335 lines
13 KiB
Python
335 lines
13 KiB
Python
from bigchaindb.common.crypto import hash_data, PublicKey, PrivateKey
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from bigchaindb.common.exceptions import (InvalidHash, InvalidSignature,
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OperationError, DoubleSpend,
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TransactionDoesNotExist,
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TransactionNotInValidBlock,
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AssetIdMismatch, AmountError)
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from bigchaindb.common.transaction import Transaction
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from bigchaindb.common.utils import gen_timestamp, serialize
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from bigchaindb.common.schema import validate_transaction_schema
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class Transaction(Transaction):
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def validate(self, bigchain):
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"""Validate a transaction.
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Args:
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bigchain (Bigchain): an instantiated bigchaindb.Bigchain object.
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Returns:
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The transaction (Transaction) if the transaction is valid else it
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raises an exception describing the reason why the transaction is
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invalid.
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Raises:
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OperationError: if the transaction operation is not supported
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TransactionDoesNotExist: if the input of the transaction is not
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found
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TransactionNotInValidBlock: if the input of the transaction is not
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in a valid block
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TransactionOwnerError: if the new transaction is using an input it
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doesn't own
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DoubleSpend: if the transaction is a double spend
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InvalidHash: if the hash of the transaction is wrong
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InvalidSignature: if the signature of the transaction is wrong
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"""
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if len(self.inputs) == 0:
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raise ValueError('Transaction contains no inputs')
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input_conditions = []
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inputs_defined = all([input_.fulfills for input_ in self.inputs])
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# validate amounts
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if any(output.amount < 1 for output in self.outputs):
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raise AmountError('`amount` needs to be greater than zero')
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if self.operation in (Transaction.CREATE, Transaction.GENESIS):
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# validate asset
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if self.asset['data'] is not None and not isinstance(self.asset['data'], dict):
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raise TypeError(('`asset.data` must be a dict instance or '
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'None for `CREATE` transactions'))
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# validate inputs
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if inputs_defined:
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raise ValueError('A CREATE operation has no inputs')
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elif self.operation == Transaction.TRANSFER:
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# validate asset
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if not isinstance(self.asset['id'], str):
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raise ValueError(('`asset.id` must be a string for '
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'`TRANSFER` transations'))
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# check inputs
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if not inputs_defined:
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raise ValueError('Only `CREATE` transactions can have null '
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'inputs')
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# store the inputs so that we can check if the asset ids match
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input_txs = []
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for input_ in self.inputs:
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input_txid = input_.fulfills.txid
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input_tx, status = bigchain.\
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get_transaction(input_txid, include_status=True)
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if input_tx is None:
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raise TransactionDoesNotExist("input `{}` doesn't exist"
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.format(input_txid))
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if status != bigchain.TX_VALID:
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raise TransactionNotInValidBlock(
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'input `{}` does not exist in a valid block'.format(
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input_txid))
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spent = bigchain.get_spent(input_txid, input_.fulfills.output)
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if spent and spent.id != self.id:
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raise DoubleSpend('input `{}` was already spent'
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.format(input_txid))
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output = input_tx.outputs[input_.fulfills.output]
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input_conditions.append(output)
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input_txs.append(input_tx)
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if output.amount < 1:
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raise AmountError('`amount` needs to be greater than zero')
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# validate asset id
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asset_id = Transaction.get_asset_id(input_txs)
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if asset_id != self.asset['id']:
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raise AssetIdMismatch(('The asset id of the input does not'
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' match the asset id of the'
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' transaction'))
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# validate the amounts
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for output in self.outputs:
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if output.amount < 1:
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raise AmountError('`amount` needs to be greater than zero')
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input_amount = sum([input_condition.amount for input_condition in input_conditions])
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output_amount = sum([output_condition.amount for output_condition in self.outputs])
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if output_amount != input_amount:
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raise AmountError(('The amount used in the inputs `{}`'
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' needs to be same as the amount used'
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' in the outputs `{}`')
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.format(input_amount, output_amount))
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else:
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allowed_operations = ', '.join(Transaction.ALLOWED_OPERATIONS)
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raise TypeError('`operation`: `{}` must be either {}.'
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.format(self.operation, allowed_operations))
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if not self.inputs_valid(input_conditions):
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raise InvalidSignature()
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return self
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@classmethod
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def from_dict(cls, tx_body):
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validate_transaction_schema(tx_body)
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return super().from_dict(tx_body)
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class Block(object):
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"""Bundle a list of Transactions in a Block. Nodes vote on its validity.
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Attributes:
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transaction (:obj:`list` of :class:`~.Transaction`):
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Transactions to be included in the Block.
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node_pubkey (str): The public key of the node creating the
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Block.
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timestamp (str): The Unix time a Block was created.
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voters (:obj:`list` of :obj:`str`): A list of a federation
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nodes' public keys supposed to vote on the Block.
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signature (str): A cryptographic signature ensuring the
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integrity and validity of the creator of a Block.
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"""
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def __init__(self, transactions=None, node_pubkey=None, timestamp=None,
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voters=None, signature=None):
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"""The Block model is mainly used for (de)serialization and integrity
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checking.
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Args:
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transaction (:obj:`list` of :class:`~.Transaction`):
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Transactions to be included in the Block.
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node_pubkey (str): The public key of the node creating the
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Block.
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timestamp (str): The Unix time a Block was created.
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voters (:obj:`list` of :obj:`str`): A list of a federation
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nodes' public keys supposed to vote on the Block.
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signature (str): A cryptographic signature ensuring the
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integrity and validity of the creator of a Block.
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"""
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if transactions is not None and not isinstance(transactions, list):
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raise TypeError('`transactions` must be a list instance or None')
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else:
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self.transactions = transactions or []
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if voters is not None and not isinstance(voters, list):
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raise TypeError('`voters` must be a list instance or None')
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else:
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self.voters = voters or []
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if timestamp is not None:
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self.timestamp = timestamp
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else:
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self.timestamp = gen_timestamp()
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self.node_pubkey = node_pubkey
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self.signature = signature
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def __eq__(self, other):
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try:
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other = other.to_dict()
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except AttributeError:
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return False
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return self.to_dict() == other
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def validate(self, bigchain):
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"""Validate the Block.
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Args:
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bigchain (:class:`~bigchaindb.Bigchain`): An instantiated Bigchain
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object.
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Returns:
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:class:`~.Block`: If valid, return a `Block` object. Else an
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appropriate exception describing the reason of invalidity is
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raised.
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Raises:
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OperationError: If a non-federation node signed the Block.
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InvalidSignature: If a Block's signature is invalid.
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"""
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# First, make sure this node hasn't already voted on this block
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if bigchain.has_previous_vote(self.id, self.voters):
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return self
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# Check if the block was created by a federation node
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possible_voters = (bigchain.nodes_except_me + [bigchain.me])
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if self.node_pubkey not in possible_voters:
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raise OperationError('Only federation nodes can create blocks')
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if not self.is_signature_valid():
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raise InvalidSignature('Block signature invalid')
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# Finally: Tentative assumption that every blockchain will want to
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# validate all transactions in each block
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for tx in self.transactions:
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# NOTE: If a transaction is not valid, `is_valid` will throw an
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# an exception and block validation will be canceled.
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bigchain.validate_transaction(tx)
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return self
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def sign(self, private_key):
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"""Create a signature for the Block and overwrite `self.signature`.
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Args:
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private_key (str): A private key corresponding to
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`self.node_pubkey`.
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Returns:
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:class:`~.Block`
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"""
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block_body = self.to_dict()
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block_serialized = serialize(block_body['block'])
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private_key = PrivateKey(private_key)
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self.signature = private_key.sign(block_serialized.encode()).decode()
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return self
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def is_signature_valid(self):
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"""Check the validity of a Block's signature.
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Returns:
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bool: Stating the validity of the Block's signature.
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"""
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block = self.to_dict()['block']
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# cc only accepts bytestring messages
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block_serialized = serialize(block).encode()
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public_key = PublicKey(block['node_pubkey'])
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try:
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# NOTE: CC throws a `ValueError` on some wrong signatures
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# https://github.com/bigchaindb/cryptoconditions/issues/27
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return public_key.verify(block_serialized, self.signature)
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except (ValueError, AttributeError):
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return False
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@classmethod
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def from_dict(cls, block_body):
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"""Transform a Python dictionary to a Block object.
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Args:
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block_body (dict): A block dictionary to be transformed.
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Returns:
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:class:`~Block`
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Raises:
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InvalidHash: If the block's id is not corresponding to its
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data.
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InvalidSignature: If the block's signature is not corresponding
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to it's data or `node_pubkey`.
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"""
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# TODO: Reuse `is_signature_valid` method here.
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block = block_body['block']
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block_serialized = serialize(block)
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block_id = hash_data(block_serialized)
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public_key = PublicKey(block['node_pubkey'])
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try:
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signature = block_body['signature']
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except KeyError:
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signature = None
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if block_id != block_body['id']:
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raise InvalidHash()
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if signature is not None:
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# NOTE: CC throws a `ValueError` on some wrong signatures
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# https://github.com/bigchaindb/cryptoconditions/issues/27
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try:
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signature_valid = public_key\
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.verify(block_serialized.encode(), signature)
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except ValueError:
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signature_valid = False
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if signature_valid is False:
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raise InvalidSignature('Invalid block signature')
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transactions = [Transaction.from_dict(tx) for tx
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in block['transactions']]
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return cls(transactions, block['node_pubkey'],
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block['timestamp'], block['voters'], signature)
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@property
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def id(self):
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return self.to_dict()['id']
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def to_dict(self):
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"""Transform the Block to a Python dictionary.
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Returns:
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dict: The Block as a dict.
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Raises:
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OperationError: If the Block doesn't contain any transactions.
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"""
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if len(self.transactions) == 0:
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raise OperationError('Empty block creation is not allowed')
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block = {
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'timestamp': self.timestamp,
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'transactions': [tx.to_dict() for tx in self.transactions],
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'node_pubkey': self.node_pubkey,
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'voters': self.voters,
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}
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block_serialized = serialize(block)
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block_id = hash_data(block_serialized)
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return {
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'id': block_id,
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'block': block,
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'signature': self.signature,
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}
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def to_str(self):
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return serialize(self.to_dict())
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