Tigris Trade contest - izhelyazkov's results

Lines of code

https://github.com/code-423n4/2022-12-tigris/blob/588c84b7bb354d20cbca6034544c4faa46e6a80e/contracts/StableVault.sol#L49

Vulnerability details

Impact

The StableVault has a deposit function, which allows a user to deposit a whitelisted token in exchange for tigAsset. If the whitelisted token has above 18 decimals, the deposit and depositWithPermit functions will revert, thus rendering any asset with > 18 decimals incompatible with the protocol.

Proof of Concept

1. Deploy a MockERC20 with 19 decimals in the deploy/00.Mocks.js script.
2. Add the following test in test/06.StableVault.js:

it("Listing and depositing a token with > 18 decimals", async function () {
      await stablevault.connect(owner).listToken(MockBigDecimal.address);
      await mockBD.connect(owner).approve(StableVault.address, 5000000);
      await (stablevault.connect(owner).deposit(MockBigDecimal.address, 100000));
    })

3. Result:

Error: VM Exception while processing transaction: reverted with panic code 0x11 (Arithmetic operation underflowed or overflowed outside of an unchecked block)

Tools Used

VS Code Plugins, Hardhat

Recommended Mitigation Steps

Explicitly add a check or a comment if the StableVault is not meant to support tokens with > 18 decimals.