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Process Quality Review (0.7)


Final score:90%
Date:23 Sep 2021
Audit Process:version 0.7
Author:Nick of DeFiSafety
PQR Score:90%


Scoring Appendix

The final review score is indicated as a percentage. The percentage is calculated as Achieved Points due to MAX Possible Points. For each element the answer can be either Yes/No or a percentage. For a detailed breakdown of the individual weights of each question, please consult this document.

The blockchain used by this protocol

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

  • Here is my smart contract on the blockchain
  • You can see it matches a software repository used to develop the code
  • Here is the documentation that explains what my smart contract does
  • Here are the tests I ran to verify my smart contract
  • Here are the audit(s) performed to review my code by third party experts

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 2023. 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.

1. Are the executing code addresses readily available? (%)

Answer: 100%

They are available at website https://github.com/gnosis/gp-v2-contracts/blob/main/networks.json, as indicated in the Appendix. The contracts were located on the bottom left of the front page.

Deployed Contracts:Download filelink

Percentage Score Guidance:
Clearly labelled and on website, docs or repo, quick to find
Clearly labelled and on website, docs or repo but takes a bit of looking
Addresses in mainnet.json, in discord or sub graph, etc
Address found but labeling not clear or easy to find
Executing addresses could not be found

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

Answer: 100%

Activity is 400 transactions a day on contract Gnosis Protocol: GPv2Settlement, as indicated in the Appendix.

Deployed Contracts:Download filelink

Percentage Score Guidance:
More than 10 transactions a day
More than 10 transactions a week
More than 10 transactions a month
Less than 10 transactions a month
No activity

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

Answer: Yes

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

Score Guidance:
There is a public software repository with the code at a minimum, but also normally test and scripts. Even if the repository was created just to hold the files and has just 1 transaction.
For teams with private repositories.

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

Answer: 100%

With 1712 commits and 72 branches, Cowswap's development history is beautifully rich and detailed.

This metric 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).

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

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

Answer: Yes

For a "Yes" in this question, the real names of some team members must be public on the website or other documentation (LinkedIn, etc). If the team is anonymous, then this question is a "No".



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

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

Answer: Yes

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

Answer: Yes

The documents cover basic software functions.

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

Answer: 100%

The software documentation fully covers both deployed contracts.

Percentage Score Guidance:
All contracts and functions documented
Only the major functions documented
79 - 1%
Estimate of the level of software documentation
No software documentation

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

Answer: 73%

Code examples are in the Appendix. As per the SLOC, there is 73% commenting to code (CtC).

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

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

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

Answer: 60%

The CowSwap documentation provides a clear association between code and documents via non explicit traceability at https://docs.cowswap.exchange/smart-contracts/settlement-contract/signature-schemes.

Percentage Score Guidance:
Clear explicit traceability between code and documentation at a requirement level for all code
Clear association between code and documents via non explicit traceability
Documentation lists all the functions and describes their functions
No connection between documentation and code



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

Answer: 100%

Code examples are in the Appendix. As per the SLOC, there is 371% testing to code (TtC).

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.

Percentage Score Guidance:
TtC > 120% Both unit and system test visible
TtC > 80% Both unit and system test visible
TtC < 80% Some tests visible
No tests obvious

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

Answer: 97%

GPv2/CowSwap has 97% code coverage according to the coveralls report found at https://coveralls.io/github/gnosis/gp-v2-contracts?branch=main.

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

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

Answer: Yes

Scripts/Instructions location: https://github.com/gnosis/cowswap

14. Report of the results (%)

Answer: 70%

The GPv2/CowSwap code coverage report is available at https://coveralls.io/github/gnosis/gp-v2-contracts?branch=main, and is also linked in their contracts' GitHub repo.

Percentage Score Guidance:
Detailed test report as described below
GitHub code coverage report visible
No test report evident

15. Formal Verification test done (%)

Answer: 0%

No formal verification could be found.

16. Stress Testing environment (%)

Answer: 100%

Cowswap has been deployed to multiple testnets.



This section looks at the 3rd party software audits done. It is explained in this document.

17. Did 3rd Party audits take place? (%)

Answer: 90%

​One audit was released shortly after Cowswap's deployment, but was started beforehand. While the results are public it is very short at just 3 pages.

Percentage Score Guidance:
Multiple Audits performed before deployment and results public and implemented or not required
Single audit performed before deployment and results public and implemented or not required
Audit(s) performed after deployment and no changes required. Audit report is public
Audit(s) performed after deployment and changes needed but not implemented
No audit performed
Audit Performed after deployment, existence is public, report is not public and no improvements deployed OR smart contract address not found, (where question 1 is 0%)
Deduct 25% if code is in a private repo and no note from auditors that audit is applicable to deployed code.

18. Is the bug bounty acceptable high? (%)

Answer: 50%

The GPv2/CowSwap Bug Bounty program rewards participating users with up to 50k for bug finds. Program information can be found at https://medium.com/@gnosisPM/announcing-gnosis-protocol-v2-bug-bounty-f3e44e934566.

Percentage Score Guidance:
Bounty is 10% TVL or at least $1M AND active program (see below)
Bounty is 5% TVL or at least 500k AND active program
Bounty is 5% TVL or at least 500k
Bounty is 100k or over AND active program
Bounty is 100k or over
Bounty is 50k or over AND active program
Bounty is 50k or over
Bug bounty program bounty is less than 50k
No bug bounty program offered
An active program means that a third party (such as Immunefi) is actively driving hackers to the site. An inactive program would be static mentions on the docs.

Access Controls


This section covers the documentation of special access controls for a DeFi protocol. The admin access controls are the contracts that allow updating contracts or coefficients in the protocol. Since these contracts can allow the protocol admins to "change the rules", complete disclosure of capabilities is vital for user's transparency. It is explained in this document.

19. Can a user clearly and quickly find the status of the access controls (%)

Answer: 100%

The documents detailing the planned decentralisation process clearly state the status of access controls.

Percentage Score Guidance:
Clearly labelled and on website, docs or repo, quick to find
Clearly labelled and on website, docs or repo but takes a bit of looking
Access control docs in multiple places and not well labelled
Access control docs in multiple places and not labelled
Admin Control information could not be found

20. Is the information clear and complete (%)

Answer: 100%

All the core executing contracts are immutable.

Percentage Score Guidance:
All the contracts are immutable -- 100% OR
a) All contracts are clearly labelled as upgradeable (or not) -- 30% AND
b) The type of ownership is clearly indicated (OnlyOwner / MultiSig / Defined Roles) -- 30% AND
c) The capabilities for change in the contracts are described -- 30%

21. Is the information in non-technical terms that pertain to the investments (%)

Answer: 100%

The contracts are immutable, and this is clearly identified.

Percentage Score Guidance:
All the contracts are immutable
Description relates to investments safety and updates in clear, complete non-software language
Description all in software specific language
No admin control information could be found

22. Is there Pause Control documentation including records of tests (%)

Answer: 100%

No pause control can be used on the GPv2/CowSwap core executing smart contracts due to their immutability.

Percentage Score Guidance:
All the contracts are immutable or no pause control needed and this is explained OR Pause control(s) are clearly documented and there is records of at least one test within 3 months
Pause control(s) explained clearly but no evidence of regular tests
Pause controls mentioned with no detail on capability or tests
Pause control not documented or explained


 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. DeFiSafety is my full time gig and we are working on funding vehicles for a permanent staff.

123    constructor(GPv2Authentication authenticator_, IVault vault_) {
4        authenticator = authenticator_;
5        vault = vault_;
6        vaultRelayer = new GPv2VaultRelayer(vault_);
7    }
89    // solhint-disable-next-line no-empty-blocks
10    receive() external payable {
11        // NOTE: Include an empty receive function so that the settlement
12        // contract can receive Ether from contract interactions.
13    }
1415    /// @dev This modifier is called by settle function to block any non-listed
16    /// senders from settling batches.
17    modifier onlySolver {
18        require(authenticator.isSolver(msg.sender), "GPv2: not a solver");
19        _;
20    }
2122    /// @dev Modifier to ensure that an external function is only callable as a
23    /// settlement interaction.
24    modifier onlyInteraction {
25        require(address(this) == msg.sender, "GPv2: not an interaction");
26        _;
27    }
2829    /// @dev Settle the specified orders at a clearing price. Note that it is
30    /// the responsibility of the caller to ensure that all GPv2 invariants are
31    /// upheld for the input settlement, otherwise this call will revert.
32    /// Namely:
33    /// - All orders are valid and signed
34    /// - Accounts have sufficient balance and approval.
35    /// - Settlement contract has sufficient balance to execute trades. Note
36    ///   this implies that the accumulated fees held in the contract can also
37    ///   be used for settlement. This is OK since:
38    ///   - Solvers need to be authorized
39    ///   - Misbehaving solvers will be slashed for abusing accumulated fees for
40    ///     settlement
41    ///   - Critically, user orders are entirely protected
42    ///
43    /// @param tokens An array of ERC20 tokens to be traded in the settlement.
44    /// Trades encode tokens as indices into this array.
45    /// @param clearingPrices An array of clearing prices where the `i`-th price
46    /// is for the `i`-th token in the [`tokens`] array.
47    /// @param trades Trades for signed orders.
48    /// @param interactions Smart contract interactions split into three
49    /// separate lists to be run before the settlement, during the settlement
50    /// and after the settlement respectively.
51    function settle(
52        IERC20[] calldata tokens,
53        uint256[] calldata clearingPrices,
54        GPv2Trade.Data[] calldata trades,
55        GPv2Interaction.Data[][3] calldata interactions
56    ) external nonReentrant onlySolver {
57        executeInteractions(interactions[0]);
5859        (
60            GPv2Transfer.Data[] memory inTransfers,
61            GPv2Transfer.Data[] memory outTransfers
62        ) = computeTradeExecutions(tokens, clearingPrices, trades);
6364        vaultRelayer.transferFromAccounts(inTransfers);
6566        executeInteractions(interactions[1]);
6768        vault.transferToAccounts(outTransfers);
6970        executeInteractions(interactions[2]);
7172        emit Settlement(msg.sender);
73    }
7475    /// @dev Settle an order directly against Balancer V2 pools.
76    ///
77    /// @param swaps The Balancer V2 swap steps to use for trading.
78    /// @param tokens An array of ERC20 tokens to be traded in the settlement.
79    /// Swaps and the trade encode tokens as indices into this array.
80    /// @param trade The trade to match directly against Balancer liquidity. The
81    /// order will always be fully executed, so the trade's `executedAmount`
82    /// field is used to represent a swap limit amount.
83    function swap(
84        IVault.BatchSwapStep[] calldata swaps,
85        IERC20[] calldata tokens,
86        GPv2Trade.Data calldata trade
87    ) external nonReentrant onlySolver {
88        RecoveredOrder memory recoveredOrder = allocateRecoveredOrder();
89        GPv2Order.Data memory order = recoveredOrder.data;
90        recoverOrderFromTrade(recoveredOrder, tokens, trade);
9192        IVault.SwapKind kind =
93            order.kind == GPv2Order.KIND_SELL
94                ? IVault.SwapKind.GIVEN_IN
95                : IVault.SwapKind.GIVEN_OUT;
9697        IVault.FundManagement memory funds;
98        funds.sender = recoveredOrder.owner;
99        funds.fromInternalBalance =
100            order.sellTokenBalance == GPv2Order.BALANCE_INTERNAL;
101        funds.recipient = payable(recoveredOrder.receiver);
102        funds.toInternalBalance =
103            order.buyTokenBalance == GPv2Order.BALANCE_INTERNAL;
104105        int256[] memory limits = new int256[](tokens.length);
106        uint256 limitAmount = trade.executedAmount;
107        // NOTE: Array allocation initializes elements to 0, so we only need to
108        // set the limits we care about. This ensures that the swap will respect
109        // the order's limit price.
110        if (order.kind == GPv2Order.KIND_SELL) {
111            require(limitAmount >= order.buyAmount, "GPv2: limit too low");
112            limits[trade.sellTokenIndex] = order.sellAmount.toInt256();
113            limits[trade.buyTokenIndex] = -limitAmount.toInt256();
114        } else {
115            require(limitAmount <= order.sellAmount, "GPv2: limit too high");
116            limits[trade.sellTokenIndex] = limitAmount.toInt256();
117            limits[trade.buyTokenIndex] = -order.buyAmount.toInt256();
118        }
119120        GPv2Transfer.Data memory feeTransfer;
121        feeTransfer.account = recoveredOrder.owner;
122        feeTransfer.token = order.sellToken;
123        feeTransfer.amount = order.feeAmount;
124        feeTransfer.balance = order.sellTokenBalance;
125126        int256[] memory tokenDeltas =
127            vaultRelayer.batchSwapWithFee(
128                kind,
129                swaps,
130                tokens,
131                funds,
132                limits,
133                // NOTE: Specify a deadline to ensure that an expire order
134                // cannot be used to trade.
135                order.validTo,
136                feeTransfer
137            );
138139        bytes memory orderUid = recoveredOrder.uid;
140        uint256 executedSellAmount =
141            tokenDeltas[trade.sellTokenIndex].toUint256();
142        uint256 executedBuyAmount =
143            (-tokenDeltas[trade.buyTokenIndex]).toUint256();
144145        // NOTE: Check that the orders were completely filled and update their
146        // filled amounts to avoid replaying them. The limit price and order
147        // validity have already been verified when executing the swap through
148        // the `limit` and `deadline` parameters.
149        require(filledAmount[orderUid] == 0, "GPv2: order filled");
150        if (order.kind == GPv2Order.KIND_SELL) {
151            require(
152                executedSellAmount == order.sellAmount,
153                "GPv2: sell amount not respected"
154            );
155            filledAmount[orderUid] = order.sellAmount;
156        } else {
157            require(
158                executedBuyAmount == order.buyAmount,
159                "GPv2: buy amount not respected"
160            );
161            filledAmount[orderUid] = order.buyAmount;
162        }
163164        emit Trade(
165            recoveredOrder.owner,
166            order.sellToken,
167            order.buyToken,
168            executedSellAmount,
169            executedBuyAmount,
170            order.feeAmount,
171            orderUid
172        );
173        emit Settlement(msg.sender);
174    }
175176    /// @dev Invalidate onchain an order that has been signed offline.
177    ///
178    /// @param orderUid The unique identifier of the order that is to be made
179    /// invalid after calling this function. The user that created the order
180    /// must be the the sender of this message. See [`extractOrderUidParams`]
181    /// for details on orderUid.
182    function invalidateOrder(bytes calldata orderUid) external {
183        (, address owner, ) = orderUid.extractOrderUidParams();
184        require(owner == msg.sender, "GPv2: caller does not own order");
185        filledAmount[orderUid] = uint256(-1);
186        emit OrderInvalidated(owner, orderUid);
187    }
188189    /// @dev Free storage from the filled amounts of **expired** orders to claim
190    /// a gas refund. This method can only be called as an interaction.
191    ///
192    /// @param orderUids The unique identifiers of the expired order to free
193    /// storage for.
194    function freeFilledAmountStorage(bytes[] calldata orderUids)
195        external
196        onlyInteraction
197    {
198        freeOrderStorage(filledAmount, orderUids);
199    }
200201    /// @dev Free storage from the pre signatures of **expired** orders to claim
202    /// a gas refund. This method can only be called as an interaction.
203    ///
204    /// @param orderUids The unique identifiers of the expired order to free
205    /// storage for.
206    function freePreSignatureStorage(bytes[] calldata orderUids)
207        external
208        onlyInteraction
209    {
210        freeOrderStorage(preSignature, orderUids);
211    }
212213    /// @dev Process all trades one at a time returning the computed net in and
214    /// out transfers for the trades.
215    ///
216    /// This method reverts if processing of any single trade fails. See
217    /// [`computeTradeExecution`] for more details.
218    ///
219    /// @param tokens An array of ERC20 tokens to be traded in the settlement.
220    /// @param clearingPrices An array of token clearing prices.
221    /// @param trades Trades for signed orders.
222    // @return inTransfers Array of in transfers of executed sell amounts.
223    // @return outTransfers Array of out transfers of executed buy amounts.
224    function computeTradeExecutions(
225        IERC20[] calldata tokens,
226        uint256[] calldata clearingPrices,
227        GPv2Trade.Data[] calldata trades
228    )
229        internal
230        returns (
231            GPv2Transfer.Data[] memory inTransfers,
232            GPv2Transfer.Data[] memory outTransfers
233        )
234    {
235        RecoveredOrder memory recoveredOrder = allocateRecoveredOrder();
236237        inTransfers = new GPv2Transfer.Data[](trades.length);
238        outTransfers = new GPv2Transfer.Data[](trades.length);
239240        for (uint256 i = 0; i < trades.length; i++) {
241            GPv2Trade.Data calldata trade = trades[i];
242243            recoverOrderFromTrade(recoveredOrder, tokens, trade);
244            computeTradeExecution(
245                recoveredOrder,
246                clearingPrices[trade.sellTokenIndex],
247                clearingPrices[trade.buyTokenIndex],
248                trade.executedAmount,
249                inTransfers[i],
250                outTransfers[i]
251            );
252        }
253    }

Solidity Contracts


Comments to Code: 718 / 990 =  73 %

JavaScript Tests


Tests to Code: 3673 / 990 = 371 %