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
  22 from bitcoin import *
  23
  24
  25
  26
  27 class WalletVerifier(threading.Thread):
  28
  29     def __init__(self, interface, config, get_transactions):
  30         threading.Thread.__init__(self)
  31         self.daemon = True
  32         self.config = config
  33         self.interface = interface
  34         self.get_transactions = get_transactions
  35         self.interface.register_channel('verifier')
  36         self.verified_tx     = config.get('verified_tx',[])
  37         self.merkle_roots    = config.get('merkle_roots',{})      # hashed by me
  38         self.targets         = config.get('targets',{})           # compute targets
  39         self.lock = threading.Lock()
  40         self.pending_headers = [] # headers that have not been verified
  41         self.height = 0
  42         self.local_height = 0
  43         self.set_local_numblocks()
  44
  45
  46
  47
  48     def run(self):
  49         requested_merkle = []
  50         requested_chunks = []
  51         requested_headers = []
  52
  53         # subscribe to block headers
  54         self.interface.send([ ('blockchain.headers.subscribe',[])], 'verifier')
  55
  56         while True:
  57             # request missing chunks
  58             max_index = (self.height+1)/2016
  59             if not requested_chunks:
  60                 for i in range(0, max_index + 1):
  61                     # test if we can read the first header of the chunk
  62                     if self.read_header(i*2016): continue
  63                     print "requesting chunk", i
  64                     self.interface.send([ ('blockchain.block.get_chunk',[i])], 'verifier')
  65                     requested_chunks.append(i)
  66                     break
  67
  68             # request missing headers
  69             if not requested_chunks and self.local_height:
  70                 for i in range(self.local_height + 1, self.height + 1):
  71                     if i not in requested_headers:
  72                         print "requesting header", i
  73                         self.interface.send([ ('blockchain.block.get_header',[i])], 'verifier')
  74                         requested_headers.append(i)
  75
  76             # request missing tx merkle
  77             txlist = self.get_transactions()
  78             for tx in txlist:
  79                 if tx not in self.verified_tx:
  80                     if tx not in requested_merkle:
  81                         requested_merkle.append(tx)
  82                         self.request_merkle(tx)
  83                         #break
  84
  85             try:
  86                 r = self.interface.get_response('verifier',timeout=1)
  87             except Queue.Empty:
  88                 time.sleep(1)
  89                 continue
  90
  91             # 3. handle response
  92             method = r['method']
  93             params = r['params']
  94             result = r['result']
  95
  96             if method == 'blockchain.transaction.get_merkle':
  97                 tx_hash = params[0]
  98                 self.verify_merkle(tx_hash, result)
  99                 requested_merkle.remove(tx_hash)
 100
 101             elif method == 'blockchain.block.get_chunk':
 102                 index = params[0]
 103                 self.verify_chunk(index, result)
 104                 requested_chunks.remove(index)
 105
 106             elif method == 'blockchain.headers.subscribe':
 107                 self.height = result.get('block_height')
 108                 self.pending_headers.append(result)
 109
 110             elif method == 'blockchain.block.get_header':
 111                 height = result.get('block_height')
 112                 requested_headers.remove(height)
 113                 self.pending_headers.append(result)
 114
 115             # process pending headers
 116             # todo: sort them first
 117             for header in self.pending_headers:
 118                 self.verify_header(header)
 119             self.pending_headers = []
 120
 121
 122
 123     def request_merkle(self, tx_hash):
 124         self.interface.send([ ('blockchain.transaction.get_merkle',[tx_hash]) ], 'verifier')
 125
 126
 127     def verify_merkle(self, tx_hash, result):
 128         tx_height = result.get('block_height')
 129         self.merkle_roots[tx_hash] = self.hash_merkle_root(result['merkle'], tx_hash)
 130         header = self.read_header(tx_height)
 131         if header:
 132             assert header.get('merkle_root') == self.merkle_roots[tx_hash]
 133             self.verified_tx.append(tx_hash)
 134             print "verified", tx_hash
 135             self.config.set_key('verified_tx', self.verified_tx, True)
 136
 137
 138     def verify_chunk(self, index, hexdata):
 139         data = hexdata.decode('hex')
 140         height = index*2016
 141         num = len(data)/80
 142         print "validate_chunk", index, num
 143
 144         if index == 0:
 145             previous_hash = ("0"*64)
 146         else:
 147             prev_header = self.read_header(index*2016-1)
 148             if prev_header is None: raise
 149             previous_hash = self.hash_header(prev_header)
 150
 151         bits, target = self.get_target(index)
 152
 153         for i in range(num):
 154             height = index*2016 + i
 155             raw_header = data[i*80:(i+1)*80]
 156             header = self.header_from_string(raw_header)
 157             _hash = self.hash_header(header)
 158             assert previous_hash == header.get('prev_block_hash')
 159             assert bits == header.get('bits')
 160             assert eval('0x'+_hash) < target
 161
 162             previous_header = header
 163             previous_hash = _hash
 164
 165         self.save_chunk(index, data)
 166
 167
 168     def verify_header(self, header):
 169         # add header to the blockchain file
 170         # if there is a reorg, push it in a stack
 171
 172         height = header.get('block_height')
 173
 174         prev_header = self.read_header(height -1)
 175         if not prev_header:
 176             raise "no previous header", height
 177             return
 178
 179         #prev_hash = prev_header.get('block_height')
 180         prev_hash = self.hash_header(prev_header)
 181         bits, target = self.get_target(height/2016)
 182         _hash = self.hash_header(header)
 183         try:
 184             assert prev_hash == header.get('prev_block_hash')
 185             assert bits == header.get('bits')
 186             assert eval('0x'+_hash) < target
 187             ok = True
 188         except:
 189             print "verify header failed", header
 190             raise
 191             # this could be caused by a reorg. request the previous header
 192             ok = False
 193             #request previous one
 194
 195         if ok:
 196             self.save_header(header)
 197             print "verify header: ok", height
 198
 199
 200
 201
 202     def header_to_string(self, res):
 203         s = int_to_hex(res.get('version'),4) \
 204             + rev_hex(res.get('prev_block_hash')) \
 205             + rev_hex(res.get('merkle_root')) \
 206             + int_to_hex(int(res.get('timestamp')),4) \
 207             + int_to_hex(int(res.get('bits')),4) \
 208             + int_to_hex(int(res.get('nonce')),4)
 209         return s
 210
 211
 212     def header_from_string(self, s):
 213         hex_to_int = lambda s: eval('0x' + s[::-1].encode('hex'))
 214         h = {}
 215         h['version'] = hex_to_int(s[0:4])
 216         h['prev_block_hash'] = hash_encode(s[4:36])
 217         h['merkle_root'] = hash_encode(s[36:68])
 218         h['timestamp'] = hex_to_int(s[68:72])
 219         h['bits'] = hex_to_int(s[72:76])
 220         h['nonce'] = hex_to_int(s[76:80])
 221         return h
 222
 223
 224     def hash_header(self, header):
 225         return rev_hex(Hash(self.header_to_string(header).decode('hex')).encode('hex'))
 226
 227
 228     def hash_merkle_root(self, merkle_s, target_hash):
 229         h = hash_decode(target_hash)
 230         for item in merkle_s:
 231             is_left = item[0] == 'L'
 232             h = Hash( h + hash_decode(item[1:]) ) if is_left else Hash( hash_decode(item[1:]) + h )
 233         return hash_encode(h)
 234
 235     def path(self):
 236         wdir = user_dir()
 237         if not os.path.exists( wdir ):
 238             wdir = os.path.dirname(self.config.path)
 239         return os.path.join( wdir, 'blockchain_headers')
 240
 241     def save_chunk(self, index, chunk):
 242         filename = self.path()
 243         if os.path.exists(filename):
 244             f = open(filename,'rw+')
 245         else:
 246             print "creating file", filename
 247             f = open(filename,'w+')
 248         f.seek(index*2016*80)
 249         h = f.write(chunk)
 250         f.close()
 251         self.set_local_numblocks()
 252
 253     def save_header(self, header):
 254         data = self.header_to_string(header).decode('hex')
 255         assert len(data) == 80
 256         height = header.get('block_height')
 257         filename = self.path()
 258         f = open(filename,'rw+')
 259         f.seek(height*80)
 260         h = f.write(data)
 261         f.close()
 262         self.set_local_numblocks()
 263
 264     def set_local_numblocks(self):
 265         name = self.path()
 266         if os.path.exists(name):
 267             self.local_height = os.path.getsize(name)/80 - 1
 268             # print "local height", self.local_height, os.path.getsize(name)/80.
 269
 270
 271     def read_header(self, block_height):
 272         name = self.path()
 273         if os.path.exists(name):
 274             f = open(name,'rb')
 275             f.seek(block_height*80)
 276             h = f.read(80)
 277             f.close()
 278             if len(h) == 80:
 279                 h = self.header_from_string(h)
 280                 return h
 281
 282
 283     def get_target(self, index):
 284
 285         max_target = 0x00000000FFFF0000000000000000000000000000000000000000000000000000
 286         if index == 0: return 0x1d00ffff, max_target
 287
 288         first = self.read_header((index-1)*2016)
 289         last = self.read_header(index*2016-1)
 290
 291         nActualTimespan = last.get('timestamp') - first.get('timestamp')
 292         nTargetTimespan = 14*24*60*60
 293         nActualTimespan = max(nActualTimespan, nTargetTimespan/4)
 294         nActualTimespan = min(nActualTimespan, nTargetTimespan*4)
 295
 296         bits = last.get('bits')
 297         # convert to bignum
 298         MM = 256*256*256
 299         a = bits%MM
 300         if a < 0x8000:
 301             a *= 256
 302         target = (a) * pow(2, 8 * (bits/MM - 3))
 303
 304         # new target
 305         new_target = min( max_target, (target * nActualTimespan)/nTargetTimespan )
 306
 307         # convert it to bits
 308         c = ("%064X"%new_target)[2:]
 309         i = 31
 310         while c[0:2]=="00":
 311             c = c[2:]
 312             i -= 1
 313
 314         c = eval('0x'+c[0:6])
 315         if c > 0x800000:
 316             c /= 256
 317             i += 1
 318
 319         new_bits = c + MM * i
 320         # print "%3d"%index, "%8x"%bits, "%64X"%new_target, hex(c)[2:].upper(), hex(new_bits)
 321         return new_bits, new_target
 322