#!/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 import bitcoin 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.checkpoint_height, self.checkpoint_hash = self.get_checkpoint() self.check_truncate_headers() self.set_local_height() def height(self): return self.local_height def init(self): import threading if os.path.exists(self.path()): self.downloading_headers = False return self.downloading_headers = True t = threading.Thread(target = self.init_headers_file) t.daemon = True t.start() def pass_checkpoint(self, header): if type(header) is not dict: return False if header.get('block_height') != self.checkpoint_height: return True if header.get('prev_block_hash') is None: header['prev_block_hash'] = '00'*32 try: _hash = self.hash_header(header) except: return False return _hash == self.checkpoint_hash def verify_header(self, header, prev_header, bits, target): prev_hash = self.hash_header(prev_header) _hash = self.hash_header(header) if prev_hash != header.get('prev_block_hash'): raise BaseException("prev hash mismatch: %s vs %s" % (prev_hash, header.get('prev_block_hash'))) if not self.pass_checkpoint(header): raise BaseException('failed checkpoint') if self.checkpoint_height == header.get('block_height'): self.print_error("validated checkpoint", self.checkpoint_height) if bitcoin.TESTNET: return if bits != header.get('bits'): raise BaseException("bits mismatch: %s vs %s" % (bits, header.get('bits'))) if int('0x' + _hash, 16) > target: raise BaseException("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, index*2016 + i) 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, height): 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]) h['block_height'] = height 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 util.get_headers_path(self.config) def init_headers_file(self): filename = self.path() try: import urllib, socket socket.setdefaulttimeout(30) self.print_error("downloading ", bitcoin.HEADERS_URL) urllib.urlretrieve(bitcoin.HEADERS_URL, filename + '.tmp') os.rename(filename + '.tmp', filename) self.print_error("done.") except Exception: self.print_error("download failed. creating file", filename) open(filename, 'wb+').close() self.downloading_headers = False self.set_local_height() self.print_error("%d blocks" % self.local_height) 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): self.local_height = 0 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, block_height) return h def BIP9(self, height, flag): v = self.read_header(height)['version'] return ((v & 0xE0000000) == 0x20000000) and ((v & flag) == flag) def segwit_support(self, N=144): h = self.local_height return sum([self.BIP9(h-i, 2) for i in range(N)])*10000/N/100. def check_truncate_headers(self): checkpoint = self.read_header(self.checkpoint_height) if checkpoint is None: return if self.hash_header(checkpoint) == self.checkpoint_hash: return self.print_error('checkpoint mismatch:', self.hash_header(checkpoint), self.checkpoint_hash) self.truncate_headers(self.checkpoint_height) def truncate_headers(self, height): self.print_error('Truncating headers file at height %d'%height) name = self.path() f = open(name, 'rb+') f.seek(height * 80) f.truncate() f.close() def get_target(self, index, chain=None): if bitcoin.TESTNET: return 0, 0 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 if not (bitsN >= 0x03 and bitsN <= 0x1d): raise BaseException("First part of bits should be in [0x03, 0x1d]") bitsBase = bits & 0xffffff if not (bitsBase >= 0x8000 and bitsBase <= 0x7fffff): raise BaseException("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 can_connect(self, header): previous_height = header['block_height'] - 1 previous_header = self.read_header(previous_height) if not previous_header: return False prev_hash = self.hash_header(previous_header) if prev_hash != header.get('prev_block_hash'): return False height = header.get('block_height') bits, target = self.get_target(height / 2016) try: self.verify_header(header, previous_header, bits, target) except: return False return True 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 True except BaseException as e: self.print_error('verify_chunk failed', str(e)) return False def get_checkpoint(self): height = self.config.get('checkpoint_height', 0) value = self.config.get('checkpoint_value', bitcoin.GENESIS) return (height, value) def set_checkpoint(self, height, value): self.checkpoint_height = height self.checkpoint_hash = value self.config.set_key('checkpoint_height', height) self.config.set_key('checkpoint_value', value) self.check_truncate_headers()