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