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Use invalid opcode to consume all gas in MinimalForwarder #3035

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merged 3 commits into from
Dec 22, 2021
Merged

Use invalid opcode to consume all gas in MinimalForwarder #3035

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dbcfb24
use invalid opcode to consume all gas
Amxx Dec 17, 2021
fcbd319
test out-of-gas-bubbling
Amxx Dec 20, 2021
480f83d
address PR comments
Amxx Dec 21, 2021
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10 changes: 9 additions & 1 deletion contracts/metatx/MinimalForwarder.sol
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Original file line number Diff line number Diff line change
Expand Up @@ -50,9 +50,17 @@ contract MinimalForwarder is EIP712 {
(bool success, bytes memory returndata) = req.to.call{gas: req.gas, value: req.value}(
abi.encodePacked(req.data, req.from)
);

// Validate that the relayer has sent enough gas for the call.
// See https://ronan.eth.link/blog/ethereum-gas-dangers/
assert(gasleft() > req.gas / 63);
if (gasleft() <= req.gas / 63) {
// We explicitly trigger invalid opcode to consume all gas and bubble-up the effects, since
// Panic error do not consume all gas since Solidity 0.8.0
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// https://docs.soliditylang.org/en/v0.8.0/control-structures.html#panic-via-assert-and-error-via-require
assembly {
invalid()
}
}

return (success, returndata);
}
Expand Down
48 changes: 33 additions & 15 deletions test/metatx/MinimalForwarder.test.js
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@ const { expectRevert, constants } = require('@openzeppelin/test-helpers');
const { expect } = require('chai');

const MinimalForwarder = artifacts.require('MinimalForwarder');
const CallReceiverMock = artifacts.require('CallReceiverMock');

const name = 'MinimalForwarder';
const version = '0.0.1';
Expand Down Expand Up @@ -44,7 +45,7 @@ contract('MinimalForwarder', function (accounts) {
nonce: Number(await this.forwarder.getNonce(this.sender)),
data: '0x',
};
this.sign = ethSigUtil.signTypedMessage(
this.sign = () => ethSigUtil.signTypedMessage(
this.wallet.getPrivateKey(),
{
data: {
Expand All @@ -65,7 +66,7 @@ contract('MinimalForwarder', function (accounts) {
});

it('success', async function () {
expect(await this.forwarder.verify(this.req, this.sign)).to.be.equal(true);
expect(await this.forwarder.verify(this.req, this.sign())).to.be.equal(true);
});

afterEach(async function () {
Expand All @@ -76,27 +77,27 @@ contract('MinimalForwarder', function (accounts) {

context('invalid signature', function () {
it('tampered from', async function () {
expect(await this.forwarder.verify({ ...this.req, from: accounts[0] }, this.sign))
expect(await this.forwarder.verify({ ...this.req, from: accounts[0] }, this.sign()))
.to.be.equal(false);
});
it('tampered to', async function () {
expect(await this.forwarder.verify({ ...this.req, to: accounts[0] }, this.sign))
expect(await this.forwarder.verify({ ...this.req, to: accounts[0] }, this.sign()))
.to.be.equal(false);
});
it('tampered value', async function () {
expect(await this.forwarder.verify({ ...this.req, value: web3.utils.toWei('1') }, this.sign))
expect(await this.forwarder.verify({ ...this.req, value: web3.utils.toWei('1') }, this.sign()))
.to.be.equal(false);
});
it('tampered nonce', async function () {
expect(await this.forwarder.verify({ ...this.req, nonce: this.req.nonce + 1 }, this.sign))
expect(await this.forwarder.verify({ ...this.req, nonce: this.req.nonce + 1 }, this.sign()))
.to.be.equal(false);
});
it('tampered data', async function () {
expect(await this.forwarder.verify({ ...this.req, data: '0x1742' }, this.sign))
expect(await this.forwarder.verify({ ...this.req, data: '0x1742' }, this.sign()))
.to.be.equal(false);
});
it('tampered signature', async function () {
const tamperedsign = web3.utils.hexToBytes(this.sign);
const tamperedsign = web3.utils.hexToBytes(this.sign());
tamperedsign[42] ^= 0xff;
expect(await this.forwarder.verify(this.req, web3.utils.bytesToHex(tamperedsign)))
.to.be.equal(false);
Expand All @@ -112,7 +113,7 @@ contract('MinimalForwarder', function (accounts) {
});

it('success', async function () {
await this.forwarder.execute(this.req, this.sign); // expect to not revert
await this.forwarder.execute(this.req, this.sign()); // expect to not revert
});

afterEach(async function () {
Expand All @@ -124,43 +125,60 @@ contract('MinimalForwarder', function (accounts) {
context('invalid signature', function () {
it('tampered from', async function () {
await expectRevert(
this.forwarder.execute({ ...this.req, from: accounts[0] }, this.sign),
this.forwarder.execute({ ...this.req, from: accounts[0] }, this.sign()),
'MinimalForwarder: signature does not match request',
);
});
it('tampered to', async function () {
await expectRevert(
this.forwarder.execute({ ...this.req, to: accounts[0] }, this.sign),
this.forwarder.execute({ ...this.req, to: accounts[0] }, this.sign()),
'MinimalForwarder: signature does not match request',
);
});
it('tampered value', async function () {
await expectRevert(
this.forwarder.execute({ ...this.req, value: web3.utils.toWei('1') }, this.sign),
this.forwarder.execute({ ...this.req, value: web3.utils.toWei('1') }, this.sign()),
'MinimalForwarder: signature does not match request',
);
});
it('tampered nonce', async function () {
await expectRevert(
this.forwarder.execute({ ...this.req, nonce: this.req.nonce + 1 }, this.sign),
this.forwarder.execute({ ...this.req, nonce: this.req.nonce + 1 }, this.sign()),
'MinimalForwarder: signature does not match request',
);
});
it('tampered data', async function () {
await expectRevert(
this.forwarder.execute({ ...this.req, data: '0x1742' }, this.sign),
this.forwarder.execute({ ...this.req, data: '0x1742' }, this.sign()),
'MinimalForwarder: signature does not match request',
);
});
it('tampered signature', async function () {
const tamperedsign = web3.utils.hexToBytes(this.sign);
const tamperedsign = web3.utils.hexToBytes(this.sign());
tamperedsign[42] ^= 0xff;
await expectRevert(
this.forwarder.execute(this.req, web3.utils.bytesToHex(tamperedsign)),
'MinimalForwarder: signature does not match request',
);
});
});

it('bubble out of gas', async function () {
const receiver = await CallReceiverMock.new();
const gasAvailable = 100000;
this.req.to = receiver.address;
this.req.data = receiver.contract.methods.mockFunctionOutOfGas().encodeABI();
this.req.gas = 1000000;

await expectRevert.assertion(
this.forwarder.execute(this.req, this.sign(), { gas: gasAvailable }),
);

const { gasUsed } = await web3.eth.getBlock('latest')
.then(({ transactions }) => web3.eth.getTransactionReceipt(transactions.find(Boolean)));
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expect(gasUsed).to.be.equal(gasAvailable);
});
});
});
});