Merge pull request #402 from DavidKnott/re-entrancy-protection

Add staticcall opcode for constant external function calls

tests/examples/company/test_company.py

@@ -2,8 +2,9 @@
 
 from ethereum.tools import tester as t
 from ethereum import utils
-from viper import compiler
+
 from tests.setup_transaction_tests import assert_tx_failed
+from viper import compiler
 
 @pytest.fixture
 def tester():

tests/parser/features/test_external_contract_calls.py

@@ -75,7 +75,7 @@ def get_array(arg1: address) -> bytes <= 3:
     assert c2.get_array(c.address) == b'dog'
 
 
-def test_external_contract_call__state_change():
+def test_external_contract_call_state_change():
     contract_1 = """
 lucky: public(num)
 
@@ -101,6 +101,37 @@ def set_lucky(arg1: address, arg2: num):
     print('Successfully executed an external contract call state change')
 
 
+def test_constant_external_contract_call_cannot_change_state(assert_tx_failed):
+    contract_1 = """
+lucky: public(num)
+
+def set_lucky(_lucky: num) -> num:
+    self.lucky = _lucky
+    return _lucky
+    """
+
+    lucky_number = 7
+    c = get_contract(contract_1)
+
+    contract_2 = """
+class Foo():
+    def set_lucky(_lucky: num) -> num: pass
+
+@constant
+def set_lucky_expr(arg1: address, arg2: num):
+    Foo(arg1).set_lucky(arg2)
+
+@constant
+def set_lucky_stmt(arg1: address, arg2: num) -> num:
+    return Foo(arg1).set_lucky(arg2)
+    """
+    c2 = get_contract(contract_2)
+
+    assert_tx_failed(lambda: c2.set_lucky_expr(c.address, lucky_number))
+    assert_tx_failed(lambda: c2.set_lucky_stmt(c.address, lucky_number))
+    print('Successfully tested an constant external contract call attempted state change')
+
+
 def test_external_contract_can_be_changed_based_on_address():
     contract_1 = """
 lucky: public(num)

viper/opcodes.py

@@ -68,6 +68,7 @@
     'INVALID': [0xfe, 0, 0, 0],
     'SUICIDE': [0xff, 1, 0, 5000],
     'SELFDESTRUCT': [0xff, 1, 0, 25000],
+    'STATICCALL': [0xfa, 6, 1, 40],
 }
 
 pseudo_opcodes = {

viper/parser/parser.py

@@ -461,11 +461,13 @@ def external_contract_call_stmt(stmt, context):
     sig = context.sigs[contract_name][method_name]
     contract_address = parse_expr(stmt.func.value.args[0], context)
     inargs, inargsize = pack_arguments(sig, [parse_expr(arg, context) for arg in stmt.args], context)
-    o = LLLnode.from_list(['seq',
-                            ['assert', ['extcodesize', ['mload', contract_address]]],
-                            ['assert', ['ne', 'address', ['mload', contract_address]]],
-                            ['assert', ['call', ['gas'], ['mload', contract_address], 0, inargs, inargsize, 0, 0]]],
-                                    typ=None, location='memory', pos=getpos(stmt))
+    sub = ['seq', ['assert', ['extcodesize', ['mload', contract_address]]],
+                    ['assert', ['ne', 'address', ['mload', contract_address]]]]
+    if context.is_constant:
+        sub.append(['assert', ['staticcall', 'gas', ['mload', contract_address], inargs, inargsize, 0, 0]])
+    else:
+        sub.append(['assert', ['call', 'gas', ['mload', contract_address], 0, inargs, inargsize, 0, 0]])
+    o = LLLnode.from_list(sub, typ=sig.output_type, location='memory', pos=getpos(stmt))
     return o
 
 
@@ -487,13 +489,16 @@ def external_contract_call_expr(expr, context):
         returner = output_placeholder + 32
     else:
         raise TypeMismatchException("Invalid output type: %r" % sig.output_type, expr)
-    o = LLLnode.from_list(['seq',
-                            ['assert', ['extcodesize', ['mload', contract_address]]],
-                            ['assert', ['ne', 'address', ['mload', contract_address]]],
-                            ['assert', ['call', ['gas'], ['mload', contract_address], 0,
-                            inargs, inargsize,
-                            output_placeholder, get_size_of_type(sig.output_type) * 32]],
-                            returner], typ=sig.output_type, location='memory', pos=getpos(expr))
+    sub = ['seq', ['assert', ['extcodesize', ['mload', contract_address]]],
+                    ['assert', ['ne', 'address', ['mload', contract_address]]]]
+    if context.is_constant:
+        sub.append(['assert', ['staticcall', 'gas', ['mload', contract_address], inargs, inargsize,
+                    output_placeholder, get_size_of_type(sig.output_type) * 32]])
+    else:
+        sub.append(['assert', ['call', 'gas', ['mload', contract_address], 0, inargs, inargsize,
+            output_placeholder, get_size_of_type(sig.output_type) * 32]])
+    sub.extend([0, returner])
+    o = LLLnode.from_list(sub, typ=sig.output_type, location='memory', pos=getpos(expr))
     return o