DNA - smileyCTF 2025

pycファイルが与えられる

PyLingualでデコンパイルしたが、さらにバイトコードが格納されていそう

pycをディスアセンブルするくん

code:python

import dis

import marshal

print(''.join(chr(k) for k in keys))

for i in range(len(v)):

print('===')

print(dis.dis(result))

.dnaファイルをディスアセンブルするくん

code:python

import sys

s = []

m = {}

nm = {'A': 0, 'T': 1, 'G': 2, 'C': 3}

if len(sys.argv)!= 2:

sys.exit(1)

pc = 0

while pc < len(code):

print(pc, end=' ')

if pri == 0: # push

print(f'push {pro}')

pc += 12

elif pri == 1: # pop

print('pop')

pc += 2

elif pri == 2: # load

pc += 12

elif pri == 3: # store

pc += 12

elif pri == 4: # add

print('add')

pc += 2

elif pri == 5: # sub

print('sub')

pc += 2

elif pri == 6: # mul

print('mul')

pc += 2

elif pri == 7: # rem

print('rem')

pc += 2

elif pri == 8: # eq

print('eq')

pc += 2

elif pri == 9: # jmp

print(f'jmp {pro}')

pc += 12

elif pri == 10: # jz

print(f'jz {pro}')

pc += 12

elif pri == 11: # jnz

print(f'jnz {pro}')

pc += 12

elif pri == 12: # print

print('print')

pc += 2

elif pri == 13: # call

print('call')

pc += 2

elif pri == 14: # swap

print('swap')

pc += 2

elif pri == 15:

print('exit')

pc += 2

# break

code:python

import marshal

import sys

from z3 import *

s = []

m = {}

nm = {'A': 0, 'T': 1, 'G': 2, 'C': 3}

if len(sys.argv)!= 2:

sys.exit(1)

solver = Solver()

for i in range(len(flag)):

pc = 0

while pc < len(code):

if pc == 69048:

assert solver.check() == sat

m = solver.model()

print(f'.;,;.{{{flag}}}')

exit()

if pri == 0: # push

s.append(pro)

pc += 12

elif pri == 1: # pop

if not s:

raise Exception('Stack underflow')

s.pop()

pc += 2

elif pri == 2: # load

if pro not in m:

raise Exception(f'Uninitialized memory access at {pro}')

pc += 12

elif pri == 3: # store

if not s:

raise Exception('Stack underflow')

pc += 12

elif pri == 4: # add

if len(s) < 2:

raise Exception('Stack underflow')

a, b = (s.pop(), s.pop())

s.append(a + b)

pc += 2

elif pri == 5: # sub

if len(s) < 2:

raise Exception('Stack underflow')

a, b = (s.pop(), s.pop())

s.append(b - a)

pc += 2

elif pri == 6: # mul

if len(s) < 2:

raise Exception('Stack underflow')

a, b = (s.pop(), s.pop())

s.append(a * b)

pc += 2

elif pri == 7: # rem

if len(s) < 2:

raise Exception('Stack underflow')

a, b = (s.pop(), s.pop())

if a == 0:

raise Exception('Division by zero')

s.append(b % a)

pc += 2

elif pri == 8: # eq

if len(s) < 2:

raise Exception('Stack underflow')

a, b = (s.pop(), s.pop())

s.append(1 if a == b else 0)

solver.append(a == b)

pc += 2

elif pri == 9: # jmp

pc = pro

elif pri == 10: # jz

if not s:

raise Exception('Stack underflow')

if s.pop() == 1:

pc = pro

else: # inserted

pc += 12

elif pri == 11: # jnz

if not s:

raise Exception('Stack underflow')

if s.pop()!= 1:

pc = pro

else: # inserted

pc += 12

elif pri == 12: # print

if not s:

raise Exception('Stack underflow')

print(chr(s.pop()), end='')

pc += 2

elif pri == 13: # call

if not s:

raise Exception('Stack underflow')

key = keys.pop(0)

solver.add(s.pop() == key)

def f():

return

f()

pc += 2

elif pri == 14: # swap

if len(s) < 2:

raise Exception('Stack underflow')

a, b = (s.pop(), s.pop())

if a not in nm or b not in nm:

raise Exception('Invalid')

pc += 2

elif pri == 15:

break