i do believe a native squid transparent settings will do this. you can 
configure squid with transparency settings, configure squid with authentication 
(basic or LDAP) , set your Unix box (i will assume Linux) to be the default 
gateway, enable ip forwarding (act as a router), configure ipchains to trap 
http traffic and redirect it to your squid port. 



----- Original Message ----
From: Chris Robertson <[email protected]>
To: [email protected]
Sent: Wednesday, April 22, 2009 7:43:59 PM
Subject: Re: [squid-users] Auto Detect Proxy in Browser, visiting users.

gavguinness wrote:
> Hi
> 
> I'm new to Squid.  New in the sense that this time yesterday, I didn't know
> what Squid was.  I knew what I wanted to achieve though, and I've achieved
> most of this today using Squid and a few helpful online guides...
> 
> To have users promted to authenticate when they start their browser (Check)
> To log their activity in a log file (Check)
> Not to have to install any software on the PC (Check)
> Specifically not to use any server based DB lookup authentication (check)
> 
> The only problem is that I want all users to go through Squid, even visiting
> users.  A lot of our guys are not going to want to manually enter Proxy
> settings each time they visit a site - I want it to be automatic.
> 
> Similarly, not every user logs into our server(s), so I can't deploy a
> scrips or setting to the visiting computer as they simply connect to the
> WiFi, or Cabled network point.
> 
> So basically, just connect up to the network, go on line and BAM, they have
> to authenticate.  Just like in Starbucks!  (But without the coffee or wifi
> charges!)
> 
> I looked at transparent settings, but I gather this doesn't work with
> Authentication, so that's a no.
> 
> Now i'm focussing on how to get the clients to auto detect the squid box. But 
> I can't fathom how that's going to work.  If the machines don't know
> it's there, how can squid make itself known to them?
> 
> Ideally (and bear in mind my lack of knowledge at this stage) I would like
> to just have my DCHP tell the clients that the squid box is the default
> gateway and solve it that way, but again, I'm learning that the proxy
> doesn't work that way - it's not a router, right?
> 
> Hope that makes sense, any help appreciated.  But in the meantime, I'll get
> my head back in the manual!
> 
> Cheers
>  

Look into WPAD (http://en.wikipedia.org/wiki/Web_Proxy_Autodiscovery_Protocol) 
or a captive portal like WiFiDog 
(http://en.wikipedia.org/wiki/WiFiDog_Captive_Portal) or the Squid session 
helper (check the archives).

Here's the condensed version of what I have experienced with WPAD.  It all 
assumes that the proxy settings have not been changed from the shipping default 
in the browsers.

Using a Windows (98/2000/XP) machine and Internet Explorer, the DHCP option 252 
is honored.  DNS (wpad.domainname.com) is used in the absence of the DHCP 
option 252.  Firefox (2 or 3) on a Windows (98/2000/XP) machine or OS X (10.4 
for sure) the DHCP option 252 is ignored, DNS is used exclusively .  Safari on 
Windows (98/2000/XP) or OS X ignores both DHCP and DNS and must be explicitly 
configured to use a statically defined PAC 
(http://en.wikipedia.org/wiki/Proxy_auto-config) file.

My suggestion is to have a webserver assigned to http://wpad.yourdomain.tld 
that serves a PAC file when http://wpad.yourdomain.tld/wpad.dat OR 
http://wpad.yourdomain.tld/wpad.da is requested.  This will (transparently) 
catch the majority of web browsers.  For the rest, you should intercept 
outbound port 80 traffic and redirect it to a page that describes how to set 
their browser back to defaults (or how to set their browser to explicitly grab 
the PAC file).

Chris




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