ctf.sh

#!/bin/bash

function atoi {
  IP=$1; IPNUM=0
  for (( i=0 ; i<4 ; ++i )); do
    ((IPNUM+=${IP%%.*}*$((256**$((3-${i}))))))
    IP=${IP#*.}
  done
  echo $IPNUM 
}

function itoa {
  echo -n $(($(($(($((${1}/256))/256))/256))%256)).
  echo -n $(($(($((${1}/256))/256))%256)).
  echo -n $(($((${1}/256))%256)).
  echo $((${1}%256)) 
}

goal="f04031af5ee9939a931a062b836c385eb2ee681fd704ed919534b78329ae34e173e13c31ebfd03db1eb9e9759cd3365195d0d7d53028256038b24975ace8c83d"
      
for ip in 172.16.{0..255}.{0..255} ; do
  echo "Checking " $ip " (" $(atoi $ip) ")"
  digest=$(atoi $ip | openssl dgst -sha512)
  if [ "$goal" = "$digest" ]
    then echo "Success. The answer is: " $ip; exit
  fi
done