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156 lines
6.6 KiB
156 lines
6.6 KiB
# Electrum - Lightweight Bitcoin Client
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# Copyright (c) 2012 Thomas Voegtlin
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#
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# Permission is hereby granted, free of charge, to any person
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# obtaining a copy of this software and associated documentation files
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# (the "Software"), to deal in the Software without restriction,
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# including without limitation the rights to use, copy, modify, merge,
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# publish, distribute, sublicense, and/or sell copies of the Software,
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# and to permit persons to whom the Software is furnished to do so,
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# subject to the following conditions:
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#
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# The above copyright notice and this permission notice shall be
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# included in all copies or substantial portions of the Software.
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#
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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# SOFTWARE.
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from .util import ThreadJob, bh2u
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from .bitcoin import Hash, hash_decode, hash_encode
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from .transaction import Transaction
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class InnerNodeOfSpvProofIsValidTx(Exception): pass
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class SPV(ThreadJob):
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""" Simple Payment Verification """
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def __init__(self, network, wallet):
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self.wallet = wallet
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self.network = network
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self.blockchain = network.blockchain()
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self.merkle_roots = {} # txid -> merkle root (once it has been verified)
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self.requested_merkle = set() # txid set of pending requests
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def run(self):
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interface = self.network.interface
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if not interface:
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return
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blockchain = interface.blockchain
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if not blockchain:
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return
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lh = self.network.get_local_height()
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unverified = self.wallet.get_unverified_txs()
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for tx_hash, tx_height in unverified.items():
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# do not request merkle branch before headers are available
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if (tx_height > 0) and (tx_height <= lh):
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header = blockchain.read_header(tx_height)
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if header is None:
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index = tx_height // 2016
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if index < len(blockchain.checkpoints):
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self.network.request_chunk(interface, index)
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else:
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if (tx_hash not in self.requested_merkle
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and tx_hash not in self.merkle_roots):
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self.network.get_merkle_for_transaction(
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tx_hash,
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tx_height,
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self.verify_merkle)
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self.print_error('requested merkle', tx_hash)
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self.requested_merkle.add(tx_hash)
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if self.network.blockchain() != self.blockchain:
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self.blockchain = self.network.blockchain()
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self.undo_verifications()
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def verify_merkle(self, r):
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if self.wallet.verifier is None:
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return # we have been killed, this was just an orphan callback
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if r.get('error'):
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self.print_error('received an error:', r)
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return
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params = r['params']
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merkle = r['result']
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# Verify the hash of the server-provided merkle branch to a
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# transaction matches the merkle root of its block
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tx_hash = params[0]
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tx_height = merkle.get('block_height')
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pos = merkle.get('pos')
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try:
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merkle_root = self.hash_merkle_root(merkle['merkle'], tx_hash, pos)
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except InnerNodeOfSpvProofIsValidTx:
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self.print_error("merkle verification failed for {} (inner node looks like tx)"
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.format(tx_hash))
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return
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header = self.network.blockchain().read_header(tx_height)
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# FIXME: if verification fails below,
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# we should make a fresh connection to a server to
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# recover from this, as this TX will now never verify
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if not header:
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self.print_error(
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"merkle verification failed for {} (missing header {})"
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.format(tx_hash, tx_height))
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return
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if header.get('merkle_root') != merkle_root:
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self.print_error(
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"merkle verification failed for {} (merkle root mismatch {} != {})"
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.format(tx_hash, header.get('merkle_root'), merkle_root))
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return
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# we passed all the tests
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self.merkle_roots[tx_hash] = merkle_root
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try:
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# note: we could pop in the beginning, but then we would request
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# this proof again in case of verification failure from the same server
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self.requested_merkle.remove(tx_hash)
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except KeyError: pass
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self.print_error("verified %s" % tx_hash)
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self.wallet.add_verified_tx(tx_hash, (tx_height, header.get('timestamp'), pos))
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if self.is_up_to_date() and self.wallet.is_up_to_date():
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self.wallet.save_verified_tx(write=True)
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@classmethod
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def hash_merkle_root(cls, merkle_s, target_hash, pos):
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h = hash_decode(target_hash)
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for i in range(len(merkle_s)):
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item = merkle_s[i]
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h = Hash(hash_decode(item) + h) if ((pos >> i) & 1) else Hash(h + hash_decode(item))
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cls._raise_if_valid_tx(bh2u(h))
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return hash_encode(h)
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@classmethod
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def _raise_if_valid_tx(cls, raw_tx: str):
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# If an inner node of the merkle proof is also a valid tx, chances are, this is an attack.
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# https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2018-June/016105.html
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# https://lists.linuxfoundation.org/pipermail/bitcoin-dev/attachments/20180609/9f4f5b1f/attachment-0001.pdf
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# https://bitcoin.stackexchange.com/questions/76121/how-is-the-leaf-node-weakness-in-merkle-trees-exploitable/76122#76122
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tx = Transaction(raw_tx)
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try:
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tx.deserialize()
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except:
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pass
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else:
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raise InnerNodeOfSpvProofIsValidTx()
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def undo_verifications(self):
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height = self.blockchain.get_checkpoint()
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tx_hashes = self.wallet.undo_verifications(self.blockchain, height)
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for tx_hash in tx_hashes:
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self.print_error("redoing", tx_hash)
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self.remove_spv_proof_for_tx(tx_hash)
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def remove_spv_proof_for_tx(self, tx_hash):
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self.merkle_roots.pop(tx_hash, None)
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try:
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self.requested_merkle.remove(tx_hash)
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except KeyError:
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pass
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def is_up_to_date(self):
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return not self.requested_merkle
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