Configuring Trust Between Two Realms in One KDC: Step-by-Step Guide
As a beginner in the tech world, you may come across the term "trust between realms" when dealing with Kerberos authentication. Trust between realms allows users from one realm to access resources in another realm without having to create separate user accounts. In this step-by-step guide, we will walk you through the process of configuring trust between two realms in one KDC (Key Distribution Center).
What is a Realm?
A realm, in the context of Kerberos, is a logical unit that defines a security boundary. It represents a domain or a group of domains in a network. Each realm has its own KDC, which is responsible for authenticating and granting tickets to users.
Step 1: Understand the Setup
Before we begin, let's understand the setup we will be working with. In this guide, we will configure trust between two realms: Realm A and Realm B. Both realms are managed by the same KDC. The goal is to allow users from Realm A to access resources in Realm B without the need for separate user accounts.
Step 2: Configure Realm A
The first step is to configure Realm A to trust Realm B. Follow these steps:
- Open the Kerberos configuration file on the KDC server. The file is usually located at
/etc/krb5.conf. - Locate the
[realms]section and add the following lines:
[realms]
REALM-A = {
kdc = kdc.realm-a.com
admin_server = kdc.realm-a.com
}
REALM-B = {
kdc = kdc.realm-b.com
admin_server = kdc.realm-b.com
}
Replace REALM-A and REALM-B with the actual names of your realms. Also, replace kdc.realm-a.com and kdc.realm-b.com with the respective KDC server addresses.
- Save the configuration file and exit the editor.
- Restart the Kerberos service to apply the changes.
Step 3: Configure Realm B
Now, let's configure Realm B to trust Realm A:
- Open the Kerberos configuration file on the KDC server of Realm B.
- Locate the
[realms]section and add the following lines:
[realms]
REALM-A = {
kdc = kdc.realm-a.com
admin_server = kdc.realm-a.com
}
REALM-B = {
kdc = kdc.realm-b.com
admin_server = kdc.realm-b.com
default_domain = realm-b.com
auth_to_local = RULE:[1:$1@$0](^.*@REALM-A$)s/@.*//
}
Replace REALM-A and REALM-B with the actual names of your realms. Also, replace kdc.realm-a.com and kdc.realm-b.com with the respective KDC server addresses. The default_domain parameter should be set to the domain name of Realm B.
- Save the configuration file and exit the editor.
- Restart the Kerberos service to apply the changes.
Step 4: Create Trust Relationship
Now that both realms are configured to trust each other, we need to establish the trust relationship:
- On the KDC server of Realm A, open the Kerberos database administration tool.
- Execute the following command to create the trust relationship:
kadmin: addprinc -e "realm=REALM-B" krbtgt/REALM-B@REALM-A
Replace REALM-B with the name of Realm B. This command creates a principal in Realm A's KDC that represents the trust relationship with Realm B.
- On the KDC server of Realm B, open the Kerberos database administration tool.
- Execute the following command to create the trust relationship:
kadmin: addprinc -e "realm=REALM-A" krbtgt/REALM-A@REALM-B
Replace REALM-A with the name of Realm A. This command creates a principal in Realm B's KDC that represents the trust relationship with Realm A.
Step 5: Test the Trust Relationship
Finally, let's test the trust relationship between the two realms:
- On a client machine in Realm A, open a terminal and obtain a Kerberos ticket:
$ kinit user@REALM-A
- Now, try to access a resource in Realm B:
$ kinit user@REALM-B
If you can successfully obtain a ticket for Realm B without being prompted for a password, it means the trust relationship has been established correctly.
Conclusion
Congratulations! You have successfully configured trust between two realms in one KDC. This allows users from one realm to access resources in another realm without the need for separate user accounts. Remember, trust between realms simplifies authentication and enhances security in a network environment.
References
| Source | Link |
|---|---|
| Kerberos - MIT | https://web.mit.edu/kerberos/ |
| Kerberos - Wikipedia | https://en.wikipedia.org/wiki/Kerberos_(protocol) |