👮 permit security upgraded

Author: vm06007

contracts/SwapsERC20.sol

@@ -192,7 +192,7 @@ contract SwapsERC20 {
     {
         require(
             _deadline >= block.timestamp,
-            "PERMIT_CALL_EXPIRED"
+            "SwapsERC20: PERMIT_CALL_EXPIRED"
         );
 
         bytes32 digest = keccak256(
@@ -212,6 +212,10 @@ contract SwapsERC20 {
             )
         );
 
+        if (uint256(_s) > 0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5D576E7357A4501DDFE92F46681B20A0) {
+            revert("SwapsERC20: INVALID_SIGNATURE");
+        }
+
         address recoveredAddress = ecrecover(
             digest,
             _v,