Re: Issues with GSSAPI kerberos authentication - realm undefined?

"Kyle Brantley" <kyle@xxxxxxxxxxxxxx> · Mon, 13 Apr 2020 13:22:02 -0600

Log here, but it’s not really any more illuminating: https://paste.centos.org/view/raw/ec0588a0
And filtered down to just lines that contain ‘sasl’: https://paste.centos.org/view/raw/ea345620

From what I can tell, the first time the SASL identity is shown in any form, the realm is absent. Timestamp of my “ldapwhois” is 13:04:52. Timestamp of me changing the logging back to 0 is 13:05:42.

Yes – the mapping succeeded – but that’s because I’ve removed the SASL mappings that check for the realm in specific.

(And sorry for the top-posting… I’m away from the computer where I sent my initial mail, I’ll respond in the future in a better format.)

Thanks,
--Kyle

From: Mark Reynolds <mreynolds@xxxxxxxxxx> 
Sent: Monday, April 13, 2020 12:59 PM
To: General discussion list for the 389 Directory server project. <389-users@xxxxxxxxxxxxxxxxxxxxxxx>; Kyle Brantley <kyle@xxxxxxxxxxxxxx>
Subject: [389-users] Re: Issues with GSSAPI kerberos authentication - realm undefined?

On 4/13/20 2:46 PM, Kyle Brantley wrote:
Thanks, Mark. I can tell that it’s an internal troubleshooting doc – and that’s great, thank you!

However, I… I don’t believe that I have any issues with my kerberos setup. The authentication from a pure krb5 perspective is happening appropriately. The tickets are being issued and I see the logs on the KDC confirming as much.

We have the pre-auth event:
kdc.averageurl.com krb5kdc[2432](info): AS_REQ (1 etypes {aes128-cts-hmac-sha1-96(17)}) 2001:470:xx:dae4: NEEDED_PREAUTH: kyletest@xxxxxxxxxxxxxx for krbtgt/AVERAGEURL.COM@xxxxxxxxxxxxxx, Additional pre-authentication required

The issuance of the kgbtgt ticket:
kdc.averageurl.com krb5kdc[2432](info): AS_REQ (1 etypes {aes128-cts-hmac-sha1-96(17)}) 2001:470:xx:dae4: ISSUE: authtime 1586803255, etypes {rep=aes128-cts-hmac-sha1-96(17), tkt=aes256-cts-hmac-sha1-96(18), ses=aes128-cts-hmac-sha1-96(17)}, kyletest@xxxxxxxxxxxxxx for krbtgt/AVERAGEURL.COM@xxxxxxxxxxxxxx

And finally, the ticket for ldap/ being issued as well:
kdc.averageurl.com krb5kdc[2433](info): TGS_REQ (1 etypes {aes128-cts-hmac-sha1-96(17))}) 2001:470:xx:dae4: ISSUE: authtime 1586803255, etypes {rep=aes128-cts-hmac-sha1-96(17), tkt=aes256-cts-hmac-sha1-96(18), ses=aes128-cts-hmac-sha1-96(17)}, kyletest@xxxxxxxxxxxxxx for ldap/ldaptest.averageurl.com@xxxxxxxxxxxxxx

The issue appears to be specific to what 389-ds is seeing as the realm:

DEBUG - ids_sasl_canon_user - (user=kyletest, realm=)

For reasons unknown to me, the realm isn’t being populated internally within 389-ds when the SASL mapping is taking place, even though kerberos is working as it should be.
The realm gets set by the cyrus-sasl library, the DS code has no control over it.  
Did you enable trace function call logging from the troubleshooting section of that doc?

ldapmodify -D "cn=directory manager" -W 
dn: cn=config 
changetype: modify 
replace: nsslapd-errorlog-level 
nsslapd-errorlog-level: 1

But beware, this is dramatically slow the server down.  So enable it, run your test, and then set the nsslapd-errorlog-level to "0" when you are done.  Please share the error log output from this test.
Thanks,
Mark

(This is the type of thing that I suspect needs to go on the bug tracker – but given how relatively little I know about administration of 389-ds I definitely wanted to check here in detail before I went over there.)

Thanks,
--Kyle

From: Mark Reynolds <mreynolds@xxxxxxxxxx> 
Sent: Monday, April 13, 2020 12:34 PM
To: General discussion list for the 389 Directory server project. <389-users@xxxxxxxxxxxxxxxxxxxxxxx>; Kyle Brantley <kyle@xxxxxxxxxxxxxx>
Subject: [389-users] Re: Issues with GSSAPI kerberos authentication - realm undefined?

On 4/13/20 2:30 PM, Mark Reynolds wrote:
Sorry not a kerberos expert but this is old doc I used to use to get it working.  I would double check your /etc/krb5.conf first though.
Here is that doc

I wanted to add this this document was for doing internal testing, so permission changes and password storage schemes changes should probably not be done in production.  The hope is that it will help figure out what is wrong in your setup...
Mark
===================================================================
SASL and DS
KDC Server

     - HOST.DOMAIN.COM is usually "localhost.localdomain" for internal testing.  Make sure the hostname is lowercase!

   [1]  ssh krbuser@xxxxxxxxxxxxxxxxxxx (password redhat)
   [2]  sudo /usr/kerberos/sbin/kadmin.local -r EXAMPLE.COM
   [3]  addprinc -randkey ldap/HOST.DOMAIN.COM@xxxxxxxxxxx
   [4]  ktadd -k /opt/ldap.HOST.DOMAIN.COM.keytab ldap/HOST.DOMAIN.COM@xxxxxxxxxxx
   [5]  addprinc sasltest  -> use redhat as password
   [6]  ktadd -k /opt/sasltest.keytab sasltest@xxxxxxxxxxx
   [7]  addprinc t001  --> use redhat as password
   [8]  ktadd -k /opt/ldap.t001.keytab t001@xxxxxxxxxxx
   [9]  exit
   [10] sudo chmod 777 /opt/ldap.HOST.DOMAIN.COM.keytab
   [11] sudo chmod 777 /opt/ldap.t001.keytab
   [12] sudo chmod 777 /opt/sasltest.keytab

DS Server

   - Get the keytabs

   [1]  cd /etc/dirsrv
   [2]  wget ftp://internal.redhat.com/opt/ldap.HOST.DOMAIN.COM.keytab
   [3]  wget ftp://internal.redhat.com/opt/sasltest.keytab
   [4]  wget ftp://internal.redhat.com/opt/ldap.t001.keytab

   - Edit /etc/krb5.conf, make sure these settings are included

    [libdefaults]

      default_realm: EXAMPLE.COM
      allow_weak_crypto = true (or 'yes')

    [realms]

    EXAMPLE.COM = {
      kdc = internal.redhat.com:88
      admin_server = internal.redhat.com:749
      default_domain = example.com
    }

    [domain_realm]
     .redhat.com = EXAMPLE.COM
     redhat.com = EXAMPLE.COM
     .example.com = EXAMPLE.COM
     example.com = EXAMPLE.COM

  - Edit /etc/sysconfig/dirsrv-INSTANCE

       Add these two lines to

         KRB5_CONFIG=/etc/krb5.conf
         KRB5_KTNAME=/etc/dirsrv/ldap.HOST.DOMAIN.COM.keytab

  - Edit the dse.ldif/ldapmodify.  This assumes there is a backend:  dc=example,dc=com

dn: cn=Kerberos uid mapping,cn=mapping,cn=sasl,cn=config
changetype: modify
replace: nsSaslMapBaseDNTemplate
nsSaslMapBaseDNTemplate: dc=example,dc=com

dn: cn=rfc 2829 dn syntax,cn=mapping,cn=sasl,cn=config
changetype: modify
replace: nsSaslMapBaseDNTemplate
nsSaslMapBaseDNTemplate: dc=example,dc=com

dn: cn=rfc 2829 u syntax,cn=mapping,cn=sasl,cn=config
changetype: modify
replace: nsSaslMapBaseDNTemplate
nsSaslMapBaseDNTemplate: dc=example,dc=com

dn: cn=uid mapping,cn=mapping,cn=sasl,cn=config
changetype: modify
replace: nsSaslMapBaseDNTemplate
nsSaslMapBaseDNTemplate: dc=example,dc=com

dn: cn=config
changetype: modify
add: passwordstoragescheme
passwordstoragescheme: clear

  - Add our user:

dn: uid=t001,ou=people,dc=example,dc=com
uid: t001
givenName: test
objectClass: top
objectClass: person
objectClass: organizationalPerson
objectClass: inetorgperson
sn: 001
cn: test 001
mail: t001@xxxxxxxxxxx

Testing

   [1]  cd /etc/dirsrv
   [2]  kinit -k -t ./ldap.t001.keytab t001@xxxxxxxxxxx
   [3]  klist

     Ticket cache: FILE:/tmp/krb5cc_0
     Default principal: t001@xxxxxxxxxxx

     Valid starting     Expires            Service principal
     02/08/10 14:29:33  02/09/10 14:29:33  krbtgt/EXAMPLE.COM@xxxxxxxxxxx
         renew until 02/08/10 14:29:33

   [4]  ldapsearch -h HOST.DOMAIN.COM -p 389  -b "dc=example,dc=com" -v -LLL -Y GSSAPI "uid=*" dn

   [5]  klist

    Ticket cache: FILE:/tmp/krb5cc_0
    Default principal: t001@xxxxxxxxxxx

    Valid starting     Expires            Service principal
    02/08/10 16:52:14  02/09/10 16:52:14  krbtgt/EXAMPLE.COM@xxxxxxxxxxx
        renew until 02/08/10 16:52:14
    02/08/10 16:52:20  02/09/10 16:52:14  ldap/HOST.DOMAIN.COM@xxxxxxxxxxx
        renew until 02/08/10 16:52:14

Troubleshooting

   [1]  To verify the DS server does use the user kerberos ticket for authentication, log on kdc server (internal.redhat.com), and tail -f /var/log/krb5kdc.log You should see following msgs in log:

        - The first msg means the usr "t001" does get valid kerberos ticket from kdc server
        - The second msg means the server which use "ldap/internal.redhat.com@xxxxxxxxxxx" is connect with kdc for user authentication

   Feb 08 16:46:14 internal.redhat.com krb5kdc[2726](info): AS_REQ (12 etypes {18 17 16 23 1 3 2 11 10 15 12 13}) 10.16.96.80: ISSUE: authtime 1265665574, etypes {rep=1 tkt=16 ses=16}, t001@xxxxxxxxxxx for krbtgt/EXAMPLE.COM@xxxxxxxxxxx

   Feb 08 16:48:34 internal.redhat.com krb5kdc[2726](info): TGS_REQ (7 etypes {18 17 16 23 1 3 2}) 10.16.96.80: ISSUE: authtime 1265665574, etypes {rep=16 tkt=16 ses=16}, t001@xxxxxxxxxxx for ldap/HOST.DOMAIN.COM.com@xxxxxxxxxxx

   [2]  ldapsearch issues

      [a] make sure you use -h "<FQDN>"

      [b] error:

        ldap_sasl_interactive_bind_s: Invalid credentials (49)
            additional info: SASL(-1): generic failure: GSSAPI Error: Unspecified GSS failure.  Minor code may provide more information (Unknown error)

        cause:  /etc/sysconfig/dirsrv-INSTANCE, the KRB5_KTNAME was incorrect

      [c] other errors, if you have verified the kerberos ticket is being used(see [1]), then recheck your sasl mappings in dse.ldif

   [3]  DS error logging, turn on "trace function calls" (nsslapd-errorlog-level: 1), this might provide more information.

================================================================

HTH,
Mark
On 4/12/20 12:41 PM, Kyle Brantley wrote:
I'm trying to move over from OpenLDAP, as it seems that 389-ds is better supported in the RH family of products. 

I've followed the RH docs to configure kerberos[1] as well as checking to ensure that the auth mechanisms are enabled and I've poked around with the SASL identity mappings. From what I can tell, all of these are setup correctly. 

However, every single time, the realm isn't populated with the kerberos realm and instead, only the username is passed. This results in the SASL mapping that matches the realm (correctly) failing to match: 

DEBUG - do_bind - BIND dn="" method=163 version=3 
DEBUG - ids_sasl_listmech - sasl library mechs: GSS-SPNEGO,GSSAPI,DIGEST-MD5,CRAM-MD5,PLAIN,LOGIN,ANONYMOUS 
DEBUG - ids_sasl_log - (5): GSSAPI server step 3 
DEBUG - ids_sasl_canon_user - (user=kyletest, realm=) 
DEBUG - sasl_map_domap - Trying map [Kerberos uid mapping] 
DEBUG - sasl_map_check - regex: (.*)@(.*)\.(.*), id: kyletest, didn't match 

I've trimmed the above to just the more relevant log lines, but it's very clear that the value for "realm" is en empty string. 

What do I need to do in order to have the realm be made visible to the SASL mapping component? I've searched the docs, both the fedora and the pagure bug trackers, searched all of the nsslapd-* attributes to see if I'm missing something, and tried on both centos8 and F31 (same results). I don't see anything obvious missing here (but I might just not know where to be looking). 

F31 package: 389-ds-base-1.4.2.11-1.fc31.x86_64 
CentOS8 package: 389-ds-base-1.4.2.9-1.module_el8+8314+9ac085f5.x86_64 

- Kerberos setup: 
[root@ldaptest ~]# cat /etc/sysconfig/dirsrv-app 
KRB5_KTNAME=/etc/dirsrv/krb5.keytab 
[root@ldaptest ~]# kinit -kt /etc/dirsrv/krb5.keytab ldap/$HOSTNAME 
[root@ldaptest ~]# klist 
Ticket cache: KCM:0:9594 
Default principal: ldap/ldaptest.averageurl.com@xxxxxxxxxxxxxx 

- klist after attempting an ldapwhoami: 
[root@ldaptest ~]# klist 
Ticket cache: KCM:0:39355 
Default principal: kyletest@xxxxxxxxxxxxxx 

Valid starting       Expires              Service principal 
04/12/2020 10:33:44  04/13/2020 10:33:40 krbtgt/AVERAGEURL.COM@xxxxxxxxxxxxxx 
04/12/2020 10:33:51  04/13/2020 10:33:40 ldap/ldaptest.averageurl.com@xxxxxxxxxxxxxx 

- SASL mapping: 
nsSaslMapRegexString: \(.*\)@\(.*\)\.\(.*\) 
nsSaslMapFilterTemplate: (cn=\1) 
nsSaslMapBaseDNTemplate: ou=accounts,dc=app,dc=averageurl,dc=com 

- Alternative SASL mapping that I'd prefer to use: 
nsSaslMapRegexString: \(.*\)@AVERAGEURL\.COM 
nsSaslMapFilterTemplate: (cn=\1) 
nsSaslMapBaseDNTemplate: ou=accounts,dc=app,dc=averageurl,dc=com 

Thanks, 
--Kyle 

[1] https://access.redhat.com/documentation/en-us/red_hat_directory_server/11/html/administration_guide/configuring_kerberos
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