def from_dict(cls, block_body):
block = block_body['block']
block_serialized = serialize(block)
block_id = hash_data(block_serialized)
verifying_key = VerifyingKey(block['node_pubkey'])
try:
signature = block_body['signature']
except KeyError:
signature = None
if block_id != block_body['id']:
raise InvalidHash()
if signature is not None:
# NOTE: CC throws a `ValueError` on some wrong signatures
# https://github.com/bigchaindb/cryptoconditions/issues/27
try:
signature_valid = verifying_key.verify(block_serialized,
signature)
except ValueError:
signature_valid = False
if signature_valid is False:
raise InvalidSignature('Invalid block signature')
transactions = [Transaction.from_dict(tx) for tx
in block['transactions']]
return cls(transactions, block['node_pubkey'],
block['timestamp'], block['voters'], signature)
def validate(self, bigchain):
"""Validate a block.
Args:
bigchain (Bigchain): an instantiated bigchaindb.Bigchain object.
Returns:
block (Block): The block as a `Block` object if it is valid.
Else it raises an appropriate exception describing
the reason of invalidity.
Raises:
OperationError: if a non-federation node signed the block.
"""
# First, make sure this node hasn't already voted on this block
if bigchain.has_previous_vote(self.id, self.voters):
return self
# Check if the block was created by a federation node
possible_voters = (bigchain.nodes_except_me + [bigchain.me])
if self.node_pubkey not in possible_voters:
raise OperationError('Only federation nodes can create blocks')
if not self.is_signature_valid():
raise InvalidSignature('Block signature invalid')
# Finally: Tentative assumption that every blockchain will want to
# validate all transactions in each block
for tx in self.transactions:
# NOTE: If a transaction is not valid, `is_valid` will throw an
# an exception and block validation will be canceled.
bigchain.validate_transaction(tx)
return self
def validate(self, bigchain):
"""Validate a transaction.
Args:
bigchain (Bigchain): an instantiated bigchaindb.Bigchain object.
Returns:
The transaction (Transaction) if the transaction is valid else it
raises an exception describing the reason why the transaction is
invalid.
Raises:
OperationError: if the transaction operation is not supported
TransactionDoesNotExist: if the input of the transaction is not
found
TransactionOwnerError: if the new transaction is using an input it
doesn't own
DoubleSpend: if the transaction is a double spend
InvalidHash: if the hash of the transaction is wrong
InvalidSignature: if the signature of the transaction is wrong
"""
if len(self.fulfillments) == 0:
raise ValueError('Transaction contains no fulfillments')
input_conditions = []
inputs_defined = all([ffill.tx_input for ffill in self.fulfillments])
if self.operation in (Transaction.CREATE, Transaction.GENESIS):
if inputs_defined:
raise ValueError('A CREATE operation has no inputs')
elif self.operation == Transaction.TRANSFER:
if not inputs_defined:
raise ValueError('Only `CREATE` transactions can have null '
'inputs')
for ffill in self.fulfillments:
input_txid = ffill.tx_input.txid
input_cid = ffill.tx_input.cid
input_tx = bigchain.get_transaction(input_txid)
if input_tx is None:
raise TransactionDoesNotExist("input `{}` doesn't exist"
.format(input_txid))
spent = bigchain.get_spent(input_txid, ffill.tx_input.cid)
if spent and spent.id != self.id:
raise DoubleSpend('input `{}` was already spent'
.format(input_txid))
input_conditions.append(input_tx.conditions[input_cid])
else:
allowed_operations = ', '.join(Transaction.ALLOWED_OPERATIONS)
raise TypeError('`operation`: `{}` must be either {}.'
.format(self.operation, allowed_operations))
if not self.fulfillments_valid(input_conditions):
raise InvalidSignature()
else:
return self
def validate(self, bigchain):
"""Validate a transaction.
Args:
bigchain (Bigchain): an instantiated bigchaindb.Bigchain object.
Returns:
The transaction (Transaction) if the transaction is valid else it
raises an exception describing the reason why the transaction is
invalid.
Raises:
OperationError: if the transaction operation is not supported
TransactionDoesNotExist: if the input of the transaction is not
found
TransactionOwnerError: if the new transaction is using an input it
doesn't own
DoubleSpend: if the transaction is a double spend
InvalidHash: if the hash of the transaction is wrong
InvalidSignature: if the signature of the transaction is wrong
"""
if len(self.fulfillments) == 0:
raise ValueError('Transaction contains no fulfillments')
input_conditions = []
inputs_defined = all([ffill.tx_input for ffill in self.fulfillments])
if self.operation in (Transaction.CREATE, Transaction.GENESIS):
# validate inputs
if inputs_defined:
raise ValueError('A CREATE operation has no inputs')
# validate asset
self.asset._validate_asset()
elif self.operation == Transaction.TRANSFER:
if not inputs_defined:
raise ValueError('Only `CREATE` transactions can have null '
'inputs')
# check inputs
# store the inputs so that we can check if the asset ids match
input_txs = []
for ffill in self.fulfillments:
input_txid = ffill.tx_input.txid
input_cid = ffill.tx_input.cid
input_tx, status = bigchain.\
get_transaction(input_txid, include_status=True)
if input_tx is None:
raise TransactionDoesNotExist(
"input `{}` doesn't exist".format(input_txid))
if status != bigchain.TX_VALID:
raise FulfillmentNotInValidBlock(
'input `{}` does not exist in a valid block'.format(
input_txid))
spent = bigchain.get_spent(input_txid, ffill.tx_input.cid)
if spent and spent.id != self.id:
raise DoubleSpend(
'input `{}` was already spent'.format(input_txid))
input_conditions.append(input_tx.conditions[input_cid])
input_txs.append(input_tx)
# validate asset id
asset_id = Asset.get_asset_id(input_txs)
if asset_id != self.asset.data_id:
raise AssetIdMismatch(
'The asset id of the input does not match the asset id of the transaction'
)
else:
allowed_operations = ', '.join(Transaction.ALLOWED_OPERATIONS)
raise TypeError('`operation`: `{}` must be either {}.'.format(
self.operation, allowed_operations))
if not self.fulfillments_valid(input_conditions):
raise InvalidSignature()
else:
return self