This is a Process Quality Review of the Gnosis DEX completed on 19 January, 2021. It was performed using the Process Review process (version 0.6.1) and is documented here. The review was performed by ShinkaRex of DeFiSafety. Check out our Telegram.

The final score of the review is 91%, an excellent score The breakdown of the scoring is in Scoring Appendix.

Summary of the Process

Very simply, the review looks for the following declarations from the developer's site. With these declarations, it is reasonable to trust the smart contracts.

• Here are my smart contracts on the blockchain

• Here is the documentation that explains what my smart contracts do

• Here are the tests I ran to verify my smart contract

• Here are the audit(s) performed on my code by third party experts

Disclaimer

This report is for informational purposes only and does not constitute investment advice of any kind, nor does it constitute an offer to provide investment advisory or other services. Nothing in this report shall be considered a solicitation or offer to buy or sell any security, token, future, option or other financial instrument or to offer or provide any investment advice or service to any person in any jurisdiction. Nothing contained in this report constitutes investment advice or offers any opinion with respect to the suitability of any security, and the views expressed in this report should not be taken as advice to buy, sell or hold any security. The information in this report should not be relied upon for the purpose of investing. In preparing the information contained in this report, we have not taken into account the investment needs, objectives and financial circumstances of any particular investor. This information has no regard to the specific investment objectives, financial situation and particular needs of any specific recipient of this information and investments discussed may not be suitable for all investors.

Any views expressed in this report by us were prepared based upon the information available to us at the time such views were written. The views expressed within this report are limited to DeFiSafety and the author and do not reflect those of any additional or third party and are strictly based upon DeFiSafety, its authors, interpretations and evaluation of relevant data. Changed or additional information could cause such views to change. All information is subject to possible correction. Information may quickly become unreliable for various reasons, including changes in market conditions or economic circumstances.

This completed report is copyright (c) DeFiSafety 2021. Permission is given to copy in whole, retaining this copyright label.

Code and Team

This section looks at the code deployed on the Mainnet that gets reviewed and its corresponding software repository. The document explaining these questions is here. This review will answer the questions;

1. Are the executing code addresses readily available? (Y/N)

2. Is the code actively being used? (%)

3. Is there a public software repository? (Y/N)

4. Is there a development history visible? (%)

5. Is the team public (not anonymous)? (Y/N)

Are the executing code addresses readily available? (Y/N)

They are available at website https://github.com/gnosis/dex-contracts/blob/master/networks.json as indicated in the Appendix. It would be better if this information was in a text file that is easier to read.

Is the code actively being used? (%)

Activity is 29 transactions a day on contract BatchExchange.sol, as indicated in the Appendix.

Percentage Score Guidance

100% More than 10 transactions a day 70% More than 10 transactions a week 40% More than 10 transactions a month 10% Less than 10 transactions a month 0% No activity

Is there a public software repository? (Y/N)

GitHub: https://github.com/gnosis​

Is there a public software repository with the code at a minimum, but normally test and scripts also (Y/N). Even if the repo was created just to hold the files and has just 1 transaction, it gets a Yes. For teams with private repos, this answer is No.

Is there a development history visible? (%)

With 985 commits and 20 branches in the dex-protocols repository, this is a healthy repo.

This checks if the software repository demonstrates a strong steady history. This is normally demonstrated by commits, branches and releases in a software repository. A healthy history demonstrates a history of more than a month (at a minimum).

Guidance: 100% Any one of 100+ commits, 10+branches 70% Any one of 70+ commits, 7+branches 50% Any one of 50+ commits, 5+branches 30% Any one of 30+ commits, 3+branches 0% Less than 2 branches or less than 10 commits

Is the team public (not anonymous)? (Y/N)

Information about the Gnosis founders can be found on their career page.​

For a yes in this question the real names of some team members must be public on the website or other documentation. If the team is anonymous and then this question is a No.

Documentation

This section looks at the software documentation. The document explaining these questions is here.

Required questions are;

1. Is there a whitepaper? (Y/N)

2. Are the basic software functions documented? (Y/N)

3. Does the software function documentation fully (100%) cover the deployed contracts? (%)

4. Are there sufficiently detailed comments for all functions within the deployed contract code (%)

5. Is it possible to trace from software documentation to the implementation in codee (%)

Is there a whitepaper? (Y/N)

Location: https://docs.gnosis.io/protocol/docs/devguide01/​

Are the basic software functions documented? (Y/N)

There is function documentation in their developer guide.​

Does the software function documentation fully (100%) cover the deployed contracts? (%)

All contracts and functions are documented.

Guidance:

100% All contracts and functions documented 80% Only the major functions documented 79-1% Estimate of the level of software documentation 0% No software documentation

How to improve this score

This score can improve by adding content to the requirements document such that it comprehensively covers the requirements. For guidance, refer to the SecurEth System Description Document . Using tools that aid traceability detection will help.

Are there sufficiently detailed comments for all functions within the deployed contract code (%)

Gnosis has some detailed comments, but most of the contract functions do not include any.

Code examples are in the Appendix. As per the SLOC, there is 46% commenting to code (CtC).

The Comments to Code (CtC) ratio is the primary metric for this score.

Guidance: 100% CtC > 100 Useful comments consistently on all code 90-70% CtC > 70 Useful comment on most code 60-20% CtC > 20 Some useful commenting 0% CtC < 20 No useful commenting

How to improve this score

This score can improve by adding comments to the deployed code such that it comprehensively covers the code. For guidance, refer to the SecurEth Software Requirements.

Is it possible to trace from software documentation to the implementation in code (%)

The documentation lists the functions and describes them, but there is limited amounts of clear association between the code and the documentation.

Guidance: 100% - Clear explicit traceability between code and documentation at a requirement level for all code 60% - Clear association between code and documents via non explicit traceability 40% - Documentation lists all the functions and describes their functions 0% - No connection between documentation and code

How to improve this score

This score can improve by adding traceability from requirements to code such that it is clear where each requirement is coded. For reference, check the SecurEth guidelines on traceability.

Testing

This section looks at the software testing available. It is explained in this document. This section answers the following questions;

1. Full test suite (Covers all the deployed code) (%)

2. Code coverage (Covers all the deployed lines of code, or explains misses) (%)

3. Scripts and instructions to run the tests (Y/N)

4. Packaged with the deployed code (Y/N)

5. Report of the results (%)

6. Formal Verification test done (%)

7. Stress Testing environment (%)

Is there a Full test suite? (%)

Gnosis's test to code ratio (TtC) is 670, demonstrating a robust testing suite.

This score is guided by the Test to Code ratio (TtC). Generally a good test to code ratio is over 100%. However the reviewers best judgement is the final deciding factor.

Guidance: 100% TtC > 120% Both unit and system test visible 80% TtC > 80% Both unit and system test visible 40% TtC < 80% Some tests visible 0% No tests obvious

How to improve this score

This score can improve by adding tests to fully cover the code. Document what is covered by traceability or test results in the software repository.

Code coverage (Covers all the deployed lines of code, or explains misses) (%)

Their coverall report reports a 100% coverage.

Guidance: 100% - Documented full coverage 99-51% - Value of test coverage from documented results 50% - No indication of code coverage but clearly there is a reasonably complete set of tests 30% - Some tests evident but not complete 0% - No test for coverage seen

How to improve this score

This score can improve by adding tests achieving full code coverage. A clear report and scripts in the software repository will guarantee a high score.

Scripts and instructions to run the tests (Y/N)

Scripts to run testing can be found on their GitHub readme.

How to improve this score

Add the scripts to the repository and ensure they work. Ask an outsider to create the environment and run the tests. Improve the scripts and docs based on their feedback.

Packaged with the deployed code (Y/N)

How to improve this score

Improving this score requires redeployment of the code, with the tests. This score gives credit to those who test their code before deployment and release them together. If a developer adds tests after deployment they can gain full points for all test elements except this one.

Report of the results (%)

Location: https://travis-ci.com/github/gnosis/dex-contracts​

Guidance: 100% - Detailed test report as described below 70% - GitHub Code coverage report visible 0% - No test report evident

How to improve this score

Add a report with the results. The test scripts should generate the report or elements of it.

Formal Verification test done (%)

There has been no formal verification testing done on the DEX contracts.

Stress Testing environment (%)

​Contracts on rinkby have been clearly stress-tested.​

Audits

​G0 Group has conducted an audit on Jan 27th, 2020.

Gnosis protocol was officially launched Apr 15th, 2020.

Guidance:

1. Multiple Audits performed before deployment and results public and implemented or not required (100%)

2. Single audit performed before deployment and results public and implemented or not required (90%)

3. Audit(s) performed after deployment and no changes required. Audit report is public. (70%)

4. No audit performed (20%)

5. Audit Performed after deployment, existence is public, report is not public and no improvements deployed OR smart contract address' not found, question 1 (0%)

Appendices

Author Details

The author of this review is Rex of DeFi Safety.

Email : rex@defisafety.com Twitter : @defisafety

I started with Ethereum just before the DAO and that was a wonderful education. It showed the importance of code quality. The second Parity hack also showed the importance of good process. Here my aviation background offers some value. Aerospace knows how to make reliable code using quality processes.

I was coaxed to go to EthDenver 2018 and there I started SecuEth.org with Bryant and Roman. We created guidelines on good processes for blockchain code development. We got EthFoundation funding to assist in their development.

Process Quality Reviews are an extension of the SecurEth guidelines that will further increase the quality processes in Solidity and Vyper development.

Career wise I am a business development manager for an avionics supplier.

Scoring Appendix

Executing Code Appendix

Code Used Appendix

Example Code Appendix

pragma solidity ^0.5.10;
​
import "@openzeppelin/contracts/math/SafeMath.sol";
import "@openzeppelin/contracts/token/ERC20/ERC20Detailed.sol";
import "solidity-bytes-utils/contracts/BytesLib.sol";
import "./BatchExchange.sol";
​
contract BatchExchangeViewer {
    using BytesLib for bytes;
    using SafeMath for uint256;
​
    uint8 public constant AUCTION_ELEMENT_WIDTH = 112;
    // Contains the orderId on top of the normal auction element data
    uint8 public constant INDEXED_AUCTION_ELEMENT_WIDTH = AUCTION_ELEMENT_WIDTH + 2;
    uint8 public constant ADDRESS_WIDTH = 20;
    uint16 public constant LARGE_PAGE_SIZE = 5000;
    // Can be used by external contracts to indicate no filter as it doesn't seem possible
    // to create an empty memory array in solidity.
    uint16[] public ALL_TOKEN_FILTER;
​
    BatchExchange batchExchange;
​
    constructor(BatchExchange exchange) public {
        batchExchange = exchange;
    }
​
    /** @dev Queries the orderbook for the auction that is still accepting orders
     *  @param tokenFilter all returned order will have buy *and* sell token from this list (leave empty for "no filter")
     *  @return encoded bytes representing orders, maxed at 5000 elements
     */
    function getOpenOrderBook(address[] memory tokenFilter) public view returns (bytes memory) {
        (bytes memory elements, , , ) = getOpenOrderBookPaginated(tokenFilter, address(0), 0, LARGE_PAGE_SIZE);
        require(
            elements.length < uint256(LARGE_PAGE_SIZE) * INDEXED_AUCTION_ELEMENT_WIDTH,
            "Orderbook too large, use paginated view functions"
        );
        return elements;
    }
​
    /** @dev Queries a page of the orderbook for the auction that is still accepting orders
     *  @param tokenFilter all returned order will have buy *and* sell token from this list (leave empty for "no filter")
     *  @param previousPageUser address taken from nextPageUser return value from last page (address(0) for first page)
     *  @param previousPageUserOffset offset taken nextPageUserOffset return value from last page (0 for first page)
     *  @param maxPageSize count of elements to be returned per page (same value is used for subqueries on the exchange)
     *  @return encoded bytes representing orders and page information for next page
     */
    function getOpenOrderBookPaginated(
        address[] memory tokenFilter,
        address previousPageUser,
        uint16 previousPageUserOffset,
        uint16 maxPageSize
    )
        public
        view
        returns (
            bytes memory elements,
            bool hasNextPage,
            address nextPageUser,
            uint16 nextPageUserOffset
        )
    {
        uint32 batch = batchExchange.getCurrentBatchId();
        return
            getFilteredOrdersPaginated(
                [batch, batch, batch + 1],
                getTokenIdsFromAdresses(tokenFilter),
                previousPageUser,
                previousPageUserOffset,
                maxPageSize
            );
    }
​
    /** @dev Queries the orderbook for the auction that is currently being solved
     *  @param tokenFilter all returned order will have buy *and* sell token from this list (leave empty for "no filter")
     *  @return encoded bytes representing orders, maxed at 5000 elements
     */
    function getFinalizedOrderBook(address[] memory tokenFilter) public view returns (bytes memory) {
        (bytes memory elements, , , ) = getFinalizedOrderBookPaginated(tokenFilter, address(0), 0, LARGE_PAGE_SIZE);
        require(
            elements.length < uint256(LARGE_PAGE_SIZE) * INDEXED_AUCTION_ELEMENT_WIDTH,
            "Orderbook too large, use paginated view functions"
        );
        return elements;
    }
​
    /** @dev Queries a page of the orderbook for the auction that is currently being solved
     *  @param tokenFilter all returned order will have buy *and* sell token from this list (leave empty for "no filter")
     *  @param previousPageUser address taken from nextPageUser return value from last page (address(0) for first page)
     *  @param previousPageUserOffset offset taken nextPageUserOffset return value from last page (0 for first page)
     *  @param maxPageSize count of elements to be returned per page (same value is used for subqueries on the exchange)
     *  @return encoded bytes representing orders and page information for next page
     */
    function getFinalizedOrderBookPaginated(
        address[] memory tokenFilter,
        address previousPageUser,
        uint16 previousPageUserOffset,
        uint16 maxPageSize
    )
        public
        view
        returns (
            bytes memory elements,
            bool hasNextPage,
            address nextPageUser,
            uint16 nextPageUserOffset
        )
    {
        uint32 batch = batchExchange.getCurrentBatchId();
        return
            getFilteredOrdersPaginated(
                [batch - 1, batch - 1, batch],
                getTokenIdsFromAdresses(tokenFilter),
                previousPageUser,
                previousPageUserOffset,
                maxPageSize
            );
    }
​
    /** @dev Queries a page in the list of all orders
     *  @param batchIds Triple with the following values [maxValidFrom, minValidUntil, sellBalanceTargetBatchIndex]
     *  Batched together as we are running out of local variables (Solidity does not compile with Stack too deep error)
     *      - maxValidFrom: all returned orders will have a validFrom <= this value (they were placed at or before that batch)
     *      - minValidUntil all returned orders will have a validUntil >= this value (validity ends at or after that batch)
     *      - sellBalanceTargetBatchIndex the batchIndex at which we are expecting the sellTokenBalance to be valid
        (e.g. in the current live orderbook we want to include sellBalances that are valid in currentBatch + 1).
     *  @param tokenFilter all returned order will have buy *and* sell token from this list (leave empty for "no filter")
     *  @param previousPageUser address taken from nextPageUser return value from last page (address(0) for first page)
     *  @param previousPageUserOffset offset taken nextPageUserOffset return value from last page (0 for first page)
     *  @param maxPageSize maximum count of elements to be returned per page (same value is used for subqueries on the exchange)
     *  @return encoded bytes representing orders and page information for next page. Result can contain less elements than
     *  maxPageSize if remaining gas is low.
     */

SLOC Appendix

Solidity Contracts

Comments to Code 529/1144 = 46%

Javascript Tests

Tests to Code 7669/1144 = 670%