90 lines
2.7 KiB
Python
90 lines
2.7 KiB
Python
import subprocess
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# Build a self-modifying thinga-ma-jig
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def run_command(cmd):
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proc = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE,
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stderr=subprocess.PIPE, stdin=subprocess.PIPE)
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stdoutput = proc.stdout.read() + proc.stderr.read()
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return stdoutput
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def build_bin(name):
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print(run_command('fasm %s.asm' % name))
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def create_xor_block(last_shellcode_block, next_shellcode_block):
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block = bytearray(b'')
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for x in range(0, len(last_shellcode_block)): # each shellcode block should be 512 bytes
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block.append((last_shellcode_block[x]) ^ (next_shellcode_block[x]))
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return bytes(block)
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def get_shellcode_block(name):
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build_bin(name)
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f = open('%s.bin' % name, 'rb')
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out = f.read()
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f.close()
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return out
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shellcode_files = ['first', 'second', 'third', 'fourth', 'last']
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shellcode_blocks = [get_shellcode_block('base_block')]
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morpher_file = 'morpher'
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morpher_template = 'morpher.template.asm'
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xor_blocks = []
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xor_block_files = []
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def build_shellcode_files():
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for x in shellcode_files:
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shellcode_blocks.append(get_shellcode_block(x))
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def gen_xor_blocks():
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for x in range(0, len(shellcode_files)):
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xor_block = create_xor_block(shellcode_blocks[x], shellcode_blocks[x+1])
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xor_blocks.append(xor_block)
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f = open('b%d.bin' % x, 'wb')
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f.write(xor_block)
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f.close()
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xor_block_files.append('b%d.bin' % x)
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def create_morpher_file():
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_mrph = 'file \'base_block.bin\'\n'
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_data = ''
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_block_list = ''
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for x in xor_block_files:
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_data += '%s: file \'%s\'\n' % (x, x)
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_block_list += '%s, ' % x
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_data += 'block_ptrs dd %s0' % _block_list
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f = open(morpher_template, 'rb')
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template = f.read().decode('utf-8')
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f.close()
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result = template % (_mrph, _data)
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f = open('%s.asm' % morpher_file, 'wb')
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f.write(result.encode('utf-8'))
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f.close()
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# The morpher has 3 sections, modifiable code, static code (morphing), data
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# Modifiable code will be where each shellcode segment is done
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# Static code has the morpher that sets up each shellcode segment
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# Data has the XOR block pointers and indicies for the ones to use in order
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# Begins by the morpher creating the first shellcode block, setting it up, then running it
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# continues until the final block that will print the flag
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# Kinda like a binary bomb but in one binary
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# On entrance to each shellcode segment the ebx register will be a vtable of std funcs
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# printf
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# puts
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# scanf
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# esi contains the base address of the shellcode segment
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# edi contains the address of the part of the flag that this segment fills
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# edx contains the number of the block
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build_shellcode_files()
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gen_xor_blocks()
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create_morpher_file()
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build_bin(morpher_file)
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#print(create_xor_block(b'123', b'321'))
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#print(get_shellcode_block('shellcode'))
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