From: Brian Warner Date: Tue, 6 Nov 2007 22:04:46 +0000 (-0700) Subject: mutable: move IV into signed prefix, add more retrieval code X-Git-Url: https://git.rkrishnan.org/components/%22news.html//%22?a=commitdiff_plain;h=2ed394e471165eb688457b15342e430a8dad0e20;p=tahoe-lafs%2Ftahoe-lafs.git mutable: move IV into signed prefix, add more retrieval code --- diff --git a/docs/mutable.txt b/docs/mutable.txt index f1cc6c28..2d64d60d 100644 --- a/docs/mutable.txt +++ b/docs/mutable.txt @@ -378,27 +378,26 @@ offset is used both to terminate the share data and to begin the encprivkey). 1 0 1 version byte, \x00 for this format 2 1 8 sequence number. 2^64-1 must be handled specially, TBD 3 9 32 "R" (root of share hash Merkle tree) - 4 41 18 encoding parameters: - 41 1 k - 42 1 N - 43 8 segment size - 51 8 data length (of original plaintext) - 5 59 36 offset table: - 59 4 (7) signature - 63 4 (8) share hash chain - 67 4 (9) block hash tree - 71 4 (10) IV - 75 4 (11) share data - 79 8 (12) encrypted private key - 87 8 (13) EOF - 6 95 256 verification key (2048 RSA key 'n' value, e=3) - 7 361 256 signature= RSAenc(sig-key, H(version+seqnum+r+encparm)) - 8 607 (a) share hash chain, encoded as: + 4 41 16 IV (share data is AES(H(readkey+IV)) ) + 5 57 18 encoding parameters: + 57 1 k + 58 1 N + 59 8 segment size + 67 8 data length (of original plaintext) + 6 75 36 offset table: + 75 4 (8) signature + 79 4 (9) share hash chain + 83 4 (10) block hash tree + 91 4 (11) share data + 95 8 (12) encrypted private key + 103 8 (13) EOF + 7 111 256 verification key (2048 RSA key 'n' value, e=3) + 8 367 256 signature=RSAenc(sigkey, H(version+seqnum+r+IV+encparm)) + 9 623 (a) share hash chain, encoded as: "".join([pack(">H32s", shnum, hash) for (shnum,hash) in needed_hashes]) - 9 ?? (b) block hash tree, encoded as: +10 ?? (b) block hash tree, encoded as: "".join([pack(">32s",hash) for hash in block_hash_tree]) -10 ?? 16 IV (share data is AES(H(readkey+IV)) ) 11 ?? LEN share data (no gap between this and encprivkey) 12 ?? 256 encrypted private key= AESenc(write-key, RSA 'd' value) 13 ?? -- EOF diff --git a/src/allmydata/mutable.py b/src/allmydata/mutable.py index a1f48a3d..e2bd556a 100644 --- a/src/allmydata/mutable.py +++ b/src/allmydata/mutable.py @@ -34,25 +34,27 @@ class CorruptShareError(Exception): self.shnum, self.reason) -HEADER_LENGTH = struct.calcsize(">BQ32s BBQQ LLLLLQQ") +PREFIX = ">BQ32s16s" # each version has a different prefix +SIGNED_PREFIX = ">BQ32s16s BBQQ" # this is covered by the signature +HEADER = ">BQ32s16s BBQQ LLLLQQ" # includes offsets +HEADER_LENGTH = struct.calcsize(HEADER) def unpack_prefix_and_signature(data): assert len(data) >= HEADER_LENGTH o = {} - prefix = data[:struct.calcsize(">BQ32s BBQQ")] + prefix = data[:struct.calcsize(SIGNED_PREFIX)] (version, seqnum, root_hash, + IV, k, N, segsize, datalen, o['signature'], o['share_hash_chain'], o['block_hash_tree'], - o['IV'], o['share_data'], o['enc_privkey'], - o['EOF']) = struct.unpack(">BQ32s BBQQ LLLLLQQ", - data[:HEADER_LENGTH]) + o['EOF']) = struct.unpack(HEADER, data[:HEADER_LENGTH]) assert version == 0 if len(data) < o['share_hash_chain']: @@ -61,7 +63,7 @@ def unpack_prefix_and_signature(data): pubkey_s = data[HEADER_LENGTH:o['signature']] signature = data[o['signature']:o['share_hash_chain']] - return (seqnum, root_hash, k, N, segsize, datalen, + return (seqnum, root_hash, IV, k, N, segsize, datalen, pubkey_s, signature, prefix) def unpack_share(data): @@ -70,15 +72,14 @@ def unpack_share(data): (version, seqnum, root_hash, + IV, k, N, segsize, datalen, o['signature'], o['share_hash_chain'], o['block_hash_tree'], - o['IV'], o['share_data'], o['enc_privkey'], - o['EOF']) = struct.unpack(">BQ32s" + "BBQQ" + "LLLLLQQ", - data[:HEADER_LENGTH]) + o['EOF']) = struct.unpack(HEADER, data[:HEADER_LENGTH]) assert version == 0 if len(data) < o['EOF']: @@ -95,41 +96,41 @@ def unpack_share(data): chunk = share_hash_chain_s[i:i+hsize] (hid, h) = struct.unpack(share_hash_format, chunk) share_hash_chain.append( (hid, h) ) - block_hash_tree_s = data[o['block_hash_tree']:o['IV']] + block_hash_tree_s = data[o['block_hash_tree']:o['share_data']] assert len(block_hash_tree_s) % 32 == 0, len(block_hash_tree_s) block_hash_tree = [] for i in range(0, len(block_hash_tree_s), 32): block_hash_tree.append(block_hash_tree_s[i:i+32]) - IV = data[o['IV']:o['share_data']] share_data = data[o['share_data']:o['enc_privkey']] enc_privkey = data[o['enc_privkey']:o['EOF']] - return (seqnum, root_hash, k, N, segsize, datalen, + return (seqnum, root_hash, IV, k, N, segsize, datalen, pubkey, signature, share_hash_chain, block_hash_tree, - IV, share_data, enc_privkey) + share_data, enc_privkey) -def pack_checkstring(seqnum, root_hash): - return struct.pack(">BQ32s", +def pack_checkstring(seqnum, root_hash, IV): + return struct.pack(PREFIX, 0, # version, seqnum, - root_hash) + root_hash, + IV) def unpack_checkstring(checkstring): - cs_len = struct.calcsize(">BQ32s") - version, seqnum, root_hash = struct.unpack(">BQ32s", - checkstring[:cs_len]) + cs_len = struct.calcsize(PREFIX) + version, seqnum, root_hash, IV = struct.unpack(PREFIX, checkstring[:cs_len]) assert version == 0 # TODO: just ignore the share - return (seqnum, root_hash) + return (seqnum, root_hash, IV) -def pack_prefix(seqnum, root_hash, +def pack_prefix(seqnum, root_hash, IV, required_shares, total_shares, segment_size, data_length): - prefix = struct.pack(">BQ32s" + "BBQQ", + prefix = struct.pack(SIGNED_PREFIX, 0, # version, seqnum, root_hash, + IV, required_shares, total_shares, @@ -140,23 +141,20 @@ def pack_prefix(seqnum, root_hash, def pack_offsets(verification_key_length, signature_length, share_hash_chain_length, block_hash_tree_length, - IV_length, share_data_length, encprivkey_length): + share_data_length, encprivkey_length): post_offset = HEADER_LENGTH offsets = {} o1 = offsets['signature'] = post_offset + verification_key_length o2 = offsets['share_hash_chain'] = o1 + signature_length o3 = offsets['block_hash_tree'] = o2 + share_hash_chain_length - assert IV_length == 16 - o4 = offsets['IV'] = o3 + block_hash_tree_length - o5 = offsets['share_data'] = o4 + IV_length - o6 = offsets['enc_privkey'] = o5 + share_data_length - o7 = offsets['EOF'] = o6 + encprivkey_length + o4 = offsets['share_data'] = o3 + block_hash_tree_length + o5 = offsets['enc_privkey'] = o4 + share_data_length + o6 = offsets['EOF'] = o5 + encprivkey_length - return struct.pack(">LLLLLQQ", + return struct.pack(">LLLLQQ", offsets['signature'], offsets['share_hash_chain'], offsets['block_hash_tree'], - offsets['IV'], offsets['share_data'], offsets['enc_privkey'], offsets['EOF']) @@ -302,6 +300,10 @@ class Retrieve: # we'll grab a copy from the first peer we talk to. self._pubkey = filenode.get_pubkey() self._storage_index = filenode.get_storage_index() + self._readkey = filenode.get_readkey() + + def log(self, msg): + self._node._client.log(msg) def retrieve(self): """Retrieve the filenode's current contents. Returns a Deferred that @@ -415,6 +417,11 @@ class Retrieve: # TODO return None + def _validate_share(self, root_hash, shnum, data): + if False: + raise CorruptShareError("explanation") + pass + def _got_results(self, datavs, peerid, readsize): self._queries_outstanding.discard(peerid) self._used_peers.add(peerid) @@ -423,7 +430,7 @@ class Retrieve: for shnum,datav in datavs.items(): data = datav[0] - (seqnum, root_hash, k, N, segsize, datalength, + (seqnum, root_hash, IV, k, N, segsize, datalength, pubkey_s, signature, prefix) = unpack_prefix_and_signature(data) if not self._pubkey: @@ -434,7 +441,7 @@ class Retrieve: "pubkey doesn't match fingerprint") self._pubkey = self._deserialize_pubkey(pubkey_s) - verinfo = (seqnum, root_hash) + verinfo = (seqnum, root_hash, IV) if verinfo not in self._valid_versions: # it's a new pair. Verify the signature. valid = self._pubkey.verify(prefix, signature) @@ -480,28 +487,29 @@ class Retrieve: self._bad_peerids.add(peerid) short_sid = idlib.a2b(self.storage_index)[:6] if f.check(CorruptShareError): - self._node._client.log("WEIRD: bad share for %s: %s" % - (short_sid, f)) + self.log("WEIRD: bad share for %s: %s" % (short_sid, f)) else: - self._node._client.log("WEIRD: other error for %s: %s" % - (short_sid, f)) + self.log("WEIRD: other error for %s: %s" % (short_sid, f)) self._check_for_done() def _check_for_done(self): share_prefixes = {} versionmap = DictOfSets() - for prefix, sharemap in self._valid_versions.values(): + for verinfo, (prefix, sharemap) in self._valid_versions.items(): if len(sharemap) >= self._required_shares: # this one looks retrievable - try: - contents = self._extract_data(sharemap) - except CorruptShareError: - # log(WEIRD) - # _extract_data is responsible for removing the bad - # share, so we can just try again - return self._check_for_done() - # success! - return self._done(contents) + d = defer.maybeDeferred(self._extract_data, verinfo, sharemap) + def _problem(f): + if f.check(CorruptShareError): + # log(WEIRD) + # _extract_data is responsible for removing the bad + # share, so we can just try again + eventually(self._check_for_done) + return + return f + d.addCallbacks(self._done, _problem) + return + # we don't have enough shares yet. Should we send out more queries? if self._queries_outstanding: # there are some running, so just wait for them to come back. @@ -544,6 +552,77 @@ class Retrieve: # we've used up all the peers we're allowed to search. Failure. return self._done(failure.Failure(NotEnoughPeersError())) + def _extract_data(self, verinfo, sharemap): + # sharemap is a dict which maps shnum to [(peerid,data)..] sets. + (seqnum, root_hash, IV) = verinfo + + # first, validate each share that we haven't validated yet. We use + # self._valid_shares to remember which ones we've already checked. + + self._valid_shares = set() # set of (peerid,data) sets + shares = {} + for shnum, shareinfo in sharemap.items(): + if shareinfo not in self._valid_shares: + (peerid,data) = shareinfo + try: + # The (seqnum+root_hash+IV) tuple for this share was + # already verified: specifically, all shares in the + # sharemap have a (seqnum+root_hash+IV) pair that was + # present in a validly signed prefix. The remainder of + # the prefix for this particular share has *not* been + # validated, but we don't care since we don't use it. + # self._validate_share() is required to check the hashes + # on the share data (and hash chains) to make sure they + # match root_hash, but is not required (and is in fact + # prohibited, because we don't validate the prefix on all + # shares) from using anything else in the share. + sharedata = self._validate_share(root_hash, shnum, data) + except CorruptShareError, e: + self.log("WEIRD: share was corrupt: %s" % e) + sharemap[shnum].discard(shareinfo) + # If there are enough remaining shares, _check_for_done() + # will try again + raise + self._valid_shares.add(shareinfo) + shares[shnum] = sharedata + # at this point, all shares in the sharemap are valid, and they're + # all for the same seqnum+root_hash version, so it's now down to + # doing FEC and decrypt. + d = defer.maybeDeferred(self._decode, shares) + d.addCallback(self._decrypt, IV) + return d + + def _decode(self, shares_dict): + # shares_dict is a dict mapping shnum to share data, but the codec + # wants two lists. + shareids = []; shares = [] + for shareid, share in shares_dict.items(): + shareids.append(shareid) + shares.append(share) + + fec = codec.CRSDecoder() + # we ought to know these values by now + assert self._segsize is not None + assert self._required_shares is not None + assert self._total_shares is not None + params = "%d-%d-%d" % (self._segsize, + self._required_shares, self._total_shares) + fec.set_serialized_params(params) + + d = fec.decode(shares, shareids) + def _done(buffers): + segment = "".join(buffers) + segment = segment[:self._datalength] + return segment + d.addCallback(_done) + return d + + def _decrypt(self, crypttext, IV): + key = hashutil.ssk_readkey_data_hash(IV, self._readkey) + decryptor = AES.new(key=key, mode=AES.MODE_CTR, counterstart="\x00"*16) + plaintext = decryptor.decrypt(crypttext) + return plaintext + def _done(self, contents): self._running = False eventually(self._done_deferred.callback, contents) @@ -588,21 +667,22 @@ class Publish: encprivkey = self._node.get_encprivkey() pubkey = self._node.get_pubkey() + IV = os.urandom(16) + d = defer.succeed(newdata) - d.addCallback(self._encrypt_and_encode, readkey, + d.addCallback(self._encrypt_and_encode, readkey, IV, required_shares, total_shares) d.addCallback(self._generate_shares, old_seqnum+1, privkey, encprivkey, pubkey) d.addCallback(self._query_peers, total_shares) - d.addCallback(self._send_shares) + d.addCallback(self._send_shares, IV) d.addCallback(self._maybe_recover) d.addCallback(lambda res: None) return d - def _encrypt_and_encode(self, newdata, readkey, + def _encrypt_and_encode(self, newdata, readkey, IV, required_shares, total_shares): - IV = os.urandom(16) key = hashutil.ssk_readkey_data_hash(IV, readkey) enc = AES.new(key=key, mode=AES.MODE_CTR, counterstart="\x00"*16) crypttext = enc.encrypt(newdata) @@ -666,7 +746,7 @@ class Publish: root_hash = share_hash_tree[0] assert len(root_hash) == 32 - prefix = pack_prefix(seqnum, root_hash, + prefix = pack_prefix(seqnum, root_hash, IV, required_shares, total_shares, segment_size, data_length) @@ -694,7 +774,6 @@ class Publish: len(signature), len(share_hash_chain_s), len(block_hash_tree_s), - len(IV), len(share_data), len(encprivkey)) @@ -704,7 +783,6 @@ class Publish: signature, share_hash_chain_s, block_hash_tree_s, - IV, share_data, encprivkey]) return (seqnum, root_hash, final_shares) @@ -812,7 +890,7 @@ class Publish: return (target_map, peer_storage_servers) - def _send_shares(self, (target_map, peer_storage_servers) ): + def _send_shares(self, (target_map, peer_storage_servers), IV ): # we're finally ready to send out our shares. If we encounter any # surprises here, it's because somebody else is writing at the same # time. (Note: in the future, when we remove the _query_peers() step @@ -821,7 +899,7 @@ class Publish: # and we'll need to respond to them more gracefully. my_checkstring = pack_checkstring(self._new_seqnum, - self._new_root_hash) + self._new_root_hash, IV) peer_messages = {} expected_old_shares = {} @@ -884,14 +962,14 @@ class Publish: surprised = True for shnum, (old_cs,) in read_data.items(): - old_seqnum, old_root_hash = unpack_checkstring(old_cs) + (old_seqnum, old_root_hash, IV) = unpack_checkstring(old_cs) if wrote and shnum in tw_vectors: - current_cs = my_checkstring + cur_cs = my_checkstring else: - current_cs = old_cs + cur_cs = old_cs - current_seqnum, current_root_hash = unpack_checkstring(current_cs) - dispatch_map.add(shnum, (peerid, current_seqnum, current_root_hash)) + (cur_seqnum, cur_root_hash, IV) = unpack_checkstring(cur_cs) + dispatch_map.add(shnum, (peerid, cur_seqnum, cur_root_hash)) if shnum not in expected_old_shares: # surprise! there was a share we didn't know about diff --git a/src/allmydata/test/test_mutable.py b/src/allmydata/test/test_mutable.py index ea5bb411..4176b813 100644 --- a/src/allmydata/test/test_mutable.py +++ b/src/allmydata/test/test_mutable.py @@ -167,7 +167,7 @@ class Publish(unittest.TestCase): fn.create(CONTENTS) p = mutable.Publish(fn) d = defer.maybeDeferred(p._encrypt_and_encode, - CONTENTS, "READKEY", 3, 10) + CONTENTS, "READKEY", "IV"*8, 3, 10) def _done( ((shares, share_ids), required_shares, total_shares, segsize, data_length, IV) ): @@ -212,12 +212,12 @@ class Publish(unittest.TestCase): self.failUnlessEqual(sorted(final_shares.keys()), range(10)) for i,sh in final_shares.items(): self.failUnless(isinstance(sh, str)) - self.failUnlessEqual(len(sh), 369) + self.failUnlessEqual(len(sh), 381) # feed the share through the unpacker as a sanity-check pieces = mutable.unpack_share(sh) - (u_seqnum, u_root_hash, k, N, segsize, datalen, + (u_seqnum, u_root_hash, IV, k, N, segsize, datalen, pubkey, signature, share_hash_chain, block_hash_tree, - IV, share_data, enc_privkey) = pieces + share_data, enc_privkey) = pieces self.failUnlessEqual(u_seqnum, 3) self.failUnlessEqual(u_root_hash, root_hash) self.failUnlessEqual(k, 3) @@ -225,7 +225,8 @@ class Publish(unittest.TestCase): self.failUnlessEqual(segsize, 21) self.failUnlessEqual(datalen, len(CONTENTS)) self.failUnlessEqual(pubkey, FakePubKey(0).serialize()) - sig_material = struct.pack(">BQ32s BBQQ", 0, seqnum, root_hash, + sig_material = struct.pack(">BQ32s16s BBQQ", + 0, seqnum, root_hash, IV, k, N, segsize, datalen) self.failUnlessEqual(signature, FakePrivKey(0).sign(sig_material)) @@ -355,7 +356,8 @@ class Publish(unittest.TestCase): total_shares = 10 d, p = self.setup_for_write(20, total_shares) d.addCallback(p._query_peers, total_shares) - d.addCallback(p._send_shares) + IV = "IV"*8 + d.addCallback(p._send_shares, IV) def _done((surprised, dispatch_map)): self.failIf(surprised, "surprised!") d.addCallback(_done)