Bug: `get_baseurl_from_conn/1` fails on `Fly.io`

[nelsonic]

Don't know why, but we're having trouble with ElixirAuthGoogle.generate_oauth_url(conn) on our Calendar app: dwyl/calendar#38
We've identified that the conn on Fly.io is actually reporting port: 80 and scheme: :http
get_baseurl_from_conn/1 is setting the scheme to http instead of https which means that Google Auth Fails with the Error 400: redirect_uri_mismatch error. 😢

I think we can check for the presence of the req_headers -> x-forwarded-proto which is set to "https"
Just need to write a test for this ...

Todo

• Create a test for {"x-forwarded-proto", "https"}
• Add code to check for it at the top of get_baseurl_from_conn/1
• Make sure nothing else breaks!
• Publish new version of the package to test in calendar App.

[nelsonic]

Test:

  test "get_baseurl_from_conn(conn) x-forwarded-proto header for https #94" do
    conn = %{
      host: "gcal.fly.dev",
      port: 80,
      scheme: :http,
      req_headers: %{
        "x-forwarded-proto" => "https"
      }
    }

    assert ElixirAuthGoogle.get_baseurl_from_conn(conn) == "https://gcal.fly.dev"
  end

[nelsonic]

Getting on this now cause I really want to fix dwyl/calendar#38

[jtormey]

Good timing, I'm seeing this as well and was looking to see if it had been reported 🙂

To add to this, when running locally and tunneling through ngrok for testing sign-in with Google, the URL also incorrectly uses HTTP.

Is there a reason the URL is built from conn, rather than the app Endpoint, which should already know how to build a public URL?

[nelsonic]

@jtormey thanks for commenting and sharing your experience.
are you deployed to Fly.io?
No reason for not using Endpoint. We just didn't have a functional way of doing that.
Can we read the Endpoint from the context of a Controller?

Looks like it: https://stackoverflow.com/questions/40243229/how-to-get-the-current-base-domain-of-a-phoenix-app

MyAppWeb.Endpoint.url()
# => "http://localhost:4000"

Ok, I don't really see a situation where this package will be used outside of a Phoenix App ... 💭
So maybe we can shift to using this method to get the base_url ...

[jtormey]

Yes! I'm deployed to Fly.

That's a good point, relying on Endpoint would limit use of this library to Phoenix. Maybe would be best to derive from conn by default, with a configuration option where Endpoint.url() can be set as the base URL to use.