From: Brian Warner Date: Thu, 8 Nov 2007 09:46:27 +0000 (-0700) Subject: mutable: grab encprivkey when necessary during publish, fix test_mutable X-Git-Tag: allmydata-tahoe-0.7.0~245 X-Git-Url: https://git.rkrishnan.org/components/%22news.html//%22?a=commitdiff_plain;h=e7ad7f879105afd0fa95de2a488d4d7d6c3484b8;p=tahoe-lafs%2Ftahoe-lafs.git mutable: grab encprivkey when necessary during publish, fix test_mutable --- diff --git a/docs/mutable.txt b/docs/mutable.txt index a67e8973..ee01d044 100644 --- a/docs/mutable.txt +++ b/docs/mutable.txt @@ -391,15 +391,15 @@ offset is used both to terminate the share data and to begin the encprivkey). 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: + 7 111 292ish verification key (2048 RSA key) + 8 367ish 256ish signature=RSAenc(sigkey, H(version+seqnum+r+IV+encparm)) + 9 623ish (a) share hash chain, encoded as: "".join([pack(">H32s", shnum, hash) for (shnum,hash) in needed_hashes]) 10 ?? (b) block hash tree, encoded as: "".join([pack(">32s",hash) for hash in block_hash_tree]) 11 ?? LEN share data (no gap between this and encprivkey) -12 ?? 256 encrypted private key= AESenc(write-key, RSA 'd' value) +12 ?? 1216ish encrypted private key= AESenc(write-key, RSA-key) 13 ?? -- EOF (a) The share hash chain contains ceil(log(N)) hashes, each 32 bytes long. diff --git a/src/allmydata/mutable.py b/src/allmydata/mutable.py index a3d93ab5..7aea078f 100644 --- a/src/allmydata/mutable.py +++ b/src/allmydata/mutable.py @@ -15,9 +15,11 @@ from pycryptopp.publickey import rsa class NeedMoreDataError(Exception): - def __init__(self, needed_bytes): + def __init__(self, needed_bytes, encprivkey_offset, encprivkey_length): Exception.__init__(self) - self.needed_bytes = needed_bytes + self.needed_bytes = needed_bytes # up through EOF + self.encprivkey_offset = encprivkey_offset + self.encprivkey_length = encprivkey_length def __str__(self): return "" % self.needed_bytes @@ -59,7 +61,8 @@ def unpack_prefix_and_signature(data): assert version == 0 if len(data) < o['share_hash_chain']: - raise NeedMoreDataError(o['share_hash_chain']) + raise NeedMoreDataError(o['share_hash_chain'], + o['enc_privkey'], o['EOF']-o['enc_privkey']) pubkey_s = data[HEADER_LENGTH:o['signature']] signature = data[o['signature']:o['share_hash_chain']] @@ -84,7 +87,8 @@ def unpack_share(data): assert version == 0 if len(data) < o['EOF']: - raise NeedMoreDataError(o['EOF']) + raise NeedMoreDataError(o['EOF'], + o['enc_privkey'], o['EOF']-o['enc_privkey']) pubkey = data[HEADER_LENGTH:o['signature']] signature = data[o['signature']:o['share_hash_chain']] @@ -593,7 +597,10 @@ class Publish: def log(self, msg): prefix = idlib.b2a(self._node.get_storage_index())[:6] - #self._node._client.log("%s: %s" % (prefix, msg)) + self._node._client.log("%s: %s" % (prefix, msg)) + + def log_err(self, f): + log.err(f) def publish(self, newdata): """Publish the filenode's current contents. Returns a Deferred that @@ -612,6 +619,10 @@ class Publish: self.log("starting publish") + self._storage_index = self._node.get_storage_index() + self._writekey = self._node.get_writekey() + assert self._writekey, "need write capability to publish" + old_roothash = self._node._current_roothash old_seqnum = self._node._current_seqnum assert old_seqnum is not None, "must read before replace" @@ -629,8 +640,18 @@ class Publish: IV = os.urandom(16) + # we read only 1KB because all we generally care about is the seqnum + # ("prefix") info, so we know which shares are where. We need to get + # the privkey from somebody, which means reading more like 3KB, but + # the code in _obtain_privkey will ensure that we manage that even if + # we need an extra roundtrip. TODO: arrange to read 3KB from one peer + # who is likely to hold a share (like, say, ourselves), so we can + # avoid the latency of that extra roundtrip. + self._read_size = 1000 + d = defer.succeed(total_shares) d.addCallback(self._query_peers) + d.addCallback(self._obtain_privkey) d.addCallback(self._encrypt_and_encode, newdata, readkey, IV, required_shares, total_shares) @@ -644,7 +665,7 @@ class Publish: def _query_peers(self, total_shares): self.log("_query_peers") - storage_index = self._node.get_storage_index() + storage_index = self._storage_index peerlist = self._node._client.get_permuted_peers(storage_index, include_myself=False) # we don't include ourselves in the N peers, but we *do* push an @@ -656,6 +677,8 @@ class Publish: current_share_peers = DictOfSets() reachable_peers = {} + # list of (peerid, offset, length) where the encprivkey might be found + self._encprivkey_shares = [] EPSILON = total_shares / 2 partial_peerlist = islice(peerlist, total_shares + EPSILON) @@ -679,13 +702,8 @@ class Publish: d = conn.callRemote("get_service", "storageserver") def _got_storageserver(ss): peer_storage_servers[peerid] = ss - # TODO: only read 2KB, since all we really need is the seqnum - # info. But we need to read more from at least one peer so we can - # grab the encrypted privkey. Really, read just the 2k, and if - # the first response suggests that the privkey is beyond that - # segment, send out another query to the same peer for the - # privkey segment. - return ss.callRemote("slot_readv", storage_index, [], [(0, 2500)]) + return ss.callRemote("slot_readv", + storage_index, [], [(0, self._read_size)]) d.addCallback(_got_storageserver) return d @@ -698,22 +716,67 @@ class Publish: for shnum, datav in datavs.items(): assert len(datav) == 1 data = datav[0] - r = unpack_share(data) + # We want (seqnum, root_hash, IV) from all servers to know what + # versions we are replacing. We want the encprivkey from one + # server (assuming it's valid) so we know our own private key, so + # we can sign our update. SMDF: read the whole share from each + # server. TODO: later we can optimize this to transfer less data. + + # we assume that we have enough data to extract the signature. + # TODO: if this raises NeedMoreDataError, arrange to do another + # read pass. + r = unpack_prefix_and_signature(data) (seqnum, root_hash, IV, k, N, segsize, datalen, - pubkey, signature, share_hash_chain, block_hash_tree, - share_data, enc_privkey) = r + pubkey_s, signature, prefix) = r + + # TODO: consider verifying the signature here. It's expensive. + # What can an attacker (in this case the server) accomplish? They + # could make us think that there's a newer version of the file + # out there, which would cause us to throw + # UncoordinatedWriteError (i.e. it's a DoS attack). share = (shnum, seqnum, root_hash) current_share_peers.add(shnum, (peerid, seqnum, root_hash) ) - if not self._encprivkey: - self._encprivkey = enc_privkey - self._node._populate_encprivkey(self._encprivkey) + if not self._privkey: - privkey_s = self._node._decrypt_privkey(enc_privkey) - self._privkey = rsa.create_signing_key_from_string(privkey_s) - self._node._populate_privkey(self._privkey) - # TODO: make sure we actually fill these in before we try to - # upload. This means we may need to re-fetch something if our - # initial read was too short. + self._try_to_extract_privkey(data, peerid, shnum) + + + def _try_to_extract_privkey(self, data, peerid, shnum): + try: + r = unpack_share(data) + except NeedMoreDataError, e: + # this share won't help us. oh well. + offset = e.encprivkey_offset + length = e.encprivkey_length + self.log("shnum %d on peerid %s: share was too short " + "to get the encprivkey, but [%d:%d] ought to hold it" % + (shnum, idlib.shortnodeid_b2a(peerid), + offset, offset+length)) + + self._encprivkey_shares.append( (peerid, shnum, offset, length) ) + return + + (seqnum, root_hash, IV, k, N, segsize, datalen, + pubkey, signature, share_hash_chain, block_hash_tree, + share_data, enc_privkey) = r + + return self._try_to_validate_privkey(enc_privkey, peerid, shnum) + + def _try_to_validate_privkey(self, enc_privkey, peerid, shnum): + alleged_privkey_s = self._node._decrypt_privkey(enc_privkey) + alleged_writekey = hashutil.ssk_writekey_hash(alleged_privkey_s) + if alleged_writekey != self._writekey: + self.log("WEIRD: invalid privkey from %s shnum %d" % + (idlib.nodeid_b2a(peerid)[:8], shnum)) + return + + # it's good + self.log("got valid privkey from shnum %d on peerid %s" % + (shnum, idlib.shortnodeid_b2a(peerid))) + self._privkey = rsa.create_signing_key_from_string(alleged_privkey_s) + self._encprivkey = enc_privkey + self._node._populate_encprivkey(self._encprivkey) + self._node._populate_privkey(self._privkey) def _got_all_query_results(self, res, total_shares, reachable_peers, @@ -762,9 +825,43 @@ class Publish: assert not shares_needing_homes - target_info = (target_map, peer_storage_servers) + target_info = (target_map, shares_per_peer, peer_storage_servers) return target_info + def _obtain_privkey(self, target_info): + # make sure we've got a copy of our private key. + if self._privkey: + # Must have picked it up during _query_peers. We're good to go. + return target_info + + # Nope, we haven't managed to grab a copy, and we still need it. Ask + # peers one at a time until we get a copy. Only bother asking peers + # who've admitted to holding a share. + + target_map, shares_per_peer, peer_storage_servers = target_info + # pull shares from self._encprivkey_shares + if not self._encprivkey_shares: + raise NotEnoughPeersError("Unable to find a copy of the privkey") + + (peerid, shnum, offset, length) = self._encprivkey_shares.pop(0) + self.log("trying to obtain privkey from %s shnum %d" % + (idlib.shortnodeid_b2a(peerid), shnum)) + d = self._do_privkey_query(peer_storage_servers[peerid], peerid, + shnum, offset, length) + d.addErrback(self.log_err) + d.addCallback(lambda res: self._obtain_privkey(target_info)) + return d + + def _do_privkey_query(self, rref, peerid, shnum, offset, length): + d = rref.callRemote("slot_readv", self._storage_index, + [shnum], [(offset, length)] ) + d.addCallback(self._privkey_query_response, peerid, shnum) + return d + + def _privkey_query_response(self, datav, peerid, shnum): + data = datav[shnum][0] + self._try_to_validate_privkey(data, peerid, shnum) + def _encrypt_and_encode(self, target_info, newdata, readkey, IV, required_shares, total_shares): @@ -893,7 +990,7 @@ class Publish: # surprises here are *not* indications of UncoordinatedWriteError, # and we'll need to respond to them more gracefully. - target_map, peer_storage_servers = target_info + target_map, shares_per_peer, peer_storage_servers = target_info my_checkstring = pack_checkstring(seqnum, root_hash, IV) peer_messages = {} @@ -950,7 +1047,7 @@ class Publish: def _got_write_answer(self, answer, tw_vectors, my_checkstring, peerid, expected_old_shares, dispatch_map): - self.log("_got_write_answer: %r" % (answer,)) + self.log("_got_write_answer from %s" % idlib.shortnodeid_b2a(peerid)) wrote, read_data = answer surprised = False diff --git a/src/allmydata/test/test_mutable.py b/src/allmydata/test/test_mutable.py index 42a01a66..f3a7abfc 100644 --- a/src/allmydata/test/test_mutable.py +++ b/src/allmydata/test/test_mutable.py @@ -2,7 +2,7 @@ import itertools, struct from twisted.trial import unittest from twisted.internet import defer -from twisted.python import failure +from twisted.python import failure, log from allmydata import mutable, uri, dirnode2 from allmydata.dirnode2 import split_netstring from allmydata.util.hashutil import netstring, tagged_hash @@ -91,6 +91,8 @@ class MyClient: self._num_peers = num_peers self._peerids = [tagged_hash("peerid", "%d" % i)[:20] for i in range(self._num_peers)] + def log(self, msg): + log.msg(msg) def get_renewal_secret(self): return "I hereby permit you to renew my files" @@ -167,11 +169,12 @@ class Publish(unittest.TestCase): CONTENTS = "some initial contents" fn.create(CONTENTS) p = mutable.Publish(fn) - d = defer.maybeDeferred(p._encrypt_and_encode, + target_info = None + d = defer.maybeDeferred(p._encrypt_and_encode, target_info, CONTENTS, "READKEY", "IV"*8, 3, 10) def _done( ((shares, share_ids), required_shares, total_shares, - segsize, data_length, IV) ): + segsize, data_length, target_info2) ): self.failUnlessEqual(len(shares), 10) for sh in shares: self.failUnless(isinstance(sh, str)) @@ -181,7 +184,7 @@ class Publish(unittest.TestCase): self.failUnlessEqual(total_shares, 10) self.failUnlessEqual(segsize, 21) self.failUnlessEqual(data_length, len(CONTENTS)) - self.failUnlessEqual(len(IV), 16) + self.failUnlessIdentical(target_info, target_info2) d.addCallback(_done) return d @@ -196,16 +199,19 @@ class Publish(unittest.TestCase): r = mutable.Retrieve(fn) # make some fake shares shares_and_ids = ( ["%07d" % i for i in range(10)], range(10) ) + target_info = None + p._privkey = FakePrivKey(0) + p._encprivkey = "encprivkey" + p._pubkey = FakePubKey(0) d = defer.maybeDeferred(p._generate_shares, (shares_and_ids, 3, 10, 21, # segsize len(CONTENTS), - "IV"*8), + target_info), 3, # seqnum - FakePrivKey(0), "encprivkey", FakePubKey(0), - ) - def _done( (seqnum, root_hash, final_shares) ): + "IV"*8) + def _done( (seqnum, root_hash, final_shares, target_info2) ): self.failUnlessEqual(seqnum, 3) self.failUnlessEqual(len(root_hash), 32) self.failUnless(isinstance(final_shares, dict)) @@ -243,6 +249,7 @@ class Publish(unittest.TestCase): self.failUnlessEqual(IV, "IV"*8) self.failUnlessEqual(len(share_data), len("%07d" % 1)) self.failUnlessEqual(enc_privkey, "encprivkey") + self.failUnlessIdentical(target_info, target_info2) d.addCallback(_done) return d @@ -254,6 +261,7 @@ class Publish(unittest.TestCase): CONTENTS = "some initial contents" fn.create(CONTENTS) p = FakePublish(fn) + p._storage_index = "\x00"*32 #r = mutable.Retrieve(fn) p._peers = {} for peerid in c._peerids: @@ -279,13 +287,10 @@ class Publish(unittest.TestCase): def test_sharemap_20newpeers(self): c, p = self.setup_for_sharemap(20) - new_seqnum = 3 - new_root_hash = "Rnew" - new_shares = None total_shares = 10 - d = p._query_peers( (new_seqnum, new_root_hash, new_seqnum), - total_shares) - def _done( (target_map, peer_storage_servers) ): + d = p._query_peers(total_shares) + def _done(target_info): + (target_map, shares_per_peer, peer_storage_servers) = target_info shares_per_peer = {} for shnum in target_map: for (peerid, old_seqnum, old_R) in target_map[shnum]: @@ -304,13 +309,10 @@ class Publish(unittest.TestCase): def test_sharemap_3newpeers(self): c, p = self.setup_for_sharemap(3) - new_seqnum = 3 - new_root_hash = "Rnew" - new_shares = None total_shares = 10 - d = p._query_peers( (new_seqnum, new_root_hash, new_seqnum), - total_shares) - def _done( (target_map, peer_storage_servers) ): + d = p._query_peers(total_shares) + def _done(target_info): + (target_map, shares_per_peer, peer_storage_servers) = target_info shares_per_peer = {} for shnum in target_map: for (peerid, old_seqnum, old_R) in target_map[shnum]: @@ -327,37 +329,30 @@ class Publish(unittest.TestCase): def test_sharemap_nopeers(self): c, p = self.setup_for_sharemap(0) - new_seqnum = 3 - new_root_hash = "Rnew" - new_shares = None total_shares = 10 d = self.shouldFail(NotEnoughPeersError, "test_sharemap_nopeers", - p._query_peers, - (new_seqnum, new_root_hash, new_seqnum), - total_shares) + p._query_peers, total_shares) return d - def setup_for_write(self, num_peers, total_shares): - c, p = self.setup_for_sharemap(num_peers) + def test_write(self): + total_shares = 10 + c, p = self.setup_for_sharemap(20) + p._privkey = FakePrivKey(0) + p._encprivkey = "encprivkey" + p._pubkey = FakePubKey(0) # make some fake shares CONTENTS = "some initial contents" shares_and_ids = ( ["%07d" % i for i in range(10)], range(10) ) - d = defer.maybeDeferred(p._generate_shares, - (shares_and_ids, - 3, total_shares, - 21, # segsize - len(CONTENTS), - "IV"*8), - 3, # seqnum - FakePrivKey(0), "encprivkey", FakePubKey(0), - ) - return d, p - - def test_write(self): - total_shares = 10 - d, p = self.setup_for_write(20, total_shares) - d.addCallback(p._query_peers, total_shares) + d = defer.maybeDeferred(p._query_peers, total_shares) IV = "IV"*8 + d.addCallback(lambda target_info: + p._generate_shares( (shares_and_ids, + 3, total_shares, + 21, # segsize + len(CONTENTS), + target_info), + 3, # seqnum + IV)) d.addCallback(p._send_shares, IV) def _done((surprised, dispatch_map)): self.failIf(surprised, "surprised!") @@ -387,7 +382,6 @@ class Publish(unittest.TestCase): d.addCallback(_done) return d -del Publish # gotta run, will fix this in a few hours class FakePubKey: def __init__(self, count): diff --git a/src/allmydata/util/idlib.py b/src/allmydata/util/idlib.py index fa990b7a..a972b22e 100644 --- a/src/allmydata/util/idlib.py +++ b/src/allmydata/util/idlib.py @@ -253,3 +253,6 @@ from foolscap import base32 def nodeid_b2a(nodeid): # we display nodeids using the same base32 alphabet that Foolscap uses return base32.encode(nodeid) + +def shortnodeid_b2a(nodeid): + return nodeid_b2a(nodeid)[:8]