ProtectedERC20Gateway Static Analysis Findings

PEC-01S: Redundant Function Implementations

Type	Severity	Location
Gas Optimization		ProtectedERC20Gateway.sol:L128-L130, L134-L136

Description:

The referenced ProtectedERC20Gateway::receive and ProtectedERC20Gateway::fallback function implementations are redundant as Solidity's behaviour is to not include them if they are not explicitly specified in the version utilized.

Example:

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128receive() external payable {
129  revert('Receive not allowed');
130}
131/**
132 * @dev Revert fallback calls
133 */
134fallback() external payable {
135  revert('Fallback not allowed');
136}

Recommendation:

We advise them to be safely omitted, optimizing the contract's deployment gas cost as well as the legibility of the codebase.

Alleviation:

Both function implementations have been removed as advised.

PEC-02S: Inexistent Sanitization of Input Address

Type	Severity	Location
Input Sanitization		ProtectedERC20Gateway.sol:L26-L32

Description:

The linked function accepts an address argument yet does not properly sanitize it.

Impact:

The presence of zero-value addresses, especially in constructor implementations, can cause the contract to be permanently inoperable. These checks are advised as zero-value inputs are a common side-effect of off-chain software related bugs.

Example:

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26constructor(
27  IPool pool
28) {
29  POOL = pool;
30  
31  
32}

Recommendation:

We advise some basic sanitization to be put in place by ensuring that the address specified is non-zero.

Alleviation:

The input pool address of the ProtectedERC20Gateway::constructor is now adequately sanitized via a newly introduced UtilLib and specifically its UtilLib::checkNonZeroAddress function.

PEC-03S: Improper Invocations of EIP-20 transferFrom

Type	Severity	Location
Standard Conformity		ProtectedERC20Gateway.sol:L41, L72, L107

Description:

The linked statements do not properly validate the returned bool of the EIP-20 standard transferFrom function. As the standard dictates, callers must not assume that false is never returned.

Impact:

If the code mandates that the returned bool is true, this will cause incompatibility with tokens such as USDT / Tether as no such bool is returned to be evaluated causing the check to fail at all times. On the other hand, if the token utilized can return a false value under certain conditions but the code does not validate it, the contract itself can be compromised as having received / sent funds that it never did.

Example:

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41token.transferFrom(msg.sender, address(this), amount);

Recommendation:

Since not all standardized tokens are EIP-20 compliant (such as Tether / USDT), we advise a safe wrapper library to be utilized instead such as SafeERC20 by OpenZeppelin to opportunistically validate the returned bool only if it exists in each instance.

Alleviation:

The Kinza Finance team has stated that they wish to not sanitize the yielded bool values as the tokens they intend to integrate with will either revert or yield true.

We consider the gas overhead of evaluating the yielded bool to be minimal and as such will mark this exhibit as acknowledged.