Skip to content

Commit

Permalink
Reduce ERC20 allowance before triggering transfer (OpenZeppelin#3056)
Browse files Browse the repository at this point in the history 
* Reduce ERC20 allowance before triggering transfer

* adapt ERC777 to reduce allowance before transfer

* fix test for ERC777

* use smaller number to reduce balance

* simplify test description

* don't use deprecated expectEvents.inLogs

* fix test

Co-authored-by: Hadrien Croubois <hadrien.croubois@gmail.com>
  • Loading branch information
@frangio @Amxx
frangio and Amxx authored Dec 31, 2021
1 parent ef0273f commit a9f994f
Show file tree
Hide file tree
Showing 5 changed files with 90 additions and 93 deletions.
1 change: 1 addition & 0 deletions CHANGELOG.md
View file
Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,7 @@
* `ERC721Votes`: Added an extension of ERC721 enabled with vote tracking and delegation. ([#2944](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2944))
* `ERC2771Context`: use immutable storage to store the forwarder address, no longer an issue since Solidity >=0.8.8 allows reading immutable variables in the constructor. ([#2917](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2917))
* `Base64`: add a library to parse bytes into base64 strings using `encode(bytes memory)` function, and provide examples to show how to use to build URL-safe `tokenURIs` ([#2884](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/#2884))
* `ERC20`: reduce allowance before triggering transfer.

## 4.4.1 (2021-12-14)

Expand Down
4 changes: 2 additions & 2 deletions contracts/token/ERC20/ERC20.sol
View file
Original file line number Diff line number Diff line change
Expand Up @@ -152,14 +152,14 @@ contract ERC20 is Context, IERC20, IERC20Metadata {
address recipient,
uint256 amount
) public virtual override returns (bool) {
_transfer(sender, recipient, amount);

uint256 currentAllowance = _allowances[sender][_msgSender()];
require(currentAllowance >= amount, "ERC20: transfer amount exceeds allowance");
unchecked {
_approve(sender, _msgSender(), currentAllowance - amount);
}

_transfer(sender, recipient, amount);

return true;
}

Expand Down
4 changes: 2 additions & 2 deletions contracts/token/ERC777/ERC777.sol
View file
Original file line number Diff line number Diff line change
Expand Up @@ -287,12 +287,12 @@ contract ERC777 is Context, IERC777, IERC20 {

_callTokensToSend(spender, holder, recipient, amount, "", "");

_move(spender, holder, recipient, amount, "", "");

uint256 currentAllowance = _allowances[holder][spender];
require(currentAllowance >= amount, "ERC777: transfer amount exceeds allowance");
_approve(holder, spender, currentAllowance - amount);

_move(spender, holder, recipient, amount, "", "");

_callTokensReceived(spender, holder, recipient, amount, "", "", false);

return true;
Expand Down
112 changes: 57 additions & 55 deletions test/token/ERC20/ERC20.behavior.js
View file
Original file line number Diff line number Diff line change
Expand Up @@ -40,7 +40,7 @@ function shouldBehaveLikeERC20 (errorPrefix, initialSupply, initialHolder, recip
describe('when the recipient is not the zero address', function () {
const to = anotherAccount;

describe('when the spender has enough approved balance', function () {
describe('when the spender has enough allowance', function () {
beforeEach(async function () {
await this.token.approve(spender, initialSupply, { from: initialHolder });
});
Expand All @@ -63,58 +63,67 @@ function shouldBehaveLikeERC20 (errorPrefix, initialSupply, initialHolder, recip
});

it('emits a transfer event', async function () {
const { logs } = await this.token.transferFrom(tokenOwner, to, amount, { from: spender });

expectEvent.inLogs(logs, 'Transfer', {
from: tokenOwner,
to: to,
value: amount,
});
expectEvent(
await this.token.transferFrom(tokenOwner, to, amount, { from: spender }),
'Transfer',
{ from: tokenOwner, to: to, value: amount },
);
});

it('emits an approval event', async function () {
const { logs } = await this.token.transferFrom(tokenOwner, to, amount, { from: spender });

expectEvent.inLogs(logs, 'Approval', {
owner: tokenOwner,
spender: spender,
value: await this.token.allowance(tokenOwner, spender),
});
expectEvent(
await this.token.transferFrom(tokenOwner, to, amount, { from: spender }),
'Approval',
{ owner: tokenOwner, spender: spender, value: await this.token.allowance(tokenOwner, spender) },
);
});
});

describe('when the token owner does not have enough balance', function () {
const amount = initialSupply.addn(1);
const amount = initialSupply;

beforeEach('reducing balance', async function () {
await this.token.transfer(to, 1, { from: tokenOwner });
});

it('reverts', async function () {
await expectRevert(this.token.transferFrom(
tokenOwner, to, amount, { from: spender }), `${errorPrefix}: transfer amount exceeds balance`,
await expectRevert(
this.token.transferFrom(tokenOwner, to, amount, { from: spender }),
`${errorPrefix}: transfer amount exceeds balance`,
);
});
});
});

describe('when the spender does not have enough approved balance', function () {
describe('when the spender does not have enough allowance', function () {
const allowance = initialSupply.subn(1);

beforeEach(async function () {
await this.token.approve(spender, initialSupply.subn(1), { from: tokenOwner });
await this.token.approve(spender, allowance, { from: tokenOwner });
});

describe('when the token owner has enough balance', function () {
const amount = initialSupply;

it('reverts', async function () {
await expectRevert(this.token.transferFrom(
tokenOwner, to, amount, { from: spender }), `${errorPrefix}: transfer amount exceeds allowance`,
await expectRevert(
this.token.transferFrom(tokenOwner, to, amount, { from: spender }),
`${errorPrefix}: transfer amount exceeds allowance`,
);
});
});

describe('when the token owner does not have enough balance', function () {
const amount = initialSupply.addn(1);
const amount = allowance;

beforeEach('reducing balance', async function () {
await this.token.transfer(to, 2, { from: tokenOwner });
});

it('reverts', async function () {
await expectRevert(this.token.transferFrom(
tokenOwner, to, amount, { from: spender }), `${errorPrefix}: transfer amount exceeds balance`,
await expectRevert(
this.token.transferFrom(tokenOwner, to, amount, { from: spender }),
`${errorPrefix}: transfer amount exceeds balance`,
);
});
});
Expand Down Expand Up @@ -143,8 +152,9 @@ function shouldBehaveLikeERC20 (errorPrefix, initialSupply, initialHolder, recip
const to = recipient;

it('reverts', async function () {
await expectRevert(this.token.transferFrom(
tokenOwner, to, amount, { from: spender }), `${errorPrefix}: transfer from the zero address`,
await expectRevert(
this.token.transferFrom(tokenOwner, to, amount, { from: spender }),
'from the zero address',
);
});
});
Expand Down Expand Up @@ -183,13 +193,11 @@ function shouldBehaveLikeERC20Transfer (errorPrefix, from, to, balance, transfer
});

it('emits a transfer event', async function () {
const { logs } = await transfer.call(this, from, to, amount);

expectEvent.inLogs(logs, 'Transfer', {
from,
to,
value: amount,
});
expectEvent(
await transfer.call(this, from, to, amount),
'Transfer',
{ from, to, value: amount },
);
});
});

Expand All @@ -205,13 +213,11 @@ function shouldBehaveLikeERC20Transfer (errorPrefix, from, to, balance, transfer
});

it('emits a transfer event', async function () {
const { logs } = await transfer.call(this, from, to, amount);

expectEvent.inLogs(logs, 'Transfer', {
from,
to,
value: amount,
});
expectEvent(
await transfer.call(this, from, to, amount),
'Transfer',
{ from, to, value: amount },
);
});
});
});
Expand All @@ -231,13 +237,11 @@ function shouldBehaveLikeERC20Approve (errorPrefix, owner, spender, supply, appr
const amount = supply;

it('emits an approval event', async function () {
const { logs } = await approve.call(this, owner, spender, amount);

expectEvent.inLogs(logs, 'Approval', {
owner: owner,
spender: spender,
value: amount,
});
expectEvent(
await approve.call(this, owner, spender, amount),
'Approval',
{ owner: owner, spender: spender, value: amount },
);
});

describe('when there was no approved amount before', function () {
Expand Down Expand Up @@ -265,13 +269,11 @@ function shouldBehaveLikeERC20Approve (errorPrefix, owner, spender, supply, appr
const amount = supply.addn(1);

it('emits an approval event', async function () {
const { logs } = await approve.call(this, owner, spender, amount);

expectEvent.inLogs(logs, 'Approval', {
owner: owner,
spender: spender,
value: amount,
});
expectEvent(
await approve.call(this, owner, spender, amount),
'Approval',
{ owner: owner, spender: spender, value: amount },
);
});

describe('when there was no approved amount before', function () {
Expand Down
62 changes: 28 additions & 34 deletions test/token/ERC20/ERC20.test.js
View file
Original file line number Diff line number Diff line change
Expand Up @@ -63,17 +63,15 @@ contract('ERC20', function (accounts) {
const approvedAmount = amount;

beforeEach(async function () {
({ logs: this.logs } = await this.token.approve(spender, approvedAmount, { from: initialHolder }));
await this.token.approve(spender, approvedAmount, { from: initialHolder });
});

it('emits an approval event', async function () {
const { logs } = await this.token.decreaseAllowance(spender, approvedAmount, { from: initialHolder });

expectEvent.inLogs(logs, 'Approval', {
owner: initialHolder,
spender: spender,
value: new BN(0),
});
expectEvent(
await this.token.decreaseAllowance(spender, approvedAmount, { from: initialHolder }),
'Approval',
{ owner: initialHolder, spender: spender, value: new BN(0) },
);
});

it('decreases the spender allowance subtracting the requested amount', async function () {
Expand Down Expand Up @@ -129,13 +127,11 @@ contract('ERC20', function (accounts) {

describe('when the sender has enough balance', function () {
it('emits an approval event', async function () {
const { logs } = await this.token.increaseAllowance(spender, amount, { from: initialHolder });

expectEvent.inLogs(logs, 'Approval', {
owner: initialHolder,
spender: spender,
value: amount,
});
expectEvent(
await this.token.increaseAllowance(spender, amount, { from: initialHolder }),
'Approval',
{ owner: initialHolder, spender: spender, value: amount },
);
});

describe('when there was no approved amount before', function () {
Expand Down Expand Up @@ -163,13 +159,11 @@ contract('ERC20', function (accounts) {
const amount = initialSupply.addn(1);

it('emits an approval event', async function () {
const { logs } = await this.token.increaseAllowance(spender, amount, { from: initialHolder });

expectEvent.inLogs(logs, 'Approval', {
owner: initialHolder,
spender: spender,
value: amount,
});
expectEvent(
await this.token.increaseAllowance(spender, amount, { from: initialHolder }),
'Approval',
{ owner: initialHolder, spender: spender, value: amount },
);
});

describe('when there was no approved amount before', function () {
Expand Down Expand Up @@ -215,8 +209,7 @@ contract('ERC20', function (accounts) {

describe('for a non zero account', function () {
beforeEach('minting', async function () {
const { logs } = await this.token.mint(recipient, amount);
this.logs = logs;
this.receipt = await this.token.mint(recipient, amount);
});

it('increments totalSupply', async function () {
Expand All @@ -229,10 +222,11 @@ contract('ERC20', function (accounts) {
});

it('emits Transfer event', async function () {
const event = expectEvent.inLogs(this.logs, 'Transfer', {
from: ZERO_ADDRESS,
to: recipient,
});
const event = expectEvent(
this.receipt,
'Transfer',
{ from: ZERO_ADDRESS, to: recipient },
);

expect(event.args.value).to.be.bignumber.equal(amount);
});
Expand All @@ -255,8 +249,7 @@ contract('ERC20', function (accounts) {
const describeBurn = function (description, amount) {
describe(description, function () {
beforeEach('burning', async function () {
const { logs } = await this.token.burn(initialHolder, amount);
this.logs = logs;
this.receipt = await this.token.burn(initialHolder, amount);
});

it('decrements totalSupply', async function () {
Expand All @@ -270,10 +263,11 @@ contract('ERC20', function (accounts) {
});

it('emits Transfer event', async function () {
const event = expectEvent.inLogs(this.logs, 'Transfer', {
from: initialHolder,
to: ZERO_ADDRESS,
});
const event = expectEvent(
this.receipt,
'Transfer',
{ from: initialHolder, to: ZERO_ADDRESS },
);

expect(event.args.value).to.be.bignumber.equal(amount);
});
Expand Down

0 comments on commit a9f994f

Please sign in to comment.