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    = {}                                 # monitored transactions
  36         self.interface.register_channel('verifier')
  37
  38         self.verified_tx     = config.get('verified_tx',{})       # height of verified tx
  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.init_headers_file()
  47         self.set_local_height()
  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                 return (self.local_height - self.verified_tx[tx] + 1) if tx in self.verified_tx else 0
  54             else:
  55                 return 0
  56
  57     def add(self, tx_hash, tx_height):
  58         """ add a transaction to the list of monitored transactions. """
  59         with self.lock:
  60             if tx_hash not in self.transactions.keys():
  61                 self.transactions[tx_hash] = tx_height
  62
  63     def run(self):
  64         requested_merkle = []
  65         requested_chunks = []
  66         requested_headers = []
  67         all_chunks = False
  68
  69         # subscribe to block headers
  70         self.interface.send([ ('blockchain.headers.subscribe',[])], 'verifier')
  71
  72         while True:
  73             # request missing chunks
  74             if not all_chunks and self.height and not requested_chunks:
  75
  76                 if self.local_height + 50 < self.height:
  77                     min_index = (self.local_height + 1)/2016
  78                     max_index = (self.height + 1)/2016
  79                     for i in range(min_index, max_index + 1):
  80                         print_error( "requesting chunk", i )
  81                         self.interface.send([ ('blockchain.block.get_chunk',[i])], 'verifier')
  82                         requested_chunks.append(i)
  83                         break
  84                 else:
  85                     all_chunks = True
  86                     print_error("downloaded all chunks")
  87
  88             # request missing tx
  89             if all_chunks:
  90                 for tx_hash, tx_height in self.transactions.items():
  91                     if tx_hash not in self.verified_tx:
  92                         if self.merkle_roots.get(tx_hash) is None and tx_hash not in requested_merkle:
  93                             print_error('requesting merkle', tx_hash)
  94                             self.interface.send([ ('blockchain.transaction.get_merkle',[tx_hash, tx_height]) ], 'verifier')
  95                             requested_merkle.append(tx_hash)
  96
  97             # process pending headers
  98             if self.pending_headers and all_chunks:
  99                 done = []
 100                 for header in self.pending_headers:
 101                     if self.verify_header(header):
 102                         done.append(header)
 103                     else:
 104                         # request previous header
 105                         i = header.get('block_height') - 1
 106                         if i not in requested_headers:
 107                             print_error("requesting header %d"%i)
 108                             self.interface.send([ ('blockchain.block.get_header',[i])], 'verifier')
 109                             requested_headers.append(i)
 110                         # no point continuing
 111                         break
 112                 if done:
 113                     self.interface.trigger_callback('updated')
 114                     for header in done:
 115                         self.pending_headers.remove(header)
 116
 117             try:
 118                 r = self.interface.get_response('verifier',timeout=1)
 119             except Queue.Empty:
 120                 time.sleep(1)
 121                 continue
 122
 123             # 3. handle response
 124             method = r['method']
 125             params = r['params']
 126             result = r['result']
 127
 128             if method == 'blockchain.transaction.get_merkle':
 129                 tx_hash = params[0]
 130                 self.verify_merkle(tx_hash, result)
 131                 requested_merkle.remove(tx_hash)
 132
 133             elif method == 'blockchain.block.get_chunk':
 134                 index = params[0]
 135                 self.verify_chunk(index, result)
 136                 requested_chunks.remove(index)
 137
 138             elif method in ['blockchain.headers.subscribe', 'blockchain.block.get_header']:
 139
 140                 self.pending_headers.append(result)
 141                 if method == 'blockchain.block.get_header':
 142                     requested_headers.remove(result.get('block_height'))
 143                 else:
 144                     self.height = result.get('block_height')
 145
 146                 self.pending_headers.sort(key=lambda x: x.get('block_height'))
 147                 # print "pending headers", map(lambda x: x.get('block_height'), self.pending_headers)
 148
 149
 150
 151     def verify_merkle(self, tx_hash, result):
 152         tx_height = result.get('block_height')
 153         self.merkle_roots[tx_hash] = self.hash_merkle_root(result['merkle'], tx_hash, result.get('pos'))
 154         header = self.read_header(tx_height)
 155         if not header: return
 156         assert header.get('merkle_root') == self.merkle_roots[tx_hash]
 157         # we passed all the tests
 158         self.verified_tx[tx_hash] = tx_height
 159         print_error("verified %s"%tx_hash)
 160         self.config.set_key('verified_tx', self.verified_tx, True)
 161         self.interface.trigger_callback('updated')
 162
 163
 164     def verify_chunk(self, index, hexdata):
 165         data = hexdata.decode('hex')
 166         height = index*2016
 167         num = len(data)/80
 168         print_error("validating headers %d"%height)
 169
 170         if index == 0:
 171             previous_hash = ("0"*64)
 172         else:
 173             prev_header = self.read_header(index*2016-1)
 174             if prev_header is None: raise
 175             previous_hash = self.hash_header(prev_header)
 176
 177         bits, target = self.get_target(index)
 178
 179         for i in range(num):
 180             height = index*2016 + i
 181             raw_header = data[i*80:(i+1)*80]
 182             header = self.header_from_string(raw_header)
 183             _hash = self.hash_header(header)
 184             assert previous_hash == header.get('prev_block_hash')
 185             assert bits == header.get('bits')
 186             assert eval('0x'+_hash) < target
 187
 188             previous_header = header
 189             previous_hash = _hash
 190
 191         self.save_chunk(index, data)
 192
 193
 194     def verify_header(self, header):
 195         # add header to the blockchain file
 196         # if there is a reorg, push it in a stack
 197
 198         height = header.get('block_height')
 199
 200         prev_header = self.read_header(height -1)
 201         if not prev_header:
 202             # return False to request previous header
 203             return False
 204
 205         prev_hash = self.hash_header(prev_header)
 206         bits, target = self.get_target(height/2016)
 207         _hash = self.hash_header(header)
 208         try:
 209             assert prev_hash == header.get('prev_block_hash')
 210             assert bits == header.get('bits')
 211             assert eval('0x'+_hash) < target
 212         except:
 213             # this can be caused by a reorg.
 214             print_error("verify header failed"+ repr(header))
 215             # undo verifications
 216             for tx_hash, tx_height in self.verified_tx.items():
 217                 if tx_height >= height:
 218                     print_error("redoing", tx_hash)
 219                     self.verified_tx.pop(tx_hash)
 220                     if tx_hash in self.merkle_roots: self.merkle_roots.pop(tx_hash)
 221             # return False to request previous header.
 222             return False
 223
 224         self.save_header(header)
 225         print_error("verify header:", _hash, height)
 226         return True
 227
 228
 229
 230
 231     def header_to_string(self, res):
 232         s = int_to_hex(res.get('version'),4) \
 233             + rev_hex(res.get('prev_block_hash')) \
 234             + rev_hex(res.get('merkle_root')) \
 235             + int_to_hex(int(res.get('timestamp')),4) \
 236             + int_to_hex(int(res.get('bits')),4) \
 237             + int_to_hex(int(res.get('nonce')),4)
 238         return s
 239
 240
 241     def header_from_string(self, s):
 242         hex_to_int = lambda s: eval('0x' + s[::-1].encode('hex'))
 243         h = {}
 244         h['version'] = hex_to_int(s[0:4])
 245         h['prev_block_hash'] = hash_encode(s[4:36])
 246         h['merkle_root'] = hash_encode(s[36:68])
 247         h['timestamp'] = hex_to_int(s[68:72])
 248         h['bits'] = hex_to_int(s[72:76])
 249         h['nonce'] = hex_to_int(s[76:80])
 250         return h
 251
 252     def hash_header(self, header):
 253         return rev_hex(Hash(self.header_to_string(header).decode('hex')).encode('hex'))
 254
 255     def hash_merkle_root(self, merkle_s, target_hash, pos):
 256         h = hash_decode(target_hash)
 257         for i in range(len(merkle_s)):
 258             item = merkle_s[i]
 259             h = Hash( hash_decode(item) + h ) if ((pos >> i) & 1) else Hash( h + hash_decode(item) )
 260         return hash_encode(h)
 261
 262     def path(self):
 263         wdir = self.config.get('blockchain_headers_path', user_dir())
 264         if not os.path.exists( wdir ): os.mkdir(wdir)
 265         return os.path.join( wdir, 'blockchain_headers')
 266
 267     def init_headers_file(self):
 268         filename = self.path()
 269         if os.path.exists(filename):
 270             return
 271         src = os.path.join(appdata_dir(), 'blockchain_headers')
 272         if os.path.exists(src):
 273             # copy it from appdata dir
 274             print_error( "copying headers to", filename )
 275             shutil.copy(src, filename)
 276         else:
 277             print_error( "creating headers file", filename )
 278             open(filename,'wb+').close()
 279
 280     def save_chunk(self, index, chunk):
 281         filename = self.path()
 282         f = open(filename,'rb+')
 283         f.seek(index*2016*80)
 284         h = f.write(chunk)
 285         f.close()
 286         self.set_local_height()
 287
 288     def save_header(self, header):
 289         data = self.header_to_string(header).decode('hex')
 290         assert len(data) == 80
 291         height = header.get('block_height')
 292         filename = self.path()
 293         f = open(filename,'rb+')
 294         f.seek(height*80)
 295         h = f.write(data)
 296         f.close()
 297         self.set_local_height()
 298
 299
 300     def set_local_height(self):
 301         name = self.path()
 302         if os.path.exists(name):
 303             h = os.path.getsize(name)/80 - 1
 304             if self.local_height != h:
 305                 self.local_height = h
 306
 307
 308     def read_header(self, block_height):
 309         name = self.path()
 310         if os.path.exists(name):
 311             f = open(name,'rb')
 312             f.seek(block_height*80)
 313             h = f.read(80)
 314             f.close()
 315             if len(h) == 80:
 316                 h = self.header_from_string(h)
 317                 return h
 318
 319
 320     def get_target(self, index):
 321
 322         max_target = 0x00000000FFFF0000000000000000000000000000000000000000000000000000
 323         if index == 0: return 0x1d00ffff, max_target
 324
 325         first = self.read_header((index-1)*2016)
 326         last = self.read_header(index*2016-1)
 327
 328         nActualTimespan = last.get('timestamp') - first.get('timestamp')
 329         nTargetTimespan = 14*24*60*60
 330         nActualTimespan = max(nActualTimespan, nTargetTimespan/4)
 331         nActualTimespan = min(nActualTimespan, nTargetTimespan*4)
 332
 333         bits = last.get('bits')
 334         # convert to bignum
 335         MM = 256*256*256
 336         a = bits%MM
 337         if a < 0x8000:
 338             a *= 256
 339         target = (a) * pow(2, 8 * (bits/MM - 3))
 340
 341         # new target
 342         new_target = min( max_target, (target * nActualTimespan)/nTargetTimespan )
 343
 344         # convert it to bits
 345         c = ("%064X"%new_target)[2:]
 346         i = 31
 347         while c[0:2]=="00":
 348             c = c[2:]
 349             i -= 1
 350
 351         c = eval('0x'+c[0:6])
 352         if c > 0x800000:
 353             c /= 256
 354             i += 1
 355
 356         new_bits = c + MM * i
 357         return new_bits, new_target
 358
 359     def get_timestamp(self, tx_height):
 360         if tx_height>0:
 361             header = self.read_header(tx_height)
 362             timestamp = header.get('timestamp') if header else 0
 363         else:
 364             timestamp = 1e12
 365         return timestamp
 366