From effe6dbfd5fb640e634f005212964c525f25d77e Mon Sep 17 00:00:00 2001
From: rishab11250 <rishab.chandgothia.cg@gmail.com>
Date: Sat, 20 Jun 2026 22:42:57 +0530
Subject: [PATCH] security: add rate limiting to /api/user/:username endpoint
 (#222)

Install express-rate-limit v8.5.2 and apply a rate limiter (30 req/min per IP, configurable via API_RATE_LIMIT env var) to the API endpoint. Also sets trust proxy for correct client IP detection behind Render.com's reverse proxy. Returns Retry-After header and JSON error on 429.
---
 package-lock.json | 28 ++++++++++++++++++++++++++++
 package.json      |  1 +
 server.js         | 20 ++++++++++++++++++++
 3 files changed, 49 insertions(+)

diff --git a/package-lock.json b/package-lock.json
index 3d201b72..adf840be 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -12,6 +12,7 @@
         "axios": "^1.10.0",
         "cors": "^2.8.5",
         "express": "^5.1.0",
+        "express-rate-limit": "^8.5.2",
         "helmet": "^8.2.0"
       },
       "devDependencies": {
@@ -374,6 +375,24 @@
         "url": "https://opencollective.com/express"
       }
     },
+    "node_modules/express-rate-limit": {
+      "version": "8.5.2",
+      "resolved": "https://registry.npmjs.org/express-rate-limit/-/express-rate-limit-8.5.2.tgz",
+      "integrity": "sha512-5Kb34ipNX694DH48vN9irak1Qx30nb0PLYHXfJgw4YEjiC3ZEmZJhwOp+VfiCYwFzvFTdB9QkArYS5kXa2cx2A==",
+      "license": "MIT",
+      "dependencies": {
+        "ip-address": "^10.2.0"
+      },
+      "engines": {
+        "node": ">= 16"
+      },
+      "funding": {
+        "url": "https://github.com/sponsors/express-rate-limit"
+      },
+      "peerDependencies": {
+        "express": ">= 4.11"
+      }
+    },
     "node_modules/express/node_modules/mime-db": {
       "version": "1.54.0",
       "resolved": "https://registry.npmjs.org/mime-db/-/mime-db-1.54.0.tgz",
@@ -630,6 +649,15 @@
       "integrity": "sha512-k/vGaX4/Yla3WzyMCvTQOXYeIHvqOKtnqBduzTHpzpQZzAskKMhZ2K+EnBiSM9zGSoIFeMpXKxa4dYeZIQqewQ==",
       "license": "ISC"
     },
+    "node_modules/ip-address": {
+      "version": "10.2.0",
+      "resolved": "https://registry.npmjs.org/ip-address/-/ip-address-10.2.0.tgz",
+      "integrity": "sha512-/+S6j4E9AHvW9SWMSEY9Xfy66O5PWvVEJ08O0y5JGyEKQpojb0K0GKpz/v5HJ/G0vi3D2sjGK78119oXZeE0qA==",
+      "license": "MIT",
+      "engines": {
+        "node": ">= 12"
+      }
+    },
     "node_modules/ipaddr.js": {
       "version": "1.9.1",
       "resolved": "https://registry.npmjs.org/ipaddr.js/-/ipaddr.js-1.9.1.tgz",
diff --git a/package.json b/package.json
index d22495e7..96c1430b 100644
--- a/package.json
+++ b/package.json
@@ -23,6 +23,7 @@
     "axios": "^1.10.0",
     "cors": "^2.8.5",
     "express": "^5.1.0",
+    "express-rate-limit": "^8.5.2",
     "helmet": "^8.2.0"
   },
   "devDependencies": {
diff --git a/server.js b/server.js
index 7d1be02a..8ab527e7 100644
--- a/server.js
+++ b/server.js
@@ -5,12 +5,16 @@ const path = require("path");
 const fs = require("fs");
 const crypto = require("crypto");
 const fetchUserInfo = require("./scripts/fetch-user-info");
+const { rateLimit } = require("express-rate-limit");
 
 const app = express();
 const PORT = process.env.PORT || 3000;
 
 app.use(cors());
 
+// Trust Render.com proxy so req.ip returns real client IP
+app.set("trust proxy", 1);
+
 // 1. Per-request nonce generator (used by CSP and HTML nonce injection)
 app.use((req, res, next) => {
   res.locals.nonce = crypto.randomBytes(16).toString("base64url");
@@ -124,6 +128,22 @@ app.get("/user/:username", (req, res) => {
   serveHtml(res, path.join(__dirname, "frontend", "user.html"));
 });
 
+// ---- Rate limiter for API endpoint ----
+const apiLimiter = rateLimit({
+  windowMs: 60 * 1000, // 1-minute window
+  limit: parseInt(process.env.API_RATE_LIMIT, 10) || 30,
+  standardHeaders: "draft-8",
+  legacyHeaders: false,
+  message: { error: "Rate limit exceeded", retryAfter: 60 },
+  handler: (req, res, next, options) => {
+    res.status(options.statusCode);
+    res.set("Retry-After", Math.ceil(options.windowMs / 1000));
+    res.json(options.message);
+  },
+});
+
+app.use("/api/user/:username", apiLimiter);
+
 app.get("/api/user/:username", async (req, res) => {
   const username = req.params.username;