inetd mode and disable_syslog should be compatible

[skarnet]

Hi,

When trying to build dropbear-2022.83, with only INETD_MODE and DISABLE_SYSLOG, the binary refuses to run, saying: Dropbear inetd mode is incompatible with debug -v or non-syslog.

A comment in the code says:
/* log output goes to stderr which would get sent over the inetd network socket */.

But this is inaccurate. Super-servers like s6-tcpserver and tcpsvd, which spawn inetd-mode processes, do not conflate stdout and stderr; the daemon's stdout is sent over the network socket, but the daemon's stderr is properly sent to the logger. Using syslog has never been necessary in inetd mode; my server runs with lots of daemons under s6-tcpserver and no syslogd at all. It worked with the 2020 version of dropbear; I was surprised that it stopped working when I upgraded.

Could the functionality please be restored?

Thanks.

[mkj]

I hadn't realised stderr worked OK with those.
I'll change it to allow non-syslog. I wonder if there's any way to catch running under an unsupported inetd - there have been cases reported in the past where it seemed to work but then the connection mysteriously broke when debug output was printed.

I added the test for -v back in 2018.

[skarnet]

Thanks!

I think it's more a question of "bad configuration" than "unsupported inetd". Any inetd-like superserver can send stderr to stdout when misconfigured, and that would obviously cause issues - but it's neither on you, nor on the inetd author. Admins are responsible for handling their tools properly.

[opk12]

Thank you for the fix. This allows to debug configuration issues on the ubiquitous systemd, where you can configure StandardError=file:/error_output.txt.