HTTP 413 (Payload Too Large) error not handled properly by the UI

Description:

When uploading a 7 MB file on our production instance (behind nginx), the server responds HTTP 413 error but the UI does not reflect this state (the upload widget seems "frozen" at 0% after uploading). I suspect that the payload is too large for nginx, so it never gets passed to the Rocket.Chat server at all (could not find any trace in the app logs).

I would expect the UI to show the same as what happens with the development version (HTTP 400)

Steps to reproduce:

1. Upload a file that is too large for nginx and triggers HTTP 413

Expected behavior:

"File exceeds allowed size of 100 MB. [error-file-too-large] "

Actual behavior:

Widget stays at 0%

Server Setup Information:

• Version of Rocket.Chat Server: 3.7.1
• Operating System: Linux (LXC)
• Deployment Method: snap
• Number of Running Instances: 1
• DB Replicaset Oplog: enabled
• NodeJS Version: v12.18.4
• MongoDB Version:4.0.20

Client Setup Information

• Desktop App or Browser Version: chromium 86
• Operating System: Arch Linux

Additional context

Nginx configuration

server {
	listen 80;
	server_name xxx;

	location / {
		proxy_pass http://127.0.0.1:3000/;
		proxy_http_version 1.1;
		proxy_set_header Upgrade $http_upgrade;
		proxy_set_header Connection "upgrade";
		proxy_set_header Host $http_host;

		proxy_set_header X-Real-IP $remote_addr;
		proxy_set_header X-Forward-For $proxy_add_x_forwarded_for;
		proxy_set_header X-Forward-Proto http;
		proxy_set_header X-Nginx-Proxy true;

		proxy_redirect off;
	}
}

Relevant logs:

nginx

192.168.90.100 - - [20/Nov/2020:12:09:58 +0100] "POST /api/v1/rooms.upload/aQA4q9pFsrasDrAPGi5mEsAqZin5JNPSsL HTTP/1.1" 413 601 "https://xxx/direct/aQA4q9pFsrasDrAPGi5mEsAqZin5J

browser:

POST https://xxx/api/v1/rooms.upload/aQA4q9pFsrasDrAPGi5mEsAqZin5JNPSsL 413

Start with the upload widget and its response handling for POST /api/v1/rooms.upload, using the provided nginx configuration and browser 413 request as context. Reproduce an upload rejected by nginx and trace why the widget remains at 0%. Done means the UI displays the file-too-large error instead of appearing frozen.