Allowance should always larger or equal to the transferred amount

[code423n4]

Lines of code

https://github.com/code-423n4/2022-07-swivel/blob/main/Creator/ZcToken.sol#L111-L115 https://github.com/code-423n4/2022-07-swivel/blob/main/Creator/ZcToken.sol#L132-L134 https://github.com/code-423n4/2022-07-swivel/blob/main/Tokens/ZcToken.sol#L111-L115 https://github.com/code-423n4/2022-07-swivel/blob/main/Tokens/ZcToken.sol#L111-L115

Vulnerability details

Impact

Detailed description of the impact of this finding.

Wrong operators are set.

Proof of Concept

Provide direct links to all referenced code in GitHub. Add screenshots, logs, or any other relevant proof that illustrates the concept.

[Line 111 - 115]

if (allowed >= previewAmount) { revert Approvals(allowed, previewAmount);}

should be changed to

if (allowed < previewAmount) { revert Approvals(allowed, previewAmount);}

[Line 132 - 134]

if (allowed >= principalAmount) { revert Approvals(allowed, principalAmount); }

should be changed to

if (allowed < principalAmount) { revert Approvals(allowed, principalAmount); }

Tools Used

Manual

Recommended Mitigation Steps

Using the current code, If allowance < value, code will be reverted because of underflow after substraction if allowance >= value, code will be reverted because of the if statement

which is not what we want

[scaraven]

duplicate of #180

[JTraversa]

Duplicate of #129

[bghughes]

Duplicate of #129