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Refactor test_replay_attack.py.

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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.
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vladdd 2014-04-05 15:27:27 -04:00
parent 48bd9f7040
commit ba19cd7b72
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tests/integration/test_replay_attack.py
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@ -5,34 +5,26 @@
test_replay_attack.py
<Author>
Konstantin Andrianov
Konstantin Andrianov.
<Started>
February 22, 2012
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
<Copyright>
See LICENSE for licensing information.
<Purpose>
Simulate a replay attack. A simple client update vs. client update
implementing TUF.
In the replay attack an attacker is able to trick clients into installing
software that is older than that which the client previously knew to be
available.
NOTE: The interposition provided by 'tuf.interposition' is used to intercept
all calls made by urllib/urillib2 to certain hostname specified in
the interposition configuration file. Look up interposition.py for more
information and illustration of a sample contents of the interposition
configuration file. Interposition was meant to make TUF integration with an
existing software updater an easy process. This allows for more flexibility
to the existing software updater. However, if you are planning to solely use
TUF there should be no need for interposition, all necessary calls will be
generated from within TUF.
There is no difference between 'updates' and 'target' files.
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 compatability, where the print statement is a function, an
@ -43,162 +35,296 @@
from __future__ import division
import os
import shutil
import urllib
import tempfile
import random
import time
import shutil
import json
import subprocess
import unittest
import logging
import tuf.interposition
import tuf.tests.util_test_tools as util_test_tools
import tuf.formats
import tuf.util
import tuf.log
import tuf.client.updater as updater
import tuf.repository_tool as repo_tool
import tuf.tests.unittest_toolbox as unittest_toolbox
# 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 TestSetupError(Exception): pass
class ReplayAttackAlert(Exception): pass
class TestReplayAttack(unittest_toolbox.Modified_TestCase):
def _download(url, filename, using_tuf=False):
if using_tuf:
tuf.interposition.urllib_tuf.urlretrieve(url, filename)
@classmethod
def setUpClass(cls):
# setUpClass() is called before any of the test cases are executed.
else:
urllib.urlretrieve(url, filename)
# 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:
# <urlopen error [Errno 111] Connection refused>
time.sleep(.2)
@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)
unittest_toolbox.Modified_TestCase.clear_toolbox()
# 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 test_replay_attack(using_tuf=False):
"""
<Arguments>
using_tuf:
If set to 'False' all directories that start with 'tuf_' are ignored,
indicating that tuf is not implemented.
<Purpose>
Illustrate replay attack vulnerability.
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(), os.pardir,
'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)
ERROR_MSG = '\tReplay Attack was Successful!\n\n'
FIRST_CONTENT = 'Test A'
SECOND_CONTENT = 'Test B'
try:
# Setup.
root_repo, url, server_proc, keyids = \
util_test_tools.init_repo(using_tuf=using_tuf)
reg_repo = os.path.join(root_repo, 'reg_repo')
tuf_repo = os.path.join(root_repo, 'tuf_repo')
tuf_repo_copy = os.path.join(root_repo, 'tuf_repo_copy')
downloads = os.path.join(root_repo, 'downloads')
tuf_targets = os.path.join(tuf_repo, 'targets')
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)
# Add file to 'repo' directory: {root_repo}
filepath = util_test_tools.add_file_to_repository(reg_repo, FIRST_CONTENT)
file_basename = os.path.basename(filepath)
url_to_repo = url+'reg_repo/'+file_basename
downloaded_file = os.path.join(downloads, file_basename)
# Attacker saves the original file into 'evil_dir'.
evil_dir = tempfile.mkdtemp(dir=root_repo)
original_file = os.path.join(evil_dir, file_basename)
shutil.copy(filepath, evil_dir)
if using_tuf:
# Update TUF metadata before attacker modifies anything.
util_test_tools.tuf_refresh_repo(root_repo, keyids)
# Copy the first version of the repository for replay later.
shutil.copytree(tuf_repo, tuf_repo_copy)
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.
# Modify the url. Remember that the interposition will intercept
# urls that have 'localhost:9999' hostname, which was specified in
# the json interposition configuration file. Look for 'hostname'
# in 'util_test_tools.py'. Further, the 'file_basename' is the target
# path relative to 'targets_dir'.
url_to_repo = 'http://localhost:9999/'+file_basename
# End of Setup.
# 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 = '2088-01-01 12:12:00'
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'))
# Client performs initial update.
_download(url=url_to_repo, filename=downloaded_file, using_tuf=using_tuf)
# 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)
# Downloads are stored in the same directory '{root_repo}/downloads/'
# for regular and tuf clients.
downloaded_content = util_test_tools.read_file_content(downloaded_file)
if FIRST_CONTENT != downloaded_content:
raise TestSetupError('[Initial Update] Failed to download the file.')
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')
urllib.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)
# Developer patches the file and updates the repository.
util_test_tools.modify_file_at_repository(filepath, SECOND_CONTENT)
# 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)
urllib.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)
# Updating tuf repository. This will copy files from regular repository
# into tuf repository and refresh the metadata
if using_tuf:
util_test_tools.tuf_refresh_repo(root_repo, keyids)
# Client downloads the patched file.
_download(url=url_to_repo, filename=downloaded_file, using_tuf=using_tuf)
# Content of the downloaded file.
downloaded_content = util_test_tools.read_file_content(downloaded_file)
if SECOND_CONTENT != downloaded_content:
raise TestSetupError('[Update] Failed to update the file.')
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 = '2088-01-01 12:12:00'
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'))
# Attacker tries to be clever, he manages to modifies regular and tuf
# targets directory by replacing a patched file with an old one.
if using_tuf:
# Delete the current TUF repository...
shutil.rmtree(tuf_repo)
# ...and replace it with a previous copy.
shutil.move(tuf_repo_copy, tuf_repo)
else:
# Delete the current file...
util_test_tools.delete_file_at_repository(filepath)
# ...and replace it with a previous copy.
shutil.copy(original_file, reg_repo)
# 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)
# Verify that the TUF client detects replayed metadata and refuses to
# continue the update process.
try:
# Client downloads the file once more.
_download(url=url_to_repo, filename=downloaded_file, using_tuf=using_tuf)
self.repository_updater.refresh()
# Verify that the specific 'tuf.ReplayedMetadataError' is raised by each
# mirror.
except tuf.NoWorkingMirrorError, exception:
replayed_metadata_attack = False
for mirror_url, mirror_error in exception.mirror_errors.iteritems():
if isinstance(mirror_error, tuf.ReplayedMetadataError):
replayed_metadata_attack = True
break
# In case we did not detect what was likely a replayed metadata attack,
# we reraise the exception to indicate that replayed metadata attack
# detection failed.
if not replayed_metadata_attack: raise
else:
# Check whether the attack succeeded by inspecting the content of the
# update. The update should contain 'Test NOT A'.
downloaded_content = util_test_tools.read_file_content(downloaded_file)
# If we ended up downloading replayed content, then we failed.
if FIRST_CONTENT == downloaded_content:
raise ReplayAttackAlert(ERROR_MSG)
finally:
util_test_tools.cleanup(root_repo, server_proc)
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))
try:
test_replay_attack(using_tuf=False)
except ReplayAttackAlert, exception:
print('Download without TUF fell prey to replayed metadata attack.')
try:
test_replay_attack(using_tuf=True)
except ReplayAttackAlert, exception:
print('Download with TUF fell prey to replayed metadata attack!')
except Exception, exception:
print('Download with TUF failed due to: '+str(exception))
else:
print('Download with TUF defended against replayed metadata attack.')
except Exception, exception:
print('Download without TUF failed due to: '+str(exception))
else:
print('Download without TUF did NOT fail due to replayed metadata attack!')
if __name__ == '__main__':
unittest.main()