def _got_results_one_share(self, shnum, peerid, got_prefix,
got_hash_and_data):
self.log("_got_results: got shnum #%d from peerid %s" %
(shnum, idlib.shortnodeid_b2a(peerid)))
(seqnum, root_hash, IV, segsize, datalength, k, N, prefix,
offsets_tuple) = self.verinfo
assert len(got_prefix) == len(prefix), (len(got_prefix), len(prefix))
if got_prefix != prefix:
msg = "someone wrote to the data since we read the servermap: prefix changed"
raise UncoordinatedWriteError(msg)
(share_hash_chain, block_hash_tree,
share_data) = unpack_share_data(self.verinfo, got_hash_and_data)
assert isinstance(share_data, str)
# build the block hash tree. SDMF has only one leaf.
leaves = [hashutil.block_hash(share_data)]
t = hashtree.HashTree(leaves)
if list(t) != block_hash_tree:
raise CorruptShareError(peerid, shnum, "block hash tree failure")
share_hash_leaf = t[0]
t2 = hashtree.IncompleteHashTree(N)
# root_hash was checked by the signature
t2.set_hashes({0: root_hash})
try:
t2.set_hashes(hashes=share_hash_chain,
leaves={shnum: share_hash_leaf})
except (hashtree.BadHashError, hashtree.NotEnoughHashesError,
IndexError), e:
msg = "corrupt hashes: %s" % (e, )
raise CorruptShareError(peerid, shnum, msg)
def _got_results_one_share(self, shnum, peerid, data):
self.check_prefix(peerid, shnum, data)
# the [seqnum:signature] pieces are validated by _compare_prefix,
# which checks their signature against the pubkey known to be
# associated with this file.
(seqnum, root_hash, IV, k, N, segsize, datalen, pubkey, signature,
share_hash_chain, block_hash_tree, share_data,
enc_privkey) = unpack_share(data)
# validate [share_hash_chain,block_hash_tree,share_data]
leaves = [hashutil.block_hash(share_data)]
t = hashtree.HashTree(leaves)
if list(t) != block_hash_tree:
raise CorruptShareError(peerid, shnum, "block hash tree failure")
share_hash_leaf = t[0]
t2 = hashtree.IncompleteHashTree(N)
# root_hash was checked by the signature
t2.set_hashes({0: root_hash})
try:
t2.set_hashes(hashes=share_hash_chain,
leaves={shnum: share_hash_leaf})
except (hashtree.BadHashError, hashtree.NotEnoughHashesError,
IndexError), e:
msg = "corrupt hashes: %s" % (e, )
raise CorruptShareError(peerid, shnum, msg)
def _validate_block(self, results, segnum, reader, server, started):
"""
I validate a block from one share on a remote server.
"""
# Grab the part of the block hash tree that is necessary to
# validate this block, then generate the block hash root.
self.log("validating share %d for segment %d" % (reader.shnum, segnum))
elapsed = time.time() - started
self._status.add_fetch_timing(server, elapsed)
self._set_current_status("validating blocks")
block_and_salt, blockhashes, sharehashes = results
block, salt = block_and_salt
assert type(block) is str, (block, salt)
blockhashes = dict(enumerate(blockhashes))
self.log("the reader gave me the following blockhashes: %s" % \
blockhashes.keys())
self.log("the reader gave me the following sharehashes: %s" % \
sharehashes.keys())
bht = self._block_hash_trees[reader.shnum]
if bht.needed_hashes(segnum, include_leaf=True):
try:
bht.set_hashes(blockhashes)
except (hashtree.BadHashError, hashtree.NotEnoughHashesError, \
IndexError), e:
raise CorruptShareError(server, reader.shnum,
"block hash tree failure: %s" % e)
def check_prefix(self, peerid, shnum, data):
(seqnum, root_hash, IV, segsize, datalength, k, N, prefix,
offsets_tuple) = self.best_version
got_prefix = data[:SIGNED_PREFIX_LENGTH]
if got_prefix != prefix:
raise CorruptShareError(
peerid, shnum,
"prefix mismatch: share changed while we were reading it")
def _validate_block(self, results, segnum, reader, server, started):
"""
I validate a block from one share on a remote server.
"""
# Grab the part of the block hash tree that is necessary to
# validate this block, then generate the block hash root.
self.log("validating share %d for segment %d" % (reader.shnum, segnum))
elapsed = time.time() - started
self._status.add_fetch_timing(server, elapsed)
self._set_current_status("validating blocks")
# Did we fail to fetch either of the things that we were
# supposed to? Fail if so.
if not results[0][0] and results[1][0]:
# handled by the errback handler.
# These all get batched into one query, so the resulting
# failure should be the same for all of them, so we can just
# use the first one.
assert isinstance(results[0][1], failure.Failure)
f = results[0][1]
raise CorruptShareError(server, reader.shnum,
"Connection error: %s" % str(f))
block_and_salt, block_and_sharehashes = results
block, salt = block_and_salt[1]
blockhashes, sharehashes = block_and_sharehashes[1]
blockhashes = dict(enumerate(blockhashes[1]))
self.log("the reader gave me the following blockhashes: %s" % \
blockhashes.keys())
self.log("the reader gave me the following sharehashes: %s" % \
sharehashes[1].keys())
bht = self._block_hash_trees[reader.shnum]
if bht.needed_hashes(segnum, include_leaf=True):
try:
bht.set_hashes(blockhashes)
except (hashtree.BadHashError, hashtree.NotEnoughHashesError, \
IndexError), e:
raise CorruptShareError(server, reader.shnum,
"block hash tree failure: %s" % e)
def _try_to_validate_privkey(self, enc_privkey, reader, server):
alleged_privkey_s = self._node._decrypt_privkey(enc_privkey)
alleged_writekey = hashutil.ssk_writekey_hash(alleged_privkey_s)
if alleged_writekey != self._node.get_writekey():
self.log("invalid privkey from %s shnum %d" %
(reader, reader.shnum),
level=log.WEIRD,
umid="YIw4tA")
if self._verify:
self.servermap.mark_bad_share(server, reader.shnum,
self.verinfo[-2])
e = CorruptShareError(server, reader.shnum, "invalid privkey")
f = failure.Failure(e)
self._bad_shares.add((server, reader.shnum, f))
return
# it's good
self.log("got valid privkey from shnum %d on reader %s" %
(reader.shnum, reader))
privkey = rsa.create_signing_key_from_string(alleged_privkey_s)
self._node._populate_encprivkey(enc_privkey)
self._node._populate_privkey(privkey)
self._need_privkey = False
class MutableChecker:
def __init__(self, node, storage_broker, history, monitor):
self._node = node
self._storage_broker = storage_broker
self._history = history
self._monitor = monitor
self.bad_shares = [] # list of (nodeid,shnum,failure)
self._storage_index = self._node.get_storage_index()
self.results = CheckResults(from_string(node.get_uri()),
self._storage_index)
self.need_repair = False
self.responded = set() # set of (binary) nodeids
def check(self, verify=False, add_lease=False):
servermap = ServerMap()
u = ServermapUpdater(self._node,
self._storage_broker,
self._monitor,
servermap,
MODE_CHECK,
add_lease=add_lease)
if self._history:
self._history.notify_mapupdate(u.get_status())
d = u.update()
d.addCallback(self._got_mapupdate_results)
if verify:
d.addCallback(self._verify_all_shares)
d.addCallback(lambda res: servermap)
d.addCallback(self._fill_checker_results, self.results)
d.addCallback(lambda res: self.results)
return d
def _got_mapupdate_results(self, servermap):
# the file is healthy if there is exactly one recoverable version, it
# has at least N distinct shares, and there are no unrecoverable
# versions: all existing shares will be for the same version.
self._monitor.raise_if_cancelled()
self.best_version = None
num_recoverable = len(servermap.recoverable_versions())
if num_recoverable:
self.best_version = servermap.best_recoverable_version()
if servermap.unrecoverable_versions():
self.need_repair = True
if num_recoverable != 1:
self.need_repair = True
if self.best_version:
available_shares = servermap.shares_available()
(num_distinct_shares, k, N) = available_shares[self.best_version]
if num_distinct_shares < N:
self.need_repair = True
return servermap
def _verify_all_shares(self, servermap):
# read every byte of each share
if not self.best_version:
return
versionmap = servermap.make_versionmap()
shares = versionmap[self.best_version]
(seqnum, root_hash, IV, segsize, datalength, k, N, prefix,
offsets_tuple) = self.best_version
offsets = dict(offsets_tuple)
readv = [(0, offsets["EOF"])]
dl = []
for (shnum, peerid, timestamp) in shares:
ss = servermap.connections[peerid]
d = self._do_read(ss, peerid, self._storage_index, [shnum], readv)
d.addCallback(self._got_answer, peerid, servermap)
dl.append(d)
return defer.DeferredList(dl,
fireOnOneErrback=True,
consumeErrors=True)
def _do_read(self, ss, peerid, storage_index, shnums, readv):
# isolate the callRemote to a separate method, so tests can subclass
# Publish and override it
d = ss.callRemote("slot_readv", storage_index, shnums, readv)
return d
def _got_answer(self, datavs, peerid, servermap):
for shnum, datav in datavs.items():
data = datav[0]
try:
self._got_results_one_share(shnum, peerid, data)
except CorruptShareError:
f = failure.Failure()
self.need_repair = True
self.bad_shares.append((peerid, shnum, f))
prefix = data[:SIGNED_PREFIX_LENGTH]
servermap.mark_bad_share(peerid, shnum, prefix)
ss = servermap.connections[peerid]
self.notify_server_corruption(ss, shnum, str(f.value))
def check_prefix(self, peerid, shnum, data):
(seqnum, root_hash, IV, segsize, datalength, k, N, prefix,
offsets_tuple) = self.best_version
got_prefix = data[:SIGNED_PREFIX_LENGTH]
if got_prefix != prefix:
raise CorruptShareError(
peerid, shnum,
"prefix mismatch: share changed while we were reading it")
def _got_results_one_share(self, shnum, peerid, data):
self.check_prefix(peerid, shnum, data)
# the [seqnum:signature] pieces are validated by _compare_prefix,
# which checks their signature against the pubkey known to be
# associated with this file.
(seqnum, root_hash, IV, k, N, segsize, datalen, pubkey, signature,
share_hash_chain, block_hash_tree, share_data,
enc_privkey) = unpack_share(data)
# validate [share_hash_chain,block_hash_tree,share_data]
leaves = [hashutil.block_hash(share_data)]
t = hashtree.HashTree(leaves)
if list(t) != block_hash_tree:
raise CorruptShareError(peerid, shnum, "block hash tree failure")
share_hash_leaf = t[0]
t2 = hashtree.IncompleteHashTree(N)
# root_hash was checked by the signature
t2.set_hashes({0: root_hash})
try:
t2.set_hashes(hashes=share_hash_chain,
leaves={shnum: share_hash_leaf})
except (hashtree.BadHashError, hashtree.NotEnoughHashesError,
IndexError), e:
msg = "corrupt hashes: %s" % (e, )
raise CorruptShareError(peerid, shnum, msg)
# validate enc_privkey: only possible if we have a write-cap
if not self._node.is_readonly():
alleged_privkey_s = self._node._decrypt_privkey(enc_privkey)
alleged_writekey = hashutil.ssk_writekey_hash(alleged_privkey_s)
if alleged_writekey != self._node.get_writekey():
raise CorruptShareError(peerid, shnum, "invalid privkey")
class Retrieve:
# this class is currently single-use. Eventually (in MDMF) we will make
# it multi-use, in which case you can call download(range) multiple
# times, and each will have a separate response chain. However the
# Retrieve object will remain tied to a specific version of the file, and
# will use a single ServerMap instance.
implements(IPushProducer)
def __init__(self,
filenode,
storage_broker,
servermap,
verinfo,
fetch_privkey=False,
verify=False):
self._node = filenode
assert self._node.get_pubkey()
self._storage_broker = storage_broker
self._storage_index = filenode.get_storage_index()
assert self._node.get_readkey()
self._last_failure = None
prefix = si_b2a(self._storage_index)[:5]
self._log_number = log.msg("Retrieve(%s): starting" % prefix)
self._running = True
self._decoding = False
self._bad_shares = set()
self.servermap = servermap
assert self._node.get_pubkey()
self.verinfo = verinfo
# during repair, we may be called upon to grab the private key, since
# it wasn't picked up during a verify=False checker run, and we'll
# need it for repair to generate a new version.
self._need_privkey = verify or (fetch_privkey
and not self._node.get_privkey())
if self._need_privkey:
# TODO: Evaluate the need for this. We'll use it if we want
# to limit how many queries are on the wire for the privkey
# at once.
self._privkey_query_markers = [] # one Marker for each time we've
# tried to get the privkey.
# verify means that we are using the downloader logic to verify all
# of our shares. This tells the downloader a few things.
#
# 1. We need to download all of the shares.
# 2. We don't need to decode or decrypt the shares, since our
# caller doesn't care about the plaintext, only the
# information about which shares are or are not valid.
# 3. When we are validating readers, we need to validate the
# signature on the prefix. Do we? We already do this in the
# servermap update?
self._verify = verify
self._status = RetrieveStatus()
self._status.set_storage_index(self._storage_index)
self._status.set_helper(False)
self._status.set_progress(0.0)
self._status.set_active(True)
(seqnum, root_hash, IV, segsize, datalength, k, N, prefix,
offsets_tuple) = self.verinfo
self._status.set_size(datalength)
self._status.set_encoding(k, N)
self.readers = {}
self._stopped = False
self._pause_deferred = None
self._offset = None
self._read_length = None
self.log("got seqnum %d" % self.verinfo[0])
def get_status(self):
return self._status
def log(self, *args, **kwargs):
if "parent" not in kwargs:
kwargs["parent"] = self._log_number
if "facility" not in kwargs:
kwargs["facility"] = "tahoe.mutable.retrieve"
return log.msg(*args, **kwargs)
def _set_current_status(self, state):
seg = "%d/%d" % (self._current_segment, self._last_segment)
self._status.set_status("segment %s (%s)" % (seg, state))
###################
# IPushProducer
def pauseProducing(self):
"""
I am called by my download target if we have produced too much
data for it to handle. I make the downloader stop producing new
data until my resumeProducing method is called.
"""
if self._pause_deferred is not None:
return
# fired when the download is unpaused.
self._old_status = self._status.get_status()
self._set_current_status("paused")
self._pause_deferred = defer.Deferred()
def resumeProducing(self):
"""
I am called by my download target once it is ready to begin
receiving data again.
"""
if self._pause_deferred is None:
return
p = self._pause_deferred
self._pause_deferred = None
self._status.set_status(self._old_status)
eventually(p.callback, None)
def stopProducing(self):
self._stopped = True
self.resumeProducing()
def _check_for_paused(self, res):
"""
I am called just before a write to the consumer. I return a
Deferred that eventually fires with the data that is to be
written to the consumer. If the download has not been paused,
the Deferred fires immediately. Otherwise, the Deferred fires
when the downloader is unpaused.
"""
if self._pause_deferred is not None:
d = defer.Deferred()
self._pause_deferred.addCallback(lambda ignored: d.callback(res))
return d
return res
def _check_for_stopped(self, res):
if self._stopped:
raise DownloadStopped("our Consumer called stopProducing()")
return res
def download(self, consumer=None, offset=0, size=None):
assert IConsumer.providedBy(consumer) or self._verify
if consumer:
self._consumer = consumer
# we provide IPushProducer, so streaming=True, per
# IConsumer.
self._consumer.registerProducer(self, streaming=True)
self._done_deferred = defer.Deferred()
self._offset = offset
self._read_length = size
self._setup_encoding_parameters()
self._setup_download()
self.log("starting download")
self._started_fetching = time.time()
# The download process beyond this is a state machine.
# _add_active_servers will select the servers that we want to use
# for the download, and then attempt to start downloading. After
# each segment, it will check for doneness, reacting to broken
# servers and corrupt shares as necessary. If it runs out of good
# servers before downloading all of the segments, _done_deferred
# will errback. Otherwise, it will eventually callback with the
# contents of the mutable file.
self.loop()
return self._done_deferred
def loop(self):
d = fireEventually(None) # avoid #237 recursion limit problem
d.addCallback(lambda ign: self._activate_enough_servers())
d.addCallback(lambda ign: self._download_current_segment())
# when we're done, _download_current_segment will call _done. If we
# aren't, it will call loop() again.
d.addErrback(self._error)
def _setup_download(self):
self._started = time.time()
self._status.set_status("Retrieving Shares")
# how many shares do we need?
(seqnum, root_hash, IV, segsize, datalength, k, N, prefix,
offsets_tuple) = self.verinfo
# first, which servers can we use?
versionmap = self.servermap.make_versionmap()
shares = versionmap[self.verinfo]
# this sharemap is consumed as we decide to send requests
self.remaining_sharemap = DictOfSets()
for (shnum, server, timestamp) in shares:
self.remaining_sharemap.add(shnum, server)
# Reuse the SlotReader from the servermap.
key = (self.verinfo, server.get_serverid(), self._storage_index,
shnum)
if key in self.servermap.proxies:
reader = self.servermap.proxies[key]
else:
reader = MDMFSlotReadProxy(server.get_rref(),
self._storage_index, shnum, None)
reader.server = server
self.readers[shnum] = reader
if len(self.remaining_sharemap) < k:
self._raise_notenoughshareserror()
self.shares = {} # maps shnum to validated blocks
self._active_readers = [] # list of active readers for this dl.
self._block_hash_trees = {} # shnum => hashtree
for i in xrange(self._total_shares):
# So we don't have to do this later.
self._block_hash_trees[i] = hashtree.IncompleteHashTree(
self._num_segments)
# We need one share hash tree for the entire file; its leaves
# are the roots of the block hash trees for the shares that
# comprise it, and its root is in the verinfo.
self.share_hash_tree = hashtree.IncompleteHashTree(N)
self.share_hash_tree.set_hashes({0: root_hash})
def decode(self, blocks_and_salts, segnum):
"""
I am a helper method that the mutable file update process uses
as a shortcut to decode and decrypt the segments that it needs
to fetch in order to perform a file update. I take in a
collection of blocks and salts, and pick some of those to make a
segment with. I return the plaintext associated with that
segment.
"""
# We don't need the block hash trees in this case.
self._block_hash_trees = None
self._setup_encoding_parameters()
# _decode_blocks() expects the output of a gatherResults that
# contains the outputs of _validate_block() (each of which is a dict
# mapping shnum to (block,salt) bytestrings).
d = self._decode_blocks([blocks_and_salts], segnum)
d.addCallback(self._decrypt_segment)
return d
def _setup_encoding_parameters(self):
"""
I set up the encoding parameters, including k, n, the number
of segments associated with this file, and the segment decoders.
"""
(seqnum, root_hash, IV, segsize, datalength, k, n, known_prefix,
offsets_tuple) = self.verinfo
self._required_shares = k
self._total_shares = n
self._segment_size = segsize
self._data_length = datalength
if not IV:
self._version = MDMF_VERSION
else:
self._version = SDMF_VERSION
if datalength and segsize:
self._num_segments = mathutil.div_ceil(datalength, segsize)
self._tail_data_size = datalength % segsize
else:
self._num_segments = 0
self._tail_data_size = 0
self._segment_decoder = codec.CRSDecoder()
self._segment_decoder.set_params(segsize, k, n)
if not self._tail_data_size:
self._tail_data_size = segsize
self._tail_segment_size = mathutil.next_multiple(
self._tail_data_size, self._required_shares)
if self._tail_segment_size == self._segment_size:
self._tail_decoder = self._segment_decoder
else:
self._tail_decoder = codec.CRSDecoder()
self._tail_decoder.set_params(self._tail_segment_size,
self._required_shares,
self._total_shares)
self.log("got encoding parameters: "
"k: %d "
"n: %d "
"%d segments of %d bytes each (%d byte tail segment)" % \
(k, n, self._num_segments, self._segment_size,
self._tail_segment_size))
# Our last task is to tell the downloader where to start and
# where to stop. We use three parameters for that:
# - self._start_segment: the segment that we need to start
# downloading from.
# - self._current_segment: the next segment that we need to
# download.
# - self._last_segment: The last segment that we were asked to
# download.
#
# We say that the download is complete when
# self._current_segment > self._last_segment. We use
# self._start_segment and self._last_segment to know when to
# strip things off of segments, and how much to strip.
if self._offset:
self.log("got offset: %d" % self._offset)
# our start segment is the first segment containing the
# offset we were given.
start = self._offset // self._segment_size
assert start < self._num_segments
self._start_segment = start
self.log("got start segment: %d" % self._start_segment)
else:
self._start_segment = 0
# If self._read_length is None, then we want to read the whole
# file. Otherwise, we want to read only part of the file, and
# need to figure out where to stop reading.
if self._read_length is not None:
# our end segment is the last segment containing part of the
# segment that we were asked to read.
self.log("got read length %d" % self._read_length)
if self._read_length != 0:
end_data = self._offset + self._read_length
# We don't actually need to read the byte at end_data,
# but the one before it.
end = (end_data - 1) // self._segment_size
assert end < self._num_segments
self._last_segment = end
else:
self._last_segment = self._start_segment
self.log("got end segment: %d" % self._last_segment)
else:
self._last_segment = self._num_segments - 1
self._current_segment = self._start_segment
def _activate_enough_servers(self):
"""
I populate self._active_readers with enough active readers to
retrieve the contents of this mutable file. I am called before
downloading starts, and (eventually) after each validation
error, connection error, or other problem in the download.
"""
# TODO: It would be cool to investigate other heuristics for
# reader selection. For instance, the cost (in time the user
# spends waiting for their file) of selecting a really slow server
# that happens to have a primary share is probably more than
# selecting a really fast server that doesn't have a primary
# share. Maybe the servermap could be extended to provide this
# information; it could keep track of latency information while
# it gathers more important data, and then this routine could
# use that to select active readers.
#
# (these and other questions would be easier to answer with a
# robust, configurable tahoe-lafs simulator, which modeled node
# failures, differences in node speed, and other characteristics
# that we expect storage servers to have. You could have
# presets for really stable grids (like allmydata.com),
# friendnets, make it easy to configure your own settings, and
# then simulate the effect of big changes on these use cases
# instead of just reasoning about what the effect might be. Out
# of scope for MDMF, though.)
# XXX: Why don't format= log messages work here?
known_shnums = set(self.remaining_sharemap.keys())
used_shnums = set([r.shnum for r in self._active_readers])
unused_shnums = known_shnums - used_shnums
if self._verify:
new_shnums = unused_shnums # use them all
elif len(self._active_readers) < self._required_shares:
# need more shares
more = self._required_shares - len(self._active_readers)
# We favor lower numbered shares, since FEC is faster with
# primary shares than with other shares, and lower-numbered
# shares are more likely to be primary than higher numbered
# shares.
new_shnums = sorted(unused_shnums)[:more]
if len(new_shnums) < more:
# We don't have enough readers to retrieve the file; fail.
self._raise_notenoughshareserror()
else:
new_shnums = []
self.log("adding %d new servers to the active list" % len(new_shnums))
for shnum in new_shnums:
reader = self.readers[shnum]
self._active_readers.append(reader)
self.log("added reader for share %d" % shnum)
# Each time we add a reader, we check to see if we need the
# private key. If we do, we politely ask for it and then continue
# computing. If we find that we haven't gotten it at the end of
# segment decoding, then we'll take more drastic measures.
if self._need_privkey and not self._node.is_readonly():
d = reader.get_encprivkey()
d.addCallback(self._try_to_validate_privkey, reader,
reader.server)
# XXX: don't just drop the Deferred. We need error-reporting
# but not flow-control here.
def _try_to_validate_prefix(self, prefix, reader):
"""
I check that the prefix returned by a candidate server for
retrieval matches the prefix that the servermap knows about
(and, hence, the prefix that was validated earlier). If it does,
I return True, which means that I approve of the use of the
candidate server for segment retrieval. If it doesn't, I return
False, which means that another server must be chosen.
"""
(seqnum, root_hash, IV, segsize, datalength, k, N, known_prefix,
offsets_tuple) = self.verinfo
if known_prefix != prefix:
self.log("prefix from share %d doesn't match" % reader.shnum)
raise UncoordinatedWriteError("Mismatched prefix -- this could "
"indicate an uncoordinated write")
# Otherwise, we're okay -- no issues.
def _mark_bad_share(self, server, shnum, reader, f):
"""
I mark the given (server, shnum) as a bad share, which means that it
will not be used anywhere else.
There are several reasons to want to mark something as a bad
share. These include:
- A connection error to the server.
- A mismatched prefix (that is, a prefix that does not match
our local conception of the version information string).
- A failing block hash, salt hash, share hash, or other
integrity check.
This method will ensure that readers that we wish to mark bad
(for these reasons or other reasons) are not used for the rest
of the download. Additionally, it will attempt to tell the
remote server (with no guarantee of success) that its share is
corrupt.
"""
self.log("marking share %d on server %s as bad" % \
(shnum, server.get_name()))
prefix = self.verinfo[-2]
self.servermap.mark_bad_share(server, shnum, prefix)
self._bad_shares.add((server, shnum, f))
self._status.add_problem(server, f)
self._last_failure = f
# Remove the reader from _active_readers
self._active_readers.remove(reader)
for shnum in list(self.remaining_sharemap.keys()):
self.remaining_sharemap.discard(shnum, reader.server)
if f.check(BadShareError):
self.notify_server_corruption(server, shnum, str(f.value))
def _download_current_segment(self):
"""
I download, validate, decode, decrypt, and assemble the segment
that this Retrieve is currently responsible for downloading.
"""
if self._current_segment > self._last_segment:
# No more segments to download, we're done.
self.log("got plaintext, done")
return self._done()
elif self._verify and len(self._active_readers) == 0:
self.log("no more good shares, no need to keep verifying")
return self._done()
self.log("on segment %d of %d" %
(self._current_segment + 1, self._num_segments))
d = self._process_segment(self._current_segment)
d.addCallback(lambda ign: self.loop())
return d
def _process_segment(self, segnum):
"""
I download, validate, decode, and decrypt one segment of the
file that this Retrieve is retrieving. This means coordinating
the process of getting k blocks of that file, validating them,
assembling them into one segment with the decoder, and then
decrypting them.
"""
self.log("processing segment %d" % segnum)
# TODO: The old code uses a marker. Should this code do that
# too? What did the Marker do?
# We need to ask each of our active readers for its block and
# salt. We will then validate those. If validation is
# successful, we will assemble the results into plaintext.
ds = []
for reader in self._active_readers:
started = time.time()
d1 = reader.get_block_and_salt(segnum)
d2, d3 = self._get_needed_hashes(reader, segnum)
d = deferredutil.gatherResults([d1, d2, d3])
d.addCallback(self._validate_block, segnum, reader, reader.server,
started)
# _handle_bad_share takes care of recoverable errors (by dropping
# that share and returning None). Any other errors (i.e. code
# bugs) are passed through and cause the retrieve to fail.
d.addErrback(self._handle_bad_share, [reader])
ds.append(d)
dl = deferredutil.gatherResults(ds)
if self._verify:
dl.addCallback(lambda ignored: "")
dl.addCallback(self._set_segment)
else:
dl.addCallback(self._maybe_decode_and_decrypt_segment, segnum)
return dl
def _maybe_decode_and_decrypt_segment(self, results, segnum):
"""
I take the results of fetching and validating the blocks from
_process_segment. If validation and fetching succeeded without
incident, I will proceed with decoding and decryption. Otherwise, I
will do nothing.
"""
self.log("trying to decode and decrypt segment %d" % segnum)
# 'results' is the output of a gatherResults set up in
# _process_segment(). Each component Deferred will either contain the
# non-Failure output of _validate_block() for a single block (i.e.
# {segnum:(block,salt)}), or None if _validate_block threw an
# exception and _validation_or_decoding_failed handled it (by
# dropping that server).
if None in results:
self.log("some validation operations failed; not proceeding")
return defer.succeed(None)
self.log("everything looks ok, building segment %d" % segnum)
d = self._decode_blocks(results, segnum)
d.addCallback(self._decrypt_segment)
# check to see whether we've been paused before writing
# anything.
d.addCallback(self._check_for_paused)
d.addCallback(self._check_for_stopped)
d.addCallback(self._set_segment)
return d
def _set_segment(self, segment):
"""
Given a plaintext segment, I register that segment with the
target that is handling the file download.
"""
self.log("got plaintext for segment %d" % self._current_segment)
if self._current_segment == self._start_segment:
# We're on the first segment. It's possible that we want
# only some part of the end of this segment, and that we
# just downloaded the whole thing to get that part. If so,
# we need to account for that and give the reader just the
# data that they want.
n = self._offset % self._segment_size
self.log("stripping %d bytes off of the first segment" % n)
self.log("original segment length: %d" % len(segment))
segment = segment[n:]
self.log("new segment length: %d" % len(segment))
if self._current_segment == self._last_segment and self._read_length is not None:
# We're on the last segment. It's possible that we only want
# part of the beginning of this segment, and that we
# downloaded the whole thing anyway. Make sure to give the
# caller only the portion of the segment that they want to
# receive.
extra = self._read_length
if self._start_segment != self._last_segment:
extra -= self._segment_size - \
(self._offset % self._segment_size)
extra %= self._segment_size
self.log("original segment length: %d" % len(segment))
segment = segment[:extra]
self.log("new segment length: %d" % len(segment))
self.log("only taking %d bytes of the last segment" % extra)
if not self._verify:
self._consumer.write(segment)
else:
# we don't care about the plaintext if we are doing a verify.
segment = None
self._current_segment += 1
def _handle_bad_share(self, f, readers):
"""
I am called when a block or a salt fails to correctly validate, or when
the decryption or decoding operation fails for some reason. I react to
this failure by notifying the remote server of corruption, and then
removing the remote server from further activity.
"""
# these are the errors we can tolerate: by giving up on this share
# and finding others to replace it. Any other errors (i.e. coding
# bugs) are re-raised, causing the download to fail.
f.trap(DeadReferenceError, RemoteException, BadShareError)
# DeadReferenceError happens when we try to fetch data from a server
# that has gone away. RemoteException happens if the server had an
# internal error. BadShareError encompasses: (UnknownVersionError,
# LayoutInvalid, struct.error) which happen when we get obviously
# wrong data, and CorruptShareError which happens later, when we
# perform integrity checks on the data.
assert isinstance(readers, list)
bad_shnums = [reader.shnum for reader in readers]
self.log("validation or decoding failed on share(s) %s, server(s) %s "
", segment %d: %s" % \
(bad_shnums, readers, self._current_segment, str(f)))
for reader in readers:
self._mark_bad_share(reader.server, reader.shnum, reader, f)
return None
def _validate_block(self, results, segnum, reader, server, started):
"""
I validate a block from one share on a remote server.
"""
# Grab the part of the block hash tree that is necessary to
# validate this block, then generate the block hash root.
self.log("validating share %d for segment %d" % (reader.shnum, segnum))
elapsed = time.time() - started
self._status.add_fetch_timing(server, elapsed)
self._set_current_status("validating blocks")
block_and_salt, blockhashes, sharehashes = results
block, salt = block_and_salt
assert type(block) is str, (block, salt)
blockhashes = dict(enumerate(blockhashes))
self.log("the reader gave me the following blockhashes: %s" % \
blockhashes.keys())
self.log("the reader gave me the following sharehashes: %s" % \
sharehashes.keys())
bht = self._block_hash_trees[reader.shnum]
if bht.needed_hashes(segnum, include_leaf=True):
try:
bht.set_hashes(blockhashes)
except (hashtree.BadHashError, hashtree.NotEnoughHashesError, \
IndexError), e:
raise CorruptShareError(server, reader.shnum,
"block hash tree failure: %s" % e)
if self._version == MDMF_VERSION:
blockhash = hashutil.block_hash(salt + block)
else:
blockhash = hashutil.block_hash(block)
# If this works without an error, then validation is
# successful.
try:
bht.set_hashes(leaves={segnum: blockhash})
except (hashtree.BadHashError, hashtree.NotEnoughHashesError, \
IndexError), e:
raise CorruptShareError(server, reader.shnum,
"block hash tree failure: %s" % e)
# Reaching this point means that we know that this segment
# is correct. Now we need to check to see whether the share
# hash chain is also correct.
# SDMF wrote share hash chains that didn't contain the
# leaves, which would be produced from the block hash tree.
# So we need to validate the block hash tree first. If
# successful, then bht[0] will contain the root for the
# shnum, which will be a leaf in the share hash tree, which
# will allow us to validate the rest of the tree.
try:
self.share_hash_tree.set_hashes(hashes=sharehashes,
leaves={reader.shnum: bht[0]})
except (hashtree.BadHashError, hashtree.NotEnoughHashesError, \
IndexError), e:
raise CorruptShareError(server, reader.shnum,
"corrupt hashes: %s" % e)
self.log('share %d is valid for segment %d' % (reader.shnum, segnum))
return {reader.shnum: (block, salt)}
def _get_needed_hashes(self, reader, segnum):
"""
I get the hashes needed to validate segnum from the reader, then return
to my caller when this is done.
"""
bht = self._block_hash_trees[reader.shnum]
needed = bht.needed_hashes(segnum, include_leaf=True)
# The root of the block hash tree is also a leaf in the share
# hash tree. So we don't need to fetch it from the remote
# server. In the case of files with one segment, this means that
# we won't fetch any block hash tree from the remote server,
def _validate_block(self, results, segnum, reader, server, started):
"""
I validate a block from one share on a remote server.
"""
# Grab the part of the block hash tree that is necessary to
# validate this block, then generate the block hash root.
self.log("validating share %d for segment %d" % (reader.shnum, segnum))
elapsed = time.time() - started
self._status.add_fetch_timing(server, elapsed)
self._set_current_status("validating blocks")
block_and_salt, blockhashes, sharehashes = results
block, salt = block_and_salt
_assert(isinstance(block, bytes), (block, salt))
blockhashes = dict(enumerate(blockhashes))
self.log("the reader gave me the following blockhashes: %s" % \
list(blockhashes.keys()))
self.log("the reader gave me the following sharehashes: %s" % \
list(sharehashes.keys()))
bht = self._block_hash_trees[reader.shnum]
if bht.needed_hashes(segnum, include_leaf=True):
try:
bht.set_hashes(blockhashes)
except (hashtree.BadHashError, hashtree.NotEnoughHashesError, \
IndexError) as e:
raise CorruptShareError(server, reader.shnum,
"block hash tree failure: %s" % e)
if self._version == MDMF_VERSION:
blockhash = hashutil.block_hash(salt + block)
else:
blockhash = hashutil.block_hash(block)
# If this works without an error, then validation is
# successful.
try:
bht.set_hashes(leaves={segnum: blockhash})
except (hashtree.BadHashError, hashtree.NotEnoughHashesError, \
IndexError) as e:
raise CorruptShareError(server, reader.shnum,
"block hash tree failure: %s" % e)
# Reaching this point means that we know that this segment
# is correct. Now we need to check to see whether the share
# hash chain is also correct.
# SDMF wrote share hash chains that didn't contain the
# leaves, which would be produced from the block hash tree.
# So we need to validate the block hash tree first. If
# successful, then bht[0] will contain the root for the
# shnum, which will be a leaf in the share hash tree, which
# will allow us to validate the rest of the tree.
try:
self.share_hash_tree.set_hashes(hashes=sharehashes,
leaves={reader.shnum: bht[0]})
except (hashtree.BadHashError, hashtree.NotEnoughHashesError, \
IndexError) as e:
raise CorruptShareError(server, reader.shnum,
"corrupt hashes: %s" % e)
self.log('share %d is valid for segment %d' % (reader.shnum, segnum))
return {reader.shnum: (block, salt)}
