Thursday Jul 16, 2009

YubiVDI

Last weekend I decided to put some effort around integrating Sun VDI and strong authentication based on One-Time-Passwords (OTP). During my visit to the European Identity Conference in May 2009 I had received a YubiKey at the booth of Yubico and I was still thinking about setting up some meaningful demonstration with it. During the same period I had received a request from a partner of ours whether it would be possible to have OTP integrated into Sun VDI. So finally this weekend the two ideas came together and I decided to extend the standard VdaClient used in VDI3 with YubiKey authentication.

So what is a YubiKey?

According to Wikipedia the YubiKey, manufactured by Yubico, is a device that acts as a USB keyboard and provides secure authentication by a one-time password algorithm.YubiKey From the manufacturer's website: "The Key generates and sends unique time-variant authentication codes by emulating keystrokes through the standard keyboard interface. The computer to which the Key is attached receives this authentication code character by character just as if it were being typed in from the keyboard – yet it's all performed automatically. This process allows the Key to be used with any application or Web-based service without any need for special client computer interaction or drivers." And in a nutshell, that's what it is. The Key is in fact very small and lightweight (18 x 45 x 2 mm and only 2 grams) and doesn't require a battery. Again, since it is presenting itself as a USB keyboard, you don't need any special device drivers or such. That's why this works also out-of-the-box on a Sun Ray device. So, the Yubikey is a USB device and has one button. If you push the button, it generates an authentication code (consisting of a unique identity code and an OTP). With the identity code it is possible to check if the used Key is really the one assigned to this user. The complete authentication code can be checked either locally with a validation server or over the Internet with a Web Services API that Yubico is offering. This is extremely neat since integrating this way is almost just a matter of minutes. Also a lot of Web Services clients have been written in various languages and these are all open sourced.

For more information on the YubiKey please visit Yubico.com.

Initially I had extended the UI with an additional field where a user can have their generated OTP put in as a visible string. This obviously works fine but after browsing some sites and applications that also integrate with the YubiKey it appears that it is more common to just have the OTP typed in right after the regular password (at least, in the case of "two-factor authentication with username"). In that case it is easy to separate the two since the OTP is a long fixed length string. Anyway, I decided to go back to the more common design which you can see in the demonstration video below. My original design and application you can see here:

So how does it work?

As you can see in the demonstration, a user types in his or her username in the regular Username field and the password (in my case I use the AD password for the user) in the Password + .YubiKey field. I use the AD username and password so the user can be authenticated also against AD. Furthermore, via e.g. a lookup in AD it can be established if this is the key for the user. For this to work, the YubiKey unique identity code needs to be in the user profile. Of course, it is also possible to store these in a separate database.

After the user puts in the username and password, we keep focus in the Password + YubiKey field and press the button on the YubiKey so the OTP code gets typed in right after the regular password for the user...

At that point, the YubiKey identity is verified for this user, the OTP is validated via the Yubico Web Services API, and the username and password are also checked against AD. If this all succeeds, the user is logged in and is either shown its default desktop or the desktop selector frame as can be seen in the demonstration. If either one of these pieces of information is wrong or we try to replay an old OTP, we get the appropiate error messages as can again be seen in the short video.

Have fun!

Monday May 25, 2009

Integrating Sun Secure Global Desktop with Radius Authentication

Last week I have been looking at the integration of SGD (4.41.907) with Radius One-Time-Password (OTP) Authentication. Inspired by some projects that are being done by some of our partners at customer sites and a wiki page on the same subject I decided to setup a similar environment in our lab. The wiki page material is based on an earlier version of Sun Secure Global Desktop and therefore based on an earlier version of Apache web server (version 2.x vs. 1.3.36).

I decided to install ActivIdentity (AI) AAA Radius Server 6.6 next to an already existing installation of VDI3 and Active Directory DC. The Active Directory is integrated with both AAA and VDI. The AAA server will use Active Directory to lookup users and also store serial number information for the token cards that are used by these users. The integration with VDI is for the Kerberos Authentication of Sun Ray users and also for looking up user profiles by SGD after a successful third-party authentication has taken place (all user profiles are provisioned to AD by means of Sun Identity Manager but this is less relevant at this point).

AI Pocket TokenThe authentication within SGD / AAA is based on OTP's generated by ActivIdentity Pocket Tokens. After setting the PIN these can be used in various ways. We will use them in synchronous way which means that after typing in our PIN and clicking OK, the token will generate and present an OTP. Other ways these tokens can be used is through a challenge-response OTP generation.

The integration of SGD (Apache) and Radius authentication can be done in various ways as well. One of them is based on a piece of code (mod_auth_radius) from the open source freeradius.org project. This is what is described on the wiki mentioned above and is also described in this blog. Another way is through a similar piece of code (mod_auth_xradius) from another website called outoforder.cc. The last option and probably the most sophisticated is through a solution like Sun OpenSSO Enterprise.

Where possible I have followed the wiki mentioned above. However, there are some steps that need some adjustments and some other things need to be changed. I will focus mainly on the differences and other things that I encountered...


Step 1. Obtain and install, (if necessary) CVS

I also downloaded and installed CVS to get to the latest version of mod_auth_radius. However, through a conversation I had with the author of this module, the most recent source code can now be found at git://git.freeradius.org/mod_auth_radius.git so to get to the latest version from now on this would require the installation and use of e.g. git-1.6.2.1-sol10-x86-local.gz


Step 2. Retrieve and Build mod_auth_radius

First of all, since we are using Apache 2.x underneath SGD 4.41, we need to get the right mod_auth_radius. As can be easily found on freeradius.org this version is called mod_auth_radius-2.0.c. From the CVS we checkout module mod_auth_radius which contains mod_auth_radius-2.0.c (v 1.5.7). Therefore the 3 last bullets should read:

# cp mod_auth_radius-2.0.c /opt/tarantella/webserver/apache/{version}
# cd /opt/tarantella/webserver/apache/{version}
# bin/apxs -i -a -c mod_auth_radius-2.0.c

However, the last command will generate the following error on a default Solaris x86 installation platform:

/opt/tarantella/webserver/apache/2.2.8_openssl-0.9.8g_jk1.2.25/build/libtool:
  line 1279: gcc4: command not found
apxs:Error: Command failed with rc=65536 

This can of course be fixed by installing gcc4 (e.g. from blastwave.org) or also by just creating a link gcc4 that points to gcc (which is gcc3 on my Solaris 10 x86 platform) like this (there are of course more ways to get this right):

# cd /usr/sfw/bin
# ln -s gcc gcc4
# PATH=/usr/sfw/bin:/usr/ccs/bin:$PATH
# bin/apxs -i -a -c mod_auth_radius-2.0.c

This should have added a line in the Apache /opt/tarantella/webserver/apache/{version}/httpd.conf file:

LoadModule radius_auth_module modules/mod_auth_radius-2.0.so

Step 3.  Configure Apache for RADIUS Authentication

We add the following lines to the end of httpd.conf:

#
# radius_auth_module add
# 
Alias /sgd "/opt/tarantella/webserver/tomcat/5.0.28_axis1.2/webapps/sgd"
<IfModule radius_auth_module>
AddRadiusAuth RadiusServer:1812 ActivPack 5:3
AddRadiusCookieValid 0
</IfModule>

SetEnvIf Request_URI "\\.(cab|jar|gif|der|class)$" sgd_noauth_ok
<LocationMatch "/sgd">
    Order Allow,Deny
    Allow from env=sgd_noauth_ok
    AuthType Basic
    AuthName "Radius Authentication"
    AuthBasicAuthoritative off
    AuthRadiusAuthoritative on
    AuthRadiusCookieValid 0
    AuthRadiusActive On
    Require valid-user
    Satisfy any
</LocationMatch>

Step 4.  Test RADIUS Authentication (optional)

Least thing to do here is to restart the webserver:

/opt/tarantella/bin/tarantella restart webserver

Step 5.  Configure Tomcat to Trust Webserver Authentication
Step 6.  Configure SGD to Allow Webserver Authentication
Step 7.  Allow Administrators to Login via Webserver Authentications (optional)

See wiki for steps 5, 6, and 7.


An additional note is that after all these steps, things worked fine for Internet Explorer but not for Firefox. Investigating the HTTP traffic in more detail revealed that not always the RADIUS cookie (that is set after successful authentication) is send back to the server properly. Also it appeared the cookie had a very strange path and also the expiration date was off. E.g., the cookie path contained "/ expires=...". Looking more closely at the source code I ended up with these lines of code:

static void
add_cookie(request_rec \*r, apr_table_t \*header, char \*cookie, time_t expires)
{
  ...
    apr_snprintf(new_cookie, 1024, "%s=%s; path=/ expires=%s;",
                cookie_name, cookie, buffer);
  } else {
    apr_snprintf(new_cookie, 1024,
                "%s=%s; path=/; expires=Wed, 01-Oct-97 01:01:01 GMT;",
                cookie_name, cookie);
  }
  ...
}

It looks like there is a ';' missing in the line in red. I added a ';' in this line right after 'path=/' and recompiled. After this things also worked for Firefox. Checking the HTTP traffic, I could see the cookie being sent correctly.


Another thing to note is that I have set the lifetime of the cookie to indefinite (AddRadiusCookieValid 0). This is of course an arbitrary choice but I wanted to prevent having to regenerate an OTP every 5 minutes to keep working in SGD. This way the session is tied to the SGD session and will end when we logoff (see the end of this blog of how we can do this).

After these steps the end result should look similar to what you see in the following demonstration...


Basic demonstration of SGD and Radius OTP Authentication

To get a single logoff experience, logging out from SGD should also clear the authentication "session" so trying to log back in will confront us again with a Radius Authentication prompt. For this we have changed the logged-out.jsp file that can be found at the default path: /opt/tarantella/webserver/tomcat/5.0.28_axis1.2/webapps/sgd/webtops/standard/webtop/logged-out.jsp. The line that I put in is the following:

document.execCommand("ClearAuthenticationCache");

This will clear the HTTP authentication cache for the browser. Unfortunately, this is browser dependent and only works for Internet Explorer. There is no straightforward way to get the same behavior with Firefox. Googling around I have found that this is a long standing RFE that apparently has not been implemented. Also some workarounds / hacks are described at various websites (e.g.http://trac-hacks.org) that supposedly will give a similar behavior with Firefox. However, I have not really tried to get this working.

Finally, I have also used mod_auth_xradius to get a similar result. It took more work to get this module built. Apparently this code is less straghtforward to compile on Solaris 10 with gcc. It took some tweaking (not detailed here) to get this compiled. As, said the end result is similar. It is different in the sense that mod_auth_xradius does not use cookies for its sessions. As far as I can tell it is also not possible to set the lifetime of a session to indefinite.

All in all, it seems possible to get this working with the mod_auth_radius module. A much nicer solution would possible be the integration with Sun OpenSSO. This will get away from using Basic Authentication and give us some better session management (in my opinion) and also the possibility of SSO to other back end applications. I have not tried this but it should be fairly straightforward since OpenSSO supports Radius authentication. Might be something interesting to work on for a next "proof-of-concept" :-)

About

This blog covers exciting things I encounter about Oracle's software and related; that is Identity & Access Management, SOA, Security, Desktop, etc. The views expressed on this blog are my own and do not necessarily reflect the views of Oracle.

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