Merge pull request #837 from crytic/dev-unchecked-block

 Add checked arithmetic  + unchecked block

Author: montyly

slither/slithir/operations/binary.py

@@ -88,6 +88,16 @@ def get_type(operation_type):  # pylint: disable=too-many-branches
 
         raise SlithIRError("get_type: Unknown operation type {})".format(operation_type))
 
+    def can_be_checked_for_overflow(self):
+        return self in [
+            BinaryType.POWER,
+            BinaryType.MULTIPLICATION,
+            BinaryType.MODULO,
+            BinaryType.ADDITION,
+            BinaryType.SUBTRACTION,
+            BinaryType.DIVISION,
+        ]
+
     def __str__(self):  # pylint: disable=too-many-branches
         if self == BinaryType.POWER:
             return "**"
@@ -167,6 +177,8 @@ def type(self):
 
     @property
     def type_str(self):
+        if self.node.scope.is_checked and self._type.can_be_checked_for_overflow():
+            return "(c)" + str(self._type)
         return str(self._type)
 
     def __str__(self):

slither/solc_parsing/declarations/function.py

@@ -931,6 +931,8 @@ def _parse_statement(
             node = self._parse_for(statement, node)
         elif name == "Block":
             node = self._parse_block(statement, node)
+        elif name == "UncheckedBlock":
+            node = self._parse_unchecked_block(statement, node)
         elif name == "InlineAssembly":
             # Added with solc 0.6 - the yul code is an AST
             if "AST" in statement and not self.compilation_unit.core.skip_assembly:
@@ -1015,7 +1017,7 @@ def _parse_statement(
 
         return node
 
-    def _parse_block(self, block: Dict, node: NodeSolc):
+    def _parse_block(self, block: Dict, node: NodeSolc, check_arithmetic: bool = False):
         """
         Return:
             Node
@@ -1027,7 +1029,25 @@ def _parse_block(self, block: Dict, node: NodeSolc):
         else:
             statements = block[self.get_children("children")]
 
-        new_scope = Scope(node.underlying_node.scope.is_checked, False, node.underlying_node.scope)
+        check_arithmetic = check_arithmetic | node.underlying_node.scope.is_checked
+        new_scope = Scope(check_arithmetic, False, node.underlying_node.scope)
+        for statement in statements:
+            node = self._parse_statement(statement, node, new_scope)
+        return node
+
+    def _parse_unchecked_block(self, block: Dict, node: NodeSolc):
+        """
+        Return:
+            Node
+        """
+        assert block[self.get_key()] == "UncheckedBlock"
+
+        if self.is_compact_ast:
+            statements = block["statements"]
+        else:
+            statements = block[self.get_children("children")]
+
+        new_scope = Scope(False, False, node.underlying_node.scope)
         for statement in statements:
             node = self._parse_statement(statement, node, new_scope)
         return node
@@ -1048,7 +1068,8 @@ def _parse_cfg(self, cfg: Dict):
             self._function.is_empty = True
         else:
             self._function.is_empty = False
-            self._parse_block(cfg, node)
+            check_arithmetic = self.compilation_unit.solc_version >= "0.8.0"
+            self._parse_block(cfg, node, check_arithmetic=check_arithmetic)
             self._remove_incorrect_edges()
             self._remove_alone_endif()