PRBProxy

PRBProxy is a forwarding proxy that allows for the composition of Ethereum transactions on behalf of the contract owner, acting as a smart wallet that enables multiple contract calls within a single transaction. In Ethereum, externally owned accounts (EOAs) do not have this functionality because they cannot perform delegate calls.

Some key features of PRBProxy include:

• Forwards calls with DELEGATECALL.
• Uses CREATE2 to deploy the proxies at deterministic addresses.
• A unique registry system ensures that each user has a distinct proxy.
• A plugin system enables the proxy to respond to callbacks.
• An access control system permits third-party accounts (called "envoys") to call target contracts on behalf of the owner.
• Reverts with custom errors rather than reason strings for more efficient error handling.
• Comprehensive documentation via NatSpec comments.
• Developed and tested using Foundry.

Overall, PRBProxy is a powerful tool for transaction composition, providing numerous features and benefits not available through EOAs:

1. Fewer interactions: bundling multiple actions together lowers the number of protocol interactions required.
2. Modularity: establishing a clear distinction between the core business logic of your protocol and the potentially more intricate, peripheral higher-level logic.
3. Extensibility without upgradeability: users can delegate call to any arbitrary contracts, including those not even written yet.

Background

The concept of a forwarding proxy has gained popularity thanks to DappHub, the developer team behind the decentralized stablecoin DAI. DappHub created DSProxy, a widely used tool that allows for the execution of multiple contract calls in a single transaction. Major DeFi players like Maker, Balancer, and DeFi Saver all rely on DSProxy.

However, as the Ethereum ecosystem has evolved since DSProxy's launch in 2017, the tool has become outdated. With significant improvements to the Solidity compiler and new EVM OPCODES, as well as the introduction of more user-friendly development environments like Foundry, it was time for an update.

Enter PRBProxy, the modern successor to DSProxy; a "DSProxy 2.0", if you will. It improves upon DSProxy in several ways:

1. PRBProxy is deployed with CREATE2, which allows clients to pre-compute the proxy contract's address.
2. Front-running is not possible.
3. The proxy contract itself has no storage, which reduces the risk of storage collisions and malicious attacks.
4. The proxy owner is immutable, and so it cannot be changed during any DELEGATECALL.
5. PRBProxy uses high-level Solidity code that is easier to comprehend and less prone to errors.
6. PRBProxy offers more features than DSProxy, such as plugins.

Using CREATE2 eliminates the risk of a chain reorg overriding the proxy contract owner, making PRBProxy a more secure alternative to DSProxy. With DSProxy, users must wait for several blocks to be mined before assuming the contract is secure. However, PRBProxy eliminates this risk entirely, making it possible to safely send funds to the proxy before it is deployed.

Deployments

PRBProxyRegistry is deployed on 10+ chains at 0x584009E9eDe26e212182c9745F5c000191296a78. A sortable, searchable list of all available chains can be found at https://prbproxy.com/deployments. To request a deployment to a new chain, please open a GitHub issue. You can speed up the process by sending funds to cover the deploy cost to the deployer account: 0x3Afb8fEDaC6429E2165E84CC43EeA7e42e6440fF.

ABIs

The ABIs can be found on https://prbproxy.com/abi, where they can be downloaded or copied to the clipboard in various formats, including:

• Solidity interfaces
• JSON ABIs, prettified
• viem human readable ABIs

Alternatively, you can:

• Download the ABIs from the releases page
• Copy the ABIs from Etherscan
• Install Foundry and run cast interface 0x584009E9eDe26e212182c9745F5c000191296a78
• Use one of the programmatic methods described below

Install

Node.js

This is the recommended approach.

Install PRBProxy using your favorite package manager, e.g., with Bun:

bun add @prb/proxy

Then, if you are using Foundry, you need to add this to your remappings.txt file:

@prb/proxy/=node_modules/@prb/proxy/

Git Submodules

This installation method is not recommended, but it is available for those who prefer it.

First, install the submodule using Forge:

forge install --no-commit PaulRBerg/prb-proxy@release-v4

Your .gitmodules file should now contain the following entry:

[submodule "lib/prb-proxy"]
  branch = "release-v4"
  path = "lib/prb-proxy"
  url = "https://github.com/PaulRBerg/prb-proxy"

Finally, add this to your remappings.txt file:

@prb/proxy/=lib/prb-proxy/

Usage

Proxies are deployed via PRBProxyRegistry. There are multiple deploy functions available:

Function	Description
deploy	Deploy a proxy for msg.sender
deployFor	Deploy a proxy for the provided owner
deployAndExecute	Deploy a proxy for msg.sender, and delegate calls to the provided target
deployAndInstallPlugin	Deploy a proxy for msg.sender, and installs the provided plugin
deployAndExecuteAndInstall	Deploy a proxy for msg.sender, delegate calls to the provided target, and installs the provided plugin

Once the proxy is deployed, you can start interacting with target contracts by calling the execute function on the proxy by passing the ABI-encoding function signatures and data.

No Upgradeability

For the avoidance of doubt, PRBProxy is not an upgradeable proxy¹. It is a "forwarding" proxy whose sole purpose is to delegate calls to target and plugin contracts.

Both PRBProxyRegistry and PRBProxy are immutable contracts. Their source code cannot be changed once deployed.

Targets and Plugins

See this repository's wiki page for guidance on how to write targets and plugins.

Frontends

Integrating PRBProxy into a front-end app would work something like this:

1. Begin by calling the getProxy function on the registry to determine if the user already has a proxy.
2. If the user does not have a proxy, deploy one for them using one of the deploy methods outlined above.
3. Interact with your desired target contract using the execute function.
4. Install relevant plugins, which can make the proxy react to your protocol events.
5. Going forward, treat the proxy address as the user of your system.

However, this is just scratching the surface. For more examples of how to use PRBProxy in a frontend environment, check out the Frontends wiki. Additionally, Maker's developer guide, Working with DSProxy, provides an in-depth exploration of the proxy concept that can also help you understand how to use PRBProxy. Just be sure to keep in mind the differences outlined throughout this document.

Security

While I have strict standards for code quality and test coverage, and the code has been audited by third-party security researchers, using PRBProxy may not be entirely risk-free.

Caveat Emptor

Please be aware that this software is experimental and is provided on an "as is" and "as available" basis. I do not offer any warranties, and I cannot be held responsible for any direct or indirect loss resulting from the continued use of this codebase.

Contact

If you discover any bugs or security issues, please report them via Telegram.

License

This project is licensed under MIT.

Footnotes

1. The term "proxy" can refer to different concepts in Ethereum, most notably upgradeable proxies, a design popularized by OpenZeppelin that enables contract owners to upgrade the contract's logic. It's critical to note that PRBProxy does not fall under this category of upgradeable proxies. ↩