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Re: enabling X-Authenticated-user

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On Thu, Mar 01, 2012 at 03:07:42PM +1300, Amos Jeffries wrote:
> On 01.03.2012 14:32, Brett Lymn wrote:
> >I have an application that pays attention to the X-Authenticated-User
> >header.
> 
> Why? what does it do?
> 

Apparently, it believes it.  I don't _think_ it actually does any
further authentications based on the information from what I can see but
just uses the username presented for its own internal machinations.

> > I need to use this application as an upstream proxy and need to
> >have the user authentication passed from squid through to this
> >application.
> 
> What happens to the user if Squid accepts the credentials and 
> authenticates them. But the other proxy does not? important.
> 

Given that both are querying the same auth database (windows AD) this is
unlikely in our situation.

> > I know about the login=PASS cache_peer directive but I am
> >wondering how that plays with negotiated authentication schemes like
> >kerberos.
> 
> 
> In HTTP proxy-auth credentials are decided at each and every hop down 
> the chain servers. login= is the way Squid uses to determine what 
> credentials are valid for the next peer. The same directive can also 
> completely replace the downstream credentials, wholly or partially and 
> send a new set upstream.
>  Kerberos connection-based nature forces this fact right up into your 
> face. Needing a new keytab token at every proxy. Squid 3.2+ supports 
> login=NEGOTIATE to send your Squid's Kerberos credentials to the next 
> proxy down the chain.
> 

Hmmm I don't think that is what I need - I really need to pass the name
of the user that made the connection to squid upstream.  I have just
tested login=PASS and that works fine for basic auth but kerberos fails.


> Login from user to web servers is irrelevant to this whole process. 
> They are passed down untouched. Although some auth frameworks like 
> NTLM/Kerberos/Negotiate make several bad assumptions and need persistent 
> connection pinning hacks (Squid 2.6, 2.7, and 3.1+ supported) in place 
> to work over HTTP.
> 

Right.  I am not wanting to touch logon from user to web servers.  The
upstream proxy is a security/scanning thing that can apply different
policies based on a user or group membership and also feeds the data
into a reporting database.  For all this to work properly the username
needs of the person making the request via squid needs to be presented
to the upstream proxy.

> > Is there a configuration item I can enable to get the header?
> >A bit of a search showed up nothing apart from some ICAP related 
> >stuff.
> >I cannot use ICAP for this application, I simply need the header.  
> >Would
> >the squid developers consider a patch if I developed one to add this?
> 
> No the header is not part of HTTP or any other protocol specification. 
> It is an experimental header created for the use of ICAP plugins to 
> Squid until such time as Squid can be re-written to use proper 
> authentication to ICAP or ICAP helpers to not depend on the existence of 
> a "user" label.
> 

Well, I can tell you now that someone in the commercial space is abusing
that header for their own ends.  Their documentation has clear
instructions on how to add the header to a BlueCoat device and they have
a .dll for MS ISA.  I don't want to name names in a public forum but I
am happy to provide the info privately if you are interested.

-- 
Brett Lymn
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