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
  69     def is_running(self):
  70         with self.lock: return self.running
  71
  72     def run(self):
  73         with self.lock:
  74             self.running = True
  75         requested_merkle = []
  76         requested_chunks = []
  77         requested_headers = []
  78         all_chunks = False
  79
  80         # subscribe to block headers
  81         self.interface.send([ ('blockchain.headers.subscribe',[])], 'verifier')
  82
  83         while self.is_running():
  84             # request missing chunks
  85             if not all_chunks and self.height and not requested_chunks:
  86
  87                 if self.local_height + 50 < self.height:
  88                     min_index = (self.local_height + 1)/2016
  89                     max_index = (self.height + 1)/2016
  90                     for i in range(min_index, max_index + 1):
  91                         print_error( "requesting chunk", i )
  92                         self.interface.send([ ('blockchain.block.get_chunk',[i])], 'verifier')
  93                         requested_chunks.append(i)
  94                         break
  95                 else:
  96                     all_chunks = True
  97                     print_error("downloaded all chunks")
  98
  99             # request missing tx
 100             if all_chunks:
 101                 for tx_hash, tx_height in self.transactions.items():
 102                     if tx_hash not in self.verified_tx:
 103                         if self.merkle_roots.get(tx_hash) is None and tx_hash not in requested_merkle:
 104                             print_error('requesting merkle', tx_hash)
 105                             self.interface.send([ ('blockchain.transaction.get_merkle',[tx_hash, tx_height]) ], 'verifier')
 106                             requested_merkle.append(tx_hash)
 107
 108             # process pending headers
 109             if self.pending_headers and all_chunks:
 110                 done = []
 111                 for header in self.pending_headers:
 112                     if self.verify_header(header):
 113                         done.append(header)
 114                     else:
 115                         # request previous header
 116                         i = header.get('block_height') - 1
 117                         if i not in requested_headers:
 118                             print_error("requesting header %d"%i)
 119                             self.interface.send([ ('blockchain.block.get_header',[i])], 'verifier')
 120                             requested_headers.append(i)
 121                         # no point continuing
 122                         break
 123                 if done:
 124                     self.interface.trigger_callback('updated')
 125                     for header in done:
 126                         self.pending_headers.remove(header)
 127
 128             try:
 129                 r = self.interface.get_response('verifier',timeout=0.1)
 130             except Queue.Empty:
 131                 continue
 132
 133             # 3. handle response
 134             method = r['method']
 135             params = r['params']
 136             result = r['result']
 137
 138             if method == 'blockchain.transaction.get_merkle':
 139                 tx_hash = params[0]
 140                 self.verify_merkle(tx_hash, result)
 141                 requested_merkle.remove(tx_hash)
 142
 143             elif method == 'blockchain.block.get_chunk':
 144                 index = params[0]
 145                 self.verify_chunk(index, result)
 146                 requested_chunks.remove(index)
 147
 148             elif method in ['blockchain.headers.subscribe', 'blockchain.block.get_header']:
 149
 150                 self.pending_headers.append(result)
 151                 if method == 'blockchain.block.get_header':
 152                     requested_headers.remove(result.get('block_height'))
 153                 else:
 154                     self.height = result.get('block_height')
 155
 156                 self.pending_headers.sort(key=lambda x: x.get('block_height'))
 157                 # print "pending headers", map(lambda x: x.get('block_height'), self.pending_headers)
 158
 159
 160
 161     def verify_merkle(self, tx_hash, result):
 162         tx_height = result.get('block_height')
 163         self.merkle_roots[tx_hash] = self.hash_merkle_root(result['merkle'], tx_hash, result.get('pos'))
 164         header = self.read_header(tx_height)
 165         if not header: return
 166         assert header.get('merkle_root') == self.merkle_roots[tx_hash]
 167         # we passed all the tests
 168         self.verified_tx[tx_hash] = tx_height
 169         print_error("verified %s"%tx_hash)
 170         self.config.set_key('verified_tx', self.verified_tx, True)
 171         self.interface.trigger_callback('updated')
 172
 173
 174     def verify_chunk(self, index, hexdata):
 175         data = hexdata.decode('hex')
 176         height = index*2016
 177         num = len(data)/80
 178         print_error("validating headers %d"%height)
 179
 180         if index == 0:
 181             previous_hash = ("0"*64)
 182         else:
 183             prev_header = self.read_header(index*2016-1)
 184             if prev_header is None: raise
 185             previous_hash = self.hash_header(prev_header)
 186
 187         bits, target = self.get_target(index)
 188
 189         for i in range(num):
 190             height = index*2016 + i
 191             raw_header = data[i*80:(i+1)*80]
 192             header = self.header_from_string(raw_header)
 193             _hash = self.hash_header(header)
 194             assert previous_hash == header.get('prev_block_hash')
 195             assert bits == header.get('bits')
 196             assert eval('0x'+_hash) < target
 197
 198             previous_header = header
 199             previous_hash = _hash
 200
 201         self.save_chunk(index, data)
 202
 203
 204     def verify_header(self, header):
 205         # add header to the blockchain file
 206         # if there is a reorg, push it in a stack
 207
 208         height = header.get('block_height')
 209
 210         prev_header = self.read_header(height -1)
 211         if not prev_header:
 212             # return False to request previous header
 213             return False
 214
 215         prev_hash = self.hash_header(prev_header)
 216         bits, target = self.get_target(height/2016)
 217         _hash = self.hash_header(header)
 218         try:
 219             assert prev_hash == header.get('prev_block_hash')
 220             assert bits == header.get('bits')
 221             assert eval('0x'+_hash) < target
 222         except:
 223             # this can be caused by a reorg.
 224             print_error("verify header failed"+ repr(header))
 225             # undo verifications
 226             for tx_hash, tx_height in self.verified_tx.items():
 227                 if tx_height >= height:
 228                     print_error("redoing", tx_hash)
 229                     self.verified_tx.pop(tx_hash)
 230                     if tx_hash in self.merkle_roots: self.merkle_roots.pop(tx_hash)
 231             # return False to request previous header.
 232             return False
 233
 234         self.save_header(header)
 235         print_error("verify header:", _hash, height)
 236         return True
 237
 238
 239
 240
 241     def header_to_string(self, res):
 242         s = int_to_hex(res.get('version'),4) \
 243             + rev_hex(res.get('prev_block_hash')) \
 244             + rev_hex(res.get('merkle_root')) \
 245             + int_to_hex(int(res.get('timestamp')),4) \
 246             + int_to_hex(int(res.get('bits')),4) \
 247             + int_to_hex(int(res.get('nonce')),4)
 248         return s
 249
 250
 251     def header_from_string(self, s):
 252         hex_to_int = lambda s: eval('0x' + s[::-1].encode('hex'))
 253         h = {}
 254         h['version'] = hex_to_int(s[0:4])
 255         h['prev_block_hash'] = hash_encode(s[4:36])
 256         h['merkle_root'] = hash_encode(s[36:68])
 257         h['timestamp'] = hex_to_int(s[68:72])
 258         h['bits'] = hex_to_int(s[72:76])
 259         h['nonce'] = hex_to_int(s[76:80])
 260         return h
 261
 262     def hash_header(self, header):
 263         return rev_hex(Hash(self.header_to_string(header).decode('hex')).encode('hex'))
 264
 265     def hash_merkle_root(self, merkle_s, target_hash, pos):
 266         h = hash_decode(target_hash)
 267         for i in range(len(merkle_s)):
 268             item = merkle_s[i]
 269             h = Hash( hash_decode(item) + h ) if ((pos >> i) & 1) else Hash( h + hash_decode(item) )
 270         return hash_encode(h)
 271
 272     def path(self):
 273         wdir = self.config.get('blockchain_headers_path', user_dir())
 274         if not os.path.exists( wdir ): os.mkdir(wdir)
 275         return os.path.join( wdir, 'blockchain_headers')
 276
 277     def init_headers_file(self):
 278         filename = self.path()
 279         if os.path.exists(filename):
 280             return
 281         src = os.path.join(appdata_dir(), 'blockchain_headers')
 282         if os.path.exists(src):
 283             # copy it from appdata dir
 284             print_error( "copying headers to", filename )
 285             shutil.copy(src, filename)
 286         else:
 287             print_error( "creating headers file", filename )
 288             open(filename,'wb+').close()
 289
 290     def save_chunk(self, index, chunk):
 291         filename = self.path()
 292         f = open(filename,'rb+')
 293         f.seek(index*2016*80)
 294         h = f.write(chunk)
 295         f.close()
 296         self.set_local_height()
 297
 298     def save_header(self, header):
 299         data = self.header_to_string(header).decode('hex')
 300         assert len(data) == 80
 301         height = header.get('block_height')
 302         filename = self.path()
 303         f = open(filename,'rb+')
 304         f.seek(height*80)
 305         h = f.write(data)
 306         f.close()
 307         self.set_local_height()
 308
 309
 310     def set_local_height(self):
 311         name = self.path()
 312         if os.path.exists(name):
 313             h = os.path.getsize(name)/80 - 1
 314             if self.local_height != h:
 315                 self.local_height = h
 316
 317
 318     def read_header(self, block_height):
 319         name = self.path()
 320         if os.path.exists(name):
 321             f = open(name,'rb')
 322             f.seek(block_height*80)
 323             h = f.read(80)
 324             f.close()
 325             if len(h) == 80:
 326                 h = self.header_from_string(h)
 327                 return h
 328
 329
 330     def get_target(self, index):
 331
 332         max_target = 0x00000000FFFF0000000000000000000000000000000000000000000000000000
 333         if index == 0: return 0x1d00ffff, max_target
 334
 335         first = self.read_header((index-1)*2016)
 336         last = self.read_header(index*2016-1)
 337
 338         nActualTimespan = last.get('timestamp') - first.get('timestamp')
 339         nTargetTimespan = 14*24*60*60
 340         nActualTimespan = max(nActualTimespan, nTargetTimespan/4)
 341         nActualTimespan = min(nActualTimespan, nTargetTimespan*4)
 342
 343         bits = last.get('bits')
 344         # convert to bignum
 345         MM = 256*256*256
 346         a = bits%MM
 347         if a < 0x8000:
 348             a *= 256
 349         target = (a) * pow(2, 8 * (bits/MM - 3))
 350
 351         # new target
 352         new_target = min( max_target, (target * nActualTimespan)/nTargetTimespan )
 353
 354         # convert it to bits
 355         c = ("%064X"%new_target)[2:]
 356         i = 31
 357         while c[0:2]=="00":
 358             c = c[2:]
 359             i -= 1
 360
 361         c = eval('0x'+c[0:6])
 362         if c > 0x800000:
 363             c /= 256
 364             i += 1
 365
 366         new_bits = c + MM * i
 367         return new_bits, new_target
 368
 369     def get_timestamp(self, tx_height):
 370         if tx_height>0:
 371             header = self.read_header(tx_height)
 372             if header:
 373                 return header.get('timestamp')
 374
 375