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, header = result
  68             if not header: continue
  69
  70             height = header.get('block_height')
  71             self.servers_height[i.server] = height
  72
  73             if height > self.local_height + 50:
  74                 self.get_chunks(i, header, height)
  75                 self.network.trigger_callback('updated')
  76
  77             if height > self.local_height:
  78                 # get missing parts from interface (until it connects to my chain)
  79                 chain = self.get_chain( i, header )
  80
  81                 # skip that server if the result is not consistent
  82                 if not chain: continue
  83
  84                 # verify the chain
  85                 if self.verify_chain( chain ):
  86                     print_error("height:", height, i.server)
  87                     for header in chain:
  88                         self.save_header(header)
  89                         self.height = height
  90                 else:
  91                     print_error("error", i.server)
  92                     # todo: dismiss that server
  93
  94                 self.network.trigger_callback('updated')
  95
  96             h = self.servers_height.get(self.network.interface.server)
  97             if h is not None and h < height :
  98                 print_error( "Server is lagging", height, h)
  99                 if self.config.get('auto_cycle'):
 100                     self.network.set_server(i.server)
 101                 else:
 102                     self.network.interface.stop()
 103
 104
 105
 106
 107     def verify_chain(self, chain):
 108
 109         first_header = chain[0]
 110         prev_header = self.read_header(first_header.get('block_height') -1)
 111
 112         for header in chain:
 113
 114             height = header.get('block_height')
 115
 116             prev_hash = self.hash_header(prev_header)
 117             bits, target = self.get_target(height/2016)
 118             _hash = self.hash_header(header)
 119             try:
 120                 assert prev_hash == header.get('prev_block_hash')
 121                 assert bits == header.get('bits')
 122                 assert eval('0x'+_hash) < target
 123             except:
 124                 return False
 125
 126             prev_header = header
 127
 128         return True
 129
 130
 131
 132     def verify_chunk(self, index, hexdata):
 133         data = hexdata.decode('hex')
 134         height = index*2016
 135         num = len(data)/80
 136
 137         if index == 0:
 138             previous_hash = ("0"*64)
 139         else:
 140             prev_header = self.read_header(index*2016-1)
 141             if prev_header is None: raise
 142             previous_hash = self.hash_header(prev_header)
 143
 144         bits, target = self.get_target(index)
 145
 146         for i in range(num):
 147             height = index*2016 + i
 148             raw_header = data[i*80:(i+1)*80]
 149             header = self.header_from_string(raw_header)
 150             _hash = self.hash_header(header)
 151             assert previous_hash == header.get('prev_block_hash')
 152             assert bits == header.get('bits')
 153             assert eval('0x'+_hash) < target
 154
 155             previous_header = header
 156             previous_hash = _hash
 157
 158         self.save_chunk(index, data)
 159         print_error("validated chunk %d"%height)
 160
 161
 162     def verify_header(self, header):
 163         # add header to the blockchain file
 164         # if there is a reorg, push it in a stack
 165
 166         height = header.get('block_height')
 167
 168         prev_header = self.read_header(height -1)
 169         if not prev_header:
 170             # return False to request previous header
 171             return False
 172
 173         prev_hash = self.hash_header(prev_header)
 174         bits, target = self.get_target(height/2016)
 175         _hash = self.hash_header(header)
 176         try:
 177             assert prev_hash == header.get('prev_block_hash')
 178             assert bits == header.get('bits')
 179             assert eval('0x'+_hash) < target
 180         except:
 181             # this can be caused by a reorg.
 182             print_error("verify header failed"+ repr(header))
 183             verifier.undo_verifications()
 184
 185             # return False to request previous header.
 186             return False
 187
 188         self.save_header(header)
 189         print_error("verify header:", _hash, height)
 190         return True
 191
 192
 193     def header_to_string(self, res):
 194         s = int_to_hex(res.get('version'),4) \
 195             + rev_hex(res.get('prev_block_hash')) \
 196             + rev_hex(res.get('merkle_root')) \
 197             + int_to_hex(int(res.get('timestamp')),4) \
 198             + int_to_hex(int(res.get('bits')),4) \
 199             + int_to_hex(int(res.get('nonce')),4)
 200         return s
 201
 202
 203     def header_from_string(self, s):
 204         hex_to_int = lambda s: eval('0x' + s[::-1].encode('hex'))
 205         h = {}
 206         h['version'] = hex_to_int(s[0:4])
 207         h['prev_block_hash'] = hash_encode(s[4:36])
 208         h['merkle_root'] = hash_encode(s[36:68])
 209         h['timestamp'] = hex_to_int(s[68:72])
 210         h['bits'] = hex_to_int(s[72:76])
 211         h['nonce'] = hex_to_int(s[76:80])
 212         return h
 213
 214     def hash_header(self, header):
 215         return rev_hex(Hash(self.header_to_string(header).decode('hex')).encode('hex'))
 216
 217     def path(self):
 218         return os.path.join( self.config.path, 'blockchain_headers')
 219
 220     def init_headers_file(self):
 221         filename = self.path()
 222         if os.path.exists(filename):
 223             return
 224
 225         try:
 226             import urllib, socket
 227             socket.setdefaulttimeout(30)
 228             print_error("downloading ", self.headers_url )
 229             urllib.urlretrieve(self.headers_url, filename)
 230         except:
 231             print_error( "download failed. creating file", filename )
 232             open(filename,'wb+').close()
 233
 234     def save_chunk(self, index, chunk):
 235         filename = self.path()
 236         f = open(filename,'rb+')
 237         f.seek(index*2016*80)
 238         h = f.write(chunk)
 239         f.close()
 240         self.set_local_height()
 241
 242     def save_header(self, header):
 243         data = self.header_to_string(header).decode('hex')
 244         assert len(data) == 80
 245         height = header.get('block_height')
 246         filename = self.path()
 247         f = open(filename,'rb+')
 248         f.seek(height*80)
 249         h = f.write(data)
 250         f.close()
 251         self.set_local_height()
 252
 253
 254     def set_local_height(self):
 255         name = self.path()
 256         if os.path.exists(name):
 257             h = os.path.getsize(name)/80 - 1
 258             if self.local_height != h:
 259                 self.local_height = h
 260                 self.height = self.local_height
 261
 262
 263     def read_header(self, block_height):
 264         name = self.path()
 265         if os.path.exists(name):
 266             f = open(name,'rb')
 267             f.seek(block_height*80)
 268             h = f.read(80)
 269             f.close()
 270             if len(h) == 80:
 271                 h = self.header_from_string(h)
 272                 return h
 273
 274
 275     def get_target(self, index):
 276
 277         max_target = 0x00000000FFFF0000000000000000000000000000000000000000000000000000
 278         if index == 0: return 0x1d00ffff, max_target
 279
 280         first = self.read_header((index-1)*2016)
 281         last = self.read_header(index*2016-1)
 282
 283         nActualTimespan = last.get('timestamp') - first.get('timestamp')
 284         nTargetTimespan = 14*24*60*60
 285         nActualTimespan = max(nActualTimespan, nTargetTimespan/4)
 286         nActualTimespan = min(nActualTimespan, nTargetTimespan*4)
 287
 288         bits = last.get('bits')
 289         # convert to bignum
 290         MM = 256*256*256
 291         a = bits%MM
 292         if a < 0x8000:
 293             a *= 256
 294         target = (a) * pow(2, 8 * (bits/MM - 3))
 295
 296         # new target
 297         new_target = min( max_target, (target * nActualTimespan)/nTargetTimespan )
 298
 299         # convert it to bits
 300         c = ("%064X"%new_target)[2:]
 301         i = 31
 302         while c[0:2]=="00":
 303             c = c[2:]
 304             i -= 1
 305
 306         c = eval('0x'+c[0:6])
 307         if c > 0x800000:
 308             c /= 256
 309             i += 1
 310
 311         new_bits = c + MM * i
 312         return new_bits, new_target
 313
 314
 315     def request_header(self, i, h, queue):
 316         print_error("requesting header %d from %s"%(h, i.server))
 317         i.send([ ('blockchain.block.get_header',[h])], lambda i,r: queue.put((i,r)))
 318
 319     def retrieve_header(self, i, queue):
 320         while True:
 321             try:
 322                 ir = queue.get(timeout=1)
 323             except Queue.Empty:
 324                 print_error('timeout')
 325                 continue
 326
 327             if not ir:
 328                 continue
 329
 330             i, r = ir
 331
 332             if r.get('error'):
 333                 print_error('Verifier received an error:', r)
 334                 continue
 335
 336             # 3. handle response
 337             method = r['method']
 338             params = r['params']
 339             result = r['result']
 340
 341             if method == 'blockchain.block.get_header':
 342                 return result
 343
 344
 345
 346     def get_chain(self, interface, final_header):
 347
 348         header = final_header
 349         chain = [ final_header ]
 350         requested_header = False
 351         queue = Queue.Queue()
 352
 353         while self.is_running():
 354
 355             if requested_header:
 356                 header = self.retrieve_header(interface, queue)
 357                 if not header: return
 358                 chain = [ header ] + chain
 359                 requested_header = False
 360
 361             height = header.get('block_height')
 362             previous_header = self.read_header(height -1)
 363             if not previous_header:
 364                 self.request_header(interface, height - 1, queue)
 365                 requested_header = True
 366                 continue
 367
 368             # verify that it connects to my chain
 369             prev_hash = self.hash_header(previous_header)
 370             if prev_hash != header.get('prev_block_hash'):
 371                 print_error("reorg")
 372                 self.request_header(interface, height - 1, queue)
 373                 requested_header = True
 374                 continue
 375
 376             else:
 377                 # the chain is complete
 378                 return chain
 379
 380
 381     def get_chunks(self, i, header, height):
 382         requested_chunks = []
 383         queue = Queue.Queue()
 384         min_index = (self.local_height + 1)/2016
 385         max_index = (height + 1)/2016
 386         for n in range(min_index, max_index + 1):
 387             print_error( "requesting chunk", n )
 388             i.send([ ('blockchain.block.get_chunk',[n])], lambda i,r:queue.put(r))
 389             requested_chunks.append(n)
 390             break
 391
 392         while requested_chunks:
 393             try:
 394                 r = queue.get(timeout=1)
 395             except Queue.Empty:
 396                 continue
 397             if not r: continue
 398
 399             if r.get('error'):
 400                 print_error('Verifier received an error:', r)
 401                 continue
 402
 403             # 3. handle response
 404             params = r['params']
 405             result = r['result']
 406
 407             index = params[0]
 408             self.verify_chunk(index, result)
 409             requested_chunks.remove(index)
 410
 411
 412
 413
 414
 415
 416