Onchain Data Verification

Verify reports onchain

To verify data onchain, Streams Direct requires several interfaces.

The primary onchain interaction occurs between the IVerifierProxy interface and your protocol's client contract. Find the Verifier proxy address for each feed on the Data Streams Feed IDs page.

Interfaces

• IVerifierProxy
• IFeeManager

In the current code example for verifying reports onchain using Streams Direct, these interfaces are specified in the example itself. Imports for these interfaces will be available in the future.

Contract example to verify report data onchain

This contract example allows you to verify reports and pay the verification fee in LINK tokens. Your contract must have sufficient LINK tokens to pay for the verification fee. Learn how to fund your contract with LINK tokens.

// SPDX-License-Identifier: MIT

pragma solidity 0.8.19;

import {Common} from "@chainlink/contracts/src/v0.8/llo-feeds/libraries/Common.sol";
import {IRewardManager} from "@chainlink/contracts/src/v0.8/llo-feeds/interfaces/IRewardManager.sol";
import {IVerifierFeeManager} from "@chainlink/contracts/src/v0.8/llo-feeds/interfaces/IVerifierFeeManager.sol";
import {IERC20} from "@chainlink/contracts-ccip/src/v0.8/vendor/openzeppelin-solidity/v4.8.3/contracts/token/ERC20/IERC20.sol";
import {SafeERC20} from "@chainlink/contracts-ccip/src/v0.8/vendor/openzeppelin-solidity/v4.8.3/contracts/token/ERC20/utils/SafeERC20.sol";

using SafeERC20 for IERC20;

/**
 * THIS IS AN EXAMPLE CONTRACT THAT USES UN-AUDITED CODE FOR DEMONSTRATION PURPOSES.
 * DO NOT USE THIS CODE IN PRODUCTION.
 */

// Custom interfaces for IVerifierProxy and IFeeManager
interface IVerifierProxy {
    /**
     * @notice Verifies that the data encoded has been signed.
     * correctly by routing to the correct verifier, and bills the user if applicable.
     * @param payload The encoded data to be verified, including the signed
     * report.
     * @param parameterPayload Fee metadata for billing. In the current implementation,
     * this consists of the abi-encoded address of the ERC-20 token used for fees.
     * @return verifierResponse The encoded report from the verifier.
     */
    function verify(
        bytes calldata payload,
        bytes calldata parameterPayload
    ) external payable returns (bytes memory verifierResponse);

    /**
     * @notice Verifies multiple reports in bulk, ensuring that each is signed correctly,
     * routes them to the appropriate verifier, and handles billing for the verification process.
     * @param payloads An array of encoded data to be verified, where each entry includes
     * the signed report.
     * @param parameterPayload Fee metadata for billing. In the current implementation,
     * this consists of the abi-encoded address of the ERC-20 token used for fees.
     * @return verifiedReports An array of encoded reports returned from the verifier.
     */
    function verifyBulk(
        bytes[] calldata payloads,
        bytes calldata parameterPayload
    ) external payable returns (bytes[] memory verifiedReports);

    function s_feeManager() external view returns (IVerifierFeeManager);
}

interface IFeeManager {
    /**
     * @notice Calculates the fee and reward associated with verifying a report, including discounts for subscribers.
     * This function assesses the fee and reward for report verification, applying a discount for recognized subscriber addresses.
     * @param subscriber The address attempting to verify the report. A discount is applied if this address
     * is recognized as a subscriber.
     * @param unverifiedReport The report data awaiting verification. The content of this report is used to
     * determine the base fee and reward, before considering subscriber discounts.
     * @param quoteAddress The payment token address used for quoting fees and rewards.
     * @return fee The fee assessed for verifying the report, with subscriber discounts applied where applicable.
     * @return reward The reward allocated to the caller for successfully verifying the report.
     * @return totalDiscount The total discount amount deducted from the fee for subscribers.
     */
    function getFeeAndReward(
        address subscriber,
        bytes memory unverifiedReport,
        address quoteAddress
    ) external returns (Common.Asset memory, Common.Asset memory, uint256);

    function i_linkAddress() external view returns (address);

    function i_nativeAddress() external view returns (address);

    function i_rewardManager() external view returns (address);
}

/**
 * @dev This contract implements functionality to verify Data Streams reports from
 * the Streams Direct API or WebSocket connection, with payment in LINK tokens.
 */
contract ClientReportsVerifier {
    error NothingToWithdraw(); // Thrown when a withdrawal attempt is made but the contract holds no tokens of the specified type.
    error NotOwner(address caller); // Thrown when a caller tries to execute a function that is restricted to the contract's owner.

    /**
     * @dev Represents a data report from a Data Streams feed.
     * The `price`, `bid`, and `ask` values are carried to either 8 or 18 decimal places, depending on the feed.
     * For more information, see https://docs.chain.link/data-streams/stream-ids.
     */
    struct Report {
        bytes32 feedId; // The feed ID the report has data for
        uint32 validFromTimestamp; // Earliest timestamp for which price is applicable
        uint32 observationsTimestamp; // Latest timestamp for which price is applicable
        uint192 nativeFee; // Base cost to validate a transaction using the report, denominated in the chain’s native token (WETH/ETH)
        uint192 linkFee; // Base cost to validate a transaction using the report, denominated in LINK
        uint32 expiresAt; // Latest timestamp where the report can be verified onchain
        int192 price; // DON consensus median price (8 or 18 decimals)
        int192 bid; // Simulated price impact of a buy order up to the X% depth of liquidity utilisation (8 or 18 decimals)
        int192 ask; // Simulated price impact of a sell order up to the X% depth of liquidity utilisation (8 or 18 decimals)
    }

    IVerifierProxy public s_verifierProxy;

    address private s_owner;
    int192 public last_decoded_price;

    event DecodedPrice(int192);

    /**
     * @param _verifierProxy The address of the VerifierProxy contract.
     * You can find these addresses on https://docs.chain.link/data-streams/stream-ids
     */
    constructor(address _verifierProxy) {
        s_owner = msg.sender;
        s_verifierProxy = IVerifierProxy(_verifierProxy);
    }

    /// @notice Checks if the caller is the owner of the contract.
    modifier onlyOwner() {
        if (msg.sender != s_owner) revert NotOwner(msg.sender);
        _;
    }

    /**
     * @notice Verifies a report and handles fee payment.
     * @dev Decodes the unverified report, calculates fees, approves token spending, and verifies the report.
     * Emits a DecodedPrice event upon successful verification and stores the price from the report in `last_decoded_price`.
     * @param unverifiedReport The encoded report data to be verified.
     */
    function verifyReport(bytes memory unverifiedReport) external {
        // Report verification fees
        IFeeManager feeManager = IFeeManager(
            address(s_verifierProxy.s_feeManager())
        );

        IRewardManager rewardManager = IRewardManager(
            address(feeManager.i_rewardManager())
        );

        (, /* bytes32[3] reportContextData */ bytes memory reportData) = abi
            .decode(unverifiedReport, (bytes32[3], bytes));

        address feeTokenAddress = feeManager.i_linkAddress();

        (Common.Asset memory fee, , ) = feeManager.getFeeAndReward(
            address(this),
            reportData,
            feeTokenAddress
        );

        // Approve rewardManager to spend this contract's balance in fees
        IERC20(feeTokenAddress).approve(address(rewardManager), fee.amount);

        // Verify the report
        bytes memory verifiedReportData = s_verifierProxy.verify(
            unverifiedReport,
            abi.encode(feeTokenAddress)
        );

        // Decode verified report data into a Report struct
        // If your report is a PremiumReport, you should decode it as a PremiumReport
        Report memory verifiedReport = abi.decode(verifiedReportData, (Report));

        // Log price from report
        emit DecodedPrice(verifiedReport.price);

        // Store the price from the report
        last_decoded_price = verifiedReport.price;
    }

    /**
     * @notice Withdraws all tokens of a specific ERC20 token type to a beneficiary address.
     * @dev Utilizes SafeERC20's safeTransfer for secure token transfer. Reverts if the contract's balance of the specified token is zero.
     * @param _beneficiary Address to which the tokens will be sent. Must not be the zero address.
     * @param _token Address of the ERC20 token to be withdrawn. Must be a valid ERC20 token contract.
     */
    function withdrawToken(
        address _beneficiary,
        address _token // LINK token address on Arbitrum Sepolia: 0x779877A7B0D9E8603169DdbD7836e478b4624789
    ) public onlyOwner {
        // Retrieve the balance of this contract
        uint256 amount = IERC20(_token).balanceOf(address(this));

        // Revert if there is nothing to withdraw
        if (amount == 0) revert NothingToWithdraw();

        IERC20(_token).safeTransfer(_beneficiary, amount);
    }
}