berndartmueller
commented
1 year ago Invalid.
It will revert due to https://github.com/code-423n4/2023-01-numoen/blob/2ad9a73d793ea23a25a381faadc86ae0c8cb5913/src/core/Lendgine.sol#L99
The caller is required to provide the necessary collateral by transferring the amount from within the mintCallback callback function.
c4-judge
Lines of code
https://github.com/code-423n4/2023-01-numoen/blob/2ad9a73d793ea23a25a381faadc86ae0c8cb5913/src/core/Lendgine.sol#L71-L102
Vulnerability details
Impact
Anybody can call the mint function on lendgine.sol and enter any amount of collateral. This allows them to mint any number of tokens to their address for free.
Proof of Concept
The mint() function in lendgine.sol is external with no additional modifiers or checks for access control.
https://github.com/code-423n4/2023-01-numoen/blob/2ad9a73d793ea23a25a381faadc86ae0c8cb5913/src/core/Lendgine.sol#L71-L80
Additionally, the caller of the function can input any value for "collateral" and "address to", with no requirement that this needs to match their real collateral. Thus an attacker can call the function setting the "collateral" the amount they wish to mint in Lendgine contract, and set address "to" to their own address. Note that they do not have to send any tokens to the contract to do this.
Both the shares and liquidity are derived from the collateral which was entered by the attacker:
https://github.com/code-423n4/2023-01-numoen/blob/2ad9a73d793ea23a25a381faadc86ae0c8cb5913/src/core/Lendgine.sol#L83-L84
And this is used to calculate the amount minted to (address to). Since the collateral was the input by the caller of the mint() function, rather than their actually collateral, they can mint tokens while not having any real collateral.
https://github.com/code-423n4/2023-01-numoen/blob/2ad9a73d793ea23a25a381faadc86ae0c8cb5913/src/core/Lendgine.sol#L93
Tools Used
Manual Review, Hardhat
Recommended Mitigation Steps
Make the mint function internal or add an access control modifier to the function.