[squid-users] Squid 3.x or 4.x acting as a transparent http proxy (NOT https)

Wed Feb 7 21:38:17 UTC 2018

Hello setuid,

If you do not mind looking at other tutorials - these are what we have in the test lab.

https://docs.diladele.com/tutorials/transparent_proxy_ubuntu/index.html
https://docs.diladele.com/tutorials/policy_based_routing_squid/index.html

First one for Squid running on the gateway and the second one for separate Squid that intercepts  traffic re-routed from the router using Policy-Based-Routing.
The tutorials are working, I test it with every release of our ICAP web filter.

Best regards,
Rafael Akchurin
Diladele B.V.

-----Original Message-----
From: squid-users [mailto:squid-users-bounces at lists.squid-cache.org] On Behalf Of setuid
Sent: Wednesday, February 7, 2018 10:11 PM
To: squid-users at lists.squid-cache.org
Subject: [squid-users] Squid 3.x or 4.x acting as a transparent http proxy (NOT https)

I'll start with the pointedly easy stuff: Squid > 2.6 (tested 3.4, 3.5,
4.0 on Ubuntu Xenial, Debian Jessie, FreeSBD 11.1 using iptables, pf, ipf, ipfilter) does not work at all, when configured as a transparent proxy. Full stop.

I went through hundreds of posts on dozens of forums, blogs and other resources, tried dozens and dozens of configurations suggested by those posts, tried all 3 firewall options on BSD, tried two versions of Ubuntu and the various versions of Squid from the apt repos, as well as those in BSD's ports.

All of them, 100%, fail in _exactly_ the same way, no matter what my configuration was set to. That result, is that _every single http request I make_ when Squid is configured as a transparent proxy, results in the following response being logged:

======================
	07/Feb/2018:15:10:59 -0500.213      0 192.168.1.1 TAG_NONE/400 3583 GET
/ - HIER_NONE/- text/html ("-" "-")
======================

When I point a client directly at the proxy, using a browser, curl or anything else, I see:

======================
	07/Feb/2018:15:12:56 -0500.875     82 192.168.1.1 TCP_MISS/302 333 HEAD
http://www.java.com/ - HIER_DIRECT/www.java.com - ("-" "curl/7.47.0") ======================

These were the same exact request against the same exact Squid instance.
If I use Squid 3.5 on Ubuntu or 3.5 and 4.0 on BSD, the logged entry is _identical_ for every single http request I make, regardless of origin.

My Squid configuration is 100% default, identical to the generic config, with the exception of the following lines:

======================
http_port 3128
http_port 3129 intercept
tcp_outgoing_address 192.168.1.25
debug_options ALL,9
======================

I've tried all of the obvious links, blogs and resources I could Google up, and 100% of them fail to function as described. Most people I've seen on the forums who attempt to get this working, throw their hands up in defeat and end up configuring the proxy directly on every client that needs it.

My current environment looks like this:

[ wireless router: 10.0.1.1 on LAN side, 192.168.1.1 on WAN side ]

That router has a firewall script on it that says:

======================
#!/bin/sh
PROXY_IP=192.168.2.25
PROXY_PORT=3128
LAN_IP=$(nvram get lan_ipaddr)
LAN_NET=$LAN_IP/$(nvram get lan_netmask)

iptables -t nat -A PREROUTING -i br0 -s $LAN_NET -d $LAN_NET -p tcp --dport 80 -j ACCEPT iptables -t nat -A PREROUTING -i br0 -s ! $PROXY_IP -p tcp --dport 80 -j DNAT --to $PROXY_IP:$PROXY_PORT

iptables -t nat -I POSTROUTING -o br0 -s $LAN_NET -d $PROXY_IP -p tcp -j SNAT --to $LAN_IP iptables -I FORWARD -i br0 -o br0 -s $LAN_NET -d $PROXY_IP -p tcp --dport $PROXY_PORT -j ACCEPT ======================

This takes every packet that hits the router on :80, and sends it to my Squid server on .25, which mangles it and sends it back to 192.168.1.1 (router), and onward back to client who requested it.

When I was using 2.6 (without large_file support), I was using this same exact configuration, but http_port was set to 'accel', and I didn't need _any_ NAT/routing rules on the squid side at all. It all "Just Worked(tm)".

Now I need to jump through hoops to do pf incantations of rdr/direct-to (but direct-to and direct-reply aren't supported on FreeBSD's pf, only OpenBSD's pf supports that syntax), and iptables PREROUTING and POSTROUTING mojo (also fails).

Here's a list of some of the resources I've tried, with 100% failure in every case. There are dozens more that I've lost in my browser history now.

* https://wiki.squid-cache.org/ConfigExamples/Intercept/Ipfw
*
https://wiki.squid-cache.org/SquidFaq/InterceptionProxy#Interception_Caching_packet_redirection_for_OpenBSD_PF
* https://www.benzedrine.ch/transquid.html
*
https://www.unix-experience.fr/2013/create-a-powerfull-proxy-cache-with-squid-and-openbsd-2/
*
https://www.cyberciti.biz/tips/linux-setup-transparent-proxy-squid-howto.html
*
https://adilmehmoodbutt.wordpress.com/2014/02/19/how-to-install-squid3-transparent-proxy-server/
* https://veesp.com/en/blog/how-to-setup-squid-on-ubuntu
* https://ubuntuforums.org/showthread.php?t=2210987
*
http://ubuntuserverguide.com/2012/06/how-to-setup-squid3-as-transparent-proxy-on-ubuntu-server-12-04.html
*
http://roberts.bplaced.net/index.php/linux-guides/centos-6-guides/proxy-server/squid-transparent-proxy-http-https

I also tried asking in #squid on Freenode (dead channel), and #FreeBSD (helpful folks there, but they too, failed to get this working).

So I'm at an impasse. Is this just 100% decoupled from the current codebase, and doesn't work at all? Or is this really meant to be some lengthy archaeology to find the right, working solution for getting this configured in Linux or BSD?

It seems like with the hundreds of posts from people out there failing to do this correctly, that there's a great opportunity here to a.) make it work again like it did in v2.6, and b.) document the _precise steps_ required to make it function as a transparent http proxy [eg: install foo, create file with these exact contents, execute this exact command, test with this use case, if error message 'bar', do the following ].

Can anyone give me a hand here? I, like so many dozens of others, am about to just give up and move past this, because it just does not work anymore.

Help! :D

(Thanks in advance for making it this far in my plea)

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