Which of the following is a is a two way relationship that is automatically created between parent and child domains in a Microsoft Active Directory F?

33.6.1. Unique primary DNS domains

In Windows, every domain is a Kerberos realm and a DNS domain at the same time. Every domain managed by the domain controller needs to have its own dedicated DNS zone. The same applies when Identity Management (IdM) is trusted by Active Directory (AD) as a forest. AD expects IdM to have its own DNS domain. For the trust setup to work, the DNS domain needs to be dedicated to the Linux environment.

Each system must have its own unique primary DNS domain configured. For example:

• ad.example.com for AD and idm.example.com for IdM
• example.com for AD and idm.example.com for IdM
• ad.example.com for AD and example.com for IdM

The most convenient management solution is an environment where each DNS domain is managed by integrated DNS servers, but it is possible to use any other standard-compliant DNS server as well.

Kerberos realm names as upper-case versions of primary DNS domain names Kerberos realm names must be the same as the primary DNS domain names, with all letters uppercase. For example, if the domain names are ad.example.com for AD and idm.example.com for IdM, the Kerberos realm names are required to be AD.EXAMPLE.COM and IDM.EXAMPLE.COM. DNS records resolvable from all DNS domains in the trust All machines must be able to resolve DNS records from all DNS domains involved in the trust relationship. IdM and AD DNS Domains Systems joined to IdM can be distributed over multiple DNS domains. Red Hat recommends that you deploy IdM clients in a DNS zone different to the ones owned by Active Directory. The primary IdM DNS domain must have proper SRV records to support AD trusts.

In some environments with trusts between IdM and Active Directory, you can install an IdM client on a host that is part of the Active Directory DNS domain. The host can then benefit from the Linux-focused features of IdM. This is not a recommended configuration and has some limitations. See Configuring IdM clients in an Active Directory DNS domain for more details.

You can acquire a list of the required SRV records specific to your system setup by running the following command:

The generated list can look for example like this:

For other DNS domains that are part of the same IdM realm, it is not required for the SRV records to be configured when the trust to AD is configured. The reason is that AD domain controllers do not use SRV records to discover KDCs but rather base the KDC discovery on name suffix routing information for the trust.

33.6.2. Configuring a DNS forward zone in the IdM Web UI

This section describes how to add a DNS forward zone to the Identity Management (IdM) server by using the IdM Web UI.

With DNS forward zones, you can forward DNS queries for a specific zone to a different DNS server. For example, you can forward DNS queries for the Active Directory (AD) domain to an AD DNS server.

Prerequisites

• Access to the IdM Web UI with a user account that has administrator rights.
• Correctly configured DNS server.

Procedure

1. Log in to the IdM Web UI with administrator privileges. For details, see Accessing the IdM Web UI in a web browser.
2. Click on the Network Services tab.
3. Click on the DNS tab.

4. In the drop down menu, click on the DNS Forward Zones item.

   

5. Click on the Add button.
6. In the Add DNS forward zone dialog box, add a zone name.
7. In the Zone forwarders item, click on the Add button.
8. In the Zone forwarders field, add the IP address of the server for which you want to create the forward zone.

9. Click on the Add button.

   

The forwarded zone has been added to the DNS settings and you can verify it in the DNS Forward Zones settings. The Web UI informs you about success with the following pop-up message: DNS Forward Zone successfully added.

The Web UI might display a warning about a DNSSEC validation failure after adding a forward zone to the configuration.

DNSSEC (Domain Name System Security Extensions) secures DNS data with a digital signature to protect DNS from attacks. This service is enabled by default in the IdM server. The warning appears because the remote DNS server does not use DNSSEC. Red Hat recommends that you enable DNSSEC on the remote DNS server.

If you cannot enable DNSSEC validation on the remote server, you can disable DNSSEC in the IdM server:

1. Choose the appropriate configuration file to edit:

   • If your IdM server is using RHEL 8.0 or RHEL 8.1, open the /etc/named.conf file.
   • If your IdM server is using RHEL 8.2 or later, open the /etc/named/ipa-options-ext.conf file.

2. Add the following DNSSEC parameters:

   dnssec-enable no; dnssec-validation no;
3. Save and close the configuration file.

4. Restart the DNS service:

   # systemctl restart named-pkcs11

Verification steps

• Use the nslookup command with the name of the remote DNS server:

  $ nslookup ad.example.com Server: 192.168.122.2 Address: 192.168.122.2#53 No-authoritative answer: Name: ad.example.com Address: 192.168.122.3

  If you configured the domain forwarding correctly, the IP address of the remote DNS server is displayed.

33.6.3. Configuring a DNS forward zone in the CLI

This section describes how to add a new DNS forward zone to the Identity Management (IdM) server using the command line interface (CLI).

With DNS forward zones, you can forward DNS queries for a specific zone to a different DNS server. For example, you can forward DNS queries for the Active Directory (AD) domain to an AD DNS server.

Prerequisites

• Access to the CLI with a user account that has administrator rights.
• Correctly configured DNS server.

Procedure

• Create a DNS forward zone for the AD domain, and specify the IP address of the remote DNS server with the --forwarder option:

  # ipa dnsforwardzone-add ad.example.com --forwarder=192.168.122.3 --forward-policy=first

You might see a warning about a DNSSEC validation failure in the /var/log/messages system logs after adding a new forward zone to the configuration:

DNSSEC (Domain Name System Security Extensions) secures DNS data with a digital signature to protect DNS from attacks. This service is enabled by default in the IdM server. The warning appears because the remote DNS server does not use DNSSEC. Red Hat recommends that you enable DNSSEC on the remote DNS server.

If you cannot enable DNSSEC validation on the remote server, you can disable DNSSEC in the IdM server:

1. Choose the appropriate configuration file to edit:

   • If your IdM server is using RHEL 8.0 or RHEL 8.1, open the /etc/named.conf file.
   • If your IdM server is using RHEL 8.2 or later, open the /etc/named/ipa-options-ext.conf file.

2. Add the following DNSSEC parameters:

   dnssec-enable no; dnssec-validation no;
3. Save and close the configuration file.

4. Restart the DNS service:

   # systemctl restart named-pkcs11

Verification steps

• Use the nslookup command with the name of the remote DNS server:

  $ nslookup ad.example.com Server: 192.168.122.2 Address: 192.168.122.2#53 No-authoritative answer: Name: ad.example.com Address: 192.168.122.3

  If the domain forwarding is configured correctly, the nslookup request displays an IP address of the remote DNS server.

33.6.4. Configuring DNS forwarding in AD

This section describes how to set up a DNS forwarding in Active Directory (AD) for the Identity Management (IdM) server.

Prerequisites

• Windows Server with AD installed.
• DNS port open on both servers.

Procedure

1. Log in to the Windows Server.
2. Open Server Manager.
3. Open DNS Manager.

4. In Conditional Forwarders, add a new conditional forwarder with:

   • The IdM server IP address
   • A fully qualified domain name, for example, server.idm.example.com

5. Save the settings.

33.6.5. Verifying the DNS configuration

Before configuring trust, verify that the Identity Management (IdM) and Active Directory (AD) servers can resolve themselves and each other.

Prerequisites

• You need to be logged in with sudo permissions.

Procedure

1. Run a DNS query for the Kerberos over UDP and LDAP over TCP service records.

   [[email protected] ~]# dig +short -t SRV _kerberos._udp.idm.example.com. 0 100 88 server.idm.example.com. [[email protected] ~]# dig +short -t SRV _ldap._tcp.idm.example.com. 0 100 389 server.idm.example.com.

   The commands are expected to list all IdM servers.

2. Run a DNS query for the TXT record with the IdM Kerberos realm name. The obtained value is expected to match the Kerberos realm you specified when installing IdM.

   [[email protected] ~]# dig +short -t TXT _kerberos.idm.example.com. "IDM.EXAMPLE.COM"

   If the previous steps did not return all the expected records, update the DNS configuration with the missing records:

   • If your IdM environment uses an integrated DNS server, enter the ipa dns-update-system-records command without any options to update your system records:

     [[email protected] ~]$ ipa dns-update-system-records

   • If your IdM environment does not use an integrated DNS server:

     1. On the IdM server, export the IdM DNS records into a file:

        [[email protected] ~]$ ipa dns-update-system-records --dry-run --out dns_records_file.nsupdate

        The command creates a file named dns_records_file.nsupdate with the relevant IdM DNS records.

     2. Submit a DNS update request to your DNS server using the nsupdate utility and the dns_records_file.nsupdate file. For more information, see Updating External DNS Records Using nsupdate in RHEL 7 documentation. Alternatively, refer to your DNS server documentation for adding DNS records.

3. Verify that IdM is able to resolve service records for AD with a command that runs a DNS query for Kerberos and LDAP over TCP service records:

   [[email protected] ~]# dig +short -t SRV _kerberos._tcp.dc._msdcs.ad.example.com. 0 100 88 addc1.ad.example.com. [[email protected] ~]# dig +short -t SRV _ldap._tcp.dc._msdcs.ad.example.com. 0 100 389 addc1.ad.example.com.

33.7.1. Configuring an IdM client without Kerberos single sign-on

Password authentication is the only authentication method that is available for users to access resources on IdM clients if the IdM clients are in an Active Directory DNS domain. This procedure describes how to configure your client without Kerberos single sign-on.

Procedure

1. Install the IdM client with the --domain=IPA_DNS_Domain option to ensure the System Security Services Daemon (SSSD) can communicate with the IdM servers:

   [ ~]# ipa-client-install --domain=idm.example.com

   This option disables the SRV record auto-detection for the Active Directory DNS domain.

2. Open the /etc/krb5.conf configuration file and locate the existing mapping for the Active Directory domain in the [domain_realm] section.

   .ad.example.com = IDM.EXAMPLE.COM ad.example.com = IDM.EXAMPLE.COM

3. Replace both lines with an entry mapping the fully qualified domain name (FQDN) of the Linux clients in the Active Directory DNS zone to the IdM realm:

   idm-client.ad.example.com = IDM.EXAMPLE.COM

   By replacing the default mapping, you prevent Kerberos from sending its requests for the Active Directory domain to the IdM Kerberos Distribution Center (KDC). Instead Kerberos uses auto-discovery through SRV DNS records to locate the KDC.

33.7.2. Requesting SSL certificates without single sign-on

SSL-based services require a certificate with dNSName extension records that cover all system host names, because both original (A/AAAA) and CNAME records must be in the certificate. Currently, IdM only issues certificates to host objects in the IdM database.

In the described setup without single sign-on available, IdM already has a host object for the FQDN in the database, and certmonger can request a certificate using this name.

Prerequisites

• Installed and configured the IdM client by following the procedure in Configuring an IdM client without Kerberos single sign-on.

Procedure

• Use certmonger to request a certificate using the FQDN:

  [ ~]# ipa-getcert request -r \ -f /etc/httpd/alias/server.crt \ -k /etc/httpd/alias/server.key \ -N CN=ipa-client.ad.example.com \ -D ipa-client.ad.example.com \ -K host/ \ -U id-kp-serverAuth

The certmonger service uses the default host key stored in the /etc/krb5.keytab file to authenticate to the IdM Certificate Authority (CA).

33.7.3. Configuring an IdM client with Kerberos single sign-on

If you require Kerberos single sign-on to access resources on the IdM client, the client must be within the IdM DNS domain, for example idm-client.idm.example.com. You must create a CNAME record idm-client.ad.example.com in the Active Directory DNS domain pointing to the A/AAAA record of the IdM client.

For Kerberos-based application servers, MIT Kerberos supports a method to allow the acceptance of any host-based principal available in the application’s keytab.

Procedure

• On the IdM client, disable the strict checks on what Kerberos principal is used to target the Kerberos server by setting the following option in the [libdefaults] section of the /etc/krb5.conf configuration file:

  ignore_acceptor_hostname = true

33.7.4. Requesting SSL certificates with single sign-on

SSL-based services require a certificate with dNSName extension records that cover all system host names, because both original (A/AAAA) and CNAME records must be in the certificate. Currently, IdM only issues certificates to host objects in the IdM database.

This procedure describes how to to create a host object for ipa-client.example.com in IdM and make sure the real IdM machine’s host object is able to manage this host.

Prerequisites

• You have disabled the strict checks on what Kerberos principal is used to target the Kerberos server as outlined in Configuring an IdM client with Kerberos single sign-on.

Procedure

1. Create a new host object on the IdM server:

   [ ~]# ipa host-add idm-client.ad.example.com --force

   Use the --force option, because the host name is a CNAME and not an A/AAAA record.

2. On the IdM server, allow the IdM DNS host name to manage the Active Directory host entry in the IdM database:

   [ ~]# ipa host-add-managedby idm-client.ad.example.com \ --hosts=idm-client.idm.example.com

3. Your can now request an SSL certificate for your IdM client with the dNSName extension record for its host name within the Active Directory DNS domain:

   [ ~]# ipa-getcert request -r \ -f /etc/httpd/alias/server.crt \ -k /etc/httpd/alias/server.key \ -N CN=`hostname --fqdn` \ -D `hostname --fqdn` \ -D idm-client.ad.example.com \ -K host/ \ -U id-kp-serverAuth

33.8.1. Preparing the IdM server for the trust

Before you can establish a trust with AD, you must prepare the IdM domain using the ipa-adtrust-install utility on an IdM server.

Any system where you run the ipa-adtrust-install command automatically becomes an AD trust controller. However, you must run ipa-adtrust-install only once on an IdM server.

Prerequisites

• IdM server is installed.
• You need root privileges to install packages and restart IdM services.

Procedure

1. Install the required packages:

   [[email protected] ~]# yum install ipa-server-trust-ad samba-client

2. Authenticate as the IdM administrative user:

   [[email protected] ~]# kinit admin

3. Run the ipa-adtrust-install utility:

   [[email protected] ~]# ipa-adtrust-install

   The DNS service records are created automatically if IdM was installed with an integrated DNS server.

   If you installed IdM without an integrated DNS server, ipa-adtrust-install prints a list of service records that you must manually add to DNS before you can continue.

4. The script prompts you that the /etc/samba/smb.conf already exists and will be rewritten:

   WARNING: The smb.conf already exists. Running ipa-adtrust-install will break your existing Samba configuration. Do you wish to continue? [no]: yes

5. The script prompts you to configure the slapi-nis plug-in, a compatibility plug-in that allows older Linux clients to work with trusted users:

   Do you want to enable support for trusted domains in Schema Compatibility plugin? This will allow clients older than SSSD 1.9 and non-Linux clients to work with trusted users. Enable trusted domains support in slapi-nis? [no]: yes

6. When prompted, enter the NetBIOS name for the IdM domain or press Enter to accept the name suggested:

   Trust is configured but no NetBIOS domain name found, setting it now. Enter the NetBIOS name for the IPA domain. Only up to 15 uppercase ASCII letters, digits and dashes are allowed. Example: EXAMPLE. NetBIOS domain name [IDM]:

7. You are prompted to run the SID generation task to create a SID for any existing users:

   Do you want to run the ipa-sidgen task? [no]: yes

   This is a resource-intensive task, so if you have a high number of users, you can run this at another time.

8. (Optional) By default, the Dynamic RPC port range is defined as 49152-65535 for Windows Server 2008 and later. If you need to define a different Dynamic RPC port range for your environment, configure Samba to use different ports and open those ports in your firewall settings. The following example sets the port range to 55000-65000.

   [[email protected] ~]# net conf setparm global 'rpc server dynamic port range' 55000-65000 [[email protected] ~]# firewall-cmd --add-port=55000-65000/tcp [[email protected] ~]# firewall-cmd --runtime-to-permanent

9. Make sure that DNS is properly configured, as described in Verifying the DNS configuration for a trust.

   Red Hat strongly recommends you verify the DNS configuration as described in Verifying the DNS configuration for a trust every time after running ipa-adtrust-install, especially if IdM or AD do not use integrated DNS servers.

10. Restart the ipa service:

    [[email protected] ~]# ipactl restart

11. Use the smbclient utility to verify that Samba responds to Kerberos authentication from the IdM side:

    [[email protected] ~]# smbclient -L server.idm.example.com -U user_name --use-kerberos=required lp_load_ex: changing to config backend registry Sharename Type Comment --------- ---- ------- IPC$ IPC IPC Service (Samba 4.15.2) ...

33.8.2. Setting up a trust agreement using the command line

This section describes how to set up the trust agreement using the command line. The Identity Management (IdM) server allows you to configure three types of trust agreements:

• One-way trust — default option. One-way trust enables Active Directory (AD) users and groups to access resources in IdM, but not the other way around. The IdM domain trusts the AD forest, but the AD forest does not trust the IdM domain.

• Two-way trust — Two-way trust enables AD users and groups to access resources in IdM.

  You must configure a two-way trust for solutions such as Microsoft SQL Server that expect the S4U2Self and S4U2Proxy Microsoft extensions to the Kerberos protocol to work over a trust boundary. An application on a RHEL IdM host might request S4U2Self or S4U2Proxy information from an Active Directory domain controller about an AD user, and a two-way trust provides this feature.

  Note that this two-way trust functionality does not allow IdM users to login to Windows systems, and the two-way trust in IdM does not give the users any additional rights compared to the one-way trust solution in AD.

  • To create the two-way trust, add the following option to the command: --two-way=true

• External trust — a trust relationship between IdM and an AD domain in different forests. While a forest trust always requires establishing a trust between IdM and the root domain of an Active Directory forest, an external trust can be established from IdM to a domain within a forest. This is only recommended if it is not possible to establish a forest trust between forest root domains due to administrative or organizational reasons.

  • To create the external trust, add the following option to the command: --external=true

In this section, the steps below shows you how to create a one-way trust agreement.

Procedure

• Create a trust agreement for the AD domain and the IdM domain by using the ipa trust-add command:

  • To have SSSD automatically generate UIDs and GIDs for AD users based on their SID, create a trust agreement with the Active Directory domain ID range type. This is the most common configuration.

    [[email protected] ~]# ipa trust-add --type=ad ad.example.com --admin <ad_admin_username> --password --range-type=ipa-ad-trust

  • If you have configured POSIX attributes for your users in Active Directory (such as uidNumber and gidNumber) and you want SSSD to process this information, create a trust agreement with the Active Directory domain with POSIX attributes ID range type:

    [[email protected] ~]# ipa trust-add --type=ad ad.example.com --admin <ad_admin_username> --password --range-type=ipa-ad-trust-posix

If you do not specify an ID Range type when creating a trust, IdM attempts to automatically select the appropriate range type by requesting details from AD domain controllers in the forest root domain. If IdM does not detect any POSIX attributes, the trust installation script selects the Active Directory domain ID range.

If IdM detects any POSIX attributes in the forest root domain, the trust installation script selects the Active Directory domain with POSIX attributes ID range and assumes that UIDs and GIDs are correctly defined in AD. If POSIX attributes are not correctly set in AD, you will not be able to resolve AD users.

For example, if the users and groups that need access to IdM systems are not part of the forest root domain, but instead are located in a child domain of the forest domain, the installation script may not detect the POSIX attributes defined in the child AD domain. In this case, Red Hat recommends that you explicitly choose the POSIX ID range type when establishing the trust.

33.8.3. Setting up a trust agreement in the IdM Web UI

This section describes how to configure the Identity Management (IdM)/Active Directory (AD) trust agreement on the IdM side using the IdM Web UI.

Prerequisites

• DNS is correctly configured. Both IdM and AD servers must be able to resolve each other names.
• Supported versions of AD and IdM are deployed.
• You have obtained a Kerberos ticket.
• Before creating a trust in the Web UI, prepare the IdM server for the trust as described in: Preparing the IdM server for the trust.
• You need to be logged in as an IdM administrator.

Procedure

1. Log in to the IdM Web UI with administrator privileges. For details, see Accessing the IdM Web UI in a web browser.
2. In the IdM Web UI, click the IPA Server tab.
3. In the IPA Server tab, click the Trusts tab.

4. In the drop down menu, select the Trusts option.

   

5. Click the Add button.
6. In the Add Trust dialog box, enter the name of the Active Directory domain.

7. In the Account and Password fields, add the administrator credentials of the Active Directory administrator.

   

8. (Optional) Select Two-way trust, if you want to enable AD users and groups to access resources in IdM. However, the two-way trust in IdM does not give the users any additional rights compared to the one-way trust solution in AD. Both solutions are considered equally secure because of default cross-forest trust SID filtering settings.
9. (Optional) Select External trust if you are configuring a trust with an AD domain that is not the root domain of an AD forest. While a forest trust always requires establishing a trust between IdM and the root domain of an Active Directory forest, you can establish an external trust from IdM to any domain within an AD forest.

10. (Optional) By default, the trust installation script tries to detect the appropriate ID range type. You can also explicitly set the ID range type by choosing one of the following options:

    1. To have SSSD automatically generate UIDs and GIDs for AD users based on their SID, select the Active Directory domain ID range type. This is the most common configuration.

    2. If you have configured POSIX attributes for your users in Active Directory (such as uidNumber and gidNumber) and you want SSSD to process this information, select the Active Directory domain with POSIX attributes ID range type.

       

       If you leave the Range type setting on the default Detect option, IdM attempts to automatically select the appropriate range type by requesting details from AD domain controllers in the forest root domain. If IdM does not detect any POSIX attributes, the trust installation script selects the Active Directory domain ID range.

       If IdM detects any POSIX attributes in the forest root domain, the trust installation script selects the Active Directory domain with POSIX attributes ID range and assumes that UIDs and GIDs are correctly defined in AD. If POSIX attributes are not correctly set in AD, you will not be able to resolve AD users.

       For example, if the users and groups that need access to IdM systems are not part of the forest root domain, but instead are located in a child domain of the forest domain, the installation script may not detect the POSIX attributes defined in the child AD domain. In this case, Red Hat recommends that you explicitly choose the POSIX ID range type when establishing the trust.

11. Click Add.

Verification steps

• If the trust has been successfully added to the IdM server, you can see the green pop-up window in the IdM Web UI. It means that the:

  • Domain name exists

  • User name and password of the Windows Server has been added correctly.

    

Now you can continue to test the trust connection and Kerberos authentication.

33.8.4. Setting up a trust agreement using Ansible

This section describes how to set up a one-way trust agreement between Identity Management (IdM) and Active Directory (AD) by using an Ansible playbook. You can configure three types of trust agreements:

• One-way trust — default option. One-way trust enables Active Directory (AD) users and groups to access resources in IdM, but not the other way around. The IdM domain trusts the AD forest, but the AD forest does not trust the IdM domain.

• Two-way trust — Two-way trust enables AD users and groups to access resources in IdM.

  You must configure a two-way trust for solutions such as Microsoft SQL Server that expect the S4U2Self and S4U2Proxy Microsoft extensions to the Kerberos protocol to work over a trust boundary. An application on a RHEL IdM host might request S4U2Self or S4U2Proxy information from an Active Directory domain controller about an AD user, and a two-way trust provides this feature.

  Note that this two-way trust functionality does not allow IdM users to login to Windows systems, and the two-way trust in IdM does not give the users any additional rights compared to the one-way trust solution in AD.

  • To create the two-way trust, add the following variable to the playbook task below: two_way: true

• External trust — a trust relationship between IdM and an AD domain in different forests. While a forest trust always requires establishing a trust between IdM and the root domain of an Active Directory forest, an external trust can be established from IdM to a domain within a forest. This is only recommended if it is not possible to establish a forest trust between forest root domains due to administrative or organizational reasons.

  • To create the external trust, add the following variable to the playbook task below: external: true

Prerequisites

• User name and password of a Windows administrator.
• The IdM admin password.
• You have prepared the IdM server for the trust.
• You are using the 4.8.7 version of IdM or later. To view the version of IdM you have installed on your server, run ipa --version.

• You have configured an Ansible control node that meets the following requirements:

  • You are using Ansible version 2.8 or later.
  • You have installed the ansible-freeipa package.
  • In the ~/MyPlaybooks/ directory, you have created an Ansible inventory file with the fully-qualified domain name (FQDN) of the IdM server where you are configuring the trust.

Procedure

1. Navigate to your ~/MyPlaybooks/ directory:

   $ cd ~/MyPlaybooks/

2. Select one of the following scenarios based on your use case:

   • To create an ID mapping trust agreement, in which SSSD automatically generates UIDs and GIDs for AD users and groups based on their SIDs, create an add-trust.yml playbook with the following content:

     --- - name: Playbook to create a trust hosts: ipaserver become: true tasks: - name: ensure the trust is present ipatrust: ipaadmin_password: SomeADMINpassword realm: ad.example.com admin: Administrator password: secret_password range_type: ipa-ad-trust state: present

     In the example:

     • realm defines the AD realm name string.
     • admin defines the AD domain administrator string.
     • password defines the AD domain administrator’s password string.

   • To create a POSIX trust agreement, in which SSSD processes POSIX attributes stored in AD, such as uidNumber and gidNumber, create an add-trust.yml playbook with the following content:

     --- - name: Playbook to create a trust hosts: ipaserver become: true tasks: - name: ensure the trust is present ipatrust: ipaadmin_password: SomeADMINpassword realm: ad.example.com admin: Administrator password: secret_password range_type: ipa-ad-trust-posix state: present

   • To create a trust agreement in which IdM attempts to automatically select the appropriate range type, ipa-ad-trust or ipa-ad-trust-posix, by requesting details from AD domain controllers in the forest root domain, create an add-trust.yml playbook with the following content:

     --- - name: Playbook to create a trust hosts: ipaserver become: true tasks: - name: ensure the trust is present ipatrust: ipaadmin_password: SomeADMINpassword realm: ad.example.com admin: Administrator password: secret_password state: present

   If you do not specify an ID range type when creating a trust, and if IdM does not detect any POSIX attributes in the AD forest root domain, the trust installation script selects the Active Directory domain ID range.

   If IdM detects any POSIX attributes in the forest root domain, the trust installation script selects the Active Directory domain with POSIX attributes ID range and assumes that UIDs and GIDs are correctly defined in AD.

   However, if POSIX attributes are not correctly set in AD, you will not be able to resolve AD users. For example, if the users and groups that need access to IdM systems are not part of the forest root domain, but instead are located in a child domain of the forest domain, the installation script may not detect the POSIX attributes defined in the child AD domain. In this case, Red Hat recommends that you explicitly choose the POSIX ID range type when establishing the trust.

3. Save the file.

4. Run the Ansible playbook specifying the playbook file and the inventory file:

   $ ansible-playbook -v -i inventory add-trust.yml

Additional resources

• /usr/share/doc/ansible-freeipa/README-trust.md
• /usr/share/doc/ansible-freeipa/playbooks/trust

33.8.5. Verifying the Kerberos configuration

To verify the Kerberos configuration, test if it is possible to obtain a ticket for an Identity Management (IdM) user and if the IdM user can request service tickets.

Procedure

1. Request a ticket for an Active Directory (AD) user:

   [[email protected] ~]# kinit

2. Request service tickets for a service within the IdM domain:

   [[email protected] ~]# kvno -S host server.idm.example.com

   If the AD service ticket is successfully granted, there is a cross-realm ticket-granting ticket (TGT) listed with all of the other requested tickets. The TGT is named krbtgt/.

The localauth plug-in maps Kerberos principals to local System Security Services Daemon (SSSD) user names. This allows AD users to use Kerberos authentication and access Linux services, which support GSSAPI authentication directly.

33.8.6. Verifying the trust configuration on IdM

Before configuring trust, verify that the Identity Management (IdM) and Active Directory (AD) servers can resolve themselves and each other.

Prerequisites

• You need to be logged in with administrator privileges.

Procedure

1. Run a DNS query for the MS DC Kerberos over UDP and LDAP over TCP service records.

   [[email protected] ~]# dig +short -t SRV _kerberos._udp.dc._msdcs.idm.example.com. 0 100 88 server.idm.example.com. [[email protected] ~]# dig +short -t SRV _ldap._tcp.dc._msdcs.idm.example.com. 0 100 389 server.idm.example.com.

   These commands list all IdM servers on which ipa-adtrust-install has been executed. The output is empty if ipa-adtrust-install has not been executed on any IdM server, which is typically before establishing the first trust relationship.

2. Run a DNS query for the Kerberos and LDAP over TCP service records to verify that IdM is able to resolve service records for AD:

   [[email protected] ~]# dig +short -t SRV _kerberos._tcp.dc._msdcs.ad.example.com. 0 100 88 addc1.ad.example.com. [[email protected] ~]# dig +short -t SRV _ldap._tcp.dc._msdcs.ad.example.com. 0 100 389 addc1.ad.example.com.

.

33.8.7. Verifying the trust configuration on AD

After configuring the trust, verify that:

• The Identity Management (IdM)-hosted services are resolvable from the Active Directory (AD) server.
• AD services are resolvable from the AD server.

Prerequisites

• You need to be logged in with administrator privileges.

Procedure

1. On the AD server, set the nslookup.exe utility to look up service records.

   C:\>nslookup.exe > set type=SRV

2. Enter the domain name for the Kerberos over UDP and LDAP over TCP service records.

   > _kerberos._udp.idm.example.com. _kerberos._udp.idm.example.com. SRV service location: priority = 0 weight = 100 port = 88 svr hostname = server.idm.example.com > _ldap._tcp.idm.example.com _ldap._tcp.idm.example.com SRV service location: priority = 0 weight = 100 port = 389 svr hostname = server.idm.example.com

3. Change the service type to TXT and run a DNS query for the TXT record with the IdM Kerberos realm name.

   C:\>nslookup.exe > set type=TXT > _kerberos.idm.example.com. _kerberos.idm.example.com. text = "IDM.EXAMPLE.COM"

4. Run a DNS query for the MS DC Kerberos over UDP and LDAP over TCP service records.

   C:\>nslookup.exe > set type=SRV > _kerberos._udp.dc._msdcs.idm.example.com. _kerberos._udp.dc._msdcs.idm.example.com. SRV service location: priority = 0 weight = 100 port = 88 svr hostname = server.idm.example.com > _ldap._tcp.dc._msdcs.idm.example.com. _ldap._tcp.dc._msdcs.idm.example.com. SRV service location: priority = 0 weight = 100 port = 389 svr hostname = server.idm.example.com

   Active Directory only expects to discover domain controllers that can respond to AD-specific protocol requests, such as other AD domain controllers and IdM trust controllers. Use the ipa-adtrust-install tool to promote an IdM server to a trust controller, and you can verify which servers are trust controllers with the ipa server-role-find --role 'AD trust controller' command.

5. Verify that AD services are resolvable from the AD server.

   C:\>nslookup.exe > set type=SRV

6. Enter the domain name for the Kerberos over UDP and LDAP over TCP service records.

   > _kerberos._udp.dc._msdcs.ad.example.com. _kerberos._udp.dc._msdcs.ad.example.com. SRV service location: priority = 0 weight = 100 port = 88 svr hostname = addc1.ad.example.com > _ldap._tcp.dc._msdcs.ad.example.com. _ldap._tcp.dc._msdcs.ad.example.com. SRV service location: priority = 0 weight = 100 port = 389 svr hostname = addc1.ad.example.com

33.8.8. Creating a trust agent

A trust agent is an IdM server that can perform identity lookups against AD domain controllers.

For example, if you are creating a replica of an IdM server that has a trust with Active Directory, you can set up the replica as a trust agent. A replica does not automatically have the AD trust agent role installed.

Prerequisites

• IdM is installed with an Active Directory trust.
• The sssd-tools package is installed.

Procedure

1. On an existing trust controller, run the ipa-adtrust-install --add-agents command:

   [[email protected]_trust_controller]# ipa-adtrust-install --add-agents

   The command starts an interactive configuration session and prompts you for the information required to set up the agent.

2. Restart the IdM service on the trust agent.

   [[email protected]_trust_agent]# ipactl restart

3. Remove all entries from the SSSD cache on the trust agent:

   [[email protected]_trust_agent]# sssctl cache-remove

4. Verify that the replica has the AD trust agent role installed:.

   [[email protected]_trust_controller]# ipa server-show new_replica.idm.example.com ... Enabled server roles: CA server, NTP server, AD trust agent

Additional resources

• For further information about the --add-agents option, see the ipa-adtrust-install(1) man page.
• For more information on trust agents, see Trust controllers and trust agents in the Planning Identity Management guide.

33.8.9. Enabling automatic private group mapping for a POSIX ID range on the CLI

By default, SSSD does not map private groups for Active Directory (AD) users if you have established a POSIX trust that relies on POSIX data stored in AD. If any AD users do not have primary groups configured, IdM is not be able to resolve them.

This procedure explains how to enable automatic private group mapping for an ID range by setting the hybrid option for the auto_private_groups SSSD parameter on the command line. As a result, IdM is able to resolve AD users that do not have primary groups configured in AD.

Prerequisites

• You have successfully established a POSIX cross-forest trust between your IdM and AD environments.

Procedure

1. Display all ID ranges and make note of the AD ID range you want to modify.

   [[email protected] ~]# ipa idrange-find ---------------- 2 ranges matched ---------------- Range name: IDM.EXAMPLE.COM_id_range First Posix ID of the range: 882200000 Number of IDs in the range: 200000 Range type: local domain range Range name: AD.EXAMPLE.COM_id_range First Posix ID of the range: 1337000000 Number of IDs in the range: 200000 Domain SID of the trusted domain: S-1-5-21-4123312420-990666102-3578675309 Range type: Active Directory trust range with POSIX attributes ---------------------------- Number of entries returned 2 ----------------------------

2. Adjust the automatic private group behavior for the AD ID range with the ipa idrange-mod command.

   [[email protected] ~]# ipa idrange-mod --auto-private-groups=hybrid AD.EXAMPLE.COM_id_range

3. Reset the SSSD cache to enable the new setting.

   [[email protected] ~]# sss_cache -E

33.8.10. Enabling automatic private group mapping for a POSIX ID range in the IdM WebUI

By default, SSSD does not map private groups for Active Directory (AD) users if you have established a POSIX trust that relies on POSIX data stored in AD. If any AD users do not have primary groups configured, IdM is not be able to resolve them.

This procedure explains how to enable automatic private group mapping for an ID range by setting the hybrid option for the auto_private_groups SSSD parameter in the Identity Management (IdM) WebUI. As a result, IdM is able to resolve AD users that do not have primary groups configured in AD.

Prerequisites

• You have successfully established a POSIX cross-forest trust between your IdM and AD environments.

Procedure

1. Log into the IdM Web UI with your user name and password.
2. Open the IPA Server → ID Ranges tab.
3. Select the ID range you want to modify, such as AD.EXAMPLE.COM_id_range.

4. From the Auto private groups drop down menu, select the hybrid option.

   

5. Click the Save button to save your changes.

33.9.1. Sequence of events when establishing a cross-forest trust with AD

When you use the ipa trust-add command to establish a cross-forest trust with an Active Directory (AD) Domain Controller (DC), the command operates on behalf of the user who ran the command and performs the following actions on the IdM server. If you have trouble establishing a cross-forest trust, you can use this list to help narrow down and troubleshoot your issue.

Part 1: The command verifies settings and inputs

1. Verify that the IdM server has the Trust Controller role.
2. Validate the options passed to the ipa trust-add command.
3. Validate the ID range associated with a trusted forest root domain. If you did not specify the ID range type and properties as options to the ipa trust-add command, they are discovered from Active Directory.

Part 2: The command attempts to establish a trust to an Active Directory domain

1. Create a separate trust object for each trust direction. Each of the objects get created on both sides (IdM and AD). If you are establishing a one-way trust, only one object is created on each side.

2. The IdM server uses the Samba suite to handle domain controller capabilities for Active Directory and creates a trust object on the target AD PDC:

   1. The IdM server establishes a secure connection to the IPC$ share on the target DC. Since RHEL 8.4, the connection requires at least the SMB3 protocol with Windows Server 2012 and above to ensure the connection is sufficiently secure with AES-based encryption used for the session.
   2. The IdM server queries for the presence of the trusted domain object (TDO) using an LSA QueryTrustedDomainInfoByName call.

   3. If the TDO is already present, remove it with an LSA DeleteTrustedDomain call.

      This call fails if the AD user account used to establish the trust does not have full Enterprise Admin (EA) or Domain Admin (DA) privileges for the forest root, such as members of the Incoming Forest Trust Builders group. If the old TDO is not automatically removed, an AD Administrator must manually remove it from AD.

   4. The IdM server creates a new TDO with an LSA CreateTrustedDomainEx2 call. The TDO credentials are randomly generated using a Samba-provided password generator with 128 random characters.

   5. The new TDO is then modified with an LSA SetInformationTrustedDomain call to make sure encryption types supported by the trust are set properly:

      1. The RC4_HMAC_MD5 encryption type is enabled, even if there are no RC4 keys in use, due to how Active Directory is designed.
      2. AES128_CTS_HMAC_SHA1_96 and AES256_CTS_HMAC_SHA1_96 encryption types are enabled.

3. For a forest trust, verify that in-forest domains can be reached transitively with an LSA SetInformationTrustedDomain call.

4. Add trust topology information about the other forest (IdM in the case of communicating with AD, AD in the case of communicating with IdM) using an LSA RSetForestTrustInformation call.

   This step might cause a conflict for one of three reasons:

   1. A SID namespace conflict, reported as an LSA_SID_DISABLED_CONFLICT error. This conflict cannot be resolved.
   2. A NetBIOS namespace conflict, reported as an LSA_NB_DISABLED_CONFLICT error. This conflict cannot be resolved.
   3. A DNS namespace conflict with a top level name (TLN), reported as an LSA_TLN_DISABLED_CONFLICT error. The IdM server can automatically resolve a TLN conflict if it is caused by another forest.

   To resolve a TLN conflict, the IdM server performs the following steps:

   1. Retrieve forest trust information for the conflicting forest.
   2. Add an exclusion entry for the IdM DNS namespace to the AD forest.
   3. Set forest trust information for the forest we conflict on.
   4. Re-try establishing the trust to the original forest.

   The IdM server can only resolve these conflicts if you authenticated the ipa trust-add command with the privileges of an AD administrator that can change forest trusts. If you do not have access to those privileges, the administrator of the original forest must manually perform the steps above in the Active Directory Domains and Trusts section of the Windows UI.

5. If it does not exist, create the ID range for the trusted domain.
6. For a forest trust, query Active Directory domain controllers from the forest root for details about the forest topology. The IdM server uses this information to create additional ID ranges for any additional domains from the trusted forest.

33.10.1. Flow of information when a host in the AD forest root domain requests services from an IdM server

The following diagram explains the flow of information when an Active Directory (AD) client requests a service in the Identity Management (IdM) domain.

If you have trouble accessing IdM services from AD clients, you can use this information to narrow your troubleshooting efforts and identify the source of the issue.

1. The AD client contacts the AD Kerberos Distribution Center (KDC) to perform a TGS Request for the service in the IdM domain.
2. The AD KDC recognizes that the service belongs to the trusted IdM domain.
3. The AD KDC sends the client a cross-realm ticket-granting ticket (TGT), along with a referral to the trusted IdM KDC.
4. The AD client uses the cross-realm TGT to request a ticket to the IdM KDC.
5. The IdM KDC validates the Privileged Attribute Certificate (MS-PAC) that is transmitted with the cross-realm TGT.
6. The IPA-KDB plugin might check the LDAP directory to see if foreign principals are allowed to get tickets for the requested service.
7. The IPA-KDB plugin decodes the MS-PAC, verifies, and filters the data. It performs lookups in the LDAP server to check if it needs to augment the MS-PAC with additional information, such as local groups.
8. The IPA-KDB plugin then encodes the PAC, signs it, attaches it to the service ticket, and sends it to the AD client.
9. The AD client can now contact the IdM service using the service ticket issued by IdM KDC.

33.10.2. Flow of information when a host in an AD child domain requests services from an IdM server

The following diagram explains the flow of information when an Active Directory (AD) host in a child domain requests a service in the Identity Management (IdM) domain. In this scenario, the AD client contacts the Kerberos Distribution Center (KDC) in the child domain, then contacts the KDC in the AD forest root, and finally contacts the IdM KDC to request access to the IdM service.

If you have trouble accessing IdM services from AD clients, and your AD client belongs to a domain that is a child domain of an AD forest root, you can use this information to narrow your troubleshooting efforts and identify the source of the issue.

1. The AD client contacts the AD Kerberos Distribution Center (KDC) in its own domain to perform a TGS Request for the service in the IdM domain.
2. The AD KDC in child.ad.example.com, the child domain, recognizes that the service belongs to the trusted IdM domain.
3. The AD KDC in the child domain sends the client a referral ticket for the AD forest root domain ad.example.com.
4. The AD client contacts the KDC in the AD forest root domain for the service in the IdM domain.
5. The KDC in the forest root domain recognizes that the service belongs to the trusted IdM domain.
6. The AD KDC sends the client a cross-realm ticket-granting ticket (TGT), along with a referral to the trusted IdM KDC.
7. The AD client uses the cross-realm TGT to request a ticket to the IdM KDC.
8. The IdM KDC validates the Privileged Attribute Certificate (MS-PAC) that is transmitted with the cross-realm TGT.
9. The IPA-KDB plugin might check the LDAP directory to see if foreign principals are allowed to get tickets for the requested service.
10. The IPA-KDB plugin decodes the MS-PAC, verifies, and filters the data. It performs lookups in the LDAP server to check if it needs to augment the MS-PAC with additional information, such as local groups.
11. The IPA-KDB plugin then encodes the PAC, signs it, attaches it to the service ticket, and sends it to the AD client.
12. The AD client can now contact the IdM service using the service ticket issued by IdM KDC.