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