ZRX Audit Report.

ETH_ZRX_report.md

Security Audit Report

1. Summary

ZRX Token smart contract security audit report performed by Callisto Security Audit Department

Token desription:

Symbol      : ZRX
Name        : 0x Protocol Token
Total supply: 1,000,000,000
Decimals    : 18 
Standard    : ERC20

2. In scope

• ZRXToken.sol

3. Findings

In total, 4 issues were reported including:

• 1 medium severity issues.

• 3 low severity issues.

No critical security issues were found.

3.1. Known vulnerabilities of ERC-20 token

Severity: low

Description

1. It is possible to double withdrawal attack. More details here.

2. Lack of transaction handling mechanism issue. WARNING! This is a very common issue and it already caused millions of dollars losses for lots of token users! More details here.

Recommendation

Add the following code to the transfer(_to address, ...) function:

require( _to != address(this) );

3.2. ERC-20 Compliance

Severity: medium

Description

• Following EIP-20 specifications transfer should throw when the msg.sender doesn't have enough fund.
• Same as previously following the specifications transferFrom should throw and not return false if the _from address doesn't have enough of fund or if the allowed value isn't enough to cover the transaction _value.

Code snippet

https://gist.github.com/yuriy77k/9e3f16ce8289f6fafa64c9fee13dfd1f#file-zrxtoken-sol-L60

https://gist.github.com/yuriy77k/9e3f16ce8289f6fafa64c9fee13dfd1f#file-zrxtoken-sol-L70

3.3. Unlimited Allowance

Severity: low

Description

Even if the likelihood of such issue to represent a risk for users is very low, the reimplemented transferFrom with unlimited allowance to an address is not complaint with ERC-20 standard. Users should be aware of it.

Code snippet

https://gist.github.com/yuriy77k/9e3f16ce8289f6fafa64c9fee13dfd1f#file-zrxtoken-sol-L108

3.4. No zero address checking

Severity: low

Description

In functions transfer and transferFrom there are no zero address checking.

Code snippet

https://gist.github.com/yuriy77k/9e3f16ce8289f6fafa64c9fee13dfd1f#file-zrxtoken-sol-L60

https://gist.github.com/yuriy77k/9e3f16ce8289f6fafa64c9fee13dfd1f#file-zrxtoken-sol-L70

4. Conclusion

The audited code has some ERC20 compliance issues.

5. Revealing audit reports

https://gist.github.com/yuriy77k/3a07536517aef3a02b64024db39f5407

https://gist.github.com/yuriy77k/471b6aeffdc8bc2c5c6a406dbe656ec7

https://gist.github.com/yuriy77k/dfa68fb6651cd142bc1ae85c681dc58c