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Based

Based

Challenge

To get truly 1337, you must understand different data encodings, such as hexadecimal or binary. Can you get the flag from this program to prove you are on the way to becoming 1337? Connect with nc 2019shell1.picoctf.com 20836.

Solution

I used a bash script that utilized perl to convert binary to ascii. I would paste the array in as arguments.

#!/bin/bash

array=("$@")
string=''

for i in "${array[@]}"
do
        string+=$(echo $i | perl -lape '$_=pack"(B8)*",@F')
done

echo $string

A second string is needed and it is octal, so I created another bash script that would take the input and convert it hex, then to ascii, mainly relying on xxd to do the ascii conversion.

#!/bin/bash

array=("$@")
string=''

for i in "${array[@]}"
do
        hex=$(echo "obase=16;ibase=8;$i" | bc)
        string+=$(echo "0x$hex" | xxd -r)
done

echo $string

Next portion was hex, and that was just a stripped version of the previous script.

#!/bin/bash

array=("$@")
string=''

for i in "${array[@]}"
do
        string+=$(echo "0x$i" | xxd -r)
done

echo $string

picoCTF{learning_about_converting_values_6cdcad0d}


Last update: September 28, 2022 07:59:55