Avoid returndatacopy in ERC2771Forwarder by calling via assembly (#4458)
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@ -41,12 +41,13 @@ contract('ERC2771Forwarder', function (accounts) {
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this.alice.address = web3.utils.toChecksumAddress(this.alice.getAddressString());
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this.timestamp = await time.latest();
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this.receiver = await CallReceiverMock.new();
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this.request = {
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from: this.alice.address,
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to: constants.ZERO_ADDRESS,
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to: this.receiver.address,
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value: '0',
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gas: '100000',
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data: '0x',
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data: this.receiver.contract.methods.mockFunction().encodeABI(),
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deadline: this.timestamp.toNumber() + 60, // 1 minute
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};
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this.requestData = {
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@ -64,6 +65,14 @@ contract('ERC2771Forwarder', function (accounts) {
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ethSigUtil.signTypedMessage(privateKey, {
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data: this.forgeData(request),
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});
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this.estimateRequest = request =>
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web3.eth.estimateGas({
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from: this.forwarder.address,
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to: request.to,
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data: web3.utils.encodePacked({ value: request.data, type: 'bytes' }, { value: request.from, type: 'address' }),
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value: request.value,
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gas: request.gas,
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});
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this.requestData.signature = this.sign(this.alice.getPrivateKey());
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});
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@ -125,7 +134,8 @@ contract('ERC2771Forwarder', function (accounts) {
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it('emits an event and consumes nonce for a successful request', async function () {
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const receipt = await this.forwarder.execute(this.requestData);
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expectEvent(receipt, 'ExecutedForwardRequest', {
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await expectEvent.inTransaction(receipt.tx, this.receiver, 'MockFunctionCalled');
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await expectEvent.inTransaction(receipt.tx, this.forwarder, 'ExecutedForwardRequest', {
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signer: this.requestData.from,
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nonce: web3.utils.toBN(this.requestData.nonce),
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success: true,
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@ -136,11 +146,9 @@ contract('ERC2771Forwarder', function (accounts) {
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});
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it('reverts with an unsuccessful request', async function () {
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const receiver = await CallReceiverMock.new();
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const req = {
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...this.requestData,
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to: receiver.address,
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data: receiver.contract.methods.mockFunctionRevertsNoReason().encodeABI(),
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data: this.receiver.contract.methods.mockFunctionRevertsNoReason().encodeABI(),
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};
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req.signature = this.sign(this.alice.getPrivateKey(), req);
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await expectRevertCustomError(this.forwarder.execute(req), 'FailedInnerCall', []);
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@ -208,14 +216,11 @@ contract('ERC2771Forwarder', function (accounts) {
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});
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it('bubbles out of gas', async function () {
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const receiver = await CallReceiverMock.new();
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const gasAvailable = 100000;
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this.requestData.to = receiver.address;
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this.requestData.data = receiver.contract.methods.mockFunctionOutOfGas().encodeABI();
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this.requestData.gas = 1000000;
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this.requestData.data = this.receiver.contract.methods.mockFunctionOutOfGas().encodeABI();
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this.requestData.gas = 1_000_000;
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this.requestData.signature = this.sign(this.alice.getPrivateKey());
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const gasAvailable = 100_000;
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await expectRevert.assertion(this.forwarder.execute(this.requestData, { gas: gasAvailable }));
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const { transactions } = await web3.eth.getBlock('latest');
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@ -223,6 +228,32 @@ contract('ERC2771Forwarder', function (accounts) {
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expect(gasUsed).to.be.equal(gasAvailable);
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});
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it('bubbles out of gas forced by the relayer', async function () {
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// If there's an incentive behind executing requests, a malicious relayer could grief
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// the forwarder by executing requests and providing a top-level call gas limit that
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// is too low to successfully finish the request after the 63/64 rule.
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// We set the baseline to the gas limit consumed by a successful request if it was executed
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// normally. Note this includes the 21000 buffer that also the relayer will be charged to
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// start a request execution.
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const estimate = await this.estimateRequest(this.request);
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// Because the relayer call consumes gas until the `CALL` opcode, the gas left after failing
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// the subcall won't enough to finish the top level call (after testing), so we add a
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// moderated buffer.
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const gasAvailable = estimate + 2_000;
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// The subcall out of gas should be caught by the contract and then bubbled up consuming
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// the available gas with an `invalid` opcode.
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await expectRevert.outOfGas(this.forwarder.execute(this.requestData, { gas: gasAvailable }));
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const { transactions } = await web3.eth.getBlock('latest');
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const { gasUsed } = await web3.eth.getTransactionReceipt(transactions[0]);
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// We assert that indeed the gas was totally consumed.
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expect(gasUsed).to.be.equal(gasAvailable);
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});
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});
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context('executeBatch', function () {
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@ -252,6 +283,14 @@ contract('ERC2771Forwarder', function (accounts) {
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}));
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this.msgValue = batchValue(this.requestDatas);
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this.gasUntil = async reqIdx => {
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const gas = 0;
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const estimations = await Promise.all(
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new Array(reqIdx + 1).fill().map((_, idx) => this.estimateRequest(this.requestDatas[idx])),
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);
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return estimations.reduce((acc, estimation) => acc + estimation, gas);
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};
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});
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context('with valid requests', function () {
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@ -265,7 +304,8 @@ contract('ERC2771Forwarder', function (accounts) {
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it('emits events', async function () {
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for (const request of this.requestDatas) {
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expectEvent(this.receipt, 'ExecutedForwardRequest', {
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await expectEvent.inTransaction(this.receipt.tx, this.receiver, 'MockFunctionCalled');
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await expectEvent.inTransaction(this.receipt.tx, this.forwarder, 'ExecutedForwardRequest', {
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signer: request.from,
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nonce: web3.utils.toBN(request.nonce),
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success: true,
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@ -428,6 +468,52 @@ contract('ERC2771Forwarder', function (accounts) {
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);
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});
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});
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it('bubbles out of gas', async function () {
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this.requestDatas[this.idx].data = this.receiver.contract.methods.mockFunctionOutOfGas().encodeABI();
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this.requestDatas[this.idx].gas = 1_000_000;
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this.requestDatas[this.idx].signature = this.sign(
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this.signers[this.idx].getPrivateKey(),
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this.requestDatas[this.idx],
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);
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const gasAvailable = 300_000;
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await expectRevert.assertion(
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this.forwarder.executeBatch(this.requestDatas, constants.ZERO_ADDRESS, {
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gas: gasAvailable,
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value: this.requestDatas.reduce((acc, { value }) => acc + Number(value), 0),
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}),
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);
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const { transactions } = await web3.eth.getBlock('latest');
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const { gasUsed } = await web3.eth.getTransactionReceipt(transactions[0]);
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expect(gasUsed).to.be.equal(gasAvailable);
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});
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it('bubbles out of gas forced by the relayer', async function () {
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// Similarly to the single execute, a malicious relayer could grief requests.
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// We estimate until the selected request as if they were executed normally
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const estimate = await this.gasUntil(this.requestDatas, this.idx);
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// We add a Buffer to account for all the gas that's used before the selected call.
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// Note is slightly bigger because the selected request is not the index 0 and it affects
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// the buffer needed.
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const gasAvailable = estimate + 10_000;
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// The subcall out of gas should be caught by the contract and then bubbled up consuming
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// the available gas with an `invalid` opcode.
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await expectRevert.outOfGas(
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this.forwarder.executeBatch(this.requestDatas, constants.ZERO_ADDRESS, { gas: gasAvailable }),
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);
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const { transactions } = await web3.eth.getBlock('latest');
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const { gasUsed } = await web3.eth.getTransactionReceipt(transactions[0]);
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// We assert that indeed the gas was totally consumed.
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expect(gasUsed).to.be.equal(gasAvailable);
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});
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});
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});
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});
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