sshrc script no longer working

rtaft

4/11/24, 11:58 PM

I have an /etc/ssh/sshrc script that I have used in the past and it has worked fine. chmod is 755

#!/bin/bash

ip=`echo $SSH_CONNECTION | cut -d " " -f 1`

if [[ $ip == 192.168.1.* ]] || [[ $ip == 127.0.0.1 ]] ;
then
  exit
fi

echo "User $USER just logged in from $ip" | sendEmail -t recipient@example.com -f sender@example.com -u 'SSH login detected' > /dev/null

I recently upgraded to Ubuntu 22.04 and I now get this error:

/etc/ssh/sshrc: 5: [[: not found

I then found a similar script https://gist.github.com/mplinuxgeek/f08b91d2236b742f19c63579cd727167 and I get the same error on the if statement with this one. Any ideas what is wrong here? I know it worked in Ubuntu 18.04. I'm not sure if it worked in Ubuntu 20.04 since I have not utilized the ssh server much since covid.

EDIT: It does appear that dash is being run.

$ ls -al /bin/sh
lrwxrwxrwx 1 root root 4 Feb  8 19:08 /bin/sh -> dash

1 + 3

ssh

22.04

doneal24

4/12/24, 12:09 AM

Are you sure `/bin/bash` is really bash? Confirm with `ls -l /bin/bash`. Also, try running `bash /etc/ssh/sshrc` to see if you still get the error. FYI, backticks are deprecated and you should use `IP=$(...)` for the assignment. You might also want to put 192.168.1.* in single-quotes to make sure it is never expanded.

steeldriver

4/12/24, 2:00 AM

`man sshd` suggests that "sh(1) runs it" (implying that the shebang is ignored?) so it would suggest that /bin/sh was symlinked to bash on your previous system whereas it is now symlinked to dash (which doesn't support the `[[ ]]` extended test syntax)

rtaft

4/12/24, 2:35 PM

I actually had this content on my Ubuntu 20 Pi: `/bin/bash /home/rtaft/bin/sshrc` which explains how I was able to get it working. The Pi wasn't working yesterday so I couldn't just look at the difference.

Score:1

Ubuntu

Artur Meinild

4/12/24, 6:13 AM

I think steeldrivers comment is correct, in which case you should replace the double brackets with single ones (and also the double equal signs):

#!/bin/sh

ip=$( echo $SSH_CONNECTION | cut -d " " -f 1 )

if [ $ip = 192.168.1.* ] || [ $ip = 127.0.0.1 ] ;
then
  exit
fi

echo "User $USER just logged in from $ip" | sendEmail -t recipient@example.com -f sender@example.com -u 'SSH login detected' > /dev/

+ 0

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