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Unprotected update current contract wasm

Description​

It warns you if update_current_contract_wasm() function is called without a previous check of the address of the caller. If users are allowed to call update_current_contract_wasm(), they can intentionally modify the contract behaviour, leading to the loss of all associated data/tokens and functionalities given by this contract or by others that depend on it.

Exploit Scenario​

Consider the following Soroban contract:

#[contractimpl]
impl UpgradeableContract {
    pub fn init(e: Env, admin: Address) {
        e.storage().instance().set(&DataKey::Admin, &admin);
    }

    pub fn version() -> u32 {
        1
    }

    pub fn upgrade(e: Env, new_wasm_hash: BytesN<32>) {
        e.deployer().update_current_contract_wasm(new_wasm_hash);
    }
}

This contract allows upgrades through the update_current_contract_wasm function. If just anyone can call this function, they could modify the contract behaviour.

The vulnerable code example can be found here.

Remediation​

To prevent this, the function should be restricted to administrators or authorized users only.

#[contractimpl]
impl UpgradeableContract {
    pub fn init(e: Env, admin: Address) {
        e.storage().instance().set(&DataKey::Admin, &admin);
    }

    pub fn version() -> u32 {
        1
    }

    pub fn upgrade(e: Env, new_wasm_hash: BytesN<32>) {
        let admin: Address = e.storage().instance().get(&DataKey::Admin).unwrap();
        admin.require_auth();

        e.deployer().update_current_contract_wasm(new_wasm_hash);
    }
}

The remediated code example can be found here.