#!/usr/bin/env python """ test_arbitrary_package_attack.py Konstantin Andrianov. February 22, 2012. March 21, 2014. Refactored to use the 'unittest' module (test conditions in code, rather than verifying text output), use pre-generated repository files, and discontinue use of the old repository tools. -vladimir.v.diaz See LICENSE for licensing information. Simulate an arbitrary package attack, where an updater client attempts to download a malicious file. TUF and non-TUF client scenarios are tested. There is no difference between 'updates' and 'target' files. """ # Help with Python 3 compatibility, where the print statement is a function, an # implicit relative import is invalid, and the '/' operator performs true # division. Example: print 'hello world' raises a 'SyntaxError' exception. from __future__ import print_function from __future__ import absolute_import from __future__ import division from __future__ import unicode_literals import os import tempfile import random import time import shutil import json import subprocess import logging import sys # 'unittest2' required for testing under Python < 2.7. if sys.version_info >= (2, 7): import unittest else: import unittest2 as unittest import tuf import tuf.formats import tuf.util import tuf.roledb import tuf.keydb import tuf.log import tuf.client.updater as updater import tuf.unittest_toolbox as unittest_toolbox import six logger = logging.getLogger('tuf.test_arbitrary_package_attack') class TestArbitraryPackageAttack(unittest_toolbox.Modified_TestCase): @classmethod def setUpClass(cls): # setUpClass() is called before any of the test cases are executed. # Create a temporary directory to store the repository, metadata, and target # files. 'temporary_directory' must be deleted in TearDownModule() so that # temporary files are always removed, even when exceptions occur. cls.temporary_directory = tempfile.mkdtemp(dir=os.getcwd()) # Launch a SimpleHTTPServer (serves files in the current directory). # Test cases will request metadata and target files that have been # pre-generated in 'tuf/tests/repository_data', which will be served by the # SimpleHTTPServer launched here. The test cases of this unit test assume # the pre-generated metadata files have a specific structure, such # as a delegated role 'targets/role1', three target files, five key files, # etc. cls.SERVER_PORT = random.randint(30000, 45000) command = ['python', 'simple_server.py', str(cls.SERVER_PORT)] cls.server_process = subprocess.Popen(command, stderr=subprocess.PIPE) logger.info('Server process started.') logger.info('Server process id: '+str(cls.server_process.pid)) logger.info('Serving on port: '+str(cls.SERVER_PORT)) cls.url = 'http://localhost:'+str(cls.SERVER_PORT) + os.path.sep # NOTE: Following error is raised if a delay is not applied: # time.sleep(1) @classmethod def tearDownClass(cls): # tearDownModule() is called after all the test cases have run. # http://docs.python.org/2/library/unittest.html#class-and-module-fixtures # Remove the temporary repository directory, which should contain all the # metadata, targets, and key files generated of all the test cases. shutil.rmtree(cls.temporary_directory) # Kill the SimpleHTTPServer process. if cls.server_process.returncode is None: logger.info('Server process '+str(cls.server_process.pid)+' terminated.') cls.server_process.kill() def setUp(self): # We are inheriting from custom class. unittest_toolbox.Modified_TestCase.setUp(self) # Copy the original repository files provided in the test folder so that # any modifications made to repository files are restricted to the copies. # The 'repository_data' directory is expected to exist in 'tuf/tests/'. original_repository_files = os.path.join(os.getcwd(), 'repository_data') temporary_repository_root = \ self.make_temp_directory(directory=self.temporary_directory) # The original repository, keystore, and client directories will be copied # for each test case. original_repository = os.path.join(original_repository_files, 'repository') original_client = os.path.join(original_repository_files, 'client') # Save references to the often-needed client repository directories. # Test cases need these references to access metadata and target files. self.repository_directory = \ os.path.join(temporary_repository_root, 'repository') self.client_directory = os.path.join(temporary_repository_root, 'client') # Copy the original 'repository', 'client', and 'keystore' directories # to the temporary repository the test cases can use. shutil.copytree(original_repository, self.repository_directory) shutil.copytree(original_client, self.client_directory) # Set the url prefix required by the 'tuf/client/updater.py' updater. # 'path/to/tmp/repository' -> 'localhost:8001/tmp/repository'. repository_basepath = self.repository_directory[len(os.getcwd()):] url_prefix = \ 'http://localhost:' + str(self.SERVER_PORT) + repository_basepath # Setting 'tuf.conf.repository_directory' with the temporary client # directory copied from the original repository files. tuf.conf.repository_directory = self.client_directory self.repository_mirrors = {'mirror1': {'url_prefix': url_prefix, 'metadata_path': 'metadata', 'targets_path': 'targets', 'confined_target_dirs': ['']}} # Create the repository instance. The test cases will use this client # updater to refresh metadata, fetch target files, etc. self.repository_updater = updater.Updater('test_repository', self.repository_mirrors) def tearDown(self): # Modified_TestCase.tearDown() automatically deletes temporary files and # directories that may have been created during each test case. unittest_toolbox.Modified_TestCase.tearDown(self) # updater.Updater() populates the roledb with the name "test_repository" tuf.roledb.clear_roledb(clear_all=True) tuf.keydb.clear_keydb(clear_all=True) def test_without_tuf(self): # Verify that a target file replaced with a malicious version is downloaded # by a non-TUF client (i.e., a non-TUF client that does not verify hashes, # detect mix-and-mix attacks, etc.) A tuf client, on the other hand, should # detect that the downloaded target file is invalid. # Test: Download a valid target file from the repository. # Ensure the target file to be downloaded has not already been downloaded, # and generate its file size and digest. The file size and digest is needed # to check that the malicious file was indeed downloaded. target_path = os.path.join(self.repository_directory, 'targets', 'file1.txt') client_target_path = os.path.join(self.client_directory, 'file1.txt') self.assertFalse(os.path.exists(client_target_path)) length, hashes = tuf.util.get_file_details(target_path) fileinfo = tuf.formats.make_fileinfo(length, hashes) url_prefix = self.repository_mirrors['mirror1']['url_prefix'] url_file = os.path.join(url_prefix, 'targets', 'file1.txt') six.moves.urllib.request.urlretrieve(url_file, client_target_path) self.assertTrue(os.path.exists(client_target_path)) length, hashes = tuf.util.get_file_details(client_target_path) download_fileinfo = tuf.formats.make_fileinfo(length, hashes) self.assertEqual(fileinfo, download_fileinfo) # Test: Download a target file that has been modified by an attacker. with open(target_path, 'wt') as file_object: file_object.write('add malicious content.') length, hashes = tuf.util.get_file_details(target_path) malicious_fileinfo = tuf.formats.make_fileinfo(length, hashes) six.moves.urllib.request.urlretrieve(url_file, client_target_path) length, hashes = tuf.util.get_file_details(client_target_path) download_fileinfo = tuf.formats.make_fileinfo(length, hashes) # Verify 'download_fileinfo' is unequal to the original trusted version. self.assertNotEqual(download_fileinfo, fileinfo) # Verify 'download_fileinfo' is equal to the malicious version. self.assertEqual(download_fileinfo, malicious_fileinfo) def test_with_tuf(self): # Verify that a target file (on the remote repository) modified by an # attacker is not downloaded by the TUF client. # First test that the valid target file is successfully downloaded. file1_fileinfo = self.repository_updater.target('file1.txt') destination = os.path.join(self.client_directory) self.repository_updater.download_target(file1_fileinfo, destination) client_target_path = os.path.join(destination, 'file1.txt') self.assertTrue(os.path.exists(client_target_path)) # Modify 'file1.txt' and confirm that the TUF client rejects it. target_path = os.path.join(self.repository_directory, 'targets', 'file1.txt') with open(target_path, 'wt') as file_object: file_object.write('malicious content, size 33 bytes.') try: self.repository_updater.download_target(file1_fileinfo, destination) except tuf.NoWorkingMirrorError as exception: url_prefix = self.repository_mirrors['mirror1']['url_prefix'] url_file = os.path.join(url_prefix, 'targets', 'file1.txt') # Verify that only one exception is raised for 'url_file'. self.assertTrue(len(exception.mirror_errors), 1) # Verify that the expected 'tuf.DownloadLengthMismatchError' exception # is raised for 'url_file'. self.assertTrue(url_file in exception.mirror_errors) self.assertTrue(isinstance(exception.mirror_errors[url_file], tuf.BadHashError)) else: self.fail('TUF did not prevent an arbitrary package attack.') def test_with_tuf_and_metadata_tampering(self): # Test that a TUF client does not download a malicious target file, and a # 'targets.json' metadata file that has also been modified by the attacker. # The attacker does not attach a valid signature to 'targets.json' # An attacker modifies 'file1.txt'. target_path = os.path.join(self.repository_directory, 'targets', 'file1.txt') with open(target_path, 'wt') as file_object: file_object.write('malicious content, size 33 bytes.') # An attacker also tries to add the malicious target's length and digest # to its metadata file. length, hashes = tuf.util.get_file_details(target_path) metadata_path = \ os.path.join(self.repository_directory, 'metadata', 'targets.json') metadata = tuf.util.load_json_file(metadata_path) metadata['signed']['targets']['/file1.txt']['hashes'] = hashes metadata['signed']['targets']['/file1.txt']['length'] = length tuf.formats.check_signable_object_format(metadata) with open(metadata_path, 'wb') as file_object: json.dumps(metadata, file_object, indent=1, sort_keys=True).encode('utf-8') # Verify that the malicious 'targets.json' is not downloaded. Perform # a refresh of top-level metadata to demonstrate that the malicious # 'targets.json' is not downloaded. try: self.repository_updater.refresh() file1_fileinfo = self.repository_updater.target('file1.txt') destination = os.path.join(self.client_directory) self.repository_updater.download_target(file1_fileinfo, destination) except tuf.NoWorkingMirrorError as exception: url_prefix = self.repository_mirrors['mirror1']['url_prefix'] url_file = os.path.join(url_prefix, 'targets', 'file1.txt') # Verify that an exception raised for only the malicious 'url_file'. self.assertTrue(len(exception.mirror_errors), 1) # Verify that the specific and expected mirror exception is raised. self.assertTrue(url_file in exception.mirror_errors) self.assertTrue(isinstance(exception.mirror_errors[url_file], tuf.BadHashError)) else: self.fail('TUF did not prevent an arbitrary package attack.') if __name__ == '__main__': unittest.main()