83 lines
3.6 KiB
Python
83 lines
3.6 KiB
Python
import struct
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import binascii
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from lbry.crypto.hash import double_sha256
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class InvalidProofError(Exception):
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pass
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def get_hash_for_outpoint(txhash, nout, height_of_last_takeover):
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return double_sha256(
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double_sha256(txhash) +
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double_sha256(str(nout).encode()) +
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double_sha256(struct.pack('>Q', height_of_last_takeover))
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)
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# noinspection PyPep8
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def verify_proof(proof, root_hash, name):
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previous_computed_hash = None
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reverse_computed_name = ''
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verified_value = False
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for i, node in enumerate(proof['nodes'][::-1]):
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found_child_in_chain = False
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to_hash = b''
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previous_child_character = None
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for child in node['children']:
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if child['character'] < 0 or child['character'] > 255:
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raise InvalidProofError("child character not int between 0 and 255")
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if previous_child_character:
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if previous_child_character >= child['character']:
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raise InvalidProofError("children not in increasing order")
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previous_child_character = child['character']
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to_hash += bytes((child['character'],))
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if 'nodeHash' in child:
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if len(child['nodeHash']) != 64:
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raise InvalidProofError("invalid child nodeHash")
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to_hash += binascii.unhexlify(child['nodeHash'])[::-1]
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else:
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if previous_computed_hash is None:
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raise InvalidProofError("previous computed hash is None")
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if found_child_in_chain is True:
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raise InvalidProofError("already found the next child in the chain")
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found_child_in_chain = True
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reverse_computed_name += chr(child['character'])
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to_hash += previous_computed_hash
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if not found_child_in_chain:
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if i != 0:
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raise InvalidProofError("did not find the alleged child")
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if i == 0 and 'txhash' in proof and 'nOut' in proof and 'last takeover height' in proof:
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if len(proof['txhash']) != 64:
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raise InvalidProofError(f"txhash was invalid: {proof['txhash']}")
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if not isinstance(proof['nOut'], int):
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raise InvalidProofError(f"nOut was invalid: {proof['nOut']}")
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if not isinstance(proof['last takeover height'], int):
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raise InvalidProofError(
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f"last takeover height was invalid: {proof['last takeover height']}")
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to_hash += get_hash_for_outpoint(
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binascii.unhexlify(proof['txhash'])[::-1],
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proof['nOut'],
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proof['last takeover height']
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)
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verified_value = True
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elif 'valueHash' in node:
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if len(node['valueHash']) != 64:
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raise InvalidProofError("valueHash was invalid")
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to_hash += binascii.unhexlify(node['valueHash'])[::-1]
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previous_computed_hash = double_sha256(to_hash)
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if previous_computed_hash != binascii.unhexlify(root_hash)[::-1]:
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raise InvalidProofError("computed hash does not match roothash")
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if 'txhash' in proof and 'nOut' in proof:
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if not verified_value:
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raise InvalidProofError("mismatch between proof claim and outcome")
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target = reverse_computed_name[::-1].encode('ISO-8859-1').decode()
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if 'txhash' in proof and 'nOut' in proof:
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if name != target:
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raise InvalidProofError("name did not match proof")
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if not name.startswith(target):
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raise InvalidProofError("name fragment does not match proof")
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return True
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