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Contract Extensions

This repository contains smart contract extensions to be used with different smart contracts accounts, similar to those used in advanced account systems like Gnosis Safe and Universal Profiles, etc ..

Overview

Smart contract accounts often implement an extending mechanism where calls to non-existent functions are delegated to extensions using the fallback function. These extensions contain the actual logic and execute it on behalf of the main contract.

sequenceDiagram
    participant EU as External User
    participant SCA as Smart Contract Account
    participant EXT as Extension

    EU->>SCA: Call function A
    Note over SCA: Function A doesn't exist
    SCA->>EXT: Call to extension for function A
    EXT->>EXT: Execute func A
    EXT->>SCA: Return result
    SCA->>EU: Return result
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This approach is beneficial for contracts that:

  • Have logic that may change over time
  • Need to implement a large number of functions
  • Want to maintain upgradeability for specific functionalities

Use Cases

Flexible ERC721 Callbacks

Consider an ERC721 token receiver. Initially, in your GnosisSafe/UniversalProfile you might want to accept all tokens. However, later you may decide to only accept specific tokens. If this logic was implemented natively in an immutable contract, changing it would be impossible. By using extensions, you can:

  • Start with an extension that accepts all tokens
  • Later, replace it with a new extension that only accepts specific tokens

This flexibility allows for evolving logic without needing to redeploy the main contract.

Available Extensions

The extensions available are:

  • ExtERC165StorageOwnable: Extension that allows the owner of the extension to add ERC165 supported interfaces.
  • ExtERC165StorageSingleton: Extension that allows each smart contract account to add ERC165 supported interfaces, can be used as a singleton.
  • ExtERC1271Ownable: Extension that validates the signature and the hash based on whether the recovered address matches the address of the owner of the smart contract account.

More to come soon ...

Usage

Build

$ forge build

Test

$ forge test

Gas Snapshots

$ forge snapshot

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

License

MIT License