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blockchain.py: better handling of missing headers. more restrictive verify_chunk.

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SomberNight 2018-08-31 16:32:45 +02:00
parent 2157eae499
commit 3f0d79f07d
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1 changed files with 25 additions and 7 deletions
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30
electrum/blockchain.py
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@ -146,7 +146,10 @@ class Blockchain(util.PrintError):
def check_header(self, header):
header_hash = hash_header(header)
height = header.get('block_height')
try:
return header_hash == self.get_hash(height)
except MissingHeader:
return False
def fork(parent, header):
forkpoint = header.get('block_height')
@ -166,8 +169,10 @@ class Blockchain(util.PrintError):
p = self.path()
self._size = os.path.getsize(p)//80 if os.path.exists(p) else 0
def verify_header(self, header, prev_hash, target):
def verify_header(self, header, prev_hash, target, expected_header_hash=None):
_hash = hash_header(header)
if expected_header_hash and expected_header_hash != _hash:
raise Exception("hash mismatches with expected: {} vs {}".format(expected_header_hash, _hash))
if prev_hash != header.get('prev_block_hash'):
raise Exception("prev hash mismatch: %s vs %s" % (prev_hash, header.get('prev_block_hash')))
if constants.net.TESTNET:
@ -180,12 +185,18 @@ class Blockchain(util.PrintError):
def verify_chunk(self, index, data):
num = len(data) // 80
prev_hash = self.get_hash(index * 2016 - 1)
start_height = index * 2016
prev_hash = self.get_hash(start_height - 1)
target = self.get_target(index-1)
for i in range(num):
height = start_height + i
try:
expected_header_hash = self.get_hash(height)
except MissingHeader:
expected_header_hash = None
raw_header = data[i*80:(i+1) * 80]
header = deserialize_header(raw_header, index*2016 + i)
self.verify_header(header, prev_hash, target)
self.verify_header(header, prev_hash, target, expected_header_hash)
prev_hash = hash_header(header)
def path(self):
@ -303,17 +314,24 @@ class Blockchain(util.PrintError):
return deserialize_header(h, height)
def get_hash(self, height):
def is_height_checkpoint():
within_cp_range = height < len(self.checkpoints) * 2016
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 height < len(self.checkpoints) * 2016:
assert (height+1) % 2016 == 0, (height, len(self.checkpoints), (height+1) % 2016)
elif is_height_checkpoint():
index = height // 2016
h, t = self.checkpoints[index]
return h
else:
return hash_header(self.read_header(height))
header = self.read_header(height)
if header is None:
raise MissingHeader(height)
return hash_header(header)
def get_target(self, index):
# compute target from chunk x, used in chunk x+1