Submission Details
Impact:
Likelihood:
No Rate Limiting
Summary
The GetWeather.js file lacks mechanisms to handle API rate limiting or throttling, which could be an issue if many NFTs are updated in a short period.
Vulnerability Details
The code in GetWeather.js makes direct API calls to OpenWeatherMap without any rate limiting considerations:
const geoCodingRequest = Functions.makeHttpRequest({
url: "http://api.openweathermap.org/geo/1.0/zip",
method: "GET",
params: { zip: `${args[0]},${args[1]}`, appid: secrets.apiKey }
});
const weatherRequest = Functions.makeHttpRequest({
url: "https://api.openweathermap.org/data/2.5/weather",
method: "GET",
params: { lat: geoCodingResponse.data.lat, lon: geoCodingResponse.data.lon, appid: secrets.apiKey }
});
If many NFTs are updated simultaneously or in rapid succession, this could exceed OpenWeatherMap's API rate limits, leading to failed requests and NFTs not updating properly.
Proof of Concept
// SPDX-License-Identifier: MIT
// This is a JavaScript test file that demonstrates the rate limiting issues in GetWeather.js
// Mock the Chainlink Functions environment
const Functions = {
makeHttpRequest: async (params) => {
// Track API calls to simulate rate limiting
apiCallCount++;
// Simulate rate limiting after a certain number of calls
if (apiCallCount > RATE_LIMIT_THRESHOLD) {
return {
error: {
status: 429,
statusText: "Too Many Requests",
message: "API rate limit exceeded. Please wait before making further requests."
}
};
}
// Normal response for successful calls
if (params.url.includes("geo/1.0/zip")) {
return {
data: {
lat: 40.7128,
lon: -74.0060
}
};
} else if (params.url.includes("data/2.5/weather")) {
return {
data: {
weather: [
{
id: 800
}
],
main: {
temp: 20
}
}
};
}
}
};
// Import the GetWeather function (simplified version for testing)
const getWeather = (args, secrets) => {
return new Promise(async (resolve) => {
try {
// Get location data - no rate limiting consideration
const geoCodingRequest = await Functions.makeHttpRequest({
url: "http://api.openweathermap.org/geo/1.0/zip",
method: "GET",
params: { zip: `${args[0]},${args[1]}`, appid: secrets.apiKey }
});
if (geoCodingRequest.error) {
throw Error("Request failed, try checking the params provided");
}
// Get weather data - no rate limiting consideration
const weatherRequest = await Functions.makeHttpRequest({
url: "https://api.openweathermap.org/data/2.5/weather",
method: "GET",
params: {
lat: geoCodingRequest.data.lat,
lon: geoCodingRequest.data.lon,
appid: secrets.apiKey
}
});
if (weatherRequest.error) {
throw Error("Request failed, try checking the params provided");
}
// Extract weather ID and map to enum
const weather_id = weatherRequest.data.weather[0].id;
const weather_id_x = Math.floor(weather_id / 100);
let weather_enum;
// Weather mapping logic
if (weather_id_x === 2) weather_enum = 3;
else if (weather_id_x === 3 || weather_id_x === 5) weather_enum = 2;
else if (weather_id_x === 6) weather_enum = 5;
else if (weather_id === 800) weather_enum = 0;
else if (weather_id_x === 8) weather_enum = 1;
else weather_enum = 4;
// Return the result
resolve([weather_enum, Math.round(weatherRequest.data.main.temp)]);
} catch (error) {
console.error("Error in getWeather:", error.message);
resolve([0, 0]); // Default to SUNNY and 0 temperature on error
}
});
};
// Improved version with rate limiting consideration
const getWeatherWithRateLimiting = (args, secrets) => {
return new Promise(async (resolve) => {
try {
// Implement rate limiting with exponential backoff
const makeRateLimitedRequest = async (requestFn, retryCount = 0) => {
try {
// Add delay based on retry count (exponential backoff)
if (retryCount > 0) {
const backoffTime = Math.min(1000 * Math.pow(2, retryCount - 1), MAX_BACKOFF_TIME);
await new Promise(resolve => setTimeout(resolve, backoffTime));
console.log(`Retrying after ${backoffTime}ms backoff (attempt ${retryCount})`);
}
const response = await requestFn();
// Handle rate limiting errors
if (response.error && response.error.status === 429) {
if (retryCount < MAX_RETRY_ATTEMPTS) {
console.log("Rate limit exceeded, retrying with backoff...");
return await makeRateLimitedRequest(requestFn, retryCount + 1);
} else {
throw new Error("Rate limit exceeded and max retry attempts reached");
}
}
return response;
} catch (error) {
if (retryCount < MAX_RETRY_ATTEMPTS) {
console.log(`Request failed, retrying (attempt ${retryCount + 1})...`);
return await makeRateLimitedRequest(requestFn, retryCount + 1);
} else {
throw error;
}
}
};
// Get location data with rate limiting
const geoCodingRequest = await makeRateLimitedRequest(() =>
Functions.makeHttpRequest({
url: "http://api.openweathermap.org/geo/1.0/zip",
method: "GET",
params: { zip: `${args[0]},${args[1]}`, appid: secrets.apiKey }
})
);
if (geoCodingRequest.error) {
throw Error(`Geocoding request failed: ${geoCodingRequest.error.message}`);
}
// Get weather data with rate limiting
const weatherRequest = await makeRateLimitedRequest(() =>
Functions.makeHttpRequest({
url: "https://api.openweathermap.org/data/2.5/weather",
method: "GET",
params: {
lat: geoCodingRequest.data.lat,
lon: geoCodingRequest.data.lon,
appid: secrets.apiKey
}
})
);
if (weatherRequest.error) {
throw Error(`Weather request failed: ${weatherRequest.error.message}`);
}
// Extract weather ID and map to enum
const weather_id = weatherRequest.data.weather[0].id;
const weather_id_x = Math.floor(weather_id / 100);
let weather_enum;
// Weather mapping logic
if (weather_id_x === 2) weather_enum = 3;
else if (weather_id_x === 3 || weather_id_x === 5) weather_enum = 2;
else if (weather_id_x === 6) weather_enum = 5;
else if (weather_id === 800) weather_enum = 0;
else if (weather_id_x === 8) weather_enum = 1;
else weather_enum = 4;
// Return the result
resolve([weather_enum, Math.round(weatherRequest.data.main.temp)]);
} catch (error) {
console.error("Error in getWeatherWithRateLimiting:", error.message);
resolve([0, 0]); // Default to SUNNY and 0 temperature on error
}
});
};
// Test cases to demonstrate the issue
async function runTests() {
const secrets = { apiKey: "mock_api_key" };
console.log("Testing Rate Limiting Issues in GetWeather.js:");
// Test case 1: Simulate multiple NFT updates in rapid succession
console.log("\nTest Case 1: Multiple NFT Updates (Original Implementation)");
// Reset API call counter
apiCallCount = 0;
// Simulate 20 NFT updates in rapid succession
const results1 = [];
const locations = [
["10001", "US"], // NYC
["90210", "US"], // Beverly Hills
["60601", "US"], // Chicago
["02108", "US"], // Boston
["33101", "US"] // Miami
];
console.log("Simulating 20 NFT updates with original implementation...");
// Process 5 locations, 4 times each (total 20 requests)
for (let i = 0; i < 4; i++) {
for (const location of locations) {
try {
const result = await getWeather(location, secrets);
results1.push({ location, result, success: true });
} catch (error) {
results1.push({ location, error: error.message, success: false });
}
}
}
// Count successful and failed requests
const successful1 = results1.filter(r => r.success).length;
const failed1 = results1.filter(r => !r.success).length;
console.log(`Results: ${successful1} successful requests, ${failed1} failed requests`);
console.log(`Rate limit exceeded after ${RATE_LIMIT_THRESHOLD} requests`);
// Test case 2: Same test with improved implementation
console.log("\nTest Case 2: Multiple NFT Updates (Improved Implementation)");
// Reset API call counter
apiCallCount = 0;
// Simulate 20 NFT updates with rate limiting
const results2 = [];
console.log("Simulating 20 NFT updates with rate limiting implementation...");
// Process 5 locations, 4 times each (total 20 requests)
for (let i = 0; i < 4; i++) {
for (const location of locations) {
try {
const result = await getWeatherWithRateLimiting(location, secrets);
results2.push({ location, result, success: true });
} catch (error) {
results2.push({ location, error: error.message, success: false });
}
}
}
// Count successful and failed requests
const successful2 = results2.filter(r => r.success).length;
const failed2 = results2.filter(r => !r.success).length;
console.log(`Results: ${successful2} successful requests, ${failed2} failed requests`);
console.log(`Rate limiting with backoff strategy helped handle the rate limit threshold`);
// Compare results
console.log("\nComparison:");
console.log(`Original implementation: ${successful1}/${results1.length} successful (${Math.round(successful1/results1.length*100)}%)`);
console.log(`Improved implementation: ${successful2}/${results2.length} successful (${Math.round(successful2/results2.length*100)}%)`);
}
// Global variables for testing
let apiCallCount = 0;
const RATE_LIMIT_THRESHOLD = 10; // Simulate rate limit after 10 requests
const MAX_RETRY_ATTEMPTS = 3;
const MAX_BACKOFF_TIME = 8000; // 8 seconds max backoff
// Run the tests
runTests();
This PoC demonstrates the issues with the lack of rate limiting consideration in GetWeather.js:
-
The original implementation makes API calls without any rate limiting or backoff strategy:
It sends requests as fast as possible without considering API rate limits
Once the rate limit is exceeded (after 10 requests in this simulation), all subsequent requests fail
This results in many NFTs not being updated properly
-
The improved implementation includes rate limiting and exponential backoff:
It detects rate limit errors (HTTP 429) and implements a retry strategy
It uses exponential backoff to space out requests and avoid hitting rate limits
It successfully processes more requests by handling rate limiting gracefully
The PoC shows how implementing proper rate limiting and backoff strategies can significantly improve the reliability of the system when updating multiple NFTs in a short period.
Impact
The lack of rate limiting consideration could lead to:
API rate limit exceeded errors
Failed weather updates for NFTs
Potential service disruption for all users
Increased costs if using a paid API plan with overage charges
Tools Used
Manual code review
API integration best practices analysis
Recommendations
Implement rate limiting and backoff strategies:
// Track request timestamps and implement exponential backoff
let lastRequestTime = 0;
const MIN_REQUEST_INTERVAL = 1000; // 1 second minimum between requests
async function makeRateLimitedRequest(requestFn) {
const now = Date.now();
const timeElapsed = now - lastRequestTime;
if (timeElapsed < MIN_REQUEST_INTERVAL) {
// Wait for the remaining time before making the request
const waitTime = MIN_REQUEST_INTERVAL - timeElapsed;
await new Promise(resolve => setTimeout(resolve, waitTime));
}
lastRequestTime = Date.now();
return await requestFn();
}
// Use the rate-limited function for API calls
const geoCodingResponse = await makeRateLimitedRequest(() =>
Functions.makeHttpRequest({
url: "http://api.openweathermap.org/geo/1.0/zip",
method: "GET",
params: { zip: `${args[0]},${args[1]}`, appid: secrets.apiKey }
})
);
-
Consider implementing a batching mechanism in the smart contract to update multiple NFTs with a single API call when possible.
-
Add error handling specifically for rate limit errors, with appropriate retry logic.
Rewards breakdown
nSLOC
236This contest has a flat reward structure with the following payouts:
100 EXP
20 EXP
2 EXP
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