From: Zooko O'Whielacronx Date: Thu, 8 Jan 2009 06:40:12 +0000 (-0700) Subject: immutable: fix error in validation of ciphertext hash tree and add test for that... X-Git-Url: https://git.rkrishnan.org/Site/Content/Exhibitors/nxhtml.html?a=commitdiff_plain;h=83b97ee79fdf75e51db1afe6d02dad50715cc9f2;p=tahoe-lafs%2Ftahoe-lafs.git immutable: fix error in validation of ciphertext hash tree and add test for that code pyflakes pointed out to me that I had committed some code that is untested, since it uses an undefined name. This patch exercises that code -- the validation of the ciphertext hash tree -- by corrupting some of the share files in a very specific way, and also fixes the bug. --- diff --git a/src/allmydata/immutable/download.py b/src/allmydata/immutable/download.py index c3104ded..0f5a0f81 100644 --- a/src/allmydata/immutable/download.py +++ b/src/allmydata/immutable/download.py @@ -175,7 +175,7 @@ class ValidatedCrypttextHashTreeProxy: # TODO: It would have better alacrity if we downloaded only part of the crypttext hash tree at a time. for segnum in range(self._num_segments): if self._crypttext_hash_tree.needed_hashes(segnum): - raise NotEnoughHashesError("not enough hashes to validate segment number %d" % (segnum,)) + raise BadOrMissingHash("not enough hashes to validate segment number %d" % (segnum,)) return self def start(self): diff --git a/src/allmydata/test/test_immutable.py b/src/allmydata/test/test_immutable.py index 7c7923db..06674726 100644 --- a/src/allmydata/test/test_immutable.py +++ b/src/allmydata/test/test_immutable.py @@ -3,7 +3,7 @@ from allmydata.monitor import Monitor from allmydata import check_results from allmydata.interfaces import IURI, NotEnoughSharesError from allmydata.immutable import upload -from allmydata.util import log +from allmydata.util import hashutil, log from twisted.internet import defer from twisted.trial import unittest import random, struct @@ -112,6 +112,23 @@ def _corrupt_offset_of_block_hashes(data): else: return corrupt_field(data, 0x0c+0x2c, 8) +def _corrupt_offset_of_block_hashes_to_truncate_crypttext_hashes(data): + """ Scramble the file data -- the field showing the offset of the block hash tree within the + share data will have a multiple of hash size subtracted from it, thus causing the downloader + to download an incomplete crypttext hash tree.""" + sharevernum = struct.unpack(">l", data[0x0c:0x0c+4])[0] + assert sharevernum in (1, 2), "This test is designed to corrupt immutable shares of v1 or v2 in specific ways." + if sharevernum == 1: + curval = struct.unpack(">L", data[0x0c+0x18:0x0c+0x18+4])[0] + newval = random.randrange(0, max(1, (curval/hashutil.CRYPTO_VAL_SIZE)/2))*hashutil.CRYPTO_VAL_SIZE + newvalstr = struct.pack(">L", newval) + return data[:0x0c+0x18]+newvalstr+data[0x0c+0x18+4:] + else: + curval = struct.unpack(">Q", data[0x0c+0x2c:0x0c+0x2c+8])[0] + newval = random.randrange(0, max(1, (curval/hashutil.CRYPTO_VAL_SIZE)/2))*hashutil.CRYPTO_VAL_SIZE + newvalstr = struct.pack(">Q", newval) + return data[:0x0c+0x2c]+newvalstr+data[0x0c+0x2c+8:] + def _corrupt_offset_of_share_hashes(data): """ Scramble the file data -- the field showing the offset of the share hash tree within the share data will have one bit flipped or else will be changed to a random value. """ @@ -244,7 +261,11 @@ class Test(ShareManglingMixin, unittest.TestCase): d.addCallback(lambda x: self.set_up_nodes()) def _upload_a_file(ignored): - d2 = self.clients[0].upload(upload.Data(TEST_DATA, convergence="")) + client = self.clients[0] + # We need multiple segments to test crypttext hash tree's that are non-trivial + # (i.e. they have more than just one hash in them). + client.DEFAULT_ENCODING_PARAMETERS['max_segment_size'] = 12 + d2 = client.upload(upload.Data(TEST_DATA, convergence="")) def _after_upload(u): self.uri = IURI(u.uri) return self.clients[0].create_node_from_uri(self.uri) @@ -387,10 +408,7 @@ class Test(ShareManglingMixin, unittest.TestCase): before_download_reads = self._count_reads() def _after_download(unused=None): after_download_reads = self._count_reads() - # To pass this test, you have to download the file using only 10 reads total: 3 to - # get the headers from each share, 3 to get the share hash trees and uebs from each - # share, 1 to get the crypttext hashes, and 3 to get the block data from each share. - self.failIf(after_download_reads-before_download_reads > 12, (after_download_reads, before_download_reads)) + self.failIf(after_download_reads-before_download_reads > 27, (after_download_reads, before_download_reads)) d.addCallback(self._download_and_check_plaintext) d.addCallback(_after_download) return d @@ -405,13 +423,24 @@ class Test(ShareManglingMixin, unittest.TestCase): d.addCallback(_then_delete_7) def _after_download(unused=None): after_download_reads = self._count_reads() - # To pass this test, you have to download the file using only 10 reads to get the - # UEB (in parallel from all shares), plus one read for each of the 3 shares. - self.failIf(after_download_reads-before_download_reads > 13, (after_download_reads, before_download_reads)) + self.failIf(after_download_reads-before_download_reads > 27, (after_download_reads, before_download_reads)) d.addCallback(self._download_and_check_plaintext) d.addCallback(_after_download) return d + def test_download_from_only_3_shares_with_good_crypttext_hash(self): + """ Test download after 7 random shares (of the 10) have had their crypttext hash tree corrupted. """ + d = defer.succeed(None) + def _then_corrupt_7(unused=None): + shnums = range(10) + random.shuffle(shnums) + for i in shnums[:7]: + self._corrupt_a_share(None, _corrupt_offset_of_block_hashes_to_truncate_crypttext_hashes, i) + before_download_reads = self._count_reads() + d.addCallback(_then_corrupt_7) + d.addCallback(self._download_and_check_plaintext) + return d + def test_download_abort_if_too_many_missing_shares(self): """ Test that download gives up quickly when it realizes there aren't enough shares out there.""" @@ -515,7 +544,7 @@ class Test(ShareManglingMixin, unittest.TestCase): return d def _help_test_verify(self, corruptor_funcs, judgement_func): - LEEWAY = 7 # We'll allow you to pass this test even if you trigger seven times as many disk reads and blocks sends as would be optimal. + LEEWAY = 18 # We'll allow you to pass this test even if you trigger eighteen times as many disk reads and blocks sends as would be optimal. DELTA_READS = 10 * LEEWAY # N = 10 d = defer.succeed(None) @@ -534,7 +563,7 @@ class Test(ShareManglingMixin, unittest.TestCase): d2 = self.filenode.check(Monitor(), verify=True) def _after_check(checkresults): after_check_reads = self._count_reads() - self.failIf(after_check_reads - before_check_reads > DELTA_READS) + self.failIf(after_check_reads - before_check_reads > DELTA_READS, (after_check_reads, before_check_reads)) try: return judgement_func(checkresults) except Exception, le: @@ -638,6 +667,26 @@ class Test(ShareManglingMixin, unittest.TestCase): _corrupt_uri_extension, ], judge) + def test_verify_server_invisible_corruption_offset_of_block_hashtree_to_truncate_crypttext_hashtree_TODO(self): + def judge(checkresults): + self.failIf(checkresults.is_healthy(), (checkresults, checkresults.is_healthy(), checkresults.get_data())) + data = checkresults.get_data() + self.failUnless(data['count-shares-good'] == 9, data) + self.failUnless(data['count-shares-needed'] == 3, data) + self.failUnless(data['count-shares-expected'] == 10, data) + self.failUnless(data['count-good-share-hosts'] == 5, data) + self.failUnless(data['count-corrupt-shares'] == 1, (data,)) + self.failUnless(len(data['list-corrupt-shares']) == 1, data) + self.failUnless(len(data['list-corrupt-shares']) == data['count-corrupt-shares'], data) + self.failUnless(len(data['list-incompatible-shares']) == data['count-incompatible-shares'], data) + self.failUnless(len(data['list-incompatible-shares']) == 0, data) + self.failUnless(len(data['servers-responding']) == 5, data) + self.failUnless(len(data['sharemap']) == 9, data) + return self._help_test_verify([ + _corrupt_offset_of_block_hashes_to_truncate_crypttext_hashes, + ], judge) + test_verify_server_invisible_corruption_offset_of_block_hashtree_to_truncate_crypttext_hashtree_TODO.todo = "Verifier doesn't yet properly detect this kind of corruption." + def test_verify_server_invisible_corruption_offset_of_block_hashtree_TODO(self): def judge(checkresults): self.failIf(checkresults.is_healthy(), (checkresults, checkresults.is_healthy(), checkresults.get_data())) @@ -905,3 +954,5 @@ class Test(ShareManglingMixin, unittest.TestCase): # XXX extend these tests to show bad behavior of various kinds from servers: raising exception from each remove_foo() method, for example # XXX test disconnect DeadReferenceError from get_buckets and get_block_whatsit + +# XXX test corruption that truncates other hash trees than just the crypttext hash tree