You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
 
 
 
 

257 lines
8.1 KiB

#!/usr/bin/env python
#
# Electrum - lightweight Bitcoin client
# Copyright (C) 2012 thomasv@ecdsa.org
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
import os
import util
from bitcoin import *
class Blockchain():
'''Manages blockchain headers and their verification'''
def __init__(self, config, network):
self.config = config
self.network = network
self.headers_url = 'https://headers.electrum.org/blockchain_headers'
self.local_height = 0
self.set_local_height()
def print_error(self, *msg):
util.print_error("[blockchain]", *msg)
def height(self):
return self.local_height
def init(self):
self.init_headers_file()
self.set_local_height()
self.print_error("%d blocks" % self.local_height)
def verify_chain(self, chain):
first_header = chain[0]
prev_header = self.read_header(first_header.get('block_height') -1)
for header in chain:
height = header.get('block_height')
prev_hash = self.hash_header(prev_header)
bits, target = self.get_target(height/2016, chain)
_hash = self.hash_header(header)
try:
assert prev_hash == header.get('prev_block_hash')
assert bits == header.get('bits')
assert int('0x'+_hash,16) < target
except Exception:
return False
prev_header = header
return True
def verify_chunk(self, index, hexdata):
data = hexdata.decode('hex')
height = index*2016
num = len(data)/80
if index == 0:
previous_hash = ("0"*64)
else:
prev_header = self.read_header(index*2016-1)
if prev_header is None: raise
previous_hash = self.hash_header(prev_header)
bits, target = self.get_target(index)
for i in range(num):
height = index*2016 + i
raw_header = data[i*80:(i+1)*80]
header = self.header_from_string(raw_header)
_hash = self.hash_header(header)
assert previous_hash == header.get('prev_block_hash')
assert bits == header.get('bits')
assert int('0x'+_hash,16) < target
previous_header = header
previous_hash = _hash
self.save_chunk(index, data)
self.print_error("validated chunk %d to height %d" % (index, height))
def header_to_string(self, res):
s = int_to_hex(res.get('version'),4) \
+ rev_hex(res.get('prev_block_hash')) \
+ rev_hex(res.get('merkle_root')) \
+ int_to_hex(int(res.get('timestamp')),4) \
+ int_to_hex(int(res.get('bits')),4) \
+ int_to_hex(int(res.get('nonce')),4)
return s
def header_from_string(self, s):
hex_to_int = lambda s: int('0x' + s[::-1].encode('hex'), 16)
h = {}
h['version'] = hex_to_int(s[0:4])
h['prev_block_hash'] = hash_encode(s[4:36])
h['merkle_root'] = hash_encode(s[36:68])
h['timestamp'] = hex_to_int(s[68:72])
h['bits'] = hex_to_int(s[72:76])
h['nonce'] = hex_to_int(s[76:80])
return h
def hash_header(self, header):
return rev_hex(Hash(self.header_to_string(header).decode('hex')).encode('hex'))
def path(self):
return os.path.join(self.config.path, 'blockchain_headers')
def init_headers_file(self):
filename = self.path()
if os.path.exists(filename):
return
try:
import urllib, socket
socket.setdefaulttimeout(30)
self.print_error("downloading ", self.headers_url )
urllib.urlretrieve(self.headers_url, filename)
self.print_error("done.")
except Exception:
self.print_error( "download failed. creating file", filename )
open(filename,'wb+').close()
def save_chunk(self, index, chunk):
filename = self.path()
f = open(filename,'rb+')
f.seek(index*2016*80)
h = f.write(chunk)
f.close()
self.set_local_height()
def save_header(self, header):
data = self.header_to_string(header).decode('hex')
assert len(data) == 80
height = header.get('block_height')
filename = self.path()
f = open(filename,'rb+')
f.seek(height*80)
h = f.write(data)
f.close()
self.set_local_height()
def set_local_height(self):
name = self.path()
if os.path.exists(name):
h = os.path.getsize(name)/80 - 1
if self.local_height != h:
self.local_height = h
def read_header(self, block_height):
name = self.path()
if os.path.exists(name):
f = open(name,'rb')
f.seek(block_height*80)
h = f.read(80)
f.close()
if len(h) == 80:
h = self.header_from_string(h)
return h
def get_target(self, index, chain=None):
if chain is None:
chain = [] # Do not use mutables as default values!
max_target = 0x00000000FFFF0000000000000000000000000000000000000000000000000000
if index == 0: return 0x1d00ffff, max_target
first = self.read_header((index-1)*2016)
last = self.read_header(index*2016-1)
if last is None:
for h in chain:
if h.get('block_height') == index*2016-1:
last = h
nActualTimespan = last.get('timestamp') - first.get('timestamp')
nTargetTimespan = 14*24*60*60
nActualTimespan = max(nActualTimespan, nTargetTimespan/4)
nActualTimespan = min(nActualTimespan, nTargetTimespan*4)
bits = last.get('bits')
# convert to bignum
MM = 256*256*256
a = bits%MM
if a < 0x8000:
a *= 256
target = (a) * pow(2, 8 * (bits/MM - 3))
# new target
new_target = min( max_target, (target * nActualTimespan)/nTargetTimespan )
# convert it to bits
c = ("%064X"%new_target)[2:]
i = 31
while c[0:2]=="00":
c = c[2:]
i -= 1
c = int('0x'+c[0:6],16)
if c >= 0x800000:
c /= 256
i += 1
new_bits = c + MM * i
return new_bits, new_target
def connect_header(self, chain, header):
'''Builds a header chain until it connects. Returns True if it has
successfully connected, False if verification failed, otherwise the
height of the next header needed.'''
chain.append(header) # Ordered by decreasing height
previous_height = header['block_height'] - 1
previous_header = self.read_header(previous_height)
# Missing header, request it
if not previous_header:
return previous_height
# Does it connect to my chain?
prev_hash = self.hash_header(previous_header)
if prev_hash != header.get('prev_block_hash'):
self.print_error("reorg")
return previous_height
# The chain is complete. Reverse to order by increasing height
chain.reverse()
if self.verify_chain(chain):
self.print_error("connected at height:", previous_height)
for header in chain:
self.save_header(header)
return True
return False
def connect_chunk(self, idx, chunk):
try:
self.verify_chunk(idx, chunk)
return idx + 1
except Exception:
self.print_error('verify_chunk failed')
return idx - 1