A DESCRIPTION OF THE PROBLEM :
The parsing mechanism in sun/security/krb5/Config.java incorrect assumes only 3 types of lines are possible

1. a = b
2. a = {
3. }

auth_to_local rules in MIT Kerberos (which java follows) are of the format

a = {
  value
}

hence auth_to_local rules are impossible to read as a KrbException("Illegal config content") is thrown when encountering "value"

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Create a krb5.conf with auth_to_local rules like this (straight from MIT Kerberos man page)

         [realms]
              ATHENA.MIT.EDU = {
                  auth_to_local = {
                      RULE:[2:$1](johndoe)s/^.*$/guest/
                      RULE:[2:$1;$2](^.*;admin$)s/;admin$//
                      RULE:[2:$2](^.*;root)s/^.*$/root/
                      DEFAULT
                      }
                  }

try to use "get("realms", "ATHENA.MIT.EDU", "auth_to_local")

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
String of "auth_to_local" value.

ACTUAL -
KrbException("Illegal config content")