Heimdal releases prior to 0.6.1 and 0.5.3 have a cross-realm vulnerability allowing someone with control over a realm to impersonate anyone in the cross-realm trust path.
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<title>2004-04-01: Cross-realm trust vulnerability in Heimdal</title>
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<h1>2004-04-01: Cross-realm trust vulnerability in Heimdal</h1>
<p>
All releases prior to 0.6.1 and 0.5.3 have a cross-realm vulnerability
allowing someone with control over a realm to impersonate anyone in
the cross-realm trust path.
</p>
<p>
0.6.1 and 0.5.3 performs proper consistency checks on cross-realm
requests, as well as allowing for better control over transit checks.
</p>
<p>
If you are running a vulnerable KDC version and have established
cross-realm trust with anyone, we recommend that you disable this
trust and then upgrade to 0.6.1.
</p>
<p>
Too see if you have any cross-realm trust enabled you can list all
krbtgt principals in the database:
<pre class="example">
kadmin> get -t krbtgt/*
krbtgt/<MY.REALM>@<MY.REALM>
krbtgt/<MY.REALM>@<OTHER.REALM>
krbtgt/<OTHER.REALM>@<MY.REALM>
</pre>
If you have any <tt><OTHER.REALM></tt> variants, you can
temporarily disable them with:
<pre class="example">
kadmin> mod krbtgt/<MY.REALM>@<OTHER.REALM>
Max ticket life [unlimited]:
Max renewable life [unlimited]:
Principal expiration time [never]:
Password expiration time [never]:
Attributes []:+disallow-all-tix
</pre>
You have to repeat this for all such principals as there is no easy
way to automate this. If you have a huge number to update, you will
probably have to dump the database, edit the dump, and reload.
</pre>
After upgrading the KDC you can reenable them with:
<pre class="example">
kadmin> mod krbtgt/<MY.REALM>@<OTHER.REALM>
Max ticket life [unlimited]:
Max renewable life [unlimited]:
Principal expiration time [never]:
Password expiration time [never]:
Attributes [disallow-all-tix]:-disallow-all-tix
</pre>
<p>
See also <a href="https://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2004-0371">CAN-2004-0371</a>.
</p>
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