S2C8: Multi-Lock Contract #

1. Problem #

The contract has multiple "lock" mechanisms that must be unlocked sequentially before mintFlag can be called. Each lock has different unlock conditions (such as paying ETH, specific states, storage operations, etc.).

2. Cause #

The contract implements layered access control — multiple modifiers or condition checks stacked together. Each layer can be unlocked through specific operations.

3. Solution #

1. Read contract storage to analyze the state of each lock
2. Unlock each lock in order (send ETH, call specific functions, write storage)
3. Call mintFlag after all locks are unlocked

4. Pitfalls Encountered #

Lock Dependencies: Some locks may depend on the state of other locks, so the unlocking order may matter. The attack contract needs to have ETH deposited in advance.

5. Pitfall Causes #

There may be dependencies between the contract's state variables. Operating in the wrong order could cause state resets or transaction reverts.

6. How to Resolve #

Read lock states one by one via cast storage, and design atomic operations to unlock all locks in a single transaction.

7. Key Technical Points #