forked from DecentralizedClimateFoundation/DCIPs
105 lines
4.9 KiB
Markdown
105 lines
4.9 KiB
Markdown
---
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eip: 5216
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title: EIP-1155 Approval By Amount Extension
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description: Extension for EIP-1155 secure approvals
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author: Iván Mañús (@ivanmmurciaua), Juan Carlos Cantó (@EscuelaCryptoES)
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discussions-to: https://ethereum-magicians.org/t/eip-erc1155-approval-by-amount/9898
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status: Last Call
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last-call-deadline: 2022-11-12
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type: Standards Track
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category: ERC
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created: 2022-07-11
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requires: 20, 165, 1155
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---
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## Abstract
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This EIP defines standard functions for granular approval of [EIP-1155](./eip-1155.md) tokens by both `id` and `amount`. This EIP extends [EIP-1155](./eip-1155.md).
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## Motivation
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[EIP-1155](./eip-1155.md)'s popularity means that multi-token management transactions occur on a daily basis. Although it can be used as a more comprehensive alternative to [EIP-721](./eip-721.md), EIP-1155 is most commonly used as intended: creating multiple `id`s, each with multiple tokens. While many projects interface with these semi-fungible tokens, by far the most common interactions are with NFT marketplaces.
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Due to the nature of the blockchain, programming errors or malicious operators can cause permanent loss of funds. It is therefore essential that transactions are as trustless as possible. EIP-1155 uses the `setApprovalForAll` function, which approves ALL tokens with a specific `id`. This system has obvious minimum required trust flaws. This EIP combines ideas from [EIP-20](./eip-20.md) and [EIP-721](./eip-721.md) in order to create a trust mechanism where an owner can allow a third party, such as a marketplace, to approve a limited (instead of unlimited) number of tokens of one `id`.
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## Specification
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The keywords “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.
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Contracts using this EIP MUST implement the `IERC1155ApprovalByAmount` interface.
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### Interface implementation
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```solidity
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/**
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* @title ERC-1155 Approval By Amount Extension
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* Note: the ERC-165 identifier for this interface is 0x1be07d74
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*/
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interface IERC1155ApprovalByAmount is IERC1155 {
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/**
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* @notice Emitted when `account` grants or revokes permission to `operator` to transfer their tokens, according to
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* `id` and with an amount: `amount`.
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*/
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event ApprovalByAmount(address indexed account, address indexed operator, uint256 id, uint256 amount);
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/**
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* @notice Grants permission to `operator` to transfer the caller's tokens, according to `id`, and an amount: `amount`.
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* Emits an {ApprovalByAmount} event.
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*
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* Requirements:
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* - `operator` cannot be the caller.
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*/
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function approve(address operator, uint256 id, uint256 amount) external;
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/**
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* @notice Returns the amount allocated to `operator` approved to transfer `account`'s tokens, according to `id`.
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*/
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function allowance(address account, address operator, uint256 id) external view returns (uint256);
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}
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```
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The `approve(address operator, uint256 id, uint256 amount)` function MUST be either `public` or `external`.
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The `allowance(address account, address operator, uint256 id)` function MUST be either `public` or `external` and MUST be `view`.
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The `safeTrasferFrom` function (as defined by EIP-1155) MUST:
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- Not revert if the user has approved `msg.sender` with a sufficient `amount`
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- Subtract the transferred amount of tokens from the approved amount if `msg.sender` is not approved with `setApprovalForAll`
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In addition, the `safeBatchTransferFrom` MUST:
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- Add an extra condition that checks if the `allowance` of all `ids` have the approved `amounts` (See `_checkApprovalForBatch` function reference implementation)
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The `ApprovalByAmount` event MUST be emitted when a certain number of tokens are approved.
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The `supportsInterface` method MUST return `true` when called with `0x1be07d74`.
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## Rationale
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The name "EIP-1155 Approval By Amount Extension" was chosen because it is a succinct description of this EIP. Users can approve their tokens by `id` and `amount` to `operator`s.
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By having a way to approve and revoke in a manner similar to [EIP-20](./eip-20.md), the trust level can be more directly managed by users:
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- Using the `approve` function, users can approve an operator to spend an `amount` of tokens for each `id`.
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- Using the `allowance` function, users can see the approval that an operator has for each `id`.
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The [EIP-20](./eip-20.md) name patterns were used due to similarities with [EIP-20](./eip-20.md) approvals.
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## Backwards Compatibility
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This standard is compatible with [EIP-1155](./eip-1155.md).
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## Reference Implementation
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The reference implementation can be found [here](../assets/eip-5216/ERC1155ApprovalByAmount.sol).
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## Security Considerations
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Users of this EIP must thoroughly consider the amount of tokens they give permission to `operators`, and should revoke unused authorizations.
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## Copyright
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Copyright and related rights waived via [CC0](../LICENSE.md).
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