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sDOLARateProvider.md

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Rate Provider: ERC4626RateProvider

Details

Context

sDOLA is a yield-bearing stablecoin structured as an ERC-4626 wrapper around a DOLA Savings Account (DSA) contract that continuously streams DOLA Borrowing Rights rewards to staked DOLA and auto-compounds them. The Rate provider exposes the convertToAssets of sDOLA via a getRate() function and makes the rate consumable by Balancer pools.

Review Checklist: Bare Minimum Compatibility

Each of the items below represents an absolute requirement for the Rate Provider. If any of these is unchecked, the Rate Provider is unfit to use.

  • Implements the IRateProvider interface.
  • getRate returns an 18-decimal fixed point number (i.e., 1 == 1e18) regardless of underlying token decimals.

Review Checklist: Common Findings

Each of the items below represents a common red flag found in Rate Provider contracts.

If none of these is checked, then this might be a pretty great Rate Provider! If any of these is checked, we must thoroughly elaborate on the conditions that lead to the potential issue. Decision points are not binary; a Rate Provider can be safe despite these boxes being checked. A check simply indicates that thorough vetting is required in a specific area, and this vetting should be used to inform a holistic analysis of the Rate Provider.

Administrative Privileges

  • The Rate Provider is upgradeable (e.g., via a proxy architecture or an onlyOwner function that updates the price source address).

  • Some other portion of the price pipeline is upgradeable (e.g., the token itself, an oracle, or some piece of a larger system that tracks the price).

Oracles

  • Price data is provided by an off-chain source (e.g., a Chainlink oracle, a multisig, or a network of nodes).

  • Price data is expected to be volatile (e.g., because it represents an open market price instead of a (mostly) monotonically increasing price).

Common Manipulation Vectors

  • The Rate Provider is susceptible to donation attacks.

The price is dependent on evaluation of totalAssets() which also evaluates the balance of DolaSavings in the [sDOLA] contract by reading it via balanceOf().

uint actualAssets = savings.balanceOf(address(this)) - remainingLastRevenue - weeklyRevenue[week];

By sending DolaSavings to the sDOLA contract, the price can be influenced by a donation.

Additional Findings

To save time, we do not bother pointing out low-severity/informational issues or gas optimizations (unless the gas usage is particularly egregious). Instead, we focus only on high- and medium-severity findings which materially impact the contract's functionality and could harm users.

Conclusion

Summary judgment: SAFE

This Rate Provider should work well with Balancer pools. The Rate Provider and downstream contracts not being upgradeable decrease the potential attack surface and make the Rate Provider immutable.