AaveBorrower

Protocol adapter enabling the FlashLoanRouter to access flash loans from Aave V3 pools

Overview

The AaveBorrower contract serves as a protocol adapter between the FlashLoanRouter’s generic interface and Aave V3’s specific flash loan mechanism. It implements Aave’s flash loan receiver interface while maintaining the router’s standardized borrowing pattern.

Contract Details

• Source: src/AaveBorrower.sol
• License: GPL-3.0-or-later
• Solidity: ^0.8.28
• Address: 0x7d9C4DeE56933151Bc5C909cfe09DEf0d315CB4A (all networks)
• Inherits: Borrower, IAaveFlashLoanReceiver

Functions

flashLoanAndCallBack

function flashLoanAndCallBack(
    address lender,
    IERC20 token,
    uint256 amount,
    bytes calldata callBackData
) external onlyRouter

Initiates a flash loan request to an Aave V3 pool. Only callable by the registered router.

Parameters:

• lender: Address of the Aave V3 Pool contract
• token: ERC-20 token to borrow
• amount: Amount of tokens to borrow
• callBackData: Data to pass back to the router unchanged

executeOperation

function executeOperation(
    address[] calldata assets,
    uint256[] calldata amounts,
    uint256[] calldata premiums,
    address initiator,
    bytes calldata params
) external returns (bool)

Aave’s callback function invoked after the flash loan funds have been transferred. Notifies the router by calling borrowerCallBack().

Parameters:

• assets: Array of borrowed token addresses
• amounts: Array of borrowed amounts
• premiums: Array of flash loan fees
• initiator: Address that initiated the flash loan
• params: Encoded callback data (passed through unchanged)

Returns: true to indicate successful execution

approve

function approve(
    IERC20 token,
    address target,
    uint256 amount
) external onlySettlementContract

Allows the settlement contract to authorize token spending during settlement. Used to approve the Aave pool for repayment.

triggerFlashLoan (internal)

function triggerFlashLoan(
    address lender,
    IERC20 token,
    uint256 amount,
    bytes calldata callBackData
) internal override

Internal implementation that constructs Aave-specific flash loan parameters and calls IAavePool.flashLoan().

Key implementation details:

• Interest rate mode is set to 0 (no debt position, must repay in same transaction)
• Referral code is set to 0 (Aave’s referral program is currently inactive)
• Assets and amounts are wrapped in single-element arrays

Execution Flow

1. Router calls flashLoanAndCallBack() on the AaveBorrower
2. AaveBorrower calls IAavePool.flashLoan() on the Aave V3 pool
3. Aave transfers the requested tokens to the AaveBorrower
4. Aave invokes executeOperation() on the AaveBorrower
5. AaveBorrower calls router.borrowerCallBack() to continue execution
6. During settlement, the settlement contract calls approve() to authorize Aave pool repayment
7. After settlement, Aave pulls the borrowed amount plus premium via transferFrom()

Repayment Model

Aave uses a “pull” repayment model:

1. Settlement approves the Aave pool to spend the borrower’s tokens
2. Aave’s flash loan mechanism calls transferFrom() to reclaim the principal plus premium
3. If the approval is insufficient or the borrower lacks funds, the transaction reverts

Always verify that the lender address is a legitimate Aave V3 Pool contract. Using an incorrect address could result in loss of funds or failed transactions.

Integration Notes

• Flash loan premiums on Aave are typically 0.05%-0.09% depending on the asset
• Premiums may vary by network and pool configuration
• Solvers must account for premiums when calculating settlement profitability
• The settlement must include an interaction to approve the Aave pool for repayment

Security

• flashLoanAndCallBack(): Only callable by the registered router
• approve(): Only callable by the settlement contract
• executeOperation(): Called by Aave within the flash loan flow
• Immutable router and settlement contract references prevent manipulation

Next Steps

ERC3156Borrower

ERC-3156 flash loan adapter

Borrower Base

Abstract base contract