#!/usr/bin/env python """ test_replay_attack.py Konstantin Andrianov. February 22, 2012. April 5, 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. Expanded comments. -vladimir.v.diaz See LICENSE for licensing information. Simulate a replay, or rollback, attack. In a replay attack, a client is tricked into installing software that is older than that which the client previously knew to be available. Note: 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 datetime 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.formats import tuf.util import tuf.log import tuf.client.updater as updater import tuf.repository_tool as repo_tool import tuf.unittest_toolbox as unittest_toolbox import six # The repository tool is imported and logs console messages by default. Disable # console log messages generated by this unit test. repo_tool.disable_console_log_messages() logger = logging.getLogger('tuf.test_replay_attack') class TestReplayAttack(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(.8) @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') original_keystore = os.path.join(original_repository_files, 'keystore') # 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') self.keystore_directory = os.path.join(temporary_repository_root, 'keystore') # 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) shutil.copytree(original_keystore, self.keystore_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) def test_without_tuf(self): # Scenario: # 'timestamp.json' specifies the latest version of the repository files. # A client should only accept the same version number (specified in the # file) of the metadata, or greater. A version number less than the one # currently trusted should be rejected. A non-TUF client may use a # different mechanism for determining versions of metadata, but version # numbers in this integrations because that is what TUF uses. # # Modify the repository's timestamp.json' so that a new version is generated # and accepted by the client, and backup the previous version. The previous # is then returned the next time the client requests an update. A non-TUF # client (without a way to detect older versions of metadata, and thus # updates) is expected to download older metadata and outdated files. # Verify that the older version of timestamp.json' is downloaded by the # non-TUF client. # Backup the current version of 'timestamp'. It will be used as the # outdated version returned to the client. The repository tool removes # obsolete metadadata, so do *not* save the backup version in the # repository's metadata directory. timestamp_path = os.path.join(self.repository_directory, 'metadata', 'timestamp.json') backup_timestamp = os.path.join(self.repository_directory, 'timestamp.json.backup') shutil.copy(timestamp_path, backup_timestamp) # The fileinfo of the previous version is saved to verify that it is indeed # accepted by the non-TUF client. length, hashes = tuf.util.get_file_details(backup_timestamp) previous_fileinfo = tuf.formats.make_fileinfo(length, hashes) # Modify the timestamp file on the remote repository. repository = repo_tool.load_repository(self.repository_directory) key_file = os.path.join(self.keystore_directory, 'timestamp_key') timestamp_private = repo_tool.import_rsa_privatekey_from_file(key_file, 'password') repository.timestamp.load_signing_key(timestamp_private) # Set an arbitrary expiration so that the repository tool generates a new # version. repository.timestamp.expiration = datetime.datetime(2030, 1, 1, 12, 12) repository.write() # Move the staged metadata to the "live" metadata. shutil.rmtree(os.path.join(self.repository_directory, 'metadata')) shutil.copytree(os.path.join(self.repository_directory, 'metadata.staged'), os.path.join(self.repository_directory, 'metadata')) # Save the fileinfo of the new version generated to verify that it is # saved by the client. length, hashes = tuf.util.get_file_details(timestamp_path) new_fileinfo = tuf.formats.make_fileinfo(length, hashes) url_prefix = self.repository_mirrors['mirror1']['url_prefix'] url_file = os.path.join(url_prefix, 'metadata', 'timestamp.json') client_timestamp_path = os.path.join(self.client_directory, 'metadata', 'current', 'timestamp.json') six.moves.urllib.request.urlretrieve(url_file, client_timestamp_path) length, hashes = tuf.util.get_file_details(client_timestamp_path) download_fileinfo = tuf.formats.make_fileinfo(length, hashes) # Verify 'download_fileinfo' is equal to the new version. self.assertEqual(download_fileinfo, new_fileinfo) # Restore the previous version of 'timestamp.json' on the remote repository # and verify that the non-TUF client downloads it (expected, but not ideal). shutil.move(backup_timestamp, timestamp_path) six.moves.urllib.request.urlretrieve(url_file, client_timestamp_path) length, hashes = tuf.util.get_file_details(client_timestamp_path) download_fileinfo = tuf.formats.make_fileinfo(length, hashes) # Verify 'download_fileinfo' is equal to the previous version. self.assertEqual(download_fileinfo, previous_fileinfo) self.assertNotEqual(download_fileinfo, new_fileinfo) def test_with_tuf(self): # The same scenario outlined in test_without_tuf() is followed here, except # with a TUF client (scenario description provided in the opening comment # block of that test case.) The TUF client performs a refresh of top-level # metadata, which also includes 'timestamp.json'. # Backup the current version of 'timestamp'. It will be used as the # outdated version returned to the client. The repository tool removes # obsolete metadadata, so do *not* save the backup version in the # repository's metadata directory. timestamp_path = os.path.join(self.repository_directory, 'metadata', 'timestamp.json') backup_timestamp = os.path.join(self.repository_directory, 'timestamp.json.backup') shutil.copy(timestamp_path, backup_timestamp) # The fileinfo of the previous version is saved to verify that it is indeed # accepted by the non-TUF client. length, hashes = tuf.util.get_file_details(backup_timestamp) previous_fileinfo = tuf.formats.make_fileinfo(length, hashes) # Modify the timestamp file on the remote repository. repository = repo_tool.load_repository(self.repository_directory) key_file = os.path.join(self.keystore_directory, 'timestamp_key') timestamp_private = repo_tool.import_rsa_privatekey_from_file(key_file, 'password') repository.timestamp.load_signing_key(timestamp_private) # Set an arbitrary expiration so that the repository tool generates a new # version. repository.timestamp.expiration = datetime.datetime(2030, 1, 1, 12, 12) repository.write() # Move the staged metadata to the "live" metadata. shutil.rmtree(os.path.join(self.repository_directory, 'metadata')) shutil.copytree(os.path.join(self.repository_directory, 'metadata.staged'), os.path.join(self.repository_directory, 'metadata')) # Save the fileinfo of the new version generated to verify that it is # saved by the client. length, hashes = tuf.util.get_file_details(timestamp_path) new_fileinfo = tuf.formats.make_fileinfo(length, hashes) # Refresh top-level metadata, including 'timestamp.json'. Installation of # new version of 'timestamp.json' is expected. self.repository_updater.refresh() client_timestamp_path = os.path.join(self.client_directory, 'metadata', 'current', 'timestamp.json') length, hashes = tuf.util.get_file_details(client_timestamp_path) download_fileinfo = tuf.formats.make_fileinfo(length, hashes) # Verify 'download_fileinfo' is equal to the new version. self.assertEqual(download_fileinfo, new_fileinfo) # Restore the previous version of 'timestamp.json' on the remote repository # and verify that the non-TUF client downloads it (expected, but not ideal). shutil.move(backup_timestamp, timestamp_path) logger.info('Moving the timestamp.json backup to the current version.') # Verify that the TUF client detects replayed metadata and refuses to # continue the update process. try: self.repository_updater.refresh() # Verify that the specific 'tuf.ReplayedMetadataError' is raised by each # mirror. except tuf.NoWorkingMirrorError as exception: for mirror_url, mirror_error in six.iteritems(exception.mirror_errors): url_prefix = self.repository_mirrors['mirror1']['url_prefix'] url_file = os.path.join(url_prefix, 'metadata', 'timestamp.json') # Verify that 'timestamp.json' is the culprit. self.assertEqual(url_file, mirror_url) self.assertTrue(isinstance(mirror_error, tuf.ReplayedMetadataError)) else: self.fail('TUF did not prevent a replay attack.') if __name__ == '__main__': unittest.main()