lib/blockchain.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, shutil
  21 from util import user_dir, appdata_dir, print_error
  22 from bitcoin import *
  23
  24 try:
  25     from ltc_scrypt import getPoWHash
  26 except ImportError:
  27     print_msg("Warning: scrypt not available, using fallback")
  28     from scrypt import scrypt_1024_1_1_80 as getPoWHash
  29
  30 class Blockchain(threading.Thread):
  31
  32     def __init__(self, config, network):
  33         threading.Thread.__init__(self)
  34         self.daemon = True
  35         self.config = config
  36         self.network = network
  37         self.lock = threading.Lock()
  38         self.local_height = 0
  39         self.running = False
  40         self.headers_url = 'http://novacoin.su/static/blockchain_headers'
  41         self.set_local_height()
  42         self.queue = Queue.Queue()
  43
  44
  45     def height(self):
  46         return self.local_height
  47
  48
  49     def stop(self):
  50         with self.lock: self.running = False
  51
  52
  53     def is_running(self):
  54         with self.lock: return self.running
  55
  56
  57     def run(self):
  58         self.init_headers_file()
  59         self.set_local_height()
  60         print_error( "blocks:", self.local_height )
  61
  62         with self.lock:
  63             self.running = True
  64
  65         while self.is_running():
  66
  67             try:
  68                 result = self.queue.get()
  69             except Queue.Empty:
  70                 continue
  71
  72             if not result: continue
  73
  74             i, header = result
  75             if not header: continue
  76
  77             height = header.get('block_height')
  78
  79             if height <= self.local_height:
  80                 continue
  81
  82             if height > self.local_height + 50:
  83                 if not self.get_and_verify_chunks(i, header, height):
  84                     continue
  85
  86             if height > self.local_height:
  87                 # get missing parts from interface (until it connects to my chain)
  88                 chain = self.get_chain( i, header )
  89
  90                 # skip that server if the result is not consistent
  91                 if not chain:
  92                     print_error('e')
  93                     continue
  94
  95                 # verify the chain
  96                 if self.verify_chain( chain ):
  97                     print_error("height:", height, i.server)
  98                     for header in chain:
  99                         self.save_header(header)
 100                 else:
 101                     print_error("error", i.server)
 102                     # todo: dismiss that server
 103                     continue
 104
 105
 106             self.network.new_blockchain_height(height, i)
 107
 108
 109
 110     def calculate_target(self, bits):
 111         # convert to bignum
 112         MM = 256*256*256
 113         a = bits%MM
 114         if a < 0x8000:
 115             a *= 256
 116         return (a) * pow(2, 8 * (bits/MM - 3))
 117
 118
 119     def verify_chain(self, chain):
 120
 121         first_header = chain[0]
 122         prev_header = self.read_header(first_header.get('block_height') -1)
 123
 124         for header in chain:
 125
 126             height = header.get('block_height')
 127
 128             prev_hash = self.hash_header(prev_header)
 129             header_hash = self.hash_header(header)
 130
 131             try:
 132                 assert prev_hash == header.get('prev_block_hash')
 133                 if header.get('nonce') != 0:
 134                     assert int('0x'+_hash,16) < self.calculate_target(header.get('bits'))
 135             except Exception:
 136                 return False
 137
 138             prev_header = header
 139
 140         return True
 141
 142
 143
 144     def verify_chunk(self, index, hexdata):
 145         data = hexdata.decode('hex')
 146         height = index*2016
 147         num = len(data)/80
 148
 149         if index == 0:
 150             previous_hash = ("0"*64)
 151         else:
 152             prev_header = self.read_header(index*2016-1)
 153             if prev_header is None: raise
 154             _hash = self.hash_header(prev_header)
 155
 156         for i in range(num):
 157             height = index*2016 + i
 158             raw_header = data[i*80:(i+1)*80]
 159             header = self.header_from_string(raw_header)
 160             header_hash = self.hash_header(header)
 161
 162             assert previous_hash == header.get('prev_block_hash')
 163             if header.get('nonce') != 0:
 164                 assert int('0x'+header_hash,16) < calculate_target(header.get('bits'))
 165
 166             previous_header = header
 167             previous_hash = header_hash
 168
 169         self.save_chunk(index, data)
 170         print_error("validated chunk %d"%height)
 171
 172
 173
 174     def header_to_string(self, res):
 175         s = int_to_hex(res.get('version'),4) \
 176             + rev_hex(res.get('prev_block_hash')) \
 177             + rev_hex(res.get('merkle_root')) \
 178             + int_to_hex(int(res.get('timestamp')),4) \
 179             + int_to_hex(int(res.get('bits')),4) \
 180             + int_to_hex(int(res.get('nonce')),4)
 181         return s
 182
 183
 184     def header_from_string(self, s):
 185         hex_to_int = lambda s: int('0x' + s[::-1].encode('hex'), 16)
 186         h = {}
 187         h['version'] = hex_to_int(s[0:4])
 188         h['prev_block_hash'] = hash_encode(s[4:36])
 189         h['merkle_root'] = hash_encode(s[36:68])
 190         h['timestamp'] = hex_to_int(s[68:72])
 191         h['bits'] = hex_to_int(s[72:76])
 192         h['nonce'] = hex_to_int(s[76:80])
 193         return h
 194
 195     def hash_header(self, header):
 196         return rev_hex(getPoWHash(self.header_to_string(header).decode('hex')).encode('hex'))
 197
 198     def path(self):
 199         return os.path.join( self.config.path, 'blockchain_headers')
 200
 201     def init_headers_file(self):
 202         filename = self.path()
 203         if os.path.exists(filename):
 204             return
 205
 206         try:
 207             import urllib, socket
 208             socket.setdefaulttimeout(30)
 209             print_error("downloading ", self.headers_url )
 210             urllib.urlretrieve(self.headers_url, filename)
 211             print_error("done.")
 212         except Exception:
 213             print_error( "download failed. creating file", filename )
 214             open(filename,'wb+').close()
 215
 216     def save_chunk(self, index, chunk):
 217         filename = self.path()
 218         f = open(filename,'rb+')
 219         f.seek(index*2016*80)
 220         h = f.write(chunk)
 221         f.close()
 222         self.set_local_height()
 223
 224     def save_header(self, header):
 225         data = self.header_to_string(header).decode('hex')
 226         assert len(data) == 80
 227         height = header.get('block_height')
 228         filename = self.path()
 229         f = open(filename,'rb+')
 230         f.seek(height*80)
 231         h = f.write(data)
 232         f.close()
 233         self.set_local_height()
 234
 235
 236     def set_local_height(self):
 237         name = self.path()
 238         if os.path.exists(name):
 239             h = os.path.getsize(name)/80 - 1
 240             if self.local_height != h:
 241                 self.local_height = h
 242
 243
 244     def read_header(self, block_height):
 245         name = self.path()
 246         if os.path.exists(name):
 247             f = open(name,'rb')
 248             f.seek(block_height*80)
 249             h = f.read(80)
 250             f.close()
 251             if len(h) == 80:
 252                 h = self.header_from_string(h)
 253                 return h
 254
 255     def request_header(self, i, h, queue):
 256         print_error("requesting header %d from %s"%(h, i.server))
 257         i.send([ ('blockchain.block.get_header',[h])], lambda i,r: queue.put((i,r)))
 258
 259     def retrieve_header(self, i, queue):
 260         while True:
 261             try:
 262                 ir = queue.get(timeout=1)
 263             except Queue.Empty:
 264                 print_error('timeout')
 265                 continue
 266
 267             if not ir:
 268                 continue
 269
 270             i, r = ir
 271
 272             if r.get('error'):
 273                 print_error('Verifier received an error:', r)
 274                 continue
 275
 276             # 3. handle response
 277             method = r['method']
 278             params = r['params']
 279             result = r['result']
 280
 281             if method == 'blockchain.block.get_header':
 282                 return result
 283
 284
 285
 286     def get_chain(self, interface, final_header):
 287
 288         header = final_header
 289         chain = [ final_header ]
 290         requested_header = False
 291         queue = Queue.Queue()
 292
 293         while self.is_running():
 294
 295             if requested_header:
 296                 header = self.retrieve_header(interface, queue)
 297                 if not header: return
 298                 chain = [ header ] + chain
 299                 requested_header = False
 300
 301             height = header.get('block_height')
 302             previous_header = self.read_header(height -1)
 303             if not previous_header:
 304                 self.request_header(interface, height - 1, queue)
 305                 requested_header = True
 306                 continue
 307
 308             # verify that it connects to my chain
 309             prev_hash = self.hash_header(previous_header)
 310             if prev_hash != header.get('prev_block_hash'):
 311                 print_error("reorg")
 312                 self.request_header(interface, height - 1, queue)
 313                 requested_header = True
 314                 continue
 315
 316             else:
 317                 # the chain is complete
 318                 return chain
 319
 320
 321     def get_and_verify_chunks(self, i, header, height):
 322
 323         queue = Queue.Queue()
 324         min_index = (self.local_height + 1)/2016
 325         max_index = (height + 1)/2016
 326         n = min_index
 327         while n < max_index + 1:
 328             print_error( "Requesting chunk:", n )
 329             r = i.synchronous_get([ ('blockchain.block.get_chunk',[n])])[0]
 330             if not r:
 331                 continue
 332             try:
 333                 self.verify_chunk(n, r)
 334                 n = n + 1
 335             except Exception:
 336                 print_error('Verify chunk failed!')
 337                 n = n - 1
 338                 if n < 0:
 339                     return False
 340
 341         return True
 342