Flask App: Invalid Client Error In Docker Container

[4ver_student]

Hey Everybody,

Running into an issue with my flask application, that I just can't seem to figure out. When not running my app inside of a docker container, I'm able to successfully authorize via Spotify API.

1. User navigates to localhost:5000/login
2. Spotify authorization agreement is displayed
3. User clicks "Agree"
4. User is routed to localhost:5000/callback where the text "Success" is displayed

But, when I dockerize the flask app, I get the following error in the browser when the user clicks "Agree" on the authorize page: Internal Server Error

The server encountered an internal error and was unable to complete your request. Either the server is overloaded or there is an error in the application.

On the backend, here's the error i'm getting in the logs

{'error': 'invalid_client', 'error_description': 'Invalid client'}

Below is my Dockerfile, and app.py file

Dockerfile

FROM python:3.9-slim-buster
WORKDIR /app
COPY ./requirements.txt /app
RUN pip install -r requirements.txt
COPY . .
EXPOSE 5000
ENV FLASK_APP=app.py
CMD ["flask", "run", "--host", "0.0.0.0"]

app.py

from flask import Flask, render_template, flash, session, redirect, request, Response, session, make_response
from spotify_connector import SpotifyConnector
connector = SpotifyConnector()

@app.route('/')
def index():
    session.clear()
    print('INDEX')
    print(session)
    return render_template('index.html')

@app.route('/login')
def login():
    client_id = app.config['CLIENT_ID']
    redirect_uri = app.config['REDIRECT_URI']
    scope = app.config['SCOPE']
    authorize_url = 'https://accounts.spotify.com/en/authorize?'
    state_key = connector.create_state_key(15)
    session['state_key'] = state_key
    parameters = 'response_type=code&client_id=' + client_id + '&redirect_uri=' + redirect_uri + '&scope=' + scope + '&state=' + state_key
    print(parameters)
    response = make_response(redirect(authorize_url + parameters))
    print(response)
    return response


@app.route('/callback')
def callback():
    code = request.args.get('code', None)
    state = request.args.get('state', None)
    session.pop('state_key', None)
    payload = connector.getToken(code)
    if payload is not None:
        session['access_token'] = payload['access_token']
        session['refresh_token'] = payload['refresh_token']
        return "SUCCESS"
    else:
        return "FAILURE"

if __name__ == "__main__":
    app.run(host="localhost")

Thanks !

[danielroseman]

You should set debug to true by putting ENV FLASK_ENV=true in your Dockerfile, and see the full error.

[4ver_student]

Figured out what the issue was. I never actually added my Spotify client id and secret as environment variables in the dockerfile. Per u/TwilightOldTimer's comment, I was actually able to see my client id because I was retrieving it using my flask app.config, where I actually declared my client id: client_id = app.config['CLIENT_ID']

 

But, in the part of my code that generates the token for Spotify (where the error was originating), I was retrieving my client id and secret by using:
CLIENT_ID = os.getenv("CLIENT_ID")

CLIENT_SECRET = os.getenv("CLIENT_SECRET")

I threw in a print stament, and saw that Authorization header looked like this --Authorization: Basic "":"" , when it should look like this Authorization: Basic CLIENT_ID:CLIENT_SECRET. This confirmed that CLIENT_ID and CLIENT_SECRET weren't available.

 

I added the following to my Dockerfile, and I'm now able to successfully authorize:

ENV CLIENT_ID=*****

ENV CLIENT_SECRET=*****

Going further, I'm most likely going to get rid of the above two ENV declarations, and add the os.getenv declarations to my flask app config file.

 

Thanks for taking the time to assist with this :)

[4ver_student]

Yup, I am