Public bug reported:
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.
** Affects: openssh (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1876320
Title:
Port parameter sshd_config is 22 AND whatever you specify
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