- implement test for onBehalfOf flashloan borrow debt

contracts/interfaces/ILendingPool.sol

@@ -99,6 +99,8 @@ interface ILendingPool {
   /**
    * @dev emitted when a flashloan is executed
    * @param target the address of the flashLoanReceiver
+   * @param mode Type of the debt to open if the flash loan is not returned. 0 -> Don't open any debt, just revert, 1 -> stable, 2 -> variable
+   * @param onBehalfOf the address incurring the debt, if borrow mode is not 0
    * @param assets the address of the assets being flashborrowed
    * @param amounts the amount requested
    * @param premiums the total fee on the amount
@@ -107,6 +109,7 @@ interface ILendingPool {
   event FlashLoan(
     address indexed target,
     uint256 mode,
+    address indexed onBehalfOf,
     address[] assets,
     uint256[] amounts,
     uint256[] premiums,

contracts/lendingpool/LendingPool.sol

@@ -503,7 +503,7 @@ contract LendingPool is VersionedInitializable, ILendingPool, LendingPoolStorage
    * @param assets The addresss of the assets being flashborrowed
    * @param amounts The amounts requested for this flashloan for each asset
    * @param mode Type of the debt to open if the flash loan is not returned. 0 -> Don't open any debt, just revert, 1 -> stable, 2 -> variable
-   * @param onBehalfOf If mode is not 0, then the address to take the debt onBehalfOf. The address must already have approved `msg.sender` to incur the debt on their behalf.
+   * @param onBehalfOf If mode is not 0, then the address to take the debt onBehalfOf. The onBehalfOf address must already have approved `msg.sender` to incur the debt on their behalf.
    * @param params Variadic packed params to pass to the receiver as extra information
    * @param referralCode Referral code of the flash loan
    **/
@@ -570,6 +570,16 @@ contract LendingPool is VersionedInitializable, ILendingPool, LendingPoolStorage
           vars.currentAmountPlusPremium
         );
       } else {
+        if (msg.sender != onBehalfOf) {
+          address debtToken = _reserves[vars.currentAsset].getDebtTokenAddress(mode);
+
+          _borrowAllowance[debtToken][onBehalfOf][msg
+            .sender] = _borrowAllowance[debtToken][onBehalfOf][msg.sender].sub(
+            vars.currentAmount,
+            Errors.BORROW_ALLOWANCE_ARE_NOT_ENOUGH
+          );
+        }
+
         //if the user didn't choose to return the funds, the system checks if there
         //is enough collateral and eventually open a position
         _executeBorrow(
@@ -585,7 +595,7 @@ contract LendingPool is VersionedInitializable, ILendingPool, LendingPoolStorage
           )
         );
       }
-      emit FlashLoan(receiverAddress, mode, assets, amounts, premiums, referralCode);
+      emit FlashLoan(receiverAddress, mode, onBehalfOf, assets, amounts, premiums, referralCode);
     }
   }
 

helpers/types.ts

@@ -89,6 +89,7 @@ export enum ProtocolErrors {
   REQUESTED_AMOUNT_TOO_SMALL = '25', // 'The requested amount is too small for a FlashLoan.'
   INCONSISTENT_PROTOCOL_ACTUAL_BALANCE = '26', // 'The actual balance of the protocol is inconsistent'
   CALLER_NOT_LENDING_POOL_CONFIGURATOR = '27', // 'The actual balance of the protocol is inconsistent'
+  BORROW_ALLOWANCE_ARE_NOT_ENOUGH = '54', // User borrows on behalf, but allowance are too small
   INVALID_FLASH_LOAN_EXECUTOR_RETURN = '60', // The flash loan received returned 0 (EOA)
 
   // require error messages - aToken

test/flashloan.spec.ts

@@ -25,6 +25,7 @@ makeSuite('LendingPool FlashLoan function', (testEnv: TestEnv) => {
     SAFEERC20_LOWLEVEL_CALL,
     IS_PAUSED,
     INVALID_FLASH_LOAN_EXECUTOR_RETURN,
+    BORROW_ALLOWANCE_ARE_NOT_ENOUGH,
   } = ProtocolErrors;
 
   before(async () => {
@@ -113,7 +114,7 @@ makeSuite('LendingPool FlashLoan function', (testEnv: TestEnv) => {
           [weth.address],
           [ethers.utils.parseEther('0.8')],
           0,
-          _mockFlashLoanReceiver.address,
+          caller.address,
           '0x10',
           '0'
         )
@@ -134,7 +135,7 @@ makeSuite('LendingPool FlashLoan function', (testEnv: TestEnv) => {
           [weth.address],
           [ethers.utils.parseEther('0.8')],
           0,
-          _mockFlashLoanReceiver.address,
+          caller.address,
           '0x10',
           '0'
         )
@@ -155,7 +156,7 @@ makeSuite('LendingPool FlashLoan function', (testEnv: TestEnv) => {
           [weth.address],
           [ethers.utils.parseEther('0.8')],
           4,
-          _mockFlashLoanReceiver.address,
+          caller.address,
           '0x10',
           '0'
         )
@@ -297,7 +298,7 @@ makeSuite('LendingPool FlashLoan function', (testEnv: TestEnv) => {
           [usdc.address],
           [flashloanAmount],
           2,
-          _mockFlashLoanReceiver.address,
+          caller.address,
           '0x10',
           '0'
         )
@@ -358,7 +359,15 @@ makeSuite('LendingPool FlashLoan function', (testEnv: TestEnv) => {
     await expect(
       pool
         .connect(caller.signer)
-        .flashLoan(_mockFlashLoanReceiver.address, [weth.address], [flashAmount], 0, _mockFlashLoanReceiver.address, '0x10', '0')
+        .flashLoan(
+          _mockFlashLoanReceiver.address,
+          [weth.address],
+          [flashAmount],
+          0,
+          caller.address,
+          '0x10',
+          '0'
+        )
     ).to.be.revertedWith(SAFEERC20_LOWLEVEL_CALL);
   });
 
@@ -373,7 +382,15 @@ makeSuite('LendingPool FlashLoan function', (testEnv: TestEnv) => {
 
     await pool
       .connect(caller.signer)
-      .flashLoan(_mockFlashLoanReceiver.address, [weth.address], [flashAmount], 1, caller.address, '0x10', '0');
+      .flashLoan(
+        _mockFlashLoanReceiver.address,
+        [weth.address],
+        [flashAmount],
+        1,
+        caller.address,
+        '0x10',
+        '0'
+      );
 
     const {stableDebtTokenAddress} = await helpersContract.getReserveTokensAddresses(weth.address);
 
@@ -386,4 +403,82 @@ makeSuite('LendingPool FlashLoan function', (testEnv: TestEnv) => {
 
     expect(callerDebt.toString()).to.be.equal('800000000000000000', 'Invalid user debt');
   });
+
+  it('Caller takes a WETH flashloan with mode = 1 onBehalfOf user without allowance', async () => {
+    const {dai, pool, weth, users, helpersContract} = testEnv;
+
+    const caller = users[5];
+    const onBehalfOf = users[4];
+
+    // Deposit 1000 dai for onBehalfOf user
+    await dai.connect(onBehalfOf.signer).mint(await convertToCurrencyDecimals(dai.address, '1000'));
+
+    await dai.connect(onBehalfOf.signer).approve(pool.address, APPROVAL_AMOUNT_LENDING_POOL);
+
+    const amountToDeposit = await convertToCurrencyDecimals(dai.address, '1000');
+
+    await pool
+      .connect(onBehalfOf.signer)
+      .deposit(dai.address, amountToDeposit, onBehalfOf.address, '0');
+
+    const flashAmount = ethers.utils.parseEther('0.8');
+
+    await _mockFlashLoanReceiver.setFailExecutionTransfer(true);
+
+    await expect(
+      pool
+        .connect(caller.signer)
+        .flashLoan(
+          _mockFlashLoanReceiver.address,
+          [weth.address],
+          [flashAmount],
+          1,
+          onBehalfOf.address,
+          '0x10',
+          '0'
+        )
+    ).to.be.revertedWith(BORROW_ALLOWANCE_ARE_NOT_ENOUGH);
+  });
+
+  it('Caller takes a WETH flashloan with mode = 1 onBehalfOf user with allowance. A loan for onBehalfOf is creatd.', async () => {
+    const {dai, pool, weth, users, helpersContract} = testEnv;
+
+    const caller = users[5];
+    const onBehalfOf = users[4];
+
+    const flashAmount = ethers.utils.parseEther('0.8');
+
+    // Deposited for onBehalfOf user already, delegate borrow allowance
+    await pool
+      .connect(onBehalfOf.signer)
+      .delegateBorrowAllowance(weth.address, caller.address, 1, flashAmount);
+
+    await _mockFlashLoanReceiver.setFailExecutionTransfer(true);
+
+    await pool
+      .connect(caller.signer)
+      .flashLoan(
+        _mockFlashLoanReceiver.address,
+        [weth.address],
+        [flashAmount],
+        1,
+        onBehalfOf.address,
+        '0x10',
+        '0'
+      );
+
+    const {stableDebtTokenAddress} = await helpersContract.getReserveTokensAddresses(weth.address);
+
+    const wethDebtToken = await getContract<StableDebtToken>(
+      eContractid.VariableDebtToken,
+      stableDebtTokenAddress
+    );
+
+    const onBehalfOfDebt = await wethDebtToken.balanceOf(onBehalfOf.address);
+
+    expect(onBehalfOfDebt.toString()).to.be.equal(
+      '800000000000000000',
+      'Invalid onBehalfOf user debt'
+    );
+  });
 });