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