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Fix balance and allowance checks in _burn and _burnFrom #1218

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Merged
merged 3 commits into from
Aug 17, 2018
Merged

Fix balance and allowance checks in _burn and _burnFrom #1218

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1721186
fix off by one error in _burn and _burnFrom
frangio Aug 17, 2018
b384386
add tests for off-by-one error
frangio Aug 17, 2018
f88c273
change amount used
frangio Aug 17, 2018
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4 changes: 2 additions & 2 deletions contracts/token/ERC20/StandardToken.sol
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Original file line number Diff line number Diff line change
Expand Up @@ -178,7 +178,7 @@ contract StandardToken is ERC20 {
*/
function _burn(address _account, uint256 _amount) internal {
require(_account != 0);
require(balances[_account] > _amount);
require(_amount <= balances[_account]);

totalSupply_ = totalSupply_.sub(_amount);
balances[_account] = balances[_account].sub(_amount);
Expand All @@ -193,7 +193,7 @@ contract StandardToken is ERC20 {
* @param _amount The amount that will be burnt.
*/
function _burnFrom(address _account, uint256 _amount) internal {
require(allowed[_account][msg.sender] > _amount);
require(_amount <= allowed[_account][msg.sender]);

// Should https://github.com/OpenZeppelin/zeppelin-solidity/issues/707 be accepted,
// this function needs to emit an event with the updated approval.
Expand Down
104 changes: 56 additions & 48 deletions test/token/ERC20/StandardToken.test.js
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Original file line number Diff line number Diff line change
Expand Up @@ -526,49 +526,52 @@ contract('StandardToken', function ([_, owner, recipient, anotherAccount]) {

describe('_burn', function () {
const initialSupply = new BigNumber(100);
const amount = new BigNumber(50);

it('rejects a null account', async function () {
await assertRevert(this.token.burn(ZERO_ADDRESS, amount));
await assertRevert(this.token.burn(ZERO_ADDRESS, 1));
});

describe('for a non null account', function () {
it('rejects burning more than balance', async function () {
await assertRevert(this.token.burn(owner, initialSupply.plus(1)));
});

describe('for less amount than balance', function () {
beforeEach('burning', async function () {
const { logs } = await this.token.burn(owner, amount);
this.logs = logs;
});

it('decrements totalSupply', async function () {
const expectedSupply = initialSupply.minus(amount);
(await this.token.totalSupply()).should.be.bignumber.equal(expectedSupply);
});
const describeBurn = function (description, amount) {
describe(description, function () {
beforeEach('burning', async function () {
const { logs } = await this.token.burn(owner, amount);
this.logs = logs;
});

it('decrements owner balance', async function () {
const expectedBalance = initialSupply.minus(amount);
(await this.token.balanceOf(owner)).should.be.bignumber.equal(expectedBalance);
});
it('decrements totalSupply', async function () {
const expectedSupply = initialSupply.minus(amount);
(await this.token.totalSupply()).should.be.bignumber.equal(expectedSupply);
});

it('emits Transfer event', async function () {
const event = expectEvent.inLogs(this.logs, 'Transfer', {
from: owner,
to: ZERO_ADDRESS,
it('decrements owner balance', async function () {
const expectedBalance = initialSupply.minus(amount);
(await this.token.balanceOf(owner)).should.be.bignumber.equal(expectedBalance);
});

event.args.value.should.be.bignumber.equal(amount);
it('emits Transfer event', async function () {
const event = expectEvent.inLogs(this.logs, 'Transfer', {
from: owner,
to: ZERO_ADDRESS,
});

event.args.value.should.be.bignumber.equal(amount);
});
});
});
};

describeBurn('for entire balance', initialSupply);
describeBurn('for less amount than balance', initialSupply.sub(1));
});
});

describe('_burnFrom', function () {
const initialSupply = new BigNumber(100);
const allowance = new BigNumber(70);
const amount = new BigNumber(50);

const spender = anotherAccount;

Expand All @@ -577,7 +580,7 @@ contract('StandardToken', function ([_, owner, recipient, anotherAccount]) {
});

it('rejects a null account', async function () {
await assertRevert(this.token.burnFrom(ZERO_ADDRESS, amount));
await assertRevert(this.token.burnFrom(ZERO_ADDRESS, 1));
});

describe('for a non null account', function () {
Expand All @@ -589,36 +592,41 @@ contract('StandardToken', function ([_, owner, recipient, anotherAccount]) {
await assertRevert(this.token.burnFrom(owner, initialSupply.plus(1)));
});

describe('for less amount than allowance', function () {
beforeEach('burning', async function () {
const { logs } = await this.token.burnFrom(owner, amount, { from: spender });
this.logs = logs;
});

it('decrements totalSupply', async function () {
const expectedSupply = initialSupply.minus(amount);
(await this.token.totalSupply()).should.be.bignumber.equal(expectedSupply);
});
const describeBurnFrom = function (description, amount) {
describe(description, function () {
beforeEach('burning', async function () {
const { logs } = await this.token.burnFrom(owner, amount, { from: spender });
this.logs = logs;
});

it('decrements owner balance', async function () {
const expectedBalance = initialSupply.minus(amount);
(await this.token.balanceOf(owner)).should.be.bignumber.equal(expectedBalance);
});
it('decrements totalSupply', async function () {
const expectedSupply = initialSupply.minus(amount);
(await this.token.totalSupply()).should.be.bignumber.equal(expectedSupply);
});

it('decrements spender allowance', async function () {
const expectedAllowance = allowance.minus(amount);
(await this.token.allowance(owner, spender)).should.be.bignumber.equal(expectedAllowance);
});
it('decrements owner balance', async function () {
const expectedBalance = initialSupply.minus(amount);
(await this.token.balanceOf(owner)).should.be.bignumber.equal(expectedBalance);
});

it('emits Transfer event', async function () {
const event = expectEvent.inLogs(this.logs, 'Transfer', {
from: owner,
to: ZERO_ADDRESS,
it('decrements spender allowance', async function () {
const expectedAllowance = allowance.minus(amount);
(await this.token.allowance(owner, spender)).should.be.bignumber.equal(expectedAllowance);
});

event.args.value.should.be.bignumber.equal(amount);
it('emits Transfer event', async function () {
const event = expectEvent.inLogs(this.logs, 'Transfer', {
from: owner,
to: ZERO_ADDRESS,
});

event.args.value.should.be.bignumber.equal(amount);
});
});
});
};

describeBurnFrom('for entire allowance', allowance);
describeBurnFrom('for less amount than allowance', allowance.sub(1));
});
});
});