Boost _ Folks Finance 34074 - [Smart Contract - Critical] Hub missing check for available liquidity could lead to locked fund and utilization ratio exceeding

Submitted on Mon Aug 05 2024 08:09:42 GMT-0400 (Atlantic Standard Time) by @A2Security for Boost | Folks Finance

Report ID: #34074

Report type: Smart Contract

Report severity: Critical

Target: https://testnet.snowtrace.io/address/0x2cAa1315bd676FbecABFC3195000c642f503f1C9

Impacts:

Temporary freezing of funds of at least 24h
Griefing (e.g. no profit motive for an attacker, but damage to the users or the protocol)
Smart contract unable to operate due to lack of token funds
Permanent freezing of funds

Description

Impact

The Hub doesn't check for available liquidity, leading to borrow/withdraw operation on the hub succeeding eventhough the spokeToken doesn't have enough liquidity. In the case of race conditions, e.g user A borrows 5000 ETH, and Whale B borrows/withdraws remaining liquidity from the ethHubPool. The borrow operation for user A will succeed, but the second part of the operation will revert. => This will lead to:

Utilization ratio surpassing 100% -> interest Rates becomes unbelievable high
User A wouldn't be able to withdraw his borrowed funds (locked) and will be forced to pay really high interest
User A wouldn't be able to reverse the action from spoke, because all operations from Hub -> spoke Chain can't be reversed

The higher the borrow amount, the bigger the chance that the user funds will be stuck (possibly forever, if the liquidity in the spoketoken, never reaches the wanted amount to borrow) Please note that, such a scenario is highly likeable considering that Folks Finance is cross chain by design, and operations like borrow/withdraw from spoke chains != Avalanche , will require 2 cross-chain actions that requires bridging through wormhole/ccip (which will take considerable time to be executed, and make predicting available liquidity not an easy task for protocol users)

Description

In HubPool.getSendTokenMessage() which is used to build the message to send through the bridgeRouter to the spoke contracts (mostly cross-chains)

    function getSendTokenMessage(IBridgeRouter bridgeRouter, uint16 adapterId, uint256 gasLimit, bytes32 accountId, uint16 chainId, uint256 amount, bytes32 recipient)
        external
        override
        onlyRole(HUB_ROLE)
        nonReentrant
        returns (Messages.MessageToSend memory)
    {
        // check chain is compatible
        bytes32 spokeAddress = getChainSpoke(chainId);

        // prepare message
>>        Messages.MessageParams memory params = Messages.MessageParams({adapterId: adapterId, returnAdapterId: 0, receiverValue: 0, gasLimit: gasLimit, returnGasLimit: 0});

As we can see in the message returnAdapterId is set to 0 meaning messages can't be reversed

Recomendation

An easy fix for this is to add a check for available liquidity to each a user actions that removes liquidity from a hubpool

if (pool.depositData.totalAmout < pool.variableData.totalAmount + pool.stableData.totalAmount + amount_to_remove){
    revert NotEnoughLiquidityAvailable;
}

(a side note we know that totaldebt here only includes principal and can in certain condition not be accurate, so we would also recommend adding a margin of safety (e.g 5%))

Proof of concept

Proof Of Concept

Test Result:

Ran 1 test for test/pocs/test_poc.sol:Pocs
[PASS] test_poc06() (gas: 1632608)
Logs:
  variable Interest Rate 1 %
  stable Interest Rate   8 %
  depositData.totalAmount avax 248 avax
  total debt hubpool avax 17 avax
  Alice borrows 258 avax
  Avax Alice Recieved 0
  variable Interest Rate 271 %
  stable Interest Rate   272 %
  depositData.totalAmount avax 248 avax
  total debt hubpool avax 276 avax

Suite result: ok. 1 passed; 0 failed; 0 skipped; finished in 684.53ms (9.27ms CPU time)

Ran 1 test suite in 687.47ms (684.53ms CPU time): 1 tests passed, 0 failed, 0 skipped (1 total tests)

To run the test please add test/pocs/base_test.sol

// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.19;

import "@forge-std/Test.sol";
import "contracts/hub/Hub.sol";
import "contracts/spoke/SpokeToken.sol";
import "contracts/spoke/SpokeCommon.sol";
import "contracts/hub/HubPool.sol";
import "contracts/hub/LoanManager.sol";
import "contracts/bridge/libraries/Messages.sol";
import "contracts/hub/AccountManager.sol";
import "contracts/bridge/BridgeRouter.sol";
import "contracts/bridge/HubAdapter.sol";
import "contracts/oracle/modules/NodeManager.sol";
import "contracts/hub/OracleManager.sol";
import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";

contract baseTest is Test {
    using SafeERC20 for address;
    // Hub public hub;

    uint256 mainnetFork;
    bytes32 public constant PREFIX = "HUB_ADAPTER_V1";
    address constant HUB_ADDRESS = 0xaE4C62510F4d930a5C8796dbfB8C4Bc7b9B62140; // Assuming this is the Hub address
    address constant SPOKE_COMMON = 0x6628cE08b54e9C8358bE94f716D93AdDcca45b00;
    address constant SPOKE_USDC = 0x89df7db4af48Ec7A84DE09F755ade9AF1940420b;
    address constant HUBPOOL_USDC = 0x1968237f3a7D256D08BcAb212D7ae28fEda72c34;
    address constant HUBPOOL_AVAX = 0xd90B7614551E799Cdef87463143eCe2efd4054f9;
    address constant SPOKE_AVAX = 0xBFf8b4e5f92eDD0A5f72b4b0E23cCa2Cc476ce2a;
    address constant LOAN_MANAGER = 0x2cAa1315bd676FbecABFC3195000c642f503f1C9;
    address constant ACCOUNT_MANAGER = 0x3324B5BF2b5C85999C6DAf2f77b5a29aB74197cc;
    address constant USDC_TOKEN = 0x5425890298aed601595a70AB815c96711a31Bc65;
    address constant ADAPTER = 0xf472ab58969709De9FfEFaeFFd24F9e90cf8DbF9;
    address constant LISTING_ROLE = 0x16870a6A85cD152229B97d018194d66740f932d6;
    address constant BRIDGE_ROUTER_HUB = 0xa9491a1f4f058832e5742b76eE3f1F1fD7bb6837;
    address constant ORACLE_MANAGER = 0x46c425F4Ec43b25B6222bcc05De051e6D3845165;
    address constant NODE_MANAGER = 0xA758c321DF6Cd949A8E074B22362a4366DB1b725;
    uint16 constant STABELE_LOAN_TYPE_ID = 1;
    uint16 constant VARIABLE_LOAN_TYPE_ID = 2;
    uint16 constant CHAIN_ID = 1; // Assuming Ethereum mainnet

    Hub hub;
    SpokeCommon spokeCommon;