Dead Reckoning

#!/usr/bin/env python3
from pathlib import Path
import re, math
import numpy as np
import cv2

fw = Path("controller_fw.bin").read_bytes()

# 1) parse 4 packets from job buffer
off = 0x100C
segments = []
for _ in range(4):
    ln = int.from_bytes(fw[off:off+4], "little")
    sid = fw[off+4]
    data = fw[off+5:off+5+ln]
    segments.append((sid, data))
    off += 5 + ln

# 2) key from cal_reserved offset
key = fw[0x0C18:0x0C20]  # f1 4c 3b a7 2e 91 c4 08

def xor_rep(data, key):
    return bytes(b ^ key[i % len(key)] for i, b in enumerate(data))

dec = b"".join(xor_rep(d, key) for _, d in sorted(segments, key=lambda x: x[0]))
Path("controller_job_dec.bin").write_bytes(dec)

text = dec.decode("ascii", errors="ignore")
print("--- GCODE PREVIEW ---")
print("\n".join(text.splitlines()[:20]))

# 3) render toolpath
lines = [ln.strip() for ln in text.splitlines() if ln.strip() and not ln.strip().startswith("(") and ln.strip() != "%"]

x = y = z = 0.0
draw_segments = []

for ln in lines:
    m = re.search(r"G(\d\d)", ln)
    cmd = "G" + m.group(1) if m else None
    p = {k: float(v) for k, v in re.findall(r"([XYZIJF])(-?\d+(?:\.\d+)?)", ln)}

    nx, ny, nz = p.get("X", x), p.get("Y", y), p.get("Z", z)
    if "Z" in p:
        z = nz
    cut = z < 0

    if cmd in ("G00", "G01"):
        if "X" in p or "Y" in p:
            if cut:
                draw_segments.append(((x, y), (nx, ny)))
            x, y = nx, ny

    elif cmd in ("G02", "G03"):
        I, J = p.get("I", 0.0), p.get("J", 0.0)
        cx, cy = x + I, y + J
        r = math.hypot(x - cx, y - cy)
        a0 = math.atan2(y - cy, x - cx)
        a1 = math.atan2(ny - cy, nx - cx)
        cw = cmd == "G02"
        if cw and a1 >= a0:
            a1 -= 2 * math.pi
        if (not cw) and a1 <= a0:
            a1 += 2 * math.pi

        steps = max(16, int(abs(a1 - a0) * max(r, 1) / 0.5))
        px, py = x, y
        for i in range(1, steps + 1):
            a = a0 + (a1 - a0) * i / steps
            qx, qy = cx + r * math.cos(a), cy + r * math.sin(a)
            if cut:
                draw_segments.append(((px, py), (qx, qy)))
            px, py = qx, qy
        x, y = nx, ny

pts = np.array([p for s in draw_segments for p in s], dtype=np.float64)
minx, miny = pts.min(axis=0)
maxx, maxy = pts.max(axis=0)

scale, pad = 8, 20
W = int((maxx - minx) * scale + 2 * pad)
H = int((maxy - miny) * scale + 2 * pad)
img = np.full((H, W), 255, np.uint8)

def tr(pt):
    xx = int(round((pt[0] - minx) * scale + pad))
    yy = int(round((maxy - pt[1]) * scale + pad))
    return xx, yy

for a, b in draw_segments:
    cv2.line(img, tr(a), tr(b), 0, 2, cv2.LINE_AA)

cv2.imwrite("controller_job_render.png", img)
print("Saved controller_job_render.png")
print("Visually read text as: f'GS")
print("Flag: apoorvctf{f'GS}")