Acre stBTC Rate Provider

rate-providers/registry.json

@@ -1381,6 +1381,24 @@
           "implementationReviewed": "0xe2D2E90122cb203CF1565a37ef90a256843A825A"
         }
       ]
+    },
+    "0x479306411084bD75b8Ce9Dd488e64f212b8336b2": {
+      "asset": "0xdF217EFD8f3ecb5E837aedF203C28c1f06854017",
+      "name": "ERC4626RateProvider",
+      "summary": "safe",
+      "review": "./stBTCRateProvider.md",
+      "warnings": ["donation"],
+      "factory": "0xFC541f8d8c5e907E236C8931F0Df9F58e0C259Ec",
+      "upgradeableComponents": [
+        {
+          "entrypoint": "0xdF217EFD8f3ecb5E837aedF203C28c1f06854017",
+          "implementationReviewed": "0xef96b93db617f3db5b2cf2df9aa50bd7f5cb22c4"
+        },
+        {
+          "entrypoint": "0xAB13B8eecf5AA2460841d75da5d5D861fD5B8A39",
+          "implementationReviewed": "0xd7097af27b14e204564c057c636022fae346fe60"
+        }
+      ]
     }
   },
   "fantom": {

rate-providers/stBTCRateProvider.md

@@ -0,0 +1,68 @@
+# Rate Provider: `ERC4626RateProvider`
+
+## Details
+- Reviewed by: @mkflow27
+- Checked by: @danielmkm
+- Deployed at:
+    - [ethereum:0x479306411084bD75b8Ce9Dd488e64f212b8336b2](https://etherscan.io/address/0x479306411084bD75b8Ce9Dd488e64f212b8336b2#readContract)
+- Audit report(s):
+    - [Acre audits](https://acre.fi/assets/stbtc-smart-contracts-audit.pdf)
+
+## Context
+Users deposit BTC and receive stBTC representing their deposited BTC. The deposited BTC is deployed to Bitcoin layers that use BTC as their Proof-of-Stake asset, generating rewards for stBTC holders.
+
+## 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.
+
+- [x] Implements the [`IRateProvider`](https://github.com/balancer/balancer-v2-monorepo/blob/bc3b3fee6e13e01d2efe610ed8118fdb74dfc1f2/pkg/interfaces/contracts/pool-utils/IRateProvider.sol) interface.
+- [x] `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).
+
+- [x] 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).
+    - upgradeable component: `stBTC` ([ethereum:0xdF217EFD8f3ecb5E837aedF203C28c1f06854017](https://etherscan.io/address/0xdF217EFD8f3ecb5E837aedF203C28c1f06854017))
+    - admin address: [ethereum:0x790Dda4c56b3c45d0e4514eDbAaBa30D7129c857](https://etherscan.io/address/0x790Dda4c56b3c45d0e4514eDbAaBa30D7129c857#code)
+    - admin type: multisig
+        - multisig threshold/signers: 3/7
+
+
+    - upgradeable component: `Portal` ([ethereum:0xAB13B8eecf5AA2460841d75da5d5D861fD5B8A39](https://etherscan.io/address/0xAB13B8eecf5AA2460841d75da5d5D861fD5B8A39#code))
+    - admin address: [ethereum:0x98D8899c3030741925BE630C710A98B57F397C7a](https://etherscan.io/address/0x98D8899c3030741925BE630C710A98B57F397C7a#code)
+    - admin type: multisig
+        - multisig threshold/signers: 5/9
+
+    #### A note on pricing approach.
+    The price is calculated via a totalAssets / totalSupply approach. totalAssets is calculated via
+    ```solidity
+    function totalAssets() public view override returns (uint256) {
+        return
+            IERC20(asset()).balanceOf(address(this)) +
+            dispatcher.totalAssets() +
+            totalDebt;
+    }
+    ``` 
+    Where debt can be publicly minted by anyone if his `allowedDebt[msg.sender]` is not exceeded. The admin who can set this limit for any account is a 3/7 Multisig at [ethereum:0x790Dda4c56b3c45d0e4514eDbAaBa30D7129c857](https://etherscan.io/address/0x790Dda4c56b3c45d0e4514eDbAaBa30D7129c857).
+
+
+### 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
+- [x] The Rate Provider is susceptible to donation attacks. 
+    Various token balances are being read throughout the rate calculation. 
+
+## 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. A common mechanism to calculate share price is chosen (totalAssets / totalSupply) and any external contracts which influence the rate or callable functions which influence the rate are properly guarded by multisigs.