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):
  30         threading.Thread.__init__(self)
  31         self.daemon = True
  32         self.config = config
  33         self.interface = interface
  34         self.transactions    = []                                 # monitored 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_height()
  44
  45     def get_confirmations(self, tx):
  46         return (self.local_height - self.verified_tx[tx] + 1) if tx in self.verified_tx else 0
  47
  48     def add(self, tx):
  49         with self.lock:
  50             if tx not in self.transactions:
  51                 self.transactions.append(tx)
  52
  53     def run(self):
  54         requested_merkle = []
  55         requested_chunks = []
  56         requested_headers = []
  57         pending_headers_changed = False
  58
  59         # subscribe to block headers
  60         self.interface.send([ ('blockchain.headers.subscribe',[])], 'verifier')
  61
  62         while True:
  63             # request missing chunks
  64             max_index = (self.height+1)/2016
  65             if not requested_chunks:
  66                 for i in range(0, max_index + 1):
  67                     # test if we can read the first header of the chunk
  68                     if self.read_header(i*2016): continue
  69                     print "requesting chunk", i
  70                     self.interface.send([ ('blockchain.block.get_chunk',[i])], 'verifier')
  71                     requested_chunks.append(i)
  72                     break
  73
  74             # request missing headers
  75             if not requested_chunks and self.local_height:
  76                 for i in range(self.local_height + 1, self.height + 1):
  77                     if i not in requested_headers:
  78                         print "requesting header", i
  79                         self.interface.send([ ('blockchain.block.get_header',[i])], 'verifier')
  80                         requested_headers.append(i)
  81
  82             # request missing tx merkle
  83             for tx in self.transactions:
  84                 if tx not in self.verified_tx:
  85                     if tx not in requested_merkle:
  86                         requested_merkle.append(tx)
  87                         self.request_merkle(tx)
  88                         #break
  89
  90             try:
  91                 r = self.interface.get_response('verifier',timeout=1)
  92             except Queue.Empty:
  93                 time.sleep(1)
  94                 continue
  95
  96             # 3. handle response
  97             method = r['method']
  98             params = r['params']
  99             result = r['result']
 100
 101             if method == 'blockchain.transaction.get_merkle':
 102                 tx_hash = params[0]
 103                 self.verify_merkle(tx_hash, result)
 104                 requested_merkle.remove(tx_hash)
 105
 106             elif method == 'blockchain.block.get_chunk':
 107                 index = params[0]
 108                 self.verify_chunk(index, result)
 109                 requested_chunks.remove(index)
 110
 111             elif method == 'blockchain.headers.subscribe':
 112                 self.height = result.get('block_height')
 113                 self.pending_headers.append(result)
 114                 pending_headers_changed = True
 115
 116             elif method == 'blockchain.block.get_header':
 117                 height = result.get('block_height')
 118                 requested_headers.remove(height)
 119                 self.pending_headers.append(result)
 120                 pending_headers_changed = True
 121
 122             # process pending headers
 123             if pending_headers_changed:
 124                 self.pending_headers.sort(key=lambda x: x.get('block_height'))
 125                 print "pending headers", map(lambda x: x.get('block_height'), self.pending_headers)
 126                 for header in self.pending_headers:
 127                     if self.verify_header(header):
 128                         self.pending_headers.remove(header)
 129                     else:
 130                         break
 131                 pending_headers_changed = False
 132
 133             self.interface.trigger_callback('updated')
 134
 135
 136     def request_merkle(self, tx_hash):
 137         self.interface.send([ ('blockchain.transaction.get_merkle',[tx_hash]) ], 'verifier')
 138
 139
 140     def verify_merkle(self, tx_hash, result):
 141         tx_height = result.get('block_height')
 142         self.merkle_roots[tx_hash] = self.hash_merkle_root(result['merkle'], tx_hash)
 143         header = self.read_header(tx_height)
 144         if header:
 145             assert header.get('merkle_root') == self.merkle_roots[tx_hash]
 146             self.verified_tx[tx_hash] = tx_height
 147             print "verified", tx_hash
 148             self.config.set_key('verified_tx', self.verified_tx, True)
 149
 150
 151     def verify_chunk(self, index, hexdata):
 152         data = hexdata.decode('hex')
 153         height = index*2016
 154         num = len(data)/80
 155         print "validate_chunk", index, num
 156
 157         if index == 0:
 158             previous_hash = ("0"*64)
 159         else:
 160             prev_header = self.read_header(index*2016-1)
 161             if prev_header is None: raise
 162             previous_hash = self.hash_header(prev_header)
 163
 164         bits, target = self.get_target(index)
 165
 166         for i in range(num):
 167             height = index*2016 + i
 168             raw_header = data[i*80:(i+1)*80]
 169             header = self.header_from_string(raw_header)
 170             _hash = self.hash_header(header)
 171             assert previous_hash == header.get('prev_block_hash')
 172             assert bits == header.get('bits')
 173             assert eval('0x'+_hash) < target
 174
 175             previous_header = header
 176             previous_hash = _hash
 177
 178         self.save_chunk(index, data)
 179
 180
 181     def verify_header(self, header):
 182         # add header to the blockchain file
 183         # if there is a reorg, push it in a stack
 184
 185         height = header.get('block_height')
 186
 187         prev_header = self.read_header(height -1)
 188         if not prev_header:
 189             print "no previous header", height
 190             return
 191
 192         #prev_hash = prev_header.get('block_height')
 193         prev_hash = self.hash_header(prev_header)
 194         bits, target = self.get_target(height/2016)
 195         _hash = self.hash_header(header)
 196         try:
 197             assert prev_hash == header.get('prev_block_hash')
 198             assert bits == header.get('bits')
 199             assert eval('0x'+_hash) < target
 200             ok = True
 201         except:
 202             print "verify header failed", header
 203             raise
 204             # this could be caused by a reorg. request the previous header
 205             ok = False
 206             #request previous one
 207
 208         if ok:
 209             self.save_header(header)
 210             print "verify header: ok", height
 211             return True
 212
 213
 214
 215
 216     def header_to_string(self, res):
 217         s = int_to_hex(res.get('version'),4) \
 218             + rev_hex(res.get('prev_block_hash')) \
 219             + rev_hex(res.get('merkle_root')) \
 220             + int_to_hex(int(res.get('timestamp')),4) \
 221             + int_to_hex(int(res.get('bits')),4) \
 222             + int_to_hex(int(res.get('nonce')),4)
 223         return s
 224
 225
 226     def header_from_string(self, s):
 227         hex_to_int = lambda s: eval('0x' + s[::-1].encode('hex'))
 228         h = {}
 229         h['version'] = hex_to_int(s[0:4])
 230         h['prev_block_hash'] = hash_encode(s[4:36])
 231         h['merkle_root'] = hash_encode(s[36:68])
 232         h['timestamp'] = hex_to_int(s[68:72])
 233         h['bits'] = hex_to_int(s[72:76])
 234         h['nonce'] = hex_to_int(s[76:80])
 235         return h
 236
 237
 238     def hash_header(self, header):
 239         return rev_hex(Hash(self.header_to_string(header).decode('hex')).encode('hex'))
 240
 241
 242     def hash_merkle_root(self, merkle_s, target_hash):
 243         h = hash_decode(target_hash)
 244         for item in merkle_s:
 245             is_left = item[0] == 'L'
 246             h = Hash( h + hash_decode(item[1:]) ) if is_left else Hash( hash_decode(item[1:]) + h )
 247         return hash_encode(h)
 248
 249     def path(self):
 250         wdir = user_dir()
 251         if not os.path.exists( wdir ):
 252             wdir = os.path.dirname(self.config.path)
 253         return os.path.join( wdir, 'blockchain_headers')
 254
 255     def save_chunk(self, index, chunk):
 256         filename = self.path()
 257         if os.path.exists(filename):
 258             f = open(filename,'rw+')
 259         else:
 260             print "creating file", filename
 261             f = open(filename,'w+')
 262         f.seek(index*2016*80)
 263         h = f.write(chunk)
 264         f.close()
 265         self.set_local_height()
 266
 267     def save_header(self, header):
 268         data = self.header_to_string(header).decode('hex')
 269         assert len(data) == 80
 270         height = header.get('block_height')
 271         filename = self.path()
 272         f = open(filename,'rw+')
 273         f.seek(height*80)
 274         h = f.write(data)
 275         f.close()
 276         self.set_local_height()
 277
 278
 279     def set_local_height(self):
 280         name = self.path()
 281         if os.path.exists(name):
 282             h = os.path.getsize(name)/80 - 1
 283             if self.local_height != h:
 284                 self.local_height = h
 285
 286
 287     def read_header(self, block_height):
 288         name = self.path()
 289         if os.path.exists(name):
 290             f = open(name,'rb')
 291             f.seek(block_height*80)
 292             h = f.read(80)
 293             f.close()
 294             if len(h) == 80:
 295                 h = self.header_from_string(h)
 296                 return h
 297
 298
 299     def get_target(self, index):
 300
 301         max_target = 0x00000000FFFF0000000000000000000000000000000000000000000000000000
 302         if index == 0: return 0x1d00ffff, max_target
 303
 304         first = self.read_header((index-1)*2016)
 305         last = self.read_header(index*2016-1)
 306
 307         nActualTimespan = last.get('timestamp') - first.get('timestamp')
 308         nTargetTimespan = 14*24*60*60
 309         nActualTimespan = max(nActualTimespan, nTargetTimespan/4)
 310         nActualTimespan = min(nActualTimespan, nTargetTimespan*4)
 311
 312         bits = last.get('bits')
 313         # convert to bignum
 314         MM = 256*256*256
 315         a = bits%MM
 316         if a < 0x8000:
 317             a *= 256
 318         target = (a) * pow(2, 8 * (bits/MM - 3))
 319
 320         # new target
 321         new_target = min( max_target, (target * nActualTimespan)/nTargetTimespan )
 322
 323         # convert it to bits
 324         c = ("%064X"%new_target)[2:]
 325         i = 31
 326         while c[0:2]=="00":
 327             c = c[2:]
 328             i -= 1
 329
 330         c = eval('0x'+c[0:6])
 331         if c > 0x800000:
 332             c /= 256
 333             i += 1
 334
 335         new_bits = c + MM * i
 336         # print "%3d"%index, "%8x"%bits, "%64X"%new_target, hex(c)[2:].upper(), hex(new_bits)
 337         return new_bits, new_target
 338