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633 lines
25 KiB
633 lines
25 KiB
# Electrum - lightweight Bitcoin client
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# Copyright (C) 2012 thomasv@ecdsa.org
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#
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# Permission is hereby granted, free of charge, to any person
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# obtaining a copy of this software and associated documentation files
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# (the "Software"), to deal in the Software without restriction,
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# including without limitation the rights to use, copy, modify, merge,
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# publish, distribute, sublicense, and/or sell copies of the Software,
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# and to permit persons to whom the Software is furnished to do so,
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# subject to the following conditions:
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#
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# The above copyright notice and this permission notice shall be
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# included in all copies or substantial portions of the Software.
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#
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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# SOFTWARE.
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import os
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import threading
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from typing import Optional, Dict, Mapping, Sequence
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from . import util
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from .bitcoin import hash_encode, int_to_hex, rev_hex
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from .crypto import sha256d
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from . import constants
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from .util import bfh, bh2u
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from .simple_config import SimpleConfig
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from .logging import get_logger, Logger
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_logger = get_logger(__name__)
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HEADER_SIZE = 80 # bytes
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MAX_TARGET = 0x00000000FFFF0000000000000000000000000000000000000000000000000000
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class MissingHeader(Exception):
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pass
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class InvalidHeader(Exception):
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pass
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def serialize_header(header_dict: dict) -> str:
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s = int_to_hex(header_dict['version'], 4) \
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+ rev_hex(header_dict['prev_block_hash']) \
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+ rev_hex(header_dict['merkle_root']) \
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+ int_to_hex(int(header_dict['timestamp']), 4) \
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+ int_to_hex(int(header_dict['bits']), 4) \
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+ int_to_hex(int(header_dict['nonce']), 4)
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return s
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def deserialize_header(s: bytes, height: int) -> dict:
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if not s:
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raise InvalidHeader('Invalid header: {}'.format(s))
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if len(s) != HEADER_SIZE:
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raise InvalidHeader('Invalid header length: {}'.format(len(s)))
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hex_to_int = lambda s: int.from_bytes(s, byteorder='little')
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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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h['block_height'] = height
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return h
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def hash_header(header: dict) -> str:
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if header is None:
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return '0' * 64
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if header.get('prev_block_hash') is None:
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header['prev_block_hash'] = '00'*32
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return hash_raw_header(serialize_header(header))
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def hash_raw_header(header: str) -> str:
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return hash_encode(sha256d(bfh(header)))
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# key: blockhash hex at forkpoint
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# the chain at some key is the best chain that includes the given hash
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blockchains = {} # type: Dict[str, Blockchain]
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blockchains_lock = threading.RLock()
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def read_blockchains(config: 'SimpleConfig'):
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best_chain = Blockchain(config=config,
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forkpoint=0,
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parent=None,
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forkpoint_hash=constants.net.GENESIS,
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prev_hash=None)
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blockchains[constants.net.GENESIS] = best_chain
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# consistency checks
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if best_chain.height() > constants.net.max_checkpoint():
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header_after_cp = best_chain.read_header(constants.net.max_checkpoint()+1)
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if not header_after_cp or not best_chain.can_connect(header_after_cp, check_height=False):
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_logger.info("[blockchain] deleting best chain. cannot connect header after last cp to last cp.")
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os.unlink(best_chain.path())
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best_chain.update_size()
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# forks
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fdir = os.path.join(util.get_headers_dir(config), 'forks')
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util.make_dir(fdir)
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# files are named as: fork2_{forkpoint}_{prev_hash}_{first_hash}
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l = filter(lambda x: x.startswith('fork2_') and '.' not in x, os.listdir(fdir))
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l = sorted(l, key=lambda x: int(x.split('_')[1])) # sort by forkpoint
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def delete_chain(filename, reason):
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_logger.info(f"[blockchain] deleting chain {filename}: {reason}")
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os.unlink(os.path.join(fdir, filename))
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def instantiate_chain(filename):
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__, forkpoint, prev_hash, first_hash = filename.split('_')
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forkpoint = int(forkpoint)
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prev_hash = (64-len(prev_hash)) * "0" + prev_hash # left-pad with zeroes
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first_hash = (64-len(first_hash)) * "0" + first_hash
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# forks below the max checkpoint are not allowed
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if forkpoint <= constants.net.max_checkpoint():
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delete_chain(filename, "deleting fork below max checkpoint")
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return
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# find parent (sorting by forkpoint guarantees it's already instantiated)
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for parent in blockchains.values():
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if parent.check_hash(forkpoint - 1, prev_hash):
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break
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else:
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delete_chain(filename, "cannot find parent for chain")
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return
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b = Blockchain(config=config,
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forkpoint=forkpoint,
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parent=parent,
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forkpoint_hash=first_hash,
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prev_hash=prev_hash)
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# consistency checks
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h = b.read_header(b.forkpoint)
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if first_hash != hash_header(h):
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delete_chain(filename, "incorrect first hash for chain")
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return
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if not b.parent.can_connect(h, check_height=False):
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delete_chain(filename, "cannot connect chain to parent")
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return
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chain_id = b.get_id()
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assert first_hash == chain_id, (first_hash, chain_id)
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blockchains[chain_id] = b
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for filename in l:
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instantiate_chain(filename)
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def get_best_chain() -> 'Blockchain':
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return blockchains[constants.net.GENESIS]
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# block hash -> chain work; up to and including that block
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_CHAINWORK_CACHE = {
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"0000000000000000000000000000000000000000000000000000000000000000": 0, # virtual block at height -1
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} # type: Dict[str, int]
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class Blockchain(Logger):
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"""
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Manages blockchain headers and their verification
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"""
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def __init__(self, config: SimpleConfig, forkpoint: int, parent: Optional['Blockchain'],
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forkpoint_hash: str, prev_hash: Optional[str]):
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assert isinstance(forkpoint_hash, str) and len(forkpoint_hash) == 64, forkpoint_hash
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assert (prev_hash is None) or (isinstance(prev_hash, str) and len(prev_hash) == 64), prev_hash
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# assert (parent is None) == (forkpoint == 0)
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if 0 < forkpoint <= constants.net.max_checkpoint():
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raise Exception(f"cannot fork below max checkpoint. forkpoint: {forkpoint}")
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Logger.__init__(self)
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self.config = config
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self.forkpoint = forkpoint # height of first header
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self.parent = parent
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self._forkpoint_hash = forkpoint_hash # blockhash at forkpoint. "first hash"
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self._prev_hash = prev_hash # blockhash immediately before forkpoint
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self.lock = threading.RLock()
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self.update_size()
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def with_lock(func):
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def func_wrapper(self, *args, **kwargs):
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with self.lock:
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return func(self, *args, **kwargs)
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return func_wrapper
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@property
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def checkpoints(self):
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return constants.net.CHECKPOINTS
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def get_max_child(self) -> Optional[int]:
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children = self.get_direct_children()
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return max([x.forkpoint for x in children]) if children else None
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def get_max_forkpoint(self) -> int:
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"""Returns the max height where there is a fork
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related to this chain.
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"""
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mc = self.get_max_child()
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return mc if mc is not None else self.forkpoint
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def get_direct_children(self) -> Sequence['Blockchain']:
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with blockchains_lock:
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return list(filter(lambda y: y.parent==self, blockchains.values()))
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def get_parent_heights(self) -> Mapping['Blockchain', int]:
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"""Returns map: (parent chain -> height of last common block)"""
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with blockchains_lock:
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result = {self: self.height()}
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chain = self
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while True:
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parent = chain.parent
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if parent is None: break
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result[parent] = chain.forkpoint - 1
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chain = parent
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return result
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def get_height_of_last_common_block_with_chain(self, other_chain: 'Blockchain') -> int:
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last_common_block_height = 0
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our_parents = self.get_parent_heights()
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their_parents = other_chain.get_parent_heights()
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for chain in our_parents:
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if chain in their_parents:
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h = min(our_parents[chain], their_parents[chain])
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last_common_block_height = max(last_common_block_height, h)
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return last_common_block_height
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@with_lock
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def get_branch_size(self) -> int:
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return self.height() - self.get_max_forkpoint() + 1
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def get_name(self) -> str:
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return self.get_hash(self.get_max_forkpoint()).lstrip('0')[0:10]
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def check_header(self, header: dict) -> bool:
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header_hash = hash_header(header)
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height = header.get('block_height')
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return self.check_hash(height, header_hash)
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def check_hash(self, height: int, header_hash: str) -> bool:
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"""Returns whether the hash of the block at given height
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is the given hash.
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"""
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assert isinstance(header_hash, str) and len(header_hash) == 64, header_hash # hex
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try:
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return header_hash == self.get_hash(height)
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except Exception:
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return False
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def fork(parent, header: dict) -> 'Blockchain':
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if not parent.can_connect(header, check_height=False):
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raise Exception("forking header does not connect to parent chain")
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forkpoint = header.get('block_height')
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self = Blockchain(config=parent.config,
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forkpoint=forkpoint,
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parent=parent,
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forkpoint_hash=hash_header(header),
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prev_hash=parent.get_hash(forkpoint-1))
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open(self.path(), 'w+').close()
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self.save_header(header)
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# put into global dict. note that in some cases
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# save_header might have already put it there but that's OK
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chain_id = self.get_id()
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with blockchains_lock:
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blockchains[chain_id] = self
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return self
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@with_lock
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def height(self) -> int:
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return self.forkpoint + self.size() - 1
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@with_lock
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def size(self) -> int:
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return self._size
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@with_lock
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def update_size(self) -> None:
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p = self.path()
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self._size = os.path.getsize(p)//HEADER_SIZE if os.path.exists(p) else 0
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@classmethod
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def verify_header(cls, header: dict, prev_hash: str, target: int, expected_header_hash: str=None) -> None:
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_hash = hash_header(header)
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if expected_header_hash and expected_header_hash != _hash:
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raise Exception("hash mismatches with expected: {} vs {}".format(expected_header_hash, _hash))
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if prev_hash != header.get('prev_block_hash'):
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raise Exception("prev hash mismatch: %s vs %s" % (prev_hash, header.get('prev_block_hash')))
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if constants.net.TESTNET:
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return
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bits = cls.target_to_bits(target)
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if bits != header.get('bits'):
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raise Exception("bits mismatch: %s vs %s" % (bits, header.get('bits')))
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block_hash_as_num = int.from_bytes(bfh(_hash), byteorder='big')
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if block_hash_as_num > target:
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raise Exception(f"insufficient proof of work: {block_hash_as_num} vs target {target}")
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def verify_chunk(self, index: int, data: bytes) -> None:
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num = len(data) // HEADER_SIZE
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start_height = index * 2016
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prev_hash = self.get_hash(start_height - 1)
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target = self.get_target(index-1)
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for i in range(num):
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height = start_height + i
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try:
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expected_header_hash = self.get_hash(height)
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except MissingHeader:
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expected_header_hash = None
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raw_header = data[i*HEADER_SIZE : (i+1)*HEADER_SIZE]
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header = deserialize_header(raw_header, index*2016 + i)
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self.verify_header(header, prev_hash, target, expected_header_hash)
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prev_hash = hash_header(header)
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@with_lock
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def path(self):
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d = util.get_headers_dir(self.config)
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if self.parent is None:
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filename = 'blockchain_headers'
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else:
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assert self.forkpoint > 0, self.forkpoint
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prev_hash = self._prev_hash.lstrip('0')
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first_hash = self._forkpoint_hash.lstrip('0')
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basename = f'fork2_{self.forkpoint}_{prev_hash}_{first_hash}'
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filename = os.path.join('forks', basename)
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return os.path.join(d, filename)
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@with_lock
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def save_chunk(self, index: int, chunk: bytes):
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assert index >= 0, index
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chunk_within_checkpoint_region = index < len(self.checkpoints)
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# chunks in checkpoint region are the responsibility of the 'main chain'
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if chunk_within_checkpoint_region and self.parent is not None:
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main_chain = get_best_chain()
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main_chain.save_chunk(index, chunk)
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return
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delta_height = (index * 2016 - self.forkpoint)
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delta_bytes = delta_height * HEADER_SIZE
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# if this chunk contains our forkpoint, only save the part after forkpoint
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# (the part before is the responsibility of the parent)
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if delta_bytes < 0:
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chunk = chunk[-delta_bytes:]
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delta_bytes = 0
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truncate = not chunk_within_checkpoint_region
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self.write(chunk, delta_bytes, truncate)
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self.swap_with_parent()
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def swap_with_parent(self) -> None:
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with self.lock, blockchains_lock:
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# do the swap; possibly multiple ones
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cnt = 0
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while True:
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old_parent = self.parent
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if not self._swap_with_parent():
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break
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# make sure we are making progress
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cnt += 1
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if cnt > len(blockchains):
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raise Exception(f'swapping fork with parent too many times: {cnt}')
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# we might have become the parent of some of our former siblings
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for old_sibling in old_parent.get_direct_children():
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if self.check_hash(old_sibling.forkpoint - 1, old_sibling._prev_hash):
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old_sibling.parent = self
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def _swap_with_parent(self) -> bool:
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"""Check if this chain became stronger than its parent, and swap
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the underlying files if so. The Blockchain instances will keep
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'containing' the same headers, but their ids change and so
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they will be stored in different files."""
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if self.parent is None:
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return False
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if self.parent.get_chainwork() >= self.get_chainwork():
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return False
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self.logger.info(f"swapping {self.forkpoint} {self.parent.forkpoint}")
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parent_branch_size = self.parent.height() - self.forkpoint + 1
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forkpoint = self.forkpoint # type: Optional[int]
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parent = self.parent # type: Optional[Blockchain]
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child_old_id = self.get_id()
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parent_old_id = parent.get_id()
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# swap files
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# child takes parent's name
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# parent's new name will be something new (not child's old name)
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self.assert_headers_file_available(self.path())
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child_old_name = self.path()
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with open(self.path(), 'rb') as f:
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my_data = f.read()
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self.assert_headers_file_available(parent.path())
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assert forkpoint > parent.forkpoint, (f"forkpoint of parent chain ({parent.forkpoint}) "
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f"should be at lower height than children's ({forkpoint})")
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with open(parent.path(), 'rb') as f:
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f.seek((forkpoint - parent.forkpoint)*HEADER_SIZE)
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parent_data = f.read(parent_branch_size*HEADER_SIZE)
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self.write(parent_data, 0)
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parent.write(my_data, (forkpoint - parent.forkpoint)*HEADER_SIZE)
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# swap parameters
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self.parent, parent.parent = parent.parent, self # type: Optional[Blockchain], Optional[Blockchain]
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self.forkpoint, parent.forkpoint = parent.forkpoint, self.forkpoint
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self._forkpoint_hash, parent._forkpoint_hash = parent._forkpoint_hash, hash_raw_header(bh2u(parent_data[:HEADER_SIZE]))
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self._prev_hash, parent._prev_hash = parent._prev_hash, self._prev_hash
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# parent's new name
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os.replace(child_old_name, parent.path())
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self.update_size()
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parent.update_size()
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# update pointers
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blockchains.pop(child_old_id, None)
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blockchains.pop(parent_old_id, None)
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blockchains[self.get_id()] = self
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blockchains[parent.get_id()] = parent
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return True
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def get_id(self) -> str:
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return self._forkpoint_hash
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def assert_headers_file_available(self, path):
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if os.path.exists(path):
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return
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elif not os.path.exists(util.get_headers_dir(self.config)):
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raise FileNotFoundError('Electrum headers_dir does not exist. Was it deleted while running?')
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else:
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raise FileNotFoundError('Cannot find headers file but headers_dir is there. Should be at {}'.format(path))
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@with_lock
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def write(self, data: bytes, offset: int, truncate: bool=True) -> None:
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filename = self.path()
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self.assert_headers_file_available(filename)
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with open(filename, 'rb+') as f:
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if truncate and offset != self._size * HEADER_SIZE:
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f.seek(offset)
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f.truncate()
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f.seek(offset)
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f.write(data)
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f.flush()
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os.fsync(f.fileno())
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self.update_size()
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@with_lock
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def save_header(self, header: dict) -> None:
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delta = header.get('block_height') - self.forkpoint
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data = bfh(serialize_header(header))
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# headers are only _appended_ to the end:
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assert delta == self.size(), (delta, self.size())
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assert len(data) == HEADER_SIZE
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self.write(data, delta*HEADER_SIZE)
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self.swap_with_parent()
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@with_lock
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def read_header(self, height: int) -> Optional[dict]:
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if height < 0:
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return
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if height < self.forkpoint:
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return self.parent.read_header(height)
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if height > self.height():
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return
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delta = height - self.forkpoint
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name = self.path()
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self.assert_headers_file_available(name)
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with open(name, 'rb') as f:
|
|
f.seek(delta * HEADER_SIZE)
|
|
h = f.read(HEADER_SIZE)
|
|
if len(h) < HEADER_SIZE:
|
|
raise Exception('Expected to read a full header. This was only {} bytes'.format(len(h)))
|
|
if h == bytes([0])*HEADER_SIZE:
|
|
return None
|
|
return deserialize_header(h, height)
|
|
|
|
def header_at_tip(self) -> Optional[dict]:
|
|
"""Return latest header."""
|
|
height = self.height()
|
|
return self.read_header(height)
|
|
|
|
def get_hash(self, height: int) -> str:
|
|
def is_height_checkpoint():
|
|
within_cp_range = height <= constants.net.max_checkpoint()
|
|
at_chunk_boundary = (height+1) % 2016 == 0
|
|
return within_cp_range and at_chunk_boundary
|
|
|
|
if height == -1:
|
|
return '0000000000000000000000000000000000000000000000000000000000000000'
|
|
elif height == 0:
|
|
return constants.net.GENESIS
|
|
elif is_height_checkpoint():
|
|
index = height // 2016
|
|
h, t = self.checkpoints[index]
|
|
return h
|
|
else:
|
|
header = self.read_header(height)
|
|
if header is None:
|
|
raise MissingHeader(height)
|
|
return hash_header(header)
|
|
|
|
def get_target(self, index: int) -> int:
|
|
# compute target from chunk x, used in chunk x+1
|
|
if constants.net.TESTNET:
|
|
return 0
|
|
if index == -1:
|
|
return MAX_TARGET
|
|
if index < len(self.checkpoints):
|
|
h, t = self.checkpoints[index]
|
|
return t
|
|
# new target
|
|
first = self.read_header(index * 2016)
|
|
last = self.read_header(index * 2016 + 2015)
|
|
if not first or not last:
|
|
raise MissingHeader()
|
|
bits = last.get('bits')
|
|
target = self.bits_to_target(bits)
|
|
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)
|
|
# not any target can be represented in 32 bits:
|
|
new_target = self.bits_to_target(self.target_to_bits(new_target))
|
|
return new_target
|
|
|
|
@classmethod
|
|
def bits_to_target(cls, bits: int) -> int:
|
|
bitsN = (bits >> 24) & 0xff
|
|
if not (0x03 <= bitsN <= 0x1d):
|
|
raise Exception("First part of bits should be in [0x03, 0x1d]")
|
|
bitsBase = bits & 0xffffff
|
|
if not (0x8000 <= bitsBase <= 0x7fffff):
|
|
raise Exception("Second part of bits should be in [0x8000, 0x7fffff]")
|
|
return bitsBase << (8 * (bitsN-3))
|
|
|
|
@classmethod
|
|
def target_to_bits(cls, target: int) -> int:
|
|
c = ("%064x" % target)[2:]
|
|
while c[:2] == '00' and len(c) > 6:
|
|
c = c[2:]
|
|
bitsN, bitsBase = len(c) // 2, int.from_bytes(bfh(c[:6]), byteorder='big')
|
|
if bitsBase >= 0x800000:
|
|
bitsN += 1
|
|
bitsBase >>= 8
|
|
return bitsN << 24 | bitsBase
|
|
|
|
def chainwork_of_header_at_height(self, height: int) -> int:
|
|
"""work done by single header at given height"""
|
|
chunk_idx = height // 2016 - 1
|
|
target = self.get_target(chunk_idx)
|
|
work = ((2 ** 256 - target - 1) // (target + 1)) + 1
|
|
return work
|
|
|
|
@with_lock
|
|
def get_chainwork(self, height=None) -> int:
|
|
if height is None:
|
|
height = max(0, self.height())
|
|
if constants.net.TESTNET:
|
|
# On testnet/regtest, difficulty works somewhat different.
|
|
# It's out of scope to properly implement that.
|
|
return height
|
|
last_retarget = height // 2016 * 2016 - 1
|
|
cached_height = last_retarget
|
|
while _CHAINWORK_CACHE.get(self.get_hash(cached_height)) is None:
|
|
if cached_height <= -1:
|
|
break
|
|
cached_height -= 2016
|
|
assert cached_height >= -1, cached_height
|
|
running_total = _CHAINWORK_CACHE[self.get_hash(cached_height)]
|
|
while cached_height < last_retarget:
|
|
cached_height += 2016
|
|
work_in_single_header = self.chainwork_of_header_at_height(cached_height)
|
|
work_in_chunk = 2016 * work_in_single_header
|
|
running_total += work_in_chunk
|
|
_CHAINWORK_CACHE[self.get_hash(cached_height)] = running_total
|
|
cached_height += 2016
|
|
work_in_single_header = self.chainwork_of_header_at_height(cached_height)
|
|
work_in_last_partial_chunk = (height % 2016 + 1) * work_in_single_header
|
|
return running_total + work_in_last_partial_chunk
|
|
|
|
def can_connect(self, header: dict, check_height: bool=True) -> bool:
|
|
if header is None:
|
|
return False
|
|
height = header['block_height']
|
|
if check_height and self.height() != height - 1:
|
|
return False
|
|
if height == 0:
|
|
return hash_header(header) == constants.net.GENESIS
|
|
try:
|
|
prev_hash = self.get_hash(height - 1)
|
|
except:
|
|
return False
|
|
if prev_hash != header.get('prev_block_hash'):
|
|
return False
|
|
try:
|
|
target = self.get_target(height // 2016 - 1)
|
|
except MissingHeader:
|
|
return False
|
|
try:
|
|
self.verify_header(header, prev_hash, target)
|
|
except BaseException as e:
|
|
return False
|
|
return True
|
|
|
|
def connect_chunk(self, idx: int, hexdata: str) -> bool:
|
|
assert idx >= 0, idx
|
|
try:
|
|
data = bfh(hexdata)
|
|
self.verify_chunk(idx, data)
|
|
self.save_chunk(idx, data)
|
|
return True
|
|
except BaseException as e:
|
|
self.logger.info(f'verify_chunk idx {idx} failed: {repr(e)}')
|
|
return False
|
|
|
|
def get_checkpoints(self):
|
|
# for each chunk, store the hash of the last block and the target after the chunk
|
|
cp = []
|
|
n = self.height() // 2016
|
|
for index in range(n):
|
|
h = self.get_hash((index+1) * 2016 -1)
|
|
target = self.get_target(index)
|
|
cp.append((h, target))
|
|
return cp
|
|
|
|
|
|
def check_header(header: dict) -> Optional[Blockchain]:
|
|
if type(header) is not dict:
|
|
return None
|
|
with blockchains_lock: chains = list(blockchains.values())
|
|
for b in chains:
|
|
if b.check_header(header):
|
|
return b
|
|
return None
|
|
|
|
|
|
def can_connect(header: dict) -> Optional[Blockchain]:
|
|
with blockchains_lock: chains = list(blockchains.values())
|
|
for b in chains:
|
|
if b.can_connect(header):
|
|
return b
|
|
return None
|
|
|