unclaimed-storage-fee.md

Missing check for the storage fee before trying to unregister the storage

Configuration

• detector id: unclaimed-storage-fee
• severity: low

Description

According to NEP145, if the owner of an account tries to close the account, he needs to unregister the storage with a zero balance unless the force flag is set. So the implementation of NEP145 should comply with this rule.

Sample code

Here is a wrong example of storage_unregister:

fn storage_unregister(&mut self, force: Option<bool>) -> bool {
    assert_one_yocto();
    let account_id = env::predecessor_account_id();
    if let Some(balance) = self.accounts.get(&account_id) {
        self.accounts.remove(&account_id);
        self.total_supply -= balance;
        Promise::new(account_id.clone()).transfer(self.storage_balance_bounds().min.0 + 1);
        return true;
    } else {
        log!("The account {} is not registered", &account_id);
    }
    false
}

This one will remove the account from accounts without checking the balance. So the correct version is:

fn storage_unregister(&mut self, force: Option<bool>) -> bool {
    assert_one_yocto();
    let account_id = env::predecessor_account_id();
    let force = force.unwrap_or(false);
    if let Some(balance) = self.accounts.get(&account_id) {
        if balance == 0 || force {
            self.accounts.remove(&account_id);
            self.total_supply -= balance;
            Promise::new(account_id.clone()).transfer(self.storage_balance_bounds().min.0 + 1);
            true
        } else {
            env::panic_str(
                "Can't unregister the account with the positive balance without force",
            )
        }
    } else {
        log!("The account {} is not registered", &account_id);
        false
    }
}