[systemd-devel] Starting the sshd service on a 'non-bash' system

[Mark Corbin]

Hello

I was wondering whether anybody has any experience of running the sshd
service successfully on a system with a 'non-bash' shell?

We're using systemd 250.5 and openssh 8.9p1. Both ssh and scp work as
expected with '/bin/sh -> bash.bash' on the target, but with '/bin/sh ->
busybox.nosuid' (ash shell) the connections fail.

The sshd logs on the target show:
Jul 31 15:24:56 hc sshd[17826]: Connection from UNKNOWN port 65535 on
192.168.12.246 port 65535
Jul 31 15:24:56 hc sshd[17826]: debug1: kex_exchange_identification: write:
Broken pipe
Jul 31 15:24:56 hc sshd[17826]: banner exchange: Connection from UNKNOWN
port 65535: Broken pipe

Some extra debug messages that I've added to both systemd and sshd show
that the incoming socket gets closed somewhere between the handover from
the systemd socket service to the systemd sshd service. This results in
sshd being unable to get any peer details. The call to getpeername in
service_spawn fails with ENOTCONN.

I can't see anything obvious in either the systemd source that suggests a
dependency on bash.

Any ideas gratefully appreciated.

Regards

Mark

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*Mark Corbin *
Senior Software Engineer  |   lunarenergy.com <https://www.lunarenergy.com>
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