Badger Citadel contest - defsec's results

C4-001 : The Contract Should approve(0) first

Impact - LOW

Some tokens (like USDT L199) do not work when changing the allowance from an existing non-zero allowance value. They must first be approved by zero and then the actual allowance must be approved.

IERC20(token).safeApprove(address(operator), 0);
IERC20(token).safeApprove(address(operator), amount);

Proof of Concept

1. Navigate to the following contracts.

https://github.com/code-423n4/2022-04-badger-citadel/blob/dab143a990a9c355578fbb15cd3c884614e33f42/src/CitadelMinter.sol#L136
https://github.com/code-423n4/2022-04-badger-citadel/blob/dab143a990a9c355578fbb15cd3c884614e33f42/src/Funding.sol#L142

2. When trying to re-approve an already approved token, all transactions revert and the protocol cannot be used.

Tools Used

None

Recommended Mitigation Steps

Approve with a zero amount first before setting the actual amount. Consider use safeIncreaseAllowance and safeDecreaseAllowance.

C4-002 : Use of Block.timestamp

Impact - Non-Critical

Block timestamps have historically been used for a variety of applications, such as entropy for random numbers (see the Entropy Illusion for further details), locking funds for periods of time, and various state-changing conditional statements that are time-dependent. Miners have the ability to adjust timestamps slightly, which can prove to be dangerous if block timestamps are used incorrectly in smart contracts.

Proof of Concept

1. Navigate to the following contract.

https://github.com/code-423n4/2022-04-badger-citadel/blob/dab143a990a9c355578fbb15cd3c884614e33f42/src/StakedCitadel.sol#L399

https://github.com/code-423n4/2022-04-badger-citadel/blob/dab143a990a9c355578fbb15cd3c884614e33f42/src/SupplySchedule.sol#L95

Tools Used

Manual Code Review

Recommended Mitigation Steps

Block timestamps should not be used for entropy or generating random numbers—i.e., they should not be the deciding factor (either directly or through some derivation) for winning a game or changing an important state.

Time-sensitive logic is sometimes required; e.g., for unlocking contracts (time-locking), completing an ICO after a few weeks, or enforcing expiry dates. It is sometimes recommended to use block.number and an average block time to estimate times; with a 10 second block time, 1 week equates to approximately, 60480 blocks. Thus, specifying a block number at which to change a contract state can be more secure, as miners are unable to easily manipulate the block number.

C4-003 : Missing events for only functions that change critical parameters

Impact - Non critical

The afunctions that change critical parameters should emit events. Events allow capturing the changed parameters so that off-chain tools/interfaces can register such changes with timelocks that allow users to evaluate them and consider if they would like to engage/exit based on how they perceive the changes as affecting the trustworthiness of the protocol or profitability of the implemented financial services. The alternative of directly querying on-chain contract state for such changes is not considered practical for most users/usages.

Missing events and timelocks do not promote transparency and if such changes immediately affect users’ perception of fairness or trustworthiness, they could exit the protocol causing a reduction in liquidity which could negatively impact protocol TVL and reputation.

Proof of Concept

1. Navigate to the following contract.

https://github.com/code-423n4/2022-04-badger-citadel/blob/dab143a990a9c355578fbb15cd3c884614e33f42/src/StakedCitadel.sol#L676

https://github.com/code-423n4/2022-04-dualityfocus/blob/f21ef7708c9335ee1996142e2581cb8714a525c9/contracts/vault_and_oracles/UniV3LpVault.sol#L906

See similar High-severity H03 finding OpenZeppelin’s Audit of Audius (https://blog.openzeppelin.com/audius-contracts-audit/#high) and Medium-severity M01 finding OpenZeppelin’s Audit of UMA Phase 4 (https://blog.openzeppelin.com/uma-audit-phase-4/)

Tools Used

None

Recommended Mitigation Steps

Add events to all functions that change critical parameters.

C4-004 : # DoS With Block Gas Limit

Impact - Non-Critical

When smart contracts are deployed or functions inside them are called, the execution of these actions always requires a certain amount of gas, based of how much computation is needed to complete them. The Ethereum network specifies a block gas limit and the sum of all transactions included in a block can not exceed the threshold.

Programming patterns that are harmless in centralized applications can lead to Denial of Service conditions in smart contracts when the cost of executing a function exceeds the block gas limit. Modifying an array of unknown size, that increases in size over time, can lead to such a Denial of Service condition.

Proof of Concept

1. Follow the functions shown below.

https://github.com/code-423n4/2022-04-badger-citadel/blob/main/src/CitadelMinter.sol#L152

https://github.com/code-423n4/2022-04-badger-citadel/blob/main/src/CitadelMinter.sol#L344

Tools Used

Code Review

Recommended Mitigation Steps

Caution is advised when you expect to have large arrays that grow over time. Actions that require looping across the entire data structure should be avoided.

If you absolutely must loop over an array of unknown size, then you should plan for it to potentially take multiple blocks, and therefore require multiple transactions.

C4-005 : Critical changes should use two-step procedure

Impact - NON CRITICAL

The critical procedures should be two step process.

Proof of Concept

1. Navigate to the following contract.

https://github.com/code-423n4/2022-04-badger-citadel/blob/dab143a990a9c355578fbb15cd3c884614e33f42/src/StakedCitadel.sol#L572

Tools Used

Code Review

Recommended Mitigation Steps

Lack of two-step procedure for critical operations leaves them error-prone. Consider adding two step procedure on the critical functions.

C4-006 : Front-runnable Initializers

Impact - LOW

All contract initializers were missing access controls, allowing any user to initialize the contract. By front-running the contract deployers to initialize the contract, the incorrect parameters may be supplied, leaving the contract needing to be redeployed.

Proof of Concept

1. Navigate to the following contracts.

https://github.com/code-423n4/2022-04-badger-citadel/blob/dab143a990a9c355578fbb15cd3c884614e33f42/src/StakedCitadel.sol#L167

https://github.com/code-423n4/2022-04-badger-citadel/blob/dab143a990a9c355578fbb15cd3c884614e33f42/src/KnightingRound.sol#L109

https://github.com/code-423n4/2022-04-badger-citadel/blob/dab143a990a9c355578fbb15cd3c884614e33f42/src/StakedCitadelVester.sol#L59

2. initialize functions does not have access control. They are vulnerable to front-running.

Tools Used

Manual Code Review

Recommended Mitigation Steps

While the code that can be run in contract constructors is limited, setting the owner in the contract's constructor to the msg.sender and adding the onlyOwner modifier to all initializers would be a sufficient level of access control.

C4-007 : Incompatibility With Rebasing/Deflationary/Inflationary tokens

Impact - LOW

PrePo protocol do not appear to support rebasing/deflationary/inflationary tokens whose balance changes during transfers or over time. The necessary checks include at least verifying the amount of tokens transferred to contracts before and after the actual transfer to infer any fees/interest.

Proof of Concept

1. Navigate to the following contract.

https://github.com/code-423n4/2022-04-badger-citadel/blob/dab143a990a9c355578fbb15cd3c884614e33f42/src/StakedCitadel.sol#L461

https://github.com/code-423n4/2022-04-badger-citadel/blob/dab143a990a9c355578fbb15cd3c884614e33f42/src/KnightingRound.sol#L414

Tools Used

Manual Code Review

Recommended Mitigation Steps

• Ensure that to check previous balance/after balance equals to amount for any rebasing/inflation/deflation
• Add support in contracts for such tokens before accepting user-supplied tokens
• Consider supporting deflationary / rebasing / etc tokens by extra checking the balances before/after or strictly inform your users not to use such tokens if they don't want to lose them.

C4-008 : # Missing Re-entrancy Guard

Impact - LOW

The re-entrancy guard is missing on the some of the functions. The external interactions can cause to the re-entrancy vulnerability.

Proof of Concept

1. Navigate to the following contract.

https://github.com/code-423n4/2022-04-badger-citadel/blob/dab143a990a9c355578fbb15cd3c884614e33f42/src/StakedCitadelVester.sol#L85

Tools Used

Code Review

Recommended Mitigation Steps

Follow the check effect interaction pattern or put re-entrancy guard.

C4-009 : # Floating Pragma

Impact

In the contracts, floating pragmas are used. Contracts should be deployed with the same compiler version and flags that they have been tested with thoroughly. Locking the pragma helps to ensure that contracts do not accidentally get deployed using, for example, an outdated compiler version that might introduce bugs that affect the contract system negatively.

## Proof of Concept

https://swcregistry.io/docs/SWC-103

  src/CitadelToken.sol::2 => pragma solidity ^0.8.0;
  src/GlobalAccessControl.sol::3 => pragma solidity ^0.8.0;

Tools Used

Manual code review

Recommended Mitigation Steps

Lock the pragma version: delete pragma solidity 0.8.0 in favor of pragma solidity 0.8.0

C4-010 : # Use pragma abicoder v2

Impact

The code contains "pragma experimental ABIEncoderV2;" In the later Solidity versions it is no longer necessary to use the "experimental" version. Using experimental constructions is not recommended for production code.

See: https://docs.soliditylang.org/en/v0.8.7/layout-of-source-files.html#abiencoderv2

## Proof of Concept

https://github.com/code-423n4/2022-04-badger-citadel/blob/main/src/GlobalAccessControl.sol#L4

Tools Used

Manual code review

Recommended Mitigation Steps

Replace pragma experimental ABIEncoderV2; with pragma abicoder v2;

And make sure you use at least solidity version 0.7.5.

C4-001: Revert String Size Optimization

Impact

Shortening revert strings to fit in 32 bytes will decrease deploy time gas and will decrease runtime gas when the revert condition has been met.

Revert strings that are longer than 32 bytes require at least one additional mstore, along with additional overhead for computing memory offset, etc.

Proof of Concept

Revert strings > 32 bytes are here:

https://github.com/code-423n4/2022-04-badger-citadel/blob/main/src/CitadelMinter.sol#L321

Tools Used

Manual Review

Recommended Mitigation Steps

Shorten the revert strings to fit in 32 bytes. That will affect gas optimization.

C4-002 : Adding unchecked directive can save gas

Impact

For the arithmetic operations that will never over/underflow, using the unchecked directive (Solidity v0.8 has default overflow/underflow checks) can save some gas from the unnecessary internal over/underflow checks.

Proof of Concept

https://github.com/code-423n4/2022-04-badger-citadel/blob/main/src/CitadelMinter.sol#L152

https://github.com/code-423n4/2022-04-badger-citadel/blob/main/src/CitadelMinter.sol#L344

https://github.com/code-423n4/2022-04-badger-citadel/blob/main/src/KnightingRound.sol#L260

Tools Used

None

Recommended Mitigation Steps

Consider applying unchecked arithmetic where overflow/underflow is not possible.

C4-003 : Use calldata instead of memory for function parameters

Impact

In some cases, having function arguments in calldata instead of memory is more optimal.

Consider the following generic example:

contract C {
function add(uint[] memory arr) external returns (uint sum) {
uint length = arr.length;
for (uint i = 0; i < arr.length; i++) {
sum += arr[i];
}
}
}

In the above example, the dynamic array arr has the storage location memory. When the function gets called externally, the array values are kept in calldata and copied to memory during ABI decoding (using the opcode calldataload and mstore). And during the for loop, arr[i] accesses the value in memory using a mload. However, for the above example this is inefficient. Consider the following snippet instead:

contract C {
function add(uint[] calldata arr) external returns (uint sum) {
uint length = arr.length;
for (uint i = 0; i < arr.length; i++) {
sum += arr[i];
}
}
}

In the above snippet, instead of going via memory, the value is directly read from calldata using calldataload. That is, there are no intermediate memory operations that carries this value.

Gas savings: In the former example, the ABI decoding begins with copying value from calldata to memory in a for loop. Each iteration would cost at least 60 gas. In the latter example, this can be completely avoided. This will also reduce the number of instructions and therefore reduces the deploy time cost of the contract.

In short, use calldata instead of memory if the function argument is only read.

Note that in older Solidity versions, changing some function arguments from memory to calldata may cause "unimplemented feature error". This can be avoided by using a newer (0.8.*) Solidity compiler.

Examples Note: The following pattern is prevalent in the codebase:

function f(bytes memory data) external {
(...) = abi.decode(data, (..., types, ...));
}

Here, changing to bytes calldata will decrease the gas. The total savings for this change across all such uses would be quite significant.

Proof Of Concept

Examples:

https://github.com/code-423n4/2022-04-badger-citadel/blob/main/src/CitadelMinter.sol#L152

https://github.com/code-423n4/2022-04-badger-citadel/blob/main/src/CitadelMinter.sol#L344

Tools Used

None

Recommended Mitigation Steps

Change memory definition with calldata.

C4-004 : Non-strict inequalities are cheaper than strict ones

Impact

Strict inequalities add a check of non equality which costs around 3 gas.

Proof of Concept

https://github.com/code-423n4/2022-04-badger-citadel/blob/main/src/KnightingRound.sol#L313

Tools Used

Code Review

Recommended Mitigation Steps

Use >= or <= instead of > and < when possible.

C4-005: Use of constant keccak variables results in extra hashing (and so gas).

Impact

That would Increase gas costs on all privileged operations.

Proof of Concept

The following role variables are marked as constant.

https://github.com/code-423n4/2022-04-badger-citadel/blob/main/src/KnightingRound.sol#L19
https://github.com/code-423n4/2022-04-badger-citadel/blob/main/src/KnightingRound.sol#L24
https://github.com/code-423n4/2022-04-badger-citadel/blob/main/src/GlobalAccessControl.sol#L40
https://github.com/code-423n4/2022-04-badger-citadel/blob/main/src/GlobalAccessControl.sol#L25

This results in the keccak operation being performed whenever the variable is used, increasing gas costs relative to just storing the output hash. Changing to immutable will only perform hashing on contract deployment which will save gas.

See: ethereum/solidity#9232 (https://github.com/ethereum/solidity/issues/9232#issuecomment-646131646)

Tools Used

Code Review

Recommended Mitigation Steps

Consider to change the variable to be immutable rather than constant.

C4-006 : Check if amount > 0 before token transfer can save gas

Impact

Since _amount can be 0. Checking if (_amount != 0) before the transfer can potentially save an external call and the unnecessary gas cost of a 0 token transfer.

Proof of Concept

https://github.com/code-423n4/2022-04-badger-citadel/blob/main/src/StakedCitadel.sol#L469

All Contracts

Tools Used

None

Recommended Mitigation Steps

Consider checking amount != 0.

C4-007 : There is no need to assign default values to variables

Impact - Gas Optimization

When a variable is declared solidity assigns the default value. In case the contract assigns the value again, it costs extra gas.

Example: uint x = 0 costs more gas than uint x without having any different functionality.

Proof of Concept

https://github.com/code-423n4/2022-04-badger-citadel/blob/main/src/CitadelMinter.sol#L152

https://github.com/code-423n4/2022-04-badger-citadel/blob/main/src/CitadelMinter.sol#L344

Tools Used

Code Review

Recommended Mitigation Steps

uint x = 0 costs more gas than uint x without having any different functionality.

C4-008 : Use Shift Right/Left instead of Division/Multiplication if possible

Impact

A division/multiplication by any number x being a power of 2 can be calculated by shifting log2(x) to the right/left.

While the DIV opcode uses 5 gas, the SHR opcode only uses 3 gas. Furthermore, Solidity's division operation also includes a division-by-0 prevention which is bypassed using shifting.

Proof of Concept

1. Navigate to the following smart contract line.

  src/Funding.sol::36 => uint256 public citadelPriceInAsset; /// asset per citadel price eg. 1 WBTC (8 decimals) = 40,000 CTDL ==> price = 10^8 / 40,000
  src/KnightingRound.sol::43 => /// eg. 1 WBTC (8 decimals) = 40,000 CTDL ==> price = 10^8 / 40,000
  src/StakedCitadel.sol::252 => maxWithdrawalFee = WITHDRAWAL_FEE_HARD_CAP; // 2% maximum withdrawal fee
  src/StakedCitadel.sol::253 => maxManagementFee = MANAGEMENT_FEE_HARD_CAP; // 2% maximum management fee
  src/StakedCitadelVester.sol::34 => uint256 public constant INITIAL_VESTING_DURATION = 86400 * 21; // 21 days of vesting
  src/interfaces/erc20/IERC20.sol::58 => * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729

Tools Used

None

Recommended Mitigation Steps

A division/multiplication by any number x being a power of 2 can be calculated by shifting log2(x) to the right/left.

C4-009: > 0 can be replaced with != 0 for gas optimization

Impact

!= 0 is a cheaper operation compared to > 0, when dealing with uint.

Proof of Concept

1. Navigate to the following contracts.

  src/CitadelMinter.sol::270 => } else if (_weight > 0) {
  src/CitadelMinter.sol::343 => require(length > 0, "CitadelMinter: no funding pools");
  src/Funding.sol::170 => require(_assetAmountIn > 0, "_assetAmountIn must not be 0");
  src/Funding.sol::209 => if (funding.discount > 0) {
  src/Funding.sol::322 => require(amount > 0, "nothing to sweep");
  src/Funding.sol::340 => require(amount > 0, "nothing to claim");
  src/Funding.sol::424 => require(_citadelPriceInAsset > 0, "citadel price must not be zero");
  src/Funding.sol::452 => require(_citadelPriceInAsset > 0, "citadel price must not be zero");
  src/KnightingRound.sol::125 => _saleDuration > 0,
  src/KnightingRound.sol::129 => _tokenOutPrice > 0,
  src/KnightingRound.sol::172 => require(_tokenInAmount > 0, "_tokenInAmount should be > 0");
  src/KnightingRound.sol::184 => if (boughtAmountTillNow > 0) {
  src/KnightingRound.sol::215 => require(tokenOutAmount_ > 0, "nothing to claim");
  src/KnightingRound.sol::313 => _saleDuration > 0,
  src/KnightingRound.sol::332 => _tokenOutPrice > 0,
  src/KnightingRound.sol::411 => require(amount > 0, "nothing to sweep");
  src/StakedCitadel.sol::835 => if(_fee > 0) {
  src/StakedCitadel.sol::908 => uint256 management_fee = managementFee > 0
  src/StakedCitadelVester.sol::138 => require(_amount > 0, "StakedCitadelVester: cannot vest 0");
  src/SupplySchedule.sol::61 => globalStartTimestamp > 0,
  src/SupplySchedule.sol::91 => cachedGlobalStartTimestamp > 0,
  src/SupplySchedule.sol::180 => globalStartTimestamp > 0,

Tools Used

Code Review

Recommended Mitigation Steps

Use "!=0" instead of ">0" for the gas optimization.

C4-0010 : Free gas savings for using solidity 0.8.10+

Impact

Using newer compiler versions and the optimizer gives gas optimizations and additional safety checks are available for free.

Proof of Concept

  src/CitadelToken.sol::2 => pragma solidity ^0.8.0;
  src/GlobalAccessControl.sol::3 => pragma solidity ^0.8.0;

Solidity 0.8.10 has a useful change which reduced gas costs of external calls which expect a return value: https://blog.soliditylang.org/2021/11/09/solidity-0.8.10-release-announcement/

Code Generator: Skip existence check for external contract if return data is expected. In this case, the ABI decoder will revert if the contract does not exist

All Contracts

Tools Used

None

Recommended Mitigation Steps

Consider to upgrade pragma to at least 0.8.10.

C4-011: > 0 can be replaced with != 0 for gas optimization

Impact

From Pragma 0.8.0, ABI coder v2 is activated by default. The pragma abicoder v2 can be deleted from the repository. That will provide gas optimization.

Proof of Concept

1. Navigate to the following code section.

""" https://github.com/code-423n4/2022-04-badger-citadel/blob/main/src/GlobalAccessControl.sol#L4 """

Tools Used

None

Recommended Mitigation Steps

ABI coder v2 is activated by default. It is recommended to delete redundant codes.

From Solidity v0.8.0 Breaking Changes https://docs.soliditylang.org/en/v0.8.0/080-breaking-changes.html