[LNT] Enable X-Forwarded-* headers to be accepted.

[marxin]

Summary

When running behind a HTTP proxy, one needs to accept X-Forwarded-* headers to properly generate URLs.

[cmatthews]

The docs mention "Do not use this middleware in non-proxy setups for security reasons." I would assume because this allows the client to set the host information. I use this in our setups. I think I apply it in the app launch file that we hand to gunicorn instead of here.

Also, you displaced the comment that was for the next line of code.

[marxin]

In D51609#1223590, @cmatthews wrote:

The docs mention "Do not use this middleware in non-proxy setups for security reasons." I would assume because this allows the client to set the host information. I use this in our setups. I think I apply it in the app launch file that we hand to gunicorn instead of here.

Ah, I see. I'm running LNT within Apache instance that is behind a different HTTP proxy. Maybe one can somehow tweak Apache to help here, but I was unable to find anything.
That said, I'll probably need ProxyFix. What about making that conditional based on a config variable in lnt.cfg?

Also, you displaced the comment that was for the next line of code.

[cmatthews]

What are you using for the backend web server?

[marxin]

I use Apache2 + mod_wsgi.

lnt/server/ui/app.py

 import jinja2
 from flask import current_app
 from flask import g
 from flask import session
 from flask import request
 from flask import jsonify
 from flask import render_template
 from flask_restful import Api
+from werkzeug.contrib.fixers import ProxyFix
 from sqlalchemy.exc import DatabaseError
 from sqlalchemy.ext.declarative import DeclarativeMeta
 
 import lnt
 import lnt.server.db.rules_manager
 import lnt.server.db.v4db
 import lnt.server.instance
 import lnt.server.ui.filters
def __init__(self, name):
         # Override the request class.
         self.request_class = Request
 
         # Store a few global things we want available to templates.
         self.version = lnt.__version__
 
         # Inject a fix for missing slashes on the root URL (see Flask issue
         # #169).
+        self.wsgi_app = ProxyFix(self.wsgi_app)
         self.wsgi_app = RootSlashPatchMiddleware(self.wsgi_app)
         self.logger.setLevel(logging.DEBUG)
 
     def load_config(self, instance):
         self.instance = instance
         self.old_config = self.instance.config
 
         self.jinja_env.globals.update(