BitClave Token Audit

OpenZeppelin Security | November 2, 2017

The BitClave team asked us to review and audit their Consumer Activity Token (CAT) contracts. We looked at the code and now publish our results.

The audited code is located in the bitclave/crowdsale repository. The version used for this report is commit 057357fecbcc00c9a6cf96831d71d94fb7a13f03.

Great work reusing the existing OpenZeppelin libraries! The additional contracts are very thoughtfully designed, and are a good extension of the framework.

Here’s our assessment and recommendations, in order of importance.

Update: The BitClave team has followed most of our recommendations and updated the contracts. The new version is at commit d12edef05bcc5e5d24a0e53be224f304e1aa0ea8.

Critical Severity

No issues of critical severity.

High Severity

No issues of high severity.

Medium Severity

No issues of medium severity.

Low Severity

Misuse of FinalizableCrowdsale

As documented, to use FinalizableCrowdsale you must inherit from it and define a custom finalization function. Instead, in CATCrowdsale it was finalize that was redefined. Although it is not causing any problems in the code as is, the misuse of the library damages reusability. Rename finalize to finalization, including the super.finalize() line.

Update: This was fixed in the latest version.

Notes & Additional Information

  • Great work reusing the existing OpenZeppelin libraries!
  • The code is very modular, and looks thoughtfully designed. It is somewhat hard to navigate the inheritance chain, but this is mostly a consequence of the Crowdsale design in OpenZeppelin.
  • In BonusCrowdsale, there is a comment saying that bonuses are represented as values from 0 to 1000. We think this is wrong, as there could be, for example, a bonus of 200% (represented as 2000). If the comment is wrong, remove it. If it is correct, consider validating the values received in setBonusesForTimes and setBonusesForAmounts.
    Update: This was fixed in the latest version.
  • The value of decimals is duplicated in CATCrowdsale and CAToken. Try to avoid the redundancy so that the contracts can’t get out of sync.
  • The TokenMint event is redundant, given that MintableToken already emits both Mint and Transfer events.
    Update: This was fixed in the latest version.
  • The calculation of usdValue in BonusCrowdsale is somewhat obscure, and could use a comment explaining it or intermediate variables. (For example, it is not immediately clear why the division by 100 is needed.)
    Update: This was fixed in the latest version.
  • Consider removing the special case for when there are no bonuses in BonusCrowdsale’s buyTokens. It is a small optimization that is not worth the potential for error.
    Update: This was fixed in the latest version.

Conclusion

No critical or high severity issues were found. Some changes were proposed to follow best practices and reduce potential attack surface.

Note that as of the date of publishing, the above review reflects the current understanding of known security patterns as they relate to the Consumer Activity Token contracts. We have not reviewed the related BitClave project. The above should not be construed as investment advice. For general information about smart contract security, check out our thoughts here.

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