Skip to main content

Permissioned Auto EVM

A "permissioned" Auto EVM instance uses an allow list to limit which users can create contracts. After contract deployment, any user can call existing contracts.

Core Functionality​

The pallet filters contract creation calls based on an Ethereum account ID allow list:

  • pallet-ethereum calls are filtered by the signer of the self-contained call. This includes Legacy, EIP1559, and EIP2930 transactions.
  • pallet-evm calls are filtered by the signer of the runtime call, which is typically the domain owner. This includes create and create2 calls. If unsigned contract creation calls are permitted by other runtime settings, they are only allowed if the allow list is set to Anyone. The source field inside the transaction is ignored.

Contract calls nested within pallet-utility calls are allowed or rejected accurately, regardless of their nesting depth. (Nested transactions use some temporary memory, but don't use stack-based recursion.)

Rejected transactions have a custom error code ERR_CONTRACT_CREATION_NOT_ALLOWED.

Contract creation calls nested within pallet-domain-sudo calls are rejected because they are not inherents.

Pallets​

The Permissioned Auto EVM functionality is implemented via two runtime pallets:

  • EVMNoncetracker: A custom pallet used to track EVM nonces, and the EVM contract creation allow list. The crate is called pallet-evm-tracker, but existing runtimes keep the EVMNoncetracker name to preserve their storage names.
  • Domains: The send_evm_domain_set_contract_creation_allowed_by_call in pallet-domains can be used by sudo or the domain owner to change the allow list on Permissioned EVMs.

pallet-evm-tracker depends on some upstream pallets:

  • Ethereum: Ethereum-compatible transactions.
  • EVM: An EVM hosted on Substrate, using a Substrate-specific transaction format.

Global Parameters​

None

Runtime Instance Parameters​

The DomainConfig can be used to configure the initial contract creation allow list. The relevant parameter is:

DomainConfig

  • domain_runtime_config: configurations that are specific to each domain type:
    • Evm:
      • Public: a public EVM where the contract creation allow list can't be changed (even by the domain owner or sudo)
      • Private { initial_contract_creation_allow_list }: A Permissioned EVM, with the accounts that are initially allowed to create contracts on this EVM domain. (It is called "Private" for backwards compatibility.)

The default configuration is Public.

Pallet Calls​

pallet-domains​

send_evm_domain_set_contract_creation_allowed_by_call​

send_evm_domain_set_contract_creation_allowed_by_call(domain_id, contract_creation_allowed_by)

The sudo account or domain owner can replace the current contract creation allow list with a new list. This list applies to future contract creation transactions.

Existing contracts remain deployed, even if they were created by accounts that are no longer in the allow list.

pallet-evm-tracker​

set_contract_creation_allowed_by​

set_contract_creation_allowed_by(contract_creation_allowed_by)

The send_evm_domain_set_contract_creation_allowed_by_call is turned into an inherent, which updates the pallet storage via this call.

Pallet Storage Items​

pallet-domains​

DomainRegistry​

Used to check if the domain is a Permissioned EVM, before accepting the send_evm_domain_set_contract_creation_allowed_by_call.

Also holds the initial_contract_creation_allow_list, which is applied to Permissioned EVM domain storage at domain instantiation.

EvmDomainContractCreationAllowedByCalls​

Temporary storage for the send_evm_domain_set_contract_creation_allowed_by_call in this block, if there is one.

pallet-evm-tracker​

AccountNonce​

AccountNonce is used to track Ethereum account nonces. (It is not used in implementing Permissioned EVMs.)

ContractCreationAllowedBy​

ContractCreationAllowedBy is a list of accounts that are allowed to create contracts.

It has two variants:

  • Anyone: any account can create signed contracts, and unsigned contract creation is allowed.
  • Accounts(list): a list of Ethereum Account IDs that can create contracts. If the list is empty, all contract creation transactions are rejected.