HackTheBox Golfer Challenge

Explore the basics of cybersecurity in the Golfer Challenge on Hack The Box. This easy-level Challenge introduces encryption reversal and file handling concepts in a clear and accessible way, perfect for beginners.

https://app.hackthebox.com/challenges/378

Description#

A friend gave you an odd executable file, in fact it is very tiny for a simple ELF, what secret can this file hide?

Exploitation#

Steps Taken for Binary Modification#

Using Hexadecimal Editing:#

Dump the binary to a hexadecimal file for editing:
```
xxd -p golfer > golfer.hex
```
Edit the hexadecimal file:
- Open golfer.hex in a text editor.
- Locate and replace the sequence e9d6000000 with e900000000 to modify the binary’s behavior.
Rebuild the patched binary from the edited hexadecimal file:
```
xxd -r -p golfer.hex golfer.patched
```
Set execute permissions on the new binary:
```
chmod +x golfer.patched
```
Run the patched binary to observe the changes:
```
./golfer.patched
```

Using radare2:#

Open the binary with radare2 with relocation adjustments and write permissions:
```
sudo r2 -e bin.relocs.apply=true -w ./golfer
```

Navigate to the specific address and modify the instruction:

s 0x0800004c    # Seek to the desired address
pd 1            # Display the current instruction
wao nop         # Replace the instruction with NOP
pd 1            # Display the modified instruction
q               # Quit radare2

Execute the modified binary:
```
./golfer
```

Summary#

The Golfer Challenge provides a hands-on introduction to basic exploitation and file manipulation techniques. By manipulating the assembly, you can navigate to where the flag is hidden. This challenge is a great starting point for beginners in cybersecurity.