def get_spent(self, tx_input):
"""Check if a `txid` was already used as an input.
A transaction can be used as an input for another transaction. Bigchain needs to make sure that a
given `txid` is only used once.
Args:
tx_input (dict): Input of a transaction in the form `{'txid': 'transaction id', 'cid': 'condition id'}`
Returns:
The transaction that used the `txid` as an input if it exists else it returns `None`
"""
# checks if an input was already spent
# checks if the bigchain has any transaction with input {'txid': ..., 'cid': ...}
response = r.table('bigchain').concat_map(lambda doc: doc['block']['transactions'])\
.filter(lambda transaction: transaction['transaction']['fulfillments']
.contains(lambda fulfillment: fulfillment['input'] == tx_input))\
.run(self.conn)
# a transaction_id should have been spent at most one time
transactions = list(response)
if transactions:
if len(transactions) != 1:
raise exceptions.DoubleSpend('`{}` was spent more then once. There is a problem with the chain'.format(
tx_input['txid']))
else:
return transactions[0]
else:
return None
def validate_transaction(self, transaction):
"""Validate a transaction.
Args:
transaction (dict): transaction to validate.
Returns:
The transaction if the transaction is valid else it raises and 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 the operation is CREATE the transaction should have no inputs and should be signed by a
# federation node
if transaction['transaction']['operation'] == 'CREATE':
if transaction['transaction']['input']:
raise ValueError('A CREATE operation has no inputs')
if not (set(transaction['transaction']['current_owners']) <=
set(self.federation_nodes + [self.me])):
raise exceptions.OperationError(
'Only federation nodes can use the operation `CREATE`')
else:
# check if the input exists, is owned by the current_owner
if not transaction['transaction']['input']:
raise ValueError(
'Only `CREATE` transactions can have null inputs')
tx_input = self.get_transaction(
transaction['transaction']['input'])
if not tx_input:
raise exceptions.TransactionDoesNotExist(
'input `{}` does not exist in the bigchain'.format(
transaction['transaction']['input']))
if tx_input['transaction']['new_owners'] != transaction[
'transaction']['current_owners']:
raise exceptions.TransactionOwnerError(
'current_owner `{}` does not own the input `{}`'.format(
transaction['transaction']['current_owners'],
transaction['transaction']['input']))
# check if the input was already spent by a transaction other then this one.
spent = self.get_spent(tx_input['id'])
if spent:
if spent['id'] != transaction['id']:
raise exceptions.DoubleSpend(
'input `{}` was already spent'.format(
transaction['transaction']['input']))
util.check_hash_and_signature(transaction)
return transaction
def get_spent(self, tx_input):
"""Check if a `txid` was already used as an input.
A transaction can be used as an input for another transaction. Bigchain needs to make sure that a
given `txid` is only used once.
Args:
tx_input (dict): Input of a transaction in the form `{'txid': 'transaction id', 'cid': 'condition id'}`
Returns:
The transaction that used the `txid` as an input if it exists else it returns `None`
"""
# checks if an input was already spent
# checks if the bigchain has any transaction with input {'txid': ..., 'cid': ...}
response = r.table('bigchain', read_mode=self.read_mode)\
.concat_map(lambda doc: doc['block']['transactions'])\
.filter(lambda transaction: transaction['transaction']['fulfillments']
.contains(lambda fulfillment: fulfillment['input'] == tx_input))\
.run(self.conn)
transactions = list(response)
# a transaction_id should have been spent at most one time
if transactions:
# determine if these valid transactions appear in more than one valid block
num_valid_transactions = 0
for transaction in transactions:
# ignore invalid blocks
if self.get_transaction(transaction['id']):
num_valid_transactions += 1
if num_valid_transactions > 1:
raise exceptions.DoubleSpend(
'`{}` was spent more then once. There is a problem with the chain'
.format(tx_input['txid']))
if num_valid_transactions:
return transactions[0]
else:
# all queried transactions were invalid
return None
else:
return None
def validate_transaction(bigchain, transaction):
"""Validate a transaction.
Args:
bigchain (Bigchain): an instantiated bigchaindb.Bigchain object.
transaction (dict): transaction to validate.
Returns:
The 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 the operation is CREATE the transaction should have no inputs and
# should be signed by a federation node
if transaction['transaction']['operation'] == 'CREATE':
if transaction['transaction']['input']:
raise ValueError('A CREATE operation has no inputs')
if transaction['transaction']['current_owner'] not in (
bigchain.federation_nodes + [bigchain.me]):
raise exceptions.OperationError(
'Only federation nodes can use the operation `CREATE`')
else:
# check if the input exists, is owned by the current_owner
if not transaction['transaction']['input']:
raise ValueError(
'Only `CREATE` transactions can have null inputs')
tx_input = bigchain.get_transaction(
transaction['transaction']['input'])
if not tx_input:
raise exceptions.TransactionDoesNotExist(
'input `{}` does not exist in the bigchain'.format(
transaction['transaction']['input']))
if (tx_input['transaction']['new_owner'] !=
transaction['transaction']['current_owner']):
raise exceptions.TransactionOwnerError(
'current_owner `{}` does not own the input `{}`'.format(
transaction['transaction']['current_owner'],
transaction['transaction']['input']))
# check if the input was already spent by a transaction other than
# this one.
spent = bigchain.get_spent(tx_input['id'])
if spent and spent['id'] != transaction['id']:
raise exceptions.DoubleSpend(
'input `{}` was already spent'.format(
transaction['transaction']['input']))
# Check hash of the transaction
calculated_hash = crypto.hash_data(
util.serialize(transaction['transaction']))
if calculated_hash != transaction['id']:
raise exceptions.InvalidHash()
# Check signature
if not util.verify_signature(transaction):
raise exceptions.InvalidSignature()
return transaction
def validate_transaction(bigchain, transaction):
"""Validate a transaction.
Args:
bigchain (Bigchain): an instantiated bigchaindb.Bigchain object.
transaction (dict): transaction to validate.
Returns:
The 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 the operation is CREATE the transaction should have no inputs and
# should be signed by a federation node
if transaction['transaction']['operation'] == 'CREATE':
# TODO: for now lets assume a CREATE transaction only has one fulfillment
if transaction['transaction']['fulfillments'][0]['input']:
raise ValueError('A CREATE operation has no inputs')
# TODO: for now lets assume a CREATE transaction only has one current_owner
if transaction['transaction']['fulfillments'][0]['current_owners'][
0] not in (bigchain.nodes_except_me + [bigchain.me]):
raise exceptions.OperationError(
'Only federation nodes can use the operation `CREATE`')
else:
# check if the input exists, is owned by the current_owner
if not transaction['transaction']['fulfillments']:
raise ValueError('Transaction contains no fulfillments')
# check inputs
for fulfillment in transaction['transaction']['fulfillments']:
if not fulfillment['input']:
raise ValueError(
'Only `CREATE` transactions can have null inputs')
tx_input = bigchain.get_transaction(
fulfillment['input']['txid'])
if not tx_input:
raise exceptions.TransactionDoesNotExist(
'input `{}` does not exist in the bigchain'.format(
fulfillment['input']['txid']))
# TODO: check if current owners own tx_input (maybe checked by InvalidSignature)
# check if the input was already spent by a transaction other than
# this one.
spent = bigchain.get_spent(fulfillment['input'])
if spent and spent['id'] != transaction['id']:
raise exceptions.DoubleSpend(
'input `{}` was already spent'.format(
fulfillment['input']))
# Check hash of the transaction
calculated_hash = util.get_hash_data(transaction)
if calculated_hash != transaction['id']:
raise exceptions.InvalidHash()
# Check fulfillments
if not util.validate_fulfillments(transaction):
raise exceptions.InvalidSignature()
return transaction