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electrum-bitcoinprivate
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electrum-bitcoinprivate/lib/blockchain.py

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#!/usr/bin/env python
#
# Electrum - lightweight Bitcoin client
# Copyright (C) 2012 thomasv@ecdsa.org
#
# 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.
import os
import util
from bitcoin import *
MAX_TARGET = 0x00000000FFFF0000000000000000000000000000000000000000000000000000
class Blockchain(util.PrintError):
'''Manages blockchain headers and their verification'''
def __init__(self, config, network):
self.config = config
self.network = network
self.headers_url = "https://headers.electrum.org/blockchain_headers"
self.local_height = 0
self.set_local_height()
def height(self):
return self.local_height
def init(self):
self.init_headers_file()
self.set_local_height()
self.print_error("%d blocks" % self.local_height)
def verify_header(self, header, prev_header, bits, target):
prev_hash = self.hash_header(prev_header)
assert prev_hash == header.get('prev_block_hash'), "prev hash mismatch: %s vs %s" % (prev_hash, header.get('prev_block_hash'))
assert bits == header.get('bits'), "bits mismatch: %s vs %s" % (bits, header.get('bits'))
_hash = self.hash_header(header)
assert int('0x' + _hash, 16) <= target, "insufficient proof of work: %s vs target %s" % (int('0x' + _hash, 16), target)
def verify_chain(self, chain):
first_header = chain[0]
prev_header = self.read_header(first_header.get('block_height') - 1)
for header in chain:
height = header.get('block_height')
bits, target = self.get_target(height / 2016, chain)
self.verify_header(header, prev_header, bits, target)
prev_header = header
def verify_chunk(self, index, data):
num = len(data) / 80
prev_header = None
if index != 0:
prev_header = self.read_header(index*2016 - 1)
bits, target = self.get_target(index)
for i in range(num):
raw_header = data[i*80:(i+1) * 80]
header = self.deserialize_header(raw_header)
self.verify_header(header, prev_header, bits, target)
prev_header = header
def serialize_header(self, res):
s = int_to_hex(res.get('version'), 4) \
+ rev_hex(res.get('prev_block_hash')) \
+ rev_hex(res.get('merkle_root')) \
+ int_to_hex(int(res.get('timestamp')), 4) \
+ int_to_hex(int(res.get('bits')), 4) \
+ int_to_hex(int(res.get('nonce')), 4)
return s
def deserialize_header(self, s):
hex_to_int = lambda s: int('0x' + s[::-1].encode('hex'), 16)
h = {}
h['version'] = hex_to_int(s[0:4])
h['prev_block_hash'] = hash_encode(s[4:36])
h['merkle_root'] = hash_encode(s[36:68])
h['timestamp'] = hex_to_int(s[68:72])
h['bits'] = hex_to_int(s[72:76])
h['nonce'] = hex_to_int(s[76:80])
return h
def hash_header(self, header):
if header is None:
return '0' * 64
return hash_encode(Hash(self.serialize_header(header).decode('hex')))
def path(self):
return os.path.join(self.config.path, 'blockchain_headers')
def init_headers_file(self):
filename = self.path()
if os.path.exists(filename):
return
try:
import urllib, socket
socket.setdefaulttimeout(30)
self.print_error("downloading ", self.headers_url)
urllib.urlretrieve(self.headers_url, filename)
self.print_error("done.")
except Exception:
self.print_error("download failed. creating file", filename)
open(filename, 'wb+').close()
def save_chunk(self, index, chunk):
filename = self.path()
f = open(filename, 'rb+')
f.seek(index * 2016 * 80)
h = f.write(chunk)
f.close()
self.set_local_height()
def save_header(self, header):
data = self.serialize_header(header).decode('hex')
assert len(data) == 80
height = header.get('block_height')
filename = self.path()
f = open(filename, 'rb+')
f.seek(height * 80)
h = f.write(data)
f.close()
self.set_local_height()
def set_local_height(self):
name = self.path()
if os.path.exists(name):
h = os.path.getsize(name)/80 - 1
if self.local_height != h:
self.local_height = h
def read_header(self, block_height):
name = self.path()
if os.path.exists(name):
f = open(name, 'rb')
f.seek(block_height * 80)
h = f.read(80)
f.close()
if len(h) == 80:
h = self.deserialize_header(h)
return h
def get_target(self, index, chain=None):
if index == 0:
return 0x1d00ffff, MAX_TARGET
first = self.read_header((index-1) * 2016)
last = self.read_header(index*2016 - 1)
if last is None:
for h in chain:
if h.get('block_height') == index*2016 - 1:
last = h
assert last is not None
# bits to target
bits = last.get('bits')
bitsN = (bits >> 24) & 0xff
assert bitsN >= 0x03 and bitsN <= 0x1d, "First part of bits should be in [0x03, 0x1d]"
bitsBase = bits & 0xffffff
assert bitsBase >= 0x8000 and bitsBase <= 0x7fffff, "Second part of bits should be in [0x8000, 0x7fffff]"
target = bitsBase << (8 * (bitsN-3))
# new target
nActualTimespan = last.get('timestamp') - first.get('timestamp')
nTargetTimespan = 14 * 24 * 60 * 60
nActualTimespan = max(nActualTimespan, nTargetTimespan / 4)
nActualTimespan = min(nActualTimespan, nTargetTimespan * 4)
new_target = min(MAX_TARGET, (target*nActualTimespan) / nTargetTimespan)
# convert new target to bits
c = ("%064x" % new_target)[2:]
while c[:2] == '00' and len(c) > 6:
c = c[2:]
bitsN, bitsBase = len(c) / 2, int('0x' + c[:6], 16)
if bitsBase >= 0x800000:
bitsN += 1
bitsBase >>= 8
new_bits = bitsN << 24 | bitsBase
return new_bits, bitsBase << (8 * (bitsN-3))
def connect_header(self, chain, header):
'''Builds a header chain until it connects. Returns True if it has
successfully connected, False if verification failed, otherwise the
height of the next header needed.'''
chain.append(header) # Ordered by decreasing height
previous_height = header['block_height'] - 1
previous_header = self.read_header(previous_height)
# Missing header, request it
if not previous_header:
return previous_height
# Does it connect to my chain?
prev_hash = self.hash_header(previous_header)
if prev_hash != header.get('prev_block_hash'):
self.print_error("reorg")
return previous_height
# The chain is complete. Reverse to order by increasing height
chain.reverse()
try:
self.verify_chain(chain)
self.print_error("new height:", previous_height + len(chain))
for header in chain:
self.save_header(header)
return True
except BaseException as e:
self.print_error(str(e))
return False
def connect_chunk(self, idx, hexdata):
try:
data = hexdata.decode('hex')
self.verify_chunk(idx, data)
self.print_error("validated chunk %d" % idx)
self.save_chunk(idx, data)
return idx + 1
except BaseException as e:
self.print_error('verify_chunk failed', str(e))
return idx - 1
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