Set low priority to other internal compiler generated code (#975)

* Set low priority to other internal compiler generated code

* Remove unused variable

* Use the ast to get contract source code

* Add docstrings

* Remove code filtering for truffle

* Update mythril/solidity/soliditycontract.py

Co-Authored-By: JoranHonig <JoranHonig@users.noreply.github.com>

mythril/ethereum/util.py

@@ -33,7 +33,7 @@ def get_solc_json(file, solc_binary="solc", solc_args=None):
     :return:
     """
 
-    cmd = [solc_binary, "--combined-json", "bin,bin-runtime,srcmap,srcmap-runtime"]
+    cmd = [solc_binary, "--combined-json", "bin,bin-runtime,srcmap,srcmap-runtime,ast"]
 
     if solc_args:
         cmd.extend(solc_args.split())

mythril/solidity/soliditycontract.py

@@ -1,5 +1,7 @@
 """This module contains representation classes for Solidity files, contracts
 and source mappings."""
+from typing import Dict, Set
+
 import mythril.laser.ethereum.util as helper
 from mythril.ethereum.evmcontract import EVMContract
 from mythril.ethereum.util import get_solc_json
@@ -20,9 +22,16 @@ class SourceMapping:
 class SolidityFile:
     """Representation of a file containing Solidity code."""
 
-    def __init__(self, filename, data):
+    def __init__(self, filename: str, data: str, full_contract_source: Set[str]):
+        """
+        Metadata class containing data regarding a specific solidity file
+        :param filename: The filename of the solidity file
+        :param data: The code of the solidity file
+        :param full_contract_source: The set of contract source mappings of all the contracts in the file
+        """
         self.filename = filename
         self.data = data
+        self.full_contract_source = full_contract_source
 
 
 class SourceCodeInfo:
@@ -69,7 +78,12 @@ class SolidityContract(EVMContract):
         for filename in data["sourceList"]:
             with open(filename, "r", encoding="utf-8") as file:
                 code = file.read()
-                self.solidity_files.append(SolidityFile(filename, code))
+                full_contract_sources = self.get_full_contract_sources(
+                    data["sources"][filename]["AST"]
+                )
+                self.solidity_files.append(
+                    SolidityFile(filename, code, full_contract_sources)
+                )
 
         has_contract = False
 
@@ -117,6 +131,19 @@ class SolidityContract(EVMContract):
 
         super().__init__(code, creation_code, name=name)
 
+    @staticmethod
+    def get_full_contract_sources(ast: Dict) -> Set[str]:
+        """
+        Takes a solc AST and gets the src mappings for all the contracts defined in the top level of the ast
+        :param ast: AST of the contract
+        :return: The source map
+        """
+        source_map = set()
+        for child in ast["children"]:
+            if "contractKind" in child["attributes"]:
+                source_map.add(child["src"])
+        return source_map
+
     def get_source_info(self, address, constructor=False):
         """
 
@@ -140,6 +167,26 @@ class SolidityContract(EVMContract):
         lineno = mappings[index].lineno
         return SourceCodeInfo(filename, lineno, code, mappings[index].solc_mapping)
 
+    def _is_autogenerated_code(self, offset: int, length: int, file_index: int) -> bool:
+        """
+        Checks whether the code is autogenerated or not
+        :param offset: offset of the code
+        :param length: length of the code
+        :param file_index: file the code corresponds to
+        :return: True if the code is internally generated, else false
+        """
+        # Handle internal compiler files
+        if file_index == -1:
+            return True
+        # Handle the common code src map for the entire code.
+        if (
+            "{}:{}:{}".format(offset, length, file_index)
+            in self.solidity_files[file_index].full_contract_source
+        ):
+            return True
+
+        return False
+
     def _get_solc_mappings(self, srcmap, constructor=False):
         """
 
@@ -161,7 +208,8 @@ class SolidityContract(EVMContract):
 
             if len(mapping) > 2 and len(mapping[2]) > 0:
                 idx = int(mapping[2])
-            if idx == -1:
+
+            if self._is_autogenerated_code(offset, length, idx):
                 lineno = None
             else:
                 lineno = (