# Integer Overflow & Arithmetic Security Audit

Systematic audit for integer overflow, underflow, precision loss, and arithmetic vulnerabilities in Solidity smart contracts. Covers both pre-0.8 overflow and modern unchecked block misuse.

## Attack Patterns Covered

**1. Unchecked Block Overflow (post-Solidity 0.8)**
- `unchecked { a + b }` without range validation allows wrap-around
- Common in gas-optimized loops: `for (uint i; i < n; unchecked { ++i })`
- Dangerous when: result used as array index, token amount, or timestamp
- Detection: grep `unchecked` blocks, verify all arithmetic is bounded

**2. Precision Loss in Division**
- Integer division truncates: `1e18 / 3` = 333333333333333333 (loses 1 wei)
- Compound effect: `(a * b) / c` vs `a * (b / c)` — different results
- Multigig protocol rounding: always-down rounding can drain protocol fees
- Detection: check division order, identify fee calculations with truncation

**3. Phantom Overflow via Casting**
- `uint256(int256(-1))` = 2^256 - 1 (max uint)
- `uint128(largeUint256)` silently truncates high bits
- `int256(uint256(2**255))` wraps to negative
- Detection: audit all explicit type casts between signed/unsigned

**4. Intermediate Overflow Before SafeMath**
- `a * b / c` where `a * b` overflows before division
- Pre-0.8 SafeMath does not protect intermediate values
- Fix: use `mulDiv(a, b, c)` from FullMath (Uniswap v3 pattern)
- Detection: find multiplication-then-division in price/ratio calculations

**5. Block Timestamp Arithmetic**
- `block.timestamp + 365 days` overflows if timestamp near uint32 max
- `deadline - block.timestamp` underflows if deadline already passed
- Detection: check timestamp arithmetic for underflow on comparison

**6. ERC20 Balance Underflow**
- `balances[from] -= amount` without checking `balances[from] >= amount`
- Pre-0.8: wraps to max uint (instant infinite balance)
- Detection: verify all balance decrements have explicit or implicit bounds

## Deliverables

- Complete arithmetic vulnerability map of the codebase
- Severity classification (Critical/High/Medium/Low)
- PoC showing overflow/underflow exploitation path
- Fix recommendations with safe arithmetic patterns