Add example of binding with kerberos

[sshanks-kx]

Example building/using ldapsearch in kerberos env:

Example env: https://github.com/antagme/Documentation_Project/blob/master/example1fast.md

Creating container to add with our own ldap/etc build...

1. Edit Dockerfile.build (in this repo) to have yum install of openssl and cyrus-sasl-devel (ldap must be built with sasl api)
2. build docker build -f Dockerfile.build -t ldapdev .
3. run in env docker run -it --rm --name ldapdev --net ldap --ip 172.18.0.4 ldapdev
4. install gssapi/krb tools yum install -y cyrus-sasl-gssapi krb5-workstation
5. add IP of other machines to /etc/hosts

   172.18.0.2 ldap.edt.org
   172.18.0.3 kserver.edt.org
   172.18.0.8 client.edt.org

6. change /etc/krb5.conf to

   [logging]
   default = FILE:/var/log/krb5libs.log
   kdc = FILE:/var/log/krb5kdc.log
   admin_server = FILE:/var/log/kadmind.log
   [libdefaults]
   dns_lookup_realm = false
   ticket_lifetime = 24h
   renew_lifetime = 7d
   forwardable = true
   rdns = false
   default_realm = EDT.ORG
   [realms]
   EDT.ORG = {
   kdc = kserver.edt.org
   admin_server = kserver.edt.org
   }
   [domain_realm]
   .edt.org = EDT.ORG
   edt.org = EDT.ORG

7. login kinit user01 (password kuser01)
8. run ldapsearch e.g. LD_LIBRARY_PATH=/usr/lib/:$LD_LIBRARY_PATH ldapsearch -H ldap://ldap.edt.org -D 'dc=edt,dc=org' -Y GSSAPI -v

Possible error msgs if various packages/etc not installed

NO cyrus-sasl-devel error msg on compile time: ldapsearch: not compiled with SASL support

NO cyrus-sasl-gssapi or cyrus-sasl-devel error msg: ldap_sasl_interactive_bind: Unknown authentication method (-6) additional info: SASL(-4): no mechanism available: No worthy mechs found

NO kinit ran to login, error msg: ldap_sasl_interactive_bind: Local error (-2) additional info: SASL(-1): generic failure: GSSAPI Error: Unspecified GSS failure. Minor code may provide more information (No Kerberos credentials available (default cache: FILE:/tmp/krb5cc_0))