Missing Contract State Check in Smart Contracts Leads to Critical Operational Disruptions
Service: Smart contract audit
Industry: Blockchain
Region: United States
Background
A smart contract handling a distributed exchange on a blockchain platform was found to have a fundamental weakness. Among the several uses for user storage management found in the contract were storage_deposit, storage_withdraw, and storage_unregister. These purposes, however, lacked appropriate validation to guarantee that the state of the contract was “resumed” prior to any user balance adjustments or token withdrawals execution. This control let the functions run when the contract was suspended, so upsetting the services of the platform and generating contract instability and financial disparities.
The vulnerability results from the neglect to verify whether the contract’s payable API state had returned before letting these activities go forward. Unintentional results from this weakness could include transactions conducted in a suspended state, maybe resulting in losses of money or mistakes in state transitions.
Severity: High
CVSS Score: 7.4 (CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H)
Affected Module: Smart Contract State Management
Exploit Complexity: Moderate
Discovery — Reproducing the Vulnerability
Discovering the vulnerability came from a security audit of the state management features of the smart contract. Review of the storage_deposit, storage_withdraw, and storage_unregister techniques revealed that none of these checked whether the contract had been suspended prior to state changes.
Here is an example of vulnerable code:
impl StorageManagement for State {
#[payable]
pub fn storage_deposit(&mut self, account_id: Option<AccountId>) -> StorageBalance {
let mut dex = self.as_dex_mut();
let contract = dex.contract_mut().latest();
// Missing check to ensure the contract is resumed
contract.accounts.update_or_insert(account_id, || {
// Deposit logic
});
self.logger_mut().log_storage_deposit_event(&account_id);
}
}
In this case, the function should ensure that the contract’s state is resumed before proceeding with the deposit logic. Without this check, the function can execute while the contract is suspended, leading to inconsistent behavior and data corruption.
Test Flow:
Identify the method handling user input (e.g.,
storage_deposit).Inspect the code for missing state validation related to the contract’s “resumed” state.
Simulate a call to the method while the contract is in a suspended state to verify if operations can proceed despite the suspension.
Observe the consequences of executing the method in this invalid state (e.g., invalid state transitions, incorrect balance updates).
Confirm successful exploitation by checking the contract state and user balances for discrepancies.
Technical Root Cause
The issue lies in the absence of state validation before executing transactions that modify user balances. The contract trusted that these functions could run without any state verification, which led to this security gap. As a result, sensitive functions could execute while the contract was suspended, disrupting the state flow and potentially causing unintended consequences, such as incorrect deposits or withdrawals.
A proper fix would be to include a check at the start of these functions to ensure that the contract is resumed before proceeding with any changes. Here’s a secure version of the function with the necessary state check:
impl StorageManagement for State {
#[payable]
pub fn storage_deposit(&mut self, account_id: Option<AccountId>) -> StorageBalance {
self.ensure_payable_api_resumed()?;
let mut dex = self.as_dex_mut();
let contract = dex.contract_mut().latest();
contract.accounts.update_or_insert(account_id, || {
// Deposit logic
});
self.logger_mut().log_storage_deposit_event(&account_id);
}
}
Real-World Risks
Financial Instability: Allowing operations while the contract is suspended can lead to erroneous transactions, disrupting the platform’s financial system and affecting user balances.
Service Downtime: If critical functions like deposit and withdrawal operations are allowed to run while the contract is suspended, the system may experience downtime or failures in processing transactions.
Data Integrity Issues: Executing these operations without proper state checks can corrupt data, causing discrepancies in balances or account status.
Loss of User Trust: Repeated failures or unexpected behavior due to this issue could erode user confidence in the platform and reduce participation.
Recommendations
Implement State Checks: Ensure that functions interacting with the contract’s balance or storage are gated by a check confirming the contract’s state is resumed before execution.
Review Contract Functions: Conduct a thorough review of all functions that interact with sensitive state changes to ensure similar issues do not exist elsewhere.
Conduct Regular Security Audits: Regular audits of smart contracts, particularly focusing on state transitions and contract suspension checks, can help prevent such vulnerabilities.
Use Safe State Transition Practices: Implement mechanisms to safely handle contract suspension and resumption, ensuring that no critical operations occur while the contract is in a suspended state.
Conclusion
The failure to properly check the contract’s state before executing critical operations is a significant vulnerability. It highlights the importance of validating contract state before processing user transactions to avoid unwanted disruptions or data corruption. Ensuring secure state transitions through proper checks will help safeguard both the platform and its users, maintaining trust and system integrity.
All identifiers, domains, and user data in this case study have been anonymized to preserve client confidentiality.
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