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         self.is_lagging = False
  41
  42
  43     def stop(self):
  44         with self.lock: self.running = False
  45
  46
  47     def is_running(self):
  48         with self.lock: return self.running
  49
  50
  51     def run(self):
  52         self.init_headers_file()
  53         self.set_local_height()
  54         print_error( "blocks:", self.local_height )
  55
  56         with self.lock:
  57             self.running = True
  58
  59         while self.is_running():
  60
  61             try:
  62                 result = self.queue.get()
  63             except Queue.Empty:
  64                 continue
  65
  66             if not result: continue
  67
  68             i, header = result
  69             if not header: continue
  70
  71             height = header.get('block_height')
  72             self.servers_height[i.server] = height
  73
  74             if height > self.local_height + 50:
  75                 self.get_chunks(i, header, height)
  76                 self.network.trigger_callback('updated')
  77
  78             if height > self.local_height:
  79                 # get missing parts from interface (until it connects to my chain)
  80                 chain = self.get_chain( i, header )
  81
  82                 # skip that server if the result is not consistent
  83                 if not chain: continue
  84
  85                 # verify the chain
  86                 if self.verify_chain( chain ):
  87                     print_error("height:", height, i.server)
  88                     for header in chain:
  89                         self.save_header(header)
  90                         self.height = height
  91                 else:
  92                     print_error("error", i.server)
  93                     # todo: dismiss that server
  94
  95             if self.network.is_connected():
  96                 h = self.servers_height.get(self.network.interface.server)
  97             else:
  98                 h = None
  99
 100             if h is not None and h < height - 1:
 101                 print_error( "Server is lagging", height, h)
 102                 if self.config.get('auto_cycle'):
 103                     self.network.set_server(i.server)
 104                 else:
 105                     self.network.is_lagging = True
 106             else:
 107                 self.network.is_lagging = False
 108
 109             self.network.trigger_callback('updated')
 110
 111
 112
 113
 114     def verify_chain(self, chain):
 115
 116         first_header = chain[0]
 117         prev_header = self.read_header(first_header.get('block_height') -1)
 118
 119         for header in chain:
 120
 121             height = header.get('block_height')
 122
 123             prev_hash = self.hash_header(prev_header)
 124             bits, target = self.get_target(height/2016)
 125             _hash = self.hash_header(header)
 126             try:
 127                 assert prev_hash == header.get('prev_block_hash')
 128                 assert bits == header.get('bits')
 129                 assert eval('0x'+_hash) < target
 130             except:
 131                 return False
 132
 133             prev_header = header
 134
 135         return True
 136
 137
 138
 139     def verify_chunk(self, index, hexdata):
 140         data = hexdata.decode('hex')
 141         height = index*2016
 142         num = len(data)/80
 143
 144         if index == 0:
 145             previous_hash = ("0"*64)
 146         else:
 147             prev_header = self.read_header(index*2016-1)
 148             if prev_header is None: raise
 149             previous_hash = self.hash_header(prev_header)
 150
 151         bits, target = self.get_target(index)
 152
 153         for i in range(num):
 154             height = index*2016 + i
 155             raw_header = data[i*80:(i+1)*80]
 156             header = self.header_from_string(raw_header)
 157             _hash = self.hash_header(header)
 158             assert previous_hash == header.get('prev_block_hash')
 159             assert bits == header.get('bits')
 160             assert eval('0x'+_hash) < target
 161
 162             previous_header = header
 163             previous_hash = _hash
 164
 165         self.save_chunk(index, data)
 166         print_error("validated chunk %d"%height)
 167
 168
 169     def verify_header(self, header):
 170         # add header to the blockchain file
 171         # if there is a reorg, push it in a stack
 172
 173         height = header.get('block_height')
 174
 175         prev_header = self.read_header(height -1)
 176         if not prev_header:
 177             # return False to request previous header
 178             return False
 179
 180         prev_hash = self.hash_header(prev_header)
 181         bits, target = self.get_target(height/2016)
 182         _hash = self.hash_header(header)
 183         try:
 184             assert prev_hash == header.get('prev_block_hash')
 185             assert bits == header.get('bits')
 186             assert eval('0x'+_hash) < target
 187         except:
 188             # this can be caused by a reorg.
 189             print_error("verify header failed"+ repr(header))
 190             verifier.undo_verifications()
 191
 192             # return False to request previous header.
 193             return False
 194
 195         self.save_header(header)
 196         print_error("verify header:", _hash, height)
 197         return True
 198
 199
 200     def header_to_string(self, res):
 201         s = int_to_hex(res.get('version'),4) \
 202             + rev_hex(res.get('prev_block_hash')) \
 203             + rev_hex(res.get('merkle_root')) \
 204             + int_to_hex(int(res.get('timestamp')),4) \
 205             + int_to_hex(int(res.get('bits')),4) \
 206             + int_to_hex(int(res.get('nonce')),4)
 207         return s
 208
 209
 210     def header_from_string(self, s):
 211         hex_to_int = lambda s: eval('0x' + s[::-1].encode('hex'))
 212         h = {}
 213         h['version'] = hex_to_int(s[0:4])
 214         h['prev_block_hash'] = hash_encode(s[4:36])
 215         h['merkle_root'] = hash_encode(s[36:68])
 216         h['timestamp'] = hex_to_int(s[68:72])
 217         h['bits'] = hex_to_int(s[72:76])
 218         h['nonce'] = hex_to_int(s[76:80])
 219         return h
 220
 221     def hash_header(self, header):
 222         return rev_hex(Hash(self.header_to_string(header).decode('hex')).encode('hex'))
 223
 224     def path(self):
 225         return os.path.join( self.config.path, 'blockchain_headers')
 226
 227     def init_headers_file(self):
 228         filename = self.path()
 229         if os.path.exists(filename):
 230             return
 231
 232         try:
 233             import urllib, socket
 234             socket.setdefaulttimeout(30)
 235             print_error("downloading ", self.headers_url )
 236             urllib.urlretrieve(self.headers_url, filename)
 237         except:
 238             print_error( "download failed. creating file", filename )
 239             open(filename,'wb+').close()
 240
 241     def save_chunk(self, index, chunk):
 242         filename = self.path()
 243         f = open(filename,'rb+')
 244         f.seek(index*2016*80)
 245         h = f.write(chunk)
 246         f.close()
 247         self.set_local_height()
 248
 249     def save_header(self, header):
 250         data = self.header_to_string(header).decode('hex')
 251         assert len(data) == 80
 252         height = header.get('block_height')
 253         filename = self.path()
 254         f = open(filename,'rb+')
 255         f.seek(height*80)
 256         h = f.write(data)
 257         f.close()
 258         self.set_local_height()
 259
 260
 261     def set_local_height(self):
 262         name = self.path()
 263         if os.path.exists(name):
 264             h = os.path.getsize(name)/80 - 1
 265             if self.local_height != h:
 266                 self.local_height = h
 267                 self.height = self.local_height
 268
 269
 270     def read_header(self, block_height):
 271         name = self.path()
 272         if os.path.exists(name):
 273             f = open(name,'rb')
 274             f.seek(block_height*80)
 275             h = f.read(80)
 276             f.close()
 277             if len(h) == 80:
 278                 h = self.header_from_string(h)
 279                 return h
 280
 281
 282     def get_target(self, index):
 283
 284         max_target = 0x00000000FFFF0000000000000000000000000000000000000000000000000000
 285         if index == 0: return 0x1d00ffff, max_target
 286
 287         first = self.read_header((index-1)*2016)
 288         last = self.read_header(index*2016-1)
 289
 290         nActualTimespan = last.get('timestamp') - first.get('timestamp')
 291         nTargetTimespan = 14*24*60*60
 292         nActualTimespan = max(nActualTimespan, nTargetTimespan/4)
 293         nActualTimespan = min(nActualTimespan, nTargetTimespan*4)
 294
 295         bits = last.get('bits')
 296         # convert to bignum
 297         MM = 256*256*256
 298         a = bits%MM
 299         if a < 0x8000:
 300             a *= 256
 301         target = (a) * pow(2, 8 * (bits/MM - 3))
 302
 303         # new target
 304         new_target = min( max_target, (target * nActualTimespan)/nTargetTimespan )
 305
 306         # convert it to bits
 307         c = ("%064X"%new_target)[2:]
 308         i = 31
 309         while c[0:2]=="00":
 310             c = c[2:]
 311             i -= 1
 312
 313         c = eval('0x'+c[0:6])
 314         if c > 0x800000:
 315             c /= 256
 316             i += 1
 317
 318         new_bits = c + MM * i
 319         return new_bits, new_target
 320
 321
 322     def request_header(self, i, h, queue):
 323         print_error("requesting header %d from %s"%(h, i.server))
 324         i.send([ ('blockchain.block.get_header',[h])], lambda i,r: queue.put((i,r)))
 325
 326     def retrieve_header(self, i, queue):
 327         while True:
 328             try:
 329                 ir = queue.get(timeout=1)
 330             except Queue.Empty:
 331                 print_error('timeout')
 332                 continue
 333
 334             if not ir:
 335                 continue
 336
 337             i, r = ir
 338
 339             if r.get('error'):
 340                 print_error('Verifier received an error:', r)
 341                 continue
 342
 343             # 3. handle response
 344             method = r['method']
 345             params = r['params']
 346             result = r['result']
 347
 348             if method == 'blockchain.block.get_header':
 349                 return result
 350
 351
 352
 353     def get_chain(self, interface, final_header):
 354
 355         header = final_header
 356         chain = [ final_header ]
 357         requested_header = False
 358         queue = Queue.Queue()
 359
 360         while self.is_running():
 361
 362             if requested_header:
 363                 header = self.retrieve_header(interface, queue)
 364                 if not header: return
 365                 chain = [ header ] + chain
 366                 requested_header = False
 367
 368             height = header.get('block_height')
 369             previous_header = self.read_header(height -1)
 370             if not previous_header:
 371                 self.request_header(interface, height - 1, queue)
 372                 requested_header = True
 373                 continue
 374
 375             # verify that it connects to my chain
 376             prev_hash = self.hash_header(previous_header)
 377             if prev_hash != header.get('prev_block_hash'):
 378                 print_error("reorg")
 379                 self.request_header(interface, height - 1, queue)
 380                 requested_header = True
 381                 continue
 382
 383             else:
 384                 # the chain is complete
 385                 return chain
 386
 387
 388     def get_chunks(self, i, header, height):
 389         requested_chunks = []
 390         queue = Queue.Queue()
 391         min_index = (self.local_height + 1)/2016
 392         max_index = (height + 1)/2016
 393         for n in range(min_index, max_index + 1):
 394             print_error( "requesting chunk", n )
 395             i.send([ ('blockchain.block.get_chunk',[n])], lambda i,r:queue.put(r))
 396             requested_chunks.append(n)
 397             break
 398
 399         while requested_chunks:
 400             try:
 401                 r = queue.get(timeout=1)
 402             except Queue.Empty:
 403                 continue
 404             if not r: continue
 405
 406             if r.get('error'):
 407                 print_error('Verifier received an error:', r)
 408                 continue
 409
 410             # 3. handle response
 411             params = r['params']
 412             result = r['result']
 413
 414             index = params[0]
 415             self.verify_chunk(index, result)
 416             requested_chunks.remove(index)
 417
 418
 419
 420
 421
 422
 423