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intro.py
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intro.py
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from pwn import *
context.clear(arch='i386')
c = constants
assembly = 'read:' + shellcraft.read(c.STDIN_FILENO, 'esp', 1024)
assembly += 'ret\n'
# Let's provide some simple gadgets:
assembly += 'add_esp: add esp, 0x10; ret\n'
# And perhaps a nice "write" function.
assembly += 'write: enter 0,0\n'
assembly += ' mov ebx, [ebp+4+4]\n'
assembly += ' mov ecx, [ebp+4+8]\n'
assembly += ' mov edx, [ebp+4+12]\n'
assembly += shellcraft.write('ebx', 'ecx', 'edx')
assembly += ' leave\n'
assembly += ' ret\n'
assembly += 'flag: .asciz "The flag"\n'
# And a way to exit cleanly.
assembly += 'exit: ' + shellcraft.exit(0)
binary = ELF.from_assembly(assembly)
# Finally, let's build our ROP stack
rop = ROP(binary)
rop.write(c.STDOUT_FILENO, binary.symbols['flag'], 8)
rop.exit()
print rop.dump()
'''
0x0000: 0x10000012 write(STDOUT_FILENO, 268435494, 8)
0x0004: 0x1000000e <adjust: add esp, 0x10; ret>
0x0008: 0x1 arg0
0x000c: 0x10000026 flag
0x0010: 0x8 arg2
0x0014: 'faaa' <pad>
0x0018: 0x1000002f exit()
0x001c: 'haaa' <pad>
'''
# The raw data from the ROP stack is available via str.
raw_rop = str(rop)
print enhex(raw_rop)
'''
120000100e000010010000002600001008000000666161612f00001068616161
'''
# Let's try it out!
p = process(binary.path)
p.send(raw_rop)
print p.recvall(timeout=5)
'''
The flag
'''