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| ## Advanced Analysis Report for Axelar | ||
| ### Overview | ||
| - [Axelar](https://github.com/code-423n4/2023-07-axelar/tree/main) is a decentralized network that connects various blockchain ecosystems, allowing them to interoperate and communicate with each other. It provides a platform for developers to build cross-chain applications and for users to transfer assets across different blockchains seamlessly. | ||
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| ### Understanding the Ecosystem | ||
| - [Axelar](https://github.com/code-423n4/2023-07-axelar/tree/main)'s ecosystem is composed of various smart contracts that handle different functionalities such as token deployment, flow limit management, express call handling, and more. These contracts are designed to work together to facilitate cross-chain communication and asset transfer. | ||
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| ### Codebase Quality Analysis: | ||
| - The codebase of [Axelar](https://github.com/code-423n4/2023-07-axelar/tree/main) is well-structured and modular, with each contract having a specific role in the ecosystem. The contracts are well-documented, making it easier for developers to understand their functionalities. The use of interfaces and inheritance promotes code reusability and reduces the complexity of the contracts. | ||
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| ### Architecture Recommendations: | ||
| - [Axelar](https://github.com/code-423n4/2023-07-axelar/tree/main)'s architecture is robust and efficient, but there are areas where gas optimization can be implemented, to reduce the cost of transactions. For example, using packed storage for multiple small-sized variables, reducing the number of external calls, and optimizing the use of ``SLOAD`` and ``SSTORE`` operations can significantly reduce gas costs: see my gas optimizations report for more precise details of possible optimizations. | ||
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| ### Centralization Risks: | ||
| - [Axelar](https://github.com/code-423n4/2023-07-axelar/tree/main)'s architecture is decentralized, with no single point of control or failure. However, the use of a token manager in some contracts introduces a level of centralization. It is recommended to implement mechanisms to ensure the decentralization of control, such as multi-signature wallets or decentralized governance. | ||
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| ### Mechanism Review: | ||
| - [Axelar](https://github.com/code-423n4/2023-07-axelar/tree/main) uses a variety of mechanisms to facilitate cross-chain communication and asset transfer. These include the use of proxy contracts for token deployment, flow limit management to control the rate of asset transfer, and express call handling for efficient communication between different blockchains. | ||
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| ### Systemic Risks: | ||
| - The main systemic risk in [Axelar](https://github.com/code-423n4/2023-07-axelar/tree/main)'s ecosystem is the reliance on the correct functioning of the various smart contracts. If a bug or vulnerability is found in one contract, it could potentially affect the entire ecosystem. Therefore, rigorous testing and auditing of the contracts are essential. | ||
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| ### Areas of Concern | ||
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| - The use of assembly language in some contracts can make the code difficult to read and maintain. | ||
| - The reliance on external blockchain networks could potentially introduce systemic risks. | ||
| - The use of a single contract for token deployment could potentially become a central point of failure. | ||
| - The gas costs associated with some operations, such as token deployment, could be optimized. | ||
| - The complexity of the system could potentially make it difficult to debug and troubleshoot issues. | ||
| - Potential for network congestion. | ||
| - Complexity of cross-chain communication. | ||
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| ### Codebase Analysis | ||
| - The [Axelar](https://github.com/code-423n4/2023-07-axelar/tree/main) codebase is well-structured and follows best practices for solidity development. The contracts are clearly commented, making it easy to understand the purpose and function of each contract and function. The use of interfaces and inheritance is prevalent throughout the codebase, promoting code reusability and reducing redundancy. | ||
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| ### Recommendations | ||
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| - Abstract low-level assembly operations into higher-level functions where possible. | ||
| - Consider alternative methods for deploying new token contracts to further decentralize control. | ||
| - Implement robust data validation and error handling mechanisms to mitigate the risk of inaccurate or delayed data from external networks. | ||
| - Use a more reliable source of time, such as block numbers, for flow control. | ||
| - Use libraries for common operations to reduce the size of the deployed contracts and save gas. | ||
| - Implement a layer of abstraction between the core logic and the blockchain-specific operations. | ||
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| ### Contract Details | ||
| Some of the main contracts include: | ||
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| - [FlowLimit.sol](https://github.com/code-423n4/2023-07-axelar/blob/main/contracts/its/utils/FlowLimit.sol): This contract is responsible for managing the flow limit of the token transfers within the [Axelar](https://github.com/code-423n4/2023-07-axelar/tree/main) network. It uses Solidity's assembly language for low-level storage operations, specifically the ``sload`` and ``sstore`` opcodes to read and write data to Ethereum's storage. The contract also uses the ``keccak256`` opcode for generating unique slots for each epoch. | ||
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| - [ExpressCallHandler.sol](https://github.com/code-423n4/2023-07-axelar/blob/main/contracts/its/utils/ExpressCallHandler.sol): This contract handles express calls, which are urgent transactions that need to be processed quickly. It uses assembly language for low-level storage operations, specifically the ``sload`` and ``sstore`` opcodes to read and write data to Ethereum's storage. The contract also uses the ``keccak256`` opcode for generating unique slots for each token transfer. | ||
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| - [StandardizedTokenDeployer.sol](https://github.com/code-423n4/2023-07-axelar/blob/main/contracts/its/utils/StandardizedTokenDeployer.sol): This contract is responsible for deploying new instances of the [StandardizedTokenProxy](https://github.com/code-423n4/2023-07-axelar/blob/main/contracts/its/proxies/StandardizedTokenProxy.sol) contract. It uses the Create2 opcode to create new contracts with deterministic addresses. The contract also uses the ``abi.encode`` and ``abi.encodePacked`` opcodes for encoding the ``constructor`` parameters of the new contracts. | ||
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| - [AxelarGateway.sol](https://github.com/code-423n4/2023-07-axelar/blob/main/contracts/cgp/AxelarGateway.sol): This contract serves as the entry point for token transfers. It interacts with other contracts to process transactions. It uses the ``delegatecall`` opcode to delegate function calls to other contracts, and the revert opcode to ``revert`` transactions in case of errors. | ||
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| - [Create3Deployer.sol](https://github.com/code-423n4/2023-07-axelar/blob/main/contracts/gmp-sdk/deploy/Create3Deployer.sol): This contract is used by the [StandardizedTokenDeployer.sol](https://github.com/code-423n4/2023-07-axelar/blob/main/contracts/its/utils/StandardizedTokenDeployer.sol) contract to deploy new contracts. It uses the ``Create3`` opcode to create new contracts with deterministic addresses. | ||
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| - [StandardizedTokenProxy](https://github.com/code-423n4/2023-07-axelar/blob/main/contracts/its/proxies/StandardizedTokenProxy.sol): This contract is a proxy contract that delegates all function calls to an implementation contract. It uses the ``delegatecall`` opcode to ``delegate`` function calls to the ``implementation`` contract. | ||
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| - [StandardizedTokenMintBurn.sol](https://github.com/code-423n4/2023-07-axelar/blob/main/contracts/its/token-implementations/StandardizedTokenMintBurn.sol) and [StandardizedTokenLockUnlock.sol](https://github.com/code-423n4/2023-07-axelar/blob/main/contracts/its/token-implementations/StandardizedTokenLockUnlock.sol): These contracts are the implementation contracts for the [StandardizedTokenProxy](https://github.com/code-423n4/2023-07-axelar/blob/main/contracts/its/proxies/StandardizedTokenProxy.sol) contract. They implement the functionality of the token, such as minting and burning tokens, and locking and unlocking tokens. They use the ``SLOAD`` and ``SSTORE`` opcodes for reading and writing data to Ethereum's storage, and the ``revert`` opcode to ``revert`` transactions in case of errors. | ||
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| Each of these contracts plays a crucial role in the [Axelar](https://github.com/code-423n4/2023-07-axelar/tree/main) ecosystem, and they are interconnected to ensure the smooth operation of the network. The contracts have been designed with security in mind, and potential attack vectors have been mitigated. However, the use of assembly language and the complexity of the contracts could potentially introduce unforeseen risks. | ||
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| ### Conclusion | ||
| - [Axelar](https://github.com/code-423n4/2023-07-axelar/tree/main) is a robust and innovative platform for cross-chain communication, with a well-designed architecture and a high-quality codebase. While there are a few areas where improvements could be made, overall the [Axelar](https://github.com/code-423n4/2023-07-axelar/tree/main) network represents a significant advancement in the field of blockchain interoperability. | ||
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| ### Time spent: | ||
| 20 hours |