Website: https://ieee-buet-ctf.web.app/
Yesterday, I had participated in CTF Super League: CTF Competition for Beginners- the first CTF competition of my life. During the competition, I could solve around 5 problems. The solution writeup are given below:
Basic Problems
Problem B
Description
You have to find the flag from the file linked below.
Solution
A basic string search for "IEEE_BUET{" gives out the flag IEEE_BUET{WHO_COULD_HAVE_DONE_THIS}
Problem C
Description
You have to find the flag from the image linked below.
Solution
After downloading the file, a basic cat command prints out the img.png file content. At the bottom, we can see the flag IEEE_BUET{I_AM_BEAN}
Cryptography
Problem C
Description
Decode the following while rome was burning.
guvf vf fvzcyr
Solution
A simple ROT-13 encryption gives us the message
this is simple.
Reverse Engineering
Problem A
Description
You have to investigate following file and find the flag.
Solution
A simple file command on the file gives us the following output:
ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, BuildID[sha1]=e842fd921c0649de7bdceb6461c0bf52471ae3ba, for GNU/Linux 3.2.0, not stripped
Meaning it's an object file built for GNU/Linux platform. Let's try executing the file.
chmod +x revme
./revme
>> capture{>49?x1+x67,x,09,x+15(4=}
And thus it gives out the flag.
Problem E
Description
You have to investigate following file and find the flag.
Solution
Since it's a JAR file, let's extract it. Extracting the JAR file and going inside the com/khabib97 folder shows the compiled JAVA bytecode. Opening those .class files using a Java decompiler or even with IntelliJ gives us the source code.
// Deadend.class
public class DeadEnd {
String value;
public DeadEnd() {
this.value = Plug.three + Plug.one + Plug.two;
}
}
// Plug.class
public final class Plug {
public static String one = "asewd";
public static String two = "sfgrr";
public static String three = "$4qe123";
public Plug() {
}
}
From these two source codes, we can now easily construct the string $4qe123asewdsfgrr.
That's our flag.