Prog
The description of the challenge is rather long, and is available in deadalus.md
Host : prog.heroctf.fr
Port : 7000
Format : Hero{flag}
Author : Log_s
The following script allows you to solve the challenge. If the comments are not clear enough, you can contact me on discord for a more detailed explanation.
from copy import deepcopy
from pwn import *
host = "localhost"
port = 7002
def getNext(grid, x, y):
h,w = len(grid), len(grid[0])
# Depending on the symbole, loop until we hit the grid's border, or another symbol
match grid[y][x]:
case "R":
for p in range(1, w-x):
if grid[y][x+p] != ".":
return x+p, y
case "L":
for p in range(1, x+1):
if grid[y][x-p] != ".":
return x-p, y
case "D":
for p in range(1, h-y):
if grid[y+p][x] != ".":
return x, y+p
case "U":
for p in range(1, y+1):
if grid[y-p][x] != ".":
return x, y-p
# If no symbol has been returned, return (-1, -1) to indicate we hit a border
return -1, -1
def find(grid, x, y, loop=None):
# If it's the first call, create an empty list
if loop == None:
loop = []
# Add current node to list
loop.append((x, y))
# Get the coordinates of the of the next symbole, (-1, -1) if the border was hit)
nx, ny = getNext(grid, x, y)
if (nx, ny) == (-1, -1): # Border was hit
return None
elif (nx, ny) == (loop[0][0], loop[0][1]): # Back to first node, end of recursivity
return sorted(loop)
elif (nx, ny) in loop: # Already encountered node, but not the first, provent infinite loop
return None
elif grid[ny][nx] in ["R", "L", "U", "D"]: # New node, subcall
return find(grid, nx, ny, loop)
else: # Special gateways
loop.pop()
grid1 = deepcopy(grid)
grid2 = deepcopy(grid)
if grid[ny][nx] == "-": # for -
if grid[y][x] in ["R", "L"]: # Don't count if arriving from left or right
return None
grid1[ny][nx] = "R"
grid2[ny][nx] = "L"
else: # for |
if grid[y][x] in ["U", "D"]: # Don't count if arriving from up or down
return None
grid1[ny][nx] = "U"
grid2[ny][nx] = "D"
loop1 = find(grid1, x, y, deepcopy(loop))
loop2 = find(grid2, x, y, deepcopy(loop))
# Choose the grid to return
if loop1 == None and loop2 == None:
return None
elif loop1 == None:
return loop2
else:
return loop1
def count_loops(grid):
h, w = len(grid), len(grid[0])
loops = []
for y in range(h):
for x in range(w):
if grid[y][x] != ".":
l = find(grid, x, y)
if l not in loops and l != None:
loops.append(l)
return len(loops)
def get_grid(socket):
data = socket.recvuntil(b"Answer >> ").decode()
print(data)
grid_raw = data.split("===")[2].split("Answer >> ")[0].strip()
lines = grid_raw.split("\n")
grid = []
for line in lines:
grid.append([x for x in line])
return grid
if __name__ == "__main__":
r = remote(host, port)
for i in range(6):
grid = get_grid(r)
nb_loops = str(count_loops(grid))
r.sendline(nb_loops.encode())
print(nb_loops)Hero{h0w_aM4ZEiNg_y0U_d1D_17_3v3n_beTt3R_th4n_4ri4dne}