Audit fix 94 one approve

contracts/SushiYieldSource.sol

@@ -16,7 +16,10 @@ contract SushiYieldSource is IYieldSource, ReentrancyGuard {
     using SafeERC20 for IERC20;
     using SafeMath for uint256;
 
+    /// @notice Interface of the SushiBar contract
     ISushiBar public immutable sushiBar;
+
+    /// @notice Interface for the Sushi token
     IERC20 public immutable sushiAddr;
 
     mapping(address => uint256) public balances;
@@ -52,6 +55,19 @@ contract SushiYieldSource is IYieldSource, ReentrancyGuard {
         _sushiAddr.safeApprove(address(_sushiBar), type(uint256).max);
     }
 
+    /// @notice Approve SUSHI to spend infinite sushiBar (xSUSHI)
+    /// @dev Emergency function to re-approve max amount if approval amount dropped too low
+    /// @return true if operation is successful
+    function approveMaxAmount() external returns (bool) {
+        address _sushiBarAddress = address(sushiBar);
+        IERC20 sushi = sushiAddr;
+
+        uint256 allowance = sushi.allowance(address(this), _sushiBarAddress);
+
+        sushi.safeIncreaseAllowance(_sushiBarAddress, type(uint256).max.sub(allowance));
+        return true;
+    }
+
     /// @notice Returns the ERC20 asset token used for deposits.
     /// @return The ERC20 asset token
     function depositToken() external view override returns (address) {
@@ -116,6 +132,7 @@ contract SushiYieldSource is IYieldSource, ReentrancyGuard {
         uint256 sushiBalanceDiff = sushiAfterBalance.sub(sushiBeforeBalance);
 
         balances[msg.sender] = balances[msg.sender].sub(requiredSharesBalance);
+
         sushi.safeTransfer(msg.sender, sushiBalanceDiff);
         emit RedeemedToken(msg.sender, requiredSharesBalance, amount);
 

test/unit_test.js

@@ -63,20 +63,24 @@ describe("SushiYieldSource", function () {
   });
 
   describe("constructor()", () => {
-    let randomWalletAddress;
-
     before(() => {
       isDeployTest = true;
     });
 
-    beforeEach(() => {
-      randomWalletAddress = ethers.Wallet.createRandom().address;
-    });
-
     after(() => {
       isDeployTest = false;
     });
 
+    it('should succeed to construct yield source', async () => {
+      await deploySushiYieldSource(sushiBar.address, sushi.address);
+
+      expect(await yieldSource.sushiBar()).to.equal(sushiBar.address);
+      expect(await yieldSource.sushiAddr()).to.equal(sushi.address);
+      expect(await sushi.allowance(yieldSource.address, sushiBar.address)).to.equal(
+        ethers.constants.MaxUint256,
+      );
+    });
+
     it("should fail if sushiBar address is address 0", async () => {
       await expect(
         deploySushiYieldSource(ethers.constants.AddressZero, sushi.address)
@@ -90,6 +94,13 @@ describe("SushiYieldSource", function () {
     });
   });
 
+  describe('approveMaxAmount()', () => {
+    it('should approve Sushi to spend max uint256 amount', async () => {
+      expect(await yieldSource.callStatic.approveMaxAmount()).to.eq(true);
+      expect(await sushi.allowance(yieldSource.address, sushiBar.address)).to.eq(ethers.constants.MaxUint256);
+    });
+  });
+
   it("get token address", async function () {
     let address = await yieldSource.depositToken();
     expect(address == sushi);