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Make ERC2771Context return original sender address if `msg.data.lengt…
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…h <= 20` (#4481)

(cherry picked from commit 28d9ac2)
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ernestognw authored and frangio committed Jul 25, 2023
1 parent d26025b commit 7ec712b
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5 changes: 5 additions & 0 deletions .changeset/unlucky-beans-obey.md
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@@ -0,0 +1,5 @@
---
'openzeppelin-solidity': patch
---

`ERC2771Context`: Return the forwarder address whenever the `msg.data` of 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), as specified by ERC-2771.
2 changes: 1 addition & 1 deletion contracts/metatx/ERC2771Context.sol
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Expand Up @@ -22,7 +22,7 @@ abstract contract ERC2771Context is Context {
}

function _msgSender() internal view virtual override returns (address sender) {
if (isTrustedForwarder(msg.sender)) {
if (isTrustedForwarder(msg.sender) && msg.data.length >= 20) {
// The assembly code is more direct than the Solidity version using `abi.decode`.
/// @solidity memory-safe-assembly
assembly {
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11 changes: 11 additions & 0 deletions test/metatx/ERC2771Context.test.js
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Expand Up @@ -12,6 +12,8 @@ const ContextMockCaller = artifacts.require('ContextMockCaller');
const { shouldBehaveLikeRegularContext } = require('../utils/Context.behavior');

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

beforeEach(async function () {
this.forwarder = await MinimalForwarder.new();
this.recipient = await ERC2771ContextMock.new(this.forwarder.address);
Expand Down Expand Up @@ -73,6 +75,15 @@ contract('ERC2771Context', function (accounts) {
const { tx } = await this.forwarder.execute(req, sign);
await expectEvent.inTransaction(tx, ERC2771ContextMock, 'Sender', { sender: this.sender });
});

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

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

describe('msgData', function () {
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