Root + Impact

Description

• Describe the normal behavior in one or more sentences

  Answer: The set_secret function should allow the vault owner to create or update their stored secret multiple times without failure, ensuring the secret remains under their control.

  
  

• Explain the specific issue or problem in one or more sentences

  The function always uses move_to to create a new Vault resource. In Move, move_to aborts if the resource already exists under that account, which means the owner can only set their secret once. Any attempt to update it later will fail with a RESOURCE_ALREADY_EXISTS error.

Risk

Likelihood:

• Reason 1 // Describe WHEN this will occur (avoid using "if" statements)

  This occurs whenever the same account tries to call set_secret more than once, since the first call already placed a Vault resource at their address.

  
  

• Reason 2

  This occurs because there is no logic to check for the existence of the Vault resource and mutate it; instead, the code blindly tries to create a new one every time.

Impact:

• Impact 1

  The contract fails to support secret updates, locking users into their first stored value permanently.

  
  

• Impact 2

  This undermines usability and can cause users to lose control if they mistakenly set the wrong secret, as they cannot overwrite it without deleting their account’s state.

Proof of Concept

The first call creates a Vault resource at the owner’s address.

The second call attempts to use move_to again, but since the Vault already exists there, Move aborts with a RESOURCE_ALREADY_EXISTS error.

This demonstrates that the vault cannot be updated once initialized.

Recommended Mitigation

Before creating a new Vault, check whether the resource already exists at the signer’s address.

If it does, borrow it mutably and update the secret field instead of overwriting.

If it does not exist, create it normally with move_to.

This ensures the vault can be created once and updated safely multiple times, meeting expected behavior.