aprs.me/test/aprsme_web/plugs/remote_ip_test.exs

defmodule AprsmeWeb.Plugs.RemoteIpTest do
  use AprsmeWeb.ConnCase

  alias AprsmeWeb.Plugs.RemoteIp

  describe "trust gating" do
    test "trusted peer (within CIDR) gets forwarded IP from X-Forwarded-For", %{conn: conn} do
      opts = RemoteIp.init(trusted_proxies: ["10.0.0.0/8"])

      conn =
        %{conn | remote_ip: {10, 0, 0, 1}}
        |> put_req_header("x-forwarded-for", "203.0.113.50")
        |> RemoteIp.call(opts)

      assert conn.remote_ip == {203, 0, 113, 50}
    end

    test "untrusted peer (outside CIDR) gets TCP peer IP, ignoring X-Forwarded-For", %{conn: conn} do
      opts = RemoteIp.init(trusted_proxies: ["10.0.0.0/8"])

      conn =
        %{conn | remote_ip: {1, 2, 3, 4}}
        |> put_req_header("x-forwarded-for", "203.0.113.50")
        |> RemoteIp.call(opts)

      assert conn.remote_ip == {1, 2, 3, 4}
    end

    test "untrusted peer ignores CF-Connecting-IP header", %{conn: conn} do
      opts = RemoteIp.init(trusted_proxies: ["10.0.0.0/8"])

      conn =
        %{conn | remote_ip: {1, 2, 3, 4}}
        |> put_req_header("cf-connecting-ip", "203.0.113.50")
        |> RemoteIp.call(opts)

      assert conn.remote_ip == {1, 2, 3, 4}
    end

    test "CF-Connecting-IP respected when peer is trusted", %{conn: conn} do
      opts = RemoteIp.init(trusted_proxies: ["10.0.0.0/8"])

      conn =
        %{conn | remote_ip: {10, 0, 0, 1}}
        |> put_req_header("cf-connecting-ip", "203.0.113.50")
        |> RemoteIp.call(opts)

      assert conn.remote_ip == {203, 0, 113, 50}
    end

    test "trusted IPv6 peer gets IPv6 from header", %{conn: conn} do
      opts = RemoteIp.init(trusted_proxies: ["2001:db8::/32"])

      conn =
        %{conn | remote_ip: {8193, 3512, 0, 0, 0, 0, 0, 1}}
        |> put_req_header("cf-connecting-ip", "2001:db8::2")
        |> RemoteIp.call(opts)

      assert conn.remote_ip == {8193, 3512, 0, 0, 0, 0, 0, 2}
    end

    test "untrusted IPv6 peer keeps its own IP", %{conn: conn} do
      untrusted_ip = {0, 0, 0, 0, 0, 0, 0, 1}
      opts = RemoteIp.init(trusted_proxies: ["2001:db8::/32"])

      conn =
        %{conn | remote_ip: untrusted_ip}
        |> put_req_header("x-forwarded-for", "2001:db8::2")
        |> RemoteIp.call(opts)

      assert conn.remote_ip == untrusted_ip
    end

    test "malformed header value does not crash on untrusted peer", %{conn: conn} do
      opts = RemoteIp.init(trusted_proxies: ["10.0.0.0/8"])

      conn =
        %{conn | remote_ip: {1, 2, 3, 4}}
        |> put_req_header("cf-connecting-ip", "not-an-ip")
        |> RemoteIp.call(opts)

      assert conn.remote_ip == {1, 2, 3, 4}
    end

    test "malformed header value does not crash on trusted peer", %{conn: conn} do
      opts = RemoteIp.init(trusted_proxies: ["10.0.0.0/8"])

      conn =
        %{conn | remote_ip: {10, 0, 0, 1}}
        |> put_req_header("cf-connecting-ip", "not-an-ip")
        |> RemoteIp.call(opts)

      assert conn.remote_ip == {10, 0, 0, 1}
    end

    test "no trusted proxies configured means no peer is trusted", %{conn: conn} do
      opts = RemoteIp.init(trusted_proxies: [])

      conn =
        %{conn | remote_ip: {10, 0, 0, 1}}
        |> put_req_header("x-forwarded-for", "203.0.113.50")
        |> RemoteIp.call(opts)

      assert conn.remote_ip == {10, 0, 0, 1}
    end
  end

  describe "call/2 with default trusted proxies (local host)" do
    # build_conn() defaults remote_ip to {127, 0, 0, 1} which is trusted
    # by the default test config (127.0.0.0/8, ::1/128).

    test "sets remote_ip from CF-Connecting-IP header", %{conn: conn} do
      opts = RemoteIp.init([])

      conn =
        conn
        |> put_req_header("cf-connecting-ip", "203.0.113.50")
        |> RemoteIp.call(opts)

      assert conn.remote_ip == {203, 0, 113, 50}
    end

    test "sets remote_ip from X-Forwarded-For when CF header missing", %{conn: conn} do
      opts = RemoteIp.init([])

      conn =
        conn
        |> put_req_header("x-forwarded-for", "198.51.100.25, 10.0.0.1")
        |> RemoteIp.call(opts)

      assert conn.remote_ip == {198, 51, 100, 25}
    end

    test "prefers CF-Connecting-IP over X-Forwarded-For", %{conn: conn} do
      opts = RemoteIp.init([])

      conn =
        conn
        |> put_req_header("cf-connecting-ip", "203.0.113.50")
        |> put_req_header("x-forwarded-for", "198.51.100.25")
        |> RemoteIp.call(opts)

      assert conn.remote_ip == {203, 0, 113, 50}
    end

    test "handles IPv6 addresses", %{conn: conn} do
      opts = RemoteIp.init([])

      conn =
        conn
        |> put_req_header("cf-connecting-ip", "2001:db8::1")
        |> RemoteIp.call(opts)

      assert conn.remote_ip == {8193, 3512, 0, 0, 0, 0, 0, 1}
    end

    test "leaves remote_ip unchanged when no proxy headers present", %{conn: conn} do
      original_ip = conn.remote_ip
      opts = RemoteIp.init([])

      conn = RemoteIp.call(conn, opts)

      assert conn.remote_ip == original_ip
    end

    test "leaves remote_ip unchanged when header contains invalid IP", %{conn: conn} do
      original_ip = conn.remote_ip
      opts = RemoteIp.init([])

      conn =
        conn
        |> put_req_header("cf-connecting-ip", "not-an-ip")
        |> RemoteIp.call(opts)

      assert conn.remote_ip == original_ip
    end

    test "trims whitespace from IP addresses", %{conn: conn} do
      opts = RemoteIp.init([])

      conn =
        conn
        |> put_req_header("cf-connecting-ip", " 203.0.113.50 ")
        |> RemoteIp.call(opts)

      assert conn.remote_ip == {203, 0, 113, 50}
    end

    test "takes first IP from X-Forwarded-For chain", %{conn: conn} do
      opts = RemoteIp.init([])

      conn =
        conn
        |> put_req_header("x-forwarded-for", "203.0.113.50, 10.0.0.1, 172.16.0.1")
        |> RemoteIp.call(opts)

      assert conn.remote_ip == {203, 0, 113, 50}
    end
  end
end