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Adjust ERC2771Context._msgData for msg.data.length < 20 #4484

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Jul 27, 2023
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5 changes: 5 additions & 0 deletions .changeset/warm-guests-rule.md
Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
---
'openzeppelin-solidity': patch
---

`ERC2771Context`: Prevent revert in `_msgData()` when a call originating from a trusted forwarder is not long enough to contain the request signer address (i.e. `msg.data.length` is less than 20 bytes). Return the full calldata in that case.
2 changes: 1 addition & 1 deletion contracts/metatx/ERC2771Context.sol
Original file line number Diff line number Diff line change
Expand Up @@ -34,7 +34,7 @@ abstract contract ERC2771Context is Context {
}

function _msgData() internal view virtual override returns (bytes calldata) {
if (isTrustedForwarder(msg.sender)) {
if (isTrustedForwarder(msg.sender) && msg.data.length >= 20) {
return msg.data[:msg.data.length - 20];
} else {
return super._msgData();
Expand Down
6 changes: 6 additions & 0 deletions contracts/mocks/ContextMock.sol
Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,12 @@ contract ContextMock is Context {
function msgData(uint256 integerValue, string memory stringValue) public {
emit Data(_msgData(), integerValue, stringValue);
}

event DataShort(bytes data);

function msgDataShort() public {
emit DataShort(_msgData());
}
}

contract ContextMockCaller {
Expand Down
18 changes: 14 additions & 4 deletions test/metatx/ERC2771Context.test.js
Original file line number Diff line number Diff line change
Expand Up @@ -12,7 +12,7 @@ const ContextMockCaller = artifacts.require('ContextMockCaller');
const { shouldBehaveLikeRegularContext } = require('../utils/Context.behavior');

contract('ERC2771Context', function (accounts) {
const [, anotherAccount] = accounts;
const [, trustedForwarder] = accounts;

const MAX_UINT48 = web3.utils.toBN(1).shln(48).subn(1).toString();

Expand Down Expand Up @@ -84,11 +84,11 @@ contract('ERC2771Context', function (accounts) {

it('returns the original sender when calldata length is less than 20 bytes (address length)', async function () {
// The forwarder doesn't produce calls with calldata length less than 20 bytes
const recipient = await ERC2771ContextMock.new(anotherAccount);
const recipient = await ERC2771ContextMock.new(trustedForwarder);

const { receipt } = await recipient.msgSender({ from: anotherAccount });
const { receipt } = await recipient.msgSender({ from: trustedForwarder });

await expectEvent(receipt, 'Sender', { sender: anotherAccount });
await expectEvent(receipt, 'Sender', { sender: trustedForwarder });
});
});

Expand Down Expand Up @@ -117,5 +117,15 @@ contract('ERC2771Context', function (accounts) {
await expectEvent.inTransaction(tx, ERC2771ContextMock, 'Data', { data, integerValue, stringValue });
});
});

it('returns the full original data when calldata length is less than 20 bytes (address length)', async function () {
// The forwarder doesn't produce calls with calldata length less than 20 bytes
const recipient = await ERC2771ContextMock.new(trustedForwarder);

const { receipt } = await recipient.msgDataShort({ from: trustedForwarder });

const data = recipient.contract.methods.msgDataShort().encodeABI();
await expectEvent(receipt, 'DataShort', { data });
});
});
});