def _sym_exec(self, gblState, depth=0, constraints=[]):
environment = gblState.environment
disassembly = environment.code
state = gblState.mstate
depth = depth
start_addr = disassembly.instruction_list[state.pc]['address']
if start_addr == 0:
self.current_func = "fallback"
self.current_func_addr = start_addr
node = Node(environment.active_account.contract_name, start_addr, constraints)
logging.debug("- Entering node " + str(node.uid) + ", index = " + str(state.pc) + ", address = " + str(start_addr) + ", depth = " + str(depth))
if start_addr in disassembly.addr_to_func:
# Enter a new function
function_name = disassembly.addr_to_func[start_addr]
self.current_func = function_name
node.flags |= NodeFlags.FUNC_ENTRY
logging.info("- Entering function " + environment.active_account.contract_name + ":" + function_name)
node.function_name = self.current_func
halt = False
while not halt:
try:
instr = disassembly.instruction_list[state.pc]
except IndexError:
logging.debug("Invalid PC")
return node
# Save state before modifying anything
node.states.append(gblState)
gblState = self.copy_global_state(gblState)
state = gblState.mstate
self.total_states += 1
# Point program counter to next instruction
state.pc += 1
op = instr['opcode']
# logging.debug("[" + environment.active_account.contract_name + "] " + helper.get_trace_line(instr, state))
# slows down execution significantly.
# Stack ops
if op.startswith("PUSH"):
value = BitVecVal(int(instr['argument'][2:], 16), 256)
state.stack.append(value)
elif op.startswith('DUP'):
dpth = int(op[3:])
try:
state.stack.append(state.stack[-dpth])
except:
halt = True
elif op.startswith('SWAP'):
dpth = int(op[4:])
try:
temp = state.stack[-dpth - 1]
state.stack[-dpth - 1] = state.stack[-1]
state.stack[-1] = temp
except IndexError: # Stack underflow
halt = True
elif op == 'POP':
try:
state.stack.pop()
except IndexError: # Stack underflow
halt = True
# Bitwise ops
elif op == 'AND':
try:
op1, op2 = state.stack.pop(), state.stack.pop()
if (type(op1) == BoolRef):
op1 = If(op1, BitVecVal(1, 256), BitVecVal(0, 256))
if (type(op2) == BoolRef):
op2 = If(op2, BitVecVal(1, 256), BitVecVal(0, 256))
state.stack.append(op1 & op2)
except IndexError: # Stack underflow
halt = True
elif op == 'OR':
try:
op1, op2 = state.stack.pop(), state.stack.pop()
if (type(op1) == BoolRef):
op1 = If(op1, BitVecVal(1, 256), BitVecVal(0, 256))
if (type(op2) == BoolRef):
op2 = If(op2, BitVecVal(1, 256), BitVecVal(0, 256))
state.stack.append(op1 | op2)
except IndexError: # Stack underflow
halt = True
elif op == 'XOR':
state.stack.append(state.stack.pop() ^ state.stack.pop())
elif op == 'NOT':
state.stack.append(TT256M1 - state.stack.pop())
elif op == 'BYTE':
s0, s1 = state.stack.pop(), state.stack.pop()
state.stack.append(BitVecVal(0, 256))
# Arithmetics
elif op == 'ADD':
state.stack.append((helper.pop_bitvec(state) + helper.pop_bitvec(state)))
elif op == 'SUB':
state.stack.append((helper.pop_bitvec(state) - helper.pop_bitvec(state)))
elif op == 'MUL':
state.stack.append(helper.pop_bitvec(state) * helper.pop_bitvec(state))
elif op == 'DIV':
state.stack.append(UDiv(helper.pop_bitvec(state), helper.pop_bitvec(state)))
elif op == 'MOD':
s0, s1 = helper.pop_bitvec(state), helper.pop_bitvec(state)
state.stack.append(0 if s1 == 0 else URem(s0, s1))
elif op == 'SDIV':
s0, s1 = helper.pop_bitvec(state), helper.pop_bitvec(state)
state.stack.append(s0 / s1)
elif op == 'SMOD':
s0, s1 = helper.pop_bitvec(state), helper.pop_bitvec(state)
state.stack.append(0 if s1 == 0 else s0 % s1)
elif op == 'ADDMOD':
s0, s1, s2 = helper.pop_bitvec(state), helper.pop_bitvec(state), helper.pop_bitvec(state)
state.stack.append((s0 + s1) % s2 if s2 else 0)
elif op == 'MULMOD':
s0, s1, s2 = helper.pop_bitvec(state), helper.pop_bitvec(state), helper.pop_bitvec(state)
state.stack.append((s0 * s1) % s2 if s2 else 0)
elif op == 'EXP':
# we only implement 2 ** x
base, exponent = helper.pop_bitvec(state), helper.pop_bitvec(state)
if (type(base) != BitVecNumRef) or (type(exponent) != BitVecNumRef):
state.stack.append(BitVec(str(base) + "_EXP_" + str(exponent), 256))
elif (base.as_long() == 2):
if exponent.as_long() == 0:
state.stack.append(BitVecVal(1, 256))
else:
state.stack.append(base << (exponent - 1))
else:
state.stack.append(base)
elif op == 'SIGNEXTEND':
s0, s1 = state.stack.pop(), state.stack.pop()
try:
s0 = helper.get_concrete_int(s0)
s1 = helper.get_concrete_int(s1)
if s0 <= 31:
testbit = s0 * 8 + 7
if s1 & (1 << testbit):
state.stack.append(s1 | (TT256 - (1 << testbit)))
else:
state.stack.append(s1 & ((1 << testbit) - 1))
else:
state.stack.append(s1)
except:
halt = True
continue
# Comparisons
elif op == 'LT':
exp = ULT(helper.pop_bitvec(state), helper.pop_bitvec(state))
state.stack.append(exp)
elif op == 'GT':
exp = UGT(helper.pop_bitvec(state), helper.pop_bitvec(state))
state.stack.append(exp)
elif op == 'SLT':
exp = helper.pop_bitvec(state) < helper.pop_bitvec(state)
state.stack.append(exp)
elif op == 'SGT':
exp = helper.pop_bitvec(state) > helper.pop_bitvec(state)
state.stack.append(exp)
elif op == 'EQ':
op1 = state.stack.pop()
op2 = state.stack.pop()
if(type(op1) == BoolRef):
op1 = If(op1, BitVecVal(1, 256), BitVecVal(0, 256))
if(type(op2) == BoolRef):
op2 = If(op2, BitVecVal(1, 256), BitVecVal(0, 256))
exp = op1 == op2
state.stack.append(exp)
elif op == 'ISZERO':
val = state.stack.pop()
if (type(val) == BoolRef):
exp = val == False
else:
exp = val == 0
state.stack.append(exp)
# Call data
elif op == 'CALLVALUE':
state.stack.append(environment.callvalue)
elif op == 'CALLDATALOAD':
# unpack 32 bytes from calldata into a word and put it on the stack
op0 = state.stack.pop()
try:
offset = helper.get_concrete_int(simplify(op0))
b = environment.calldata[offset]
except AttributeError:
logging.debug("CALLDATALOAD: Unsupported symbolic index")
state.stack.append(BitVec("calldata_" + str(environment.active_account.contract_name) + "_" + str(op0), 256))
continue
except IndexError:
logging.debug("Calldata not set, using symbolic variable instead")
state.stack.append(BitVec("calldata_" + str(environment.active_account.contract_name) + "_" + str(op0), 256))
continue
if type(b) == int:
val = b''
try:
for i in range(offset, offset + 32):
val += environment.calldata[i].to_bytes(1, byteorder='big')
logging.debug("Final value: " + str(int.from_bytes(val, byteorder='big')))
state.stack.append(BitVecVal(int.from_bytes(val, byteorder='big'), 256))
except:
state.stack.append(BitVec("calldata_" + str(environment.active_account.contract_name) + "_" + str(op0), 256))
else:
# symbolic variable
state.stack.append(BitVec("calldata_" + str(environment.active_account.contract_name) + "_" + str(op0), 256))
elif op == 'CALLDATASIZE':
if environment.calldata_type == CalldataType.SYMBOLIC:
state.stack.append(BitVec("calldatasize_" + environment.active_account.contract_name, 256))
else:
state.stack.append(BitVecVal(len(environment.calldata), 256))
elif op == 'CALLDATACOPY':
op0, op1, op2 = state.stack.pop(), state.stack.pop(), state.stack.pop()
try:
mstart = helper.get_concrete_int(op0)
except:
logging.debug("Unsupported symbolic memory offset in CALLDATACOPY")
continue
try:
dstart = helper.get_concrete_int(op1)
except:
logging.debug("Unsupported symbolic calldata offset in CALLDATACOPY")
state.mem_extend(mstart, 1)
state.memory[mstart] = BitVec("calldata_" + str(environment.active_account.contract_name) + "_cpy", 256)
continue
try:
size = helper.get_concrete_int(op2)
except:
logging.debug("Unsupported symbolic size in CALLDATACOPY")
state.mem_extend(mstart, 1)
state.memory[mstart] = BitVec("calldata_" + str(environment.active_account.contract_name) + "_" + str(dstart), 256)
continue
if size > 0:
try:
state.mem_extend(mstart, size)
except:
logging.debug("Memory allocation error: mstart = " + str(mstart) + ", size = " + str(size))
state.mem_extend(mstart, 1)
state.memory[mstart] = BitVec("calldata_" + str(environment.active_account.contract_name) + "_" + str(dstart), 256)
continue
try:
i_data = environment.calldata[dstart]
for i in range(mstart, mstart + size):
state.memory[i] = environment.calldata[i_data]
i_data += 1
except:
logging.debug("Exception copying calldata to memory")
state.memory[mstart] = BitVec("calldata_" + str(environment.active_account.contract_name) + "_" + str(dstart), 256)
elif op == 'STOP':
if len(self.call_stack):
self.pending_returns[self.call_stack[-1]].append(node.uid)
halt = True
continue
# Environment
elif op == 'ADDRESS':
state.stack.append(environment.sender)
elif op == 'BALANCE':
addr = state.stack.pop()
state.stack.append(BitVec("balance_at_" + str(addr), 256))
elif op == 'ORIGIN':
state.stack.append(environment.origin)
elif op == 'CALLER':
state.stack.append(environment.sender)
elif op == 'CODESIZE':
state.stack.append(len(disassembly.instruction_list))
if op == 'SHA3':
op0, op1 = state.stack.pop(), state.stack.pop()
try:
index, length = helper.get_concrete_int(op0), helper.get_concrete_int(op1)
except:
# Can't access symbolic memory offsets
state.stack.append(BitVec("KECCAC_mem_" + str(op0) + ")", 256))
continue
try:
data = b''
for i in range(index, index + length):
data += helper.get_concrete_int(state.memory[i]).to_bytes(1, byteorder='big')
i += 1
except:
svar = str(state.memory[index])
svar = svar.replace(" ", "_")
state.stack.append(BitVec("keccac_" + svar, 256))
continue
keccac = utils.sha3(utils.bytearray_to_bytestr(data))
logging.debug("Computed SHA3 Hash: " + str(binascii.hexlify(keccac)))
state.stack.append(BitVecVal(helper.concrete_int_from_bytes(keccac, 0), 256))
elif op == 'GASPRICE':
state.stack.append(BitVec("gasprice", 256))
elif op == 'CODECOPY':
# Not implemented
start, s1, size = state.stack.pop(), state.stack.pop(), state.stack.pop()
elif op == 'EXTCODESIZE':
addr = state.stack.pop()
state.stack.append(BitVec("extcodesize", 256))
elif op == 'EXTCODECOPY':
# Not implemented
addr = state.stack.pop()
start, s2, size = state.stack.pop(), state.stack.pop(), state.stack.pop()
elif op == 'BLOCKHASH':
blocknumber = state.stack.pop()
state.stack.append(BitVec("blockhash_block_" + str(blocknumber), 256))
elif op == 'COINBASE':
state.stack.append(BitVec("coinbase", 256))
elif op == 'TIMESTAMP':
state.stack.append(BitVec("timestamp", 256))
elif op == 'NUMBER':
state.stack.append(BitVec("block_number", 256))
elif op == 'DIFFICULTY':
state.stack.append(BitVec("block_difficulty", 256))
elif op == 'GASLIMIT':
state.stack.append(BitVec("block_gaslimit", 256))
elif op == 'MLOAD':
op0 = state.stack.pop()
logging.debug("MLOAD[" + str(op0) + "]")
try:
offset = helper.get_concrete_int(op0)
except AttributeError:
logging.debug("Can't MLOAD from symbolic index")
data = BitVec("mem_" + str(op0), 256)
continue
try:
data = helper.concrete_int_from_bytes(state.memory, offset)
except IndexError: # Memory slot not allocated
data = BitVec("mem_" + str(offset), 256)
except TypeError: # Symbolic memory
data = state.memory[offset]
logging.debug("Load from memory[" + str(offset) + "]: " + str(data))
state.stack.append(data)
elif op == 'MSTORE':
op0, value = state.stack.pop(), state.stack.pop()
try:
mstart = helper.get_concrete_int(op0)
except AttributeError:
logging.debug("MSTORE to symbolic index. Not supported")
continue
try:
state.mem_extend(mstart, 32)
except Exception:
logging.debug("Error extending memory, mstart = " + str(mstart) + ", size = 32")
logging.debug("MSTORE to mem[" + str(mstart) + "]: " + str(value))
try:
# Attempt to concretize value
_bytes = helper.concrete_int_to_bytes(value)
i = 0
for b in _bytes:
state.memory[mstart + i] = _bytes[i]
i += 1
except:
try:
state.memory[mstart] = value
except:
logging.debug("Invalid memory access")
continue
elif op == 'MSTORE8':
op0, value = state.stack.pop(), state.stack.pop()
try:
offset = helper.get_concrete_int(op0)
except AttributeError:
logging.debug("MSTORE to symbolic index. Not supported")
continue
state.mem_extend(offset, 1)
state.memory[offset] = value % 256
elif op == 'SLOAD':
index = state.stack.pop()
logging.debug("Storage access at index " + str(index))
try:
index = helper.get_concrete_int(index)
except AttributeError:
index = str(index)
try:
data = gblState.accounts[gblState.environment.sender].storage[index]
except KeyError:
data = BitVec("storage_" + str(index), 256)
gblState.environment.active_account.storage[index] = data
state.stack.append(data)
elif op == 'SSTORE':
index, value = state.stack.pop(), state.stack.pop()
logging.debug("Write to storage[" + str(index) + "] at node " + str(start_addr))
try:
index = helper.get_concrete_int(index)
except AttributeError:
index = str(index)
try:
# Create a fresh copy of the account object before modifying storage
for k in gblState.accounts:
if gblState.accounts[k] == gblState.environment.active_account:
gblState.accounts[k] = copy.deepcopy(gblState.accounts[k])
gblState.environment.active_account = gblState.accounts[k]
break
gblState.environment.active_account.storage[index] = value
except KeyError:
logging.debug("Error writing to storage: Invalid index")
continue
elif op == 'JUMP':
try:
jump_addr = helper.get_concrete_int(state.stack.pop())
except AttributeError:
logging.debug("Invalid jump argument (symbolic address)")
halt = True
continue
except IndexError: # Stack Underflow
halt = True
continue
if (depth < self.max_depth):
i = helper.get_instruction_index(disassembly.instruction_list, jump_addr)
if i is None:
logging.debug("JUMP to invalid address")
halt = True
continue
opcode = disassembly.instruction_list[i]['opcode']
if opcode == "JUMPDEST":
new_gblState = self.copy_global_state(gblState)
new_gblState.mstate.pc = i
new_node = self._sym_exec(new_gblState, depth=depth + 1, constraints=constraints)
self.nodes[new_node.uid] = new_node
self.edges.append(Edge(node.uid, new_node.uid, JumpType.UNCONDITIONAL))
halt = True
continue
else:
logging.debug("Skipping JUMP to invalid destination (not JUMPDEST): " + str(jump_addr))
halt = True
# continue
else:
logging.debug("Max depth reached, skipping JUMP")
halt = True
# continue
elif op == 'JUMPI':
op0, condition = state.stack.pop(), state.stack.pop()
try:
jump_addr = helper.get_concrete_int(op0)
except:
logging.debug("Skipping JUMPI to invalid destination.")
if (depth < self.max_depth):
i = helper.get_instruction_index(disassembly.instruction_list, jump_addr)
if not i:
logging.debug("Invalid jump destination: " + str(jump_addr))
else:
instr = disassembly.instruction_list[i]
if instr['opcode'] != "JUMPDEST":
logging.debug("Invalid jump destination: " + str(jump_addr))
halt = True
continue
elif (type(condition) == BoolRef):
if not is_false(simplify(condition)):
# Create new node for condition == True
new_gblState = self.copy_global_state(gblState)
new_gblState.mstate.pc = i
new_constraints = copy.deepcopy(constraints)
new_constraints.append(condition)
new_node = self._sym_exec(new_gblState, depth=depth + 1, constraints=new_constraints)
self.nodes[new_node.uid] = new_node
self.edges.append(Edge(node.uid, new_node.uid, JumpType.CONDITIONAL, condition))
else:
logging.debug("Pruned unreachable states.")
else:
logging.debug("Invalid condition: " + str(condition) + "(type " + str(type(condition)) + ")")
halt = True
continue
new_gblState = self.copy_global_state(gblState)
if (type(condition) == BoolRef):
negated = Not(condition)
else:
negated = condition == 0
if not is_false(simplify(negated)):
new_constraints = copy.deepcopy(constraints)
new_constraints.append(negated)
new_node = self._sym_exec(new_gblState, depth=depth, constraints=new_constraints)
self.nodes[new_node.uid] = new_node
self.edges.append(Edge(node.uid, new_node.uid, JumpType.CONDITIONAL, negated))
halt = True
# continue
else:
logging.debug("Max depth reached, skipping JUMPI")
elif op == 'PC':
state.stack.append(state.pc - 1)
elif op == 'MSIZE':
state.stack.append(BitVec("msize", 256))
elif op == 'GAS':
state.stack.append(BitVec("gas", 256))
elif op.startswith('LOG'):
dpth = int(op[3:])
state.stack.pop(), state.stack.pop()
[state.stack.pop() for x in range(dpth)]
# Not supported
elif op == 'CREATE':
state.stack.pop(), state.stack.pop(), state.stack.pop()
# Not supported
state.stack.append(0)
elif op in ('CALL', 'CALLCODE', 'DELEGATECALL', 'STATICCALL'):
if op in ('CALL', 'CALLCODE'):
gas, to, value, meminstart, meminsz, memoutstart, memoutsz = \
state.stack.pop(), state.stack.pop(), state.stack.pop(), state.stack.pop(), state.stack.pop(), state.stack.pop(), state.stack.pop()
else:
gas, to, meminstart, meminsz, memoutstart, memoutsz = \
state.stack.pop(), state.stack.pop(), state.stack.pop(), state.stack.pop(), state.stack.pop(), state.stack.pop()
try:
callee_address = hex(helper.get_concrete_int(to))
except AttributeError:
# Not a concrete call address. Call target may be an address in storage.
m = re.search(r'storage_(\d+)', str(simplify(to)))
logging.debug("CALL to: " + str(simplify(to)))
if (m and self.dynamic_loader is not None):
idx = int(m.group(1))
logging.info("Dynamic contract address at storage index " + str(idx))
# attempt to read the contract address from instance storage
try:
callee_address = self.dynamic_loader.read_storage(environment.active_account.address, idx)
except:
logging.debug("Error accessing contract storage.")
ret = BitVec("retval_" + str(instr['address']), 256)
state.stack.append(ret)
continue
# testrpc simply returns the address, geth response is more elaborate.
if not re.match(r"^0x[0-9a-f]{40}$", callee_address):
callee_address = "0x" + callee_address[26:]
else:
ret = BitVec("retval_" + str(instr['address']), 256)
state.stack.append(ret)
continue
if not re.match(r"^0x[0-9a-f]{40}", callee_address):
logging.debug("Invalid address: " + str(callee_address))
ret = BitVec("retval_" + str(instr['address']), 256)
state.stack.append(ret)
continue
if (int(callee_address, 16) < 5):
logging.info("Native contract called: " + callee_address)
# Todo: Implement native contracts
ret = BitVec("retval_" + str(instr['address']), 256)
state.stack.append(ret)
continue
try:
callee_account = self.accounts[callee_address]
except KeyError:
# We have a valid call address, but contract is not in the modules list
logging.info("Module with address " + callee_address + " not loaded.")
if self.dynamic_loader is not None:
logging.info("Attempting to load dependency")
try:
code = self.dynamic_loader.dynld(environment.active_account.address, callee_address)
except Exception as e:
logging.info("Unable to execute dynamic loader.")
if code is None:
logging.info("No code returned, not a contract account?")
ret = BitVec("retval_" + str(instr['address']), 256)
state.stack.append(ret)
continue
# New contract bytecode loaded successfully, create a new contract account
self.accounts[callee_address] = Account(callee_address, code, callee_address)
logging.info("Dependency loaded: " + callee_address)
else:
logging.info("Dynamic loader unavailable. Skipping call")
ret = BitVec("retval_" + str(instr['address']), 256)
state.stack.append(ret)
continue
logging.info("Executing " + op + " to: " + callee_address)
try:
callee_account = self.accounts[callee_address]
except KeyError:
logging.info("Contract " + str(callee_address) + " not loaded.")
logging.info((str(self.accounts)))
ret = BitVec("retval_" + str(instr['address']), 256)
state.stack.append(ret)
continue
try:
# TODO: This only allows for either fully concrete or fully symbolic calldata.
# Improve management of memory and callata to support a mix between both types.
calldata = state.memory[helper.get_concrete_int(meminstart):helper.get_concrete_int(meminstart + meminsz)]
if (len(calldata) < 32):
calldata += [0] * (32 - len(calldata))
calldata_type = CalldataType.CONCRETE
logging.debug("Calldata: " + str(calldata))
except AttributeError:
logging.info("Unsupported symbolic calldata offset")
calldata_type = CalldataType.SYMBOLIC
calldata = []
self.call_stack.append(instr['address'])
self.pending_returns[instr['address']] = []
if (op == 'CALL'):
callee_environment = Environment(callee_account, BitVecVal(int(environment.active_account.address, 16), 256), calldata, environment.gasprice, value, environment.origin, calldata_type=calldata_type)
new_gblState = GlobalState(gblState.accounts, callee_environment, MachineState(gas))
new_node = self._sym_exec(new_gblState, depth=depth + 1, constraints=constraints)
self.nodes[new_node.uid] = new_node
elif (op == 'CALLCODE'):
temp_callvalue = environment.callvalue
temp_caller = environment.caller
temp_calldata = environment.calldata
environment.callvalue = value
environment.caller = environment.address
environment.calldata = calldata
new_gblState = GlobalState(gblState.accounts, environment, MachineState(gas))
new_node = self._sym_exec(new_gblState, depth=depth + 1, constraints=constraints)
self.nodes[new_node.uid] = new_node
environment.callvalue = temp_callvalue
environment.caller = temp_caller
environment.calldata = temp_calldata
elif (op == 'DELEGATECALL'):
temp_code = environment.code
temp_calldata = environment.calldata
environment.code = callee_account.code
environment.calldata = calldata
new_gblState = GlobalState(gblState.accounts, environment, MachineState(gas))
new_node = self._sym_exec(new_gblState, depth=depth + 1, constraints=constraints)
self.nodes[new_node.uid] = new_node
environment.code = temp_code
environment.calldata = temp_calldata
self.edges.append(Edge(node.uid, new_node.uid, JumpType.CALL))
'''
There may be multiple possible returns from the callee contract. Currently, we don't create separate nodes on the CFG
for each of them. Instead, a single "return node" is created and a separate edge is added for each return path.
The return value is always symbolic.
'''
ret = BitVec("retval_" + str(disassembly.instruction_list[state.pc]['address']), 256)
state.stack.append(ret)
return_address = self.call_stack.pop()
new_gblState = self.copy_global_state(gblState)
new_node = self._sym_exec(gblState, depth=depth + 1, constraints=constraints)
new_node.flags |= NodeFlags.CALL_RETURN
self.nodes[new_node.uid] = new_node
for ret_uid in self.pending_returns[return_address]:
self.edges.append(Edge(ret_uid, new_node.uid, JumpType.RETURN))
state.stack.append(BitVec("retval", 256))
halt = True
elif op == 'RETURN':
offset, length = state.stack.pop(), state.stack.pop()
try:
self.last_returned = state.memory[helper.get_concrete_int(offset):helper.get_concrete_int(offset + length)]
except AttributeError:
logging.debug("Return with symbolic length or offset. Not supported")
if len(self.call_stack):
self.pending_returns[self.call_stack[-1]].append(node.uid)
halt = True
elif op == 'SUICIDE':
halt = True
elif op == 'REVERT':
if len(self.call_stack):
self.pending_returns[self.call_stack[-1]].append(node.uid)
halt = True
elif op == 'ASSERT_FAIL' or op == 'INVALID':
if len(self.call_stack):
self.pending_returns[self.call_stack[-1]].append(node.uid)
halt = True
logging.debug("Returning from node " + str(node.uid))
return node
def _sym_exec(self, context, state, depth=0, constraints=[]):
disassembly = context.module['disassembly']
depth = depth
start_addr = disassembly.instruction_list[state.pc]['address']
if start_addr == 0:
self.execution_state['current_func'] = "fallback"
self.execution_state['current_func_addr'] = start_addr
node = Node(context.module['name'], start_addr, constraints)
logging.debug("DEBUG Node(type=" + str(type(node)) + "): " + str(node))
logging.debug("- Entering block " + str(node.uid) + ", index = " +
str(state.pc) + ", address = " + str(start_addr) +
", depth = " + str(depth))
if start_addr in disassembly.addr_to_func:
# Enter a new function
function_name = disassembly.addr_to_func[start_addr]
self.execution_state['current_func'] = function_name
logging.info("- Entering function " + context.module['name'] +
":" + function_name)
node.instruction_list.append({
'opcode':
function_name,
'address':
disassembly.instruction_list[state.pc]['address']
})
state.pc += 1
node.function_name = self.execution_state['current_func']
halt = False
instr = disassembly.instruction_list[state.pc]
while not halt:
try:
instr = disassembly.instruction_list[state.pc]
except IndexError:
logging.debug("Invalid PC")
return node
# Save instruction and state
node.instruction_list.append(instr)
node.states[instr['address']] = state
state = copy.deepcopy(state)
self.total_states += 1
state.pc += 1
op = instr['opcode']
logging.debug("[" + context.module['name'] + "] " +
helper.get_trace_line(instr, state))
# slows down execution significantly.
# stack ops
if op.startswith("PUSH"):
value = BitVecVal(int(instr['argument'][2:], 16), 256)
state.stack.append(value)
elif op.startswith('DUP'):
dpth = int(op[3:])
try:
state.stack.append(state.stack[-dpth])
except:
halt = True
continue
elif op.startswith('SWAP'):
dpth = int(op[4:])
try:
temp = state.stack[-dpth - 1]
except IndexError: # Stack underflow
halt = True
continue
state.stack[-dpth - 1] = state.stack[-1]
state.stack[-1] = temp
elif op == 'POP':
try:
state.stack.pop()
except IndexError: # Stack underflow
halt = True
continue
# Bitwise ops
elif op == 'AND':
try:
state.stack.append(state.stack.pop() & state.stack.pop())
except IndexError: # Stack underflow
halt = True
continue
elif op == 'OR':
try:
op1, op2 = state.stack.pop(), state.stack.pop()
except IndexError: # Stack underflow
halt = True
continue
if (type(op1) == BoolRef):
op1 = If(op1, BitVecVal(1, 256), BitVecVal(0, 256))
if (type(op2) == BoolRef):
op2 = If(op2, BitVecVal(1, 256), BitVecVal(0, 256))
state.stack.append(op1 | op2)
elif op == 'XOR':
state.stack.append(state.stack.pop() ^ state.stack.pop())
elif op == 'NOT':
state.stack.append(TT256M1 - state.stack.pop())
elif op == 'BYTE':
s0, s1 = state.stack.pop(), state.stack.pop()
state.stack.append(BitVecVal(0, 256))
# Arithmetics
elif op == 'ADD':
state.stack.append(
(helper.pop_bitvec(state) + helper.pop_bitvec(state)))
elif op == 'SUB':
state.stack.append(
(helper.pop_bitvec(state) - helper.pop_bitvec(state)))
elif op == 'MUL':
state.stack.append(
helper.pop_bitvec(state) * helper.pop_bitvec(state))
elif op == 'DIV':
s0, s1 = helper.pop_bitvec(state), helper.pop_bitvec(state)
state.stack.append(UDiv(s0, s1))
elif op == 'MOD':
s0, s1 = helper.pop_bitvec(state), helper.pop_bitvec(state)
state.stack.append(0 if s1 == 0 else s0 % s1)
elif op == 'SDIV':
s0, s1 = helper.to_signed(
helper.pop_bitvec(state)), helper.to_signed(
helper.pop_bitvec(state))
state.stack.append(0 if s1 == 0 else (
abs(s0) // abs(s1) * (-1 if s0 * s1 < 0 else 1)) & TT256M1)
elif op == 'SMOD':
s0, s1 = helper.to_signed(
helper.pop_bitvec(state)), helper.to_signed(
helper.pop_bitvec(state))
state.stack.append(0 if s1 == 0 else (abs(s0) % abs(s1) *
(-1 if s0 < 0 else 1))
& TT256M1)
elif op == 'ADDMOD':
s0, s1, s2 = helper.pop_bitvec(state), helper.pop_bitvec(
state), helper.pop_bitvec(state)
state.stack.append((s0 + s1) % s2 if s2 else 0)
elif op == 'MULMOD':
s0, s1, s2 = helper.pop_bitvec(state), helper.pop_bitvec(
state), helper.pop_bitvec(state)
state.stack.append((s0 * s1) % s2 if s2 else 0)
elif op == 'EXP':
# we only implement 2 ** x
base, exponent = state.stack.pop(), state.stack.pop()
if (type(base) != BitVecNumRef):
state.stack.append(
BitVec(str(base) + "_EXP_" + str(exponent), 256))
elif (base.as_long() == 2):
if exponent == 0:
state.stack.append(BitVecVal(1, 256))
else:
state.stack.append(base << (exponent - 1))
else:
state.stack.append(base)
elif op == 'SIGNEXTEND':
s0, s1 = state.stack.pop(), state.stack.pop()
try:
s0 = get_concrete_int(s0)
s1 = get_concrete_int(s1)
except:
halt = True
continue
if s0 <= 31:
testbit = s0 * 8 + 7
if s1 & (1 << testbit):
state.stack.append(s1 | (TT256 - (1 << testbit)))
else:
state.stack.append(s1 & ((1 << testbit) - 1))
else:
state.stack.append(s1)
# Comparisons
elif op == 'LT':
exp = ULT(helper.pop_bitvec(state), helper.pop_bitvec(state))
state.stack.append(exp)
elif op == 'GT':
exp = UGT(helper.pop_bitvec(state), helper.pop_bitvec(state))
state.stack.append(exp)
elif op == 'SLT':
exp = helper.pop_bitvec(state) < helper.pop_bitvec(state)
state.stack.append(exp)
elif op == 'SGT':
exp = helper.pop_bitvec(state) > helper.pop_bitvec(state)
state.stack.append(exp)
elif op == 'EQ':
op1 = state.stack.pop()
op2 = state.stack.pop()
if (type(op1) == BoolRef):
op1 = If(op1, BitVecVal(1, 256), BitVecVal(0, 256))
if (type(op2) == BoolRef):
op2 = If(op2, BitVecVal(1, 256), BitVecVal(0, 256))
exp = op1 == op2
state.stack.append(exp)
elif op == 'ISZERO':
val = state.stack.pop()
if (type(val) == BoolRef):
exp = val == False
else:
exp = val == 0
state.stack.append(exp)
# Call data
elif op == 'CALLVALUE':
state.stack.append(context.callvalue)
elif op == 'CALLDATALOAD':
# unpack 32 bytes from calldata into a word and put it on the stack
op0 = state.stack.pop()
try:
offset = helper.get_concrete_int(simplify(op0))
except AttributeError:
logging.debug("CALLDATALOAD: Unsupported symbolic index")
state.stack.append(
BitVec(
"calldata_" + str(context.module['name']) + "_" +
str(op0), 256))
continue
try:
b = context.calldata[offset]
except IndexError:
logging.debug(
"Calldata not set, using symbolic variable instead")
state.stack.append(
BitVec(
"calldata_" + str(context.module['name']) + "_" +
str(op0), 256))
continue
if type(b) == int:
# 32 byte concrete value
val = b''
try:
for i in range(offset, offset + 32):
val += context.calldata[i].to_bytes(
1, byteorder='big')
state.stack.append(
BitVecVal(int.from_bytes(val, byteorder='big'),
256))
except:
state.stack.append(b)
else:
# symbolic variable
state.stack.append(b)
elif op == 'CALLDATASIZE':
if context.calldata_type == CalldataType.SYMBOLIC:
state.stack.append(
BitVec("calldatasize_" + context.module['name'], 256))
else:
state.stack.append(BitVecVal(len(context.calldata), 256))
elif op == 'CALLDATACOPY':
op0, op1, op2 = state.stack.pop(), state.stack.pop(
), state.stack.pop()
try:
mstart = helper.get_concrete_int(op0)
except:
logging.debug(
"Unsupported symbolic memory offset in CALLDATACOPY")
continue
try:
dstart = helper.get_concrete_int(op1)
except:
logging.debug(
"Unsupported symbolic calldata offset in CALLDATACOPY")
state.mem_extend(mstart, 1)
state.memory[mstart] = BitVec(
"calldata_" + str(context.module['name']) + "_cpy",
256)
continue
try:
size = helper.get_concrete_int(op2)
except:
logging.debug("Unsupported symbolic size in CALLDATACOPY")
state.mem_extend(mstart, 1)
state.memory[mstart] = BitVec(
"calldata_" + str(context.module['name']) + "_" +
str(dstart), 256)
continue
if size > 0:
try:
state.mem_extend(mstart, size)
except:
logging.debug("Memory allocation error: mstart = " +
str(mstart) + ", size = " + str(size))
state.mem_extend(mstart, 1)
state.memory[mstart] = BitVec(
"calldata_" + str(context.module['name']) + "_" +
str(dstart), 256)
continue
try:
i_data = context.calldata[dstart]
for i in range(mstart, mstart + size):
state.memory[i] = context.calldata[i_data]
i_data += 1
except:
logging.debug("Exception copying calldata to memory")
state.memory[mstart] = BitVec(
"calldata_" + str(context.module['name']) + "_" +
str(dstart), 256)
# continue
# Control flow
elif op == 'STOP':
if self.last_call_address is not None:
self.pending_returns[self.last_call_address].append(
node.uid)
halt = True
continue
# Environment
elif op == 'ADDRESS':
state.stack.append(context.address)
elif op == 'BALANCE':
addr = state.stack.pop()
state.stack.append(BitVec("balance_at_" + str(addr), 256))
elif op == 'ORIGIN':
state.stack.append(context.origin)
elif op == 'CALLER':
state.stack.append(context.caller)
elif op == 'CODESIZE':
state.stack.append(len(disassembly.instruction_list))
if op == 'SHA3':
op0, op1 = state.stack.pop(), state.stack.pop()
try:
index, length = helper.get_concrete_int(
op0), helper.get_concrete_int(op1)
except:
# Can't access symbolic memory offsets
state.stack.append(
BitVec("KECCAC_mem_" + str(op0) + ")", 256))
continue
try:
data = b''
for i in range(index, index + length):
data += helper.get_concrete_int(
state.memory[i]).to_bytes(1, byteorder='big')
i += 1
except:
svar = str(state.memory[index])
svar = svar.replace(" ", "_")
state.stack.append(BitVec("keccac_" + svar, 256))
continue
logging.debug("SHA3 Data: " + str(data))
keccac = utils.sha3(utils.bytearray_to_bytestr(data))
logging.debug("SHA3 Hash: " + str(binascii.hexlify(keccac)))
state.stack.append(
BitVecVal(helper.concrete_int_from_bytes(keccac, 0), 256))
elif op == 'GASPRICE':
state.stack.append(BitVecVal(1, 256))
elif op == 'CODECOPY':
# Not implemented
start, s1, size = state.stack.pop(), state.stack.pop(
), state.stack.pop()
elif op == 'EXTCODESIZE':
addr = state.stack.pop()
state.stack.append(BitVec("extcodesize", 256))
elif op == 'EXTCODECOPY':
# Not implemented
addr = state.stack.pop()
start, s2, size = state.stack.pop(), state.stack.pop(
), state.stack.pop()
elif op == 'BLOCKHASH':
blocknumber = state.stack.pop()
state.stack.append(
BitVec("blockhash_block_" + str(blocknumber), 256))
elif op == 'COINBASE':
state.stack.append(BitVec("coinbase", 256))
elif op == 'TIMESTAMP':
state.stack.append(BitVec("timestamp", 256))
elif op == 'NUMBER':
state.stack.append(BitVec("block_number", 256))
elif op == 'DIFFICULTY':
state.stack.append(BitVec("block_difficulty", 256))
elif op == 'GASLIMIT':
state.stack.append(BitVec("block_gaslimit", 256))
elif op == 'MLOAD':
op0 = state.stack.pop()
logging.debug("MLOAD[" + str(op0) + "]")
try:
offset = helper.get_concrete_int(op0)
except AttributeError:
logging.debug("Can't MLOAD from symbolic index")
data = BitVec("mem_" + str(op0), 256)
continue
try:
data = helper.concrete_int_from_bytes(state.memory, offset)
except IndexError: # Memory slot not allocated
data = BitVec("mem_" + str(offset), 256)
except TypeError: # Symbolic memory
data = state.memory[offset]
logging.debug("Load from memory[" + str(offset) + "]: " +
str(data))
state.stack.append(data)
elif op == 'MSTORE':
op0, value = state.stack.pop(), state.stack.pop()
try:
mstart = helper.get_concrete_int(op0)
except AttributeError:
logging.debug("MSTORE to symbolic index. Not supported")
continue
try:
state.mem_extend(mstart, 32)
except Exception:
logging.debug("Error extending memory, mstart = " +
str(mstart) + ", size = 32")
logging.debug("MSTORE to mem[" + str(mstart) + "]: " +
str(value))
try:
# Attempt to concretize value
_bytes = helper.concrete_int_to_bytes(value)
i = 0
for b in _bytes:
state.memory[mstart + i] = _bytes[i]
i += 1
except:
try:
state.memory[mstart] = value
except:
logging.debug("Invalid memory access")
continue
# logging.debug("MEM: " + str(state.memory))
elif op == 'MSTORE8':
# Is this ever used?
op0, value = state.stack.pop(), state.stack.pop()
try:
offset = helper.get_concrete_int(op0)
except AttributeError:
logging.debug("MSTORE to symbolic index. Not supported")
continue
state.mem_extend(offset, 1)
state.memory[offset] = value % 256
elif op == 'SLOAD':
index = state.stack.pop()
logging.debug("Storage access at index " + str(index))
if type(index) == BitVecRef:
# SLOAD from hash offset
# k = sha3.keccak_512()
# k.update(bytes(str(index), 'utf-8'))
# index = k.hexdigest()[:8]
index = str(index)
try:
data = state.storage[index]
except KeyError:
data = BitVec("storage_" + str(index), 256)
state.storage[index] = data
state.stack.append(data)
elif op == 'SSTORE':
index, value = state.stack.pop(), state.stack.pop()
logging.debug("Write to storage[" + str(index) + "] at node " +
str(start_addr))
if type(index) == BitVecRef:
index = str(index)
try:
state.storage[index] = value
except KeyError:
logging.debug("Error writing to storage: Invalid index")
continue
elif op == 'JUMP':
try:
jump_addr = helper.get_concrete_int(state.stack.pop())
except AttributeError:
logging.debug("Invalid jump argument (symbolic address)")
halt = True
continue
except IndexError: # Stack Underflow
halt = True
continue
if (depth < self.max_depth):
i = helper.get_instruction_index(
disassembly.instruction_list, jump_addr)
if i is None:
logging.debug("JUMP to invalid address")
halt = True
continue
opcode = disassembly.instruction_list[i]['opcode']
if opcode == "JUMPDEST":
if (self.can_jump(jump_addr)):
new_state = copy.deepcopy(state)
new_state.pc = i
new_node = self._sym_exec(context,
new_state,
depth=depth + 1,
constraints=constraints)
self.nodes[new_node.uid] = new_node
self.edges.append(
Edge(node.uid, new_node.uid,
JumpType.UNCONDITIONAL))
halt = True
continue
else:
logging.debug("JUMP target limit reached")
halt = True
continue
else:
logging.debug(
"Skipping JUMP to invalid destination (not JUMPDEST): "
+ str(jump_addr))
halt = True
continue
else:
logging.debug("Max depth reached, skipping JUMP")
halt = True
continue
elif op == 'JUMPI':
op0, condition = state.stack.pop(), state.stack.pop()
try:
jump_addr = helper.get_concrete_int(op0)
except:
logging.debug("Skipping JUMPI to invalid destination.")
if (depth < self.max_depth):
i = helper.get_instruction_index(
disassembly.instruction_list, jump_addr)
if not i:
logging.debug("Invalid jump destination: " +
str(jump_addr))
else:
instr = disassembly.instruction_list[i]
# Add new node for condition == True
if instr['opcode'] != "JUMPDEST":
logging.debug("Invalid jump destination: " +
str(jump_addr))
else:
if (type(condition) == bool):
logging.debug("BOOL CONDITION TYPE")
# continue
elif (type(condition) == BoolRef):
if (self.can_jump(jump_addr)):
new_state = copy.deepcopy(state)
new_state.pc = i
new_constraints = copy.deepcopy(
constraints)
new_constraints.append(condition)
new_node = self._sym_exec(
context,
new_state,
depth=depth + 1,
constraints=new_constraints)
self.nodes[new_node.uid] = new_node
self.edges.append(
Edge(node.uid, new_node.uid,
JumpType.CONDITIONAL, condition))
else:
logging.debug(
"JUMP target limit reached (JUMPI)")
else:
logging.debug("Invalid condition: " +
str(condition) + "(type " +
str(type(condition)) + ")")
halt = True
continue
new_state = copy.deepcopy(state)
if (type(condition) == BoolRef):
negated = Not(condition)
else:
negated = condition == 0
new_constraints = copy.deepcopy(constraints)
new_constraints.append(negated)
new_node = self._sym_exec(context,
new_state,
depth=depth,
constraints=new_constraints)
self.nodes[new_node.uid] = new_node
self.edges.append(
Edge(node.uid, new_node.uid, JumpType.CONDITIONAL,
negated))
halt = True
continue
else:
logging.debug("Max depth reached, skipping JUMPI")
elif op == 'PC':
state.stack.append(state.pc - 1)
elif op == 'MSIZE':
state.stack.append(BitVec("msize", 256))
elif op == 'GAS':
state.stack.append(10000000)
elif op.startswith('LOG'):
dpth = int(op[3:])
state.stack.pop(), state.stack.pop()
[state.stack.pop() for x in range(dpth)]
# Not supported
elif op == 'CREATE':
state.stack.pop(), state.stack.pop(), state.stack.pop()
# Not supported
state.stack.append(0)
elif op in ('CALL', 'CALLCODE', 'DELEGATECALL', 'STATICCALL'):
if op in ('CALL', 'CALLCODE'):
gas, to, value, meminstart, meminsz, memoutstart, memoutsz = \
state.stack.pop(), state.stack.pop(), state.stack.pop(), state.stack.pop(), state.stack.pop(), state.stack.pop(), state.stack.pop()
else:
gas, to, meminstart, meminsz, memoutstart, memoutsz = \
state.stack.pop(), state.stack.pop(), state.stack.pop(), state.stack.pop(), state.stack.pop(), state.stack.pop()
try:
callee_address = hex(helper.get_concrete_int(to))
except AttributeError:
# Not a concrete call address. Call target may be an address in storage.
m = re.search(r'storage_(\d+)', str(simplify(to)))
logging.debug("CALL to: " + str(simplify(to)))
if (m and self.dynamic_loader is not None):
idx = int(m.group(1))
logging.info(
"Dynamic contract address at storage index " +
str(idx))
# attempt to read the contract address from instance storage
callee_address = self.dynamic_loader.read_storage(
context.module['address'], idx)
# testrpc simply returns the address, geth response is more elaborate.
if not re.match(r"^0x[0-9a-f]{40}$", callee_address):
callee_address = "0x" + callee_address[26:]
else:
logging.info("Unable to resolve address from storage.")
ret = BitVec(
"retval_" + str(disassembly.instruction_list[
state.pc]['address']), 256)
state.stack.append(ret)
continue
if (int(callee_address, 16) < 5):
logging.info("Native contract called: " + callee_address)
# Todo: Implement native contracts
ret = BitVec(
"retval_" +
str(disassembly.instruction_list[state.pc]['address']),
256)
state.stack.append(ret)
continue
if not re.match(r"^0x[0-9a-f]{40}", callee_address):
logging.debug("Invalid address: " + str(callee_address))
ret = BitVec(
"retval_" +
str(disassembly.instruction_list[state.pc]['address']),
256)
state.stack.append(ret)
continue
try:
module = self.modules[callee_address]
except KeyError:
# We have a valid call address, but contract is not in the modules list
logging.info("Module with address " + callee_address +
" not loaded.")
if self.dynamic_loader is not None:
logging.info("Attempting to load dependency")
module = self.dynamic_loader.dynld(
context.module['address'], callee_address)
if module is None:
logging.info(
"No code returned, not a contract account?")
ret = BitVec(
"retval_" + str(disassembly.instruction_list[
state.pc]['address']), 256)
state.stack.append(ret)
continue
# New contract loaded successfully, add it to the modules list
self.modules[callee_address] = module
self.addr_visited[callee_address] = []
logging.info("Dependency loaded: " + module['address'])
else:
logging.info(
"Dynamic loader unavailable. Skipping call")
ret = BitVec(
"retval_" + str(disassembly.instruction_list[
state.pc]['address']), 256)
state.stack.append(ret)
continue
logging.info("Executing " + op + " to: " + callee_address)
try:
callee_module = self.modules[callee_address]
except KeyError:
logging.info("Contract " + str(callee_address) +
" not loaded.")
logging.info((str(self.modules)))
ret = BitVec(
"retval_" +
str(disassembly.instruction_list[state.pc]['address']),
256)
state.stack.append(ret)
continue
# Attempt to write concrete calldata
try:
calldata = state.memory[helper.get_concrete_int(
meminstart):helper.get_concrete_int(meminstart +
meminsz)]
calldata_type = CalldataType.CONCRETE
logging.debug("calldata: " + str(calldata))
except AttributeError:
logging.info("Unsupported symbolic calldata offset")
calldata_type = CalldataType.SYMBOLIC
calldata = []
self.last_call_address = disassembly.instruction_list[
state.pc]['address']
self.pending_returns[self.last_call_address] = []
callee_context = Context(callee_module,
calldata=calldata,
caller=context.address,
origin=context.origin,
calldata_type=calldata_type)
if (op == 'CALL'):
new_node = self._sym_exec(callee_context,
State(),
depth=depth + 1,
constraints=constraints)
self.nodes[new_node.uid] = new_node
elif (op == 'CALLCODE'):
temp_module = context.module
temp_callvalue = context.callvalue
temp_caller = context.caller
temp_calldata = context.calldata
context.module = callee_module
context.callvalue = value
context.caller = context.address
context.calldata = calldata
new_node = self._sym_exec(context,
State(),
depth=depth + 1,
constraints=constraints)
self.nodes[new_node.uid] = new_node
context.module = temp_module
context.callvalue = temp_callvalue
context.caller = temp_caller
context.calldata = temp_calldata
elif (op == 'DELEGATECALL'):
temp_module = context.module
temp_calldata = context.calldata
context.module = callee_module
context.calldata = calldata
new_node = self._sym_exec(context,
State(),
depth=depth + 1,
constraints=constraints)
self.nodes[new_node.uid] = new_node
context.module = temp_module
context.calldata = temp_calldata
self.edges.append(Edge(node.uid, new_node.uid, JumpType.CALL))
ret = BitVec(
"retval_" +
str(disassembly.instruction_list[state.pc]['address']),
256)
state.stack.append(ret)
new_state = copy.deepcopy(state)
new_node = self._sym_exec(context,
new_state,
depth=depth + 1,
constraints=constraints)
self.nodes[new_node.uid] = new_node
for ret_uid in self.pending_returns[self.last_call_address]:
self.edges.append(
Edge(ret_uid, new_node.uid, JumpType.RETURN))
state.stack.append(BitVec("retval", 256))
continue
elif op == 'RETURN':
offset, length = state.stack.pop(), state.stack.pop()
try:
self.last_returned = state.memory[helper.get_concrete_int(
offset):helper.get_concrete_int(offset + length)]
except AttributeError:
logging.debug(
"Return with symbolic length or offset. Not supported")
if self.last_call_address is not None:
self.pending_returns[self.last_call_address].append(
node.uid)
halt = True
continue
elif op == 'SUICIDE':
halt = True
continue
elif op == 'REVERT':
if self.last_call_address is not None:
self.pending_returns[self.last_call_address].append(
node.uid)
halt = True
continue
elif op == 'INVALID':
halt = True
continue
logging.debug("Returning from node " + str(node.uid))
return node