def visit_MLIL_LOAD_SSA(self, expr):
src = self.visit(expr.src)
if src is None:
return
memory = self._memory
# we're assuming Little Endian for now
if expr.size == 1:
return memory[src]
elif expr.size == 2:
return Concat(memory[src+1], memory[src])
elif expr.size == 4:
return Concat(
memory[src+3],
memory[src+2],
memory[src+1],
memory[src]
)
elif expr.size == 8:
return Concat(
memory[src+7],
memory[src+6],
memory[src+5],
memory[src+4],
memory[src+3],
memory[src+2],
memory[src+1],
memory[src]
)
def mload(self, offset: BitVecNumRef):
if isinstance(offset, BitVecNumRef):
offset = offset.as_long()
elif not isinstance(offset, int):
raise DevelopmentErorr(
'Does not support memory operations indexed by symbol variables.'
)
if offset + WORDBYTESIZE > len(self.__immediate_data):
# ~ index out of bounds ~
# generate a symblolic variable
newmemvar = self.__generateMemoryVar()
d = offset + WORDBYTESIZE - len(self.__immediate_data)
if d < WORDBYTESIZE:
for i in range(d):
self.__immediate_data.append(
Extract((d - i - 1) * 8 + 7, (d - i - 1) * 8,
newmemvar))
return simplify(
Concat(self.__immediate_data[offset:WORDBYTESIZE +
offset]))
else:
self.mstore(BitVecVal256(offset), newmemvar)
return newmemvar
else:
return simplify(
Concat(self.__immediate_data[offset:WORDBYTESIZE + offset]))
def right_one_extension(formula, bit_places):
"""Set the rest of bits on the right to 1.
"""
complement = BitVecVal(0, formula.size() - bit_places) - 1
formula = Concat(
Extract(formula.size() - 1,
formula.size() - bit_places, formula), complement)
return formula
def is_byte_swap(self):
try:
self.model_variable()
except ModelIsConstrained:
return False
# Figure out if this might be a byte swap
byte_values_len = len(self.byte_values)
#print self.byte_values
if 1 < byte_values_len <= self.var.src.var.type.width:
var = create_BitVec(self.var.src, self.var.src.var.type.width)
ordering = list(reversed([
self.byte_values[x]
for x in sorted(self.byte_values.keys())
]))
reverse_var = Concat(
*reversed([
Extract(i-1, i-8, var)
for i in range(len(ordering) * 8, 0, -8)
])
)
if len(ordering) < 4:
reverse_var = Concat(
Extract(
31,
len(ordering)*8, var
),
reverse_var
)
reversed_ordering = reversed(ordering)
reversed_ordering = Concat(*reversed_ordering)
# The idea here is that if we add the negation of this, if it's
# not satisfiable, then that means there is no value such that
# the equivalence does not hold. If that is the case, then this
# should be a byte-swapped value.
self.solver.add(
Not(
And(
var == ZeroExt(
var.size() - len(ordering)*8,
Concat(*ordering)
),
reverse_var == ZeroExt(
reverse_var.size() - reversed_ordering.size(),
reversed_ordering
)
)
)
)
if self.solver.check() == unsat:
return True
return False
def sign_extension(formula, bit_places):
"""Set the rest of bits on the left to the value of the sign bit.
"""
sign_bit = Extract(bit_places - 1, bit_places - 1, formula)
complement = sign_bit
for _ in range(formula.size() - bit_places - 1):
complement = Concat(sign_bit, complement)
formula = Concat(complement, (Extract(bit_places - 1, 0, formula)))
return formula
def right_sign_extension(formula, bit_places):
"""Set the rest of bits on the right to the value of the sign bit.
"""
sign_bit_position = formula.size() - bit_places
sign_bit = Extract(sign_bit_position, sign_bit_position, formula)
complement = sign_bit
for _ in range(sign_bit_position - 1):
complement = Concat(sign_bit, complement)
formula = Concat(Extract(formula.size() - 1, sign_bit_position, formula),
complement)
return formula
def zero_extension(formula, bit_places):
"""Set the rest of bits on the left to 0.
"""
complement = BitVecVal(0, formula.size() - bit_places)
formula = Concat(complement, (Extract(bit_places - 1, 0, formula)))
return formula
def test_instruction_semantics_call(self):
# call #0xdead
raw = b'\xb0\x12\xad\xde'
ip = 0xc0de
ins, _ = decode_instruction(ip, raw)
state = blank_state()
state.cpu.registers['R0'] = BitVecVal(ip + len(raw),
16) # ip preincrement
state.cpu.registers['R1'] = BitVecVal(0x1234, 16)
new_states = state.cpu.step_call(state, ins)
self.assertEqual(len(new_states), 1)
new_state = new_states[0]
lo = new_state.memory[0x1232]
hi = new_state.memory[0x1233]
pushed_val = Concat(hi, lo)
self.assertEqual(intval(pushed_val), ip + len(raw))
self.assertEqual(intval(new_state.cpu.registers['R1']), 0x1232)
self.assertEqual(intval(new_state.cpu.registers['R0']), 0xdead)
def array_to_bv64(array):
return Concat(Select(array, BitVecVal(7, 32)),
Select(array, BitVecVal(6, 32)),
Select(array, BitVecVal(5, 32)),
Select(array, BitVecVal(4, 32)),
Select(array, BitVecVal(3, 32)),
Select(array, BitVecVal(2, 32)),
Select(array, BitVecVal(1, 32)),
Select(array, BitVecVal(0, 32)))
def set_region_bit(bv, p):
i = region_names.index(REGIONS[p.y][p.x])
chunks = []
if i < bits - 1:
chunks.append(Extract(bits - 1, i + 1, bv))
chunks.append(BitVecVal(1, 1))
if i > 0:
chunks.append(Extract(i - 1, 0, bv))
return Concat(*chunks)
def identity(data: Union[bytes, str, List[int]]) -> bytes:
# Group up into an array of 32 byte words instead
# of an array of bytes. If saved to memory, 32 byte
# words are currently needed, but a correct memory
# implementation would be byte indexed for the most
# part.
return data
result = []
for i in range(0, len(data), 32):
result.append(simplify(Concat(data[i:i + 32])))
return result
def byte_(self, global_state):
mstate = global_state.mstate
op0, op1 = mstate.stack.pop(), mstate.stack.pop()
try:
index = util.get_concrete_int(op0)
offset = (31 - index) * 8
result = Concat(BitVecVal(0, 248), Extract(offset + 7, offset,
op1))
except AttributeError:
logging.debug("BYTE: Unsupported symbolic byte offset")
result = BitVec(str(simplify(op1)) + "_" + str(simplify(op0)), 256)
mstate.stack.append(simplify(result))
return [global_state]
def byte_(self, global_state):
mstate = global_state.mstate
op0, op1 = mstate.stack.pop(), mstate.stack.pop()
if not isinstance(op1, ExprRef):
op1 = BitVecVal(op1, 256)
try:
index = util.get_concrete_int(op0)
offset = (31 - index) * 8
if offset >= 0:
result = simplify(Concat(BitVecVal(0, 248), Extract(offset + 7, offset, op1)))
else:
result = 0
except AttributeError:
logging.debug("BYTE: Unsupported symbolic byte offset")
result = BitVec(str(simplify(op1)) + "[" + str(simplify(op0)) + "]", 256)
mstate.stack.append(result)
return [global_state]
def test_instruction_semantics_push(self):
# push #0xdead
raw = b'\x30\x12\xad\xde'
ip = 0x1234
ins, _ = decode_instruction(ip, raw)
state = blank_state()
state.cpu.registers['R1'] = BitVecVal(0x1234, 16)
new_states = state.cpu.step_push(state, ins)
self.assertEqual(len(new_states), 1)
new_state = new_states[0]
lo = new_state.memory[0x1232]
hi = new_state.memory[0x1233]
pushed_val = Concat(hi, lo)
self.assertEqual(intval(pushed_val), 0xdead)
self.assertEqual(intval(new_state.cpu.registers['R1']), 0x1232)
def __getitem__(self, item):
if isinstance(item, slice):
try:
current_index = (item.start if isinstance(
item.start, BitVecRef) else BitVecVal(item.start, 256))
dataparts = []
while simplify(current_index != item.stop):
dataparts.append(self[current_index])
current_index = simplify(current_index + 1)
except Z3Exception:
raise IndexError("Invalid Calldata Slice")
return simplify(Concat(dataparts))
if self.concrete:
try:
return self._calldata[get_concrete_int(item)]
except IndexError:
return BitVecVal(0, 8)
else:
return self._calldata[item]
def __getitem__(self, item: Union[int, slice]) -> Any:
if isinstance(item, int) or isinstance(item, ExprRef):
return self._load(item)
if isinstance(item, slice):
start = 0 if item.start is None else item.start
step = 1 if item.step is None else item.step
stop = self.size if item.stop is None else item.stop
try:
current_index = (
start if isinstance(start, BitVecRef) else BitVecVal(start, 256)
)
parts = []
while simplify(current_index != stop):
parts.append(self._load(current_index))
current_index = simplify(current_index + step)
except Z3Exception:
raise IndexError("Invalid Calldata Slice")
return simplify(Concat(parts))
raise ValueError
def __getitem__(self, item: Union[int, slice]) -> Any:
if isinstance(item, slice):
start, step, stop = item.start, item.step, item.stop
try:
if start is None:
start = 0
if step is None:
step = 1
if stop is None:
stop = self.calldatasize
current_index = (start if isinstance(start, BitVecRef) else
BitVecVal(start, 256))
dataparts = []
while simplify(current_index != stop):
dataparts.append(self[current_index])
current_index = simplify(current_index + step)
except Z3Exception:
raise IndexError("Invalid Calldata Slice")
values, constraints = zip(*dataparts)
result_constraints = []
for c in constraints:
result_constraints.extend(c)
return simplify(Concat(values)), result_constraints
if self.concrete:
try:
return self._calldata[get_concrete_int(item)], ()
except IndexError:
return BitVecVal(0, 8), ()
else:
constraints = [
Implies(self._calldata[item] != 0, UGT(self.calldatasize,
item))
]
return self._calldata[item], constraints
def BVSignedUpCast(x, n_bits): assert x.size() <= n_bits if x.size() < n_bits: return Concat(If(x < 0, BitVecVal(-1, n_bits - x.size()), BitVecVal(0, n_bits - x.size())), x) else: return x
from pwn import *
import itertools
from z3 import BitVec, BitVecVal, Solver, If, simplify, Concat, Extract, And, Or, LShR, UDiv, sat, Int
from ictf import iCTF
from multiprocessing import Pool
i = iCTF()
team = i.login('*****@*****.**', 'HZBrKynG4XAMvWPa')
BVV = BitVecVal
BV = BitVec
int128 = lambda x: Concat(BVV(0, 64), x)
int64 = lambda x: Extract(63, 0, x)
def weird_op(x):
k = x - (1337331 * LShR(int64(LShR(0x0C8B98A756AA1D561 * int128(x), 64)), 20))
return int64(k)
def choose_op(a1, a2, op):
r = If(op == 0,
a2 + a1,
If(op == 1,
a1 - a2,
If(op == 2,
a2 * a1,
If(op == 3 and a2 != 0,
UDiv(a1, a2),
False
)
)
)
def make_load(src, size):
mem = Array('mem', BitVecSort(32), BitVecSort(8))
load_bytes = [mem[src + i] for i in range(0, size)]
return Concat(*load_bytes)
s = Solver()
flag = [BitVec(f'f{i}', 8) for i in range(16)]
shuffle = bytes.fromhex('02060701050B090E030F04080A0C0D00')
add32 = bytes.fromhex('EFBEADDEADDEE1FE3713371366746367')
xor = bytes.fromhex('7658B4498D1A5F38D423F834EB86F9AA')
expected_prefix = b'CTF{}'[:-1]
for f, v in zip(flag, expected_prefix):
s.add(f == v)
dest = [flag[b] for b in shuffle]
words = []
for i in range(0, len(dest), 4):
words.append(Concat(dest[i + 3], dest[i + 2], dest[i + 1], dest[i]))
for i in range(len(words)):
words[i] += struct.unpack('<I', add32[i * 4:][:4])[0]
for i in range(len(words)):
j = i * 4
dest[j + 0] = Extract(7, 0, words[i])
dest[j + 1] = Extract(15, 8, words[i])
dest[j + 2] = Extract(23, 16, words[i])
dest[j + 3] = Extract(31, 24, words[i])
for i in range(len(dest)):
dest[i] ^= xor[i]
for i in range(len(flag)):
from opcodes import BYTE
from rule import Rule
from z3 import BitVec, BitVecVal, Concat, Extract
"""
Checks that the byte opcode (implemented using shift) is equivalent to a
canonical definition of byte using extract.
"""
rule = Rule()
n_bits = 256
x = BitVec('X', n_bits)
for i in range(0, 32):
# For Byte, i = 0 corresponds to most significant bit
# But for extract i = 0 corresponds to the least significant bit
lsb = 31 - i
rule.check(
BYTE(BitVecVal(i, n_bits), x),
Concat(BitVecVal(0, n_bits - 8), Extract(8 * lsb + 7, 8 * lsb, x)))
def find_n_root_domains_ignoring_wildcards(solver: z3.Solver, symbols: Dict[int, List[str]],
require_literal_dot_in_domain: bool,
levels: int, max_finds: int):
"""If enough root domains are found, report vulnerability.
:param levels: number of levels of domains to consider as part of the root domain. Either 2 or 3.
If 3, the TLD needs to be a Country Code.
:param max_finds: threshold number of root domains to find before considering as vulnerability.
:return: tuple of sat result, witness or debug info
"""
from z3 import Not, And, Or, Xor, Contains, String, StringVal, Length, Implies, SuffixOf, Concat
tld = String('tld')
sld = String('sld')
third_ld = String('3ld')
DNS_root = String('DNS_root')
dot_in_domain = Contains(root_domain, '.')
domain_expr = z3.simplify(And(
Or(DNS_root == StringVal('.'), DNS_root == StringVal('')),
Xor(Concat(root_domain, DNS_root) == fqdn,
And(SuffixOf(Concat(StringVal('.'), root_domain, DNS_root), fqdn),
dot_in_domain)),
Implies(dot_in_domain,
And(Not(Contains(tld, '.')),
Not(Contains(sld, '.')),
Length(tld) > 0,
root_domain == (Concat(sld, StringVal('.'), tld)
if levels < 3
else Concat(third_ld, StringVal('.'), sld, StringVal('.'), tld)))),
Implies(Not(dot_in_domain), And(Concat(root_domain, DNS_root) == fqdn,
tld == StringVal(''),
sld == StringVal(''),)),
))
with solver_frame(solver):
solver.add(domain_expr)
solver.add(RegexStringExpr.ignore_wildcards)
if require_literal_dot_in_domain or levels >= 3:
solver.add(dot_in_domain)
if levels >= 3:
solver.add(z3.simplify(And(
Not(Contains(third_ld, '.')),
Length(sld) > 0,
Length(third_ld) > 0,
Or(*(tld == StringVal(ss) for ss in cc_tlds)),
)))
results = []
found = set()
found_root_domains = set()
result = z3.sat
logger.info('searching for n root_domains')
_concs = lambda zs: concretizations(z3_str_to_bytes(zs), symbols)
solution = None
while len(found_root_domains) < max_finds and result == z3.sat:
result = solver.check()
results.append(result)
if result == z3.sat:
model = solver.model()
_root_domain = model[root_domain]
parts = (model[proto], model[proto_delimiter], model[fqdn])
assert all(part is not None for part in parts)
logger.info(public_vars(model))
found.update(_concs(z3.simplify(z3.Concat(*parts))))
found_root_domains.update(_concs(_root_domain))
solver.add(root_domain != _root_domain)
solution = tz.first(_concs(model[unknown_string]))
# if not sat, return the would-be witness for debugging
if result == z3.sat:
root_domains_label = 'witness'
else:
root_domains_label = 'root_domains'
return result, {'strategy': 'find_n_root_domains_ignoring_wildcards',
'found': list(found),
root_domains_label: list(found_root_domains),
'levels': levels,
'solution': solution}
def to_smt(r):
# type: (Rtl) -> Tuple[List[ExprRef], Z3VarMap]
"""
Encode a concrete primitive Rtl r sa z3 query.
Returns a tuple (query, var_m) where:
- query is a list of z3 expressions
- var_m is a map from Vars v with non-BVType to their correspodning z3
bitvector variable.
"""
assert r.is_concrete()
# Should contain only primitives
primitives = set(PRIMITIVES.instructions)
assert set(d.expr.inst for d in r.rtl).issubset(primitives)
q = [] # type: List[ExprRef]
m = {} # type: Z3VarMap
# Build declarations for any bitvector Vars
var_to_bv = {} # type: Z3VarMap
for v in r.vars():
typ = v.get_typevar().singleton_type()
if not isinstance(typ, BVType):
continue
var_to_bv[v] = BitVec(v.name, typ.bits)
# Encode each instruction as a equality assertion
for d in r.rtl:
inst = d.expr.inst
exp = None # type: ExprRef
# For prim_to_bv/prim_from_bv just update var_m. No assertion needed
if inst == prim_to_bv:
assert isinstance(d.expr.args[0], Var)
m[d.expr.args[0]] = var_to_bv[d.defs[0]]
continue
if inst == prim_from_bv:
assert isinstance(d.expr.args[0], Var)
m[d.defs[0]] = var_to_bv[d.expr.args[0]]
continue
if inst in [bvadd, bvult]: # Binary instructions
assert len(d.expr.args) == 2 and len(d.defs) == 1
lhs = d.expr.args[0]
rhs = d.expr.args[1]
df = d.defs[0]
assert isinstance(lhs, Var) and isinstance(rhs, Var)
if inst == bvadd: # Normal binary - output type same as args
exp = (var_to_bv[lhs] + var_to_bv[rhs])
else:
assert inst == bvult
exp = (var_to_bv[lhs] < var_to_bv[rhs])
# Comparison binary - need to convert bool to BitVec 1
exp = If(exp, BitVecVal(1, 1), BitVecVal(0, 1))
exp = mk_eq(var_to_bv[df], exp)
elif inst == bvzeroext:
arg = d.expr.args[0]
df = d.defs[0]
assert isinstance(arg, Var)
fromW = arg.get_typevar().singleton_type().width()
toW = df.get_typevar().singleton_type().width()
exp = mk_eq(var_to_bv[df], ZeroExt(toW - fromW, var_to_bv[arg]))
elif inst == bvsignext:
arg = d.expr.args[0]
df = d.defs[0]
assert isinstance(arg, Var)
fromW = arg.get_typevar().singleton_type().width()
toW = df.get_typevar().singleton_type().width()
exp = mk_eq(var_to_bv[df], SignExt(toW - fromW, var_to_bv[arg]))
elif inst == bvsplit:
arg = d.expr.args[0]
assert isinstance(arg, Var)
arg_typ = arg.get_typevar().singleton_type()
width = arg_typ.width()
assert (width % 2 == 0)
lo = d.defs[0]
hi = d.defs[1]
exp = And(
mk_eq(var_to_bv[lo], Extract(width // 2 - 1, 0,
var_to_bv[arg])),
mk_eq(var_to_bv[hi],
Extract(width - 1, width // 2, var_to_bv[arg])))
elif inst == bvconcat:
assert isinstance(d.expr.args[0], Var) and \
isinstance(d.expr.args[1], Var)
lo = d.expr.args[0]
hi = d.expr.args[1]
df = d.defs[0]
# Z3 Concat expects hi bits first, then lo bits
exp = mk_eq(var_to_bv[df], Concat(var_to_bv[hi], var_to_bv[lo]))
else:
assert False, "Unknown primitive instruction {}".format(inst)
q.append(exp)
return (q, m)
def array_to_bv32(array):
return Concat(Select(array, BitVecVal(3, 32)),
Select(array, BitVecVal(2, 32)),
Select(array, BitVecVal(1, 32)),
Select(array, BitVecVal(0, 32)))
def BVUnsignedUpCast(x, n_bits): assert x.size() <= n_bits if x.size() < n_bits: return Concat(BitVecVal(0, n_bits - x.size()), x) else: return x
n_bits = 256
# Check that YulUtilFunction::cleanupFunction cleanup matches BVSignedCleanupFunction
for type_bits in range(8, 256, 8):
rule = Rule()
# Input vars
X = BitVec('X', n_bits)
arg = BitVecVal(type_bits / 8 - 1, n_bits)
cleaned_reference = BVSignedCleanupFunction(X, type_bits)
cleaned = SIGNEXTEND(arg, X)
rule.check(cleaned, cleaned_reference)
# Check that BVSignedCleanupFunction properly cleans up values.
for type_bits in range(8, 256, 8):
rule = Rule()
# Input vars
X_short = BitVec('X', type_bits)
dirt = BitVec('dirt', n_bits - type_bits)
X = BVSignedUpCast(X_short, n_bits)
X_dirty = Concat(dirt, X_short)
X_cleaned = BVSignedCleanupFunction(X_dirty, type_bits)
rule.check(X, X_cleaned)