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