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                 if conf <= 0: timestamp = None
  56
  57             elif tx in self.transactions:
  58                 conf = -1
  59                 timestamp = None
  60
  61             else:
  62                 conf = 0
  63                 timestamp = None
  64
  65         return conf, timestamp
  66
  67
  68     def get_txpos(self, tx_hash):
  69         "return position, even if the tx is unverified"
  70         with self.lock:
  71             x = self.verified_tx.get(tx_hash)
  72             y = self.transactions.get(tx_hash)
  73         if x:
  74             height, timestamp, pos = x
  75             return height, pos
  76         elif y:
  77             return y, 0
  78         else:
  79             return 1e12, 0
  80
  81
  82     def get_height(self, tx_hash):
  83         with self.lock:
  84             v = self.verified_tx.get(tx_hash)
  85         height = v[0] if v else None
  86         return height
  87
  88
  89     def add(self, tx_hash, tx_height):
  90         """ add a transaction to the list of monitored transactions. """
  91         assert tx_height > 0
  92         with self.lock:
  93             if tx_hash not in self.transactions.keys():
  94                 self.transactions[tx_hash] = tx_height
  95
  96     def stop(self):
  97         with self.lock: self.running = False
  98         self.interface.poke('verifier')
  99
 100     def is_running(self):
 101         with self.lock: return self.running
 102
 103     def run(self):
 104
 105         self.init_headers_file()
 106         self.set_local_height()
 107
 108         with self.lock:
 109             self.running = True
 110         requested_merkle = []
 111         requested_chunks = []
 112         requested_headers = []
 113         all_chunks = False
 114
 115         # subscribe to block headers
 116         self.interface.send([ ('blockchain.headers.subscribe',[])], 'verifier')
 117
 118         while self.is_running():
 119             # request missing chunks
 120             if not all_chunks and self.height and not requested_chunks:
 121
 122                 if self.local_height + 50 < self.height:
 123                     min_index = (self.local_height + 1)/2016
 124                     max_index = (self.height + 1)/2016
 125                     for i in range(min_index, max_index + 1):
 126                         print_error( "requesting chunk", i )
 127                         self.interface.send([ ('blockchain.block.get_chunk',[i])], 'verifier')
 128                         requested_chunks.append(i)
 129                         break
 130                 else:
 131                     all_chunks = True
 132                     print_error("downloaded all chunks")
 133
 134             # request missing tx
 135             if all_chunks:
 136                 for tx_hash, tx_height in self.transactions.items():
 137                     if tx_hash not in self.verified_tx:
 138                         if self.merkle_roots.get(tx_hash) is None and tx_hash not in requested_merkle:
 139                             print_error('requesting merkle', tx_hash)
 140                             self.interface.send([ ('blockchain.transaction.get_merkle',[tx_hash, tx_height]) ], 'verifier')
 141                             requested_merkle.append(tx_hash)
 142
 143             # process pending headers
 144             if self.pending_headers and all_chunks:
 145                 done = []
 146                 for header in self.pending_headers:
 147                     if self.verify_header(header):
 148                         done.append(header)
 149                     else:
 150                         # request previous header
 151                         i = header.get('block_height') - 1
 152                         if i not in requested_headers:
 153                             print_error("requesting header %d"%i)
 154                             self.interface.send([ ('blockchain.block.get_header',[i])], 'verifier')
 155                             requested_headers.append(i)
 156                         # no point continuing
 157                         break
 158                 if done:
 159                     self.interface.trigger_callback('updated')
 160                     for header in done:
 161                         self.pending_headers.remove(header)
 162
 163             try:
 164                 r = self.interface.get_response('verifier',timeout=1)
 165             except Queue.Empty:
 166                 continue
 167             if not r: continue
 168
 169             if r.get('error'):
 170                 print_error('Verifier received an error:', r)
 171                 continue
 172
 173             # 3. handle response
 174             method = r['method']
 175             params = r['params']
 176             result = r['result']
 177
 178             if method == 'blockchain.transaction.get_merkle':
 179                 tx_hash = params[0]
 180                 self.verify_merkle(tx_hash, result)
 181                 requested_merkle.remove(tx_hash)
 182
 183             elif method == 'blockchain.block.get_chunk':
 184                 index = params[0]
 185                 self.verify_chunk(index, result)
 186                 requested_chunks.remove(index)
 187
 188             elif method in ['blockchain.headers.subscribe', 'blockchain.block.get_header']:
 189
 190                 self.pending_headers.append(result)
 191                 if method == 'blockchain.block.get_header':
 192                     requested_headers.remove(result.get('block_height'))
 193                 else:
 194                     self.height = result.get('block_height')
 195                     self.interface.poke('synchronizer')
 196
 197                 self.pending_headers.sort(key=lambda x: x.get('block_height'))
 198                 # print "pending headers", map(lambda x: x.get('block_height'), self.pending_headers)
 199
 200
 201
 202     def verify_merkle(self, tx_hash, result):
 203         tx_height = result.get('block_height')
 204         pos = result.get('pos')
 205         self.merkle_roots[tx_hash] = self.hash_merkle_root(result['merkle'], tx_hash, pos)
 206         header = self.read_header(tx_height)
 207         if not header: return
 208         assert header.get('merkle_root') == self.merkle_roots[tx_hash]
 209         # we passed all the tests
 210         header = self.read_header(tx_height)
 211         timestamp = header.get('timestamp')
 212         with self.lock:
 213             self.verified_tx[tx_hash] = (tx_height, timestamp, pos)
 214         print_error("verified %s"%tx_hash)
 215         self.config.set_key('verified_tx3', self.verified_tx, True)
 216         self.interface.trigger_callback('updated')
 217
 218
 219     def verify_chunk(self, index, hexdata):
 220         data = hexdata.decode('hex')
 221         height = index*2016
 222         num = len(data)/80
 223         print_error("validating headers %d"%height)
 224
 225         if index == 0:
 226             previous_hash = ("0"*64)
 227         else:
 228             prev_header = self.read_header(index*2016-1)
 229             if prev_header is None: raise
 230             previous_hash = self.hash_header(prev_header)
 231
 232         bits, target = self.get_target(index)
 233
 234         for i in range(num):
 235             height = index*2016 + i
 236             raw_header = data[i*80:(i+1)*80]
 237             header = self.header_from_string(raw_header)
 238             _hash = self.hash_header(header)
 239             assert previous_hash == header.get('prev_block_hash')
 240             assert bits == header.get('bits')
 241             assert eval('0x'+_hash) < target
 242
 243             previous_header = header
 244             previous_hash = _hash
 245
 246         self.save_chunk(index, data)
 247
 248
 249     def verify_header(self, header):
 250         # add header to the blockchain file
 251         # if there is a reorg, push it in a stack
 252
 253         height = header.get('block_height')
 254
 255         prev_header = self.read_header(height -1)
 256         if not prev_header:
 257             # return False to request previous header
 258             return False
 259
 260         prev_hash = self.hash_header(prev_header)
 261         bits, target = self.get_target(height/2016)
 262         _hash = self.hash_header(header)
 263         try:
 264             assert prev_hash == header.get('prev_block_hash')
 265             assert bits == header.get('bits')
 266             assert eval('0x'+_hash) < target
 267         except:
 268             # this can be caused by a reorg.
 269             print_error("verify header failed"+ repr(header))
 270             # undo verifications
 271             with self.lock:
 272                 items = self.verified_tx.items()[:]
 273             for tx_hash, item in items:
 274                 tx_height, timestamp, pos = item
 275                 if tx_height >= height:
 276                     print_error("redoing", tx_hash)
 277                     with self.lock:
 278                         self.verified_tx.pop(tx_hash)
 279                         if tx_hash in self.merkle_roots:
 280                             self.merkle_roots.pop(tx_hash)
 281             # return False to request previous header.
 282             return False
 283
 284         self.save_header(header)
 285         print_error("verify header:", _hash, height)
 286         return True
 287
 288
 289
 290
 291     def header_to_string(self, res):
 292         s = int_to_hex(res.get('version'),4) \
 293             + rev_hex(res.get('prev_block_hash')) \
 294             + rev_hex(res.get('merkle_root')) \
 295             + int_to_hex(int(res.get('timestamp')),4) \
 296             + int_to_hex(int(res.get('bits')),4) \
 297             + int_to_hex(int(res.get('nonce')),4)
 298         return s
 299
 300
 301     def header_from_string(self, s):
 302         hex_to_int = lambda s: eval('0x' + s[::-1].encode('hex'))
 303         h = {}
 304         h['version'] = hex_to_int(s[0:4])
 305         h['prev_block_hash'] = hash_encode(s[4:36])
 306         h['merkle_root'] = hash_encode(s[36:68])
 307         h['timestamp'] = hex_to_int(s[68:72])
 308         h['bits'] = hex_to_int(s[72:76])
 309         h['nonce'] = hex_to_int(s[76:80])
 310         return h
 311
 312     def hash_header(self, header):
 313         return rev_hex(Hash(self.header_to_string(header).decode('hex')).encode('hex'))
 314
 315     def hash_merkle_root(self, merkle_s, target_hash, pos):
 316         h = hash_decode(target_hash)
 317         for i in range(len(merkle_s)):
 318             item = merkle_s[i]
 319             h = Hash( hash_decode(item) + h ) if ((pos >> i) & 1) else Hash( h + hash_decode(item) )
 320         return hash_encode(h)
 321
 322     def path(self):
 323         wdir = self.config.get('blockchain_headers_path', user_dir())
 324         if wdir and not os.path.exists( wdir ): os.mkdir(wdir)
 325         return os.path.join( wdir, 'blockchain_headers')
 326
 327     def init_headers_file(self):
 328         filename = self.path()
 329         if os.path.exists(filename):
 330             return
 331
 332         try:
 333             import urllib, socket
 334             socket.setdefaulttimeout(30)
 335             print_error("downloading ", self.headers_url )
 336             urllib.urlretrieve(self.headers_url, filename)
 337         except:
 338             print_error( "download failed. creating file", filename )
 339             open(filename,'wb+').close()
 340
 341     def save_chunk(self, index, chunk):
 342         filename = self.path()
 343         f = open(filename,'rb+')
 344         f.seek(index*2016*80)
 345         h = f.write(chunk)
 346         f.close()
 347         self.set_local_height()
 348
 349     def save_header(self, header):
 350         data = self.header_to_string(header).decode('hex')
 351         assert len(data) == 80
 352         height = header.get('block_height')
 353         filename = self.path()
 354         f = open(filename,'rb+')
 355         f.seek(height*80)
 356         h = f.write(data)
 357         f.close()
 358         self.set_local_height()
 359
 360
 361     def set_local_height(self):
 362         name = self.path()
 363         if os.path.exists(name):
 364             h = os.path.getsize(name)/80 - 1
 365             if self.local_height != h:
 366                 self.local_height = h
 367
 368
 369     def read_header(self, block_height):
 370         name = self.path()
 371         if os.path.exists(name):
 372             f = open(name,'rb')
 373             f.seek(block_height*80)
 374             h = f.read(80)
 375             f.close()
 376             if len(h) == 80:
 377                 h = self.header_from_string(h)
 378                 return h
 379
 380
 381     def get_target(self, index):
 382
 383         max_target = 0x00000000FFFF0000000000000000000000000000000000000000000000000000
 384         if index == 0: return 0x1d00ffff, max_target
 385
 386         first = self.read_header((index-1)*2016)
 387         last = self.read_header(index*2016-1)
 388
 389         nActualTimespan = last.get('timestamp') - first.get('timestamp')
 390         nTargetTimespan = 14*24*60*60
 391         nActualTimespan = max(nActualTimespan, nTargetTimespan/4)
 392         nActualTimespan = min(nActualTimespan, nTargetTimespan*4)
 393
 394         bits = last.get('bits')
 395         # convert to bignum
 396         MM = 256*256*256
 397         a = bits%MM
 398         if a < 0x8000:
 399             a *= 256
 400         target = (a) * pow(2, 8 * (bits/MM - 3))
 401
 402         # new target
 403         new_target = min( max_target, (target * nActualTimespan)/nTargetTimespan )
 404
 405         # convert it to bits
 406         c = ("%064X"%new_target)[2:]
 407         i = 31
 408         while c[0:2]=="00":
 409             c = c[2:]
 410             i -= 1
 411
 412         c = eval('0x'+c[0:6])
 413         if c > 0x800000:
 414             c /= 256
 415             i += 1
 416
 417         new_bits = c + MM * i
 418         return new_bits, new_target
 419