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From "Clayton Hicklin" <chick...@gmail.com>
Subject Re: [users@httpd] Pass-through LDAP authentication with Internet Explorer and Active Directory
Date Tue, 16 Sep 2008 19:40:21 GMT
"So what I believe in this case, is that the LDAP module might, possibly,
rely on the "REMOTE_USER" header that IE is sometimes sending when the user
is authenticated in the domain.  And that one indeed would probably contain
the domain and user.  If that is the case, then a simple manipulation of the
HTTP headers of the request, using standard Apache modules, might be enough
to get just the user."

I agree, I believe that is exactly what is happening.  I can verify that the
REMOTE_USER server variable is set to 'domain\user' using PHP (echo
$_SERVER['REMOTE_USER']).  I didn't realize that you could manipulate
headers with Apache.  I will definitely look into this as it sounds like
that is what I need.  Thanks.

Clayton

On Tue, Sep 16, 2008 at 2:32 PM, André Warnier <aw@ice-sa.com> wrote:

> Clayton Hicklin wrote:
>
>> On Tue, Sep 16, 2008 at 1:28 PM, André Warnier <aw@ice-sa.com> wrote:
>>
>>  Clayton Hicklin wrote:
>>>
>> [...]
>
> Clayton,
> Your first communication was a bit summarised, so I did not know to which
> extent you knew the underlying tidbits, from there my fist answer.
>
> I am currently in the middle of the same kind of problematic. I have
> created an SSO solution that works at the Tomcat level, in a particular
> context, and and I am interested in a solution at the Apache level, just
> like you.
> In the process of creating the Tomcat-level solution, I have learned quite
> a bit about how IE (and servers) work in that respect, and my
> questions/opinions are guided by that.
>
>
>>>  I didn't mean to imply that the authentication fails "in" IE.  I realize
>> it
>> is at the server.  My issue is that I would like a seamless user
>> experience.  IE is passing 'domain\user' due to "Windows Integrated
>> Authentication" being turned on and it would be nice if those credentials
>> could be used to authenticate without popping up the login dialog.
>>
> That is what should indeed happen, if the server supports the related
> authentication, meaning the authentication "type" that IE is trying.
>
>  This
>
>> works using the mod_auth_sspi module (which uses NTLM) but not with LDAP
>> authentication.
>>
> Which module are you using for this LDAP authentication ?
>
>  The reason is that with LDAP authentication, you have to
>
>> specify an attribute to search for the username that is passed to Apache.
>> In the case of Active Directory, this attribute is sAMAccountName.  This
>> attribute stores the username of the Windows user.  The problem is that IE
>> passes 'domain\user' (not just 'user') on it's first attempt at
>> authentication.
>>
> That's where I am not so sure.  What makes you sure that this is indeed
> what is happening ? (I am not saying it is false, I just mean that I have a
> doubt and would be interested in whether you have really verified this, and
> how).
>
> This obviously fails which causes the login dialog to pop
>
>> up.  You can then just type in your username and password and everything
>> works fine.
>>
>> I think the ultimate solution would be to modify the Apache LDAP module to
>> accept a parameter that would optionally strip out the domain portion of
>> the
>> credentials that IE passes.
>>
>
> Yes, that kind of what you need, unless that parameter already exists in
> the module you are using.  It would be relatively surprising if it didn't.
> But even if it isn't available, there might be another solution, stay with
> me.
>
>  That way, we could use IE + APACHE + Active
>
>> Directory (LDAP) for a seamless SSO solution.  I think this would be
>> pretty
>> common in most corporate environments, which is where this is being
>> implemented.
>>
>>
> One nore thing I want to add here, is a brief summary of how web
> authentication works, just in case there is a part in there that isn't clear
> to you, and because there is a particular step that may play a role.
>
> 0) we imagine that, at the beginning, the browser is just opened, and knows
> nothing yet of the URL or the server on which it resides.
>
> 1) browser sends a request to server for a particular URL.  Because the
> browser at this stage does not know that this URL requires any
> authentication, the request is sent without any authentication.
> 2) the server receives this request.  It consults its configuration, and
> sees that this URL requires some form of authentication and/or access
> control.  It thus verifies if the request contains this kind of
> authentication. If yes, the request goes through and we're done.
> 3) The request does not contain an authentication (or not one of the
> accepted type). So the server sends back to the browser a response "401
> Authorization required", along with the type of authentication required
> (NTLM, Basic, Digest are 3 possible, supported by IE), and along (if Basic
> or Digest) with a "realm" (the protected "area" name on the server).
> 4) the browser receives the 401 response.  It looks at the "authentication
> type" required, and, *if it can handle that* (which may depend on its
> settings, security zone etc..) it proceeds to try that kind of
> authentication. (If the browser cannot handle that particular type of
> authentication requested by the server, it may check if it has a "fallback
> type" that it can try. If it doesn't have such a fall-back, I do not know
> really what happens, but I guess some kind of error at the browser side.)
> 5) once the browser has "put in the bag" the required pieces for the
> authentication (as requested by the server, or its fallback type), it
> re-sends the same original request to the server, but this time it adds an
> "Authorization:" header with the appropriate content.
>
> Now, depending on the case, a back-and-forth dialog *may* take place
> between the server and the browser.  For instance, with IE and NTLM
> authentication, there are 3 such exchanges before the server and browser are
> satisfied, and the browser has the right content to send in its
> "Authorization:" header.
>
>
> I am only pointing this all out so that it would be clearer that it is
> important to know, for instance, *which* kind of authentication the LDAP
> module is telling IE (in the 401 message) that is required.
> Unless this LDAP module can handle an NTLM-type 3-step dialog with IE (like
> the mod_auth_sspi module can), then probably what the module sends is a
> response which requires a "Basic" authentication.
> Does IE then automatically send whatever IE thinks the domain\userid is ,
> as a "Authorization: Basic xxxxxxxxxxxxxxxxxx" header containing the user-id
> and user password ?
> It seems a bit far-fetched that IE would send the user's password over the
> network, just Base64-encoded.
>
> So what I believe in this case, is that the LDAP module might, possibly,
> rely on the "REMOTE_USER" header that IE is sometimes sending when the user
> is authenticated in the domain.  And that one indeed would probably contain
> the domain and user.  If that is the case, then a simple manipulation of the
> HTTP headers of the request, using standard Apache modules, might be enough
> to get just the user.
>
> That was a long message, but in the end the answer may be simple.
>
>
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-- 
Clayton Hicklin
chicklin@gmail.com

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