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