Python Flask-cors不返回任何cors标头作为响应

Question

I am using Flask-Cors==3.0.3 Here's the way I am setting it up for my app, where the front end is on localhost:9000 on apache while the backend is on localhost:8080 :

app     = Flask(_name_, template_folder="www/templates", static_folder ="www/static" )
app.config['API_UPLOAD_FOLDER'] = config.API_UPLOAD_FOLDER
app.config['SMOKE_UPLOAD_FOLDER'] = config.SMOKE_UPLOAD_FOLDER

app.config['MONGODB_SETTINGS'] = {
    'db': config.MONGO_DBNAME,
    'host': config.MONGO_URI
}

app.config['CORS_HEADERS'] = 'Content-Type, auth'
app.config['CORS_RESOURCES'] = {r"/apis/*":{"origins":"http://localhost:9000"}}
app.config['CORS_METHODS'] = "GET,POST,OPTIONS"
app.config['CORS_SUPPORTS_CREDENTIALS'] = True

CORS(app)

and my request is like :

OPTIONS /apis/register HTTP/1.1
Host: localhost:8080
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:57.0) Gecko/20100101 Firefox/57.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Access-Control-Request-Method: POST
Access-Control-Request-Headers: content-type
Origin: http://localhost:9000
Connection: close

and the response is :

HTTP/1.1 200 OK
Server: nginx/1.10.1 (Ubuntu)
Date: Tue, 02 Jan 2018 08:52:29 GMT
Content-Type: text/html; charset=utf-8
Content-Length: 0
Connection: close
Allow: POST, OPTIONS

I also tries doing it this way instead of the above and the results were still the same... no CORS headers in the response :(

Cors = CORS(app, resources={r"/apis/*": {"origins": "localhost:9000"}}, supports_credentials=True, methods="GET, POST, OPTIONS", allow_headers="Content-type, auth")

Is there something that I am doing wrong here ? Was trying more things here as changing this :

app.config['CORS_HEADERS'] = 'Content-Type, auth'
app.config['CORS_RESOURCES'] = {r"/apis/*":{"origins":"http://localhost:9000"}}
app.config['CORS_METHODS'] = "GET,POST,OPTIONS"
app.config['CORS_SUPPORTS_CREDENTIALS'] = True

to this:

app.config['CORS_HEADERS'] = ['Content-Type, auth']
app.config['CORS_RESOURCES'] = {r"/apis/*":{"origins":"http://localhost:9000"}}
app.config['CORS_METHODS'] = ["GET,POST,OPTIONS"]
app.config['CORS_SUPPORTS_CREDENTIALS'] = True

but the same results :(

What did seem to work though was using decorator instead of global app level settings like this:

@cross_origin(supports_credentials=True, methods=["GET, POST, OPTIONS"], headers=["content-type, auth"])

Answer 1

There's a comment in the source-code for flask-cors:

"If wildcard is in the origins, even if 'send_wildcard' is False, simply send the wildcard. Unless supports_credentials is True, since that is forbidded by the spec.."

They refer to the spec here: http://www.w3.org/TR/cors/#resource-requests which explicitly states "Note: The string "*" cannot be used for a resource that supports credentials."

So, the solution would seem to be to not use a wildcard origin.