Binance token (BNB) smart contract security audit report performed by Callisto Security Audit Department
In total, 5 issues were reported including:
- 5 low severity issues.
No critical security issues were found.
-
It is possible to double withdrawal attack. More details here.
-
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.
Add the following code to the transfer(_to address, ...)
function:
require( _to != address(this) );
-
According to ERC20 standard when coins are minted a
Transfer
event should be emitted. -
There is no
Approval
event call atapprove
function. And EIP20 says:
MUST trigger on any successful call to approve(address _spender, uint256 _value).
- The
burn
function also should emit theTransfer
event.
EIP20 says that:
Transfers of 0 values MUST be treated as normal transfers and fire the Transfer event. But in this contract, function
transfer
has a condition:
if (_value <= 0) throw;
- There is no way to reset approved value to 0, because
approve
function contains:
if (_value <= 0) throw;
- Also it breaks the EIP20 security recommendation:
To prevent attack vectors like the one described here and discussed here, clients SHOULD make sure to create user interfaces in such a way that they set the allowance first to 0 before setting it to another value for the same spender. THOUGH The contract itself shouldn't enforce it, to allow backwards compatibility with contracts deployed before
Any ether sent directly to the contract through the fallback function will not result in an automatic buy of tokens but instead is directly sent to the contract balance.
https://gist.github.com/yuriy77k/7612e9b1f915f169542e711dd6a29166#file-bnb-sol-L144
The audited smart contract can be deployed. Only low severity issues were found during the audit.
https://gist.github.com/yuriy77k/b228e8df2aa47aef84e91423dd340894
https://gist.github.com/yuriy77k/ee463004023c4caee3b36bea30deb32f
https://gist.github.com/yuriy77k/b15d652f64211b51711f0648cdab6000