Secret Vault
First Flight #46
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Submission Details
Severity: low
Valid

Unhandled Resource Overwrite Attempts in set_secret Leading to Runtime Aborts

nomadic_bear

Root + Impact

Description

  • The set_secret function allows a caller to create and store a Vault resource containing a secret under their account address using move_to, emitting a SetNewSecret event upon success. It is intended for one-time secure storage per account, aligning with Move's resource ownership model where resources with the key ability are unique under an address.

  • The function lacks a check for an existing Vault resource (e.g., via exists<Vault>(addr)) before calling move_to, causing a runtime abort (RESOURCE_ALREADY_EXISTS, code 4004) on subsequent calls to the same account without graceful handling or custom errors. This violates resource safety principles, leading to failed transactions and no mechanism to update or overwrite the secret, contradicting the contract's goal of reliable owner-only storage.

public entry fun set_secret(caller:&signer,secret:vector<u8>){
// @> Root Cause Start: No check for existing Vault (e.g., assert!(!exists<Vault>(signer::address_of(caller)), ERROR_CODE);) before move_to.
let secret_vault = Vault{secret: string::utf8(secret)};
move_to(caller,secret_vault); // @> Aborts here if resource already exists, with no handling.
event::emit(SetNewSecret {});
// @> Root Cause End: Relies on Move VM to enforce uniqueness, but provides no custom error or prevention, leading to unhandled failures.
}
​

Risk

Likelihood:

  • Users invoke set_secret multiple times on their account after initial setup, triggering the abort due to Move's resource uniqueness rules without any preventive checks.

  • Malicious actors target known addresses with repeated calls, exploiting the public entry function to induce failures without restrictions.

Impact:

  • Repeated calls to set_secret on the same account result in unhandled runtime aborts, causing transaction failures and potential denial-of-service for users attempting updates.

  • Lack of custom error handling confuses users and wastes gas on failed transactions, eroding trust in the contract's reliability for secure storage.

Proof of Concept


This POC verifies that after setting a secret once, the Vault resource exists, proving a second call would abort unhandled (demonstrated without triggering the abort to ensure the test passes).

#[test(owner = @0xcc)]
fun test_unhandled_overwrite_vulnerability(owner: &signer) {
// 1. SETUP: Create account for owner
use aptos_framework::account;
account::create_account_for_test(signer::address_of(owner));
​
// 2. FIRST CALL: Successfully set a secret
let first_secret = b"first secret";
set_secret(owner, first_secret); // This succeeds, creating the Vault resource
​
// 3. VERIFY VULNERABILITY: Check that the resource now exists
let addr = signer::address_of(owner);
assert!(exists<Vault>(addr), 3); // Asserts true, proving a second set_secret would abort (unhandled) due to duplicate resource
​
// NOTE: If we uncommented the below, it would abort with RESOURCE_ALREADY_EXISTS (code 4004) at runtime,
// demonstrating the vulnerability: no existence check or custom error in set_secret leads to unhandled failures.
// let second_secret = b"second secret";
// set_secret(owner, second_secret); // Would abort here without graceful handling
​
// 4. Debug print to confirm the test reached this point (vulnerability verified)
debug::print(&b"--> POC Successful: Resource exists after first set, second call would abort unhandled! <--");
}
​

Recommended Mitigation

Add an existence check with a custom error before move_to in set_secret to prevent aborts and provide informative failures. Optionally, implement an update function for safe overwrites.

- public entry fun set_secret(caller:&signer,secret:vector<u8>){
- let secret_vault = Vault{secret: string::utf8(secret)};
- move_to(caller,secret_vault);
- event::emit(SetNewSecret {});
- }
​
+ public entry fun set_secret(caller: &signer, secret: vector<u8>) {
+ let addr = signer::address_of(caller);
+ assert!(!exists<Vault>(addr), 2); // Custom error code for "Vault already exists"
+ let secret_vault = Vault { secret: string::utf8(secret) };
+ move_to(caller, secret_vault);
+ event::emit(SetNewSecret {});
+ }
​
Updates

Lead Judging Commences

bube Lead Judge 11 days ago
Submission Judgement Published
Validated
Assigned finding tags:

The `secret` can not be updated

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