HTTP Banner Grabber in AWK and Bash

Here is a simple banner grabber written in awk. all it does is query the http server and extracts the 'Server' paramater from the HTTP header and returns the result.

#!/usr/bin/env gawk

BEGIN { }


{ ## START _MAIN

port=80;

getline host<ARGV[1]

HTTP = "/inet/tcp/0/" host "/" port
   
PROCINFO[HTTP, "READ_TIMEOUT"] = 1000
   
print "HEAD / HTTP/1.0\r\n\r\n" |& HTTP   

while ( (HTTP |& getline) > 0) {
    if ($1 ~ /Server:/)
        print $0
}

close("/inet/tcp/0/" host "/80")

} ## END _MAIN


END { }

If we run the script...

root@asus:~/pentest_notes/SCANNING% awk -f simple_banner_grabber.awk awk.txt
Server: Apache/2.4.18 (Ubuntu)
root@asus:~/pentest_notes/SCANNING% 

BASH example

Here an example in Bash.

#!/usr/bin/env bash
## 
## Simple HTTP banner grabber
## 
host="127.0.0.1"
port=80

exec 3<>/dev/tcp/${host}/${port}

echo -e "HEAD / HTTP/1.0\r\n\r\n" >&3

cat <&3 | awk '/Server: (.+)/ {print $0}'

We run the script...

root@asus:~/pentest_notes/SCANNING% ./simple_banner_grabber.sh
Server: Apache/2.4.18 (Ubuntu)
root@asus:~/pentest_notes/SCANNING%