A better telnet URL handler

After I wrote yesterday’s post, Philip reminded me of the dangers of not validating your inputs. Here is a better telnet/ssh handler which checks the URL passed to it.

Update 2010-08-27: don’t use this script either! See my next post for a better one.

#!/usr/bin/perl
# parse URL
($protocol,$host) = split /:\/\//, $ARGV[0];
($host,$port) = split /:/, $host;

# validate input
if ( $protocol !~ /^(telnet|ssh)$/ || $host !~ /^[a-zA-Z0-9.-]+$/ || $port !~ /(^[a-zA-Z0-9_-]+$|^$)/ ) {
        warn "Invalid URL";
        exit 1;
}

# if SSH, add -p argument
if ( $protocol eq "ssh" && $port != '' ) { $port = "-p $port" ; }

# call terminal emulator
exec("konsole --hold -e $protocol $host $port");
exit;

This script only accepts telnet:// and ssh:// URLs, where the host is a valid domain name and the port is a valid port (including text aliases like “smtp” from /etc/services). It passes SSH port arguments correctly and tells Konsole to stay open after the session terminates.

You can download a more advanced form of this script here.