As described in the CSR [JDK-8241871], the Kerberos client does not currently support the 'canonicalize' setting in the configuration file (krb5.conf). As a result, Name Canonicalization behavior (described by RFC 6806) cannot be customized: the client will claim support for it in every TGT request if sun.security.krb5.disableReferrals is false, and the KDC service may change the client name. Even though this is RFC-compliant, it can be unexpected for some clients as we can see in the report below:

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ADDITIONAL SYSTEM INFORMATION :
$ cat /etc/lsb-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=18.04
DISTRIB_CODENAME=bionic
DISTRIB_DESCRIPTION="Ubuntu 18.04.4 LTS"

$ java -version
openjdk version "1.8.0_242"
OpenJDK Runtime Environment (build 1.8.0_242-8u242-b08-0ubuntu3~18.04-b08)
OpenJDK 64-Bit Server VM (build 25.242-b08, mixed mode)

A DESCRIPTION OF THE PROBLEM :
With 1.8.0_242 "client:" refers to the sAMAccountName of the object in AD, with 1.8.0_232 it used to refer to the servicePrincipalName (which is now "client alias:")

>>> DEBUG: ----Credentials----
       client: $V9H200-TAD2F4IK2G09@EXAMPLE.COM
       client alias: kafka/fqdn.example.com@EXAMPLE.COM
       server: zookeeper/fqdn.example.com@EXAMPLE.COM
       ticket: sname: zookeeper/fqdn.example.com@EXAMPLE.COM
       startTime: 1580465010000
       endTime: 1580501010000
       ----Credentials end----

So in some way with 1.8.0_232 zookeeper authenticated kafka/fqdn.example.com@EXAMPLE.COM while with 1.8.0_242 it is $V9H200-TAD2F4IK2G09@EXAMPLE.COM which leads to ACL problems in zookeeper.

REGRESSION : Last worked in version 8

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
# This is what we have:

user@host:~/work$ ls -al
total 20
drwxrwx--- 2 user user 4096 Feb 14 17:33 .
drwxr-xr-x 5 user user 4096 Feb 14 17:29 ..
-rw-rw---- 1 user user 942 Feb 14 17:29 KerberosDemo.java
-rw-rw---- 1 user user 101 Feb 13 13:13 jaas_cached.conf
-rw-rw---- 1 user user 276 Feb 13 13:24 jaas_keytab.conf


# it's a minimal example

user@host:~/work$ cat KerberosDemo.java
import javax.security.auth.login.*;
import java.util.Iterator;
import java.util.Set;
import javax.security.auth.Subject;
import javax.security.auth.kerberos.KerberosTicket;

public class KerberosDemo {
        public static void main (String[] args) {
                LoginContext loginContext = null;
                try {
                        loginContext = new LoginContext("Demo");
                }
                catch (LoginException e) {
                        System.err.println("login context creation failed: "+e.getMessage());
                        System.exit(1);
                }
                try {
                        loginContext.login();
                }
                catch (LoginException e) {
                        System.out.println("authentication failed");
                        System.exit(1);
                }
                Subject subject = loginContext.getSubject();
                System.out.println("Authenticated principal: " + subject.getPrincipals());
                Set credentials = subject.getPrivateCredentials();
                Iterator iterator = credentials.iterator();
                KerberosTicket kt = (KerberosTicket) iterator.next();
                System.out.println("Client name: " + kt.getClient());
        }
}


# let's compile it

user@host:~/work$ javac KerberosDemo.java


# and use it either with a keytab (JAAS is getting the ticket) ...

user@host:~/work$ cat jaas_keytab.conf # use keytab!
Demo {
    com.sun.security.auth.module.Krb5LoginModule required
    useKeyTab=true
    keyTab="/etc/security/keytabs/myprincipal.service.keytab"
    storeKey=true
    useTicketCache=false
    serviceName="serviceprincipal"
    principal="myprincipal/fqdn.example.com@EXAMPLE.COM";
};


# ... or with a ticket gotten earlier by MIT Kerberos client (kinit)

user@host:~/work$ cat jaas_cached.conf # use cached!
Demo {
    com.sun.security.auth.module.Krb5LoginModule required
    useKeyTab=false
    useTicketCache=true;
};


# this is how the ticket was placed in the cache

user@host:~/work$ kinit -kt /etc/security/keytabs/myprincipal.service.keytab myprincipal/fqdn.example.com@EXAMPLE.COM


# now, this is what happens with OpenJDK 1.8.0_232
# principal name and client name all refer to myprincipal/fqdn.example.com@EXAMPLE.COM (in AD, this is the servicePrincipalName):

user@host:~/work$ java -version
openjdk version "1.8.0_232"
OpenJDK Runtime Environment (build 1.8.0_232-8u232-b09-0ubuntu1~18.04.1-b09)
OpenJDK 64-Bit Server VM (build 25.232-b09, mixed mode)
user@host:~/work$ java -Djava.security.auth.login.config=jaas_keytab.conf KerberosDemo
Authenticated principal: [myprincipal/fqdn.example.com@EXAMPLE.COM]
Client name: myprincipal/fqdn.example.com@EXAMPLE.COM
user@host:~/work$ java -Djava.security.auth.login.config=jaas_cached.conf KerberosDemo
Authenticated principal: [myprincipal/fqdn.example.com@EXAMPLE.COM]
Client name: myprincipal/fqdn.example.com@EXAMPLE.COM


# while this is what we see with OpenJDK 1.8.0_242
# while for the cached ticket the results are the same, for the ticket gotten by JAAS the names differ!!!
# Note: $V9H200-TAD2F4IK2G09 is the sAMAccountName of the AD user with servicePrincipalName myprincipal/fqdn.example.com@EXAMPLE.COM

user@host:~/work$ java -version
openjdk version "1.8.0_242"
OpenJDK Runtime Environment (build 1.8.0_242-8u242-b08-0ubuntu3~18.04-b08)
OpenJDK 64-Bit Server VM (build 25.242-b08, mixed mode)
user@host:~/work$ java -Djava.security.auth.login.config=jaas_keytab.conf KerberosDemo
Authenticated principal: [myprincipal/fqdn.example.com@EXAMPLE.COM]
Client name: $V9H200-TAD2F4IK2G09@EXAMPLE.COM
user@host:~/work$ java -Djava.security.auth.login.config=jaas_cached.conf KerberosDemo
Authenticated principal: [myprincipal/fqdn.example.com@EXAMPLE.COM]
Client name: myprincipal/fqdn.example.com@EXAMPLE.COM

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
1.8.0_232 should behave the same as 1.8.0_242 so we can still run kafka/zookeeper.
ACTUAL -
When debugging Krb5 in Kafka/Zookeeper using OpenJDK 1.8.0_242 (this is where this bug hit me in the first place), the differing parts show up like this:

>>> DEBUG: ----Credentials----
       client: $V9H200-TAD2F4IK2G09@EXAMPLE.COM
       client alias: kafka/fqdn.example.com@EXAMPLE.COM
       server: zookeeper/fqdn.example.com@EXAMPLE.COM
       ticket: sname: zookeeper/fqdn.example.com@EXAMPLE.COM
       startTime: 1580465010000
       endTime: 1580501010000
       ----Credentials end----

So in some way with 1.8.0_232 zookeeper authenticated kafka/fqdn.example.com@EXAMPLE.COM while with 1.8.0_242 it is $V9H200-TAD2F4IK2G09@EXAMPLE.COM which leads to ACL problems in zookeeper.

---------- BEGIN SOURCE ----------
import javax.security.auth.login.*;
import java.util.Iterator;
import java.util.Set;
import javax.security.auth.Subject;
import javax.security.auth.kerberos.KerberosTicket;

public class KerberosDemo {
        public static void main (String[] args) {
                LoginContext loginContext = null;
                try {
                        loginContext = new LoginContext("Demo");
                }
                catch (LoginException e) {
                        System.err.println("login context creation failed: "+e.getMessage());
                        System.exit(1);
                }
                try {
                        loginContext.login();
                }
                catch (LoginException e) {
                        System.out.println("authentication failed");
                        System.exit(1);
                }
                Subject subject = loginContext.getSubject();
                System.out.println("Authenticated principal: " + subject.getPrincipals());
                Set credentials = subject.getPrivateCredentials();
                Iterator iterator = credentials.iterator();
                KerberosTicket kt = (KerberosTicket) iterator.next();
                System.out.println("Client name: " + kt.getClient());
        }
}
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
There are two workarounds:

1. Changing the JAAS config to use a ticket in the ticket cache created upfront using kinit. However this workaround can't be used in automated environments where clients authenticate themselves using keytabs.

2. Downgrade from OpenJDK 8 Update 242 to Update 232. Using the same configuration, the principal is authenticated as kafka/fqdn.example.com@EXAMPLE.COM. However, downgrading a package can only be a temporary solution.

FREQUENCY : always