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<p><strong>15. Freeradius</strong></p>
<p>Firstly, for Fedora 8, add user radiusd to group wbpriv.</p>
<blockquote>
<pre>[root@pptp ~]# usermod -G wbpriv radiusd</pre>
</blockquote>
<p>For Fedora 4 / 5 / 6, change the permission of the winbind_privileged directory. </p>
<blockquote>
<pre>[root@pptp ~]# chgrp radiusd /var/cache/samba/winbindd_privileged/</pre>
</blockquote>
<p>Secondly, we will need to modify the freeradius configuration file. Fortunately, we have only to change a few lines. </p>
<hr>
<a name="mschap2"></a><strong>15.1 Configure Freeradius for MSCHAPv2
</strong>
<p>Edit /etc/raddb/radiusd.conf to enable MSCAHP2. Open the file and locate the module section and then the mschap subsection.</p>
<blockquote>
<pre>modules {<br>
....[snip]....<br>
mschap {
use_mppe = yes
require_encryption = yes
require_strong = yes
ntlm_auth = "/usr/bin/ntlm_auth --request-nt-key --username=%{Stripped-User-Name:-%{User-Name:-None}} --challenge=%{mschap:Challenge:-00} --nt-response=%{mschap:NT-Response:-00}"<br> }<br>
....[snip]....<br>
}
</pre>
</blockquote>
<p>The mschap option in the authorize and authenticate sections is enabled by default. If they are not, enable them accordingly. Save the file. </p>
<p>The radius server has a secret key for security. The default key for freeradius is testing123. It is a good idea to change it for obvious security reasons. The key is in /etc/raddb/clients.conf. </p>
<blockquote>
<pre>client 127.0.0.1 {<br> #<br> # The shared secret use to "encrypt" and "sign" packets between<br> # the NAS and FreeRADIUS. You MUST change this secret from the<br> # default, otherwise it's not a secret any more!<br> #<br> # The secret can be any string, up to 32 characters in length.<br> #<br> secret = testing123
....[snip]....
</pre>
</blockquote>
<p><strong>Note</strong>: if you change the secret key, you must modify the /etc/radiusclient-ng/servers so that they match each other.
</p>
<p>Refer to <a href="poptop_ads_howto_a6.htm">Appendix 6</a> for information on Fedora 4 / 5 / 6.</p>
<hr>
<p><strong><a name="access"></a>15.2 PPTP Access Control </strong></p>
<p>The above configuration allows everyone with a valid userID in the AD to connect to the pptpd server. If you want to restrict access to a group of users, you can create a group, say VPN_Allowed, in the AD. Add users to the group and modify the ntml_auth line in /etc/raddb/radius.conf to include the parameter "--require-membership-of=EXAMPLE+VPN_Allowed". </p>
<p>In the example, I split the line into multiple lines for clarity. It should be one continuous line in the configuration file. </p>
<blockquote>
<pre>ntlm_auth = "/usr/bin/ntlm_auth --request-nt-key
--username=%{Stripped-User-Name:-%{User-Name:-None}}
--challenge=%{mschap:Challenge:-00}
--nt-response=%{mschap:NT-Response:-00}
--require-membership-of=EXAMPLE+VPN_Allowed"</pre>
</blockquote><p></p>
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