Folks,
please consider the following case/bug with JGSS:
Tried with OpenJDK 8u4xx, can try newer, but doubt that it will be any
different.
* KDCs are Active Directory
* Machine: member of INNOMOTICS.NET
* krb5.conf: Default realm is INNOMOTICS.NET
* Client: Logged in from a different realm in this machine:
f...@ad001.siemens.net
* One-way trust from AD001.SIEMENS.NET, means with an account from
AD001.SIEMENS.NET you can access resources from both realms, but you
cannot access resources from AD001.SIEMENS.NET with your INNOMOTICS.NET
account. That is on purpose.
Use case:
Client wants to access AD DS via LDAP and authenticate with an SASL
GSSAPI bind: l...@dc1.ad001.siemens.net. Client and target realm are
identical. AS-REQ, AS-REP from AD001.SIEMENS.NET are fine, now here is
the problem: To form the TGS-REQ it requests a cross-realm TGT for
INNOMOTICS.NET and then asks a KDC in INNOMOTICS.NET for a service
ticket for l...@dc1.ad001.siemens.net. This KDC of course says:
16174 >>>KRBError:
16175 sTime is Thu Aug 29 20:19:07 CEST 2024 1724955547000
16176 suSec is 106542
16177 error code is 7
16178 error Message is Server not found in Kerberos database
16179 sname is ldap/dc1.ad001.siemens....@innomotics.net
16180 msgType is 30
End of story. The bug for me is that, for some reason, JGSS assumes that
the target is in the default realm of the machine instead of asking its
own realm which should give it all necessary cross-realm referrals.
Here is what MIT Kerberos does:
$ cat /etc/krb5.conf
# Kerberos configuration
[libdefaults]
default_realm = INNOMOTICS.NET
forwardable = true
canonicalize = true
dns_lookup_kdc = true
dns_canonicalize_hostname = false
qualify_shortname = ""
rdns = false
udp_preference_limit = 1
kdc_timeout = 1000
max_retries = 1
$ klist
Ticketzwischenspeicher: FILE:/tmp/krb5cc_2011
Standard-Principal: f...@ad001.siemens.net
Valid starting Expires Service principal
2024-08-30T10:13:05 2024-08-30T20:13:05
krbtgt/ad001.siemens....@ad001.siemens.net
erneuern bis 2024-08-31T10:10:22
$ ldapwhoami -H ldap://ad001.siemens.net
SASL/GSSAPI authentication started
SASL username: f...@ad001.siemens.net
SASL SSF: 256
SASL data security layer installed.
u:AD001\foo
$ klist
Ticketzwischenspeicher: FILE:/tmp/krb5cc_2011
Standard-Principal: f...@ad001.siemens.net
Valid starting Expires Service principal
2024-08-30T10:13:05 2024-08-30T20:13:05
krbtgt/ad001.siemens....@ad001.siemens.net
erneuern bis 2024-08-31T10:10:22
2024-08-30T10:13:19 2024-08-30T20:13:05 ldap/dc1.ad001.siemens.net@
erneuern bis 2024-08-31T10:10:22
Ticket server: ldap/dc1.ad001.siemens....@ad001.siemens.net
Also looking at the output of KRB5_TRACE and pcaps MIT Kerberos never
contacts any KDC in INNOMOTICS.NET.
The workaround is the following in krb5.conf:
# JGSS does not use the client's realm to obtain a ticket and needs this hinT
[domain_realm]
.ad001.siemens.net = AD001.SIEMENS.NET
ad001.siemens.net = AD001.SIEMENS.NET
This is ugly because:
* I have to do this on all affected machines and cannot rely on AD to
give me the right referral
* if I have an SPN, e.g. HTTP/svc.ad001.siemens.net in INNOMOTICS.NET, a
migrated machine from AD001.SIEMENS.NET to INNOMOTICS.NET available
under multiple virtual hostnames the init_sec_context will likely fail
because that SPN is not known AD001.SIEMENS.NET, I can hope that AD will
send me a referral. But in any case it will incur unnecessary round
trips. I need to explicitly exempt those hosts here throughout my setup.
Max, can you have a look at this? I can provide all the necessary
debug/trace/pcap files to you. Just let me know what you would like to see.
Michael
