<div dir="ltr">I've been at this as well for a while now, and managed to make it work for my NFS needs (automounting user homes with password-less logons).<div><br></div><div>Whether and how this would apply to cron or other services, I don't know yet, but presumably would/should work in a similar manner.</div><div><br></div><div>My env:</div><div><br></div><div><div><font face="monospace, monospace">$ lsb_release -d</font></div><div><font face="monospace, monospace">Description: Red Hat Enterprise Linux Server release 7.3 (Maipo)</font></div><div><font face="monospace, monospace">$ rpm -q ipa-server</font></div><div><font face="monospace, monospace">ipa-server-4.4.0-14.el7_3.4.x86_64</font></div><div><font face="monospace, monospace">$ ipa --version</font></div><div><font face="monospace, monospace">VERSION: 4.4.0, API_VERSION: 2.213</font></div></div><div><br></div><div>This is what worked for me in the end:</div><div><br></div><div>1. Create "nfs/<a href="mailto:nfsserver.dom.com@DOM.COM">nfsserver.dom.com@DOM.COM</a>" service, and add to NFS server's /etc/krb5.keytab.</div><div><br></div><div>2. Create IPA "servicedelegation" rule/targets, so that they look like so:<br></div><div><br></div><div><div><font face="monospace, monospace">$ ipa servicedelegationrule-show ipa-nfs-delegation</font></div><div><font face="monospace, monospace"> Delegation name: ipa-nfs-delegation</font></div><div><font face="monospace, monospace"> Allowed Target: ipa-nfs-delegation-targets</font></div><div><font face="monospace, monospace"> Member principals: <b>host</b>/<b>nfsclient</b>.<a href="mailto:dom.com@DOM.COM">dom.com@DOM.COM</a></font></div><div><font face="monospace, monospace"><br></font></div><div><font face="monospace, monospace">$ ipa servicedelegationtarget-show ipa-nfs-delegation-targets</font></div><div><font face="monospace, monospace"> Delegation name: ipa-nfs-delegation-targets</font></div><div><font face="monospace, monospace"> Member principals: <b>nfs</b>/<b>nfsserver</b>.<a href="mailto:dom.com@DOM.COM">dom.com@DOM.COM</a></font></div></div><div><br></div><div>Only niggle here is IPA CLI didn't let me add "host/..." principal to the rule, or perhaps there's a default LDAP ACI of some sort and it requires a privilege/permission to be granted. The "ipa servicedelegationrule-add-member ..." command simply says "no such entry" for "host/..." type principals. Maybe IPA folks can comment.</div><div><br></div><div>I force added it to the delegation rule via LDAP instead using this ldif:</div><div><br></div><div><div><font face="monospace, monospace">dn: cn=ipa-nfs-delegation,cn=s4u2proxy,cn=etc,dc=dom,dc=com</font></div><div><font face="monospace, monospace">changetype: modify</font></div><div><font face="monospace, monospace">add: memberPrincipal</font></div><div><font face="monospace, monospace">memberPrincipal: host/<a href="mailto:nfsclient.dom.com@DOM.COM">nfsclient.dom.com@DOM.COM</a></font></div></div><div><br></div><div>The "nfs/..." principal can be added using CLI "ipa servicedelegationtarget-add-member ..." just fine.</div><div><br></div><div>3. Allow the "nfsclient" host to impersonate users:</div><div><br></div><div><font face="monospace, monospace">$ ipa host-mod <a href="http://nfsclient.dom.com">nfsclient.dom.com</a> --ok-to-auth-as-delegate=true</font></div><div><br></div><div>4. On the "nfsclient" machine, add "impersonate = true" line in the "[service/nfs-client]" section of /etc/gssproxy/gssproxy.conf.</div><div><br></div><div>5. Restart nfs/gssproxy/rpc services on client and server (it's probably just gssproxy on the client that needs a kick, but just to be sure). I was also religiously doing "sss_cache -E" for good measure, unmounting anything that got mounted, and clearing /var/lib/gssproxy/clients of all caches, to start as cleanly before each attempt at user logon. Obv make sure the user does not have an existing/valid ticket in their own cache ("kdestroy -A" as the user), otherwise it'll just mount successfully without delegation.</div><div><br></div><div>I think that's it, I've messed about with the config for a long time and in many places, so there's a small chance there's something else that I did and don't remember. Gssproxy config on "nfsserver" is vanilla, as are my sssd.confs and krb5.confs on both machines, can't think of much else that I might've changed for now.</div><div><br></div><div>So my IPA automount config now mounts users' home dirs on the "nfsclient", without any tickets or keytabs from users.</div><div><br></div><div>There's also a "krb5_principal" option available in gssproxy.conf - I tried to set that to "nfs/<a href="mailto:nfsclient@DOM.COM">nfsclient@DOM.COM</a>" in "[service/nfs-client]" section on the "nfsclient" machine, to try and force gssproxy to use that principal instead of "host/...", but it didn't seem to work, gssproxy defaults to "host/...". Possibly mis-understanding what this option is for, and possibly "host/..." is the safer/standard option? I'm assuming it's default for a reason, or maybe just operational convenience (not having to pollute /etc/krb5.keytabs with more principals than necessary).</div><div><br></div><div>Hope this helps.</div><div><br></div><div>--</div><div>Thanks,</div><div><br></div><div>Greg Kubok.</div><div><br></div><div><div class="gmail_extra"><div class="gmail_quote">On 1 March 2017 at 22:47, Orion Poplawski <span dir="ltr"><<a href="mailto:orion@cora.nwra.com" target="_blank">orion@cora.nwra.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">If you ever get this into a repository, I'd love to see it. Thanks.<br>
<br>
On 01/17/2017 07:44 PM, Charles Hedrick wrote:<br>
> Instructions like that are several places. But NFS is different, and I believe the configuration would be different from other services.<br>
><br>
> I’ve given up on this approach, and have written my own utilities. I’ve actually got three. The first two assume that users who want to do cron jobs on a machine register a keytab for that machine on a secure system. I don’t want to put the actual keytab on the machine where the user is running, because if someone can become root, they can take the keytab and use it anywhere. (I’m in a computer science dept with systems run by faculty and grad students; also systems in public labs.)<br>
><br>
> So instead, I allow users to register that they want to do cron on a specific machine by putting a keytab on a secure server, associated with their username and the hostname. I expect to write a web app to set that up.<br>
><br>
> Credserv runs on the machine with the keytabs. It accepts a request from a server, authenticated using the host’s host key (i.e. /etc/krb5.keytab), with a username in the request. If the user has registered a keytab for that host, credserv returns a credential, locked to that IP address, with forwarding off.<br>
><br>
> Kgetcred is the client side. It runs setuid root (so it can read /etc/krb5.keytab), though it drops privs as quickly as possible. It creates a credentials cache for the user from the credentials returned from credserv.<br>
><br>
> This gives the best granularity of control I can come up with.<br>
><br>
> There’s a third utility in the family: renewd. It gets the uids of all current processes, and renews credentials for all of the users. It’s more complex than you’d expect because a normal renewal (as in kinit -R or kstart) leaves a brief period of time when the credentials cache is unusable. This can result in NFS failing. I use a special approach that depends upon the details of the KEYRING implementation. It should be free of race conditions for NFS. If desired, a different approach to avoid race conditions could be used for caches located in /tmp. I haven’t written that code but there’s a comment in the source outlining it.<br>
><br>
> I’ll be creating a git repository for the code.<br>
><br>
><br>
>> On Jan 17, 2017, at 6:41:13 PM, Orion Poplawski <<a href="mailto:orion@cora.nwra.com">orion@cora.nwra.com</a>> wrote:<br>
>><br>
>> On 01/09/2017 09:52 AM, Charles Hedrick wrote:<br>
>>> Various documentation suggests that it is possible for Gssproxy to get tickets for users who need to use NFS. This is a possible way to handle things like cron jobs.<br>
>>><br>
>>> However while a gssproxy.conf example is given, there’s no sign of what needs to be done in freeipa to authorize it. I tried following instructions for LDAP access, but it doesn’t work. NFS seems to use a different, two-stage method for getting credentials, so that’s not a surprise. There are, not surprisingly, no useful error messages even with logging turned all the way up.<br>
>>><br>
>>><br>
>><br>
>> I'm interested in this as well. All I've been able to find so far is:<br>
>><br>
>> <a href="https://vda.li/en/posts/2013/07/29/Setting-up-S4U2Proxy-with-FreeIPA/" rel="noreferrer" target="_blank">https://vda.li/en/posts/2013/<wbr>07/29/Setting-up-S4U2Proxy-<wbr>with-FreeIPA/</a><br>
>><br>
>> haven't tried anything.<br>
>><br>
>> --<br>
>> Orion Poplawski<br>
>> Technical Manager 720-772-5637<br>
>> NWRA, Boulder/CoRA Office FAX: 303-415-9702<br>
>> 3380 Mitchell Lane <a href="mailto:orion@nwra.com">orion@nwra.com</a><br>
>> Boulder, CO 80301 <a href="http://www.nwra.com" rel="noreferrer" target="_blank">http://www.nwra.com</a><br>
><br>
<span class="gmail-HOEnZb"><font color="#888888"><br>
<br>
--<br>
Orion Poplawski<br>
Technical Manager 720-772-5637<br>
NWRA, Boulder/CoRA Office FAX: 303-415-9702<br>
3380 Mitchell Lane <a href="mailto:orion@nwra.com">orion@nwra.com</a><br>
Boulder, CO 80301 <a href="http://www.nwra.com" rel="noreferrer" target="_blank">http://www.nwra.com</a><br>
<br>
--<br>
Manage your subscription for the Freeipa-users mailing list:<br>
<a href="https://www.redhat.com/mailman/listinfo/freeipa-users" rel="noreferrer" target="_blank">https://www.redhat.com/<wbr>mailman/listinfo/freeipa-users</a><br>
Go to <a href="http://freeipa.org" rel="noreferrer" target="_blank">http://freeipa.org</a> for more info on the project</font></span></blockquote></div><br><div><br></div>
</div></div></div>