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CDN Support - Map End User Address Correctly


Randy Calvert

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Posted

[Summary]

If you're using a CDN such as Akamai or Cloudflare, you essentially have a reverse proxy that sits in front of your web server.  This is typically done to help improve the security (protection from volumetric layer 3/4 DDoS attacks and layer 7 application layer attacks and the performance of a website (caching of objects close to the end user, automatic content minification, etc.)

However if you're using a CDN in front of your site, you lose visibility to the IP addresses of your community members.  By default, IPS reports the source IP address, which happens to be the address of the reverse proxy.  To work around this challenge, most reverse proxies provide the source IP address it saw in a special header.  For example, with Akamai the address name is X-True-Client-IP and with Cloudflare, it would be CF-Connecting-IP.  Unfortunately IPB does not currently have a mechanism to remap where it consumes the end user source IP address from.  

[The Ask]

Provide a mechanism within the ACP that would allow an admin to provide a value of a header name which IPB would use to determine the end user's IP address.  

Posted

This is already supported, in the ACP go to security, security settings, then select 'Trust IP addresses provided by proxies?'. That'll then use the x-forwarded-for ip address, which as far as I'm aware all or most cdn's will support.

Posted

Login is working as expected.  That's not a problem.  

The challenge is that when members use the site, if there is a proxy such as Akamai or Cloudflare in front of the site...  if I look in the IP logs or I look at the IP address from the post, it shows the address of the Proxy, not the member.  

This means as an Admin, we lose visibility into our end user IP information.  It also makes it difficult to cross reference activity, etc.  The "Information associated with IP address" section of the moderator CP is basically useless when a proxy is used because it's the proxy that is reported and not the member.  

See below as an example:

5902ad33d6221_ScreenShot2017-04-27at10_46_25PM.png.1d9c5f9c1cd54e3d519da54f54419038.png

In this particular case, I know the end user for this IP address is actually coming from somewhere else, but that happens to be the closest Cloudflare data center.  However the end user's actual source IP address is passed as a Layer 7 HTTP header.  Depending on the reverse proxy, the field name can vary.  If we could have an input specify what that was and have the IP address related tools use that header, we could accurately log/report end user IP information.  

Posted
44 minutes ago, Randy Calvert said:

In this particular case, I know the end user for this IP address is actually coming from somewhere else, but that happens to be the closest Cloudflare data center.  However the end user's actual source IP address is passed as a Layer 7 HTTP header.  Depending on the reverse proxy, the field name can vary.  If we could have an input specify what that was and have the IP address related tools use that header, we could accurately log/report end user IP information.  

You can set this via Apache/Nginx config.

Posted
9 hours ago, Randy Calvert said:

Not a bad idea...  I'll have Apache rewrite the source IP address based on the header.  Then PHP won't know otherwise what's going on.  

Thanks!

Pretty sure cloudflare have a tutorial on how to do it as well. They used to have an apache module which did that too.

Posted
12 minutes ago, Randy Calvert said:

Yes, I do.  I implicitly checked it.  Might be a bug.  I'll open a ticket just to make sure.  

For Apache there are usually apache modules such as mod_cloudflare. This works without any issues for cloudflare and another reverse proxy (which is kinda unknown) for my forums. For nginx you can simply adapt the nginx config as already mentioned. It's not really something which needs to be considered by IPB.

  • 4 weeks later...

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