JMETER 403 when uploading a file but needs to be logged in - jmeter

Question

So I am trying to test the file upload function of this website: http://the-v.net/en/vtube/upload-video through JMETER but to be successful, the user has to be logged in through this form: http://the-v.net/login, Now, I think this is a parameter-based authentication which could be solved by defining a valid username and password in the HTTP Authorization Manager config element, but even doing so I keep getting this error:
Thread Name: Thread Group 1-1
Sample Start: 2018-01-30 20:11:06 CST
Load time: 1373
Connect Time: 214
Latency: 1167
Size in bytes: 19151
Sent bytes:134
Headers size in bytes: 768
Body size in bytes: 18383
Sample Count: 1
Error Count: 1
Data type ("text"|"bin"|""): text
Response code: 403
Response message: Forbidden
Response headers:
HTTP/1.1 403 Forbidden
Date: Tue, 30 Jan 2018 12:11:06 GMT
Server: Apache/2.4.23 (Win64) PHP/5.6.25
X-Powered-By: PHP/5.6.25
X-Drupal-Cache: MISS
Expires: Sun, 19 Nov 1978 05:00:00 GMT
Cache-Control: public, max-age=900
X-Content-Type-Options: nosniff
Content-Language: en
X-Frame-Options: SAMEORIGIN
X-Generator: Drupal 7 (http://drupal.org)
Link: <http://the-v.net/en/vtube/warning>; rel="canonical",<http://the-v.net/en/vtube/warning>; rel="shortlink",<http://the-v.net/sites/all/themes/vtube17/favicon.png>; rel="shortcut icon"
Etag: "1517314266-0"
Last-Modified: Tue, 30 Jan 2018 12:11:06 GMT
Vary: Cookie,Accept-Encoding
Keep-Alive: timeout=5, max=100
Connection: Keep-Alive
Transfer-Encoding: chunked
Content-Type: text/html; charset=utf-8
HTTPSampleResult fields:
ContentType: text/html; charset=utf-8
DataEncoding: utf-8
Any idea on how can I solve this? Thanks

Answer 1

I would suggest you record the upload in the browser and look in View Results Tree the headers/ coookies that are transmitted.
You can use File > Template. > Recording
Read:
http://jmeter.apache.org/usermanual/jmeter_proxy_step_by_step.html
You are most probably missing:
A header
A cookie
A parameter

Answer 2

You need to be logged in in order to be able to upload anything. HTTP Authorization Manager won't help as it is designed to deal with protocol level authentication and you need cookie-based one.
Add HTTP Cookie Manager to your Test Plan
Pay attention to form_build_id dynamic parameter you need to pass along with credentials during login request
So your test plan should look like:
1st HTTP Request - open login page
Post-Processor (i.e. CSS/JQuery Extractor to fetch form_build_id
2nd HTTP Request - perform login - provide credentials and the form_build_id from the previous step. You will also need to pass form_id parameter with the value of MYFORM_form
3rd HTTP Request - perform the upload.