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Add EIP: Withdrawal Credential Update Request
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| --- | ||
| eip: 7804 | ||
| title: Withdrawal Credential Update Request | ||
| description: Allow validators to update their withdrawal credentials via execution requests | ||
| author: Lucas Saldanha (@lucassaldanha), Mikhail Kalinin (@mkalinin) | ||
| discussions-to: https://ethereum-magicians.org/t/eip-7804-withdrawal-credential-update-request/21514 | ||
| status: Draft | ||
| type: Standards Track | ||
| category: Core | ||
| created: 2024-10-31 | ||
| --- | ||
|
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| ## Abstract | ||
|
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| This proposal defines a mechanism to allow validators to update their withdrawal | ||
| credentials using a new execution request type (0x03). The request allows for | ||
| changing the execution address and the withdrawal credential prefix (0x01 or 0x02). | ||
|
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| ## Motivation | ||
|
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| When the ability to update a validator BLS withdrawal credentials to execution | ||
| address was introduced in Capella, one of the most common questions was about | ||
| allowing the withdrawal credential to be changed in the future. | ||
| Either for security (e.g. credential rotation) or to allow for alternative ways | ||
| of handling withdrawals (e.g. having a contract address as credentials). | ||
| The main reason for not adding this options was because implementing | ||
| this communication channel between the Execution Layer and the Consensus Layer is | ||
| complex (based on the experience with the Eth1 bridge). | ||
|
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| In Electra, the protocol was upgraded with Execution Requests (deposits, withdrawals and | ||
| consolidations), and a mechanism for general purpose execution requests | ||
| [EIP-7685](./eip-7685.md), decreasing the complexity of adding | ||
| a new request from execution to consensus layer. | ||
|
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| The introduction of execution requests that are created on the execution layer, | ||
| opened up possibilities on how validators can be managed. | ||
| Execution request can be created via smart contracts, allowing for decentralized | ||
| and on-chain mechanisms to be explored. | ||
| This also means validators will be able to move between execution and compounding | ||
| withdrawal credentials (follwoing the correct churn on the total staked amount). | ||
|
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| For an execution request to be authorized in the consensus layer, the withdrawal | ||
| credential of the validator must be the same of the `msg.caller` when processing | ||
| the transaction on the EVM. | ||
| So the validator's withdrawal credential must be the same address of the smart contract | ||
| creating the request (not the credential of the transaction sender), or the contract | ||
| needs to use `DELEGATECALL` to ensure the caller address matches the address in the | ||
| validator's withdrawal credential. | ||
| Validators that already have a contract address as their withdrawal credentials should | ||
| be able to update their contracts to meet this demand (assuming they have an | ||
| updatable contract). | ||
|
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| There problems for existing validators that have their withdrawal credentials | ||
| set to an EOA account is they will never be able to use use smart contracts | ||
| for creating execution requests, because the current design does not allow for these | ||
| credentials to ever be changed. | ||
|
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| Allowing for validators to update their withdrawal credentials mean they can opt-in | ||
| and out of different schemes and strategies on managing their validators, favouring | ||
| experimentation and innovation. | ||
| Today, the only alternative to this is exitting the validator and creating a new | ||
| validator with different withdrawal credentials. | ||
|
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| ## Specification | ||
|
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| ### Constants | ||
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| | Name | Value | Comment | | ||
| | - | - | - | | ||
| |`FORK_TIMESTAMP` | *TBD* | Mainnet | | ||
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| ### Configuration | ||
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| | Name | Value | Comment | | ||
| | - | - | - | | ||
| | `WITHDRAWAL_CREDENTIALS_UPDATE_REQUEST_PREDEPLOY_ADDRESS` | `0x09Fc772D0857550724b07B850a4323f39112aAaA` | Where to call and store relevant details about the withdrawal credentials update mechanism | | ||
| | `WITHDRAWAL_CREDENTIALS_UPDATE_REQUEST_TYPE` | `0x03` | The [EIP-7685](./eip-7685.md) type prefix for withdrawal credential update request | | ||
| | `SYSTEM_ADDRESS` | `0xfffffffffffffffffffffffffffffffffffffffe` | Address used to invoke system operation on contract | ||
| | `EXCESS_WITHDRAWAL_CREDENTIALS_UPDATE_REQUESTS_STORAGE_SLOT` | 0 | | | ||
| | `WITHDRAWAL_CREDENTIALS_UPDATE_REQUEST_COUNT_STORAGE_SLOT` | 1 | | | ||
| | `WITHDRAWAL_CREDENTIALS_UPDATE_REQUEST_QUEUE_HEAD_STORAGE_SLOT` | 2 | Pointer to head of the withdrawal credential update request message queue | | ||
| | `WITHDRAWAL_CREDENTIALS_UPDATE_REQUEST_QUEUE_TAIL_STORAGE_SLOT` | 3 | Pointer to the tail of the withdrawal credential update request message queue| | ||
| | `WITHDRAWAL_CREDENTIALS_UPDATE_REQUEST_QUEUE_STORAGE_OFFSET` | 4 | The start memory slot of the in-state withdrawal credential update request message queue| | ||
| | `MAX_WITHDRAWAL_CREDENTIALS_UPDATE_REQUESTS_PER_BLOCK` | 4 | Maximum number of withdrawal credential update requests that can be dequeued into a block | | ||
| | `TARGET_WITHDRAWAL_CREDENTIALS_UPDATE_REQUESTS_PER_BLOCK` | 1 | | | ||
| | `MIN_WITHDRAWAL_CREDENTIALS_UPDATE_REQUEST_FEE` | 1 | | | ||
| | `WITHDRAWAL_CREDENTIALS_UPDATE_REQUEST_FEE_UPDATE_FRACTION` | 17 | | | ||
| | `EXCESS_INHIBITOR` | `2**256-1` | Excess value used to compute the fee before the first system call | | ||
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| ### Execution Layer | ||
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| * **`FORK_BLOCK`** -- the first block in a blockchain with the `timestamp` greater or equal to `FORK_TIMESTAMP`. | ||
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| #### Withdrawal Credentials Update request operation | ||
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| The new withdrawal credential update request operation is an [EIP-7685](./eip-7685.md) request | ||
| with type `0x03` and consists of the following fields: | ||
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| 1. `pubkey`: `Bytes48` | ||
| 2. `old_address`: `Bytes20` | ||
| 3. `new_address`: `Bytes20` | ||
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| The [EIP-7685](./eip-7685.md) encoding of a withdrawal credential update request is computed as follows. | ||
|
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| ```python | ||
| request_type = WITHDRAWAL_CREDENTIALS_UPDATE_REQUEST_TYPE | ||
| request_data = read_withdrawal_credential_update_requests() | ||
| ``` | ||
|
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| #### Withdrawal Credentials Update Request Contract | ||
|
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| The contract is similar to other execution requests contracts for Deposits, Withdrawals and Consolidation. | ||
| The contract has three different code paths, which can be summarized at a high level as follows: | ||
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| 1. Add request - requires a `68` byte input, the validator's public key concatenated with the new address for withdrawal credentials. | ||
| 2. Excess requests getter - if the input length is zero, return the current excess requests count. | ||
| 3. System process - if called by system address, pop off the withdrawal credential update requests for the current block from the queue. | ||
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| <!-- TODO add sudo code / bytecode / deployment / etc (very similar to existing request contracts) --> | ||
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| #### Block processing | ||
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| At the end of processing any execution block where `block.timestamp >= FORK_TIMESTAMP` (i.e. after processing all transactions and after performing the block body requests validations) client software **MUST** include a call the contract as `SYSTEM_ADDRESS` and empty input data to trigger the system subroutine execute. The resopnse should be treated as a new request type (0x03) according to [EIP-7685](./eip-7685.md). | ||
|
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| #### Block Validation | ||
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| EL must check that the commitment hash in the execution block header matches the hash of the list of execution requests the CL sends when | ||
| validating the execution block (including any requests of the the new defined type 0x03). | ||
|
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| ### Consensus Layer | ||
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| <!-- TODO complete the specification --> | ||
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| Summary of changes: | ||
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| * New container `WithdrawalCredentialUpdateRequest` | ||
| * New method in Block Processing: `process_withdrawal_credential_update_request` | ||
| * New Beacon State mutator method: `update_withdrawal_credentials` | ||
|
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| ```python | ||
| class WithdrawalCredentialUpdateRequest(Container): | ||
| validator_pubkey: BLSPubkey | ||
| old_address: ExecutionAddress # request contract will set this to msg.caller | ||
| new_address: ExecutionAddress | ||
| ``` | ||
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| ```python | ||
| def process_withdrawal_credential_update_request(state: BeaconState, withdrawal_credentials_update_requests: WithdrawalCredentialUpdateRequest) -> None: | ||
| validator_pubkeys = [v.pubkey for v in state.validators] | ||
| # Verify pubkey exists | ||
| request_pubkey = withdrawal_credentials_update_requests.validator_pubkey | ||
| if request_pubkey not in validator_pubkeys: | ||
| return | ||
| index = ValidatorIndex(validator_pubkeys.index(request_pubkey)) | ||
| validator = state.validators[index] | ||
|
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| # Verify withdrawal credentials | ||
| has_correct_credential = has_execution_withdrawal_credential(validator) | ||
| is_correct_old_address = ( | ||
| validator.withdrawal_credentials[12:] == withdrawal_credentials_update_requests.old_address | ||
| ) | ||
| if not (has_correct_credential and is_correct_old_address): | ||
| return | ||
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| credential_type = withdrawal_credentials_update_requests.type | ||
| is_eth1_type = credential_type == ETH1_ADDRESS_WITHDRAWAL_PREFIX | ||
| is_compounding_type = credential_type == COMPOUNDING_WITHDRAWAL_PREFIX | ||
| # Verify valid type | ||
| if not (is_eth1_type or is_compounding_type): | ||
| return; | ||
|
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| update_withdrawal_credentials(state, index, credential_type, withdrawal_credentials_update_requests.new_address) | ||
| ``` | ||
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| ```python | ||
| def update_withdrawal_credentials(state: BeaconState, index: ValidatorIndex, new_credential_type: Bytes1, new_withdrawal_credentials: ExecutionAddress) -> None: | ||
| old_credential_type = validator.withdrawal_credentials[:1] | ||
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| validator = state.validators[index] | ||
| validator.withdrawal_credentials = ( | ||
| new_credential_type | ||
| + b'\x00' * 11 | ||
| + new_withdrawal_credentials | ||
| ) | ||
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| # If moving from 0x01 to 0x02 | ||
| if (old_credential_type == ETH1_ADDRESS_WITHDRAWAL_PREFIX and new_credential_type == COMPOUNDING_WITHDRAWAL_PREFIX) { | ||
| #TODO: in this case we need to ensure we put them through the churn/likely re-using some of the exiting rules | ||
| switch_to_compounding_validator(state, index) | ||
| } | ||
| ``` | ||
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| ## Rationale | ||
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| <!-- TODO --> | ||
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| ## Backwards Compatibility | ||
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| <!-- TODO --> | ||
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| ## Test Cases | ||
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| <!-- TODO --> | ||
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| ## Security Considerations | ||
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| Ownership is defined based on control of the withdrawal credential account, either as a private key (for EOA accounts) or controlling | ||
| the smart contract at the address set as withdrawal credential. Therefore allowing an update should not bring any security implications. | ||
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| Futher discussion needed. | ||
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| ## Copyright | ||
|
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| Copyright and related rights waived via [CC0](../LICENSE.md). |