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Speedup indefinite freeze tests #1194

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merged 3 commits into from
Nov 2, 2020
Merged

Speedup indefinite freeze tests #1194

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e7ce873
updater: Add missing Exception documentation
Oct 29, 2020
ca048a2
tests: Remove sleeps from indefinite freeze tests
Oct 29, 2020
05cf090
tests: Use version specific import for mock
Oct 30, 2020
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134 changes: 55 additions & 79 deletions tests/test_indefinite_freeze_attack.py
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Original file line number Diff line number Diff line change
Expand Up @@ -44,6 +44,8 @@
from __future__ import division
from __future__ import unicode_literals

import datetime
import unittest.mock as mock
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import os
import time
import tempfile
Expand Down Expand Up @@ -265,8 +267,7 @@ def test_with_tuf(self):
# Load the repository
repository = repo_tool.load_repository(self.repository_directory)

# Load the timestamp and snapshot keys, since we will be signing a new
# timestamp and a new snapshot file.
# Load the snapshot and timestamp keys
key_file = os.path.join(self.keystore_directory, 'timestamp_key')
timestamp_private = repo_tool.import_ed25519_privatekey_from_file(key_file,
'password')
Expand All @@ -276,17 +277,11 @@ def test_with_tuf(self):
'password')
repository.snapshot.load_signing_key(snapshot_private)

# Expire snapshot in 10s. This should be far enough into the future that we
# haven't reached it before the first refresh validates timestamp expiry.
# We want a successful refresh before expiry, then a second refresh after
# expiry (which we then expect to raise an exception due to expired
# metadata).
expiry_time = time.time() + 10
datetime_object = tuf.formats.unix_timestamp_to_datetime(int(expiry_time))

repository.snapshot.expiration = datetime_object

# Now write to the repository.
# sign snapshot with expiry in near future (earlier than e.g. timestamp)
expiry = int(time.time() + 60*60)
repository.snapshot.expiration = tuf.formats.unix_timestamp_to_datetime(
expiry)
repository.mark_dirty(['snapshot', 'timestamp'])
repository.writeall()

# And move the staged metadata to the "live" metadata.
Expand All @@ -297,30 +292,24 @@ def test_with_tuf(self):
# Refresh metadata on the client. For this refresh, all data is not expired.
logger.info('Test: Refreshing #1 - Initial metadata refresh occurring.')
self.repository_updater.refresh()
logger.info('Test: Refreshed #1 - Initial metadata refresh completed '
'successfully. Now sleeping until snapshot metadata expires.')

# Sleep until expiry_time ('repository.snapshot.expiration')
time.sleep(max(0, expiry_time - time.time() + 1))

logger.info('Test: Refreshing #2 - Now trying to refresh again after local'
' snapshot expiry.')

try:
self.repository_updater.refresh() # We expect this to fail!
logger.info('Test: Refreshing #2 - refresh after local snapshot expiry.')

except tuf.exceptions.ExpiredMetadataError:
logger.info('Test: Refresh #2 - failed as expected. Expired local'
' snapshot case generated a tuf.exceptions.ExpiredMetadataError'
' exception as expected. Test pass.')
# mock current time to one second after snapshot expiry
mock_time = mock.Mock()
mock_time.return_value = expiry + 1
with mock.patch('time.time', mock_time):
try:
self.repository_updater.refresh() # We expect this to fail!

# I think that I only expect tuf.ExpiredMetadata error here. A
# NoWorkingMirrorError indicates something else in this case - unavailable
# repo, for example.
else:
except tuf.exceptions.ExpiredMetadataError:
logger.info('Test: Refresh #2 - failed as expected. Expired local'
' snapshot case generated a tuf.exceptions.ExpiredMetadataError'
' exception as expected. Test pass.')

self.fail('TUF failed to detect expired stale snapshot metadata. Freeze'
' attack successful.')
else:
self.fail('TUF failed to detect expired stale snapshot metadata. Freeze'
' attack successful.')



Expand Down Expand Up @@ -355,7 +344,7 @@ def test_with_tuf(self):
# We cannot set the timestamp expiration with
# 'repository.timestamp.expiration = ...' with already-expired timestamp
# metadata because of consistency checks that occur during that assignment.
expiry_time = time.time() + 1
expiry_time = time.time() + 60*60
datetime_object = tuf.formats.unix_timestamp_to_datetime(int(expiry_time))
repository.timestamp.expiration = datetime_object
repository.writeall()
Expand All @@ -365,29 +354,21 @@ def test_with_tuf(self):
shutil.copytree(os.path.join(self.repository_directory, 'metadata.staged'),
os.path.join(self.repository_directory, 'metadata'))

# Wait just long enough for the timestamp metadata (which is now both on
# the repository and on the client) to expire.
time.sleep(max(0, expiry_time - time.time() + 1))
# mock current time to one second after timestamp expiry
mock_time = mock.Mock()
mock_time.return_value = expiry_time + 1
with mock.patch('time.time', mock_time):
try:
self.repository_updater.refresh() # We expect NoWorkingMirrorError.

# Try to refresh top-level metadata on the client. Since we're already past
# 'repository.timestamp.expiration', the TUF client is expected to detect
# that timestamp metadata is outdated and refuse to continue the update
# process.
try:
self.repository_updater.refresh() # We expect NoWorkingMirrorError.
except tuf.exceptions.NoWorkingMirrorError as e:
# Make sure the contained error is ExpiredMetadataError
for mirror_url, mirror_error in six.iteritems(e.mirror_errors):
self.assertTrue(isinstance(mirror_error, tuf.exceptions.ExpiredMetadataError))

except tuf.exceptions.NoWorkingMirrorError as e:
# NoWorkingMirrorError indicates that we did not find valid, unexpired
# metadata at any mirror. That exception class preserves the errors from
# each mirror. We now assert that for each mirror, the particular error
# detected was that metadata was expired (the timestamp we manually
# expired).
for mirror_url, mirror_error in six.iteritems(e.mirror_errors):
self.assertTrue(isinstance(mirror_error, tuf.exceptions.ExpiredMetadataError))

else:
self.fail('TUF failed to detect expired, stale timestamp metadata.'
' Freeze attack successful.')
else:
self.fail('TUF failed to detect expired, stale timestamp metadata.'
' Freeze attack successful.')



Expand Down Expand Up @@ -416,8 +397,8 @@ def test_with_tuf(self):
# Set ts to expire in 1 month.
ts_expiry_time = time.time() + 2630000

# Set snapshot to expire in 1 second.
snapshot_expiry_time = time.time() + 1
# Set snapshot to expire in 1 hour.
snapshot_expiry_time = time.time() + 60*60

ts_datetime_object = tuf.formats.unix_timestamp_to_datetime(
int(ts_expiry_time))
Expand All @@ -432,28 +413,23 @@ def test_with_tuf(self):
shutil.copytree(os.path.join(self.repository_directory, 'metadata.staged'),
os.path.join(self.repository_directory, 'metadata'))

# Wait just long enough for the Snapshot metadata (which is now on the
# repository) to expire.
time.sleep(max(0, snapshot_expiry_time - time.time() + 1))


try:
# We expect the following refresh() to raise a NoWorkingMirrorError.
self.repository_updater.refresh()

except tuf.exceptions.NoWorkingMirrorError as e:
# NoWorkingMirrorError indicates that we did not find valid, unexpired
# metadata at any mirror. That exception class preserves the errors from
# each mirror. We now assert that for each mirror, the particular error
# detected was that metadata was expired (the Snapshot we manually
# expired).
for mirror_url, mirror_error in six.iteritems(e.mirror_errors):
self.assertTrue(isinstance(mirror_error, tuf.exceptions.ExpiredMetadataError))
self.assertTrue(mirror_url.endswith('snapshot.json'))

else:
self.fail('TUF failed to detect expired, stale Snapshot metadata.'
' Freeze attack successful.')
# mock current time to one second after snapshot expiry
mock_time = mock.Mock()
mock_time.return_value = snapshot_expiry_time + 1
with mock.patch('time.time', mock_time):
try:
# We expect the following refresh() to raise a NoWorkingMirrorError.
self.repository_updater.refresh()

except tuf.exceptions.NoWorkingMirrorError as e:
# Make sure the contained error is ExpiredMetadataError
for mirror_url, mirror_error in six.iteritems(e.mirror_errors):
self.assertTrue(isinstance(mirror_error, tuf.exceptions.ExpiredMetadataError))
self.assertTrue(mirror_url.endswith('snapshot.json'))

else:
self.fail('TUF failed to detect expired, stale Snapshot metadata.'
' Freeze attack successful.')

# The client should have rejected the malicious Snapshot metadata, and
# distrusted the local snapshot file that is no longer valid.
Expand Down
18 changes: 14 additions & 4 deletions tuf/client/updater.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1021,9 +1021,8 @@ def refresh(self, unsafely_update_root_if_necessary=True):
If the metadata for any of the top-level roles cannot be updated.

tuf.exceptions.ExpiredMetadataError:
If any of the top-level metadata is expired (whether a new version was
downloaded expired or no new version was found and the existing
version is now expired).
If any of the top-level metadata is expired and no new version was
found.

<Side Effects>
Updates the metadata files of the top-level roles with the latest
Expand Down Expand Up @@ -1900,6 +1899,9 @@ def _update_metadata_if_changed(self, metadata_role,
is 'timestamp'. See refresh().

<Exceptions>
tuf.exceptions.ExpiredMetadataError:
If local metadata is expired and newer metadata is not available.

tuf.exceptions.NoWorkingMirrorError:
If 'metadata_role' could not be downloaded after determining that it
had changed.
Expand Down Expand Up @@ -2393,7 +2395,6 @@ def _ensure_not_expired(self, metadata_object, metadata_rolename):
expires_timestamp = tuf.formats.datetime_to_unix_timestamp(expires_datetime)

current_time = int(time.time())

if expires_timestamp < current_time:
message = 'Metadata '+repr(metadata_rolename)+' expired on ' + \
expires_datetime.ctime() + ' (UTC).'
Expand Down Expand Up @@ -2495,6 +2496,9 @@ def _refresh_targets_metadata(self, rolename='targets',
repository (via snapshot.json) should be refreshed.

<Exceptions>
tuf.exceptions.ExpiredMetadataError:
If local metadata is expired and newer metadata is not available.

tuf.exceptions.RepositoryError:
If the metadata file for the 'targets' role is missing from the
'snapshot' metadata.
Expand Down Expand Up @@ -2715,6 +2719,9 @@ def get_one_valid_targetinfo(self, target_filepath):
the 'targets' (or equivalent) directory on a given mirror.

<Exceptions>
tuf.exceptions.ExpiredMetadataError:
If local metadata is expired and newer metadata is not available.

securesystemslib.exceptions.FormatError:
If 'target_filepath' is improperly formatted.

Expand Down Expand Up @@ -2770,6 +2777,9 @@ def _preorder_depth_first_walk(self, target_filepath):
the 'targets' (or equivalent) directory on a given mirror.

<Exceptions>
tuf.exceptions.ExpiredMetadataError:
If local metadata is expired and newer metadata is not available.

securesystemslib.exceptions.FormatError:
If 'target_filepath' is improperly formatted.

Expand Down