Inheritable Smart Contract Wallet

Summary

The _incrementCounter function in the contract increments a counter using Solidity’s default checked arithmetic (i.e. counter += 1). In Solidity 0.8.x, arithmetic operations include overflow checks by default. In cases where overflow is highly unlikely or controlled (as with a simple counter), these checks add unnecessary gas overhead. Using an unchecked block can reduce gas costs for this frequently called function, improving overall contract efficiency.

Vulnerability Details

• Location:

  function _incrementCounter() internal returns (uint256) {

  return counter += 1;

  }

• Issue:
  The statement counter += 1; is executed with overflow checks enabled by default. Since the counter is expected to increment reliably without reaching the overflow threshold, these checks are redundant and cost extra gas on every call.

Root Cause

Solidity 0.8.x automatically inserts overflow checks in arithmetic operations. In scenarios like a monotonically increasing counter—where the risk of overflow is minimal or managed—the checks result in unnecessary gas expenditure. The lack of an unchecked block in this simple increment operation is the root cause of the gas inefficiency.

Impact

• Technical Impact:

  • Increased gas consumption on every invocation of _incrementCounter.

  • Reduced overall efficiency, particularly in high-frequency operations such as minting NFTs or processing multiple transactions, especially in contracts that call this function repeatedly.

Tools Used

• Foundry:

• Forge Test Framework: For simulating and capturing gas consumption differences between checked and unchecked arithmetic operations.

Mitigation

Recommendation:
Modify the _incrementCounter function to use an unchecked block, as shown below:

Benefits:

• Eliminates redundant overflow checks for a counter that is unlikely to overflow.

• Reduces gas consumption per function call.