feat: Add index input validation (SC-960) (#34)

* feat: add index input validation

* feat: update to add testing

* ifx: update to use n coins

Author: lucas-manuel

src/MainnetController.sol

@@ -562,11 +562,19 @@ contract MainnetController is AccessControl {
     {
         _checkRole(RELAYER);
 
+        require(inputIndex != outputIndex, "MainnetController/invalid-indices");
+
         uint256 maxSlippage = maxSlippages[pool];
         require(maxSlippage != 0, "MainnetController/max-slippage-not-set");
 
         ICurvePoolLike curvePool = ICurvePoolLike(pool);
 
+        uint256 numCoins = curvePool.N_COINS();
+        require(
+            inputIndex < numCoins && outputIndex < numCoins,
+            "MainnetController/index-too-high"
+        );
+
         // Normalized to provide 36 decimal precision when multiplied by asset amount
         uint256[] memory rates = curvePool.stored_rates();
 
@@ -599,8 +607,8 @@ contract MainnetController is AccessControl {
                 abi.encodeCall(
                     curvePool.exchange,
                     (
-                        int128(int256(inputIndex)),   // Assuming safe cast because of 8 token max
-                        int128(int256(outputIndex)),  // Assuming safe cast because of 8 token max
+                        int128(int256(inputIndex)),   // safe cast because of 8 token max
+                        int128(int256(outputIndex)),  // safe cast because of 8 token max
                         amountIn,
                         minAmountOut,
                         address(proxy)

test/mainnet-fork/Curve.t.sol

@@ -550,6 +550,40 @@ contract MainnetControllerSwapCurveFailureTests is CurveTestBase {
         mainnetController.swapCurve(CURVE_POOL, 1, 0, 1_000_000e18, 980_000e6);
     }
 
+    function test_swapCurve_sameIndex() public {
+        vm.prank(relayer);
+        vm.expectRevert("MainnetController/invalid-indices");
+        mainnetController.swapCurve(CURVE_POOL, 1, 1, 1_000_000e18, 980_000e6);
+    }
+
+    function test_swapCurve_firstIndexTooHighBoundary() public {
+        _addLiquidity();
+        skip(1 days);  // Recharge swap rate limit from deposit
+
+        deal(RLUSD, address(almProxy), 1_000_000e18);
+
+        vm.prank(relayer);
+        vm.expectRevert("MainnetController/index-too-high");
+        mainnetController.swapCurve(CURVE_POOL, 2, 0, 1_000_000e18, 980_000e6);
+
+        vm.prank(relayer);
+        mainnetController.swapCurve(CURVE_POOL, 1, 0, 1_000_000e18, 980_000e6);
+    }
+
+    function test_swapCurve_secondIndexTooHighBoundary() public {
+        _addLiquidity();
+        skip(1 days);  // Recharge swap rate limit from deposit
+
+        deal(address(usdc), address(almProxy), 1_000_000e6);
+
+        vm.prank(relayer);
+        vm.expectRevert("MainnetController/index-too-high");
+        mainnetController.swapCurve(CURVE_POOL, 0, 2, 1_000_000e6, 980_000e18);
+
+        vm.prank(relayer);
+        mainnetController.swapCurve(CURVE_POOL, 0, 1, 1_000_000e6, 980_000e18);
+    }
+
     function test_swapCurve_slippageNotSet() public {
         vm.prank(SPARK_PROXY);
         mainnetController.setMaxSlippage(CURVE_POOL, 0);