: Reloaded OpenBSD Secure Shell server.
May 15 14:00:23 kinetic sshd[1014]: Server listening on :: port 22.

Test 2:

root@kinetic:~# apt-cache policy openssh-server
openssh-server:
  Installed: 1:9.0p1-1ubuntu7.2
  Candidate: 1:9.0p1-1ubuntu7.2
  Version table:
 *** 1:9.0p1-1ubuntu7.2 500
        500 http://archive.ubuntu.com/ubuntu kinetic-proposed/main amd64 Packages
        100 /var/lib/dpkg/status
     1:9.0p1-1ubuntu7.1 500
        500 http://archive.ubuntu.com/ubuntu kinetic-updates/main amd64 Packages
     1:9.0p1-1ubuntu7 500
        500 http://archive.ubuntu.com/ubuntu kinetic/main amd64 Packages
root@kinetic:~# vi /etc/default/ssh
root@kinetic:~# cat /etc/default/ssh
# Default settings for openssh-server. This file is sourced by /bin/sh from
# /etc/init.d/ssh.

# Options to pass to sshd
SSHD_OPTS=-ddd
root@kinetic:~# ssh localhost
The authenticity of host 'localhost (::1)' can't be established.
ED25519 key fingerprint is SHA256:DduZSXZNbtS3h9D91h0NQfRK7wnuxpWrj3f8/0J4ajc.
This key is not known by any other names
Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
Warning: Permanently added 'localhost' (ED25519) to the list of known hosts.
Welcome to Ubuntu 22.10 (GNU/Linux 6.2.0-20-generic x86_64)

 * Documentation: https://help.ubuntu.com
 * Management: https://landscape.canonical.com
 * Support: https://ubuntu.com/advantage

The programs included with the Ubuntu system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Ubuntu comes with ABSOLUTELY NO WARRANTY, to the extent permitted by
applicable law.

debug1: PAM: reinitializing credentials
debug1: permanently_set_uid: 0/0
debug3: Copy environment: XDG_SESSION_ID=15
debug3: Copy environment: XDG_RUNTIME_DIR=/run/user/0
debug3: Copy environment: DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/0/bus
debug3: Copy environment: XDG_SESSION_TYPE=tty
debug3: Copy environment: XDG_SESSION_CLASS=user
debug3: Copy environment: PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin
debug3: Copy environment: LANG=en_US.UTF-8
Environment:
  LANG=en_US.UTF-8
  USER=root
  LOGNAME=root
  HOME=/root
  PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin
  SHELL=/bin/bash
  TERM=xterm-256color
  XDG_SESSION_ID=15
  XDG_RUNTIME_DIR=/run/user/0
  DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/0/bus
  XDG_SESSION_TYPE=tty
  XDG_SESSION_CLASS=user
  SSH_CLIENT=::1 36376 22
  SSH_CONNECTION=::1 36376 ::1 22
  SSH_TTY=/dev/pts/2
root@kinetic:~# systemctl status ssh.service
● ssh.service - OpenBSD Secure Shell server
     Loaded: loaded (/lib/systemd/system/ssh.service; disabled; preset: enabled)
    Drop-In: /etc/systemd/system/ssh.service.d
             └─00-socket.conf
             /run/systemd/system/service.d
             └─zzz-lxc-service.conf
     Active: active (running) since Mon 2023-05-15 14:19:05 UTC; 11s ago
TriggeredBy: ● ssh.socket
       Docs: man:sshd(8)
             man:sshd_config(5)
    Process: 150 ExecStartPre=/usr/sbin/sshd -t (code=exited, status=0/SUCCESS)
   Main PID: 151 (sshd)
      Tasks: 0 (limit: 18854)
     Memory: 2.2M
        CPU: 91ms
     CGroup: /system.slice/ssh.service
             ‣ 151 "sshd: root@pts/2"

May 15 14:19:06 kinetic sshd[151]: debug1: server_input_channel_req: channel 0 request shell reply 1
May 15 14:19:06 kinetic sshd[151]: debug1: session_by_channel: session 0 channel 0
May 15 14:19:06 kinetic sshd[151]: debug1: session_input_channel_req: session 0 req shell
May 15 14:19:06 kinetic sshd[151]: Starting session: shell on pts/2 for root from ::1 port 36376 id 0
May 15 14:19:06 kinetic sshd[151]: debug2: fd 5 setting TCP_NODELAY
May 15 14:19:06 kinetic sshd[151]: debug3: set_sock_tos: set socket 5 IPV6_TCLASS 0x10
May 15 14:19:06 kinetic sshd[151]: debug2: channel 0: rfd 11 isatty
May 15 14:19:06 kinetic sshd[151]: debug2: fd 11 setting O_NONBLOCK
May 15 14:19:06 kinetic sshd[151]: debug3: fd 8 is O_NONBLOCK
May 15 14:19:06 kinetic sshd[151]: debug3: send packet: type 99