mirror of
https://github.com/theupdateframework/python-tuf
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296 lines
12 KiB
Python
Executable file
296 lines
12 KiB
Python
Executable file
#!/usr/bin/env python
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"""
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<Program Name>
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test_slow_retrieval_attack.py
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<Author>
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Konstantin Andrianov.
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<Started>
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March 13, 2012.
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April 5, 2014.
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Refactored to use the 'unittest' module (test conditions in code, rather
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than verifying text output), use pre-generated repository files, and
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discontinue use of the old repository tools. Expanded comments and modified
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previous setup. -vladimir.v.diaz
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<Copyright>
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See LICENSE for licensing information.
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<Purpose>
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Simulate a slow retrieval attack, where an attacker is able to prevent clients
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from receiving updates by responding to client requests so slowly that updates
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never complete. Test cases included for two types of slow retrievals: data
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that slowly trickles in, and data that is only returned after a long time
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delay. TUF prevents slow retrieval attacks by ensuring the download rate
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does not fall below a required rate (tuf.conf.MIN_AVERAGE_DOWNLOAD_SPEED).
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Note: There is no difference between 'updates' and 'target' files.
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"""
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# Help with Python 3 compatibility, where the print statement is a function, an
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# implicit relative import is invalid, and the '/' operator performs true
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# division. Example: print 'hello world' raises a 'SyntaxError' exception.
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from __future__ import print_function
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from __future__ import absolute_import
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from __future__ import division
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from __future__ import unicode_literals
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import os
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import sys
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import tempfile
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import random
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import time
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import shutil
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import json
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import subprocess
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import logging
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import sys
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# 'unittest2' required for testing under Python < 2.7.
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if sys.version_info >= (2, 7):
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import unittest
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else:
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import unittest2 as unittest
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import tuf.formats
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import tuf.util
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import tuf.log
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import tuf.client.updater as updater
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import tuf.unittest_toolbox as unittest_toolbox
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import tuf.repository_tool as repo_tool
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import tuf.roledb
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import tuf.keydb
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import six
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logger = logging.getLogger('tuf.test_slow_retrieval_attack')
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repo_tool.disable_console_log_messages()
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class TestSlowRetrievalAttack(unittest_toolbox.Modified_TestCase):
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@classmethod
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def setUpClass(cls):
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# setUpClass() is called before any of the test cases are executed.
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# Create a temporary directory to store the repository, metadata, and target
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# files. 'temporary_directory' must be deleted in TearDownModule() so that
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# temporary files are always removed, even when exceptions occur.
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cls.temporary_directory = tempfile.mkdtemp(dir=os.getcwd())
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cls.SERVER_PORT = random.randint(30000, 45000)
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@classmethod
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def tearDownClass(cls):
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# tearDownModule() is called after all the test cases have run.
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# http://docs.python.org/2/library/unittest.html#class-and-module-fixtures
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# Remove the temporary repository directory, which should contain all the
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# metadata, targets, and key files generated of all the test cases.
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shutil.rmtree(cls.temporary_directory)
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def _start_slow_server(self, mode):
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# Launch a SimpleHTTPServer (serves files in the current directory).
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# Test cases will request metadata and target files that have been
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# pre-generated in 'tuf/tests/repository_data', which will be served by the
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# SimpleHTTPServer launched here. The test cases of this unit test assume
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# the pre-generated metadata files have a specific structure, such
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# as a delegated role 'targets/role1', three target files, five key files,
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# etc.
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command = ['python', 'slow_retrieval_server.py', str(self.SERVER_PORT), mode]
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server_process = subprocess.Popen(command, stderr=subprocess.PIPE)
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logger.info('Slow Retrieval Server process started.')
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logger.info('Server process id: '+str(server_process.pid))
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logger.info('Serving on port: '+str(self.SERVER_PORT))
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url = 'http://localhost:'+str(self.SERVER_PORT) + os.path.sep
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# NOTE: Following error is raised if a delay is not applied:
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# <urlopen error [Errno 111] Connection refused>
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time.sleep(1)
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return server_process
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def _stop_slow_server(self, server_process):
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# Kill the SimpleHTTPServer process.
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if server_process.returncode is None:
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logger.info('Server process '+str(server_process.pid)+' terminated.')
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server_process.kill()
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def setUp(self):
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# We are inheriting from custom class.
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unittest_toolbox.Modified_TestCase.setUp(self)
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# Copy the original repository files provided in the test folder so that
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# any modifications made to repository files are restricted to the copies.
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# The 'repository_data' directory is expected to exist in 'tuf/tests/'.
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original_repository_files = os.path.join(os.getcwd(), 'repository_data')
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temporary_repository_root = \
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self.make_temp_directory(directory=self.temporary_directory)
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# The original repository, keystore, and client directories will be copied
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# for each test case.
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original_repository = os.path.join(original_repository_files, 'repository')
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original_client = os.path.join(original_repository_files, 'client')
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original_keystore = os.path.join(original_repository_files, 'keystore')
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# Save references to the often-needed client repository directories.
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# Test cases need these references to access metadata and target files.
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self.repository_directory = \
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os.path.join(temporary_repository_root, 'repository')
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self.client_directory = os.path.join(temporary_repository_root, 'client')
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self.keystore_directory = os.path.join(temporary_repository_root, 'keystore')
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# Copy the original 'repository', 'client', and 'keystore' directories
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# to the temporary repository the test cases can use.
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shutil.copytree(original_repository, self.repository_directory)
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shutil.copytree(original_client, self.client_directory)
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shutil.copytree(original_keystore, self.keystore_directory)
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# The slow retrieval server, in mode 2 (1 byte per second), will only
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# sleep for a total of (target file size) seconds. Add a target file
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# that contains sufficient number of bytes to trigger a slow retrieval
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# error. "sufficient number of bytes" assumed to be
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# >> 'tuf.conf.SLOW_START_GRACE_PERIOD' bytes.
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extra_bytes = 8
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total_bytes = tuf.conf.SLOW_START_GRACE_PERIOD + extra_bytes
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repository = repo_tool.load_repository(self.repository_directory)
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file1_filepath = os.path.join(self.repository_directory, 'targets',
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'file1.txt')
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with open(file1_filepath, 'wb') as file_object:
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data = 'a' * total_bytes
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file_object.write(data.encode('utf-8'))
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key_file = os.path.join(self.keystore_directory, 'timestamp_key')
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timestamp_private = repo_tool.import_ed25519_privatekey_from_file(key_file,
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'password')
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key_file = os.path.join(self.keystore_directory, 'snapshot_key')
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snapshot_private = repo_tool.import_ed25519_privatekey_from_file(key_file,
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'password')
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key_file = os.path.join(self.keystore_directory, 'targets_key')
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targets_private = repo_tool.import_ed25519_privatekey_from_file(key_file,
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'password')
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repository.targets.load_signing_key(targets_private)
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repository.snapshot.load_signing_key(snapshot_private)
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repository.timestamp.load_signing_key(timestamp_private)
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repository.write()
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# Move the staged metadata to the "live" metadata.
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shutil.rmtree(os.path.join(self.repository_directory, 'metadata'))
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shutil.copytree(os.path.join(self.repository_directory, 'metadata.staged'),
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os.path.join(self.repository_directory, 'metadata'))
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# Set the url prefix required by the 'tuf/client/updater.py' updater.
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# 'path/to/tmp/repository' -> 'localhost:8001/tmp/repository'.
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repository_basepath = self.repository_directory[len(os.getcwd()):]
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url_prefix = \
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'http://localhost:' + str(self.SERVER_PORT) + repository_basepath
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# Setting 'tuf.conf.repository_directory' with the temporary client
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# directory copied from the original repository files.
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tuf.conf.repository_directory = self.client_directory
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self.repository_mirrors = {'mirror1': {'url_prefix': url_prefix,
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'metadata_path': 'metadata',
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'targets_path': 'targets',
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'confined_target_dirs': ['']}}
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# Create the repository instance. The test cases will use this client
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# updater to refresh metadata, fetch target files, etc.
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self.repository_updater = updater.Updater('test_repository',
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self.repository_mirrors)
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def tearDown(self):
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# Modified_TestCase.tearDown() automatically deletes temporary files and
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# directories that may have been created during each test case.
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unittest_toolbox.Modified_TestCase.tearDown(self)
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tuf.roledb.clear_roledb(clear_all=True)
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tuf.keydb.clear_keydb(clear_all=True)
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def test_with_tuf_mode_1(self):
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# Simulate a slow retrieval attack.
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# 'mode_1': When download begins,the server blocks the download for a long
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# time by doing nothing before it sends the first byte of data.
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server_process = self._start_slow_server('mode_1')
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# Verify that the TUF client detects replayed metadata and refuses to
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# continue the update process.
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client_filepath = os.path.join(self.client_directory, 'file1.txt')
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try:
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file1_target = self.repository_updater.target('file1.txt')
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self.repository_updater.download_target(file1_target, self.client_directory)
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# Verify that the specific 'tuf.SlowRetrievalError' exception is raised by
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# each mirror.
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except tuf.NoWorkingMirrorError as exception:
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for mirror_url, mirror_error in six.iteritems(exception.mirror_errors):
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url_prefix = self.repository_mirrors['mirror1']['url_prefix']
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url_file = os.path.join(url_prefix, 'targets', 'file1.txt')
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# Verify that 'file1.txt' is the culprit.
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self.assertEqual(url_file, mirror_url)
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self.assertTrue(isinstance(mirror_error, tuf.DownloadLengthMismatchError))
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else:
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self.fail('TUF did not prevent a slow retrieval attack.')
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finally:
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self._stop_slow_server(server_process)
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def test_with_tuf_mode_2(self):
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# Simulate a slow retrieval attack.
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# 'mode_2': During the download process, the server blocks the download
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# by sending just several characters every few seconds.
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server_process = self._start_slow_server('mode_2')
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client_filepath = os.path.join(self.client_directory, 'file1.txt')
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original_average_download_speed = tuf.conf.MIN_AVERAGE_DOWNLOAD_SPEED
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tuf.conf.MIN_AVERAGE_DOWNLOAD_SPEED = 1
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try:
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file1_target = self.repository_updater.target('file1.txt')
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self.repository_updater.download_target(file1_target, self.client_directory)
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# Verify that the specific 'tuf.SlowRetrievalError' exception is raised by
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# each mirror. 'file1.txt' should be large enough to trigger a slow
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# retrieval attack, otherwise the expected exception may not be
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# consistently raised.
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except tuf.NoWorkingMirrorError as exception:
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for mirror_url, mirror_error in six.iteritems(exception.mirror_errors):
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url_prefix = self.repository_mirrors['mirror1']['url_prefix']
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url_file = os.path.join(url_prefix, 'targets', 'file1.txt')
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# Verify that 'file1.txt' is the culprit.
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self.assertEqual(url_file, mirror_url)
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self.assertTrue(isinstance(mirror_error, tuf.DownloadLengthMismatchError))
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else:
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# Another possibility is to check for a successfully downloaded
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# 'file1.txt' at this point.
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self.fail('TUF did not prevent a slow retrieval attack.')
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finally:
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self._stop_slow_server(server_process)
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tuf.conf.MIN_AVERAGE_DOWNLOAD_SPEED = original_average_download_speed
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if __name__ == '__main__':
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unittest.main()
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