113 lines
7.0 KiB
Markdown
113 lines
7.0 KiB
Markdown
---
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eip: 6189
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title: Alias Contracts
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description: Allows the creation of contracts that forward calls to other contracts
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author: Gavin John (@Pandapip1)
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discussions-to: https://ethereum-magicians.org/t/eip-6190-functional-selfdestruct/12232
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status: Review
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type: Standards Track
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category: Core
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created: 2022-12-20
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requires: 2929, 6188
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---
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## Abstract
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This EIP allows contracts to be turned into "alias contracts" using a magic nonce. Alias contracts automatically forward calls to other contracts.
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## Motivation
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This EIP is not terribly useful on its own, as it adds additional computation and gas costs without any useful side effects. However, in conjunction with [EIP-6190](./eip-6190.md), it can be used to make SELFDESTRUCT compatible with Verkle trees.
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## Specification
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The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in this document are to be interpreted as described in RFC 2119 and RFC 8174.
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### Definitions
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A contract is an alias contract if its nonce is `2^64-1`, and its contract code is equal to `0x1`.
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### Prerequisites
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[EIP-6188](./eip-6188.md) MUST be used to protect the magic nonce value of `2^64-1`.
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### Opcode Changes
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#### `CALL`, `CALLCODE`, `DELEGATECALL`, `STATICCALL`, `PAY`, and EOA Transactions
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The "callee" refers to the account that is being called or being paid.
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If the nonce of the callee is `2^64-1`, the call MUST be forwarded to the address stored in the `0`th storage slot of the callee (as if the callee was the address stored in the `0`th storage slot of the callee). This MUST repeat until a non-alias contract is reached. The `CALLER` MUST remain unchanged.
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If there is more than one alias contract in the chain, the original callee and all subsequent callees (except the last one) MUST have their `0`th storage slot set to the address of the final non-alias contract. Then, the call MUST be forwarded as usual. **This MUST occur, even in a read-only context like `STATICCALL`.**
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For example, if `A` is an alias contract that forwards calls to `B`, which is an alias contract that forwards calls to `C`, then `A`'s `0`th storage slot is set to `C`'s address. Then, the call is forwarded to `C`.
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Finally, the opcode MUST proceed as usual, using the final non-alias contract.
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The `CALL`, `CALLCODE`, `DELEGATECALL`, and `STATICCALL` opcodes and EOA Transactions MUST cost an `25` gas per account accessed in this manner (including the final one, and including if no aliased accounts were used), in addition to all the regular costs incurred by accessing accounts (see [EIP-2929](./eip-2929.md)). For every account whose `0`th storage slot is updated, those opcodes MUST also cost an additional `5000` gas.
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If an infinite loop occurs, the transaction MUST run out of gas and revert.
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#### `EXTCODEHASH`, `EXTCODECOPY`, `EXTCODESIZE`, and `BALANCE`
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The "accessed account" refers to the account that is being accessed (i.e. the account whose code is being accessed, or the account whose balance is being accessed).
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Similar to the `CALL` family of opcodes, if the nonce of the accessed account is `2^64-1`, the accessed account's address MUST be replaced with the address stored in the `0`th storage slot of the accessed account. This MUST repeat until a non-alias contract is reached.
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If there is more than one alias contract in the chain, the original accessed account and all subsequent accessed accounts (except the last one) MUST have their `0`th storage slot set to the address of the final non-alias contract. Then, the accessed account MUST be replaced as usual. **This MUST occur, even in a read-only context like `STATICCALL`.**
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Finally, the opcode MUST proceed as usual, using the final non-alias contract.
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The `EXTCODEHASH`, `EXTCODECOPY`, `EXTCODESIZE`, and `BALANCE` opcodes MUST cost an `25` gas per account accessed in this manner (including the final one, and including if no aliased accounts were used), in addition to all the regular costs incurred by accessing accounts (see [EIP-2929](./eip-2929.md)). For every account whose `0`th storage slot is updated, those opcodes MUST also cost an additional `5000` gas.
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If an infinite loop occurs, the transaction MUST run out of gas and revert.
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#### `CREATE` and `CREATE2`
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If `CREATE` or `CREATE2` would create (or fail to create, depending on which EIPs are used) an account at an address, and that account's code is `0x1`, and its nonce is `2^64-1`, then instead of reverting, an attempt MUST be made to create a contract at the address stored in the `0`th storage slot of the existing account. This MUST repeat until a non-alias contract is reached.
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If there is more than one alias contract in the chain, the original accessed account and all subsequent accessed accounts (except the last one) MUST have their `0`th storage slot set to the address of the final non-alias contract.
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Finally, the opcode MUST proceed as usual, returning the address of the newly-created contract.
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The `CREATE` and `CREATE2` opcodes MUST cost an `25` gas per account accessed in this manner (including the final one, and including if no aliased accounts were used), in addition to all the regular costs incurred by accessing accounts (see [EIP-2929](./eip-2929.md)). For every account whose `0`th storage slot is updated, those opcodes must also cost an additional `5000` gas.
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If an infinite loop occurs, the transaction runs out of gas and reverts.
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#### `ADDRESS`
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This opcode remains unchanged; `ADDRESS` points to the address that doesn't have a nonce of `2^64-1`.33
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### Transfers to the zero address
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Transfers to the zero address continue to have the same effect as the `CREATE` opcode, and will cost extra gas as discussed in the [`CREATE` and `CREATE2`](#create-and-create2) section.
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### RPC Endpoint Changes
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#### `eth_getStorageAt`
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The `eth_getStorageAt` RPC endpoint must error if the target contract has a contract code of `0x1` and a nonce of `2^64-1`.
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## Rationale
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The additional gas cost of `25` represents the cost of fetching the nonce and comparing it to the given value.
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`eth_getStorageAt` was modified to throw an error because of alias contracts' special behavior.
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The nonce of `2^64-1` was chosen since it is the nonce protected by [EIP-6188](./eip-6188.md).
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The contract code of `0x1` was chosen arbitrarily. A nonzero code was chosen just in case a non-alias contract with nonce `2^64-1` somehow had its code set to `0x0`, or an EOA had its nonce set to `2^64-1`.
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## Backwards Compatibility
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This EIP requires a protocol upgrade, since it modifies consensus rules. No existing contracts should be affected, as they will not have a nonce of `2^64-1`, nor will they have the contract code `0x1`.
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## Security Considerations
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The additional gas costs may cause potential DoS attacks if they access an arbitrary contract's data or make frequent contract deactivations. Contract authors must be aware and design contracts accordingly. There may be an effect on existing deployed code performing autonomous destruction and revival.
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## Copyright
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Copyright and related rights waived via [CC0](../LICENSE.md).
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