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| #!/usr/bin/env python3
# -*- coding: utf-8 -*-
import struct
from typing import List, Tuple
C1 = 1071031968 # 0x3FCCE420
C2 = 0xFD714A3E
C3 = 0x73F96656
C4 = 391575037 # 0x1753D7FD
C5 = 0x724A13FF
S_BOX_BYTES = bytes([
0x67, 0xfc, 0x44, 0xd3, 0xb7, 0xbd, 0x10, 0x22,
0x00, 0x9c, 0xbb, 0x76, 0xde, 0xb5, 0xf1, 0x53,
0x7f, 0x97, 0x1a, 0x82, 0x73, 0x16, 0xb0, 0xf5,
0x27, 0x66, 0x40, 0x2a, 0x3c, 0x49, 0x5f, 0x93,
0xc1, 0x47, 0x83, 0xb9, 0x4a, 0x27, 0xad, 0xe1,
0xce, 0x39, 0x8b, 0xf6, 0x09, 0x71, 0xb7, 0xbc,
0xaf, 0x07, 0x82, 0xae, 0x5a, 0x2f, 0xf5, 0x54,
0xb7, 0xac, 0x87, 0x24, 0xbd, 0x52, 0xaa, 0x2b,
0x9f, 0x5b, 0xa4, 0xd7, 0xc7, 0x82, 0x3d, 0xb9,
0x41, 0xf0, 0xfb, 0x77, 0x0c, 0x53, 0x47, 0x17,
0xee, 0x3d, 0xa6, 0x7e, 0x43, 0x03, 0xad, 0x8b,
0xd3, 0x2b, 0x82, 0x38, 0x9d, 0x9e, 0x6b, 0x80,
0xcf, 0x25, 0x25, 0x24, 0xbe, 0x96, 0x5d, 0x1f,
0x54, 0x45, 0xdb, 0x1a, 0xd0, 0x28, 0xb6, 0x47,
0x58, 0xa3, 0xc9, 0x77, 0x13, 0xd9, 0x43, 0x3c,
0xd3, 0x65, 0x11, 0x71, 0x6e, 0xea, 0xfd, 0x1a,
0x26, 0x6f, 0xef, 0x57, 0x7e, 0xb3, 0xcd, 0x75,
0xde, 0x80, 0x86, 0xf0, 0x62, 0xd5, 0xaa, 0x7e,
0x43, 0x92, 0xba, 0x7a, 0x20, 0x33, 0xaf, 0x45,
0xb2, 0x16, 0xf8, 0xf7, 0xd1, 0xc8, 0xd5, 0x3d,
0xf6, 0x51, 0x82, 0x6d, 0xd0, 0xe5, 0x06, 0x76,
0x31, 0xed, 0xdc, 0x38, 0x0b, 0x26, 0xa1, 0x7f,
0x02, 0xf2, 0xef, 0xba, 0x1d, 0x5e, 0xd8, 0xd9,
0x00, 0x37, 0x58, 0x5e, 0x5f, 0xcc, 0xdf, 0x35,
0xbb, 0x9a, 0x68, 0x1b, 0x67, 0xbb, 0x2b, 0x1b,
0x75, 0x63, 0x50, 0xcf, 0x68, 0x42, 0x3d, 0x3a,
0x1b, 0x14, 0xa5, 0x46, 0x6c, 0x13, 0xe3, 0x7f,
0x72, 0xf6, 0x86, 0x3e, 0xee, 0x8e, 0x0b, 0x8a,
0xd7, 0x7c, 0xd8, 0x33, 0xa9, 0x0e, 0xa5, 0xd4,
0xdd, 0xfc, 0x7a, 0xc7, 0x4d, 0xd7, 0xc0, 0xcd,
0xbc, 0xf0, 0xb6, 0xe0, 0xc7, 0xe9, 0xc0, 0x66,
0x11, 0xb8, 0x94, 0xd4, 0x81, 0x8a, 0x1d, 0x9d,
0xb6, 0x00, 0x7c, 0x14, 0xe4, 0xc3, 0x60, 0xdf,
0xf8, 0x12, 0xa1, 0x5f, 0x9a, 0x22, 0x86, 0x71,
0x37, 0xdc, 0xdc, 0x7f, 0x6b, 0xfe, 0x35, 0x14,
0xa5, 0x12, 0x71, 0xf9, 0x6c, 0x30, 0x79, 0xea
])
# 转换为DWORD数组（小端序）
S_BOX = [struct.unpack('<I', S_BOX_BYTES[i:i+4])[0] for i in range(0, len(S_BOX_BYTES), 4)]
IV_BYTES = bytes([0xb2, 0xe8, 0x87, 0xbe, 0x92, 0xf3, 0xe9, 0x88, 0xc3, 0x40, 0xfb, 0x16])
IV = [struct.unpack('<I', IV_BYTES[i:i+4])[0] for i in range(0, len(IV_BYTES), 4)]
ENC_DATA = bytes([
0xc7, 0xc9, 0x4c, 0x95, 0x6f, 0xbf, 0xc9, 0xf4,
0xc4, 0x86, 0xa4, 0x20, 0x57, 0x55, 0x6b, 0xe2,
0xea, 0xdc, 0xb7, 0x3f, 0x9c, 0x42, 0x1e, 0xe1,
0x72, 0x82, 0x0d, 0x93, 0xb3, 0xf9, 0xd0, 0x35,
0x93, 0x70, 0xff, 0x44, 0x72, 0x61, 0x55, 0xf8,
0xec, 0xda, 0xfb, 0x6e, 0xa8, 0xa6, 0xcb, 0x9e
])
def f_function(x: int) -> int:
"""
F函数 (sub_7FF750BE1450)
逆向伪代码：
return ((((a1 + C1) ^ C2) + C3) ^ C4) - C5
"""
x = (x + C1) & 0xFFFFFFFF
x = (x ^ C2) & 0xFFFFFFFF
x = (x + C3) & 0xFFFFFFFF
x = (x ^ C4) & 0xFFFFFFFF
x = (x - C5) & 0xFFFFFFFF
return x
def f_inverse(y: int) -> int:
"""
F函数的逆函数
逆向操作序列（从后往前）：
"""
y = (y + C5) & 0xFFFFFFFF
y = (y ^ C4) & 0xFFFFFFFF
y = (y - C3) & 0xFFFFFFFF
y = (y ^ C2) & 0xFFFFFFFF
y = (y - C1) & 0xFFFFFFFF
return y
def bytes_to_dwords(data: bytes) -> List[int]:
"""将字节数组转换为DWORD数组（小端序）"""
dwords = []
for i in range(0, len(data), 4):
if i + 4 <= len(data):
dwords.append(struct.unpack('<I', data[i:i+4])[0])
else:
remaining = data[i:] + b'\x00' * (4 - len(data[i:]))
dwords.append(struct.unpack('<I', remaining)[0])
return dwords
def dwords_to_bytes(dwords: List[int], length: int) -> bytes:
"""将DWORD数组转换回字节数组"""
result = b''
for dword in dwords:
result += struct.pack('<I', dword)
return result[:length]
def decrypt_block(enc_block: Tuple[int, int, int], s_box: List[int]) -> Tuple[int, int, int]:
"""
解密一个3-DWORD块（逆向72轮Feistel结构）
加密轮函数（从IDA分析）：
for n71 = 0 to 71:
v3 = size_[n71]
temp = (size_[n71+2] ^ size_[n71+1]) ^ s_box[n71]
v4 = v3 ^ F(temp)
size_[n71+3] = F(v4)
解密轮函数（逆向）：
for n71 = 71 down to 0:
temp = (size_[n71+2] ^ size_[n71+1]) ^ s_box[n71]
size_[n71] = F_inv(size_[n71+3]) ^ F(temp)
参数：
enc_block: 加密后的3个DWORD (size_[72], size_[73], size_[74])
s_box: S盒数组
返回：
解密后的3个DWORD (size_[0], size_[1], size_[2])
"""
size = [0] * 75
# 最后3个值是已知的（加密后的值）
size[72], size[73], size[74] = enc_block
# 从第71轮逆向到第0轮
for i in range(71, -1, -1):
temp = (size[i+2] ^ size[i+1]) ^ s_box[i]
size[i] = (f_inverse(size[i+3]) ^ f_function(temp)) & 0xFFFFFFFF
return (size[0], size[1], size[2])
def decrypt_full(enc_data: bytes, s_box: List[int], iv: List[int]) -> bytes:
# 步骤1: 转换为DWORD数组
enc_dwords = bytes_to_dwords(enc_data)
count = len(enc_dwords)
print(f"[*] 加密数据: {count} DWORDs")
# 步骤2: 逆向CBC模式
# CBC模式：C[i] = E(P[i] XOR C[i-1]), C[-1] = IV
# 解密：P[i] = D(C[i]) XOR C[i-1]
cbc_reversed = enc_dwords.copy()
# 从后往前，每个DWORD与前面第3个DWORD异或（因为块大小是3）
for i in range(count - 1, 2, -1):
cbc_reversed[i] = (cbc_reversed[i] ^ cbc_reversed[i - 3]) & 0xFFFFFFFF
# 前3个与IV异或
for i in range(min(3, count)):
cbc_reversed[i] = (cbc_reversed[i] ^ iv[i]) & 0xFFFFFFFF
print(f"[*] CBC逆向完成")
# 步骤3: 对每个3-DWORD块进行解密
decrypted = []
num_blocks = (count + 2) // 3
for i in range(num_blocks):
# 提取一个块（3个DWORD）
block = []
for j in range(3):
idx = i * 3 + j
if idx < count:
block.append(cbc_reversed[idx])
else:
block.append(0)
# 解密这个块
dec_block = decrypt_block(tuple(block), s_box)
decrypted.extend(dec_block)
print(f"[*] 块解密完成: {num_blocks} 块")
# 步骤4: 转换回字节
result = dwords_to_bytes(decrypted, len(enc_data))
return result
def main():
print("=" * 70)
print("尤皮·埃克斯历险记（2） - 逆向解密脚本")
print("=" * 70)
print()
print(f"[*] S盒: {len(S_BOX)} DWORDs")
print(f"[*] IV: {[hex(x) for x in IV]}")
print(f"[*] 密文长度: {len(ENC_DATA)} 字节")
print()
# 执行解密
plain = decrypt_full(ENC_DATA, S_BOX, IV)
print()
print("=" * 70)
print("解密结果")
print("=" * 70)
print()
# 转换为DWORD查看
plain_dwords = bytes_to_dwords(plain)
print(f"解密得到的DWORD ({len(plain_dwords)}个):")
for i, dw in enumerate(plain_dwords):
print(f" [{i:02d}] 0x{dw:08X}")
# 关键发现：每个DWORD的第0个字节包含flag
print()
print("=" * 70)
print("FLAG提取")
print("=" * 70)
print()
print("[*] 提取每个DWORD的各字节位置:")
byte_positions = [[], [], [], []]
for dw in plain_dwords:
byte_positions[0].append((dw >> 0) & 0xFF)
byte_positions[1].append((dw >> 8) & 0xFF)
byte_positions[2].append((dw >> 16) & 0xFF)
byte_positions[3].append((dw >> 24) & 0xFF)
for i, pos_bytes in enumerate(byte_positions):
b = bytes(pos_bytes)
printable = ''.join(chr(x) if 32 <= x < 127 else '.' for x in pos_bytes)
printable_count = sum(1 for x in b if 32 <= x < 127)
print(f" 位置{i}: {b.hex()} ({printable}) [{printable_count}/12可打印]")
# 提取FLAG - 方法1：每个DWORD的第0字节
flag_bytes_pos0 = bytes(byte_positions[0])
# 提取FLAG - 方法2：直接转换DWORD为字符串（小端序）
print()
print("[*] 直接从DWORD转换（小端序）:")
flag_from_dwords = b''
for dw in plain_dwords:
flag_from_dwords += struct.pack('<I', dw)
print(f" 十六进制: {flag_from_dwords.hex()}")
try:
flag_direct = flag_from_dwords.decode('ascii')
print(f" ASCII: {flag_direct}")
except:
printable = ''.join(chr(b) if 32 <= b < 127 else '.' for b in flag_from_dwords)
print(f" 可打印: {printable}")
print()
print("=" * 70)
# 检查哪个是正确的flag
if flag_from_dwords[:5] == b'flag{':
print(f"[+] FLAG: {flag_from_dwords.decode('ascii')}")
elif flag_bytes_pos0[:5] == b'flag{':
try:
print(f"[+] FLAG: {flag_bytes_pos0.decode('ascii')}")
except:
printable = ''.join(chr(b) if 32 <= b < 127 else '.' for b in flag_bytes_pos0)
print(f"[+] FLAG (可打印字符): {printable}")
else:
print(f"[+] FLAG候选1 (直接转换): {flag_from_dwords.decode('ascii', errors='replace')}")
print(f"[+] FLAG候选2 (位置0): {flag_bytes_pos0.hex()}")
print("=" * 70)
if __name__ == "__main__":
main()
|
