ipa id-range-find didn't find the ranges on the other servers after I added them on one. It found the primary ranges (managed by ipa-replica-manage) on all 3 systems, but of course they are different.

From: Rob Crittenden <rcritten@redhat.com>
Sent: Monday, May 15, 2023 4:15 PM
To: FreeIPA users list <freeipa-users@lists.fedorahosted.org>
Cc: Sam Morris <sam@robots.org.uk>; Alexander Bokovoy <abokovoy@redhat.com>; Charles Hedrick <hedrick@rutgers.edu>
Subject: Re: [Freeipa-users] Re: Authentication failures on a RHEL 9.2 IPA server

Charles Hedrick via FreeIPA-users wrote:
> OK, so I see the answer to my problem is to run
>
> ipa config-mod --add-sids --enable-sid
>
> But we have old UIDs that with low numbers. It looks like I need to do
>
> ipa idrange-add CS.RUTGERS.EDU_low_id_range --base-id=1
> --range-size=200000 --rid-base=200000000 --secondary-rid-base=300000000
> ipa idrange-add CS.RUTGERS.EDU_mid_id_range --base-id=600000
> --range-size=200000 --rid-base=400000000 --secondary-rid-base=500000000
>
> In order for ipa user-add for those UIDs to work on any system,
> presumably I have to do that on all IPA servers. Is that OK? I'm
> assuming new id's where we don't specify a UID will be put in the same
> range before, which is different on each server.

Ranges are global, not per-server. So assuming your ranges are ok and
there are no overlaps for the IDs or RID ranges this is probably ok, but
I'm not a PAC expert.

I think what you're seeing is the DNA (Distributed Numeric Assignment)
plugin at work.

On the first installed server, DNA has the full range of id_range values
to generate UIDs and GIDs. The first time a replica needs to generate a
UID/GID it requests a range and gets half of the allocation. A replica
does not automatically get a range on install. The more servers you have
AND the more replicas you've added entries on, the smaller the available
ranges may be. You can use ipa-replica-manage to display and manipulate
the ranges.

rob

>
>
>
>
>
> ------------------------------------------------------------------------
> *From:* Sam Morris via FreeIPA-users <freeipa-users@lists.fedorahosted.org>
> *Sent:* Monday, May 15, 2023 8:08 AM
> *To:* FreeIPA users list <freeipa-users@lists.fedorahosted.org>
> *Cc:* Alexander Bokovoy <abokovoy@redhat.com>; Sam Morris
> <sam@robots.org.uk>
> *Subject:* [Freeipa-users] Re: Authentication failures on a RHEL 9.2 IPA
> server
>
> On Mon, May 15, 2023 at 09:28:22AM +0300, Alexander Bokovoy via
> FreeIPA-users wrote:
>> On su, 14 touko 2023, Sam Morris wrote:
>> > On Fri, May 12, 2023 at 06:19:44PM +0100, Sam Morris via FreeIPA-users wrote:
>> > > I wonder about the root cause; is this because MIT Kerberos 1.20 always
>> > > wants to include a PAC in its issued TGTs, and it gives up if it can't
>> > > retrieve a user's SID from the directory? (If so I wonder if setting
>> > > disable_pac = true in the realm section of krb5.conf would have worked
>> > > around the problem?)
>> >
>> > This seems to be the case. Specifically I:
>> >
>> > 1. Removed the ipantsecurityidentifier attribute from a user, and
>> >    removed ipantuserattrs from the user's objectclass
>> > 2. Tried to log in as the user & got the same failures + 'No such file
>> >    or directory' message in /var/log/krb5kdc.log
>> > 3. Edited /var/kerberos/krb5kdc/kdc.conf, adding 'disable_pac = true'
>> >    within the realm-specific configuration in the realms section
>> > 4. Restarted krb5kdc
>> > 5. Tried to log in as the user and it worked!
>> >
>> > The docs for disable_pac say:
>> >
>> >    If true, the KDC will not issue PACs for this realm, and S4U2Self
>> >    and S4U2Proxy operations will be disabled. The default is false,
>> >    which will permit the KDC to issue PACs. New in release 1.20.
>> >
>> > ... which doesn't explain that if the KDC can't issue a PAC for some
>> > reason then the KDC will fail to issue the TGT. But at least I've gotten
>> > to the bottom of things now. :)
>>
>> RHEL IdM documentation has a separate chapter related to it.
>>
>> RHEL 9:
>> https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/9/html/managing_idm_users_groups_hosts_and_access_control_rules/assembly_strengthening-kerberos-security-with-pac-information_managing-users-groups-hosts
>>
>> RHEL 8:
>> https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html/managing_idm_users_groups_hosts_and_access_control_rules/assembly_strengthening-kerberos-security-with-pac-information_managing-users-groups-hosts
>>
>> This documentation is in place since summer 2022.
>
> Brilliant. It's interesting that the docs say "As of RHEL 8.6, Kerberos
> in IdM requires that your IdM objects have SIDs, which are necessary for
> security based on Privilege Access Certificate (PAC) information.", but
> I had no problems with authentication on my RHEL 8.6/8.7 servers...
>
>> > > "After upgrading, krb5kdc may fail to issue TGTs to users who have not
>> > > had a SID assigned to their accounts ('ipa user-show user --all' will
>> > > not include an ipantsecurityidentifier attribute). In this case
>> > > krb5kdc.log will log a message "HANDLE_AUTHDATA: user@EXAMPLE.COM for
>> > > krbtgt/EXAMPLE.COM@EXAMPLE.COM, No such file or directory". This can be
>> > > fixed by running 'ipa config-mod --enable-sid --add-sids' as an IPA
>> > > admin on another IPA server."
>> >
>> > ... "or on the same server after temporarily setting "disable_pac =
>> > true" in kdc.conf, and restarting krb5kdc."
>>
>> You should not be disabling PAC because you are really setting yourself
>> up to an attack with a known exploit out in a wild.
>
> Absolutely--I just wanted to document what I'd found out, because there
> isn't a clear connection documented between the behaviour in RHEL 9.2
> with MIT Kerberos 1.20 and the behaviour seen when your IPA users don't
> have SIDs assigned.
>
> --
> Sam Morris <https://robots.org.uk/>
> PGP: rsa4096/CAAA AA1A CA69 A83A 892B 1855 D20B 4202 5CDA 27B9
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