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