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# Electrum - Lightweight Bitcoin Client
# Copyright (c) 2012 Thomas Voegtlin
#
# Permission is hereby granted, free of charge, to any person
# obtaining a copy of this software and associated documentation files
# (the "Software"), to deal in the Software without restriction,
# including without limitation the rights to use, copy, modify, merge,
# publish, distribute, sublicense, and/or sell copies of the Software,
# and to permit persons to whom the Software is furnished to do so,
# subject to the following conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.
from .util import ThreadJob
from .bitcoin import *
class SPV(ThreadJob):
""" Simple Payment Verification """
def __init__(self, network, wallet):
self.wallet = wallet
self.network = network
self.blockchain = network.blockchain()
# Keyed by tx hash. Value is None if the merkle branch was
# requested, and the merkle root once it has been verified
self.merkle_roots = {}
def run(self):
interface = self.network.interface
if not interface:
return
blockchain = interface.blockchain
if not blockchain:
return
lh = self.network.get_local_height()
unverified = self.wallet.get_unverified_txs()
for tx_hash, tx_height in unverified.items():
# do not request merkle branch before headers are available
if (tx_height > 0) and (tx_height <= lh):
header = blockchain.read_header(tx_height)
if header is None:
index = tx_height // 2016
if index < len(blockchain.checkpoints):
self.network.request_chunk(interface, index)
else:
if tx_hash not in self.merkle_roots:
request = ('blockchain.transaction.get_merkle',
[tx_hash, tx_height])
self.network.send([request], self.verify_merkle)
self.print_error('requested merkle', tx_hash)
self.merkle_roots[tx_hash] = None
if self.network.blockchain() != self.blockchain:
self.blockchain = self.network.blockchain()
self.undo_verifications()
def verify_merkle(self, r):
if self.wallet.verifier is None:
return # we have been killed, this was just an orphan callback
if r.get('error'):
self.print_error('received an error:', r)
return
params = r['params']
merkle = r['result']
# Verify the hash of the server-provided merkle branch to a
# transaction matches the merkle root of its block
tx_hash = params[0]
tx_height = merkle.get('block_height')
pos = merkle.get('pos')
merkle_root = self.hash_merkle_root(merkle['merkle'], tx_hash, pos)
header = self.network.blockchain().read_header(tx_height)
# FIXME: if verification fails below,
# we should make a fresh connection to a server to
# recover from this, as this TX will now never verify
if not header:
self.print_error(
"merkle verification failed for {} (missing header {})"
.format(tx_hash, tx_height))
return
if header.get('merkle_root') != merkle_root:
self.print_error(
"merkle verification failed for {} (merkle root mismatch {} != {})"
.format(tx_hash, header.get('merkle_root'), merkle_root))
return
# we passed all the tests
self.merkle_roots[tx_hash] = merkle_root
self.print_error("verified %s" % tx_hash)
self.wallet.add_verified_tx(tx_hash, (tx_height, header.get('timestamp'), pos))
@classmethod
def hash_merkle_root(cls, merkle_s, target_hash, pos):
h = hash_decode(target_hash)
for i in range(len(merkle_s)):
item = merkle_s[i]
h = Hash(hash_decode(item) + h) if ((pos >> i) & 1) else Hash(h + hash_decode(item))
return hash_encode(h)
def undo_verifications(self):
height = self.blockchain.get_checkpoint()
tx_hashes = self.wallet.undo_verifications(self.blockchain, height)
for tx_hash in tx_hashes:
self.print_error("redoing", tx_hash)
self.merkle_roots.pop(tx_hash, None)