electrum-bitcoinprivate/lib/blockchain.py

#!/usr/bin/env python
#
# Electrum - lightweight Bitcoin client
# Copyright (C) 2012 thomasv@ecdsa.org
#
# Permission is hereby granted, free of charge, to any person
# obtaining a copy of this software and associated documentation files
# (the "Software"), to deal in the Software without restriction,
# including without limitation the rights to use, copy, modify, merge,
# publish, distribute, sublicense, and/or sell copies of the Software,
# and to permit persons to whom the Software is furnished to do so,
# subject to the following conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.



import os
import util
import bitcoin
from bitcoin import *

MAX_TARGET = 0x00000000FFFF0000000000000000000000000000000000000000000000000000

class Blockchain(util.PrintError):
    '''Manages blockchain headers and their verification'''
    def __init__(self, config, network):
        self.config = config
        self.network = network
        self.checkpoint_height, self.checkpoint_hash = self.get_checkpoint()
        self.check_truncate_headers()
        self.set_local_height()

    def height(self):
        return self.local_height

    def init(self):
        import threading
        if os.path.exists(self.path()):
            self.downloading_headers = False
            return
        self.downloading_headers = True
        t = threading.Thread(target = self.init_headers_file)
        t.daemon = True
        t.start()

    def pass_checkpoint(self, header):
        if type(header) is not dict:
            return False
        if header.get('block_height') != self.checkpoint_height:
            return True
        if header.get('prev_block_hash') is None:
            header['prev_block_hash'] = '00'*32
        try:
            _hash = self.hash_header(header)
        except:
            return False
        return _hash == self.checkpoint_hash

    def verify_header(self, header, prev_header, bits, target):
        prev_hash = self.hash_header(prev_header)
        _hash = self.hash_header(header)
        if prev_hash != header.get('prev_block_hash'):
            raise BaseException("prev hash mismatch: %s vs %s" % (prev_hash, header.get('prev_block_hash')))
        if not self.pass_checkpoint(header):
            raise BaseException('failed checkpoint')
        if self.checkpoint_height == header.get('block_height'):
            self.print_error("validated checkpoint", self.checkpoint_height)
        if bitcoin.TESTNET:
            return
        if bits != header.get('bits'):
            raise BaseException("bits mismatch: %s vs %s" % (bits, header.get('bits')))
        if int('0x' + _hash, 16) > target:
            raise BaseException("insufficient proof of work: %s vs target %s" % (int('0x' + _hash, 16), target))

    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')
            bits, target = self.get_target(height / 2016, chain)
            self.verify_header(header, prev_header, bits, target)
            prev_header = header

    def verify_chunk(self, index, data):
        num = len(data) / 80
        prev_header = None
        if index != 0:
            prev_header = self.read_header(index*2016 - 1)
        bits, target = self.get_target(index)
        for i in range(num):
            raw_header = data[i*80:(i+1) * 80]
            header = self.deserialize_header(raw_header, index*2016 + i)
            self.verify_header(header, prev_header, bits, target)
            prev_header = header

    def serialize_header(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 deserialize_header(self, s, height):
        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])
        h['block_height'] = height
        return h

    def hash_header(self, header):
        if header is None:
            return '0' * 64
        return hash_encode(Hash(self.serialize_header(header).decode('hex')))

    def path(self):
        return util.get_headers_path(self.config)

    def init_headers_file(self):
        filename = self.path()
        try:
            import urllib, socket
            socket.setdefaulttimeout(30)
            self.print_error("downloading ", bitcoin.HEADERS_URL)
            urllib.urlretrieve(bitcoin.HEADERS_URL, filename + '.tmp')
            os.rename(filename + '.tmp', filename)
            self.print_error("done.")
        except Exception:
            self.print_error("download failed. creating file", filename)
            open(filename, 'wb+').close()
        self.downloading_headers = False
        self.set_local_height()
        self.print_error("%d blocks" % self.local_height)

    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.serialize_header(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):
        self.local_height = 0
        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.deserialize_header(h, block_height)
                return h

    def BIP9(self, height, flag):
        v = self.read_header(height)['version']
        return ((v & 0xE0000000) == 0x20000000) and ((v & flag) == flag)

    def segwit_support(self, N=144):
        h = self.local_height
        return sum([self.BIP9(h-i, 2) for i in range(N)])*10000/N/100.

    def check_truncate_headers(self):
        checkpoint = self.read_header(self.checkpoint_height)
        if checkpoint is None:
            return
        if self.hash_header(checkpoint) == self.checkpoint_hash:
            return
        self.print_error('checkpoint mismatch:', self.hash_header(checkpoint), self.checkpoint_hash)
        self.truncate_headers(self.checkpoint_height)

    def truncate_headers(self, height):
        self.print_error('Truncating headers file at height %d'%height)
        name = self.path()
        f = open(name, 'rb+')
        f.seek(height * 80)
        f.truncate()
        f.close()

    def get_target(self, index, chain=None):
        if bitcoin.TESTNET:
            return 0, 0
        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
        assert last is not None
        # bits to target
        bits = last.get('bits')
        bitsN = (bits >> 24) & 0xff
        if not (bitsN >= 0x03 and bitsN <= 0x1d):
            raise BaseException("First part of bits should be in [0x03, 0x1d]")
        bitsBase = bits & 0xffffff
        if not (bitsBase >= 0x8000 and bitsBase <= 0x7fffff):
            raise BaseException("Second part of bits should be in [0x8000, 0x7fffff]")
        target = bitsBase << (8 * (bitsN-3))
        # new target
        nActualTimespan = last.get('timestamp') - first.get('timestamp')
        nTargetTimespan = 14 * 24 * 60 * 60
        nActualTimespan = max(nActualTimespan, nTargetTimespan / 4)
        nActualTimespan = min(nActualTimespan, nTargetTimespan * 4)
        new_target = min(MAX_TARGET, (target*nActualTimespan) / nTargetTimespan)
        # convert new target to bits
        c = ("%064x" % new_target)[2:]
        while c[:2] == '00' and len(c) > 6:
            c = c[2:]
        bitsN, bitsBase = len(c) / 2, int('0x' + c[:6], 16)
        if bitsBase >= 0x800000:
            bitsN += 1
            bitsBase >>= 8
        new_bits = bitsN << 24 | bitsBase
        return new_bits, bitsBase << (8 * (bitsN-3))

    def can_connect(self, header):
        previous_height = header['block_height'] - 1
        previous_header = self.read_header(previous_height)
        if not previous_header:
            return False
        prev_hash = self.hash_header(previous_header)
        if prev_hash != header.get('prev_block_hash'):
            return False
        height = header.get('block_height')
        bits, target = self.get_target(height / 2016)
        try:
            self.verify_header(header, previous_header, bits, target)
        except:
            return False
        return True

    def connect_chunk(self, idx, hexdata):
        try:
            data = hexdata.decode('hex')
            self.verify_chunk(idx, data)
            self.print_error("validated chunk %d" % idx)
            self.save_chunk(idx, data)
            return True
        except BaseException as e:
            self.print_error('verify_chunk failed', str(e))
            return False

    def get_checkpoint(self):
        height = self.config.get('checkpoint_height', 0)
        value = self.config.get('checkpoint_value', bitcoin.GENESIS)
        return (height, value)

    def set_checkpoint(self, height, value):
        self.checkpoint_height = height
        self.checkpoint_hash = value
        self.config.set_key('checkpoint_height', height)
        self.config.set_key('checkpoint_value', value)
        self.check_truncate_headers()