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Use Case

An oracle is a mechanism used to fetch data from an external source and use it to make decisions within a protocol. Make sure that an oracle is working as expected. Manipulation of oracles is a very common attack vector. An oracle can be manipulated to return a price that is not representative of the true price of an asset. Oracles are used in many DeFi protocols, including lending protocols, derivatives protocols, and more.

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Explanation

This assertion makes sure that the oracle has been updated within the last 10 minutes and that the price doesn’t deviate more than 10% from the pre-state price. There are two triggers, one for the liveness of the oracle and one for the price.

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Code Example

// SPDX-License-Identifier: MIT
pragma solidity 0.8.28;

import {Assertion} from "../lib/credible-std/Assertion.sol";

interface IOracle {
    function lastUpdated() external view returns (uint256);
    function price() external view returns (uint256);
}

// Checks that the oracle is live
contract OracleLivenessAssertion is Assertion {
    IOracle public oracle = IOracle(address(0xbeef));

    function fnSelectors() external pure override returns (Trigger[] memory) {
        Trigger[] memory triggers = new Trigger[](2); // Define the number of triggers
        triggers[0] = Trigger(TriggerType.STORAGE, this.assertionOracleLiveness.selector); // Define the trigger
        triggers[1] = Trigger(TriggerType.STORAGE, this.assertionOraclePrice.selector); // Define the trigger
        return triggers;
    }

    // Make sure that the oracle has been updated within the last 10 minutes
    // return true indicates a valid state
    // return false indicates an invalid state
    function assertionOracleLiveness() external returns (bool) {
        ph.forkPreState();
        uint256 preTimestamp = oracle.lastUpdated();
        ph.forkPostState();
        uint256 postTimestamp = oracle.lastUpdated();
        return postTimestamp - preTimestamp <= 10 minutes; // Could be whatever time frame your protocol requires
    }

    // Make sure that price doesn't deviate more than 10%
    // return true indicates a valid state
    // return false indicates an invalid state
    function assertionOraclePrice() external returns (bool) {
        ph.forkPreState();
        uint256 prePrice = oracle.price();
        ph.forkPostState();
        uint256 postPrice = oracle.price();
        uint256 deviation = (((postPrice > prePrice) ? postPrice - prePrice : prePrice - postPrice) * 100) / prePrice;
        return deviation <= 10; // Could be whatever deviation your protocol requires
    }
}
Timelock VerificationTWAP Deviation