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code-423n4 / 2021-11-badgerzaps-findings

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Zap contract's redeem() function doesn't check which token the user wants to receive #2

Open code423n4 opened 2 years ago

code423n4 commented 2 years ago

Handle

Ruhum

Vulnerability details

Impact

In the redeem() function, the user can pass a token address. That's the token they receive in return for the ibbtc they give back. Because of missing address checks the user can provide any possible ERC20 token here without the function reverting.

Although it's not strictly specified in the code I expect that the user should only be able to redeem wBTC or renBTC tokens since they should also only be able to deposit those.

Proof of Concept

https://github.com/Badger-Finance/ibbtc/blob/d8b95e8d145eb196ba20033267a9ba43a17be02c/contracts/Zap.sol#L216-L238

Tools Used

Manual Analysis

Recommended Mitigation Steps

Verify that the passed token address is either wBTC or renbtc

tabshaikh commented 2 years ago

best practice to add wBTC or renbtc in require, disagree on the severity

GalloDaSballo commented 2 years ago

Agree with the finding since only user can rekt themselves I believe this to be a medium severity finding we'll mitigate by adding a slippage check at the end of the function