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Test edge cases
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@computerphysicslab
computerphysicslab committed Jun 1, 2021
1 parent e7e92ba commit 9835114
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4 changes: 2 additions & 2 deletions contracts/connectors/loantoken/LoanTokenLogicStandard.sol
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Expand Up @@ -343,6 +343,7 @@ contract LoanTokenLogicStandard is LoanTokenSettingsLowerAdmin {
/// @dev Compute the worth of the total deposit in loan tokens.
/// (loanTokenSent + convert(collateralTokenSent))
/// No actual swap happening here.

uint256 totalDeposit = _totalDeposit(collateralTokenAddress, collateralTokenSent, loanTokenSent);
require(totalDeposit != 0, "12");

Expand All @@ -361,7 +362,6 @@ contract LoanTokenLogicStandard is LoanTokenSettingsLowerAdmin {
sentAmounts[4] = collateralTokenSent;

_settleInterest();

(sentAmounts[1], sentAmounts[0]) = _getMarginBorrowAmountAndRate( /// borrowAmount, interestRate
leverageAmount,
sentAmounts[1] /// depositAmount
Expand Down Expand Up @@ -920,7 +920,7 @@ contract LoanTokenLogicStandard is LoanTokenSettingsLowerAdmin {

/// @dev Probably not the same due to the price difference.
if (collateralTokenAmount != collateralTokenSent) {
//scale the loan token amount accordingly, so we'll get the expected position size in the end
/// @dev Scale the loan token amount accordingly, so we'll get the expected position size in the end.
loanTokenAmount = loanTokenAmount.mul(collateralTokenAmount).div(collateralTokenSent);
}

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12 changes: 3 additions & 9 deletions contracts/testhelpers/FlashLoanMockup.sol
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Expand Up @@ -74,17 +74,11 @@ contract FlashLoanMockup is Ownable, ReentrancyGuard {
}

/// @dev Execute the callback function.
(bool success, bytes memory returnData) =
target.call(
callData
);
require(success, string (returnData));
(bool success, bytes memory returnData) = target.call(callData);
require(success, string(returnData));

/// @dev Verify return of flash loan.
require(
beforeUnderlyingBalance <= IERC20(loanTokenAddress).balanceOf(address(this)),
"flashBorrow::Flash loan not returned."
);
require(beforeUnderlyingBalance <= IERC20(loanTokenAddress).balanceOf(address(this)), "flashBorrow::Flash loan not returned.");

return returnData;
}
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136 changes: 92 additions & 44 deletions tests-js/loan-token/MintLoanAndBorrow.test.js
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Original file line number Diff line number Diff line change
Expand Up @@ -160,16 +160,16 @@ contract("LoanTokenBorrowing & MintLoanAndBorrowTest", (accounts) => {
const mintLoanAndBorrowTest = await MintLoanAndBorrowTest.new();

// Check balances
console.log("\nsov_initial_balance: " + (await SOV.balanceOf(owner)));
console.log("SOV_initial_balance: " + (await SOV.balanceOf(owner)));
/// SOV_initial_balance: 99999999999999999999999999999900000000000000000000

console.log("\nRBTC_initial_balance: " + (await RBTC.balanceOf(owner)));
console.log("RBTC_initial_balance: " + (await RBTC.balanceOf(owner)));
/// RBTC_initial_balance: 100000000000000000000000000000000000000000000000000

console.log("\nSUSD_initial_balance: " + (await SUSD.balanceOf(owner)));
console.log("SUSD_initial_balance: " + (await SUSD.balanceOf(owner)));
/// SUSD_initial_balance: 100000000000000000000000000000000000000000000000000

console.log("\nTest contract address: " + mintLoanAndBorrowTest.address);
console.log("Test contract address: " + mintLoanAndBorrowTest.address);

// Send underlying tokens SUSD to the test contract. Later it will spend those
// on hacking the lending pool.
Expand All @@ -180,14 +180,14 @@ contract("LoanTokenBorrowing & MintLoanAndBorrowTest", (accounts) => {
await RBTC.transfer(mintLoanAndBorrowTest.address, collateralTokenSent);

// Check underlying token balance of test contract.
console.log("\nSUSD balance on test contract: " + (await SUSD.balanceOf(mintLoanAndBorrowTest.address)));
console.log("SUSD balance on test contract: " + (await SUSD.balanceOf(mintLoanAndBorrowTest.address)));
/// SUSD balance on test contract: 100000000000000000000

// Check underlying token balance of test contract w/ contract function.
console.log("\nSUSD balance on test contract: " + (await mintLoanAndBorrowTest.getBalance(SUSD.address)));
console.log("SUSD balance on test contract: " + (await mintLoanAndBorrowTest.getBalance(SUSD.address)));

// Check collateral token balance of test contract.
console.log("\nRBTC balance on test contract: " + (await RBTC.balanceOf(mintLoanAndBorrowTest.address)));
console.log("RBTC balance on test contract: " + (await RBTC.balanceOf(mintLoanAndBorrowTest.address)));
/// RBTC balance on test contract: 1501350000000000

// Approve the transfer of the collateral.
Expand Down Expand Up @@ -274,33 +274,33 @@ contract("LoanTokenBorrowing & MintLoanAndBorrowTest", (accounts) => {
// **** BALANCES **** //

// Check owner balances
console.log("\nRBTC owner balance: " + (await RBTC.balanceOf(owner)));
console.log("RBTC owner balance: " + (await RBTC.balanceOf(owner)));
/// RBTC owner balance: 99999999999999999999999999999999998498650000000000

console.log("\nSUSD owner balance: " + (await SUSD.balanceOf(owner)));
console.log("SUSD owner balance: " + (await SUSD.balanceOf(owner)));
/// SUSD owner balance: 99999999999999999999999999999900000000000000000000

// Check flashLoanMockup & flashLoanAttack contract addresses.
console.log("\nflashLoanMockup contract address: " + flashLoanMockup.address);
console.log("\nflashLoanAttack contract address: " + flashLoanAttack.address);
console.log("flashLoanMockup contract address: " + flashLoanMockup.address);
console.log("flashLoanAttack contract address: " + flashLoanAttack.address);

// Check underlying token balance of flashLoanMockup contract.
console.log("\nSUSD balance on flashLoanMockup contract: " + (await SUSD.balanceOf(flashLoanMockup.address)));
console.log("SUSD balance on flashLoanMockup contract: " + (await SUSD.balanceOf(flashLoanMockup.address)));
/// SUSD balance on flashLoanMockup contract: 100000000000000000000 (hunEth)

// Check underlying token balance of flashLoanAttack contract.
console.log("\nSUSD balance on flashLoanAttack contract: " + (await SUSD.balanceOf(flashLoanAttack.address)));
console.log("SUSD balance on flashLoanAttack contract: " + (await SUSD.balanceOf(flashLoanAttack.address)));
/// SUSD balance on flashLoanAttack contract: 0

// Check collateral token balance of flashLoanMockup contract.
console.log("\nRBTC balance on flashLoanMockup contract: " + (await RBTC.balanceOf(flashLoanMockup.address)));
console.log("RBTC balance on flashLoanMockup contract: " + (await RBTC.balanceOf(flashLoanMockup.address)));
/// RBTC balance on flashLoanMockup contract: 0

// Check collateral token balance of flashLoanAttack contract.
console.log("\nRBTC balance on flashLoanAttack contract: " + (await RBTC.balanceOf(flashLoanAttack.address)));
console.log("RBTC balance on flashLoanAttack contract: " + (await RBTC.balanceOf(flashLoanAttack.address)));
/// RBTC balance on flashLoanAttack contract: 1501350000000000

// **** RUN ATTACK directly (no FL) **** //
// **** RUN ATTACK directly (no FL) **** //

// Fill it up with underlying tokens to attack directly w/o FL.
await SUSD.transfer(flashLoanAttack.address, hackAmount1);
Expand All @@ -313,7 +313,7 @@ contract("LoanTokenBorrowing & MintLoanAndBorrowTest", (accounts) => {
"Avoiding flash loan attack: several txs in same block from same account."
);

// **** RUN ATTACK through FL contract **** //
// **** RUN ATTACK through FL contract **** //

// Call the flashLoanAttack to run the attack.
await expectRevert(
Expand All @@ -331,30 +331,30 @@ contract("LoanTokenBorrowing & MintLoanAndBorrowTest", (accounts) => {

// **** SETUP LOAN POOL TO BE ALTERED, iSUSD **** //

const underlyingToken = SUSD;
// loan pool token to alter is iSUSD (loanToken)
const collateralToken = WRBTC;
const underlyingToken = SUSD;
// loan pool token to alter is iSUSD (loanToken)
const collateralToken = WRBTC;

console.log("PREPARATION");
console.log("PREPARATION");

// Amount to be sent for margin trade
loan_token_sent = oneEth; // new BN(10).pow(new BN(18));
console.log("Amount to be sent for margin trade, loan_token_sent: " + loan_token_sent);
// Amount to be sent for margin trade
loan_token_sent = oneEth; // new BN(10).pow(new BN(18));
console.log("Amount to be sent for margin trade, loan_token_sent: " + loan_token_sent);
// Amount to be sent for margin trade, loan_token_sent: 1000000000000000000 (1 Eth)

console.log("Legitimate users add liquidity to the loan token");

const baseLiquidity = loan_token_sent.mul(new BN(11)).div(new BN(10)); // loan_token_sent * 1.1
const baseLiquidity = loan_token_sent.mul(new BN(105)).div(new BN(100)); // loan_token_sent * 1.1
console.log("baseLiquidity: ", baseLiquidity.toString());
// baseLiquidity: 1100000000000000000 (1.1 SUSD)

// Give liquidity to the provider 1.
await underlyingToken.mint(accounts[1], baseLiquidity);

// Transfer liquidity (1.1 SUSD) to the loan pool.
await underlyingToken.approve(loanToken.address, baseLiquidity, {"from": accounts[1]});
await loanToken.mint(accounts[1], baseLiquidity, {"from": accounts[1]});
await underlyingToken.approve(loanToken.address, baseLiquidity, { from: accounts[1] });
await loanToken.mint(accounts[1], baseLiquidity, { from: accounts[1] });

// Set up interest rates.
var baseRate = oneEth;
var rateMultiplier = oneEth.mul(new BN(2025)).div(new BN(100)); // 20.25e18
Expand All @@ -373,7 +373,7 @@ contract("LoanTokenBorrowing & MintLoanAndBorrowTest", (accounts) => {

// Ready to transfer it to the loan pool.
await underlyingToken.approve(loanToken.address, loan_token_sent);

// Send the margin trade transaction.
var leverage_amount = oneEth;
var collateral_sent = new BN(0);
Expand All @@ -393,14 +393,14 @@ contract("LoanTokenBorrowing & MintLoanAndBorrowTest", (accounts) => {
var loan_id = args["loanId"];
var positionSize = args["positionSize"];
var loan = await sovryn.getLoan(loan_id);

// Interest paid per day is high because of high utilization rate.
console.log("Interest per day (without attack): ", loan["interestOwedPerDay"]/10**15);
expect(loan["interestOwedPerDay"]/10**15).to.equal(0.740444139368747);
console.log("Interest per day (without attack): ", loan["interestOwedPerDay"] / 10 ** 15);
expect(loan["interestOwedPerDay"] / 10 ** 15).to.equal(1.768000054768636);

// Repays the loan (so that the tokens are there to be loaned again).
await sovryn.closeWithSwap(loan_id, accounts[0], positionSize, false, "0x");

// Now do the same loan again, but use a flash loan to lower interest.

// Amount attacker will get in flash loan
Expand All @@ -418,17 +418,18 @@ contract("LoanTokenBorrowing & MintLoanAndBorrowTest", (accounts) => {
// Deposit liquidity 100 SUSD to the loan token.
await underlyingToken.approve(loanToken.address, loan_token_sent + flashLoanAmount);
await loanToken.mint(accounts[0], flashLoanAmount);

console.log("Repeating the trade but with the attack flash loan.");
/* Second time, NOT NECESSARY
/* Second time, NOT NECESSARY
// Set up interest rates.
baseRate = oneEth;
rateMultiplier = oneEth.mul(new BN(2025)).div(new BN(100)); // 20.25e18
targetLevel = oneEth.mul(new BN(80)); // 80*10**18
kinkLevel = oneEth.mul(new BN(90)); // 90*10**18
maxScaleRate = oneEth.mul(new BN(100)); // 100*10**18
await loanToken.setDemandCurve(baseRate, rateMultiplier, baseRate, rateMultiplier, targetLevel, kinkLevel, maxScaleRate);
*/
*/

borrowInterestRate = await loanToken.borrowInterestRate();
console.log("Base borrow interest rate (not adjusted by utilization): ", borrowInterestRate.div(oneEth).toString());
// Base borrow interest rate (not adjusted by utilization): 17
Expand All @@ -452,16 +453,63 @@ contract("LoanTokenBorrowing & MintLoanAndBorrowTest", (accounts) => {
loan_id = args["loanId"];
positionSize = args["positionSize"];
loan = await sovryn.getLoan(loan_id);

// Interest paid per day is lower than without flash loan.
console.log("Interest per day (with attack): ", loan["interestOwedPerDay"]/10**15);
expect(loan["interestOwedPerDay"]/10**15).to.equal(0.477533704995224);
console.log("Interest per day (with attack): ", loan["interestOwedPerDay"] / 10 ** 15);
expect(loan["interestOwedPerDay"] / 10 ** 15).to.equal(0.477533704995224);

// Conclusion:
// With low liquidity of 1.1 SUSD, trading 1 SUSD (high utilization: ~91%)
// yields a daily interest of 0.74%
// With high liquidity of 100 SUSD, trading 1 SUSD (low utilization: 1%)
// yields a daily interest of 0.47%
// Providing low liquidity of 1.1 SUSD, trading 1 SUSD (high utilization: ~91%)
// costs a daily interest of 0.74%
// Providing high liquidity of 100 SUSD, trading 1 SUSD (low utilization: 1%)
// costs a daily interest of 0.47%

/*
Profiling interest and deposit values:
104/100 (1.040 SUSD):
sentAmounts[1] = 1055799386991083000 (1.055 SUSD)
_underlyingBalance() = 1040000000000000000 (1.040 SUSD)
_borrowOrTrade::sentAmounts
borrow::
sentAmounts[1] = withdrawAmount;
borrow::withdrawAmount
marginTrade::
sentAmounts[1] = totalDeposit; /// Total amount of deposit.
uint256 totalDeposit = _totalDeposit(collateralTokenAddress, collateralTokenSent, loanTokenSent);
marginTrade::loanTokenSent
loan_token_sent = oneEth;
uint256 totalDeposit = _totalDeposit(collateralTokenAddress, collateralTokenSent, loanTokenSent);
collateralTokenSent = 0
loanTokenSent = 1000000000000000000 (1 SUSD)
totalDeposit = 1000000000000000000 (1 SUSD)
(sentAmounts[1], sentAmounts[0]) = _getMarginBorrowAmountAndRate( /// borrowAmount, interestRate
leverageAmount,
sentAmounts[1] /// depositAmount
);
depositAmount => borrowAmount
1.000 => 1.055799
So, edge case near liquidity = 1.055800
Limit point: 105/100 (1.050 SUSD):
borrowAmount = 1.049504001533521828
interest: 1.768000054768636
Conclusion:
Interest curve is not very extreme. It's value swifts around 1.76%
(higher bound) and 0.47% (lower bound) w/ liquidities ranging
from 1.050 SUSD to 100 SUSD and margin trading depositAmount of 1 SUSD.
So an attack (flash loan or not, although FL are not allowed anymore
due to check implemented on NotInTheSameBlock branch) would give
the LP an advantage of getting loans with a lower interest of
around 1.3% on most extreme case (maximum utilization of the loan pool).
*/
});
});
});

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