Simple Basic Auth password protection for Next.js

basic_auth.ts

import { type NextRequest, NextResponse } from "next/server";

export function middleware(request: NextRequest) {
  return basicAuth(request);
}

function basicAuth(request: NextRequest) {
  const authHeader = request.headers.get("Authorization");
  const validCredentials = process.env.BASIC_AUTH_CREDENTIALS; // e.g. admin:12345

  if (!authHeader) {
    return createUnauthorizedResponse();
  }

  const [authType, base64Credentials] = authHeader.split(" ");

  if (authType !== "Basic" || !base64Credentials) {
    return createUnauthorizedResponse();
  }

  const credentials = Buffer.from(base64Credentials, "base64").toString();

  if (credentials !== validCredentials) {
    return createUnauthorizedResponse();
  }

  return NextResponse.next();
}

function createUnauthorizedResponse() {
  return new NextResponse("Authentication required", {
    status: 401,
    headers: { "WWW-Authenticate": 'Basic realm="Access to the site"' },
  });
}

export const config = {
  matcher: ["/((?!api|_next/static|_next/image|favicon.ico).*)"],
};