Re: [squid-users] RE: Reverse Proxy Configuration redirects to HTTP rather than HTTPS [NOT PROTECTIVELY MARKED]

From: Amos Jeffries <>
Date: Wed, 09 Oct 2013 17:04:13 +1300

On 8/10/2013 8:10 p.m., John Gardner wrote:
> This email has been classified as: NOT PROTECTIVELY MARKED
>> I wonder if someone can help me out with an issue that has come to light with a new application we are running behind our Squid 2.6 Reverse Proxy >Server.
>> At the moment we have a situation shown below;
>> For all applications, Traffic comes in on HTTPS (and HTTP as well, but mostly HTTPS) from the Internet, passes through FIREWALL1 and then offloads the >SSL at the REVERSE-PROXY, then the rest of the traffic flows as HTTP through FIREWALL2 and onto the APPLICATION WEB SERVER.
>> This works for all of the sites we've been serving for the past two
>> years, but for this particular new application, if you connect using
>>> when the app redirects, Squid appears to go to
>> i.e. it does not stay encrypted. I've found a
>> similar problem >in this post using mod_proxy
>> (
>> ts-to-http-rather-than-https) Can you point me in any direction to
>> assist with this solution please?
> Amos
> Thanks for the response. Squid is configured as;
> So the exact config is; (All of the specific details have been obfuscated)
> https_port cert=cert.crt key=key.pem cipher=ALL:!aNULL:!ADH:!eNULL:!LOW:!EXP:RC4+RSA:+HIGH:+MEDIUM options=NO_SSLv2 vhost
> cache_peer parent 8080 0 no-query originserver name=server_5
> acl sites_server_5 dstdomain cache_peer_access server_5 allow sites_server_5
> What actually happens is that when the browser goes to 99% of the site is rendered correctly i.e. it works as it should. There is one link however, which is generated by JavaScript in the application which always comes back as (not encrypted). I assumed this was an application problem, but the vendor thinks it's Squid, I was hoping I could force this to HTTPS only using something along the lines of;

It is a problem with the whole backend environment of your servers. The
interaction between backend webserver software and the application is ot
working. Squid is just trying as best it can to gateway the HTTPS
traffic into that environment.

The only difference between HTTP and HTTPS is the existence of SSL/TLS
wrappers and port 80/443 usage. Since your setup is using a non-standard
port without SSL/TLS wrappers there is no way for the backend server to
automatically identify what scheme is being used. Given the absence of
SSL/TLS is would be very reasonable to assume http://.
  You have to configure something there for it to know AND the
application needs to be given that information somehow.

Squid is able to pass the "Front-End-Https: on" header to backends. if
the similarly named cache_peer option is configured.

NOTE that by sending the backend connection over a link without SSL/TLS
you are breaking the assumption of end-to-end security and any observer
who can hook into the network behind the proxy can tap into the

> acl port80 myport 80
> http_access deny port80
> deny_info port80

Yes you can try this to workaround the problem. It will hide the broken
URLs being emitted by the application, but some clients will still
complain to the end-user about insecure content being embeded in secure
pages. Also any data Cookies, session ID, personal details, POST/PUT
requests which are delivered to the unsecured URLs will be publicly
visible on those first redirected requests. So the HTTPS security there
is quite broken no matter how "working" it appears to be.

> Or is this more an application issue which should be fixed by the vendor? Any help is greatly appreciated.

This is a problem requiring multiple different changes at various places.
* the application vendror should be using //foo URLs whenever possible.
Omitting the explicit scheme http: or https: parts and leaving the
client to use the scheme they believe is best.
* the admin of your backend server should, either
   - be configuring it to pass details like the scheme type to
applications. Faking https:// when they come from your Squid, or
  - use port 443 or at east SSL on port 8080 on the backend server with
a SSL certificate between Squid and the server. This is private between
Squid and the server to can be a self-signed certificate, to be secure
the only requirements is that Squid has a copy of the CA used to sign
the peers certificate so it can validate.

Received on Wed Oct 09 2013 - 04:04:29 MDT

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