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