src/allmydata/mutable/retrieve.py

   1
   2 import time
   3 from itertools import count
   4 from zope.interface import implements
   5 from twisted.internet import defer
   6 from twisted.python import failure
   7 from twisted.internet.interfaces import IPushProducer, IConsumer
   8 from foolscap.api import eventually, fireEventually
   9 from allmydata.interfaces import IRetrieveStatus, NotEnoughSharesError, \
  10                                  MDMF_VERSION, SDMF_VERSION
  11 from allmydata.util import hashutil, log, mathutil
  12 from allmydata.util.dictutil import DictOfSets
  13 from allmydata import hashtree, codec
  14 from allmydata.storage.server import si_b2a
  15 from pycryptopp.cipher.aes import AES
  16 from pycryptopp.publickey import rsa
  17
  18 from allmydata.mutable.common import CorruptShareError, UncoordinatedWriteError
  19 from allmydata.mutable.layout import MDMFSlotReadProxy
  20
  21 class RetrieveStatus:
  22     implements(IRetrieveStatus)
  23     statusid_counter = count(0)
  24     def __init__(self):
  25         self.timings = {}
  26         self.timings["fetch_per_server"] = {}
  27         self.timings["decode"] = 0.0
  28         self.timings["decrypt"] = 0.0
  29         self.timings["cumulative_verify"] = 0.0
  30         self.problems = {}
  31         self.active = True
  32         self.storage_index = None
  33         self.helper = False
  34         self.encoding = ("?","?")
  35         self.size = None
  36         self.status = "Not started"
  37         self.progress = 0.0
  38         self.counter = self.statusid_counter.next()
  39         self.started = time.time()
  40
  41     def get_started(self):
  42         return self.started
  43     def get_storage_index(self):
  44         return self.storage_index
  45     def get_encoding(self):
  46         return self.encoding
  47     def using_helper(self):
  48         return self.helper
  49     def get_size(self):
  50         return self.size
  51     def get_status(self):
  52         return self.status
  53     def get_progress(self):
  54         return self.progress
  55     def get_active(self):
  56         return self.active
  57     def get_counter(self):
  58         return self.counter
  59
  60     def add_fetch_timing(self, peerid, elapsed):
  61         if peerid not in self.timings["fetch_per_server"]:
  62             self.timings["fetch_per_server"][peerid] = []
  63         self.timings["fetch_per_server"][peerid].append(elapsed)
  64     def accumulate_decode_time(self, elapsed):
  65         self.timings["decode"] += elapsed
  66     def accumulate_decrypt_time(self, elapsed):
  67         self.timings["decrypt"] += elapsed
  68     def set_storage_index(self, si):
  69         self.storage_index = si
  70     def set_helper(self, helper):
  71         self.helper = helper
  72     def set_encoding(self, k, n):
  73         self.encoding = (k, n)
  74     def set_size(self, size):
  75         self.size = size
  76     def set_status(self, status):
  77         self.status = status
  78     def set_progress(self, value):
  79         self.progress = value
  80     def set_active(self, value):
  81         self.active = value
  82
  83 class Marker:
  84     pass
  85
  86 class Retrieve:
  87     # this class is currently single-use. Eventually (in MDMF) we will make
  88     # it multi-use, in which case you can call download(range) multiple
  89     # times, and each will have a separate response chain. However the
  90     # Retrieve object will remain tied to a specific version of the file, and
  91     # will use a single ServerMap instance.
  92     implements(IPushProducer)
  93
  94     def __init__(self, filenode, servermap, verinfo, fetch_privkey=False,
  95                  verify=False):
  96         self._node = filenode
  97         assert self._node.get_pubkey()
  98         self._storage_index = filenode.get_storage_index()
  99         assert self._node.get_readkey()
 100         self._last_failure = None
 101         prefix = si_b2a(self._storage_index)[:5]
 102         self._log_number = log.msg("Retrieve(%s): starting" % prefix)
 103         self._outstanding_queries = {} # maps (peerid,shnum) to start_time
 104         self._running = True
 105         self._decoding = False
 106         self._bad_shares = set()
 107
 108         self.servermap = servermap
 109         assert self._node.get_pubkey()
 110         self.verinfo = verinfo
 111         # during repair, we may be called upon to grab the private key, since
 112         # it wasn't picked up during a verify=False checker run, and we'll
 113         # need it for repair to generate a new version.
 114         self._need_privkey = verify or (fetch_privkey
 115                                         and not self._node.get_privkey())
 116
 117         if self._need_privkey:
 118             # TODO: Evaluate the need for this. We'll use it if we want
 119             # to limit how many queries are on the wire for the privkey
 120             # at once.
 121             self._privkey_query_markers = [] # one Marker for each time we've
 122                                              # tried to get the privkey.
 123
 124         # verify means that we are using the downloader logic to verify all
 125         # of our shares. This tells the downloader a few things.
 126         #
 127         # 1. We need to download all of the shares.
 128         # 2. We don't need to decode or decrypt the shares, since our
 129         #    caller doesn't care about the plaintext, only the
 130         #    information about which shares are or are not valid.
 131         # 3. When we are validating readers, we need to validate the
 132         #    signature on the prefix. Do we? We already do this in the
 133         #    servermap update?
 134         self._verify = verify
 135
 136         self._status = RetrieveStatus()
 137         self._status.set_storage_index(self._storage_index)
 138         self._status.set_helper(False)
 139         self._status.set_progress(0.0)
 140         self._status.set_active(True)
 141         (seqnum, root_hash, IV, segsize, datalength, k, N, prefix,
 142          offsets_tuple) = self.verinfo
 143         self._status.set_size(datalength)
 144         self._status.set_encoding(k, N)
 145         self.readers = {}
 146         self._pause_deferred = None
 147         self._offset = None
 148         self._read_length = None
 149         self.log("got seqnum %d" % self.verinfo[0])
 150
 151
 152     def get_status(self):
 153         return self._status
 154
 155     def log(self, *args, **kwargs):
 156         if "parent" not in kwargs:
 157             kwargs["parent"] = self._log_number
 158         if "facility" not in kwargs:
 159             kwargs["facility"] = "tahoe.mutable.retrieve"
 160         return log.msg(*args, **kwargs)
 161
 162     def _set_current_status(self, state):
 163         seg = "%d/%d" % (self._current_segment, self._last_segment)
 164         self._status.set_status("segment %s (%s)" % (seg, state))
 165
 166     ###################
 167     # IPushProducer
 168
 169     def pauseProducing(self):
 170         """
 171         I am called by my download target if we have produced too much
 172         data for it to handle. I make the downloader stop producing new
 173         data until my resumeProducing method is called.
 174         """
 175         if self._pause_deferred is not None:
 176             return
 177
 178         # fired when the download is unpaused.
 179         self._old_status = self._status.get_status()
 180         self._set_current_status("paused")
 181
 182         self._pause_deferred = defer.Deferred()
 183
 184
 185     def resumeProducing(self):
 186         """
 187         I am called by my download target once it is ready to begin
 188         receiving data again.
 189         """
 190         if self._pause_deferred is None:
 191             return
 192
 193         p = self._pause_deferred
 194         self._pause_deferred = None
 195         self._status.set_status(self._old_status)
 196
 197         eventually(p.callback, None)
 198
 199
 200     def _check_for_paused(self, res):
 201         """
 202         I am called just before a write to the consumer. I return a
 203         Deferred that eventually fires with the data that is to be
 204         written to the consumer. If the download has not been paused,
 205         the Deferred fires immediately. Otherwise, the Deferred fires
 206         when the downloader is unpaused.
 207         """
 208         if self._pause_deferred is not None:
 209             d = defer.Deferred()
 210             self._pause_deferred.addCallback(lambda ignored: d.callback(res))
 211             return d
 212         return defer.succeed(res)
 213
 214
 215     def download(self, consumer=None, offset=0, size=None):
 216         assert IConsumer.providedBy(consumer) or self._verify
 217
 218         if consumer:
 219             self._consumer = consumer
 220             # we provide IPushProducer, so streaming=True, per
 221             # IConsumer.
 222             self._consumer.registerProducer(self, streaming=True)
 223
 224         self._done_deferred = defer.Deferred()
 225         self._offset = offset
 226         self._read_length = size
 227         self._setup_download()
 228         self._setup_encoding_parameters()
 229         self.log("starting download")
 230         self._started_fetching = time.time()
 231         d = self._add_active_peers()
 232         # ...
 233         # The download process beyond this is a state machine.
 234         # _add_active_peers will select the peers that we want to use
 235         # for the download, and then attempt to start downloading. After
 236         # each segment, it will check for doneness, reacting to broken
 237         # peers and corrupt shares as necessary. If it runs out of good
 238         # peers before downloading all of the segments, _done_deferred
 239         # will errback.  Otherwise, it will eventually callback with the
 240         # contents of the mutable file.
 241         return self._done_deferred
 242
 243     def _setup_download(self):
 244         self._started = time.time()
 245         self._status.set_status("Retrieving Shares")
 246
 247         # how many shares do we need?
 248         (seqnum,
 249          root_hash,
 250          IV,
 251          segsize,
 252          datalength,
 253          k,
 254          N,
 255          prefix,
 256          offsets_tuple) = self.verinfo
 257
 258         # first, which servers can we use?
 259         versionmap = self.servermap.make_versionmap()
 260         shares = versionmap[self.verinfo]
 261         # this sharemap is consumed as we decide to send requests
 262         self.remaining_sharemap = DictOfSets()
 263         for (shnum, peerid, timestamp) in shares:
 264             self.remaining_sharemap.add(shnum, peerid)
 265             # If the servermap update fetched anything, it fetched at least 1
 266             # KiB, so we ask for that much.
 267             # TODO: Change the cache methods to allow us to fetch all of the
 268             # data that they have, then change this method to do that.
 269             any_cache = self._node._read_from_cache(self.verinfo, shnum,
 270                                                     0, 1000)
 271             ss = self.servermap.connections[peerid]
 272             reader = MDMFSlotReadProxy(ss,
 273                                        self._storage_index,
 274                                        shnum,
 275                                        any_cache)
 276             reader.peerid = peerid
 277             self.readers[shnum] = reader
 278         assert len(self.remaining_sharemap) >= k
 279
 280         self.shares = {} # maps shnum to validated blocks
 281         self._active_readers = [] # list of active readers for this dl.
 282         self._validated_readers = set() # set of readers that we have
 283                                         # validated the prefix of
 284         self._block_hash_trees = {} # shnum => hashtree
 285
 286         # We need one share hash tree for the entire file; its leaves
 287         # are the roots of the block hash trees for the shares that
 288         # comprise it, and its root is in the verinfo.
 289         self.share_hash_tree = hashtree.IncompleteHashTree(N)
 290         self.share_hash_tree.set_hashes({0: root_hash})
 291
 292     def decode(self, blocks_and_salts, segnum):
 293         """
 294         I am a helper method that the mutable file update process uses
 295         as a shortcut to decode and decrypt the segments that it needs
 296         to fetch in order to perform a file update. I take in a
 297         collection of blocks and salts, and pick some of those to make a
 298         segment with. I return the plaintext associated with that
 299         segment.
 300         """
 301         # shnum => block hash tree. Unused, but setup_encoding_parameters will
 302         # want to set this.
 303         self._block_hash_trees = None
 304         self._setup_encoding_parameters()
 305
 306         # This is the form expected by decode.
 307         blocks_and_salts = blocks_and_salts.items()
 308         blocks_and_salts = [(True, [d]) for d in blocks_and_salts]
 309
 310         d = self._decode_blocks(blocks_and_salts, segnum)
 311         d.addCallback(self._decrypt_segment)
 312         return d
 313
 314
 315     def _setup_encoding_parameters(self):
 316         """
 317         I set up the encoding parameters, including k, n, the number
 318         of segments associated with this file, and the segment decoders.
 319         """
 320         (seqnum,
 321          root_hash,
 322          IV,
 323          segsize,
 324          datalength,
 325          k,
 326          n,
 327          known_prefix,
 328          offsets_tuple) = self.verinfo
 329         self._required_shares = k
 330         self._total_shares = n
 331         self._segment_size = segsize
 332         self._data_length = datalength
 333
 334         if not IV:
 335             self._version = MDMF_VERSION
 336         else:
 337             self._version = SDMF_VERSION
 338
 339         if datalength and segsize:
 340             self._num_segments = mathutil.div_ceil(datalength, segsize)
 341             self._tail_data_size = datalength % segsize
 342         else:
 343             self._num_segments = 0
 344             self._tail_data_size = 0
 345
 346         self._segment_decoder = codec.CRSDecoder()
 347         self._segment_decoder.set_params(segsize, k, n)
 348
 349         if  not self._tail_data_size:
 350             self._tail_data_size = segsize
 351
 352         self._tail_segment_size = mathutil.next_multiple(self._tail_data_size,
 353                                                          self._required_shares)
 354         if self._tail_segment_size == self._segment_size:
 355             self._tail_decoder = self._segment_decoder
 356         else:
 357             self._tail_decoder = codec.CRSDecoder()
 358             self._tail_decoder.set_params(self._tail_segment_size,
 359                                           self._required_shares,
 360                                           self._total_shares)
 361
 362         self.log("got encoding parameters: "
 363                  "k: %d "
 364                  "n: %d "
 365                  "%d segments of %d bytes each (%d byte tail segment)" % \
 366                  (k, n, self._num_segments, self._segment_size,
 367                   self._tail_segment_size))
 368
 369         if self._block_hash_trees is not None:
 370             for i in xrange(self._total_shares):
 371                 # So we don't have to do this later.
 372                 self._block_hash_trees[i] = hashtree.IncompleteHashTree(self._num_segments)
 373
 374         # Our last task is to tell the downloader where to start and
 375         # where to stop. We use three parameters for that:
 376         #   - self._start_segment: the segment that we need to start
 377         #     downloading from.
 378         #   - self._current_segment: the next segment that we need to
 379         #     download.
 380         #   - self._last_segment: The last segment that we were asked to
 381         #     download.
 382         #
 383         #  We say that the download is complete when
 384         #  self._current_segment > self._last_segment. We use
 385         #  self._start_segment and self._last_segment to know when to
 386         #  strip things off of segments, and how much to strip.
 387         if self._offset:
 388             self.log("got offset: %d" % self._offset)
 389             # our start segment is the first segment containing the
 390             # offset we were given.
 391             start = self._offset // self._segment_size
 392
 393             assert start < self._num_segments
 394             self._start_segment = start
 395             self.log("got start segment: %d" % self._start_segment)
 396         else:
 397             self._start_segment = 0
 398
 399
 400         # If self._read_length is None, then we want to read the whole
 401         # file. Otherwise, we want to read only part of the file, and
 402         # need to figure out where to stop reading.
 403         if self._read_length is not None:
 404             # our end segment is the last segment containing part of the
 405             # segment that we were asked to read.
 406             self.log("got read length %d" % self._read_length)
 407             if self._read_length != 0:
 408                 end_data = self._offset + self._read_length
 409
 410                 # We don't actually need to read the byte at end_data,
 411                 # but the one before it.
 412                 end = (end_data - 1) // self._segment_size
 413
 414                 assert end < self._num_segments
 415                 self._last_segment = end
 416             else:
 417                 self._last_segment = self._start_segment
 418             self.log("got end segment: %d" % self._last_segment)
 419         else:
 420             self._last_segment = self._num_segments - 1
 421
 422         self._current_segment = self._start_segment
 423
 424     def _add_active_peers(self):
 425         """
 426         I populate self._active_readers with enough active readers to
 427         retrieve the contents of this mutable file. I am called before
 428         downloading starts, and (eventually) after each validation
 429         error, connection error, or other problem in the download.
 430         """
 431         # TODO: It would be cool to investigate other heuristics for
 432         # reader selection. For instance, the cost (in time the user
 433         # spends waiting for their file) of selecting a really slow peer
 434         # that happens to have a primary share is probably more than
 435         # selecting a really fast peer that doesn't have a primary
 436         # share. Maybe the servermap could be extended to provide this
 437         # information; it could keep track of latency information while
 438         # it gathers more important data, and then this routine could
 439         # use that to select active readers.
 440         #
 441         # (these and other questions would be easier to answer with a
 442         #  robust, configurable tahoe-lafs simulator, which modeled node
 443         #  failures, differences in node speed, and other characteristics
 444         #  that we expect storage servers to have.  You could have
 445         #  presets for really stable grids (like allmydata.com),
 446         #  friendnets, make it easy to configure your own settings, and
 447         #  then simulate the effect of big changes on these use cases
 448         #  instead of just reasoning about what the effect might be. Out
 449         #  of scope for MDMF, though.)
 450
 451         # We need at least self._required_shares readers to download a
 452         # segment.
 453         if self._verify:
 454             needed = self._total_shares
 455         else:
 456             needed = self._required_shares - len(self._active_readers)
 457         # XXX: Why don't format= log messages work here?
 458         self.log("adding %d peers to the active peers list" % needed)
 459
 460         # We favor lower numbered shares, since FEC is faster with
 461         # primary shares than with other shares, and lower-numbered
 462         # shares are more likely to be primary than higher numbered
 463         # shares.
 464         active_shnums = set(sorted(self.remaining_sharemap.keys()))
 465         # We shouldn't consider adding shares that we already have; this
 466         # will cause problems later.
 467         active_shnums -= set([reader.shnum for reader in self._active_readers])
 468         active_shnums = list(active_shnums)[:needed]
 469         if len(active_shnums) < needed and not self._verify:
 470             # We don't have enough readers to retrieve the file; fail.
 471             return self._failed()
 472
 473         for shnum in active_shnums:
 474             self._active_readers.append(self.readers[shnum])
 475             self.log("added reader for share %d" % shnum)
 476         assert len(self._active_readers) >= self._required_shares
 477         # Conceptually, this is part of the _add_active_peers step. It
 478         # validates the prefixes of newly added readers to make sure
 479         # that they match what we are expecting for self.verinfo. If
 480         # validation is successful, _validate_active_prefixes will call
 481         # _download_current_segment for us. If validation is
 482         # unsuccessful, then _validate_prefixes will remove the peer and
 483         # call _add_active_peers again, where we will attempt to rectify
 484         # the problem by choosing another peer.
 485         return self._validate_active_prefixes()
 486
 487
 488     def _validate_active_prefixes(self):
 489         """
 490         I check to make sure that the prefixes on the peers that I am
 491         currently reading from match the prefix that we want to see, as
 492         said in self.verinfo.
 493
 494         If I find that all of the active peers have acceptable prefixes,
 495         I pass control to _download_current_segment, which will use
 496         those peers to do cool things. If I find that some of the active
 497         peers have unacceptable prefixes, I will remove them from active
 498         peers (and from further consideration) and call
 499         _add_active_peers to attempt to rectify the situation. I keep
 500         track of which peers I have already validated so that I don't
 501         need to do so again.
 502         """
 503         assert self._active_readers, "No more active readers"
 504
 505         new_readers = set(self._active_readers) - self._validated_readers
 506         self.log('validating %d newly-added active readers' % len(new_readers))
 507
 508         for reader in new_readers:
 509             self._validated_readers.add(reader)
 510             # Each time we validate a reader, we check to see if we need the
 511             # private key. If we do, we politely ask for it and then continue
 512             # computing. If we find that we haven't gotten it at the end of
 513             # segment decoding, then we'll take more drastic measures.
 514             if self._need_privkey and not self._node.is_readonly():
 515                 d = reader.get_encprivkey()
 516                 d.addCallback(self._try_to_validate_privkey, reader)
 517                 # XXX: don't just drop the Deferred. We need error-reporting
 518                 # but not flow-control here.
 519         return self._download_current_segment()
 520
 521
 522     def _try_to_validate_prefix(self, prefix, reader):
 523         """
 524         I check that the prefix returned by a candidate server for
 525         retrieval matches the prefix that the servermap knows about
 526         (and, hence, the prefix that was validated earlier). If it does,
 527         I return True, which means that I approve of the use of the
 528         candidate server for segment retrieval. If it doesn't, I return
 529         False, which means that another server must be chosen.
 530         """
 531         (seqnum,
 532          root_hash,
 533          IV,
 534          segsize,
 535          datalength,
 536          k,
 537          N,
 538          known_prefix,
 539          offsets_tuple) = self.verinfo
 540         if known_prefix != prefix:
 541             self.log("prefix from share %d doesn't match" % reader.shnum)
 542             raise UncoordinatedWriteError("Mismatched prefix -- this could "
 543                                           "indicate an uncoordinated write")
 544         # Otherwise, we're okay -- no issues.
 545
 546
 547     def _remove_reader(self, reader):
 548         """
 549         At various points, we will wish to remove a peer from
 550         consideration and/or use. These include, but are not necessarily
 551         limited to:
 552
 553             - A connection error.
 554             - A mismatched prefix (that is, a prefix that does not match
 555               our conception of the version information string).
 556             - A failing block hash, salt hash, or share hash, which can
 557               indicate disk failure/bit flips, or network trouble.
 558
 559         This method will do that. I will make sure that the
 560         (shnum,reader) combination represented by my reader argument is
 561         not used for anything else during this download. I will not
 562         advise the reader of any corruption, something that my callers
 563         may wish to do on their own.
 564         """
 565         # TODO: When you're done writing this, see if this is ever
 566         # actually used for something that _mark_bad_share isn't. I have
 567         # a feeling that they will be used for very similar things, and
 568         # that having them both here is just going to be an epic amount
 569         # of code duplication.
 570         #
 571         # (well, okay, not epic, but meaningful)
 572         self.log("removing reader %s" % reader)
 573         # Remove the reader from _active_readers
 574         self._active_readers.remove(reader)
 575         # TODO: self.readers.remove(reader)?
 576         for shnum in list(self.remaining_sharemap.keys()):
 577             self.remaining_sharemap.discard(shnum, reader.peerid)
 578
 579
 580     def _mark_bad_share(self, reader, f):
 581         """
 582         I mark the (peerid, shnum) encapsulated by my reader argument as
 583         a bad share, which means that it will not be used anywhere else.
 584
 585         There are several reasons to want to mark something as a bad
 586         share. These include:
 587
 588             - A connection error to the peer.
 589             - A mismatched prefix (that is, a prefix that does not match
 590               our local conception of the version information string).
 591             - A failing block hash, salt hash, share hash, or other
 592               integrity check.
 593
 594         This method will ensure that readers that we wish to mark bad
 595         (for these reasons or other reasons) are not used for the rest
 596         of the download. Additionally, it will attempt to tell the
 597         remote peer (with no guarantee of success) that its share is
 598         corrupt.
 599         """
 600         self.log("marking share %d on server %s as bad" % \
 601                  (reader.shnum, reader))
 602         prefix = self.verinfo[-2]
 603         self.servermap.mark_bad_share(reader.peerid,
 604                                       reader.shnum,
 605                                       prefix)
 606         self._remove_reader(reader)
 607         self._bad_shares.add((reader.peerid, reader.shnum, f))
 608         self._status.problems[reader.peerid] = f
 609         self._last_failure = f
 610         self.notify_server_corruption(reader.peerid, reader.shnum,
 611                                       str(f.value))
 612
 613
 614     def _download_current_segment(self):
 615         """
 616         I download, validate, decode, decrypt, and assemble the segment
 617         that this Retrieve is currently responsible for downloading.
 618         """
 619         assert len(self._active_readers) >= self._required_shares
 620         if self._current_segment <= self._last_segment:
 621             d = self._process_segment(self._current_segment)
 622         else:
 623             d = defer.succeed(None)
 624         d.addBoth(self._turn_barrier)
 625         d.addCallback(self._check_for_done)
 626         return d
 627
 628
 629     def _turn_barrier(self, result):
 630         """
 631         I help the download process avoid the recursion limit issues
 632         discussed in #237.
 633         """
 634         return fireEventually(result)
 635
 636
 637     def _process_segment(self, segnum):
 638         """
 639         I download, validate, decode, and decrypt one segment of the
 640         file that this Retrieve is retrieving. This means coordinating
 641         the process of getting k blocks of that file, validating them,
 642         assembling them into one segment with the decoder, and then
 643         decrypting them.
 644         """
 645         self.log("processing segment %d" % segnum)
 646
 647         # TODO: The old code uses a marker. Should this code do that
 648         # too? What did the Marker do?
 649         assert len(self._active_readers) >= self._required_shares
 650
 651         # We need to ask each of our active readers for its block and
 652         # salt. We will then validate those. If validation is
 653         # successful, we will assemble the results into plaintext.
 654         ds = []
 655         for reader in self._active_readers:
 656             started = time.time()
 657             d = reader.get_block_and_salt(segnum)
 658             d2 = self._get_needed_hashes(reader, segnum)
 659             dl = defer.DeferredList([d, d2], consumeErrors=True)
 660             dl.addCallback(self._validate_block, segnum, reader, started)
 661             dl.addErrback(self._validation_or_decoding_failed, [reader])
 662             ds.append(dl)
 663         dl = defer.DeferredList(ds)
 664         if self._verify:
 665             dl.addCallback(lambda ignored: "")
 666             dl.addCallback(self._set_segment)
 667         else:
 668             dl.addCallback(self._maybe_decode_and_decrypt_segment, segnum)
 669         return dl
 670
 671
 672     def _maybe_decode_and_decrypt_segment(self, blocks_and_salts, segnum):
 673         """
 674         I take the results of fetching and validating the blocks from a
 675         callback chain in another method. If the results are such that
 676         they tell me that validation and fetching succeeded without
 677         incident, I will proceed with decoding and decryption.
 678         Otherwise, I will do nothing.
 679         """
 680         self.log("trying to decode and decrypt segment %d" % segnum)
 681         failures = False
 682         for block_and_salt in blocks_and_salts:
 683             if not block_and_salt[0] or block_and_salt[1] == None:
 684                 self.log("some validation operations failed; not proceeding")
 685                 failures = True
 686                 break
 687         if not failures:
 688             self.log("everything looks ok, building segment %d" % segnum)
 689             d = self._decode_blocks(blocks_and_salts, segnum)
 690             d.addCallback(self._decrypt_segment)
 691             d.addErrback(self._validation_or_decoding_failed,
 692                          self._active_readers)
 693             # check to see whether we've been paused before writing
 694             # anything.
 695             d.addCallback(self._check_for_paused)
 696             d.addCallback(self._set_segment)
 697             return d
 698         else:
 699             return defer.succeed(None)
 700
 701
 702     def _set_segment(self, segment):
 703         """
 704         Given a plaintext segment, I register that segment with the
 705         target that is handling the file download.
 706         """
 707         self.log("got plaintext for segment %d" % self._current_segment)
 708         if self._current_segment == self._start_segment:
 709             # We're on the first segment. It's possible that we want
 710             # only some part of the end of this segment, and that we
 711             # just downloaded the whole thing to get that part. If so,
 712             # we need to account for that and give the reader just the
 713             # data that they want.
 714             n = self._offset % self._segment_size
 715             self.log("stripping %d bytes off of the first segment" % n)
 716             self.log("original segment length: %d" % len(segment))
 717             segment = segment[n:]
 718             self.log("new segment length: %d" % len(segment))
 719
 720         if self._current_segment == self._last_segment and self._read_length is not None:
 721             # We're on the last segment. It's possible that we only want
 722             # part of the beginning of this segment, and that we
 723             # downloaded the whole thing anyway. Make sure to give the
 724             # caller only the portion of the segment that they want to
 725             # receive.
 726             extra = self._read_length
 727             if self._start_segment != self._last_segment:
 728                 extra -= self._segment_size - \
 729                             (self._offset % self._segment_size)
 730             extra %= self._segment_size
 731             self.log("original segment length: %d" % len(segment))
 732             segment = segment[:extra]
 733             self.log("new segment length: %d" % len(segment))
 734             self.log("only taking %d bytes of the last segment" % extra)
 735
 736         if not self._verify:
 737             self._consumer.write(segment)
 738         else:
 739             # we don't care about the plaintext if we are doing a verify.
 740             segment = None
 741         self._current_segment += 1
 742
 743
 744     def _validation_or_decoding_failed(self, f, readers):
 745         """
 746         I am called when a block or a salt fails to correctly validate, or when
 747         the decryption or decoding operation fails for some reason.  I react to
 748         this failure by notifying the remote server of corruption, and then
 749         removing the remote peer from further activity.
 750         """
 751         assert isinstance(readers, list)
 752         bad_shnums = [reader.shnum for reader in readers]
 753
 754         self.log("validation or decoding failed on share(s) %s, peer(s) %s "
 755                  ", segment %d: %s" % \
 756                  (bad_shnums, readers, self._current_segment, str(f)))
 757         for reader in readers:
 758             self._mark_bad_share(reader, f)
 759         return
 760
 761
 762     def _validate_block(self, results, segnum, reader, started):
 763         """
 764         I validate a block from one share on a remote server.
 765         """
 766         # Grab the part of the block hash tree that is necessary to
 767         # validate this block, then generate the block hash root.
 768         self.log("validating share %d for segment %d" % (reader.shnum,
 769                                                              segnum))
 770         elapsed = time.time() - started
 771         self._status.add_fetch_timing(reader.peerid, elapsed)
 772         self._set_current_status("validating blocks")
 773         # Did we fail to fetch either of the things that we were
 774         # supposed to? Fail if so.
 775         if not results[0][0] and results[1][0]:
 776             # handled by the errback handler.
 777
 778             # These all get batched into one query, so the resulting
 779             # failure should be the same for all of them, so we can just
 780             # use the first one.
 781             assert isinstance(results[0][1], failure.Failure)
 782
 783             f = results[0][1]
 784             raise CorruptShareError(reader.peerid,
 785                                     reader.shnum,
 786                                     "Connection error: %s" % str(f))
 787
 788         block_and_salt, block_and_sharehashes = results
 789         block, salt = block_and_salt[1]
 790         blockhashes, sharehashes = block_and_sharehashes[1]
 791
 792         blockhashes = dict(enumerate(blockhashes[1]))
 793         self.log("the reader gave me the following blockhashes: %s" % \
 794                  blockhashes.keys())
 795         self.log("the reader gave me the following sharehashes: %s" % \
 796                  sharehashes[1].keys())
 797         bht = self._block_hash_trees[reader.shnum]
 798
 799         if bht.needed_hashes(segnum, include_leaf=True):
 800             try:
 801                 bht.set_hashes(blockhashes)
 802             except (hashtree.BadHashError, hashtree.NotEnoughHashesError, \
 803                     IndexError), e:
 804                 raise CorruptShareError(reader.peerid,
 805                                         reader.shnum,
 806                                         "block hash tree failure: %s" % e)
 807
 808         if self._version == MDMF_VERSION:
 809             blockhash = hashutil.block_hash(salt + block)
 810         else:
 811             blockhash = hashutil.block_hash(block)
 812         # If this works without an error, then validation is
 813         # successful.
 814         try:
 815            bht.set_hashes(leaves={segnum: blockhash})
 816         except (hashtree.BadHashError, hashtree.NotEnoughHashesError, \
 817                 IndexError), e:
 818             raise CorruptShareError(reader.peerid,
 819                                     reader.shnum,
 820                                     "block hash tree failure: %s" % e)
 821
 822         # Reaching this point means that we know that this segment
 823         # is correct. Now we need to check to see whether the share
 824         # hash chain is also correct.
 825         # SDMF wrote share hash chains that didn't contain the
 826         # leaves, which would be produced from the block hash tree.
 827         # So we need to validate the block hash tree first. If
 828         # successful, then bht[0] will contain the root for the
 829         # shnum, which will be a leaf in the share hash tree, which
 830         # will allow us to validate the rest of the tree.
 831         if self.share_hash_tree.needed_hashes(reader.shnum,
 832                                               include_leaf=True) or \
 833                                               self._verify:
 834             try:
 835                 self.share_hash_tree.set_hashes(hashes=sharehashes[1],
 836                                             leaves={reader.shnum: bht[0]})
 837             except (hashtree.BadHashError, hashtree.NotEnoughHashesError, \
 838                     IndexError), e:
 839                 raise CorruptShareError(reader.peerid,
 840                                         reader.shnum,
 841                                         "corrupt hashes: %s" % e)
 842
 843         self.log('share %d is valid for segment %d' % (reader.shnum,
 844                                                        segnum))
 845         return {reader.shnum: (block, salt)}
 846
 847
 848     def _get_needed_hashes(self, reader, segnum):
 849         """
 850         I get the hashes needed to validate segnum from the reader, then return
 851         to my caller when this is done.
 852         """
 853         bht = self._block_hash_trees[reader.shnum]
 854         needed = bht.needed_hashes(segnum, include_leaf=True)
 855         # The root of the block hash tree is also a leaf in the share
 856         # hash tree. So we don't need to fetch it from the remote
 857         # server. In the case of files with one segment, this means that
 858         # we won't fetch any block hash tree from the remote server,
 859         # since the hash of each share of the file is the entire block
 860         # hash tree, and is a leaf in the share hash tree. This is fine,
 861         # since any share corruption will be detected in the share hash
 862         # tree.
 863         #needed.discard(0)
 864         self.log("getting blockhashes for segment %d, share %d: %s" % \
 865                  (segnum, reader.shnum, str(needed)))
 866         d1 = reader.get_blockhashes(needed, force_remote=True)
 867         if self.share_hash_tree.needed_hashes(reader.shnum):
 868             need = self.share_hash_tree.needed_hashes(reader.shnum)
 869             self.log("also need sharehashes for share %d: %s" % (reader.shnum,
 870                                                                  str(need)))
 871             d2 = reader.get_sharehashes(need, force_remote=True)
 872         else:
 873             d2 = defer.succeed({}) # the logic in the next method
 874                                    # expects a dict
 875         dl = defer.DeferredList([d1, d2], consumeErrors=True)
 876         return dl
 877
 878
 879     def _decode_blocks(self, blocks_and_salts, segnum):
 880         """
 881         I take a list of k blocks and salts, and decode that into a
 882         single encrypted segment.
 883         """
 884         d = {}
 885         # We want to merge our dictionaries to the form
 886         # {shnum: blocks_and_salts}
 887         #
 888         # The dictionaries come from validate block that way, so we just
 889         # need to merge them.
 890         for block_and_salt in blocks_and_salts:
 891             d.update(block_and_salt[1])
 892
 893         # All of these blocks should have the same salt; in SDMF, it is
 894         # the file-wide IV, while in MDMF it is the per-segment salt. In
 895         # either case, we just need to get one of them and use it.
 896         #
 897         # d.items()[0] is like (shnum, (block, salt))
 898         # d.items()[0][1] is like (block, salt)
 899         # d.items()[0][1][1] is the salt.
 900         salt = d.items()[0][1][1]
 901         # Next, extract just the blocks from the dict. We'll use the
 902         # salt in the next step.
 903         share_and_shareids = [(k, v[0]) for k, v in d.items()]
 904         d2 = dict(share_and_shareids)
 905         shareids = []
 906         shares = []
 907         for shareid, share in d2.items():
 908             shareids.append(shareid)
 909             shares.append(share)
 910
 911         self._set_current_status("decoding")
 912         started = time.time()
 913         assert len(shareids) >= self._required_shares, len(shareids)
 914         # zfec really doesn't want extra shares
 915         shareids = shareids[:self._required_shares]
 916         shares = shares[:self._required_shares]
 917         self.log("decoding segment %d" % segnum)
 918         if segnum == self._num_segments - 1:
 919             d = defer.maybeDeferred(self._tail_decoder.decode, shares, shareids)
 920         else:
 921             d = defer.maybeDeferred(self._segment_decoder.decode, shares, shareids)
 922         def _process(buffers):
 923             segment = "".join(buffers)
 924             self.log(format="now decoding segment %(segnum)s of %(numsegs)s",
 925                      segnum=segnum,
 926                      numsegs=self._num_segments,
 927                      level=log.NOISY)
 928             self.log(" joined length %d, datalength %d" %
 929                      (len(segment), self._data_length))
 930             if segnum == self._num_segments - 1:
 931                 size_to_use = self._tail_data_size
 932             else:
 933                 size_to_use = self._segment_size
 934             segment = segment[:size_to_use]
 935             self.log(" segment len=%d" % len(segment))
 936             self._status.accumulate_decode_time(time.time() - started)
 937             return segment, salt
 938         d.addCallback(_process)
 939         return d
 940
 941
 942     def _decrypt_segment(self, segment_and_salt):
 943         """
 944         I take a single segment and its salt, and decrypt it. I return
 945         the plaintext of the segment that is in my argument.
 946         """
 947         segment, salt = segment_and_salt
 948         self._set_current_status("decrypting")
 949         self.log("decrypting segment %d" % self._current_segment)
 950         started = time.time()
 951         key = hashutil.ssk_readkey_data_hash(salt, self._node.get_readkey())
 952         decryptor = AES(key)
 953         plaintext = decryptor.process(segment)
 954         self._status.accumulate_decrypt_time(time.time() - started)
 955         return plaintext
 956
 957
 958     def notify_server_corruption(self, peerid, shnum, reason):
 959         ss = self.servermap.connections[peerid]
 960         ss.callRemoteOnly("advise_corrupt_share",
 961                           "mutable", self._storage_index, shnum, reason)
 962
 963
 964     def _try_to_validate_privkey(self, enc_privkey, reader):
 965         alleged_privkey_s = self._node._decrypt_privkey(enc_privkey)
 966         alleged_writekey = hashutil.ssk_writekey_hash(alleged_privkey_s)
 967         if alleged_writekey != self._node.get_writekey():
 968             self.log("invalid privkey from %s shnum %d" %
 969                      (reader, reader.shnum),
 970                      level=log.WEIRD, umid="YIw4tA")
 971             if self._verify:
 972                 self.servermap.mark_bad_share(reader.peerid, reader.shnum,
 973                                               self.verinfo[-2])
 974                 e = CorruptShareError(reader.peerid,
 975                                       reader.shnum,
 976                                       "invalid privkey")
 977                 f = failure.Failure(e)
 978                 self._bad_shares.add((reader.peerid, reader.shnum, f))
 979             return
 980
 981         # it's good
 982         self.log("got valid privkey from shnum %d on reader %s" %
 983                  (reader.shnum, reader))
 984         privkey = rsa.create_signing_key_from_string(alleged_privkey_s)
 985         self._node._populate_encprivkey(enc_privkey)
 986         self._node._populate_privkey(privkey)
 987         self._need_privkey = False
 988
 989
 990     def _check_for_done(self, res):
 991         """
 992         I check to see if this Retrieve object has successfully finished
 993         its work.
 994
 995         I can exit in the following ways:
 996             - If there are no more segments to download, then I exit by
 997               causing self._done_deferred to fire with the plaintext
 998               content requested by the caller.
 999             - If there are still segments to be downloaded, and there
1000               are enough active readers (readers which have not broken
1001               and have not given us corrupt data) to continue
1002               downloading, I send control back to
1003               _download_current_segment.
1004             - If there are still segments to be downloaded but there are
1005               not enough active peers to download them, I ask
1006               _add_active_peers to add more peers. If it is successful,
1007               it will call _download_current_segment. If there are not
1008               enough peers to retrieve the file, then that will cause
1009               _done_deferred to errback.
1010         """
1011         self.log("checking for doneness")
1012         if self._current_segment > self._last_segment:
1013             # No more segments to download, we're done.
1014             self.log("got plaintext, done")
1015             return self._done()
1016
1017         if len(self._active_readers) >= self._required_shares:
1018             # More segments to download, but we have enough good peers
1019             # in self._active_readers that we can do that without issue,
1020             # so go nab the next segment.
1021             self.log("not done yet: on segment %d of %d" % \
1022                      (self._current_segment + 1, self._num_segments))
1023             return self._download_current_segment()
1024
1025         self.log("not done yet: on segment %d of %d, need to add peers" % \
1026                  (self._current_segment + 1, self._num_segments))
1027         return self._add_active_peers()
1028
1029
1030     def _done(self):
1031         """
1032         I am called by _check_for_done when the download process has
1033         finished successfully. After making some useful logging
1034         statements, I return the decrypted contents to the owner of this
1035         Retrieve object through self._done_deferred.
1036         """
1037         self._running = False
1038         self._status.set_active(False)
1039         now = time.time()
1040         self._status.timings['total'] = now - self._started
1041         self._status.timings['fetch'] = now - self._started_fetching
1042         self._status.set_status("Finished")
1043         self._status.set_progress(1.0)
1044
1045         # remember the encoding parameters, use them again next time
1046         (seqnum, root_hash, IV, segsize, datalength, k, N, prefix,
1047          offsets_tuple) = self.verinfo
1048         self._node._populate_required_shares(k)
1049         self._node._populate_total_shares(N)
1050
1051         if self._verify:
1052             ret = list(self._bad_shares)
1053             self.log("done verifying, found %d bad shares" % len(ret))
1054         else:
1055             # TODO: upload status here?
1056             ret = self._consumer
1057             self._consumer.unregisterProducer()
1058         eventually(self._done_deferred.callback, ret)
1059
1060
1061     def _failed(self):
1062         """
1063         I am called by _add_active_peers when there are not enough
1064         active peers left to complete the download. After making some
1065         useful logging statements, I return an exception to that effect
1066         to the caller of this Retrieve object through
1067         self._done_deferred.
1068         """
1069         self._running = False
1070         self._status.set_active(False)
1071         now = time.time()
1072         self._status.timings['total'] = now - self._started
1073         self._status.timings['fetch'] = now - self._started_fetching
1074         self._status.set_status("Failed")
1075
1076         if self._verify:
1077             ret = list(self._bad_shares)
1078         else:
1079             format = ("ran out of peers: "
1080                       "have %(have)d of %(total)d segments "
1081                       "found %(bad)d bad shares "
1082                       "encoding %(k)d-of-%(n)d")
1083             args = {"have": self._current_segment,
1084                     "total": self._num_segments,
1085                     "need": self._last_segment,
1086                     "k": self._required_shares,
1087                     "n": self._total_shares,
1088                     "bad": len(self._bad_shares)}
1089             e = NotEnoughSharesError("%s, last failure: %s" % \
1090                                      (format % args, str(self._last_failure)))
1091             f = failure.Failure(e)
1092             ret = f
1093         eventually(self._done_deferred.callback, ret)