Defuse Protocol: Fixing Fee Quote Vulnerability

by SLV Team 48 views

Hey guys! Let's dive into a critical issue within the Defuse Protocol's getFeeQuote function, specifically within the sdk-monorepo. This is super important because it directly impacts how fees are calculated, and, as we'll see, an oversight could lead to some serious problems. We're talking about missing price validation, which, if left unchecked, can lead to undefined behavior when the external price API throws back invalid data. I know, it sounds a little techy, but trust me, we'll break it down so it's easy to grasp. We're also going to talk about price validation and how it can save the day.

The Heart of the Problem: getFeeQuote and Price Data

Alright, so the core problem lies within the getFeeQuote function, which you can find in src/lib/estimate-fee.ts. The main job of this function is to, you guessed it, estimate fees. It does this by pulling in price data from external APIs, crunching some numbers, and spitting out a fee quote. Now, here's where things get interesting, and potentially problematic. The function uses price data from a source called tokensUsdPricesHttpClient. The function then performs BigInt arithmetic to calculate the fee. If the data is invalid, it can cause problems. It is the responsibility of the code to make sure that the price data is valid.

Specifically, the issue surfaces in the fallback calculation logic. This is where the function steps in to figure things out when the primary methods fail. Lines 69-78 are where the magic happens, but also where the risk resides. This is because USD prices are directly used in BigInt operations without any prior validation.

Let's take a look at the vulnerable code. Note the lack of price validation before the calculations. The lack of validation is the crux of the issue:

const feePriceScaled = BigInt(Math.round(feeAssetPrice.price * USD_SCALE));
const tokenPriceScaled = BigInt(Math.round(tokenAssetPrice.price * USD_SCALE));
// ...
const num = feeAmount * feePriceScaled * 12n * 10n ** tokenDecimals;
const den = tokenPriceScaled * 10n ** feeDecimals * 10n;
let exactAmountIn = num / den; // Possible Division by zero when tokenPriceScaled = 0

In this example, the code grabs the price data, scales it up, and then starts multiplying and dividing with BigInt. The problem? If tokenPriceScaled ends up being zero (maybe because the API returned an invalid price), then the code will try to divide by zero. And as we all know, dividing by zero is a big no-no, which will result in an unhandled exception.

Think about it like this: the getFeeQuote function is essentially a financial calculator. If the calculator receives bad input (invalid prices), it can give you a completely wrong answer or, even worse, crash the whole system.

The Risks: What Could Go Wrong?

So, what's the big deal? Why should we care about this missing price validation? Well, the consequences can be pretty significant. When the external price API returns invalid data, the function could fail, leading to:

  • Unhandled Exceptions: These can crash the application or disrupt the user experience, preventing users from getting fee quotes. That's a bad user experience. We definitely don't want that.
  • Incorrect Fee Calculations: The system might calculate fees incorrectly, leading to incorrect transaction costs. Users could end up paying way more (or potentially way less, which is also bad for the protocol). This could be devastating to the trust in the Defuse Protocol and cause a mass exodus of users, who are looking for a reliable, safe, and secure platform. Users trust the Defuse Protocol to provide accurate quotes and charge correct fees.
  • Denial-of-Service (DoS): Malicious actors could potentially exploit this vulnerability by manipulating price data, causing the getFeeQuote function to fail repeatedly and overload the system. This can be used to mount a denial of service attack.

Basically, the lack of price validation creates a potential vulnerability that could be exploited, leading to financial losses, service disruptions, and a damaged reputation. It's like building a house without checking if the foundation is solid; it's just asking for trouble.

The Solution: Implementing Price Validation

So, how do we fix this? The answer lies in price validation. We need to make sure that the price data we're receiving from the API is actually valid before we start doing calculations with it. This is like checking your ingredients before you start baking a cake; if your ingredients are bad, your cake will be bad, no matter how good you are at baking.

Here’s how we can implement price validation within the getFeeQuote function. We need to add a function that validates the price:

const validatePrice = (price: number, fieldName: string) => {
  if (!Number.isFinite(price) || price <= 0) {
    throw new Error(`Invalid ${fieldName}: ${price}. Must be a positive finite number.`);
  }
  if (price < 1e-6) {
    throw new Error(`Price too small: ${price}. Minimum supported price is 1e-6.`);
  }
};

validatePrice(feeAssetPrice.price, 'feeAssetPrice.price');
validatePrice(tokenAssetPrice.price, 'tokenAssetPrice.price');

This validatePrice function does a couple of important checks:

  1. Is the price a finite number? The Number.isFinite() function makes sure that the price is not Infinity, -Infinity, or NaN (Not a Number). If it isn’t, then something is seriously wrong with the price data.
  2. Is the price positive? Prices should always be positive, so we make sure it's greater than 0.
  3. Is the price big enough? This could vary depending on the context, but this example checks if the price is above a minimum threshold (1e-6). This is to prevent tiny prices that could lead to other issues.

By adding this validation step, we can catch invalid price data before it gets used in calculations. If the price data fails any of these checks, the validatePrice function will throw an error, preventing the bad data from causing issues. This is a crucial step in maintaining the integrity and security of the getFeeQuote function.

Step-by-Step Implementation Guide

Let’s go through a step-by-step implementation guide of how to add this validation to the getFeeQuote function, so you can do it yourself:

  1. Locate the getFeeQuote function: Find the getFeeQuote function in the src/lib/estimate-fee.ts file within the sdk-monorepo.
  2. Identify the Price Data: Look for where feeAssetPrice.price and tokenAssetPrice.price are being used. This is where the price data from the external API comes in.
  3. Implement the validatePrice function: Copy and paste the validatePrice function (provided above) into your code. It's best to put it near the top of the file, so it's easily accessible.
  4. Add Validation Calls: Right before the lines where feeAssetPrice.price and tokenAssetPrice.price are used in BigInt operations, add calls to validatePrice. For example:
validatePrice(feeAssetPrice.price, 'feeAssetPrice.price');
validatePrice(tokenAssetPrice.price, 'tokenAssetPrice.price');
const feePriceScaled = BigInt(Math.round(feeAssetPrice.price * USD_SCALE));
  1. Test Thoroughly: Test the updated function with a variety of inputs, including valid and invalid price data. Make sure it handles invalid data gracefully and throws the expected errors.

By following these steps, you can effectively safeguard the getFeeQuote function against invalid price data and enhance the reliability and security of the Defuse Protocol.

Testing and Further Improvements

After implementing the price validation, testing is paramount. Test your fixes to make sure you have addressed all your issues.

  • Unit Tests: Create unit tests that specifically feed invalid price data to the getFeeQuote function to ensure the validation logic works as expected and throws the correct errors. Make sure you cover all the edge cases that can happen.
  • Integration Tests: Test the function within the context of the larger system to ensure that the error handling and fallback mechanisms work correctly when invalid price data is encountered.
  • Monitor External APIs: Keep an eye on the external price APIs to ensure they are functioning correctly and that the data being returned is valid. This will give you confidence that your data is always valid.

Beyond just implementing price validation, you can consider other improvements:

  • Robust Error Handling: Enhance error handling to provide more informative error messages or implement a retry mechanism to fetch price data if the initial request fails.
  • Price Feed Redundancy: Implement multiple price feeds to provide redundancy and increase the reliability of the fee calculation. Having a backup plan to always provide the correct data is always a good idea.
  • Alerting System: Set up alerts to notify you immediately if invalid price data is detected, so you can quickly address any potential issues. This can be used in your incident response.

Conclusion: Keeping it Safe

Alright, guys, there you have it. We've dug into a critical vulnerability within the Defuse Protocol and how to fix it. This fix will help keep the Defuse Protocol functioning as it should. Remember, by implementing price validation and following best practices, you can build more robust and secure systems. By taking these steps, you'll be able to improve security and the overall user experience.

So, go forth, implement this solution, and keep building awesome stuff! Thanks for reading, and happy coding!