lib/blockchain.py

   1 #!/usr/bin/env python
   2 #
   3 # Electrum - lightweight Bitcoin client
   4 # Copyright (C) 2012 thomasv@ecdsa.org
   5 #
   6 # This program is free software: you can redistribute it and/or modify
   7 # it under the terms of the GNU General Public License as published by
   8 # the Free Software Foundation, either version 3 of the License, or
   9 # (at your option) any later version.
  10 #
  11 # This program is distributed in the hope that it will be useful,
  12 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  14 # GNU General Public License for more details.
  15 #
  16 # You should have received a copy of the GNU General Public License
  17 # along with this program. If not, see <http://www.gnu.org/licenses/>.
  18
  19
  20 import threading, time, Queue, os, sys, shutil
  21 from util import user_dir, appdata_dir, print_error
  22 from bitcoin import *
  23
  24
  25 class Blockchain(threading.Thread):
  26
  27     def __init__(self, config, network):
  28         threading.Thread.__init__(self)
  29         self.daemon = True
  30         self.config = config
  31         self.network = network
  32         self.lock = threading.Lock()
  33         self.height = 0
  34         self.local_height = 0
  35         self.running = False
  36         self.headers_url = 'http://headers.electrum.org/blockchain_headers'
  37         self.set_local_height()
  38         self.queue = Queue.Queue()
  39         self.servers_height = {}
  40
  41
  42     def stop(self):
  43         with self.lock: self.running = False
  44
  45
  46     def is_running(self):
  47         with self.lock: return self.running
  48
  49
  50     def run(self):
  51         self.init_headers_file()
  52         self.set_local_height()
  53         print_error( "blocks:", self.local_height )
  54
  55         with self.lock:
  56             self.running = True
  57
  58         while self.is_running():
  59
  60             try:
  61                 result = self.queue.get()
  62             except Queue.Empty:
  63                 continue
  64
  65             if not result: continue
  66
  67             i, result = result
  68             header = result.get('result')
  69             height = header.get('block_height')
  70             self.servers_height[i.server] = height
  71
  72             if height > self.local_height + 50:
  73                 self.get_chunks(i, header, height)
  74                 self.network.trigger_callback('updated')
  75
  76             if height > self.local_height:
  77                 # get missing parts from interface (until it connects to my chain)
  78                 chain = self.get_chain( i, header )
  79
  80                 # skip that server if the result is not consistent
  81                 if not chain: continue
  82
  83                 # verify the chain
  84                 if self.verify_chain( chain ):
  85                     print_error("height:", height, i.server)
  86                     for header in chain:
  87                         self.save_header(header)
  88                         self.height = height
  89                 else:
  90                     print_error("error", i.server)
  91                     # todo: dismiss that server
  92
  93                 self.network.trigger_callback('updated')
  94
  95             h = self.servers_height.get(self.network.interface.server)
  96             if h is not None and h < height - 1:
  97                 print "server is lagging", height, h
  98                 self.network.interface.stop()
  99
 100
 101
 102
 103     def verify_chain(self, chain):
 104
 105         first_header = chain[0]
 106         prev_header = self.read_header(first_header.get('block_height') -1)
 107
 108         for header in chain:
 109
 110             height = header.get('block_height')
 111
 112             prev_hash = self.hash_header(prev_header)
 113             bits, target = self.get_target(height/2016)
 114             _hash = self.hash_header(header)
 115             try:
 116                 assert prev_hash == header.get('prev_block_hash')
 117                 assert bits == header.get('bits')
 118                 assert eval('0x'+_hash) < target
 119             except:
 120                 return False
 121
 122             prev_header = header
 123
 124         return True
 125
 126
 127
 128     def verify_chunk(self, index, hexdata):
 129         data = hexdata.decode('hex')
 130         height = index*2016
 131         num = len(data)/80
 132
 133         if index == 0:
 134             previous_hash = ("0"*64)
 135         else:
 136             prev_header = self.read_header(index*2016-1)
 137             if prev_header is None: raise
 138             previous_hash = self.hash_header(prev_header)
 139
 140         bits, target = self.get_target(index)
 141
 142         for i in range(num):
 143             height = index*2016 + i
 144             raw_header = data[i*80:(i+1)*80]
 145             header = self.header_from_string(raw_header)
 146             _hash = self.hash_header(header)
 147             assert previous_hash == header.get('prev_block_hash')
 148             assert bits == header.get('bits')
 149             assert eval('0x'+_hash) < target
 150
 151             previous_header = header
 152             previous_hash = _hash
 153
 154         self.save_chunk(index, data)
 155         print_error("validated chunk %d"%height)
 156
 157
 158     def verify_header(self, header):
 159         # add header to the blockchain file
 160         # if there is a reorg, push it in a stack
 161
 162         height = header.get('block_height')
 163
 164         prev_header = self.read_header(height -1)
 165         if not prev_header:
 166             # return False to request previous header
 167             return False
 168
 169         prev_hash = self.hash_header(prev_header)
 170         bits, target = self.get_target(height/2016)
 171         _hash = self.hash_header(header)
 172         try:
 173             assert prev_hash == header.get('prev_block_hash')
 174             assert bits == header.get('bits')
 175             assert eval('0x'+_hash) < target
 176         except:
 177             # this can be caused by a reorg.
 178             print_error("verify header failed"+ repr(header))
 179             verifier.undo_verifications()
 180
 181             # return False to request previous header.
 182             return False
 183
 184         self.save_header(header)
 185         print_error("verify header:", _hash, height)
 186         return True
 187
 188
 189     def header_to_string(self, res):
 190         s = int_to_hex(res.get('version'),4) \
 191             + rev_hex(res.get('prev_block_hash')) \
 192             + rev_hex(res.get('merkle_root')) \
 193             + int_to_hex(int(res.get('timestamp')),4) \
 194             + int_to_hex(int(res.get('bits')),4) \
 195             + int_to_hex(int(res.get('nonce')),4)
 196         return s
 197
 198
 199     def header_from_string(self, s):
 200         hex_to_int = lambda s: eval('0x' + s[::-1].encode('hex'))
 201         h = {}
 202         h['version'] = hex_to_int(s[0:4])
 203         h['prev_block_hash'] = hash_encode(s[4:36])
 204         h['merkle_root'] = hash_encode(s[36:68])
 205         h['timestamp'] = hex_to_int(s[68:72])
 206         h['bits'] = hex_to_int(s[72:76])
 207         h['nonce'] = hex_to_int(s[76:80])
 208         return h
 209
 210     def hash_header(self, header):
 211         return rev_hex(Hash(self.header_to_string(header).decode('hex')).encode('hex'))
 212
 213     def path(self):
 214         return os.path.join( self.config.path, 'blockchain_headers')
 215
 216     def init_headers_file(self):
 217         filename = self.path()
 218         if os.path.exists(filename):
 219             return
 220
 221         try:
 222             import urllib, socket
 223             socket.setdefaulttimeout(30)
 224             print_error("downloading ", self.headers_url )
 225             urllib.urlretrieve(self.headers_url, filename)
 226         except:
 227             print_error( "download failed. creating file", filename )
 228             open(filename,'wb+').close()
 229
 230     def save_chunk(self, index, chunk):
 231         filename = self.path()
 232         f = open(filename,'rb+')
 233         f.seek(index*2016*80)
 234         h = f.write(chunk)
 235         f.close()
 236         self.set_local_height()
 237
 238     def save_header(self, header):
 239         data = self.header_to_string(header).decode('hex')
 240         assert len(data) == 80
 241         height = header.get('block_height')
 242         filename = self.path()
 243         f = open(filename,'rb+')
 244         f.seek(height*80)
 245         h = f.write(data)
 246         f.close()
 247         self.set_local_height()
 248
 249
 250     def set_local_height(self):
 251         name = self.path()
 252         if os.path.exists(name):
 253             h = os.path.getsize(name)/80 - 1
 254             if self.local_height != h:
 255                 self.local_height = h
 256                 self.height = self.local_height
 257
 258
 259     def read_header(self, block_height):
 260         name = self.path()
 261         if os.path.exists(name):
 262             f = open(name,'rb')
 263             f.seek(block_height*80)
 264             h = f.read(80)
 265             f.close()
 266             if len(h) == 80:
 267                 h = self.header_from_string(h)
 268                 return h
 269
 270
 271     def get_target(self, index):
 272
 273         max_target = 0x00000000FFFF0000000000000000000000000000000000000000000000000000
 274         if index == 0: return 0x1d00ffff, max_target
 275
 276         first = self.read_header((index-1)*2016)
 277         last = self.read_header(index*2016-1)
 278
 279         nActualTimespan = last.get('timestamp') - first.get('timestamp')
 280         nTargetTimespan = 14*24*60*60
 281         nActualTimespan = max(nActualTimespan, nTargetTimespan/4)
 282         nActualTimespan = min(nActualTimespan, nTargetTimespan*4)
 283
 284         bits = last.get('bits')
 285         # convert to bignum
 286         MM = 256*256*256
 287         a = bits%MM
 288         if a < 0x8000:
 289             a *= 256
 290         target = (a) * pow(2, 8 * (bits/MM - 3))
 291
 292         # new target
 293         new_target = min( max_target, (target * nActualTimespan)/nTargetTimespan )
 294
 295         # convert it to bits
 296         c = ("%064X"%new_target)[2:]
 297         i = 31
 298         while c[0:2]=="00":
 299             c = c[2:]
 300             i -= 1
 301
 302         c = eval('0x'+c[0:6])
 303         if c > 0x800000:
 304             c /= 256
 305             i += 1
 306
 307         new_bits = c + MM * i
 308         return new_bits, new_target
 309
 310
 311     def request_header(self, i, h):
 312         print_error("requesting header %d from %s"%(h, i.server))
 313         i.send([ ('blockchain.block.get_header',[h])], 'get_header')
 314
 315     def retrieve_header(self, i):
 316         while True:
 317             try:
 318                 r = i.get_response('get_header',timeout=1)
 319             except Queue.Empty:
 320                 print_error('timeout')
 321                 continue
 322
 323             if r.get('error'):
 324                 print_error('Verifier received an error:', r)
 325                 continue
 326
 327             # 3. handle response
 328             method = r['method']
 329             params = r['params']
 330             result = r['result']
 331
 332             if method == 'blockchain.block.get_header':
 333                 return result
 334
 335
 336
 337     def get_chain(self, interface, final_header):
 338
 339         header = final_header
 340         chain = [ final_header ]
 341         requested_header = False
 342
 343         while self.is_running():
 344
 345             if requested_header:
 346                 header = self.retrieve_header(interface)
 347                 if not header: return
 348                 chain = [ header ] + chain
 349                 requested_header = False
 350
 351             height = header.get('block_height')
 352             previous_header = self.read_header(height -1)
 353             if not previous_header:
 354                 self.request_header(interface, height - 1)
 355                 requested_header = True
 356                 continue
 357
 358             # verify that it connects to my chain
 359             prev_hash = self.hash_header(previous_header)
 360             if prev_hash != header.get('prev_block_hash'):
 361                 print_error("reorg")
 362                 self.request_header(interface, height - 1)
 363                 requested_header = True
 364                 continue
 365
 366             else:
 367                 # the chain is complete
 368                 return chain
 369
 370
 371     def get_chunks(self, i, header, height):
 372         requested_chunks = []
 373         min_index = (self.local_height + 1)/2016
 374         max_index = (height + 1)/2016
 375         for n in range(min_index, max_index + 1):
 376             print_error( "requesting chunk", n )
 377             i.send([ ('blockchain.block.get_chunk',[n])], 'get_header')
 378             requested_chunks.append(n)
 379             break
 380
 381         while requested_chunks:
 382             try:
 383                 r = i.get_response('get_header',timeout=1)
 384             except Queue.Empty:
 385                 continue
 386             if not r: continue
 387
 388             if r.get('error'):
 389                 print_error('Verifier received an error:', r)
 390                 continue
 391
 392             # 3. handle response
 393             method = r['method']
 394             params = r['params']
 395             result = r['result']
 396
 397             if method == 'blockchain.block.get_chunk':
 398                 index = params[0]
 399                 self.verify_chunk(index, result)
 400                 requested_chunks.remove(index)
 401
 402
 403
 404
 405
 406
 407