putty serial autologin

Question

I want to login to putty automatically via serial port through shell or bash script. This is the code:

#!/bin/bash
tty=/dev/$(dmesg | grep tty | tail -n 1 | sed -e 's/ /\n/g' -e 's/\t/\n/g' | grep tty)
tty=${tty%:}
sudo chown "$USER":"$USER" "$tty"
putty -serial "$tty" -sercfg 115200

But if I change the last line of code to:

putty -serial "$tty" -sercfg 115200 -l $username -pw $password

I get the following output:

PuTTY: the -pw option can only be used with the SSH protocol

Is there an alternative command, always via Putty, always via serial port?

Answer 1

No, you cannot pass a password when logging in over a serial line. Over a serial line, you are logged by a process that is called [a]getty and it will display a prompt for a username and a password.

Now, (because this PuTTY question appears off-topic to me) if you'd like to ask whether you could have a user 'logged in' at a serial port at all times without password, that answer is yes. Take a look at man agetty and search for -autologin.

Securty caveat: Needless to say that 'anyone' who is able to connect to your RS232 port with a dumb serial terminal (emulator), now gets in right away?