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Price feeds for WETH deployment + Bulker changes for OZ audit (#625)
This PR implements and modifies price feeds to support the upcoming WETH deployment. The favored plan so far is to use ETH-denominated price feeds as opposed to USD price feeds, but stick with using 8 decimals for prices to avoid having to change the `Comet` and `Configurator` implementations. This would require: - A new wrapper price feed (`ScalingPriceFeed.sol`) that scales prices up or down to 8 decimals - A new `ConstantPriceFeed` that always returns 1e8 for the `WETH` base asset, since should always hold a 1:1 value with ETH - Modifications to the `WstETHPriceFeed` to return prices in terms of ETH instead of USD This is an alternative approach to #626, which is a more complex change but could be a better long-term solution. *Note: This PR also now contains the changes from #634 and #635, which address some suggestions made by OZ for their audit of `WstETHPriceFeed` and `Bulker`.*
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,45 @@ | ||
| // SPDX-License-Identifier: BUSL-1.1 | ||
| pragma solidity 0.8.15; | ||
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| import "./IPriceFeed.sol"; | ||
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| contract ConstantPriceFeed is IPriceFeed { | ||
| /// @notice Version of the price feed | ||
| uint public constant override version = 1; | ||
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| /// @notice Description of the price feed | ||
| string public constant description = "Constant price feed"; | ||
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| /// @notice Number of decimals for returned prices | ||
| uint8 public immutable override decimals; | ||
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| /// @notice The constant price | ||
| int public immutable constantPrice; | ||
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| /** | ||
| * @notice Construct a new scaling price feed | ||
| * @param decimals_ The number of decimals for the returned prices | ||
| **/ | ||
| constructor(uint8 decimals_, int256 constantPrice_) { | ||
| decimals = decimals_; | ||
| constantPrice = constantPrice_; | ||
| } | ||
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| /** | ||
| * @notice Price for the latest round | ||
| * @return roundId Round id from the underlying price feed | ||
| * @return answer Latest price for the asset (will always be a constant price) | ||
| * @return startedAt Timestamp when the round was started; passed on from underlying price feed | ||
| * @return updatedAt Timestamp when the round was last updated; passed on from underlying price feed | ||
| * @return answeredInRound Round id in which the answer was computed; passed on from underlying price feed | ||
| **/ | ||
| function latestRoundData() external view returns ( | ||
| uint80 roundId, | ||
| int256 answer, | ||
| uint256 startedAt, | ||
| uint256 updatedAt, | ||
| uint80 answeredInRound | ||
| ) { | ||
| return (0, constantPrice, block.timestamp, block.timestamp, 0); | ||
| } | ||
| } |
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| @@ -0,0 +1,14 @@ | ||
| // SPDX-License-Identifier: BUSL-1.1 | ||
| pragma solidity 0.8.15; | ||
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| /** | ||
| * @title IERC20NonStandard | ||
| * @dev Version of ERC20 with no return values for `transfer` and `transferFrom` | ||
| * See https://medium.com/coinmonks/missing-return-value-bug-at-least-130-tokens-affected-d67bf08521ca | ||
| */ | ||
| interface IERC20NonStandard { | ||
| function approve(address spender, uint256 amount) external; | ||
| function transfer(address to, uint256 value) external; | ||
| function transferFrom(address from, address to, uint256 value) external; | ||
| function balanceOf(address account) external view returns (uint256); | ||
| } |
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,25 @@ | ||
| // SPDX-License-Identifier: BUSL-1.1 | ||
| pragma solidity 0.8.15; | ||
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| /** | ||
| * @dev Interface for price feeds used by Comet | ||
| * Note This is Chainlink's AggregatorV3Interface, but without the `getRoundData` function. | ||
| */ | ||
| interface IPriceFeed { | ||
| function decimals() external view returns (uint8); | ||
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| function description() external view returns (string memory); | ||
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| function version() external view returns (uint256); | ||
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| function latestRoundData() | ||
| external | ||
| view | ||
| returns ( | ||
| uint80 roundId, | ||
| int256 answer, | ||
| uint256 startedAt, | ||
| uint256 updatedAt, | ||
| uint80 answeredInRound | ||
| ); | ||
| } |
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,81 @@ | ||
| // SPDX-License-Identifier: BUSL-1.1 | ||
| pragma solidity 0.8.15; | ||
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| import "./vendor/@chainlink/contracts/src/v0.8/interfaces/AggregatorV3Interface.sol"; | ||
| import "./IPriceFeed.sol"; | ||
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| contract ScalingPriceFeed is IPriceFeed { | ||
| /** Custom errors **/ | ||
| error InvalidInt256(); | ||
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| /// @notice Version of the price feed | ||
| uint public constant override version = 1; | ||
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| /// @notice Description of the price feed | ||
| string public description; | ||
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| /// @notice Number of decimals for returned prices | ||
| uint8 public immutable override decimals; | ||
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| /// @notice Underlying Chainlink price feed where prices are fetched from | ||
| address public immutable underlyingPriceFeed; | ||
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| /// @notice Whether or not the price should be upscaled | ||
| bool internal immutable shouldUpscale; | ||
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| /// @notice The amount to upscale or downscale the price by | ||
| int256 internal immutable rescaleFactor; | ||
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| /** | ||
| * @notice Construct a new scaling price feed | ||
| * @param underlyingPriceFeed_ The address of the underlying price feed to fetch prices from | ||
| * @param decimals_ The number of decimals for the returned prices | ||
| **/ | ||
| constructor(address underlyingPriceFeed_, uint8 decimals_) { | ||
| underlyingPriceFeed = underlyingPriceFeed_; | ||
| decimals = decimals_; | ||
| description = AggregatorV3Interface(underlyingPriceFeed_).description(); | ||
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| uint8 chainlinkPriceFeedDecimals = AggregatorV3Interface(underlyingPriceFeed_).decimals(); | ||
| // Note: Solidity does not allow setting immutables in if/else statements | ||
| shouldUpscale = chainlinkPriceFeedDecimals < decimals_ ? true : false; | ||
| rescaleFactor = (shouldUpscale | ||
| ? signed256(10 ** (decimals_ - chainlinkPriceFeedDecimals)) | ||
| : signed256(10 ** (chainlinkPriceFeedDecimals - decimals_)) | ||
| ); | ||
| } | ||
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| /** | ||
| * @notice Price for the latest round | ||
| * @return roundId Round id from the underlying price feed | ||
| * @return answer Latest price for the asset in terms of ETH | ||
| * @return startedAt Timestamp when the round was started; passed on from underlying price feed | ||
| * @return updatedAt Timestamp when the round was last updated; passed on from underlying price feed | ||
| * @return answeredInRound Round id in which the answer was computed; passed on from underlying price feed | ||
| **/ | ||
| function latestRoundData() override external view returns ( | ||
| uint80 roundId, | ||
| int256 answer, | ||
| uint256 startedAt, | ||
| uint256 updatedAt, | ||
| uint80 answeredInRound | ||
| ) { | ||
| (uint80 roundId_, int256 price, uint256 startedAt_, uint256 updatedAt_, uint80 answeredInRound_) = AggregatorV3Interface(underlyingPriceFeed).latestRoundData(); | ||
| return (roundId_, scalePrice(price), startedAt_, updatedAt_, answeredInRound_); | ||
| } | ||
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| function signed256(uint256 n) internal pure returns (int256) { | ||
| if (n > uint256(type(int256).max)) revert InvalidInt256(); | ||
| return int256(n); | ||
| } | ||
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| function scalePrice(int256 price) internal view returns (int256) { | ||
| int256 scaledPrice; | ||
| if (shouldUpscale) { | ||
| scaledPrice = price * rescaleFactor; | ||
| } else { | ||
| scaledPrice = price / rescaleFactor; | ||
| } | ||
| return scaledPrice; | ||
| } | ||
| } |
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