Why does my Flask React.js session not work? - reactjs

Question

I'm making the login for a app in react with the backend in flask but the session is not working.
The flask app is running in a remote server on pythonanywhere and I'm testing the react app on my localhost:3000
Here's the code for the flask app:
app = Flask(__name__)
app.config["SESSION_PERMANENT"] = True
app.config["SESSION_TYPE"] = "filesystem"
app.config['PERMANENT_SESSION_LIFETIME'] = timedelta(hours=5)
Session(app)
CORS(app, supports_credentials = True, resources={r"/webapp/*": {"origins": "http://localhost:3000/"}})
#app.route("/webapp/login", methods = ["POST"])
def login():
user = request.get_json(force=True)
Email = user.get("email", "")
Password = user.get("password", "")
login = Login.login(Email, Password)
if login["Success"]:
session["email"] = Email
return login
#app.route("/webapp/checksession", methods = ["GET"])
def checksession():
sessionEmail = session.get("email", "")
if sessionEmail == "":
return utils.returnResult(False, "Session not valid")
return utils.returnResult(True, "")
And in the React app I use axios to do the login and check the session in the server, for example:
axios.get(APIURL + CHECK_SESSION, {withCredentials: true})
.then(response => {
console.log(response.headers);
setSession(response.data.success)
setCheckedSession(true)
})
.catch(err => {
setSession(false)
setCheckedSession(true)
if(err.response) {
}
else {
window.alert('Could not establish a connection to the server!');
}
});
In the dev tools we can see that the server is sending the cookie session:
But when I check the cookies for the app there's nothing there:
(Sorry for the Portuguese)
And in the axios promise handler, when I print the headers of the response, this is all I get:
So every time the react app checks if the user has a valid session in the server, the server creates a new session, which means that the react app is not saving and sending the cookie to the server.
Also, when I test this with postman everything works fine.
I searched all over the places and I can't find an answer for this. Can anyone help me figure out what I'm doing wrong, please?

Answer 1

Turns out it was missing configurations in the flask session:
app.config["SESSION_COOKIE_SAMESITE"] = "None"
app.config["SESSION_COOKIE_SECURE"] = True