Hyperledger Sawtooth includes the ability to control validator and transactor permissions. This article describes permissioning in Hyperledger Sawtooth by providing a detailed list of the requirements, capabilities and user stories that help to understand permissioning design.
Sawtooth divides permissioning into two general groups:
- Transactor key permissioning controls that can submit transactions and batches, based on signing keys, and…
- Validator key permissioning controls, with which nodes are allowed to establish connections to the validator network.
Each requirement has a short description, the network scenario that the requirement supports and associated user stories. User stories are short statements about a requirement or capability that an actor desires. These short descriptions illustrate the need for specific permission requirements. The design of Sawtooth permissioning includes both local validator configuration and network-wide on-chain permissioning.
- Local configuration allows a validator to limit who is allowed to submit batches and transactions directly to that validator. This is useful, for example, if a company is running its own validator, and wishes to allow only members of that company to submit transactions.
- On-chain configuration allows a Sawtooth network to enforce consistent permissioning rules. For example, in validator key permissioning, all the validators on the network will reject the same node from peering, ensuring that only known nodes can join the network.
Validator network scenarios
Sawtooth is designed to support public, consortium and private networks. The following network scenarios are used in the discussion on capability requirements to illustrate when each requirement could be useful.
- Public network: In a public network, all connections are allowed, and all transactors are allowed to sign batches and transactions.
- Consortium network: In a consortium network, only specific validators are allowed to join the validator network and participate in consensus. However, the network allows any client, transaction processor, or event subscriber to connect to a validator, and accept batches and transactions signed by all transactors.
- Private network: In a private network, only specific validators are allowed to join the validator network and participate in a consensus. The validators in the network accept only connections from specific clients. The validators also control whether the client is allowed to submit batches and query specific address prefixes in state. Only specific transaction processors and event subscribers are allowed to connect to the local validator. Batches and transactions that are received by the validator can only be signed by permitted transactors. Transactors can also be restricted to only sending transactions for certain transaction families.
Transactor key permissioning
Transactor key permissioning is performed on the basis of a transactor’s public signing key. This includes both batch signers and transaction signers. When the validator receives a batch from a client, it checks both the local configuration and network configuration. Only the batch signers that are permitted in the intersection of the two configurations will be allowed. When the validator receives a batch from a peer validator, only the network configuration is checked. This behaviour is required to prevent network forks. The following are high level capabilities of transactor key permissioning:
- Allow all batch signers to submit batches, where the validator can be configured to allow all batches to be submitted, regardless of who the batch signer is.
- Allow only specific batch signers to submit batches, where the validator can be configured to only allow certain batch signers to submit batches.
- Allow all transaction signers to submit transactions, where the validator can be configured to allow all transactions to be submitted, regardless of who the transaction signer is.
- Allow only specific transaction signers to submit transactions, where the validator can be configured to only allow certain transaction signers to submit transactions.
- Restrict the type of transactions transactors can sign, where the validator can restrict the transaction signers that are allowed to sign transactions for a specific transaction family.
- Support policy based transactor permissioning, where the validator can enforce transactor permissions based on defined policies.
Validator key permissioning
Validator key permissioning is performed on the basis of a validator node’s public signing key. The following are high level capabilities of validator key permissioning:
- Allow all nodes to join the validator network, whereby the validator network can be configured to allow all validator nodes to join the network. This means that every validator on the network should accept the node as a peer, regardless of its public key.
- Allow only specific nodes to join the validator network, where the validator network can be configured to only allow nodes to join the network if the node’s public key is permitted.
- Allow only specific nodes to participate in consensus, where the validator network can be configured to only allow specific nodes to participate in consensus. This is separate from any restrictions enforced by the consensus algorithm. The nodes that are not allowed to participate in consensus can still validate blocks but are not allowed to publish blocks.
In the next post we will take a closer look at Sawtooth events.
The author is an independent consultant with prior experience in training, and actively studies emerging technologies like blockchain, containerisation, etc. She also has certification for cyber law and cyber forensics.