QuantAMM
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Submission Details
Severity: low
Invalid

Incorrect Equality Check in _quantAMMUnpack128Array Function

aycozynfada

Summary

The _quantAMMUnpack128Array function in the provided Solidity code incorrectly sets an equality check in the require statement to >= instead of ==. This can lead to unintended behavior and potential errors in the function's logic.

Vulnerability Details

The require statement checks if _sourceArray.length * 2 is greater than or equal to _targetArrayLength (>=) instead of checking for equality (==). This can allow for cases where the lengths do not match as intended, leading to potential errors.

https://github.com/Cyfrin/2024-12-quantamm/blob/main/pkg/pool-quantamm/contracts/QuantAMMStorage.sol#L338-L346

function _quantAMMUnpack128Array(
int256[] memory _sourceArray, //50
uint _targetArrayLength // 50
) internal pure returns (int256[] memory targetArray) {
//
require(_sourceArray.length * 2 >= _targetArrayLength, "SRC!=TGT"); //should be require(_targetArrayLength == _sourceArray.length * 2, "SRC!=TGT");
targetArray = new int256[](_targetArrayLength); //targetArray is truncated if _targetArrayLength is wrong
uint targetIndex;

The _quantAMMUnpack128Array is often utilized by the updateRule.sol, QuantumVarianceBasedRule.sol and QuantumVarianceBasedRule.sol to repack states from 256 bits to 128 bit integers. The resulting integers(_targetArrayLength) is always going to be double the sourceArray length but the way the function is structured in this code will leave room for an occasion whereby the _targetArrayLength can be lesser than the expected index, thereby truncating the resulting 128 bit target array.

Also as being commented in the require statement the sourceArraylength * 2 Is expected to be strictly equal to the target array length ; , "SRC!=TGT");

Impact

Dos and discrepamcy in state being packed by the _quantAMMUnpack128Array() due to array truncation

Tools Used

Manual review

Recommendations

Adjust the require statement to ensure that _sourceArray.length * 2 is equals to _targetArrayLength

--require(_sourceArray.length * 2 >= _targetArrayLength, "SRC!=TGT");
++require(_sourceArray.length * 2 == _targetArrayLength, "SRC!=TGT");
targetArray = new int256[](_targetArrayLength);
uint targetIndex;

Similar fix is needed in QuantAmmStorage.sol#QuantAmmUnpack32Array.

Updates

Lead Judging Commences

n0kto Lead Judge 7 months ago
Submission Judgement Published
Invalidated
Reason: Non-acceptable severity
Assigned finding tags:

Informational or Gas / Admin is trusted / Pool creation is trusted / User mistake / Suppositions

Please read the CodeHawks documentation to know which submissions are valid. If you disagree, provide a coded PoC and explain the real likelyhood and the detailed impact on the mainnet without any supposition (if, it could, etc) to prove your point.

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