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, wallet, config):
  30         threading.Thread.__init__(self)
  31         self.daemon = True
  32         self.config = config
  33         self.wallet = wallet
  34         self.interface = self.wallet.interface
  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
  41         #self.config.set_key('verified_tx', [], True)
  42         #for i in range(70): self.get_target(i)
  43         #sys.exit()
  44
  45
  46
  47     def run(self):
  48         requested_merkle = []
  49         requested_chunks = []
  50
  51         while True:
  52             # request missing chunks
  53             max_index = self.wallet.blocks/2016
  54             if not requested_chunks:
  55                 for i in range(0, max_index + 1):
  56                     # test if we can read the first header of the chunk
  57                     if self.read_header(i*2016): continue
  58                     print "requesting chunk", i
  59                     self.interface.send([ ('blockchain.block.get_chunk',[i])], 'verifier')
  60                     requested_chunks.append(i)
  61                     break
  62
  63             # todo: request missing blocks too
  64
  65             # request missing tx merkle
  66             txlist = self.wallet.get_tx_hashes()
  67             for tx in txlist:
  68                 if tx not in self.verified_tx:
  69                     if tx not in requested_merkle:
  70                         requested_merkle.append(tx)
  71                         self.request_merkle(tx)
  72                         break
  73
  74             try:
  75                 r = self.interface.get_response('verifier',timeout=1)
  76             except Queue.Empty:
  77                 time.sleep(1)
  78                 continue
  79
  80             # 3. handle response
  81             method = r['method']
  82             params = r['params']
  83             result = r['result']
  84
  85             if method == 'blockchain.transaction.get_merkle':
  86                 tx_hash = params[0]
  87                 self.verify_merkle(tx_hash, result)
  88                 requested_merkle.remove(tx_hash)
  89
  90             elif method == 'blockchain.block.get_chunk':
  91                 index = params[0]
  92                 self.verify_chunk(index, result)
  93                 requested_chunks.remove(index)
  94
  95             elif method == 'blockchain.block.get_header':
  96                 self.verify_header(result)
  97
  98
  99     def request_merkle(self, tx_hash):
 100         self.interface.send([ ('blockchain.transaction.get_merkle',[tx_hash]) ], 'verifier')
 101
 102
 103     def verify_merkle(self, tx_hash, result):
 104         tx_height = result.get('block_height')
 105         self.merkle_roots[tx_hash] = self.hash_merkle_root(result['merkle'], tx_hash)
 106         header = self.read_header(tx_height)
 107         if header:
 108             assert header.get('merkle_root') == self.merkle_roots[tx_hash]
 109             self.verified_tx.append(tx_hash)
 110             print "verified", tx_hash
 111             self.config.set_key('verified_tx', self.verified_tx, True)
 112
 113
 114     def verify_chunk(self, index, hexdata):
 115         data = hexdata.decode('hex')
 116         height = index*2016
 117         numblocks = len(data)/80
 118         print "validate_chunk", index, numblocks
 119
 120         if index == 0:
 121             previous_hash = ("0"*64)
 122         else:
 123             prev_header = self.read_header(index*2016-1)
 124             if prev_header is None: raise
 125             previous_hash = self.hash_header(prev_header)
 126
 127         bits, target = self.get_target(index)
 128
 129         for i in range(numblocks):
 130             height = index*2016 + i
 131             raw_header = data[i*80:(i+1)*80]
 132             header = self.header_from_string(raw_header)
 133             _hash = self.hash_header(header)
 134             assert previous_hash == header.get('prev_block_hash')
 135             assert bits == header.get('bits')
 136             assert eval('0x'+_hash) < target
 137
 138             previous_header = header
 139             previous_hash = _hash
 140
 141         self.save_chunk(index, data)
 142
 143
 144     def validate_header(self, header):
 145         """ if there is a previous or a next block in the list, check the hash"""
 146         height = header.get('block_height')
 147         with self.lock:
 148             self.headers[height] = header # detect conflicts
 149             prev_header = next_header = None
 150             if height-1 in self.headers:
 151                 prev_header = self.headers[height-1]
 152             if height+1 in self.headers:
 153                 next_header = self.headers[height+1]
 154
 155         if prev_header:
 156             prev_hash = self.hash_header(prev_header)
 157             assert prev_hash == header.get('prev_block_hash')
 158             self.save_header(header)
 159         if next_header:
 160             _hash = self.hash_header(header)
 161             assert _hash == next_header.get('prev_block_hash')
 162
 163
 164     def header_to_string(self, res):
 165         s = int_to_hex(res.get('version'),4) \
 166             + rev_hex(res.get('prev_block_hash')) \
 167             + rev_hex(res.get('merkle_root')) \
 168             + int_to_hex(int(res.get('timestamp')),4) \
 169             + int_to_hex(int(res.get('bits')),4) \
 170             + int_to_hex(int(res.get('nonce')),4)
 171         return s
 172
 173
 174     def header_from_string(self, s):
 175         hex_to_int = lambda s: eval('0x' + s[::-1].encode('hex'))
 176         h = {}
 177         h['version'] = hex_to_int(s[0:4])
 178         h['prev_block_hash'] = hash_encode(s[4:36])
 179         h['merkle_root'] = hash_encode(s[36:68])
 180         h['timestamp'] = hex_to_int(s[68:72])
 181         h['bits'] = hex_to_int(s[72:76])
 182         h['nonce'] = hex_to_int(s[76:80])
 183         return h
 184
 185
 186     def hash_header(self, header):
 187         return rev_hex(Hash(self.header_to_string(header).decode('hex')).encode('hex'))
 188
 189
 190     def hash_merkle_root(self, merkle_s, target_hash):
 191         h = hash_decode(target_hash)
 192         for item in merkle_s:
 193             is_left = item[0] == 'L'
 194             h = Hash( h + hash_decode(item[1:]) ) if is_left else Hash( hash_decode(item[1:]) + h )
 195         return hash_encode(h)
 196
 197
 198     def path(self):
 199         wdir = user_dir()
 200         if not os.path.exists( wdir ):
 201             wdir = os.path.dirname(self.config.path)
 202         return os.path.join( wdir, 'blockchain_headers')
 203
 204
 205     def save_chunk(self, index, chunk):
 206         filename = self.path()
 207         if os.path.exists(filename):
 208             f = open(filename,'rw+')
 209         else:
 210             print "creating file", filename
 211             f = open(filename,'w+')
 212         f.seek(index*2016*80)
 213         h = f.write(chunk)
 214         f.close()
 215
 216
 217     def read_header(self, block_height):
 218         name = self.path()
 219         if os.path.exists(name):
 220             f = open(name,'rb')
 221             f.seek(block_height*80)
 222             h = f.read(80)
 223             f.close()
 224             if len(h) == 80:
 225                 h = self.header_from_string(h)
 226                 return h
 227
 228
 229     def get_target(self, index):
 230
 231         max_target = 0x00000000FFFF0000000000000000000000000000000000000000000000000000
 232         if index == 0: return 0x1d00ffff, max_target
 233
 234         first = self.read_header((index-1)*2016)
 235         last = self.read_header(index*2016-1)
 236
 237         nActualTimespan = last.get('timestamp') - first.get('timestamp')
 238         nTargetTimespan = 14*24*60*60
 239         nActualTimespan = max(nActualTimespan, nTargetTimespan/4)
 240         nActualTimespan = min(nActualTimespan, nTargetTimespan*4)
 241
 242         bits = last.get('bits')
 243         # convert to bignum
 244         MM = 256*256*256
 245         a = bits%MM
 246         if a < 0x8000:
 247             a *= 256
 248         target = (a) * pow(2, 8 * (bits/MM - 3))
 249
 250         # new target
 251         new_target = min( max_target, (target * nActualTimespan)/nTargetTimespan )
 252
 253         # convert it to bits
 254         c = ("%064X"%new_target)[2:]
 255         i = 31
 256         while c[0:2]=="00":
 257             c = c[2:]
 258             i -= 1
 259
 260         c = eval('0x'+c[0:6])
 261         if c > 0x800000:
 262             c /= 256
 263             i += 1
 264
 265         new_bits = c + MM * i
 266         # print "%3d"%index, "%8x"%bits, "%64X"%new_target, hex(c)[2:].upper(), hex(new_bits)
 267         return new_bits, new_target
 268