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