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In other places in the code we tend to make use of the Meteor.absoluteUrl() to fix this. Should we try and make use of this? That way the user only has to properly set their ROOT_URL and everything will work properly regardless of subfolder

hi @geekgonecrazy, thanks for the feedback.

we cannot make use of Meteor.absoluteUrl() here because incoming request objects url attribute is a relative URL
https://nodejs.org/api/http.html#http_message_url

and the webapp.handler method is making a decision about whether to handle the request or not based on that attribute

a separate but related issue was that ROOT_URL is not being properly set in the Set_SiteUrl callback, which will result in inconsistent behavior from the Meteor.absoluteUrl() method

@geekgonecrazy @rodrigok would you kindly review the changes? Idealy I'd like to have this in the next bugfix release. This should also resolve a lot of issues with folks using a reverse proxy setup running in a subdir

Applied this patch to current version - 0.57.2, and it doesn't work.
It only started to work when I've changed this line:
https://github.com/RocketChat/Rocket.Chat/pull/7395/files#diff-d5664ca3caa8062001b0dbddf9679f7cR10
Like this:
WebApp.connectHandlers.use('/file-upload/', Meteor.bindEnvironment(function(req, res, next) {

@simnv i think you just dont have your root_url set. I dont see how that change would fix things as Meteor.bindenvironment just makes meteor variables accessible within that scope: it still doesnt change the fact that the /file-upload/ path is missing root_url for its pattern matching

@ryoshimizu Tried with the new version, result is the same. I do have ROOT_URL set:
export ROOT_URL=https://site/rocketchat/
But unless I change the rocketchat_file-upload.js like in my previous comment, uploaded files are not accessible.

@simnv , in a browser console, what are your values for __meteor_runtime_config__.ROOT_URL and __meteor_runtime_config__.ROOT_URL_PATH_PREFIX and what is the src for the image that is inaccessible?

@Darkneon, it's different for rocketchat electron application and for rocketchat in browser.

Electron:

Browser: