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Merge GSNContext into GSNRecipient (#1906)

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* Merge GSNContext into GSNRecipient

* Update GSNRecipient.test.js

* Update GSNRecipient.sol

* Make GSNRecipient inherit from Context

(cherry picked from commit 1efa9f6281)
This commit is contained in:
Nicolás Venturo
2019-08-30 17:18:42 -03:00
committed by Francisco Giordano
parent 5f1d8e19da
commit dba4d5023d
6 changed files with 184 additions and 224 deletions
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88
contracts/GSN/GSNContext.sol
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@ -1,88 +0,0 @@
pragma solidity ^0.5.0;
import "./Context.sol";
/**
* @dev Enables GSN support on `Context` contracts by recognizing calls from
* RelayHub and extracting the actual sender and call data from the received
* calldata.
*
* > This contract does not perform all required tasks to implement a GSN
* recipient contract: end users should use `GSNRecipient` instead.
*/
contract GSNContext is Context {
address internal _relayHub = 0xD216153c06E857cD7f72665E0aF1d7D82172F494;
event RelayHubChanged(address indexed oldRelayHub, address indexed newRelayHub);
constructor() internal {
// solhint-disable-previous-line no-empty-blocks
}
function _upgradeRelayHub(address newRelayHub) internal {
address currentRelayHub = _relayHub;
require(newRelayHub != address(0), "GSNContext: new RelayHub is the zero address");
require(newRelayHub != currentRelayHub, "GSNContext: new RelayHub is the current one");
emit RelayHubChanged(currentRelayHub, newRelayHub);
_relayHub = newRelayHub;
}
// Overrides for Context's functions: when called from RelayHub, sender and
// data require some pre-processing: the actual sender is stored at the end
// of the call data, which in turns means it needs to be removed from it
// when handling said data.
function _msgSender() internal view returns (address) {
if (msg.sender != _relayHub) {
return msg.sender;
} else {
return _getRelayedCallSender();
}
}
function _msgData() internal view returns (bytes memory) {
if (msg.sender != _relayHub) {
return msg.data;
} else {
return _getRelayedCallData();
}
}
function _getRelayedCallSender() private pure returns (address result) {
// We need to read 20 bytes (an address) located at array index msg.data.length - 20. In memory, the array
// is prefixed with a 32-byte length value, so we first add 32 to get the memory read index. However, doing
// so would leave the address in the upper 20 bytes of the 32-byte word, which is inconvenient and would
// require bit shifting. We therefore subtract 12 from the read index so the address lands on the lower 20
// bytes. This can always be done due to the 32-byte prefix.
// The final memory read index is msg.data.length - 20 + 32 - 12 = msg.data.length. Using inline assembly is the
// easiest/most-efficient way to perform this operation.
// These fields are not accessible from assembly
bytes memory array = msg.data;
uint256 index = msg.data.length;
// solhint-disable-next-line no-inline-assembly
assembly {
// Load the 32 bytes word from memory with the address on the lower 20 bytes, and mask those.
result := and(mload(add(array, index)), 0xffffffffffffffffffffffffffffffffffffffff)
}
return result;
}
function _getRelayedCallData() private pure returns (bytes memory) {
// RelayHub appends the sender address at the end of the calldata, so in order to retrieve the actual msg.data,
// we must strip the last 20 bytes (length of an address type) from it.
uint256 actualDataLength = msg.data.length - 20;
bytes memory actualData = new bytes(actualDataLength);
for (uint256 i = 0; i < actualDataLength; ++i) {
actualData[i] = msg.data[i];
}
return actualData;
}
}

105
contracts/GSN/GSNRecipient.sol
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@ -1,9 +1,9 @@
pragma solidity ^0.5.0;
import "./IRelayRecipient.sol";
import "./GSNContext.sol";
import "./bouncers/GSNBouncerBase.sol";
import "./IRelayHub.sol";
import "./Context.sol";
import "./bouncers/GSNBouncerBase.sol";
/**
* @dev Base GSN recipient contract: includes the {IRelayRecipient} interface and enables GSN support on all contracts
@ -11,16 +11,42 @@ import "./IRelayHub.sol";
*
* Not all interface methods are implemented (e.g. {acceptRelayedCall}, derived contracts must provide one themselves.
*/
contract GSNRecipient is IRelayRecipient, GSNContext, GSNBouncerBase {
contract GSNRecipient is IRelayRecipient, Context, GSNBouncerBase {
// Default RelayHub address, deployed on mainnet and all testnets at the same address
address private _relayHub = 0xD216153c06E857cD7f72665E0aF1d7D82172F494;
/**
* @dev Returns the `RelayHub` address for this recipient contract.
* @dev Emitted when a contract changes its {IRelayHub} contract to a new one.
*/
event RelayHubChanged(address indexed oldRelayHub, address indexed newRelayHub);
/**
* @dev Returns the address of the {IRelayHub} contract for this recipient.
*/
function getHubAddr() public view returns (address) {
return _relayHub;
}
/**
* @dev Returns the version string of the `RelayHub` for which this recipient implementation was built.
* @dev Switches to a new {IRelayHub} instance. This method is added for future-proofing: there's no reason to not
* use the default instance.
*
* IMPORTANT: After upgrading, the {GSNRecipient} will no longer be able to receive relayed calls from the old
* {IRelayHub} instance. Additionally, all funds should be previously withdrawn via {_withdrawDeposits}.
*/
function _upgradeRelayHub(address newRelayHub) internal {
address currentRelayHub = _relayHub;
require(newRelayHub != address(0), "GSNRecipient: new RelayHub is the zero address");
require(newRelayHub != currentRelayHub, "GSNRecipient: new RelayHub is the current one");
emit RelayHubChanged(currentRelayHub, newRelayHub);
_relayHub = newRelayHub;
}
/**
* @dev Returns the version string of the {IRelayHub} for which this recipient implementation was built. If
* {_upgradeRelayHub} is used, the new {IRelayHub} instance should be compatible with this version.
*/
// This function is view for future-proofing, it may require reading from
// storage in the future.
@ -37,4 +63,73 @@ contract GSNRecipient is IRelayRecipient, GSNContext, GSNBouncerBase {
function _withdrawDeposits(uint256 amount, address payable payee) internal {
IRelayHub(_relayHub).withdraw(amount, payee);
}
// Overrides for Context's functions: when called from RelayHub, sender and
// data require some pre-processing: the actual sender is stored at the end
// of the call data, which in turns means it needs to be removed from it
// when handling said data.
/**
* @dev Replacement for msg.sender. Returns the actual sender of a transaction: msg.sender for regular transactions,
* and the end-user for GSN relayed calls (where msg.sender is actually `RelayHub`).
*
* IMPORTANT: Contracts derived from {GSNRecipient} should never use `msg.sender`, and use {_msgSender} instead.
*/
function _msgSender() internal view returns (address) {
if (msg.sender != _relayHub) {
return msg.sender;
} else {
return _getRelayedCallSender();
}
}
/**
* @dev Replacement for msg.data. Returns the actual calldata of a transaction: msg.data for regular transactions,
* and a reduced version for GSN relayed calls (where msg.data contains additional information).
*
* IMPORTANT: Contracts derived from {GSNRecipient} should never use `msg.data`, and use {_msgData} instead.
*/
function _msgData() internal view returns (bytes memory) {
if (msg.sender != _relayHub) {
return msg.data;
} else {
return _getRelayedCallData();
}
}
function _getRelayedCallSender() private pure returns (address result) {
// We need to read 20 bytes (an address) located at array index msg.data.length - 20. In memory, the array
// is prefixed with a 32-byte length value, so we first add 32 to get the memory read index. However, doing
// so would leave the address in the upper 20 bytes of the 32-byte word, which is inconvenient and would
// require bit shifting. We therefore subtract 12 from the read index so the address lands on the lower 20
// bytes. This can always be done due to the 32-byte prefix.
// The final memory read index is msg.data.length - 20 + 32 - 12 = msg.data.length. Using inline assembly is the
// easiest/most-efficient way to perform this operation.
// These fields are not accessible from assembly
bytes memory array = msg.data;
uint256 index = msg.data.length;
// solhint-disable-next-line no-inline-assembly
assembly {
// Load the 32 bytes word from memory with the address on the lower 20 bytes, and mask those.
result := and(mload(add(array, index)), 0xffffffffffffffffffffffffffffffffffffffff)
}
return result;
}
function _getRelayedCallData() private pure returns (bytes memory) {
// RelayHub appends the sender address at the end of the calldata, so in order to retrieve the actual msg.data,
// we must strip the last 20 bytes (length of an address type) from it.
uint256 actualDataLength = msg.data.length - 20;
bytes memory actualData = new bytes(actualDataLength);
for (uint256 i = 0; i < actualDataLength; ++i) {
actualData[i] = msg.data[i];
}
return actualData;
}
}

46
contracts/mocks/GSNContextMock.sol
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@ -1,46 +0,0 @@
pragma solidity ^0.5.0;
import "./ContextMock.sol";
import "../GSN/GSNContext.sol";
import "../GSN/IRelayRecipient.sol";
// By inheriting from GSNContext, Context's internal functions are overridden automatically
contract GSNContextMock is ContextMock, GSNContext, IRelayRecipient {
function getHubAddr() public view returns (address) {
return _relayHub;
}
function acceptRelayedCall(
address,
address,
bytes calldata,
uint256,
uint256,
uint256,
uint256,
bytes calldata,
uint256
)
external
view
returns (uint256, bytes memory)
{
return (0, "");
}
function preRelayedCall(bytes calldata) external returns (bytes32) {
// solhint-disable-previous-line no-empty-blocks
}
function postRelayedCall(bytes calldata, bool, uint256, bytes32) external {
// solhint-disable-previous-line no-empty-blocks
}
function getRelayHub() public view returns (address) {
return _relayHub;
}
function upgradeRelayHub(address newRelayHub) public {
return _upgradeRelayHub(newRelayHub);
}
}

8
contracts/mocks/GSNRecipientMock.sol
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@ -1,8 +1,10 @@
pragma solidity ^0.5.0;
import "./ContextMock.sol";
import "../GSN/GSNRecipient.sol";
contract GSNRecipientMock is GSNRecipient {
// By inheriting from GSNRecipient, Context's internal functions are overridden automatically
contract GSNRecipientMock is ContextMock, GSNRecipient {
function withdrawDeposits(uint256 amount, address payable payee) public {
_withdrawDeposits(amount, payee);
}
@ -22,4 +24,8 @@ contract GSNRecipientMock is GSNRecipient {
function postRelayedCall(bytes calldata, bool, uint256, bytes32) external {
// solhint-disable-previous-line no-empty-blocks
}
function upgradeRelayHub(address newRelayHub) public {
return _upgradeRelayHub(newRelayHub);
}
}