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Add ERC721 Wrapper (#3863)

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Co-authored-by: Hadrien Croubois <hadrien.croubois@gmail.com>
pull/4039/head
Ernesto García 2 years ago committed by GitHub
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  1. 5
      .changeset/early-oranges-raise.md
  2. 3
      contracts/token/ERC721/README.adoc
  3. 102
      contracts/token/ERC721/extensions/ERC721Wrapper.sol
  4. 2
      docs/modules/ROOT/pages/governance.adoc
  5. 5
      test/token/ERC721/ERC721.behavior.js
  6. 338
      test/token/ERC721/extensions/ERC721Wrapper.test.js

5
.changeset/early-oranges-raise.md
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@ -0,0 +1,5 @@
---
'openzeppelin-solidity': minor
---
`ERC721Wrapper`: add a new extension of the `ERC721` token which wraps an underlying token. Deposit and withdraw guarantee that the ownership of each token is backed by a corresponding underlying token with the same identifier.

3
contracts/token/ERC721/README.adoc
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@ -28,6 +28,7 @@ Additionally there are a few of other extensions:
* {ERC721Royalty}: A way to signal royalty information following ERC2981.
* {ERC721Pausable}: A primitive to pause contract operation.
* {ERC721Burnable}: A way for token holders to burn their own tokens.
* {ERC721Wrapper}: Wrapper to create an ERC721 backed by another ERC721, with deposit and withdraw methods. Useful in conjunction with {ERC721Votes}.
NOTE: This core set of contracts is designed to be unopinionated, allowing developers to access the internal functions in ERC721 (such as <<ERC721-_mint-address-uint256-,`_mint`>>) and expose them as external functions in the way they prefer. On the other hand, xref:ROOT:erc721.adoc#Presets[ERC721 Presets] (such as {ERC721PresetMinterPauserAutoId}) are designed using opinionated patterns to provide developers with ready to use, deployable contracts.
@ -59,6 +60,8 @@ NOTE: This core set of contracts is designed to be unopinionated, allowing devel
{{ERC721Royalty}}
{{ERC721Wrapper}}
== Presets
These contracts are preconfigured combinations of the above features. They can be used through inheritance or as models to copy and paste their source code.

102
contracts/token/ERC721/extensions/ERC721Wrapper.sol
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@ -0,0 +1,102 @@
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
import "../ERC721.sol";
import "../utils/ERC721Holder.sol";
/**
* @dev Extension of the ERC721 token contract to support token wrapping.
*
* Users can deposit and withdraw an "underlying token" and receive a "wrapped token" with a matching tokenId. This is useful
* in conjunction with other modules. For example, combining this wrapping mechanism with {ERC721Votes} will allow the
* wrapping of an existing "basic" ERC721 into a governance token.
*
* _Available since v4.9.0_
*/
abstract contract ERC721Wrapper is ERC721, ERC721Holder {
IERC721 private immutable _underlying;
// Kept as bytes12 so it can be packed with an address
// Equal to 0xb125e89df18e2ceac5fd2fa8
bytes12 public constant WRAPPER_ACCEPT_MAGIC = bytes12(keccak256("WRAPPER_ACCEPT_MAGIC"));
constructor(IERC721 underlyingToken) {
_underlying = underlyingToken;
}
/**
* @dev Allow a user to deposit underlying tokens and mint the corresponding tokenIds.
*/
function depositFor(address account, uint256[] memory tokenIds) public virtual returns (bool) {
bytes memory data = abi.encodePacked(WRAPPER_ACCEPT_MAGIC, account);
uint256 length = tokenIds.length;
for (uint256 i = 0; i < length; ++i) {
underlying().safeTransferFrom(_msgSender(), address(this), tokenIds[i], data);
}
return true;
}
/**
* @dev Allow a user to burn wrapped tokens and withdraw the corresponding tokenIds of the underlying tokens.
*/
function withdrawTo(address account, uint256[] memory tokenIds) public virtual returns (bool) {
uint256 length = tokenIds.length;
for (uint256 i = 0; i < length; ++i) {
uint256 tokenId = tokenIds[i];
require(_isApprovedOrOwner(_msgSender(), tokenId), "ERC721Wrapper: caller is not token owner or approved");
_burn(tokenId);
// Checks were already performed at this point, and there's no way to retake ownership or approval from
// the wrapped tokenId after this point, so it's safe to remove the reentrancy check for the next line.
// slither-disable-next-line reentrancy-no-eth
underlying().safeTransferFrom(address(this), account, tokenId);
}
return true;
}
/**
* @dev Overrides {IERC721Receiver-onERC721Received} to allow minting on direct ERC721 transfers to
* this contract.
*
* In case there's data attached, it validates that the sender is aware of this contract's existence and behavior
* by checking a magic value (`WRAPPER_ACCEPT_MAGIC`) in the first 12 bytes. If it also matches, the rest 20
* bytes are used as an address to send the tokens to.
*
* WARNING: Doesn't work with unsafe transfers (eg. {IERC721-transferFrom}). Use {ERC721Wrapper-_recover}
* for recovering in that scenario.
*/
function onERC721Received(
address,
address from,
uint256 tokenId,
bytes memory data
) public override returns (bytes4) {
require(address(underlying()) == _msgSender(), "ERC721Wrapper: caller is not underlying");
if (data.length > 0) {
require(data.length == 32 && WRAPPER_ACCEPT_MAGIC == bytes12(data), "ERC721Wrapper: Invalid data format");
from = address(bytes20(bytes32(data) << 96));
}
_safeMint(from, tokenId);
return IERC721Receiver.onERC721Received.selector;
}
/**
* @dev Mint a wrapped token to cover any underlyingToken that would have been transferred by mistake. Internal
* function that can be exposed with access control if desired.
*/
function _recover(address account, uint256 tokenId) internal virtual returns (uint256) {
require(underlying().ownerOf(tokenId) == address(this), "ERC721Wrapper: wrapper is not token owner");
_safeMint(account, tokenId);
return tokenId;
}
/**
* @dev Returns the underlying token.
*/
function underlying() public view virtual returns (IERC721) {
return _underlying;
}
}

2
docs/modules/ROOT/pages/governance.adoc
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@ -119,7 +119,7 @@ contract MyToken is ERC20, ERC20Permit, ERC20Votes, ERC20Wrapper {
}
```
NOTE: Voting power could be determined in different ways: multiple ERC20 tokens, ERC721 tokens, sybil resistant identities, etc. All of these options are potentially supported by writing a custom Votes module for your Governor. The only other source of voting power available in OpenZeppelin Contracts currently is xref:api:token/ERC721.adoc#ERC721Votes[`ERC721Votes`].
NOTE:The only other source of voting power available in OpenZeppelin Contracts currently is xref:api:token/ERC721.adoc#ERC721Votes[`ERC721Votes`]. ERC721 tokens that don't provide this functionality can be wrapped into a voting tokens using a combination of xref:api:token/ERC721.adoc#ERC721Votes[`ERC721Votes`] and xref:api:token/ERC721Wrapper.adoc#ERC721Wrapper[`ERC721Wrapper`].
=== Governor

5
test/token/ERC721/ERC721.behavior.js
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@ -5,6 +5,7 @@ const { ZERO_ADDRESS } = constants;
const { shouldSupportInterfaces } = require('../../utils/introspection/SupportsInterface.behavior');
const ERC721ReceiverMock = artifacts.require('ERC721ReceiverMock');
const NonERC721ReceiverMock = artifacts.require('CallReceiverMock');
const Error = ['None', 'RevertWithMessage', 'RevertWithoutMessage', 'Panic'].reduce(
(acc, entry, idx) => Object.assign({ [entry]: idx }, acc),
@ -316,7 +317,7 @@ function shouldBehaveLikeERC721(errorPrefix, owner, newOwner, approved, anotherA
describe('to a contract that does not implement the required function', function () {
it('reverts', async function () {
const nonReceiver = this.token;
const nonReceiver = await NonERC721ReceiverMock.new();
await expectRevert(
this.token.safeTransferFrom(owner, nonReceiver.address, tokenId, { from: owner }),
'ERC721: transfer to non ERC721Receiver implementer',
@ -392,7 +393,7 @@ function shouldBehaveLikeERC721(errorPrefix, owner, newOwner, approved, anotherA
context('to a contract that does not implement the required function', function () {
it('reverts', async function () {
const nonReceiver = this.token;
const nonReceiver = await NonERC721ReceiverMock.new();
await expectRevert(
this.token.$_safeMint(nonReceiver.address, tokenId),
'ERC721: transfer to non ERC721Receiver implementer',

338
test/token/ERC721/extensions/ERC721Wrapper.test.js
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@ -0,0 +1,338 @@
const { BN, expectEvent, constants, expectRevert } = require('@openzeppelin/test-helpers');
const { expect } = require('chai');
const { keccakFromString, bufferToHex } = require('ethereumjs-util');
const { shouldBehaveLikeERC721 } = require('../ERC721.behavior');
const ERC721 = artifacts.require('$ERC721');
const ERC721Wrapper = artifacts.require('$ERC721Wrapper');
contract('ERC721Wrapper', function (accounts) {
const [initialHolder, anotherAccount, approvedAccount] = accounts;
const name = 'My Token';
const symbol = 'MTKN';
const firstTokenId = new BN(1);
const secondTokenId = new BN(2);
beforeEach(async function () {
this.underlying = await ERC721.new(name, symbol);
this.token = await ERC721Wrapper.new(`Wrapped ${name}`, `W${symbol}`, this.underlying.address);
await this.underlying.$_safeMint(initialHolder, firstTokenId);
await this.underlying.$_safeMint(initialHolder, secondTokenId);
});
it('has a name', async function () {
expect(await this.token.name()).to.equal(`Wrapped ${name}`);
});
it('has a symbol', async function () {
expect(await this.token.symbol()).to.equal(`W${symbol}`);
});
it('has underlying', async function () {
expect(await this.token.underlying()).to.be.bignumber.equal(this.underlying.address);
});
describe('depositFor', function () {
it('works with token approval', async function () {
await this.underlying.approve(this.token.address, firstTokenId, { from: initialHolder });
const { tx } = await this.token.depositFor(initialHolder, [firstTokenId], { from: initialHolder });
await expectEvent.inTransaction(tx, this.underlying, 'Transfer', {
from: initialHolder,
to: this.token.address,
tokenId: firstTokenId,
});
await expectEvent.inTransaction(tx, this.token, 'Transfer', {
from: constants.ZERO_ADDRESS,
to: initialHolder,
tokenId: firstTokenId,
});
});
it('works with approval for all', async function () {
await this.underlying.setApprovalForAll(this.token.address, true, { from: initialHolder });
const { tx } = await this.token.depositFor(initialHolder, [firstTokenId], { from: initialHolder });
await expectEvent.inTransaction(tx, this.underlying, 'Transfer', {
from: initialHolder,
to: this.token.address,
tokenId: firstTokenId,
});
await expectEvent.inTransaction(tx, this.token, 'Transfer', {
from: constants.ZERO_ADDRESS,
to: initialHolder,
tokenId: firstTokenId,
});
});
it('works sending to another account', async function () {
await this.underlying.approve(this.token.address, firstTokenId, { from: initialHolder });
const { tx } = await this.token.depositFor(anotherAccount, [firstTokenId], { from: initialHolder });
await expectEvent.inTransaction(tx, this.underlying, 'Transfer', {
from: initialHolder,
to: this.token.address,
tokenId: firstTokenId,
});
await expectEvent.inTransaction(tx, this.token, 'Transfer', {
from: constants.ZERO_ADDRESS,
to: anotherAccount,
tokenId: firstTokenId,
});
});
it('works with multiple tokens', async function () {
await this.underlying.approve(this.token.address, firstTokenId, { from: initialHolder });
await this.underlying.approve(this.token.address, secondTokenId, { from: initialHolder });
const { tx } = await this.token.depositFor(initialHolder, [firstTokenId, secondTokenId], { from: initialHolder });
await expectEvent.inTransaction(tx, this.underlying, 'Transfer', {
from: initialHolder,
to: this.token.address,
tokenId: firstTokenId,
});
await expectEvent.inTransaction(tx, this.token, 'Transfer', {
from: constants.ZERO_ADDRESS,
to: initialHolder,
tokenId: firstTokenId,
});
await expectEvent.inTransaction(tx, this.underlying, 'Transfer', {
from: initialHolder,
to: this.token.address,
tokenId: secondTokenId,
});
await expectEvent.inTransaction(tx, this.token, 'Transfer', {
from: constants.ZERO_ADDRESS,
to: initialHolder,
tokenId: secondTokenId,
});
});
it('reverts with missing approval', async function () {
await expectRevert(
this.token.depositFor(initialHolder, [firstTokenId], { from: initialHolder }),
'ERC721: caller is not token owner or approved',
);
});
});
describe('withdrawTo', function () {
beforeEach(async function () {
await this.underlying.approve(this.token.address, firstTokenId, { from: initialHolder });
await this.token.depositFor(initialHolder, [firstTokenId], { from: initialHolder });
});
it('works for an owner', async function () {
const { tx } = await this.token.withdrawTo(initialHolder, [firstTokenId], { from: initialHolder });
await expectEvent.inTransaction(tx, this.underlying, 'Transfer', {
from: this.token.address,
to: initialHolder,
tokenId: firstTokenId,
});
await expectEvent.inTransaction(tx, this.token, 'Transfer', {
from: initialHolder,
to: constants.ZERO_ADDRESS,
tokenId: firstTokenId,
});
});
it('works for an approved', async function () {
await this.token.approve(approvedAccount, firstTokenId, { from: initialHolder });
const { tx } = await this.token.withdrawTo(initialHolder, [firstTokenId], { from: approvedAccount });
await expectEvent.inTransaction(tx, this.underlying, 'Transfer', {
from: this.token.address,
to: initialHolder,
tokenId: firstTokenId,
});
await expectEvent.inTransaction(tx, this.token, 'Transfer', {
from: initialHolder,
to: constants.ZERO_ADDRESS,
tokenId: firstTokenId,
});
});
it('works for an approved for all', async function () {
await this.token.setApprovalForAll(approvedAccount, true, { from: initialHolder });
const { tx } = await this.token.withdrawTo(initialHolder, [firstTokenId], { from: approvedAccount });
await expectEvent.inTransaction(tx, this.underlying, 'Transfer', {
from: this.token.address,
to: initialHolder,
tokenId: firstTokenId,
});
await expectEvent.inTransaction(tx, this.token, 'Transfer', {
from: initialHolder,
to: constants.ZERO_ADDRESS,
tokenId: firstTokenId,
});
});
it("doesn't work for a non-owner nor approved", async function () {
await expectRevert(
this.token.withdrawTo(initialHolder, [firstTokenId], { from: anotherAccount }),
'ERC721Wrapper: caller is not token owner or approved',
);
});
it('works with multiple tokens', async function () {
await this.underlying.approve(this.token.address, secondTokenId, { from: initialHolder });
await this.token.depositFor(initialHolder, [secondTokenId], { from: initialHolder });
const { tx } = await this.token.withdrawTo(initialHolder, [firstTokenId, secondTokenId], { from: initialHolder });
await expectEvent.inTransaction(tx, this.underlying, 'Transfer', {
from: this.token.address,
to: initialHolder,
tokenId: firstTokenId,
});
await expectEvent.inTransaction(tx, this.token, 'Transfer', {
from: initialHolder,
to: constants.ZERO_ADDRESS,
tokenId: firstTokenId,
});
});
it('works to another account', async function () {
const { tx } = await this.token.withdrawTo(anotherAccount, [firstTokenId], { from: initialHolder });
await expectEvent.inTransaction(tx, this.underlying, 'Transfer', {
from: this.token.address,
to: anotherAccount,
tokenId: firstTokenId,
});
await expectEvent.inTransaction(tx, this.token, 'Transfer', {
from: initialHolder,
to: constants.ZERO_ADDRESS,
tokenId: firstTokenId,
});
});
});
describe('onERC721Received', function () {
const WRAPPER_ACCEPT_MAGIC = bufferToHex(keccakFromString('WRAPPER_ACCEPT_MAGIC')).slice(0, 26); // Include 0x
const magicWithAddresss = address =>
web3.utils.encodePacked(
{
value: WRAPPER_ACCEPT_MAGIC,
type: 'bytes12',
},
{
value: address,
type: 'address',
},
);
it('only allows calls from underlying', async function () {
await expectRevert(
this.token.onERC721Received(
initialHolder,
this.token.address,
firstTokenId,
magicWithAddresss(anotherAccount), // Correct data
{ from: anotherAccount },
),
'ERC721Wrapper: caller is not underlying',
);
});
describe('when data length is > 0', function () {
it('reverts with arbitrary data', async function () {
await expectRevert(
this.underlying.methods['safeTransferFrom(address,address,uint256,bytes)'](
initialHolder,
this.token.address,
firstTokenId,
'0x0123',
{
from: initialHolder,
},
),
'ERC721Wrapper: Invalid data format',
);
});
it('reverts with the magic value and data length different to 32', async function () {
await expectRevert(
this.underlying.methods['safeTransferFrom(address,address,uint256,bytes)'](
initialHolder,
this.token.address,
firstTokenId,
WRAPPER_ACCEPT_MAGIC, // Reverts for any non-32 bytes value
{
from: initialHolder,
},
),
'ERC721Wrapper: Invalid data format',
);
});
it('mints token to specific holder with address after magic value', async function () {
const { tx } = await this.underlying.methods['safeTransferFrom(address,address,uint256,bytes)'](
initialHolder,
this.token.address,
firstTokenId,
magicWithAddresss(anotherAccount),
{
from: initialHolder,
},
);
await expectEvent.inTransaction(tx, this.token, 'Transfer', {
from: constants.ZERO_ADDRESS,
to: anotherAccount,
tokenId: firstTokenId,
});
});
});
it('mints a token to from if no data is specified', async function () {
const { tx } = await this.underlying.safeTransferFrom(initialHolder, this.token.address, firstTokenId, {
from: initialHolder,
});
await expectEvent.inTransaction(tx, this.token, 'Transfer', {
from: constants.ZERO_ADDRESS,
to: initialHolder,
tokenId: firstTokenId,
});
});
});
describe('_recover', function () {
it('works if there is something to recover', async function () {
// Should use `transferFrom` to avoid `onERC721Received` minting
await this.underlying.transferFrom(initialHolder, this.token.address, firstTokenId, { from: initialHolder });
const { tx } = await this.token.$_recover(anotherAccount, firstTokenId);
await expectEvent.inTransaction(tx, this.token, 'Transfer', {
from: constants.ZERO_ADDRESS,
to: anotherAccount,
tokenId: firstTokenId,
});
});
it('reverts if there is nothing to recover', async function () {
await expectRevert(
this.token.$_recover(initialHolder, firstTokenId),
'ERC721Wrapper: wrapper is not token owner',
);
});
});
describe('ERC712 behavior', function () {
shouldBehaveLikeERC721('ERC721', ...accounts);
});
});
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