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solver.py
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solver.py
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from pathfinder import PathFinder
from indirectaddressconstraintbuilder import IndirectAddressConstraintBuilder
from expressions import *
from constraints import *
from opcodes import fake_ops, mem_write_ops
from z3 import *
import z3 as z3lib
import sys
class Block():
def __init__(self):
self.timestamp = BitVec('TIMESTAMP', 256)
class Message():
def __init__(self):
self.sender = BitVecVal(0xca11a, 256)
self.value = BitVec('VALUE', 256)
self.gas = BitVecVal(3000000, 256)
class TargetSolver(PathFinder):
def __init__(self, binary):
self.vars = self.__initvars()
PathFinder.__init__(self, binary)
self.solver = Solver()
print("============== Solver ===============")
for func in self.get_all_functions():
self.__iterate_targets(func)
def __initvars(self):
vars = {}
vars['self'] = self
vars['bool_opcodes'] = {
"LT",
"GT",
"SLT",
"SGT",
"EQ",
"ISZERO",
"NONZERO",
"CALL"
} | fake_ops.viewkeys()
vars['equivalent_opcodes'] = {
"ASSERT": ("NONZERO", MonoOpExpression)
}
vars['msg'] = Message()
vars['block'] = Block()
vars['BALANCE'] = BitVec('BALANCE', 256)
vars['AD_MASK'] = BitVecVal(0xffffffffffffffffffffffffffffffffffffffff, 256)
vars['this'] = BitVecVal(0xca11ab1e, 256)
vars['calldatasize'] = BitVec('CALLDATASIZE', 256)
vars['target_value'] = 0xca11a
vars['SHA3'] = Function('SHA3', BitVecSort(512), BitVecSort(256))
return vars
def __iterate_targets(self, func):
for target in self.paths_to_targets[func.signature]:
print("target %s" % target.expression)
target.set_target_value_constraint(self.vars['target_value'])
dominators = target.constraints
self.rewrite_opcodes(dominators)
self.static_single_assignment(dominators)
self.declare_variables(dominators)
self.constraints = list()
self.__convert_expressions(dominators)
for dominator in dominators:
print("dominator %s" % dominator)
self.__indirect_address_constraints = IndirectAddressConstraintBuilder(self.constraints, self.vars)
self.__solve(target)
def __convert_expressions(self, expressions):
for expression in expressions:
constraint = self.__convert_expression(expression)
self.constraints.append(constraint)
def __convert_expression(self, expression):
if isinstance(expression, BinOpExpression):
new_constraint = BinOpConstraint(expression)
elif isinstance(expression, MloadExpression):
new_constraint = MloadConstraint(expression)
elif isinstance(expression, SstoreExpression):
new_constraint = SstoreConstraint(expression)
elif isinstance(expression, MoveExpression):
new_constraint = MoveConstraint(expression)
else:
new_constraint = Constraint(expression)
for i, read in enumerate(expression.reads):
if i in expression.dependencies:
dependency = self.__convert_expression(expression.dependencies[i])
new_constraint.set_dependency(i, dependency)
print "%s %s" % (new_constraint, new_constraint.__class__)
return new_constraint
def rewrite_opcodes(self, expressions):
for i, expression in enumerate(expressions):
opcode = expression.opcode
if expression.opcode in self.vars['equivalent_opcodes']:
expressions[i].__class__ = self.vars['equivalent_opcodes'][opcode][1]
expressions[i].opcode = self.vars['equivalent_opcodes'][opcode][0]
def static_single_assignment(self, expressions):
self.__current_names = dict()
for i, expression in enumerate(expressions):
self.__static_single_assignment(expression, i)
def __static_single_assignment(self, expression, index):
writes = expression.writes
self.__rename_write_registers(expression)
for register in writes:
prefix = register.split("_")[0]
new_name = "%s_%s_%s" % (prefix, index, hex(expression.address))
self.__current_names[prefix] = new_name
print " old name %s new name %s" % (register,new_name)
self.__rename_read_registers(expression)
# unroll MLOAD, CALLDATALOAD or Bool opcodes
for i, read in enumerate(expression.reads):
if i in expression.dependencies:
dependency = expression.dependencies[i]
if expression.contains_operations({"MLOAD", "CALLDATALOAD"})\
or expression.contains_operations(self.vars['bool_opcodes']):
self.__static_single_assignment(dependency, index)
if len(dependency.writes) > 0:
expression.reads[i] = dependency.writes[0]
def __rename_write_registers(self, expression):
writes = expression.writes
for index, write in enumerate(writes):
if write in self.__current_names:
writes[index] = self.__current_names[write]
def __rename_read_registers(self, expression):
reads = expression.reads
for index, register in enumerate(reads):
if index in expression.dependencies:
if not expression.contains_operations({"MLOAD", "CALLDATALOAD"})\
and not expression.contains_operations(self.vars['bool_opcodes']):
self.__rename_read_registers(expression.dependencies[index])
else:
if register in self.__current_names:
reads[index] = self.__current_names[register]
# if we have an immediate value and the operation involves Bool
if not isinstance(register, str) and self.__has_bool_arguments(expression.reads):
# immediate values are converted to True or False
reads[index] = (register != 0)
def __has_bool_arguments(self, reads):
ret = False
for read in reads:
ret |= isinstance(read, BoolRef)
return ret
def declare_variables(self, expressions):
self.__types = dict()
for expression in reversed(expressions):
self.__declare_variables(expression)
for expression in expressions:
self.__convert_read_bool(expression)
for key in self.__types:
keytype = self.__types[key]
if keytype == "Bool":
self.vars[key] = eval("Bool('%s')" % key, z3lib.__dict__)
elif keytype == "BitVec":
self.vars[key] = eval("BitVec('%s', 256)" % key, z3lib.__dict__)
#elif keytype == "BitVecVal":
# self.vars[key] = eval("BitVecVal(%s, 256)" % key)
def __declare_variables(self, expression):
self.__declare_read_variables(expression)
self.__declare_write_variables(expression)
for i, read in enumerate(expression.reads):
if i in expression.dependencies:
dependency = expression.dependencies[i]
if expression.contains_operations({"MLOAD", "CALLDATALOAD", "SLOAD", "SHA3"})\
or expression.contains_operations(self.vars['bool_opcodes']):
self.__declare_variables(dependency)
def __declare_read_variables(self, expression):
for index, register in enumerate(expression.reads):
if index not in expression.dependencies:
print "Trying to declare %s in expression %s" % (register, expression)
if isinstance(register, str):
self.__declare_variable(expression.format_dependency(index))
#else:
# self.__declare_constant(register)
def __declare_write_variables(self, expression):
for write in expression.writes:
if self.is_bool_opcode(expression):
self.__declare_bool(write)
return
print "expression %s is not bool" % expression
if expression.opcode == "MOVE" and isinstance(expression.reads[0], str):
self.__declare_same(write, expression.format_dependency(0))
elif isinstance(write, str):
self.__declare_variable(write)
def __convert_read_bool(self, expression):
for i, register in enumerate(expression.reads):
if i not in expression.dependencies:
if expression.opcode not in self.vars['bool_opcodes'] and isinstance(register, str):
if len(expression.writes) != 0:
self.__declare_same(expression.format_dependency(i), expression.writes[0], True)
else:
dependency = expression.dependencies[i]
if expression.contains_operations({"MLOAD", "CALLDATALOAD"})\
or expression.contains_operations(self.vars['bool_opcodes']):
self.__convert_read_bool(expression.dependencies[i])
def is_bool_opcode(self, expression):
return expression.opcode in self.vars['bool_opcodes'] and len(expression.writes) != 0
def __declare_variable(self, name, force = False):
if name not in self.__types or force:
print("Creating %s = BitVec('%s', 256)" % (name, name))
self.__types[name] = "BitVec"
else:
print "Failed to create BitVec('%s', 256) : already existing" % name
def __declare_bool(self, name, force = False):
if name not in self.__types or force:
print("Creating %s = Bool('%s')" % (name, name))
self.__types[name] = "Bool"
else:
print "Failed to create Bool('%s') : already existing" % name
#def __declare_constant(self, value):
# key = hex(value)
# if key not in self.__types:
# print("Creating constant %s" % key)
# self.__types[key] = "BitVecVal"
def __declare_same(self, name, origin, force = False):
if name not in self.__types or force:
if self.__types[origin]== "Bool":
self.__declare_bool(name, force)
else:
self.__declare_variable(name, force)
def __solve(self, target):
self.solver.push()
target.debug_target()
for i in self.__indirect_address_constraints.mem_constraints:
#print "memory constraints %s" % (self.__indirect_address_constraints.mem_constraints[i])
pass
calldata_constraints = self.__indirect_address_constraints.reference_constraints["CALLDATALOAD"]
for i in calldata_constraints:
for c in calldata_constraints[i]:
#print "calldata constraints %s" % (c)
eval("self.solver.add({})".format(c), z3lib.__dict__, self.vars)
for constraint in reversed(self.constraints):
self.__apply_constraints(constraint)
print("\nAssertions:")
for c in self.solver.assertions():
if isinstance(c, BoolRef):
print c
else:
print hex(c.as_long())
print(self.solver.check())
if self.solver.check() == sat:
m = self.solver.model()
self.vars['m'] = m
calldata_args = self.__indirect_address_constraints.reference_args["CALLDATALOAD"]
print "calldata_args %s" % calldata_args
references = dict()
for opcode in self.__indirect_address_constraints.reference_args:
references[opcode] = dict() # TODO: use default value for dict()
for d in m.decls():
if isinstance(m[d], BoolRef):
print "%s = %s" % (d.name(), m[d])
else:
for opcode in self.__indirect_address_constraints.reference_args:
ref_args = self.__indirect_address_constraints.reference_args[opcode]
if d.name() in ref_args:
value = d.name()
# offset = hex(eval("%s" % eval(ref_args[value])))
if "SHA3" in ref_args[d.name()].opcode:
offset = ("%s" % (ref_args[value]))
else:
print "%s" % ref_args[value].format_dependencies(True, True)
print self.vars
print "%s" % self.vars[m["MLOA_0_752_0"]].__class__
offset = hex(eval("%s" % eval(ref_args[value].format_dependencies(False,True), self.vars), z3lib.__dict__, self.vars))
print "add in calldata %s: %s = %s" % (value, "C[%s]" % offset, hex(m[d].as_long()))
references[opcode][offset] = value
elif d.name() not in ["SHA3"]:
print "%s = %s" % (d.name(), hex(m[d].as_long()))
for opcode in references:
print "%s values" % opcode
for offset in references[opcode]:
var = eval(references[opcode][offset], z3lib.__dict__, self.vars)
print "%s[%s] = %s" % (opcode[:4], offset, hex(eval("m[var].as_long()")))
self.solver.pop()
print("\n")
for i, c in reversed(list(enumerate(target.constraints))):
print "%s: %s" % (i,c.format_dependencies(True, False, False))
print("\n")
def __apply_constraints(self, expression):
opcode = expression.opcode
memory_constraints = self.__indirect_address_constraints.mem_constraints
storage_constraints = self.__indirect_address_constraints.store_constraints
indirect_constraints = dict(memory_constraints, **storage_constraints)
if expression.contains_operations({"MLOAD", "SLOAD", "SHA3"}):
for i in expression.dependencies:
self.__apply_constraints(expression.dependencies[i])
address = expression.address
if address in indirect_constraints:
for indirect_constraint in indirect_constraints[address] :
print("indirect_constraints self.solver.add(%s)" % indirect_constraint)
eval("self.solver.add(%s)" % indirect_constraint, z3lib.__dict__, self.vars)
elif expression.opcode not in mem_write_ops:
expression_copy = deepcopy(expression)
if 0 in expression_copy.dependencies:
print("%s reads before %s" % (opcode, expression_copy.reads[0]))
print("%s deps before %s" % (opcode, expression_copy.dependencies[0]))
expression_copy.dependencies = dict()
print"%s self.solver.add(%s) class %s" % (opcode, expression, expression.__class__)
eval("self.solver.add(%s)" % expression, z3lib.__dict__, self.vars)
else:
address = expression.address
if address in indirect_constraints:
for indirect_constraint in indirect_constraints[address]:
#print("indirect_constraints self.solver.add(%s)" % indirect_constraint)
eval("self.solver.add(%s)" % indirect_constraint, z3lib.__dict__, self.vars)
elif opcode not in mem_write_ops:
print("normal self.solver.add(%s)" % (expression.__class__))
print("normal self.solver.add(%s)" % (expression))
eval("self.solver.add(%s)" % expression, z3lib.__dict__, self.vars)
if __name__ == "__main__":
input_file = open(sys.argv[1])
line = input_file.readline().strip()
if " " in line:
line = line.split(" ")[1]
input_file.close()
a = TargetSolver(line)