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     """ 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         self.verified_tx     = config.get('verified_tx',{})
  38         self.merkle_roots    = config.get('merkle_roots',{})      # hashed by me
  39         self.targets         = config.get('targets',{})           # compute targets
  40         self.lock = threading.Lock()
  41         self.pending_headers = [] # headers that have not been verified
  42         self.height = 0
  43         self.local_height = 0
  44         self.set_local_height()
  45
  46     def get_confirmations(self, tx):
  47         """ return the number of confirmations of a monitored transaction. """
  48         with self.lock:
  49             assert tx in self.transactions
  50             return (self.local_height - self.verified_tx[tx] + 1) if tx in self.verified_tx else 0
  51
  52     def add(self, tx):
  53         """ add a transaction to the list of monitored transactions. """
  54         with self.lock:
  55             if tx not in self.transactions:
  56                 self.transactions.append(tx)
  57
  58     def run(self):
  59         requested_merkle = []
  60         requested_chunks = []
  61         requested_headers = []
  62         all_chunks = False
  63
  64         # subscribe to block headers
  65         self.interface.send([ ('blockchain.headers.subscribe',[])], 'verifier')
  66
  67         while True:
  68             # request missing chunks
  69             max_index = (self.height+1)/2016
  70             if not all_chunks and self.height and not requested_chunks:
  71                 for i in range(0, max_index + 1):
  72                     # test if we can read the first header of the chunk
  73                     if self.read_header(i*2016): continue
  74                     # print "requesting chunk", i
  75                     self.interface.send([ ('blockchain.block.get_chunk',[i])], 'verifier')
  76                     requested_chunks.append(i)
  77                     break
  78                 else:
  79                     all_chunks = True
  80                     print "all chunks"
  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
  91             # process pending headers
  92             if self.pending_headers and all_chunks:
  93                 done = []
  94                 for header in self.pending_headers:
  95                     if self.verify_header(header):
  96                         done.append(header)
  97                     else:
  98                         # request previous header
  99                         i = header.get('block_height') - 1
 100                         if i not in requested_headers:
 101                             print "requesting header", i
 102                             self.interface.send([ ('blockchain.block.get_header',[i])], 'verifier')
 103                             requested_headers.append(i)
 104                         # no point continuing
 105                         break
 106                 for header in done: self.pending_headers.remove(header)
 107                 self.interface.trigger_callback('updated')
 108
 109             try:
 110                 r = self.interface.get_response('verifier',timeout=1)
 111             except Queue.Empty:
 112                 time.sleep(1)
 113                 continue
 114
 115             # 3. handle response
 116             method = r['method']
 117             params = r['params']
 118             result = r['result']
 119
 120             if method == 'blockchain.transaction.get_merkle':
 121                 tx_hash = params[0]
 122                 self.verify_merkle(tx_hash, result)
 123                 requested_merkle.remove(tx_hash)
 124
 125             elif method == 'blockchain.block.get_chunk':
 126                 index = params[0]
 127                 self.verify_chunk(index, result)
 128                 requested_chunks.remove(index)
 129
 130             elif method in ['blockchain.headers.subscribe', 'blockchain.block.get_header']:
 131
 132                 self.pending_headers.append(result)
 133                 if method == 'blockchain.block.get_header':
 134                     requested_headers.remove(result.get('block_height'))
 135                 else:
 136                     self.height = result.get('block_height')
 137
 138                 self.pending_headers.sort(key=lambda x: x.get('block_height'))
 139                 # print "pending headers", map(lambda x: x.get('block_height'), self.pending_headers)
 140
 141
 142
 143             self.interface.trigger_callback('updated')
 144
 145
 146     def request_merkle(self, tx_hash):
 147         self.interface.send([ ('blockchain.transaction.get_merkle',[tx_hash]) ], 'verifier')
 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 header:
 155             assert header.get('merkle_root') == self.merkle_roots[tx_hash]
 156             self.verified_tx[tx_hash] = tx_height
 157             print "verified", tx_hash
 158             self.config.set_key('verified_tx', self.verified_tx, True)
 159
 160
 161     def verify_chunk(self, index, hexdata):
 162         data = hexdata.decode('hex')
 163         height = index*2016
 164         num = len(data)/80
 165         print "validating headers", height, num
 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             print "no previous header", height
 200             return False
 201
 202         #prev_hash = prev_header.get('block_height')
 203         prev_hash = self.hash_header(prev_header)
 204         bits, target = self.get_target(height/2016)
 205         _hash = self.hash_header(header)
 206         try:
 207             assert prev_hash == header.get('prev_block_hash')
 208             assert bits == header.get('bits')
 209             assert eval('0x'+_hash) < target
 210         except:
 211             print "verify header failed", header
 212             # this can be caused by a reorg. returning False will request the previous header.
 213             return False
 214
 215         self.save_header(header)
 216         print "verify header: ok", height
 217         return True
 218
 219
 220
 221
 222     def header_to_string(self, res):
 223         s = int_to_hex(res.get('version'),4) \
 224             + rev_hex(res.get('prev_block_hash')) \
 225             + rev_hex(res.get('merkle_root')) \
 226             + int_to_hex(int(res.get('timestamp')),4) \
 227             + int_to_hex(int(res.get('bits')),4) \
 228             + int_to_hex(int(res.get('nonce')),4)
 229         return s
 230
 231
 232     def header_from_string(self, s):
 233         hex_to_int = lambda s: eval('0x' + s[::-1].encode('hex'))
 234         h = {}
 235         h['version'] = hex_to_int(s[0:4])
 236         h['prev_block_hash'] = hash_encode(s[4:36])
 237         h['merkle_root'] = hash_encode(s[36:68])
 238         h['timestamp'] = hex_to_int(s[68:72])
 239         h['bits'] = hex_to_int(s[72:76])
 240         h['nonce'] = hex_to_int(s[76:80])
 241         return h
 242
 243     def hash_header(self, header):
 244         return rev_hex(Hash(self.header_to_string(header).decode('hex')).encode('hex'))
 245
 246     def hash_merkle_root(self, merkle_s, target_hash, pos):
 247         h = hash_decode(target_hash)
 248         for i in range(len(merkle_s)):
 249             item = merkle_s[i]
 250             h = Hash( hash_decode(item) + h ) if ((pos >> i) & 1) else Hash( h + hash_decode(item) )
 251         return hash_encode(h)
 252
 253     def path(self):
 254         wdir = self.config.get('blockchain_headers_path', user_dir())
 255         if not os.path.exists( wdir ): os.mkdir(wdir)
 256         return os.path.join( wdir, 'blockchain_headers')
 257
 258     def save_chunk(self, index, chunk):
 259         filename = self.path()
 260         if os.path.exists(filename):
 261             f = open(filename,'rw+')
 262         else:
 263             print "creating file", filename
 264             f = open(filename,'w+')
 265         f.seek(index*2016*80)
 266         h = f.write(chunk)
 267         f.close()
 268         self.set_local_height()
 269
 270     def save_header(self, header):
 271         # todo: invalidate tx verifications if we rewind
 272         data = self.header_to_string(header).decode('hex')
 273         assert len(data) == 80
 274         height = header.get('block_height')
 275         filename = self.path()
 276         f = open(filename,'rw+')
 277         f.seek(height*80)
 278         h = f.write(data)
 279         f.close()
 280         self.set_local_height()
 281
 282
 283     def set_local_height(self):
 284         name = self.path()
 285         if os.path.exists(name):
 286             h = os.path.getsize(name)/80 - 1
 287             if self.local_height != h:
 288                 self.local_height = h
 289
 290
 291     def read_header(self, block_height):
 292         name = self.path()
 293         if os.path.exists(name):
 294             f = open(name,'rb')
 295             f.seek(block_height*80)
 296             h = f.read(80)
 297             f.close()
 298             if len(h) == 80:
 299                 h = self.header_from_string(h)
 300                 return h
 301
 302
 303     def get_target(self, index):
 304
 305         max_target = 0x00000000FFFF0000000000000000000000000000000000000000000000000000
 306         if index == 0: return 0x1d00ffff, max_target
 307
 308         first = self.read_header((index-1)*2016)
 309         last = self.read_header(index*2016-1)
 310
 311         nActualTimespan = last.get('timestamp') - first.get('timestamp')
 312         nTargetTimespan = 14*24*60*60
 313         nActualTimespan = max(nActualTimespan, nTargetTimespan/4)
 314         nActualTimespan = min(nActualTimespan, nTargetTimespan*4)
 315
 316         bits = last.get('bits')
 317         # convert to bignum
 318         MM = 256*256*256
 319         a = bits%MM
 320         if a < 0x8000:
 321             a *= 256
 322         target = (a) * pow(2, 8 * (bits/MM - 3))
 323
 324         # new target
 325         new_target = min( max_target, (target * nActualTimespan)/nTargetTimespan )
 326
 327         # convert it to bits
 328         c = ("%064X"%new_target)[2:]
 329         i = 31
 330         while c[0:2]=="00":
 331             c = c[2:]
 332             i -= 1
 333
 334         c = eval('0x'+c[0:6])
 335         if c > 0x800000:
 336             c /= 256
 337             i += 1
 338
 339         new_bits = c + MM * i
 340         # print "%3d"%index, "%8x"%bits, "%64X"%new_target, hex(c)[2:].upper(), hex(new_bits)
 341         return new_bits, new_target
 342