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Azos Proxy

See HaiProxy.sol for more details.

1. Introduction​

The Azos Proxy contract is a powerful and flexible smart contract commonly used within the decentralized finance (DeFi) ecosystem. Its primary function is to act as an extensible, personal proxy contract that allows users to bundle multiple actions into single, atomic transactions. With Azos Proxy, users can interact with multiple smart contracts or execute complex contract calls in a secure, efficient, and modular manner.

2. Contract Details​

Proxy Accounts (SAFE Manager)​

In orther to facilitate the management of SAFEs, the protocol incorporates a SAFE Manager contract allowing a same user to control multiple SAFEs with the same collateral type. This interaction is done through an ownable proxy contract, and a SAFE Handler.

  • The user's Proxy
    • has an account in the SAFE Engine (can hold collateral and coins).
    • can create a new SAFE (deploying a new SAFE Handler) identified by an #ID (autoincremental).
    • is the owner (in the SAFE Manager) of the SAFE that's identified by the SAFE Handler.
  • The SAFE Handler
    • account that authorizes the SAFE Manager (in the SAFE Engine) to modify the SAFE in its behalf.
    • has no other functionality.
  • To deposit/withdraw collateral, the tokens are transferred from/to the user's Proxy account to/from the SAFE Handler's SAFE.
  • To generate/repay debt, the coins are transferred from/to the user's Proxy account to/from the SAFE Handler's SAFE.

Notice: Regular users may find that their coinBalance (in their proxy address) is usually 0 (or close to), as proxy interactions are designed to always use the coinBalance to mint ZAI and transfer the ERC20 to the user's address.

Key Methods:​

Owner

  • execute: Allows owner to call a specific contract (usually a library or helper contract containing business logic) and pass in encoded function arguments to execute a certain operation.

3. Key Mechanisms & Concepts​

Delegate Calls​

In the Ethereum smart contract ecosystem, a delegate call is a special type of contract invocation that allows one contract to "borrow" code from another contract, executing it as if it were part of the calling contract's own code. Unlike a regular function call, a delegate call operates within the context of the calling contract, meaning it can read and modify the calling contract's state variables.

4. Gotchas​

Dealing with Delegate Calls and ERC20 Transfers​

When using proxy contracts that rely on delegate calls, certain common actions like ERC20 token transfers require special handling. In a typical setup, if a user attempts to execute ERC20.transfer directly, aiming to transfer a balance that is attributed to the proxy, the operation will fail and the call will revert. This is because delegate calls operate in the context of the calling contract, not the called contract. In this case, the calling contract is the proxy, which doesn't hold the tokens, leading to a failed transaction.

To work around this issue, an intermediary contract can be introduced. This intermediary contract is responsible for parsing the intended action and then executing the transfer operation using a regular call, rather than a delegate call.

5. Failure Modes​