lib/verifier.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
  26
  27 class WalletVerifier(threading.Thread):
  28     """ Simple Payment Verification """
  29
  30     def __init__(self, interface, config):
  31         threading.Thread.__init__(self)
  32         self.daemon = True
  33         self.config = config
  34         self.interface = interface
  35         self.transactions    = {}                                 # requested verifications (with height sent by the requestor)
  36         self.interface.register_channel('verifier')
  37
  38         self.verified_tx     = config.get('verified_tx2',{})      # height, timestamp of verified transactions
  39         self.merkle_roots    = config.get('merkle_roots',{})      # hashed by me
  40
  41         self.targets         = config.get('targets',{})           # compute targets
  42         self.lock = threading.Lock()
  43         self.pending_headers = [] # headers that have not been verified
  44         self.height = 0
  45         self.local_height = 0
  46         self.running = False
  47         self.headers_url = 'http://images.ecdsa.org/blockchain_headers'
  48
  49     def get_confirmations(self, tx):
  50         """ return the number of confirmations of a monitored transaction. """
  51         with self.lock:
  52             if tx in self.transactions.keys():
  53                 if tx in self.verified_tx:
  54                     height, timestamp = self.verified_tx[tx]
  55                     conf = (self.local_height - height + 1)
  56                 else:
  57                     conf = -1
  58             else:
  59                 #print "verifier: tx not in list", tx
  60                 conf = 0
  61
  62             if conf <= 0:
  63                 timestamp = None
  64
  65         return conf, timestamp
  66
  67
  68     def add(self, tx_hash, tx_height):
  69         """ add a transaction to the list of monitored transactions. """
  70         assert tx_height > 0
  71         with self.lock:
  72             if tx_hash not in self.transactions.keys():
  73                 self.transactions[tx_hash] = tx_height
  74
  75     def stop(self):
  76         with self.lock: self.running = False
  77         self.interface.poke('verifier')
  78
  79     def is_running(self):
  80         with self.lock: return self.running
  81
  82     def run(self):
  83
  84         self.init_headers_file()
  85         self.set_local_height()
  86
  87         with self.lock:
  88             self.running = True
  89         requested_merkle = []
  90         requested_chunks = []
  91         requested_headers = []
  92         all_chunks = False
  93
  94         # subscribe to block headers
  95         self.interface.send([ ('blockchain.headers.subscribe',[])], 'verifier')
  96
  97         while self.is_running():
  98             # request missing chunks
  99             if not all_chunks and self.height and not requested_chunks:
 100
 101                 if self.local_height + 50 < self.height:
 102                     min_index = (self.local_height + 1)/2016
 103                     max_index = (self.height + 1)/2016
 104                     for i in range(min_index, max_index + 1):
 105                         print_error( "requesting chunk", i )
 106                         self.interface.send([ ('blockchain.block.get_chunk',[i])], 'verifier')
 107                         requested_chunks.append(i)
 108                         break
 109                 else:
 110                     all_chunks = True
 111                     print_error("downloaded all chunks")
 112
 113             # request missing tx
 114             if all_chunks:
 115                 for tx_hash, tx_height in self.transactions.items():
 116                     if tx_hash not in self.verified_tx:
 117                         if self.merkle_roots.get(tx_hash) is None and tx_hash not in requested_merkle:
 118                             print_error('requesting merkle', tx_hash)
 119                             self.interface.send([ ('blockchain.transaction.get_merkle',[tx_hash, tx_height]) ], 'verifier')
 120                             requested_merkle.append(tx_hash)
 121
 122             # process pending headers
 123             if self.pending_headers and all_chunks:
 124                 done = []
 125                 for header in self.pending_headers:
 126                     if self.verify_header(header):
 127                         done.append(header)
 128                     else:
 129                         # request previous header
 130                         i = header.get('block_height') - 1
 131                         if i not in requested_headers:
 132                             print_error("requesting header %d"%i)
 133                             self.interface.send([ ('blockchain.block.get_header',[i])], 'verifier')
 134                             requested_headers.append(i)
 135                         # no point continuing
 136                         break
 137                 if done:
 138                     self.interface.trigger_callback('updated')
 139                     for header in done:
 140                         self.pending_headers.remove(header)
 141
 142             try:
 143                 r = self.interface.get_response('verifier',timeout=1)
 144             except Queue.Empty:
 145                 continue
 146             if not r: continue
 147
 148             # 3. handle response
 149             method = r['method']
 150             params = r['params']
 151             result = r['result']
 152
 153             if method == 'blockchain.transaction.get_merkle':
 154                 tx_hash = params[0]
 155                 self.verify_merkle(tx_hash, result)
 156                 requested_merkle.remove(tx_hash)
 157
 158             elif method == 'blockchain.block.get_chunk':
 159                 index = params[0]
 160                 self.verify_chunk(index, result)
 161                 requested_chunks.remove(index)
 162
 163             elif method in ['blockchain.headers.subscribe', 'blockchain.block.get_header']:
 164
 165                 self.pending_headers.append(result)
 166                 if method == 'blockchain.block.get_header':
 167                     requested_headers.remove(result.get('block_height'))
 168                 else:
 169                     self.height = result.get('block_height')
 170
 171                 self.pending_headers.sort(key=lambda x: x.get('block_height'))
 172                 # print "pending headers", map(lambda x: x.get('block_height'), self.pending_headers)
 173
 174
 175
 176     def verify_merkle(self, tx_hash, result):
 177         tx_height = result.get('block_height')
 178         self.merkle_roots[tx_hash] = self.hash_merkle_root(result['merkle'], tx_hash, result.get('pos'))
 179         header = self.read_header(tx_height)
 180         if not header: return
 181         assert header.get('merkle_root') == self.merkle_roots[tx_hash]
 182         # we passed all the tests
 183         header = self.read_header(tx_height)
 184         timestamp = header.get('timestamp')
 185         self.verified_tx[tx_hash] = (tx_height, timestamp)
 186         print_error("verified %s"%tx_hash)
 187         self.config.set_key('verified_tx2', self.verified_tx, True)
 188         self.interface.trigger_callback('updated')
 189
 190
 191     def verify_chunk(self, index, hexdata):
 192         data = hexdata.decode('hex')
 193         height = index*2016
 194         num = len(data)/80
 195         print_error("validating headers %d"%height)
 196
 197         if index == 0:
 198             previous_hash = ("0"*64)
 199         else:
 200             prev_header = self.read_header(index*2016-1)
 201             if prev_header is None: raise
 202             previous_hash = self.hash_header(prev_header)
 203
 204         bits, target = self.get_target(index)
 205
 206         for i in range(num):
 207             height = index*2016 + i
 208             raw_header = data[i*80:(i+1)*80]
 209             header = self.header_from_string(raw_header)
 210             _hash = self.hash_header(header)
 211             assert previous_hash == header.get('prev_block_hash')
 212             assert bits == header.get('bits')
 213             assert eval('0x'+_hash) < target
 214
 215             previous_header = header
 216             previous_hash = _hash
 217
 218         self.save_chunk(index, data)
 219
 220
 221     def verify_header(self, header):
 222         # add header to the blockchain file
 223         # if there is a reorg, push it in a stack
 224
 225         height = header.get('block_height')
 226
 227         prev_header = self.read_header(height -1)
 228         if not prev_header:
 229             # return False to request previous header
 230             return False
 231
 232         prev_hash = self.hash_header(prev_header)
 233         bits, target = self.get_target(height/2016)
 234         _hash = self.hash_header(header)
 235         try:
 236             assert prev_hash == header.get('prev_block_hash')
 237             assert bits == header.get('bits')
 238             assert eval('0x'+_hash) < target
 239         except:
 240             # this can be caused by a reorg.
 241             print_error("verify header failed"+ repr(header))
 242             # undo verifications
 243             for tx_hash, item in self.verified_tx.items():
 244                 tx_height, timestamp = item
 245                 if tx_height >= height:
 246                     print_error("redoing", tx_hash)
 247                     self.verified_tx.pop(tx_hash)
 248                     if tx_hash in self.merkle_roots: self.merkle_roots.pop(tx_hash)
 249             # return False to request previous header.
 250             return False
 251
 252         self.save_header(header)
 253         print_error("verify header:", _hash, height)
 254         return True
 255
 256
 257
 258
 259     def header_to_string(self, res):
 260         s = int_to_hex(res.get('version'),4) \
 261             + rev_hex(res.get('prev_block_hash')) \
 262             + rev_hex(res.get('merkle_root')) \
 263             + int_to_hex(int(res.get('timestamp')),4) \
 264             + int_to_hex(int(res.get('bits')),4) \
 265             + int_to_hex(int(res.get('nonce')),4)
 266         return s
 267
 268
 269     def header_from_string(self, s):
 270         hex_to_int = lambda s: eval('0x' + s[::-1].encode('hex'))
 271         h = {}
 272         h['version'] = hex_to_int(s[0:4])
 273         h['prev_block_hash'] = hash_encode(s[4:36])
 274         h['merkle_root'] = hash_encode(s[36:68])
 275         h['timestamp'] = hex_to_int(s[68:72])
 276         h['bits'] = hex_to_int(s[72:76])
 277         h['nonce'] = hex_to_int(s[76:80])
 278         return h
 279
 280     def hash_header(self, header):
 281         return rev_hex(Hash(self.header_to_string(header).decode('hex')).encode('hex'))
 282
 283     def hash_merkle_root(self, merkle_s, target_hash, pos):
 284         h = hash_decode(target_hash)
 285         for i in range(len(merkle_s)):
 286             item = merkle_s[i]
 287             h = Hash( hash_decode(item) + h ) if ((pos >> i) & 1) else Hash( h + hash_decode(item) )
 288         return hash_encode(h)
 289
 290     def path(self):
 291         wdir = self.config.get('blockchain_headers_path', user_dir())
 292         if wdir and not os.path.exists( wdir ): os.mkdir(wdir)
 293         return os.path.join( wdir, 'blockchain_headers')
 294
 295     def init_headers_file(self):
 296         filename = self.path()
 297         if os.path.exists(filename):
 298             return
 299         import urllib2
 300         try:
 301             print_error("downloading ", self.headers_url )
 302             f = urllib2.urlopen(self.headers_url)
 303             s = f.read()
 304             f.close()
 305             f = open(filename,'wb+')
 306             f.write(s)
 307             f.close()
 308         except:
 309             print_error( "download failed. creating file", filename )
 310             open(filename,'wb+').close()
 311
 312     def save_chunk(self, index, chunk):
 313         filename = self.path()
 314         f = open(filename,'rb+')
 315         f.seek(index*2016*80)
 316         h = f.write(chunk)
 317         f.close()
 318         self.set_local_height()
 319
 320     def save_header(self, header):
 321         data = self.header_to_string(header).decode('hex')
 322         assert len(data) == 80
 323         height = header.get('block_height')
 324         filename = self.path()
 325         f = open(filename,'rb+')
 326         f.seek(height*80)
 327         h = f.write(data)
 328         f.close()
 329         self.set_local_height()
 330
 331
 332     def set_local_height(self):
 333         name = self.path()
 334         if os.path.exists(name):
 335             h = os.path.getsize(name)/80 - 1
 336             if self.local_height != h:
 337                 self.local_height = h
 338
 339
 340     def read_header(self, block_height):
 341         name = self.path()
 342         if os.path.exists(name):
 343             f = open(name,'rb')
 344             f.seek(block_height*80)
 345             h = f.read(80)
 346             f.close()
 347             if len(h) == 80:
 348                 h = self.header_from_string(h)
 349                 return h
 350
 351
 352     def get_target(self, index):
 353
 354         max_target = 0x00000000FFFF0000000000000000000000000000000000000000000000000000
 355         if index == 0: return 0x1d00ffff, max_target
 356
 357         first = self.read_header((index-1)*2016)
 358         last = self.read_header(index*2016-1)
 359
 360         nActualTimespan = last.get('timestamp') - first.get('timestamp')
 361         nTargetTimespan = 14*24*60*60
 362         nActualTimespan = max(nActualTimespan, nTargetTimespan/4)
 363         nActualTimespan = min(nActualTimespan, nTargetTimespan*4)
 364
 365         bits = last.get('bits')
 366         # convert to bignum
 367         MM = 256*256*256
 368         a = bits%MM
 369         if a < 0x8000:
 370             a *= 256
 371         target = (a) * pow(2, 8 * (bits/MM - 3))
 372
 373         # new target
 374         new_target = min( max_target, (target * nActualTimespan)/nTargetTimespan )
 375
 376         # convert it to bits
 377         c = ("%064X"%new_target)[2:]
 378         i = 31
 379         while c[0:2]=="00":
 380             c = c[2:]
 381             i -= 1
 382
 383         c = eval('0x'+c[0:6])
 384         if c > 0x800000:
 385             c /= 256
 386             i += 1
 387
 388         new_bits = c + MM * i
 389         return new_bits, new_target
 390