On Tue, Sep 16, 2008 at 1:28 PM, André Warnier <[EMAIL PROTECTED]>
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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