I've been trying to understand why when I telnet to my openbsd to a modem hooked to the serial port, the password is echoed at the login prompt.

This happens from any linux client I've used to telnet to the openbsd system over the serial port.

Same behavior happens with a linux system.

My setup is really simple.
modem is set to auto answer ats0=1

/etc/boot.conf has the following:
set tty com0

/etc/ttys has the following:
console "/usr/libexec/getty std.9600" vt220 on secure

----------------------------------------------------------

Does anyone know why the password is shown, and how to get it to not echo when the user types it in?

---
■ Synchronet ■ Lunar Outpost BBS

Re: openbsd telnet to serial
By: bbsing to All on Mon Nov 24 2025 09:36 pm

Does anyone know why the password is shown, and how to get it to not echo wh the user types it in?

Have you tried using a raw connection into it instead of telnet? Try this for science.. make sure you have netcat (nc) installed. Create a file called raw.sh with this in it:

settings=$(stty -g)
stty raw -echo
nc $1 $2
stty $settings

then 'chmod +x raw.sh' and then './raw.sh ipaddress port'. Just one thing to note, when you finally disconnect, you need to hit a key to return to your prompt.

The reason for this is telnet does some negotiation on connect, and you're not running telnetd. Your client says "Hey, let's agree on some stuff!" but your server isn't listening for that.

---
■ Synchronet ■ TIRED of waiting 2 hours for a taco? GO TO TACOPRONTO.bbs.io