Add support for locking config file (#1652)

* Add support for locking config file

* Remove abi decode test

* Fix typo

mythril/mythril/mythril_config.py

@@ -10,6 +10,7 @@ from typing import Optional
 
 from mythril.exceptions import CriticalError
 from mythril.ethereum.interface.rpc.client import EthJsonRpc
+from mythril.support.lock import LockFile
 
 log = logging.getLogger(__name__)
 
@@ -69,21 +70,23 @@ class MythrilConfig:
         config = ConfigParser(allow_no_value=True)
 
         config.optionxform = str
-        config.read(self.config_path, "utf-8")
-        if "defaults" not in config.sections():
-            self._add_default_options(config)
+        with LockFile(self.config_path):
+            config.read(self.config_path, "utf-8")
+
+            if "defaults" not in config.sections():
+                self._add_default_options(config)
 
-        if not config.has_option("defaults", "dynamic_loading"):
-            self._add_dynamic_loading_option(config)
+            if not config.has_option("defaults", "dynamic_loading"):
+                self._add_dynamic_loading_option(config)
 
-        if not config.has_option("defaults", "infura_id"):
-            config.set("defaults", "infura_id", "")
+            if not config.has_option("defaults", "infura_id"):
+                config.set("defaults", "infura_id", "")
 
-        with codecs.open(self.config_path, "w", "utf-8") as fp:
-            config.write(fp)
+            with codecs.open(self.config_path, "w", "utf-8") as fp:
+                config.write(fp)
 
-        if not self.infura_id:
-            self.infura_id = config.get("defaults", "infura_id", fallback="")
+            if not self.infura_id:
+                self.infura_id = config.get("defaults", "infura_id", fallback="")
 
     @staticmethod
     def _add_default_options(config: ConfigParser) -> None:

mythril/support/lock.py

@@ -0,0 +1,78 @@
+import os
+import time
+import errno
+
+"""
+credits: https://github.com/dmfrey/FileLock
+"""
+
+
+class LockFileException(Exception):
+    pass
+
+
+class LockFile(object):
+    """
+    Locks files.
+    """
+
+    def __init__(self, file_name, timeout=100, delay=0.05):
+        """
+        Initialises the file locker
+        """
+        if timeout is not None and delay is None:
+            raise ValueError("If timeout is not None, then delay must not be None.")
+        self.is_locked = False
+        self.lockfile = os.path.join(os.getcwd(), f"{file_name}.lock")
+        self.file_name = file_name
+        self.timeout = timeout
+        self.delay = delay
+
+    def acquire(self):
+        """
+        Acquires a lock when possible.
+        """
+        start_time = time.time()
+        while True:
+            try:
+                self.fd = os.open(self.lockfile, os.O_CREAT | os.O_EXCL | os.O_RDWR)
+                self.is_locked = True
+                break
+            except OSError as e:
+                if e.errno != errno.EEXIST:
+                    raise
+                if (time.time() - start_time) >= self.timeout:
+                    raise FileLockException(
+                        f"Stuck for more than {self.timeout} seconds waiting to unlock the file {self.filename}."
+                    )
+                time.sleep(self.delay)
+
+    def release(self):
+        """
+        Releases the lock
+        """
+        if self.is_locked:
+            os.close(self.fd)
+            os.unlink(self.lockfile)
+            self.is_locked = False
+
+    def __enter__(self):
+        """
+        Lock gets acquired at the `with` statement.
+        """
+        if not self.is_locked:
+            self.acquire()
+        return self
+
+    def __exit__(self, type, value, traceback):
+        """
+        Lock get's released at the end of the `with` block
+        """
+        if self.is_locked:
+            self.release()
+
+    def __del__(self):
+        """
+        Releases the lock during deletion.
+        """
+        self.release()

tests/integration_tests/parallel_test.py

@@ -0,0 +1,16 @@
+from subprocess import Popen, PIPE
+from tests import PROJECT_DIR, TESTDATA
+import json
+
+MYTH = str(PROJECT_DIR / "myth")
+
+
+def test_parallel():
+
+    test_file = str(TESTDATA / "input_contracts" / "origin.sol")
+    program = f"python3 {MYTH} a {test_file} --solv 0.5.0 -o json"
+    processes = [Popen(program, stdout=PIPE, shell=True) for i in range(30)]
+    for p in processes:
+        out, err = p.communicate()
+        json_output = json.loads(out.decode("utf-8"))
+        assert json_output["success"] == True