[Bug 1876320] Re: Port parameter sshd_config is 22 AND whatever you specify

[Simon Déziel]

@Adriaan, are there really 2 sshd running? Or is it only one binding to
the 2 ports and applying different parameter using Match conditions?
Beware what on 20.04, there is support for additional config snippets
dropped in /etc/ssh/sshd_config.d/*.conf.

To check for 2 daemons:

sudo ss -nltp | grep sshd

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Title:
  Port parameter sshd_config is 22 AND whatever you specify

Status in openssh package in Ubuntu:
  New

Bug description:
  On my Ubuntu Server 20.04 LTS with OpenSSH 1:8.2p1-4, I have TWO sshd
  deamons. One (on port 22) is for internal use, accepts passwords etc.
  The second (on port 7722) does not allow PAM use and no passwords,
  allows only one user(name) and uses an alternative autorized_keys file
  (that only root can edit).

  Any parameter FIRST encountered in sshd_config is the one that is
  accepted; others do not override (like in many other config files).
  There is one exception: 'Port', which is accumulative. To make life
  easier, I set the more restrictive parameters for port 7722 first and
  next include the system-default /etc/ssh/sshd_config.

  The /etc/ssh/sshd_config file(s) in Ubuntu Server 20.04 DO NOT specify
  'Port' anywhere - the default is 22. But: it is obviously still
  accumulative: Setting 'Port' to 7722 makes sshd listen on port 7722
  AND 22. This is unwanted.

  Proposed solution: Remove the accumulative behavior for 'Port' and
  REQUIRE the 'Port' parameter like before (and maybe have second and
  later parameters override the earlier ones, like 'everyone else').

  Regards,

  Adriaan

  PS Searching for solutions, I found that specifying 'ListenAddress
  0.0.0.0:7722' stops sshd from listening to port 22. This, however, is
  not documented in 'man 5 sshd_config' and may be an unreliable side-
  effect.

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