Security hardening for production readiness

- Add security headers (CSP, HSTS, X-Frame-Options, X-Content-Type-Options, etc.)
- Strengthen password requirements (10+ chars, mixed case, numbers)
- Increase shared list slug entropy from 4 to 16 bytes
- Add rate limiting to login, registration, upload, and restore endpoints
- Add file magic number validation for image uploads (JPEG, PNG, WebP, HEIC)
- Add CSV row limit (50k) to restore endpoint
- Update client-side registration form to match new password policy

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/app/(auth)/register/page.tsx

@@ -26,8 +26,13 @@ export default function RegisterPage() {
       return
     }
 
-    if (password.length < 8) {
-      setError("Password must be at least 8 characters")
+    if (password.length < 10) {
+      setError("Password must be at least 10 characters")
+      return
+    }
+
+    if (!/[a-z]/.test(password) || !/[A-Z]/.test(password) || !/[0-9]/.test(password)) {
+      setError("Password must contain lowercase, uppercase, and a number")
       return
     }
 
@@ -112,11 +117,12 @@ export default function RegisterPage() {
               <Input
                 id="password"
                 type="password"
-                placeholder="At least 8 characters"
+                placeholder="Min 10 chars, upper+lower+number"
                 value={password}
                 onChange={(e) => setPassword(e.target.value)}
                 required
-                minLength={8}
+                minLength={10}
+                maxLength={128}
                 disabled={loading}
               />
             </div>
@@ -130,7 +136,7 @@ export default function RegisterPage() {
                 value={confirmPassword}
                 onChange={(e) => setConfirmPassword(e.target.value)}
                 required
-                minLength={8}
+                minLength={10}
                 disabled={loading}
               />
             </div>

src/app/api/auth/register/route.ts

@@ -2,6 +2,7 @@ import { NextResponse } from "next/server"
 import { z } from "zod"
 import bcrypt from "bcryptjs"
 import { prisma } from "@/lib/prisma"
+import { rateLimit } from "@/lib/rate-limit"
 
 const registerSchema = z.object({
   name: z
@@ -14,11 +15,26 @@ const registerSchema = z.object({
     .email("Invalid email address"),
   password: z
     .string()
-    .min(8, "Password must be at least 8 characters"),
+    .min(10, "Password must be at least 10 characters")
+    .max(128, "Password must be 128 characters or less")
+    .regex(/[a-z]/, "Password must contain at least one lowercase letter")
+    .regex(/[A-Z]/, "Password must contain at least one uppercase letter")
+    .regex(/[0-9]/, "Password must contain at least one number"),
 })
 
 export async function POST(request: Request) {
   try {
+    // Rate limit: 5 registration attempts per IP per minute
+    const forwarded = request.headers.get("x-forwarded-for")
+    const ip = forwarded?.split(",")[0]?.trim() ?? "unknown"
+    const rl = rateLimit(`register:${ip}`, 5, 60 * 1000)
+    if (!rl.success) {
+      return NextResponse.json(
+        { error: "Too many registration attempts. Please try again later." },
+        { status: 429 }
+      )
+    }
+
     const body = await request.json()
     const result = registerSchema.safeParse(body)
 

src/app/api/settings/restore/route.ts

@@ -6,8 +6,10 @@ import {
   validateBackupData,
   executeRestore,
 } from "@/lib/backup"
+import { rateLimit } from "@/lib/rate-limit"
 
 const VALID_MODES = ["merge-skip", "merge-update", "replace"] as const
+const MAX_CSV_ROWS = 50000
 
 export async function POST(request: Request) {
   const session = await auth()
@@ -15,6 +17,15 @@ export async function POST(request: Request) {
     return NextResponse.json({ error: "Unauthorized" }, { status: 401 })
   }
 
+  // Rate limit: 3 restores per user per hour
+  const rl = rateLimit(`restore:${session.user.id}`, 3, 60 * 60 * 1000)
+  if (!rl.success) {
+    return NextResponse.json(
+      { error: "Too many restore attempts. Please try again later." },
+      { status: 429 }
+    )
+  }
+
   try {
     const formData = await request.formData()
     const file = formData.get("file") as File | null
@@ -59,6 +70,13 @@ export async function POST(request: Request) {
       )
     }
 
+    if (rows.length > MAX_CSV_ROWS) {
+      return NextResponse.json(
+        { error: `CSV exceeds maximum of ${MAX_CSV_ROWS.toLocaleString()} rows` },
+        { status: 400 }
+      )
+    }
+
     // Check for _type column
     if (!("_type" in rows[0])) {
       return NextResponse.json(

src/app/api/shared-lists/route.ts

@@ -34,7 +34,7 @@ export async function POST(request: Request) {
       )
     }
 
-    const slug = randomBytes(4).toString("hex")
+    const slug = randomBytes(16).toString("hex")
 
     const list = await prisma.sharedList.create({
       data: {

src/app/api/upload/route.ts

@@ -2,6 +2,34 @@ import { NextResponse } from "next/server"
 import { auth } from "@/lib/auth"
 import { uploadImage } from "@/lib/s3"
 import { randomUUID } from "crypto"
+import { rateLimit } from "@/lib/rate-limit"
+
+// Magic number signatures for allowed image types
+const MAGIC_NUMBERS: { type: string; bytes: number[]; offset?: number }[] = [
+  { type: "image/jpeg", bytes: [0xff, 0xd8, 0xff] },
+  { type: "image/png", bytes: [0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a] },
+  { type: "image/webp", bytes: [0x52, 0x49, 0x46, 0x46] }, // "RIFF" + check "WEBP" at offset 8
+  { type: "image/heic", bytes: [0x66, 0x74, 0x79, 0x70], offset: 4 }, // "ftyp" at offset 4
+]
+
+function detectImageType(buffer: Buffer): string | null {
+  for (const sig of MAGIC_NUMBERS) {
+    const offset = sig.offset ?? 0
+    if (buffer.length < offset + sig.bytes.length) continue
+    const match = sig.bytes.every((b, i) => buffer[offset + i] === b)
+    if (match) {
+      // Extra check for WebP: bytes 8-11 must be "WEBP"
+      if (sig.type === "image/webp") {
+        if (buffer.length >= 12 && buffer.toString("ascii", 8, 12) === "WEBP") {
+          return sig.type
+        }
+        continue
+      }
+      return sig.type
+    }
+  }
+  return null
+}
 
 export async function POST(request: Request) {
   const session = await auth()
@@ -9,6 +37,15 @@ export async function POST(request: Request) {
     return NextResponse.json({ error: "Unauthorized" }, { status: 401 })
   }
 
+  // Rate limit: 20 uploads per user per minute
+  const rl = rateLimit(`upload:${session.user.id}`, 20, 60 * 1000)
+  if (!rl.success) {
+    return NextResponse.json(
+      { error: "Too many uploads. Please try again later." },
+      { status: 429 }
+    )
+  }
+
   try {
     const formData = await request.formData()
     const file = formData.get("file") as File | null
@@ -34,10 +71,20 @@ export async function POST(request: Request) {
     }
 
     const buffer = Buffer.from(await file.arrayBuffer())
-    const ext = file.type.split("/")[1] === "jpeg" ? "jpg" : file.type.split("/")[1]
+
+    // Validate actual file content matches claimed MIME type
+    const detectedType = detectImageType(buffer)
+    if (!detectedType || !allowedTypes.includes(detectedType)) {
+      return NextResponse.json(
+        { error: "File content does not match an allowed image type" },
+        { status: 400 }
+      )
+    }
+
+    const ext = detectedType.split("/")[1] === "jpeg" ? "jpg" : detectedType.split("/")[1]
     const key = `${session.user.id}/${randomUUID()}.${ext}`
 
-    const url = await uploadImage(key, buffer, file.type)
+    const url = await uploadImage(key, buffer, detectedType)
 
     return NextResponse.json({ url, key })
   } catch (error) {

src/lib/auth.ts

@@ -4,6 +4,7 @@ import GitHub from "next-auth/providers/github"
 import Credentials from "next-auth/providers/credentials"
 import { PrismaAdapter } from "@auth/prisma-adapter"
 import { prisma } from "@/lib/prisma"
+import { rateLimit } from "@/lib/rate-limit"
 
 const providers = [
   Google({
@@ -25,6 +26,10 @@ const providers = [
       const password = credentials?.password as string
       if (!email || !password) return null
 
+      // Rate limit: 10 login attempts per email per 15 minutes
+      const rl = rateLimit(`login:${email.toLowerCase()}`, 10, 15 * 60 * 1000)
+      if (!rl.success) return null
+
       const user = await prisma.user.findUnique({ where: { email } })
       if (!user || !user.password) return null
 

src/lib/backup.ts

@@ -652,7 +652,7 @@ export async function executeRestore(
           .map((oldId) => drinkIdMap.get(oldId))
           .filter(Boolean) as string[]
 
-        const slug = crypto.randomBytes(6).toString("hex")
+        const slug = crypto.randomBytes(16).toString("hex")
 
         if (mode === "replace") {
           await tx.sharedList.create({