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_tx3',{})      # 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://headers.electrum.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.verified_tx:
  53                 height, timestamp, pos = self.verified_tx[tx]
  54                 conf = (self.local_height - height + 1)
  55             else:
  56                 conf = 0
  57
  58             if conf <= 0:
  59                 timestamp = None
  60
  61         return conf, timestamp
  62
  63
  64     def get_height(self, tx_hash):
  65         with self.lock:
  66             v = self.verified_tx.get(tx_hash)
  67         height = v[0] if v else None
  68         return height
  69
  70
  71     def add(self, tx_hash, tx_height):
  72         """ add a transaction to the list of monitored transactions. """
  73         assert tx_height > 0
  74         with self.lock:
  75             if tx_hash not in self.transactions.keys():
  76                 self.transactions[tx_hash] = tx_height
  77
  78     def stop(self):
  79         with self.lock: self.running = False
  80         self.interface.poke('verifier')
  81
  82     def is_running(self):
  83         with self.lock: return self.running
  84
  85     def run(self):
  86
  87         self.init_headers_file()
  88         self.set_local_height()
  89
  90         with self.lock:
  91             self.running = True
  92         requested_merkle = []
  93         requested_chunks = []
  94         requested_headers = []
  95         all_chunks = False
  96
  97         # subscribe to block headers
  98         self.interface.send([ ('blockchain.headers.subscribe',[])], 'verifier')
  99
 100         while self.is_running():
 101             # request missing chunks
 102             if not all_chunks and self.height and not requested_chunks:
 103
 104                 if self.local_height + 50 < self.height:
 105                     min_index = (self.local_height + 1)/2016
 106                     max_index = (self.height + 1)/2016
 107                     for i in range(min_index, max_index + 1):
 108                         print_error( "requesting chunk", i )
 109                         self.interface.send([ ('blockchain.block.get_chunk',[i])], 'verifier')
 110                         requested_chunks.append(i)
 111                         break
 112                 else:
 113                     all_chunks = True
 114                     print_error("downloaded all chunks")
 115
 116             # request missing tx
 117             if all_chunks:
 118                 for tx_hash, tx_height in self.transactions.items():
 119                     if tx_hash not in self.verified_tx:
 120                         if self.merkle_roots.get(tx_hash) is None and tx_hash not in requested_merkle:
 121                             print_error('requesting merkle', tx_hash)
 122                             self.interface.send([ ('blockchain.transaction.get_merkle',[tx_hash, tx_height]) ], 'verifier')
 123                             requested_merkle.append(tx_hash)
 124
 125             # process pending headers
 126             if self.pending_headers and all_chunks:
 127                 done = []
 128                 for header in self.pending_headers:
 129                     if self.verify_header(header):
 130                         done.append(header)
 131                     else:
 132                         # request previous header
 133                         i = header.get('block_height') - 1
 134                         if i not in requested_headers:
 135                             print_error("requesting header %d"%i)
 136                             self.interface.send([ ('blockchain.block.get_header',[i])], 'verifier')
 137                             requested_headers.append(i)
 138                         # no point continuing
 139                         break
 140                 if done:
 141                     self.interface.trigger_callback('updated')
 142                     for header in done:
 143                         self.pending_headers.remove(header)
 144
 145             try:
 146                 r = self.interface.get_response('verifier',timeout=1)
 147             except Queue.Empty:
 148                 continue
 149             if not r: continue
 150
 151             if r.get('error'):
 152                 print_error('Verifier received an error:', r)
 153                 continue
 154
 155             # 3. handle response
 156             method = r['method']
 157             params = r['params']
 158             result = r['result']
 159
 160             if method == 'blockchain.transaction.get_merkle':
 161                 tx_hash = params[0]
 162                 self.verify_merkle(tx_hash, result)
 163                 requested_merkle.remove(tx_hash)
 164
 165             elif method == 'blockchain.block.get_chunk':
 166                 index = params[0]
 167                 self.verify_chunk(index, result)
 168                 requested_chunks.remove(index)
 169
 170             elif method in ['blockchain.headers.subscribe', 'blockchain.block.get_header']:
 171
 172                 self.pending_headers.append(result)
 173                 if method == 'blockchain.block.get_header':
 174                     requested_headers.remove(result.get('block_height'))
 175                 else:
 176                     self.height = result.get('block_height')
 177                     self.interface.poke('synchronizer')
 178
 179                 self.pending_headers.sort(key=lambda x: x.get('block_height'))
 180                 # print "pending headers", map(lambda x: x.get('block_height'), self.pending_headers)
 181
 182
 183
 184     def verify_merkle(self, tx_hash, result):
 185         tx_height = result.get('block_height')
 186         pos = result.get('pos')
 187         self.merkle_roots[tx_hash] = self.hash_merkle_root(result['merkle'], tx_hash, pos)
 188         header = self.read_header(tx_height)
 189         if not header: return
 190         assert header.get('merkle_root') == self.merkle_roots[tx_hash]
 191         # we passed all the tests
 192         header = self.read_header(tx_height)
 193         timestamp = header.get('timestamp')
 194         with self.lock:
 195             self.verified_tx[tx_hash] = (tx_height, timestamp, pos)
 196         print_error("verified %s"%tx_hash)
 197         self.config.set_key('verified_tx3', self.verified_tx, True)
 198         self.interface.trigger_callback('updated')
 199
 200
 201     def verify_chunk(self, index, hexdata):
 202         data = hexdata.decode('hex')
 203         height = index*2016
 204         num = len(data)/80
 205         print_error("validating headers %d"%height)
 206
 207         if index == 0:
 208             previous_hash = ("0"*64)
 209         else:
 210             prev_header = self.read_header(index*2016-1)
 211             if prev_header is None: raise
 212             previous_hash = self.hash_header(prev_header)
 213
 214         bits, target = self.get_target(index)
 215
 216         for i in range(num):
 217             height = index*2016 + i
 218             raw_header = data[i*80:(i+1)*80]
 219             header = self.header_from_string(raw_header)
 220             _hash = self.hash_header(header)
 221             assert previous_hash == header.get('prev_block_hash')
 222             assert bits == header.get('bits')
 223             assert eval('0x'+_hash) < target
 224
 225             previous_header = header
 226             previous_hash = _hash
 227
 228         self.save_chunk(index, data)
 229
 230
 231     def verify_header(self, header):
 232         # add header to the blockchain file
 233         # if there is a reorg, push it in a stack
 234
 235         height = header.get('block_height')
 236
 237         prev_header = self.read_header(height -1)
 238         if not prev_header:
 239             # return False to request previous header
 240             return False
 241
 242         prev_hash = self.hash_header(prev_header)
 243         bits, target = self.get_target(height/2016)
 244         _hash = self.hash_header(header)
 245         try:
 246             assert prev_hash == header.get('prev_block_hash')
 247             assert bits == header.get('bits')
 248             assert eval('0x'+_hash) < target
 249         except:
 250             # this can be caused by a reorg.
 251             print_error("verify header failed"+ repr(header))
 252             # undo verifications
 253             with self.lock:
 254                 items = self.verified_tx.items()[:]
 255             for tx_hash, item in items:
 256                 tx_height, timestamp = item
 257                 if tx_height >= height:
 258                     print_error("redoing", tx_hash)
 259                     with self.lock:
 260                         self.verified_tx.pop(tx_hash)
 261                         if tx_hash in self.merkle_roots:
 262                             self.merkle_roots.pop(tx_hash)
 263             # return False to request previous header.
 264             return False
 265
 266         self.save_header(header)
 267         print_error("verify header:", _hash, height)
 268         return True
 269
 270
 271
 272
 273     def header_to_string(self, res):
 274         s = int_to_hex(res.get('version'),4) \
 275             + rev_hex(res.get('prev_block_hash')) \
 276             + rev_hex(res.get('merkle_root')) \
 277             + int_to_hex(int(res.get('timestamp')),4) \
 278             + int_to_hex(int(res.get('bits')),4) \
 279             + int_to_hex(int(res.get('nonce')),4)
 280         return s
 281
 282
 283     def header_from_string(self, s):
 284         hex_to_int = lambda s: eval('0x' + s[::-1].encode('hex'))
 285         h = {}
 286         h['version'] = hex_to_int(s[0:4])
 287         h['prev_block_hash'] = hash_encode(s[4:36])
 288         h['merkle_root'] = hash_encode(s[36:68])
 289         h['timestamp'] = hex_to_int(s[68:72])
 290         h['bits'] = hex_to_int(s[72:76])
 291         h['nonce'] = hex_to_int(s[76:80])
 292         return h
 293
 294     def hash_header(self, header):
 295         return rev_hex(Hash(self.header_to_string(header).decode('hex')).encode('hex'))
 296
 297     def hash_merkle_root(self, merkle_s, target_hash, pos):
 298         h = hash_decode(target_hash)
 299         for i in range(len(merkle_s)):
 300             item = merkle_s[i]
 301             h = Hash( hash_decode(item) + h ) if ((pos >> i) & 1) else Hash( h + hash_decode(item) )
 302         return hash_encode(h)
 303
 304     def path(self):
 305         wdir = self.config.get('blockchain_headers_path', user_dir())
 306         if wdir and not os.path.exists( wdir ): os.mkdir(wdir)
 307         return os.path.join( wdir, 'blockchain_headers')
 308
 309     def init_headers_file(self):
 310         filename = self.path()
 311         if os.path.exists(filename):
 312             return
 313
 314         try:
 315             import urllib, socket
 316             socket.setdefaulttimeout(30)
 317             print_error("downloading ", self.headers_url )
 318             urllib.urlretrieve(self.headers_url, filename)
 319         except:
 320             print_error( "download failed. creating file", filename )
 321             open(filename,'wb+').close()
 322
 323     def save_chunk(self, index, chunk):
 324         filename = self.path()
 325         f = open(filename,'rb+')
 326         f.seek(index*2016*80)
 327         h = f.write(chunk)
 328         f.close()
 329         self.set_local_height()
 330
 331     def save_header(self, header):
 332         data = self.header_to_string(header).decode('hex')
 333         assert len(data) == 80
 334         height = header.get('block_height')
 335         filename = self.path()
 336         f = open(filename,'rb+')
 337         f.seek(height*80)
 338         h = f.write(data)
 339         f.close()
 340         self.set_local_height()
 341
 342
 343     def set_local_height(self):
 344         name = self.path()
 345         if os.path.exists(name):
 346             h = os.path.getsize(name)/80 - 1
 347             if self.local_height != h:
 348                 self.local_height = h
 349
 350
 351     def read_header(self, block_height):
 352         name = self.path()
 353         if os.path.exists(name):
 354             f = open(name,'rb')
 355             f.seek(block_height*80)
 356             h = f.read(80)
 357             f.close()
 358             if len(h) == 80:
 359                 h = self.header_from_string(h)
 360                 return h
 361
 362
 363     def get_target(self, index):
 364
 365         max_target = 0x00000000FFFF0000000000000000000000000000000000000000000000000000
 366         if index == 0: return 0x1d00ffff, max_target
 367
 368         first = self.read_header((index-1)*2016)
 369         last = self.read_header(index*2016-1)
 370
 371         nActualTimespan = last.get('timestamp') - first.get('timestamp')
 372         nTargetTimespan = 14*24*60*60
 373         nActualTimespan = max(nActualTimespan, nTargetTimespan/4)
 374         nActualTimespan = min(nActualTimespan, nTargetTimespan*4)
 375
 376         bits = last.get('bits')
 377         # convert to bignum
 378         MM = 256*256*256
 379         a = bits%MM
 380         if a < 0x8000:
 381             a *= 256
 382         target = (a) * pow(2, 8 * (bits/MM - 3))
 383
 384         # new target
 385         new_target = min( max_target, (target * nActualTimespan)/nTargetTimespan )
 386
 387         # convert it to bits
 388         c = ("%064X"%new_target)[2:]
 389         i = 31
 390         while c[0:2]=="00":
 391             c = c[2:]
 392             i -= 1
 393
 394         c = eval('0x'+c[0:6])
 395         if c > 0x800000:
 396             c /= 256
 397             i += 1
 398
 399         new_bits = c + MM * i
 400         return new_bits, new_target
 401