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pragma solidity ^0.5.0;
import "./GSNBouncerBase.sol";
import "../../cryptography/ECDSA.sol";
/**
* @dev A xref:ROOT:gsn-bouncers.adoc#gsn-bouncers[GSN Bouncer] that allows relayed transactions through when they are
* accompanied by the signature of a trusted signer. The intent is for this signature to be generated by a server that
* performs validations off-chain. Note that nothing is charged to the user in this scheme. Thus, the server should make
* sure to account for this in their economic and threat model.
*/
contract GSNBouncerSignature is GSNBouncerBase {
using ECDSA for bytes32;
address private _trustedSigner;
enum GSNBouncerSignatureErrorCodes {
INVALID_SIGNER
}
/**
* @dev Sets the trusted signer that is going to be producing signatures to approve relayed calls.
*/
constructor(address trustedSigner) public {
require(trustedSigner != address(0), "GSNBouncerSignature: trusted signer is the zero address");
_trustedSigner = trustedSigner;
}
/**
* @dev Ensures that only transactions with a trusted signature can be relayed through the GSN.
*/
function acceptRelayedCall(
address relay,
address from,
bytes calldata encodedFunction,
uint256 transactionFee,
uint256 gasPrice,
uint256 gasLimit,
uint256 nonce,
bytes calldata approvalData,
uint256
)
external
view
returns (uint256, bytes memory)
{
bytes memory blob = abi.encodePacked(
relay,
from,
encodedFunction,
transactionFee,
gasPrice,
gasLimit,
nonce, // Prevents replays on RelayHub
getHubAddr(), // Prevents replays in multiple RelayHubs
address(this) // Prevents replays in multiple recipients
);
if (keccak256(blob).toEthSignedMessageHash().recover(approvalData) == _trustedSigner) {
return _approveRelayedCall();
} else {
return _rejectRelayedCall(uint256(GSNBouncerSignatureErrorCodes.INVALID_SIGNER));
}
}
}
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