#!/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