#!/usr/bin/env python # Copyright 2012 - 2017, New York University and the TUF contributors # SPDX-License-Identifier: MIT OR Apache-2.0 """ test_endless_data_attack.py Konstantin Andrianov. March 13, 2012. April 3, 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. Minor edits to the test cases. -vladimir.v.diaz See LICENSE-MIT OR LICENSE for licensing information. Simulate an endless data attack, where an updater client tries to download a target file modified by an attacker to contain a large amount of data (a TUF client should only download up to the file's expected length). 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 shutil import json import logging import unittest import sys import tuf import tuf.formats import tuf.log import tuf.client.updater as updater import tuf.unittest_toolbox as unittest_toolbox import tuf.roledb from tests import utils import securesystemslib import six logger = logging.getLogger(__name__) class TestEndlessDataAttack(unittest_toolbox.Modified_TestCase): @classmethod def setUpClass(cls): # 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_process_handler = utils.TestServerProcess(log=logger) @classmethod def tearDownClass(cls): # Cleans the resources and flush the logged lines (if any). cls.server_process_handler.clean() # 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) def setUp(self): # We are inheriting from custom class. unittest_toolbox.Modified_TestCase.setUp(self) self.repository_name = 'test_repository1' # 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_process_handler.port) + repository_basepath # Setting 'tuf.settings.repository_directory' with the temporary client # directory copied from the original repository files. tuf.settings.repositories_directory = self.client_directory self.repository_mirrors = {'mirror1': {'url_prefix': url_prefix, 'metadata_path': 'metadata', 'targets_path': 'targets'}} # Create the repository instance. The test cases will use this client # updater to refresh metadata, fetch target files, etc. self.repository_updater = updater.Updater(self.repository_name, 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) tuf.roledb.clear_roledb(clear_all=True) tuf.keydb.clear_keydb(clear_all=True) # Logs stdout and stderr from the sever subprocess. self.server_process_handler.flush_log() def test_without_tuf(self): # Verify that a target file replaced with a larger malicious version (to # simulate an endless data attack) 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 only download target files # up to their expected lengths, as explicitly specified in metadata, or # 'tuf.settings.py' (when retrieving 'timestamp.json' and 'root.json unsafely'.) # 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 verify 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 = securesystemslib.util.get_file_details(target_path) fileinfo = tuf.formats.make_targets_fileinfo(length, hashes) url_prefix = self.repository_mirrors['mirror1']['url_prefix'] url_file = os.path.join(url_prefix, 'targets', 'file1.txt') # On Windows, the URL portion should not contain backslashes. six.moves.urllib.request.urlretrieve(url_file.replace('\\', '/'), client_target_path) self.assertTrue(os.path.exists(client_target_path)) length, hashes = securesystemslib.util.get_file_details(client_target_path) download_fileinfo = tuf.formats.make_targets_fileinfo(length, hashes) self.assertEqual(fileinfo, download_fileinfo) # Test: Download a target file that has been modified by an attacker with # extra data. with open(target_path, 'a') as file_object: file_object.write('append large amount of data' * 100000) large_length, hashes = securesystemslib.util.get_file_details(target_path) malicious_fileinfo = tuf.formats.make_targets_fileinfo(large_length, hashes) # Is the modified file actually larger? self.assertTrue(large_length > length) # On Windows, the URL portion should not contain backslashes. six.moves.urllib.request.urlretrieve(url_file.replace('\\', '/'), client_target_path) length, hashes = securesystemslib.util.get_file_details(client_target_path) download_fileinfo = tuf.formats.make_targets_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, to contain a large amount of extra data, is not downloaded by # the TUF client. First test that the valid target file is successfully # downloaded. file1_fileinfo = self.repository_updater.get_one_valid_targetinfo('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)) # Verify the client's downloaded file matches the repository's. target_path = os.path.join(self.repository_directory, 'targets', 'file1.txt') length, hashes = securesystemslib.util.get_file_details(client_target_path) fileinfo = tuf.formats.make_targets_fileinfo(length, hashes) length, hashes = securesystemslib.util.get_file_details(client_target_path) download_fileinfo = tuf.formats.make_targets_fileinfo(length, hashes) self.assertEqual(fileinfo, download_fileinfo) # Modify 'file1.txt' and confirm that the TUF client only downloads up to # the expected file length. with open(target_path, 'a') as file_object: file_object.write('append large amount of data' * 10000) # Is the modified file actually larger? large_length, hashes = securesystemslib.util.get_file_details(target_path) self.assertTrue(large_length > length) os.remove(client_target_path) self.repository_updater.download_target(file1_fileinfo, destination) # A large amount of data has been appended to the original content. The # extra data appended should be discarded by the client, so the downloaded # file size and hash should not have changed. length, hashes = securesystemslib.util.get_file_details(client_target_path) download_fileinfo = tuf.formats.make_targets_fileinfo(length, hashes) self.assertEqual(fileinfo, download_fileinfo) # Test that the TUF client does not download large metadata files, as well. timestamp_path = os.path.join(self.repository_directory, 'metadata', 'timestamp.json') original_length, hashes = securesystemslib.util.get_file_details(timestamp_path) with open(timestamp_path, 'r+') as file_object: timestamp_content = securesystemslib.util.load_json_file(timestamp_path) large_data = 'LargeTimestamp' * 10000 timestamp_content['signed']['_type'] = large_data json.dump(timestamp_content, file_object, indent=1, sort_keys=True) modified_length, hashes = securesystemslib.util.get_file_details(timestamp_path) self.assertTrue(modified_length > original_length) # Does the TUF client download the upper limit of an unsafely fetched # 'timestamp.json'? 'timestamp.json' must not be greater than # 'tuf.settings.DEFAULT_TIMESTAMP_REQUIRED_LENGTH'. try: self.repository_updater.refresh() except tuf.exceptions.NoWorkingMirrorError as exception: for mirror_url, mirror_error in six.iteritems(exception.mirror_errors): self.assertTrue(isinstance(mirror_error, securesystemslib.exceptions.Error)) else: self.fail('TUF did not prevent an endless data attack.') if __name__ == '__main__': utils.configure_test_logging(sys.argv) unittest.main()