BlockApex (Auditor) was contracted by Sonar(Client) for the purpose of conducting a Smart Contract Audit/Code Review. This document presents the findings of our analysis which took place on 8th September 2021.
| Name: Sonar BSC-ETH bridge |
| Auditor: Moazzam Arif | Kaif Ahmed |
| Platform: Ethereum/Solidity |
| Type of review: Bridge |
| Methods: Architecture Review, Functional Testing, Manual Review |
| Git repository: https://github.com/sonarplatform/eth_bridge/tree/4c086d33fb5cb7a04a2192d6566c7905ea3b1074 |
| White paper/ Documentation: Not provided |
| Document log: Initial Audit (08-09-2021) Final Audit (pending) |
The git-repository shared was checked for common code violations along with vulnerability-specific probing to detect major issues/vulnerabilities. Some specific checks are as follows:
| Code review | Functional review | |
| Reentrancy | Unchecked external call | Business Logics Review |
| Ownership Takeover | ERC20 API violation | Functionality Checks |
| Timestamp Dependence | Unchecked math | Access Control & Authorization |
| Gas Limit and Loops | Unsafe type inference | Escrow manipulation |
| DoS with (Unexpected) Throw | Implicit visibility level | Token Supply manipulation |
| DoS with Block Gas Limit | Deployment Consistency | Asset’s integrity |
| Transaction-Ordering Dependence | Repository Consistency | User Balances manipulation |
| Style guide violation | Data Consistency | Kill-Switch Mechanism |
| Costly Loop | Operation Trails & Event Generation |
This is a POA bridge application that provides eth to bsc and bsc to eth bridging. It allows its native tokens to be accessed on both ETH and BSC blockchains.
Steps to burn and mint (BSC => ETH):
1. User calls the burn method on BSC bridge (BSC blockchain)
2. With the burn method, tokens are transferred to the admin account
3. Transfer event is emitted on successful burn
4. Relayer listens the event and call the mint method on ETH bridge
5. With the mint method, the tokens are transferred to the user on the ethereum blockchain
For ETH => BSC similar steps are followed.
No test cases were provided, we did our own simulations.
The analysis indicates that the contracts audited are insecure..
Our team performed a technique called “Filtered Audit”, where the contract was separately audited by two individuals. After a thorough and rigorous process of manual testing, all the flags raised were iteratively reviewed and tested.
| # of issues | Severity of the risk |
| 2 | Critical Risk issue(s) |
| 0 | High Risk issue(s) |
| 1 | Medium Risk issue(s) |
| 1 | Low Risk issue(s) |
| 1 | Informatory issue(s) |
1. Anyone can lock funds of other users
If user1 wants to transfer tokens from BSC to ETH, user1 will first approve funds to the BSC bridge. Now that the user has approved his funds to the bridge contract, anyone else can call the burn method passing the address of user1, the funds of user1 have been locked by someone else.
Remedy:
Burn function contains following logic
token.transferFrom(to, address(this), AmountwithFees);
The parameter contains “to” but should contain “msg.sender”
2. Server API to mint the tokens
There is an api written in the server to mint tokens. It does not verify that the burn has been called or not. The users can mint without burning using that api.
Remedy:
User should submit proof of burn before calling the minting API
No high-risk issues were found.
1. Locking/Unlocking both side
The contract has locking and unlocking functionality on both sides. For minting it is assumed that the admin wallet should have enough token balance.
Attack scenario:
1. User 1 locks 1000 tokens on BSC bridge
2. There is not enough token balance equivalent to be given to user1 on ETH bridge
require( adminBal > amount, "insuffient funds in admin account.");
3. Now user1 can not unlock on ETH bridge
a. He will have to unlock his token again to get his funds back from BSC bridge (extra gas, because the function is not performing the intended behavior)
b. Unlocking of tokens on the same bridge is inconvenient from user’s perspective
Remedy:
Usually the lock/unlock strategy is used on one bridge and mint/burn strategy is used on the other bridge.
1. Centralization Risk
Admin wallet is a single wallet and there is high risk of centralization if the private key gets compromised.
require(admin == msg.sender, "only admin can call this");
Remedy:
Assignment of privileged roles to multi-signature wallets to prevent single point of failure due to the private key.
1. Lock pragma versions
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.
Remedy:
Lock the pragma version and also consider known bugs (https://github.com/ethereum/solidity/releases) for the compiler version that is chosen. Please refer to this doc for more details.
The smart contracts provided by the client for audit purposes have been thoroughly analyzed in compliance with the global best practices till date w.r.t cybersecurity vulnerabilities and issues in smart contract code, the details of which are enclosed in this report.
This report is not an endorsement or indictment of the project or team, and they do not in any way guarantee the security of the particular object in context. This report is not considered, and should not be interpreted as an influence, on the potential economics of the token, its sale or any other aspect of the project.
Crypto assets/tokens are results of the emerging blockchain technology in the domain of decentralized finance and they carry with them high levels of technical risk and uncertainty. No report provides any warranty or representation to any third-Party in any respect, including regarding the bug-free nature of code, the business model or proprietors of any such business model, and the legal compliance of any such business. No third-party should rely on the reports in any way, including for the purpose of making any decisions to buy or sell any token, product, service or other asset. Specifically, for the avoidance of doubt, this report does not constitute investment advice, is not intended to be relied upon as investment advice, is not an endorsement of this project or team, and it is not a guarantee as to the absolute security of the project.
Smart contracts are deployed and executed on a blockchain. The platform, its programming language, and other software related to the smart contract can have its vulnerabilities that can lead to hacks. The scope of our review is limited to a review of the Solidity code and only the Solidity code we note as being within the scope of our review within this report. The Solidity language itself remains under development and is subject to unknown risks and flaws. The review does not extend to the compiler layer, or any other areas beyond Solidity that could present security risks.
This audit cannot be considered as a sufficient assessment regarding the utility and safety of the code, bug-free status or any other statements of the contract. While we have done our best in conducting the analysis and producing this report, it is important to note that you should not rely on this report only - we recommend proceeding with several independent audits and a public bug bounty program to ensure security of smart contracts.
BlockApex (Auditor) was contracted by SONAR (Client) for the purpose of conducting a Smart Contract Audit/Code Review. This document presents the findings of our analysis which took place on 28th September 2021 .
| Name: Sonar BSC-ETH bridge v2 | |
| Auditor: Moazzam Arif | Kaif Ahmed | |
| Platform: Ethereum/Solidity | |
| Type of review: Bridge | |
| Methods: Architecture Review, Functional Testing, Computer-Aided Verification, Manual Review | |
| Git repository: https://github.com/XORD-one/sonar-bridge-contract/tree/17cb255444153945b66c5da8672f2ca06ec91efd | |
| White paper/ Documentation: Not provided | |
| Document log: Bridge v1 Audit (08-09-2021) | Bridge v2 Audit (28-09-2021)* |
The git-repository shared was checked for common code violations along with vulnerability-specific probing to detect major issues/vulnerabilities. Some specific checks are as follows:
| Code review | Functional review | |
| Reentrancy | Unchecked external call | Business Logics Review |
| Ownership Takeover | ERC20 API violation | Functionality Checks |
| Timestamp Dependence | Unchecked math | Access Control & Authorization |
| Gas Limit and Loops | Unsafe type inference | Escrow manipulation |
| DoS with (Unexpected) Throw | Implicit visibility level | Token Supply manipulation |
| DoS with Block Gas Limit | Deployment Consistency | Asset’s integrity |
| Transaction-Ordering Dependence | Repository Consistency | User Balances manipulation |
| Style guide violation | Data Consistency | Kill-Switch Mechanism |
| Costly Loop | Operation Trails & Event Generation |
This is a POA bridge application that provides ETH to BSC and BSC to ETH bridging. It allows its native tokens to be accessed on both ETH and BSC blockchains.
Steps to burn and mint (BSC => ETH):
1. User calls the burn method on BSC bridge (BSC blockchain)
2. With the burn method, tokens are transferred to the admin account
3. Transfer event is emitted on successful burn
4. Relayer listens the event and call the mint method on ETH bridge
5. With the mint method, the tokens are transferred to the user on the ethereum blockchain
For ETH => BSC similar steps are followed.
Smart contract for the native token (PING) was provided. As $PING is similar to $RFI and $SAFEMOON. So the swapping and fee distributions were primarily focused during this security assessment (as they had already been audited by Certik). Only minting and burning functionality of $ePING (ethereum representation of $PING) was considered in scope. Manual Review and Static Analysis tools were used to produce this report.
The analysis indicates that some of the functionalities in the contracts audited are not working properly.
Our team performed a technique called “Filtered Audit”, where the contract was separately audited by two individuals. After their thorough and rigorous process of manual testing, an automated review was carried out using Mythril, MythX and Slither. All the flags raised were manually reviewed and re-tested.
| # of issues | Severity of the risk |
| 0 | Critical Risk issue(s) |
| 1 | High Risk issue(s) |
| 0 | Medium Risk issue(s) |
| 1 | Low Risk issue(s) |
| 5 | Informatory issue(s) |
No issues were found
1. No Minting and Burning in ePING
File: ePING.sol
_tTotal represents the totalSupply. Initially on the second chain _tTotal is set to 0 in the constructor. _tTotal is used to calculate the currentRate and currentRate is used while transferring and burning. Setting _tTotal to zero gives math errors. While minting _rTotal is so high (~uint(0 => ~MAX value of uint256)). Adding any value to _rTotal will cause underflow.
NOTE: Please carefully set the _rTotal. Also while minting do not change the currentRate, as it will be reflected in other users’ balances
No issues were found.
1. GasFee Griefing Attack
Assuming that the relayer server (owned by the client) pays the gasFee to mint/unlock tokens on the alternate bridge. As there is no min_amount limit on bridging tokens. Consider the following Attack Scenario
Attack Scenario:
1. User deposits 0/1 wei amount of token on BscBridge.
2. Relayer server picks-up the deposit event and calls the mint function on etheremBridge.
3. User receives 0/1 wei tokens. And Relayer pays the gas.
4. As gas fees are high, we can deduce that 1 wei tokens < gasFee (paid by relayer).
Remedy:
1. Charge gas fee from the user. While bridging the tokens, mint amount - gasFeeEquivalent on alternate chain.
2. Put a minimum threshold on the amount of tokens to be bridged.
1. transactionID is used while depositing into the bridges. transactionID is not verified in the smart contracts. It is used when the deposit event is emitted. We advise you to validate transactionID at the backend (relayer servers).
2. Destination chainId should be used while depositing. This will improve user experience if multiple chains are supported for bridging in future.
3. Remove console.log from smart contract.
4. IToken.sol has a wrong implementation of interface. Use Openzeppelin’s ERC20 interface.
5. Fees are deducted on every transfer. Please make sure that the bridge addresses are excluded from the fees.
The smart contracts provided by the client for audit purposes have been thoroughly analyzed in compliance with the global best practices till date w.r.t cybersecurity vulnerabilities and issues in smart contract code, the details of which are enclosed in this report.
This report is not an endorsement or indictment of the project or team, and they do not in any way guarantee the security of the particular object in context. This report is not considered, and should not be interpreted as an influence, on the potential economics of the token, its sale or any other aspect of the project.
Crypto assets/tokens are results of the emerging blockchain technology in the domain of decentralized finance and they carry with them high levels of technical risk and uncertainty. No report provides any warranty or representation to any third-Party in any respect, including regarding the bug-free nature of code, the business model or proprietors of any such business model, and the legal compliance of any such business. No third-party should rely on the reports in any way, including for the purpose of making any decisions to buy or sell any token, product, service or other asset. Specifically, for the avoidance of doubt, this report does not constitute investment advice, is not intended to be relied upon as investment advice, is not an endorsement of this project or team, and it is not a guarantee as to the absolute security of the project.
Smart contracts are deployed and executed on a blockchain. The platform, its programming language, and other software related to the smart contract can have its vulnerabilities that can lead to hacks. The scope of our review is limited to a review of the Solidity code and only the Solidity code we note as being within the scope of our review within this report. The Solidity language itself remains under development and is subject to unknown risks and flaws. The review does not extend to the compiler layer, or any other areas beyond Solidity that could present security risks.
This audit cannot be considered as a sufficient assessment regarding the utility and safety of the code, bug-free status or any other statements of the contract. While we have done our best in conducting the analysis and producing this report, it is important to note that you should not rely on this report only - we recommend proceeding with several independent audits and a public bug bounty program to ensure security of smart contracts.
| Name: Dafi bridge (Final Audit) |
| Auditors: Moazzam Arif | Muhammad Jarir |
| Platform: Ethereum/Solidity |
| Type of review: ETH - BSC Bridge |
| Methods: Architecture Review, Functional Testing, Computer-Aided Verification, Manual Review |
| Git repository: https://github.com/DAFIProtocol/dBridge/tree/dafi-bridge-contracts |
| White paper/ Documentation: Dafi Bridge Flow Document (1).pdf |
| Document log: Initial Audit: 30th November 2021 Final Audit: 2nd December 2021 |
The git-repository shared was checked for common code violations along with vulnerability-specific probing to detect major issues/vulnerabilities. Some specific checks are as follows:
| Code review | Functional review | |
| Reentrancy | Unchecked external call | Business Logics Review |
| Ownership Takeover | ERC20 API violation | Functionality Checks |
| Timestamp Dependence | Unchecked math | Access Control & Authorization |
| Gas Limit and Loops | Unsafe type inference | Escrow manipulation |
| DoS with (Unexpected) Throw | Implicit visibility level | Token Supply manipulation |
| DoS with Block Gas Limit | Deployment Consistency | Asset’s integrity |
| Transaction-Ordering Dependence | Repository Consistency | User Balances manipulation |
| Style guide violation | Data Consistency | Kill-Switch Mechanism |
| Costly Loop | Operation Trails & Event Generation |
A detailed overview of the project can be found here:
https://blog.dafiprotocol.io/introducing-the-dbridge-testnet-c564f5b4eea2
Dafi’s “dbridge” enables users to bring their ERC-20 $DAFI tokens across from the Ethereum network to Binance Smart Chain, and vice versa, with aims of making $DAFI available on multiple high-speed and low-cost networks. As Dafi’s goal is to support every token on most chains, to launch their own dToken, it’s important that their protocol is cross-chain.
Dafi Bridge is an implementation of a generic POA Bridge. Authority is distributed among validators. Validators sign the proof-of-burn message and the user submits (to avoid gas griefing attacks) the signature on the alternate chain to claim tokens.
The codebase:
The system consists of 3 smart contracts (i.e ETH Bridge, BSC Bridge & a burnable/mintable ERC20 token representing Dafi on alternate chains)
Bridge contracts have onlyOwner modifier to set configurations (i.e adding/removing validators, minimum signers required(threshold)).
The analysis indicates that the contracts audited are working properly.
Our team performed a technique called “Filtered Audit”, where the contract was separately audited by two individuals. After their thorough and rigorous process of manual testing, no potential flags were raised.
| # of issues | Severity of the risk |
| 0 | Critical Risk issue(s) |
| 0 | High Risk issue(s) |
| 1 | Medium Risk issue(s) |
| 1 | Low Risk issue(s) |
| 3 | Informatory issue(s) |
No critical-risk issues were found in the review.
No high-risk issues were found in the review.
1. If ETHToken is changed, tokens will be locked forever in the contract
File: ETHBridgeOptimized.sol
Description:
Owner(multisig) can change the underlying ETHToken address. If there are tokens locked in the smart contract and changeToken() is called, tokens will be locked forever in the contract.
Remedy:
Remove changeToken() method from the contract. If there is a need to change the token address, a new contract can be deployed.
Status:
Fixed.
1. Unnecessary allowance check in burn/lock tokens
File: ETHBridgeOptimized.sol, BinanceBridgeOptimized.sol
Description:
if (IERC20(BSCTOKEN).allowance(msg.sender, address(this)) < amount)
revert AllowanceInsufficient(
IERC20(BSCTOKEN).allowance(msg.sender, address(this)), amount);
When burning/locking tokens, the contract checks if the msg.sender has allowed the smart contract (address(this)) to burn/lock. This check will cost extra gas. Normally these checks are used with burnFrom. There is already check placed in the burn method of dafiToken.sol
Remedy:
Remove allowance checks
Status:
Fixed.
1. Misleading variable/function names
File: ETHBridgeOptimized.sol, BinanceBridgeOptimized.sol, dafiTokenBSC.sol
function burnTokens(uint256 amount, address targetChain) external {
function lockTokens(uint256 amount, address targetChain) external {
function viewOwners(address checkAddress) external view returns (bool) //viewValidators
function burn(uint256 _value, address _beneficiary) external onlyBridge { // burnFrom
Remedy:
Our suggestion is that
1. targetChain should be recipient
2. viewOwners should be ViewValidators
2. burn should be burnFrom in dafiToken
2. Gas cost optimization while incrementing nonce
File: ETHBridgeOptimized.sol, BinanceBridgeOptimized.sol
Description:
nonceIncrement() method is used to increment a state variable nonce. Calling a function instead of directly updating the state variable will save the gas cost. Calling a function introduce JUMP opcode which has a higher gas cost
Status:
Fixed.
3. Centralization risk on minting/burning on BSC Token
Description:
onlyBridge can burn/mint tokens. Bridge address can be changed by the owner (MultiSig). There are no potential risks as long as the signers of the multisig are honest.
The smart contracts provided by the client for audit purposes have been thoroughly analyzed in compliance with the global best practices till date w.r.t cybersecurity vulnerabilities and issues in smart contract code, the details of which are enclosed in this report.
This report is not an endorsement or indictment of the project or team, and they do not in any way guarantee the security of the particular object in context. This report is not considered, and should not be interpreted as an influence, on the potential economics of the token, its sale or any other aspect of the project.
Crypto assets/tokens are results of the emerging blockchain technology in the domain of decentralized finance and they carry with them high levels of technical risk and uncertainty. No report provides any warranty or representation to any third-Party in any respect, including regarding the bug-free nature of code, the business model or proprietors of any such business model, and the legal compliance of any such business. No third-party should rely on the reports in any way, including for the purpose of making any decisions to buy or sell any token, product, service or other asset. Specifically, for the avoidance of doubt, this report does not constitute investment advice, is not intended to be relied upon as investment advice, is not an endorsement of this project or team, and it is not a guarantee as to the absolute security of the project.
Smart contracts are deployed and executed on a blockchain. The platform, its programming language, and other software related to the smart contract can have its vulnerabilities that can lead to hacks. The scope of our review is limited to a review of the Solidity code and only the Solidity code we note as being within the scope of our review within this report. The Solidity language itself remains under development and is subject to unknown risks and flaws. The review does not extend to the compiler layer, or any other areas beyond Solidity that could present security risks.
This audit cannot be considered as a sufficient assessment regarding the utility and safety of the code, bug-free status or any other statements of the contract. While we have done our best in conducting the analysis and producing this report, it is important to note that you should not rely on this report only - we recommend proceeding with several independent audits and a public bug bounty program to ensure security of smart contracts.
| Name: Polkalokr Matic Bridge (Initial Audit) |
| Auditor: Moazzam Arif | Shakieb Shaida |
| Platform: Ethereum/Solidity |
| Type of review: Polkalokr Matic Bridge |
| Methods: Architecture Review, Functional Testing, Computer-Aided Verification, Manual Review |
| Git Repository: https://github.com/XORD-one/polkalokr-migration-contracts/blob/801391bd9d968e81346b8ce6396d767ddd19c5ae/contracts/MaticBridge.sol |
| Document log: Day 1: Initial audit (21st June 2021), Day 2: Final Audit (pending) |
The git-repository shared was checked for common code violations along with vulnerability-specific probing to detect major issues/vulnerabilities. Some specific checks are as follows:
| Code review | Functional review | |
| Reentrancy | Unchecked external call | Business Logics Review |
| Ownership Takeover | ERC20 API violation | Functionality Checks |
| Timestamp Dependence | Unchecked math | Access Control & Authorization |
| Gas Limit and Loops | Unsafe type inference | Escrow manipulation |
| DoS with (Unexpected) Throw | Implicit visibility level | Token Supply manipulation |
| DoS with Block Gas Limit | Deployment Consistency | Asset’s integrity |
| Transaction-Ordering Dependence | Repository Consistency | User Balances manipulation |
| Style guide violation | Data Consistency | Kill-Switch Mechanism |
| Costly Loop | Operation Trails & Event Generation |
The analysis indicates that the contracts audited are secured and follow the best practices.
Our team performed a technique called “Filtered Audit”, where the contract was separately audited by two individuals. After their thorough and rigorous process of manual testing, an automated review was carried out using Slither, and Manticore. All the flags raised were manually reviewed and re-tested.
| # of issues | Severity of the risk |
| 0 | Critical Risk issue |
| 0 | High-Risk issue |
| 0 | Medium Risk issue |
| 1 | Low-Risk issue |
No critical issues found
No issues were found.
No issues found
1. Lock pragma versions
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.
REMEDIATION:
Lock the pragma version and also consider known bugs (https://github.com/ethereum/solidity/releases) for the compiler version that is chosen. Please refer to this doc for more details.
The smart contracts provided by the client for audit purposes have been thoroughly analyzed in compliance with the global best practices till date w.r.t cybersecurity vulnerabilities and issues in smart contract code, the details of which are enclosed in this report.
This report is not an endorsement or indictment of the project or team, and they do not in any way guarantee the security of the particular object in context. This report is not considered, and should not be interpreted as an influence, on the potential economics of the token, its sale or any other aspect of the project.
Crypto assets/tokens are results of the emerging blockchain technology in the domain of decentralized finance and they carry with them high levels of technical risk and uncertainty. No report provides any warranty or representation to any third-Party in any respect, including regarding the bug-free nature of code, the business model or proprietors of any such business model, and the legal compliance of any such business. No third-party should rely on the reports in any way, including for the purpose of making any decisions to buy or sell any token, product, service or other asset. Specifically, for the avoidance of doubt, this report does not constitute investment advice, is not intended to be relied upon as investment advice, is not an endorsement of this project or team, and it is not a guarantee as to the absolute security of the project.
Smart contracts are deployed and executed on a blockchain. The platform, its programming language, and other software related to the smart contract can have its vulnerabilities that can lead to hacks. The scope of our review is limited to a review of the Solidity code and only the Solidity code we note as being within the scope of our review within this report. The Solidity language itself remains under development and is subject to unknown risks and flaws. The review does not extend to the compiler layer, or any other areas beyond Solidity that could present security risks.
This audit cannot be considered as a sufficient assessment regarding the utility and safety of the code, bug-free status or any other statements of the contract. While we have done our best in conducting the analysis and producing this report, it is important to note that you should not rely on this report only - we recommend proceeding with several independent audits and a public bug bounty program to ensure security of smart contracts.
