Integer Overflow Vulnerabilities and Their Protection

Integer overflow is a common issue in programming. In most programming languages, integer values are stored in fixed-length memory. Integers can be divided into unsigned and signed numbers, with the distinction being whether the highest bit is used as a sign bit to represent positive or negative. For example, a 32-bit memory can store unsigned integers from 0 to 4,294,967,295 (uint32), or signed integers from -2,147,483,648 to 2,147,483,647 (int32).

When the calculation result exceeds the range that can be represented by the integer type, an overflow occurs. Most programming languages do not check for this kind of error but instead perform a simple modulo operation or produce undefined behavior. This can lead to unexpected results in the program's execution. In blockchain smart contracts, especially in the DeFi space, integer calculations are very common, so special attention must be paid to integer overflow vulnerabilities.

Definition of Integer Overflow

Integer overflow is divided into two situations: overflow ( and underflow ).

1. Overflow: The result exceeds the maximum value of the integer type. For example, adding 1 to uint32's 0xFFFFFFFF will result in 0x00000000.

2. Underflow: The result is less than the minimum value of the integer type. For example, subtracting 1 from uint32's 0 will result in 0xFFFFFFFF.

Protective Technology

The following measures can be taken in Rust to prevent integer overflow:

1. Configure Cargo.toml to check for integer overflow in release mode:

toml [profile.release] overflow-checks = true panic = 'abort'

2. Use the uint crate to support larger integers:

rust use uint::construct_uint;

construct_uint! { pub struct U1024(16); }

3. Use security math functions like checked_*:

rust let result = x.checked_add(y).expect("Addition overflow");

4. Use type conversion functions such as as_u128() to check for overflow:

rust let amount_u256 = U256::from(u128::MAX) + 1; let amount_u128 = amount_u256.as_u128(); // will trigger panic

By using these methods, we can effectively prevent integer overflow vulnerabilities in Rust smart contracts and enhance the security of the contracts. When writing smart contracts that involve mathematical calculations, it is essential to handle integer operations with caution and take appropriate protective measures.