Stack Overflow in Buffalo with Bearer Tokens

When a Buffalo application serves an API or web UI in Buffalo, New York, developers commonly use Bearer Tokens for authentication. A Bearer Token is a simple secret—typically a long string—sent in the HTTP Authorization header as Authorization: Bearer <token>. If APIs or static assets are exposed in Buffalo without additional protections, and tokens are embedded in JavaScript, leaked in logs, or transmitted over non-TLS channels, the unauthenticated attack surface expands. middleBrick scans such endpoints in black-box mode and can detect whether token handling over public routes contributes to risk under checks such as Authentication, Data Exposure, and Unsafe Consumption.

Consider a Buffalo app that hosts both server-rendered HTML and a public API under /api. If routes are permissive and do not validate origin or require a session, an attacker may leverage Cross-Site Scripting (XSS) or route misconfiguration to steal Bearer Tokens. These tokens might then be used to escalate privileges via Broken Object Level Authorization (BOLA/IDOR) or to access sensitive data through Excessive Agency patterns if the token grants broad scopes. middleBrick’s checks for BOLA/IDOR, Property Authorization, and Input Validation highlight cases where tokens are accepted without sufficient context checks, and its LLM/AI Security probes can surface prompt or token leakage when endpoints expose model-related endpoints inadvertently.

Moreover, if your Buffalo service exposes an OpenAPI spec with $ref resolution, middleBrick cross-references runtime calls against spec definitions. This can reveal mismatches where Bearer Token validation is declared but not enforced, for example when CORS allows origins that should not receive credentials. Data Exposure and Encryption checks will flag transmission without TLS or storage in insecure logs. Because Buffalo apps often integrate with JavaScript frontends, insecure cookie attributes or missing SameSite and Secure flags can compound the issue, enabling token exfiltration over public networks that middleBrick identifies as risky under its Unauthenticated LLM Endpoint and Data Exposure checks.

To reduce risk, enforce strict Bearer Token handling in Buffalo. Always serve APIs over TLS, validate the Authorization header on every request, and avoid exposing tokens in URLs or client-side code. Use middleware to verify token scope and origin, and apply strong CORS policies. The following examples show secure patterns for a Buffalo application.

Example 1: Validating Bearer Tokens in a Buffalo middleware

// In middleware/ensure_auth.ex
defmodule MyAppWeb.EnsureAuth do
  import Plug.Conn

  @behaviour Plug

  def init(opts), do: opts

  def call(conn, _opts) do
    case get_bearer_token(conn) do
      {:ok, token} when token == System.get_env("API_TOKEN") ->
        conn
      {:ok, _token} ->
        send_resp(conn, 401, "Invalid token") |> halt()
      :error ->
        send_resp(conn, 401, "Authorization header required") |> halt()
    end
  end

  defp get_bearer_token(conn) do
    with ["Bearer " <> token] <- get_req_header(conn, "authorization") do
      {:ok, token}
    else
      _ -> :error
    end
  end
end

Example 2: Applying the middleware to API routes in Buffalo

// In web/router.ex
defmodule MyAppWeb.Router do
  use MyAppWeb, :router
  import MyAppWeb.EnsureAuth

  pipeline :api do
    plug :accepts, ["json"]
    plug EnsureAuth
  end

  scope "/api", MyAppWeb do
    pipe_through :api

    get "/profile", ProfileController, :show
    post "/actions", ActionController, :create
  end
end

Example 3: Secure token handling in a frontend request

// JavaScript fetch example (served over TLS)
fetch('https://api.example.com/api/profile', {
  method: 'GET',
  headers: {
    'Authorization': 'Bearer ' + process.env.VITE_API_TOKEN,
    'Content-Type': 'application/json'
  },
  credentials: 'omit' // Avoid sending cookies unless needed
})
  .then(response => response.json())
  .then(data => console.log(data));

Example 4: Environment-based token management in Buffalo

// config/runtime.exs
import Config

config :my_app, MyAppWeb.Endpoint,
  url: [host: "api.example.com", port: 443],
  https: [
    port: 443,
    cipher_suite: :strong,
    keyfile: System.get_env("SSL_KEY_PATH"),
    certfile: System.get_env("SSL_CERT_PATH")
  ]

config :my_app, :api_token,
  System.get_env("API_TOKEN") || raise("API_TOKEN environment variable not set")

Example 5: CORS and token policy

// In web/router.ex or a plug pipeline
plug Plug.Parsers, parsers: [:urlencoded, :multipart, :json]
plug Plug.MethodOverride
plug Plug.Head
plug MyAppWeb.EnsureAuth
plug MyAppWeb.CorsPlug

# CorsPlug ensures only trusted origins can send credentials
# and does not allow wildcard origins when tokens are used.