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375 lines
11 KiB
375 lines
11 KiB
#!/usr/bin/env python
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#
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# Electrum - lightweight Bitcoin client
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# Copyright (C) 2012 thomasv@ecdsa.org
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#
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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import threading, time, Queue, os, sys, shutil
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from util import user_dir, appdata_dir, print_error
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from bitcoin import *
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class Blockchain(threading.Thread):
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def __init__(self, config, network):
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threading.Thread.__init__(self)
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self.daemon = True
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self.config = config
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self.network = network
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self.lock = threading.Lock()
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self.local_height = 0
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self.running = False
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self.headers_url = 'http://headers.electrum.org/blockchain_headers'
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self.set_local_height()
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self.queue = Queue.Queue()
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def height(self):
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return self.local_height
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def stop(self):
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with self.lock: self.running = False
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def is_running(self):
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with self.lock: return self.running
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def run(self):
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self.init_headers_file()
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self.set_local_height()
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print_error( "blocks:", self.local_height )
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with self.lock:
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self.running = True
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while self.is_running():
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try:
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result = self.queue.get()
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except Queue.Empty:
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continue
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if not result: continue
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i, header = result
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if not header: continue
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height = header.get('block_height')
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if height <= self.local_height:
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continue
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if height > self.local_height + 50:
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if not self.get_and_verify_chunks(i, header, height):
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continue
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if height > self.local_height:
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# get missing parts from interface (until it connects to my chain)
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chain = self.get_chain( i, header )
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# skip that server if the result is not consistent
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if not chain:
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print_error('e')
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continue
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# verify the chain
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if self.verify_chain( chain ):
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print_error("height:", height, i.server)
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for header in chain:
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self.save_header(header)
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else:
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print_error("error", i.server)
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# todo: dismiss that server
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continue
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self.network.new_blockchain_height(height, i)
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def verify_chain(self, chain):
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first_header = chain[0]
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prev_header = self.read_header(first_header.get('block_height') -1)
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for header in chain:
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height = header.get('block_height')
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prev_hash = self.hash_header(prev_header)
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bits, target = self.get_target(height/2016, chain)
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_hash = self.hash_header(header)
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try:
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assert prev_hash == header.get('prev_block_hash')
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assert bits == header.get('bits')
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assert int('0x'+_hash,16) < target
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except Exception:
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return False
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prev_header = header
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return True
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def verify_chunk(self, index, hexdata):
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data = hexdata.decode('hex')
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height = index*2016
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num = len(data)/80
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if index == 0:
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previous_hash = ("0"*64)
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else:
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prev_header = self.read_header(index*2016-1)
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if prev_header is None: raise
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previous_hash = self.hash_header(prev_header)
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bits, target = self.get_target(index)
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for i in range(num):
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height = index*2016 + i
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raw_header = data[i*80:(i+1)*80]
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header = self.header_from_string(raw_header)
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_hash = self.hash_header(header)
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assert previous_hash == header.get('prev_block_hash')
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assert bits == header.get('bits')
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assert int('0x'+_hash,16) < target
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previous_header = header
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previous_hash = _hash
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self.save_chunk(index, data)
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print_error("validated chunk %d"%height)
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def header_to_string(self, res):
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s = int_to_hex(res.get('version'),4) \
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+ rev_hex(res.get('prev_block_hash')) \
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+ rev_hex(res.get('merkle_root')) \
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+ int_to_hex(int(res.get('timestamp')),4) \
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+ int_to_hex(int(res.get('bits')),4) \
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+ int_to_hex(int(res.get('nonce')),4)
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return s
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def header_from_string(self, s):
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hex_to_int = lambda s: int('0x' + s[::-1].encode('hex'), 16)
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h = {}
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h['version'] = hex_to_int(s[0:4])
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h['prev_block_hash'] = hash_encode(s[4:36])
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h['merkle_root'] = hash_encode(s[36:68])
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h['timestamp'] = hex_to_int(s[68:72])
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h['bits'] = hex_to_int(s[72:76])
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h['nonce'] = hex_to_int(s[76:80])
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return h
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def hash_header(self, header):
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return rev_hex(Hash(self.header_to_string(header).decode('hex')).encode('hex'))
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def path(self):
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return os.path.join( self.config.path, 'blockchain_headers')
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def init_headers_file(self):
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filename = self.path()
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if os.path.exists(filename):
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return
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try:
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import urllib, socket
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socket.setdefaulttimeout(30)
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print_error("downloading ", self.headers_url )
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urllib.urlretrieve(self.headers_url, filename)
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print_error("done.")
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except Exception:
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print_error( "download failed. creating file", filename )
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open(filename,'wb+').close()
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def save_chunk(self, index, chunk):
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filename = self.path()
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f = open(filename,'rb+')
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f.seek(index*2016*80)
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h = f.write(chunk)
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f.close()
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self.set_local_height()
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def save_header(self, header):
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data = self.header_to_string(header).decode('hex')
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assert len(data) == 80
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height = header.get('block_height')
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filename = self.path()
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f = open(filename,'rb+')
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f.seek(height*80)
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h = f.write(data)
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f.close()
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self.set_local_height()
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def set_local_height(self):
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name = self.path()
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if os.path.exists(name):
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h = os.path.getsize(name)/80 - 1
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if self.local_height != h:
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self.local_height = h
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def read_header(self, block_height):
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name = self.path()
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if os.path.exists(name):
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f = open(name,'rb')
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f.seek(block_height*80)
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h = f.read(80)
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f.close()
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if len(h) == 80:
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h = self.header_from_string(h)
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return h
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def get_target(self, index, chain=[]):
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max_target = 0x00000000FFFF0000000000000000000000000000000000000000000000000000
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if index == 0: return 0x1d00ffff, max_target
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first = self.read_header((index-1)*2016)
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last = self.read_header(index*2016-1)
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if last is None:
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for h in chain:
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if h.get('block_height') == index*2016-1:
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last = h
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nActualTimespan = last.get('timestamp') - first.get('timestamp')
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nTargetTimespan = 14*24*60*60
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nActualTimespan = max(nActualTimespan, nTargetTimespan/4)
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nActualTimespan = min(nActualTimespan, nTargetTimespan*4)
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bits = last.get('bits')
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# convert to bignum
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MM = 256*256*256
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a = bits%MM
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if a < 0x8000:
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a *= 256
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target = (a) * pow(2, 8 * (bits/MM - 3))
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# new target
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new_target = min( max_target, (target * nActualTimespan)/nTargetTimespan )
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# convert it to bits
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c = ("%064X"%new_target)[2:]
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i = 31
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while c[0:2]=="00":
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c = c[2:]
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i -= 1
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c = int('0x'+c[0:6],16)
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if c > 0x800000:
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c /= 256
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i += 1
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new_bits = c + MM * i
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return new_bits, new_target
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def request_header(self, i, h, queue):
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print_error("requesting header %d from %s"%(h, i.server))
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i.send([ ('blockchain.block.get_header',[h])], lambda i,r: queue.put((i,r)))
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def retrieve_header(self, i, queue):
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while True:
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try:
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ir = queue.get(timeout=1)
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except Queue.Empty:
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print_error('timeout')
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continue
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if not ir:
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continue
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i, r = ir
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if r.get('error'):
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print_error('Verifier received an error:', r)
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continue
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# 3. handle response
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method = r['method']
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params = r['params']
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result = r['result']
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if method == 'blockchain.block.get_header':
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return result
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def get_chain(self, interface, final_header):
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header = final_header
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chain = [ final_header ]
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requested_header = False
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queue = Queue.Queue()
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while self.is_running():
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if requested_header:
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header = self.retrieve_header(interface, queue)
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if not header: return
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chain = [ header ] + chain
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requested_header = False
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height = header.get('block_height')
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previous_header = self.read_header(height -1)
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if not previous_header:
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self.request_header(interface, height - 1, queue)
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requested_header = True
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continue
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# verify that it connects to my chain
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prev_hash = self.hash_header(previous_header)
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if prev_hash != header.get('prev_block_hash'):
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print_error("reorg")
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self.request_header(interface, height - 1, queue)
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requested_header = True
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continue
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else:
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# the chain is complete
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return chain
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def get_and_verify_chunks(self, i, header, height):
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queue = Queue.Queue()
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min_index = (self.local_height + 1)/2016
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max_index = (height + 1)/2016
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n = min_index
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while n < max_index + 1:
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print_error( "Requesting chunk:", n )
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r = i.synchronous_get([ ('blockchain.block.get_chunk',[n])])[0]
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if not r:
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continue
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try:
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self.verify_chunk(n, r)
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n = n + 1
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except Exception:
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print_error('Verify chunk failed!')
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n = n - 1
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if n < 0:
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return False
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return True
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