Configuring NFTY to notify me when a SSH from outside my local ip range

Question

I would like to be notified if there is ever a successful SSH login into the machine that I accept external connections on via NTFY. Since I frequently login this machine locally (192.168.1.0/24), I'd like to avoid notifications when the connection is from that range.

I am following the example listed here: https://docs.ntfy.sh/examples/#ssh-login-alerts

The notifications work correctly but I am trying to modify my script to exclude 192.168.*, my bash is awful and I have been banging my head against this for hours.

I have modified the ntfy-ssh-login.sh to this:

#!/bin/bash
if [ "${PAM_TYPE}" = "open_session" ]; then
        if [ "${PAM_RHOST}" != 192.168.* ]; then
          curl \
            -H prio:high \
            -H tags:warning \
            -d "SSH login: ${PAM_USER} from ${PAM_RHOST}" \
            http://192.168.1.137:8777/alerts
        fi
fi

which I expect will not send the alert to NTFY if PAM_RHOST starts with 192.168. However, it always sends the alert. I know the value of PAM_RHOST starts with that value because its included in the alert:

30/08/2023, 22:12 Priority 4

⚠️ SSH login: --redacted-- from 192.168.1.11

That 192.168.1.11 is set by ${PAM_RHOST}.

I am sure I am doing something silly.

Answer 1

Making my comment into something of an answer.

The [ test does not treat the * character as a wildcard/pattern, so the ${PAM_RHOST} would never match and your then expression is always evaluated.

Since you are using /bin/bash, you have the [[ test available which will handle a comparison with * as a pattern:

if [[ "${PAM_RHOST}" != 192.168.* ]];