mjhjmtu

I am doing some challenges. This is one them. I am trying to brute-force 4 digit pin with the password to get my desired answer. After connecting to the port It prompts me to enter the password then space then 4 digit pin. I tried to brute-force the pin using the script:

 #!/bin/bash 
 nc localhost 30002 
 sleep 2 

 for i in 0000..9999; 
 if [[ $(echo 'UoMYTrfrBFHyQXmg6gzctqAwOmw1IohZ $i' </dev/stdin) = ^Wrong*]]; 
 then 
 continue 
 echo '[+] Pincode Cracked! Pincode = $i' 
 fi 
 done

but it seems that this doesn't input the pass and pin to stdin, before i tried doing something like this -> if [[ $(echo 'UoMYTrfrBFHyQXmg6gzctqAwOmw1IohZ $i') = ^Wrong* ]]; What am I doing wrong here?

UPDATE:

Okay, so after researching around. I wrote this:

for i in 0000..9999
do
if [ (echo "UoMYTrfrBFHyQXmg6gzctqAwOmw1IohZ $i" | nc localhost 30002 | grep -o Wrong) == "Wrong" ]
then
sleep 0.1
continue
fi
echo "- - - - - - - - - - - - - - - - - - - - - - - - [$i]"
done

This might even work but as you can see it opens new connections in the loop which makes it really slow and exhaust the system.

That's because you're not telling your script to write anything to nc's standard input. Your script starts netcat, waits for it to terminate, and then sleeps for two seconds before executing the for loop. You probably want a construct such as:

for i in 0000..9999; do
 : stuff
done | nc localhost 30002

for i in 0000..9999; do echo "UoMYTrfrBFHyQXmg6gzctqAwOmw1IohZ $i" | nc localhost 30002; done