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