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Yearn v2 Process Quality Review

Score: 93%

This is a Yearn V2 Process Quality Review completed on 27 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 previous version of the review (0Yearn V1) is here.

The final score of the review is 93%, a super solid 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)

Answer: Yes

They are available at website https://docs.yearn.finance/developers/deployed-contracts-registry as indicated in the Appendix.

Is the code actively being used? (%)

Answer: 100%

Activity is 25 transactions a day on contract yVault.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)

Answer: Yes

GitHub: https://github.com/iearn-finance​

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? (%)

Answer: 100%

With 183 commits and 4 branches, this is a healthy repository.

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)

Answer: Yes

The Yearn team is found on https://docs.yearn.finance/additional-resources/team​

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)

Answer: Yes

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

Answer: Yes

There are a few places to view the software function documentation, most notably in their yVault Documentation, as well as the rest of the "developers" secton in their documentation.

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

Answer: 100%

The major contracts are well documented in their documentation, but there are many smaller contracts that are missing software function documentation. The yVaults have the most robust documentation of yearn's contracts.

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 (%)

Answer: 80%

The CtC seems to understate how much commenting there is on the Vyper code. For this reason the score was increase to 70%.

Code examples are in the Appendix. As per the SLOC, there is 24% 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 (%)

Answer: 80%

There is clear tractability for their v2 contracts in their documentation for all of their major contracts

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? (%)

Answer: 80%

TtC is 100%, python to vyper. We are learning that python testing lis by the line

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) (%)

Answer: 95%

The code coverage report is found by expanding the "Run Tests" element of this report. Not user friendly but it is still new with Vyper and Brownie.

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)

Answer: Yes

Testing instructions can be found in their github. ​

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)

Answer: Yes

The tests are packaged with the deployed repository in github.

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 (%)

Answer: 60%

Buried in the actions there is a test report. However it is not published neatly and the content is limited, though it does have the list of tests and coverage results. For this reason a score of 60% is given.

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 (%)

Answer: 0%

There is no formal verification testing evident.

Stress Testing environment (%)

Answer: 0%

No active test networks are evident.

Audits

Answer: 100%

Yearn V2 has been audited by:

​PeckShield​

​MixBytes (twice)​

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 : [email protected]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.

Scoring Appendix

Executing Code Appendix

Code Used Appendix

Example Code Appendix

# @version 0.2.8
"""
@title Yearn Token Vault
@license GNU AGPLv3
@author yearn.finance
@notice
Yearn Token Vault. Holds an underlying token, and allows users to interact
with the Yearn ecosystem through Strategies connected to the Vault.
Vaults are not limited to a single Strategy, they can have as many Strategies
as can be designed (however the withdrawal queue is capped at 20.)
​
Deposited funds are moved into the most impactful strategy that has not
already reached its limit for assets under management, regardless of which
Strategy a user's funds end up in, they receive their portion of yields
generated across all Strategies.
​
When a user withdraws, if there are no funds sitting undeployed in the
Vault, the Vault withdraws funds from Strategies in the order of least
impact. (Funds are taken from the Strategy that will disturb everyone's
gains the least, then the next least, etc.) In order to achieve this, the
withdrawal queue's order must be properly set and managed by the community
(through governance).
​
Vault Strategies are parameterized to pursue the highest risk-adjusted yield.
​
There is an "Emergency Shutdown" mode. When the Vault is put into emergency
shutdown, assets will be recalled from the Strategies as quickly as is
practical (given on-chain conditions), minimizing loss. Deposits are
halted, new Strategies may not be added, and each Strategy exits with the
minimum possible damage to position, while opening up deposits to be
withdrawn by users. There are no restrictions on withdrawals above what is
expected under Normal Operation.
​
For further details, please refer to the specification:
https://github.com/iearn-finance/yearn-vaults/blob/master/SPECIFICATION.md
"""
​
API_VERSION: constant(String[28]) = "0.3.0"
​
from vyper.interfaces import ERC20
​
implements: ERC20
​
​
interface DetailedERC20:
def name() -> String[42]: view
def symbol() -> String[20]: view
def decimals() -> uint256: view
​
​
interface Strategy:
def want() -> address: view
def vault() -> address: view
def estimatedTotalAssets() -> uint256: view
def withdraw(_amount: uint256) -> uint256: nonpayable
def migrate(_newStrategy: address): nonpayable
​
​
interface GuestList:
def authorized(guest: address, amount: uint256) -> bool: view
​
​
# NOTE: Track the total for overhead targeting purposes
strategies: public(HashMap[address, StrategyParams])
MAXIMUM_STRATEGIES: constant(uint256) = 20
​
# Ordering that `withdraw` uses to determine which strategies to pull funds from
# NOTE: Does *NOT* have to match the ordering of all the current strategies that
# exist, but it is recommended that it does or else withdrawal depth is
# limited to only those inside the queue.
# NOTE: Ordering is determined by governance, and should be balanced according
# to risk, slippage, and/or volatility. Can also be ordered to increase the
# withdrawal speed of a particular Strategy.
# NOTE: The first time a ZERO_ADDRESS is encountered, it stops withdrawing
withdrawalQueue: public(address[MAXIMUM_STRATEGIES])
​
emergencyShutdown: public(bool)
​
depositLimit: public(uint256) # Limit for totalAssets the Vault can hold
debtRatio: public(uint256) # Debt ratio for the Vault across all strategies (in BPS, <= 10k)
totalDebt: public(uint256) # Amount of tokens that all strategies have borrowed
lastReport: public(uint256) # block.timestamp of last report
activation: public(uint256) # block.timestamp of contract deployment
​
rewards: public(address) # Rewards contract where Governance fees are sent to
# Governance Fee for management of Vault (given to `rewards`)
managementFee: public(uint256)
# Governance Fee for performance of Vault (given to `rewards`)
performanceFee: public(uint256)
MAX_BPS: constant(uint256) = 10_000 # 100%, or 10k basis points
SECS_PER_YEAR: constant(uint256) = 31_557_600 # 365.25 days
# `nonces` track `permit` approvals with signature.
nonces: public(HashMap[address, uint256])
DOMAIN_SEPARATOR: public(bytes32)
DOMAIN_TYPE_HASH: constant(bytes32) = keccak256('EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)')
PERMIT_TYPE_HASH: constant(bytes32) = keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)")
​
​
@external
def initialize(
token: address,
governance: address,
rewards: address,
nameOverride: String[64],
symbolOverride: String[32],
guardian: address = msg.sender,
):
"""
@notice
Initializes the Vault, this is called only once, when the contract is
deployed.
The performance fee is set to 10% of yield, per Strategy.
The management fee is set to 2%, per year.
The initial deposit limit is set to 0 (deposits disabled); it must be
updated after initialization.
@dev
If `nameOverride` is not specified, the name will be 'yearn'
combined with the name of `token`.
​
If `symbolOverride` is not specified, the symbol will be 'y'
combined with the symbol of `token`.
@param token The token that may be deposited into this Vault.
@param governance The address authorized for governance interactions.
@param rewards The address to distribute rewards to.
@param nameOverride Specify a custom Vault name. Leave empty for default choice.
@param symbolOverride Specify a custom Vault symbol name. Leave empty for default choice.
@param guardian The address authorized for guardian interactions. Defaults to caller.
"""
assert self.activation == 0 # dev: no devops199
self.token = ERC20(token)
if nameOverride == "":
self.name = concat(DetailedERC20(token).symbol(), " yVault")
else:
self.name = nameOverride
if symbolOverride == "":
self.symbol = concat("yv", DetailedERC20(token).symbol())
else:
self.symbol = symbolOverride
self.decimals = DetailedERC20(token).decimals()
self.governance = governance
log UpdateGovernance(governance)
self.management = governance
log UpdateManagement(governance)
self.rewards = rewards
log UpdateRewards(rewards)
self.guardian = guardian
log UpdateGuardian(guardian)
self.performanceFee = 1000 # 10% of yield (per Strategy)
log UpdatePerformanceFee(convert(1000, uint256))
self.managementFee = 200 # 2% per year
log UpdateManagementFee(convert(200, uint256))
self.lastReport = block.timestamp
self.activation = block.timestamp
​

SLOC Appendix

Contracts

Language

Files

Lines

Blanks

Comments

Code

Complexity

Solidity

1

711

82

420

209

34

Vyper

2

1906

35

56

1815

9

Total

3

2617

117

476

2024

43

Comments to Code 476 / 2024 = 24%

Python Tests

Language

Files

Lines

Blanks

Comments

Code

Complexity

Python

27

2641

524

284

1833

114

Tests to Code 1833 / 1815 = 100.0%