[SEC] Implement Safe Math and Overflow Protection for Aggregations

[Queenode]

🟡 Priority: High
Difficulty: Hard
Estimated Effort: 2-3 days
Relevant Files: contracts/src/lib.rs
Labels: security, priority:high, rust

Requirements

1. Explicit Safe Math

   • While Rust panics on integer overflow in debug mode, it performs two's complement wrapping in release mode unless explicitly configured otherwise (the Cargo.toml currently has overflow-checks = true for release, which is good, but explicit code handles it better).
   • Replace standard operators (+, *) with checked arithmetic methods (checked_add, checked_mul) when calculating pool sizes and totals.

2. Vulnerable Areas

   • pool_size = contribution_amount * frozen_count;
   • current_contribution + amount
   • If an admin maliciously initializes a group with contribution_amount = i128::MAX, the multiplication for pool_size will overflow.

3. Implementation

   • Update payout():

     let pool_size = contribution_amount.checked_mul(frozen_count).expect("Math overflow in pool calculation");

   • Update contribute():

     let new_total = current_contribution.checked_add(amount).expect("Math overflow in contribution sum");

4. Validation on Initialize

   • Add bounds checking in initialize().
   • Prevent unrealistic contribution amounts (e.g., contribution_amount <= 0 should panic).
   • Ensure contribution_amount is within a reasonable maximum bounds (e.g., < 1_000_000_000_000_000 stroops).

5. Testing

   • Unit test: Initialize with negative amount (panics).
   • Unit test: Initialize with zero amount (panics).
   • Unit test: Simulate a scenario that would cause pool_size to exceed i128::MAX and verify the expect() panic triggers cleanly instead of wrapping.
   • Target: 100% coverage on boundary conditions.

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