BREAKER

Challenge

We are given a binary inside breaker.tar.gz.
The binary copies two arrays from .rodata and runs a loop:

c[i] = A[i] ^ B[i % 77]

The result is the flag, but it is sent to a dummy function and never printed.

Step 1 --- First thoughts

The challenge mentions GDB "chaos", but looking at the disassembly shows a clear XOR loop.
The task is to dump the arrays from .rodata and reconstruct the flag.

Step 2 --- Recovering the arrays

From the binary:

• A has 90 integers\
• B has 77 integers

The flag is produced by XORing A[i] with B[i % 77].

Step 3 --- Exploit script

import struct

bin_path = "rev"
RODATA_VADDR  = 0x473000
RODATA_OFFSET = 0x73000

A_VADDR = 0x4731a0
B_VADDR = 0x473320

with open(bin_path, "rb") as f:
    f.seek(RODATA_OFFSET + (A_VADDR - RODATA_VADDR))
    A = list(struct.unpack("<90i", f.read(90*4)))

    f.seek(RODATA_OFFSET + (B_VADDR - RODATA_VADDR))
    B = list(struct.unpack("<76i", f.read(76*4)))
    f.seek(RODATA_OFFSET + (B_VADDR - RODATA_VADDR) + 76*4)
    B.append(struct.unpack("<i", f.read(4))[0])

C = [A[i] ^ B[i % 77] for i in range(90)]
s = bytes(c & 0xff for c in C).decode("latin1")
print(s.split("}")[0] + "}")

Step 4 --- Result

Running the script gives:

NNS{moves_like_jagger_but_rev}

Flag

NNS{moves_like_jagger_but_rev}

Notes

At first I thought the challenge wanted some GDB trickery because of the description, but it turned out much simpler.
It was basically just about noticing the XOR loop and grabbing the data from .rodata. Once the arrays were dumped, the flag fell out right away. Pretty fun warm‑up style reversing task.