Wrong starting price when listing on Seaport for assets that has less than 18 decimals

[code423n4]

Lines of code

https://github.com/code-423n4/2023-01-astaria/blob/main/src/AstariaRouter.sol#L639-L647

Vulnerability details

Impact

According to Astaria's docs:
https://docs.astaria.xyz/docs/protocol-mechanics/loanterms

Liquidation initial ask: Should the NFT go into liquidation, the initial price of the auction will be set to this value. Note that this set as a starting point for a dutch auction, and the price will decrease over the liquidation period. This figure is should also be specified in 10^18 format.

The liquidation initial ask is specififed in 18 decimals. this is then used as a starting price when the NFT goes under auction on OpenSea. However, if the asset has less than 18 decimals, then the starting price goes wrong to Seaport.

This results in listing the NFT with too high price that makes it unlikely to be sold.

Proof of Concept

The starting price is set to the liquidation initial ask:

    listedOrder = s.COLLATERAL_TOKEN.auctionVault(
      ICollateralToken.AuctionVaultParams({
        settlementToken: stack[position].lien.token,
        collateralId: stack[position].lien.collateralId,
        maxDuration: auctionWindowMax,
        startingPrice: stack[0].lien.details.liquidationInitialAsk,
        endingPrice: 1_000 wei
      })
    );

https://github.com/code-423n4/2023-01-astaria/blob/main/src/AstariaRouter.sol#L639-L647

Let's assume the asset is USDC which has 6 decimals:

1. Stratigist signs a strategy with liquidationInitialAsk 1000e18.
2. Following the docs, this means the starting price is supposed to be 1000 USDC
3. The NFT is being liquidated.
4. 1000e18 is passed to Seaport along with asset USDC.
5. Seaport lists the NFT, and the price will be too high as1000e18 will be 1000000000000000 USDC

Tools Used

Manual analysis

Recommended Mitigation Steps

1. Either fetch the asset's decimals on-chain or add it as a part of the strategy.
2. Convert liquidationInitialAsk to the asset's decimals before passing it as a starting price.

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SantiagoGregory marked the issue as sponsor confirmed

[androolloyd]

@androolloyd

[c4-judge]

Picodes marked the issue as satisfactory