Menu Close

Installing trust between IdM and AD

Red Hat Enterprise Linux 9

Configuring a cross-forest trust between an IdM domain and an Active Directory domain.

Red Hat Customer Content Services

Abstract

This documentation collection provides instructions on how to create a trust between an Identity Management deployment and an Active Directory (AD) environment.

Making open source more inclusive

Red Hat is committed to replacing problematic language in our code, documentation, and web properties. We are beginning with these four terms: master, slave, blacklist, and whitelist. Because of the enormity of this endeavor, these changes will be implemented gradually over several upcoming releases. For more details, see our CTO Chris Wright’s message.

In Identity Management, planned terminology replacements include:

  • block list replaces blacklist
  • allow list replaces whitelist
  • secondary replaces slave
  • The word master is being replaced with more precise language, depending on the context:

    • IdM server replaces IdM master
    • CA renewal server replaces CA renewal master
    • CRL publisher server replaces CRL master
    • multi-supplier replaces multi-master

Providing feedback on Red Hat documentation

We appreciate your input on our documentation. Please let us know how we could make it better.

  • For simple comments on specific passages:

    1. Make sure you are viewing the documentation in the Multi-page HTML format. In addition, ensure you see the Feedback button in the upper right corner of the document.
    2. Use your mouse cursor to highlight the part of text that you want to comment on.
    3. Click the Add Feedback pop-up that appears below the highlighted text.
    4. Follow the displayed instructions.
  • For submitting feedback via Bugzilla, create a new ticket:

    1. Go to the Bugzilla website.
    2. As the Component, use Documentation.
    3. Fill in the Description field with your suggestion for improvement. Include a link to the relevant part(s) of documentation.
    4. Click Submit Bug.

Chapter 1. Prerequisites for establishing a trust

This documentation aims to help you create a trust between your Identity Management IdM server and Active Directory (AD), where both servers are located in the same forest.

Prerequisites

  • First, read the Planning a cross-forest trust between Identity Management and Active Directory document.
  • AD is installed with a domain controller on it.
  • The IdM server is installed and running.

    For details, see Installing Identity Management.

  • Both the AD server and the IdM server must have their clocks in sync because Kerberos requires max 5 mins delay in communication.
  • Unique NetBIOS names for each of the servers placed in the trust because the NetBIOS names are critical for identifying the Active Directory domain.

    The NetBIOS name of an Active Directory or IdM domain is usually the first part of the corresponding DNS domain. If the DNS domain is ad.example.com, the NetBIOS name is typically AD. However, it is not required. Important is that the NetBIOS name is just one word without periods. The maximum length of a NetBIOS name is 15 characters.

  • The IdM system must have the IPv6 protocol enabled in the kernel.

    If IPv6 is disabled, then the CLDAP plug-in used by the IdM services fails to initialize.

Chapter 2. Supported versions of Windows Server

Identity Management (IdM) does not support establishing trust to Active Directory with Active Directory domain controllers running Windows Server 2008 R2 or earlier versions. RHEL IdM requires SMB encryption when establishing the trust relationship, which is only supported in Windows Server 2012 or later.

You can establish a trust relationship with Active Directory (AD) forests that use the following forest and domain functional levels:

  • Forest functional level range: Windows Server 2012 — Windows Server 2016
  • Domain functional level range: Windows Server 2012 — Windows Server 2016

Identity Management (IdM) supports establishing a trust with Active Directory domain controllers running the following operating systems:

  • Windows Server 2012
  • Windows Server 2012 R2
  • Windows Server 2016
  • Windows Server 2019

Chapter 3. How the trust works

The trust between Identity Management IdM and Active Directory (AD) is established on the Cross-realm Kerberos trust. This solution uses the Kerberos capability to establish trusts between different identity sources. Therefore, all AD users can:

  • Log in to access Linux systems and resources.
  • Use single sign-on (SSO).

All IdM objects are managed in IdM in the trust.

All AD objects are managed in AD in the trust.

In complex environments, a single IdM forest can be connected to multiple AD forests. This setup enables better separation of duties for different functions in the organization. AD administrators can focus on users and policies related to users while Linux administrators have full control over the Linux infrastructure. In such a case, the Linux realm controlled by IdM is analogous to an AD resource domain or realm but with Linux systems in it.

From the perspective of AD, Identity Management represents a separate AD forest with a single AD domain. When cross-forest trust between an AD forest root domain and an IdM domain is established, users from the AD forest domains can interact with Linux machines and services from the IdM domain.

Note

In trust environments, IdM enables you to use ID views to configure POSIX attributes for AD users on the IdM server.

Chapter 4. AD administration rights

When you want to build a trust between AD (Active Directory) and IdM (Identity Management), you will need to use an AD administrator account with appropriate AD privileges.

Such an AD administrator must be a member of one of the following groups:

  • Enterprise Admin group in the AD forest
  • Domain Admins group in the forest root domain for your AD forest

Additional resources

Chapter 5. Ensuring support for common encryption types in AD and RHEL

By default, Identity Management establishes a cross-realm trust with support for RC4, AES-128, and AES-256 Kerberos encryption types.

RC4 encryption has been deprecated and disabled by default, as it is considered less secure than the newer AES-128 and AES-256 encryption types. In contrast, Active Directory (AD) user credentials and trusts between AD domains support RC4 encryption and they might not support AES encryption types.

Without any common encryption types, communication between IdM and AD child domains might not work, or some AD accounts might not be able to authenticate. To remedy this situation, modify one of the following configurations:

Enable AES encryption support in Active Directory (recommended option)
To ensure trusts between AD domains in an AD forest support strong AES encryption types, see the following Microsoft article: AD DS: Security: Kerberos "Unsupported etype" error when accessing a resource in a trusted domain
Enable RC4 support in RHEL

On every IdM trust controller, trust agent, and client where authentication against AD Domain Controllers takes place:

  1. Use the update-crypto-policies command to enable the AD-SUPPORT cryptographic subpolicy in addition to the DEFAULT cryptographic policy.

    [root@host ~]# update-crypto-policies --set DEFAULT:AD-SUPPORT
    Setting system policy to DEFAULT:AD-SUPPORT
    Note: System-wide crypto policies are applied on application start-up.
    It is recommended to restart the system for the change of policies
    to fully take place.
  2. Restart the host.

Additional resources

Chapter 6. Ports required for communication between IdM and AD

To enable communication between your Active Directory (AD) and Identity Management (IdM) environments, open the following ports on the firewalls of your AD Domain Controllers and IdM servers.

Table 6.1. Ports required for an AD trust

ServicePortProtocol

Endpoint resolution portmapper

135

TCP

NetBIOS-DGM

138

TCP and UDP

NetBIOS-SSN

139

TCP and UDP

Microsoft-DS

445

TCP and UDP

Dynamic RPC

49152-65535

TCP

AD Global Catalog

3268

TCP

LDAP

389

TCP and UDP

Note

The TCP port 389 is not required to be open on IdM servers for trust, but it is necessary for clients communicating with the IdM server.

To open ports, you can use the following methods:

  • Firewalld service — you can enable the particular ports or enable the following services which includes the ports:

    • FreeIPA trust setup
    • FreeIPA with LDAP
    • Kerberos
    • DNS

    For details, see Controlling ports using CLI.

Note

If you are using RHEL 8.2 and earlier, the freeipa-trust Firewalld service includes an RPC port range of 1024-1300, which is incorrect. On RHEL 8.2 and earlier, you must manually open the TCP port range 49152-65535 in addition to enabling the freeipa-trust Firewalld service.

This issue has been fixed for RHEL 8.3 and later in Bug 1850418 - update freeipa-trust.xml definition to include correct dynamic RPC range.

Table 6.2. Ports required by IdM servers in a trust

ServicePortProtocol

Kerberos

88, 464

TCP and UDP

LDAP

389

TCP

DNS

53

TCP and UDP

Table 6.3. Ports required by IdM clients in an AD trust

ServicePortProtocol

Kerberos

88

UDP and TCP

Note

The libkrb5 library uses UDP and falls back to the TCP protocol if the data sent from the Key Distribution Centre (KDC) is too large. Active Directory attaches a Privilege Attribute Certificate (PAC) to the Kerberos ticket, which increases the size and requires to use the TCP protocol. To avoid the fall-back and resending the request, by default, SSSD in Red Hat Enterprise Linux 7.4 and later uses TCP for user authentication. If you want to configure the size before libkrb5 uses TCP, set the udp_preference_limit in the /etc/krb.5.conf file. For details, see the krb5.conf(5) man page.

The following diagram shows the ports and protocols that IdM clients, IdM servers, and AD Domain Controllers use when communicating with each other.

diagram showing the ports and protocols that IdM clients use when communicating with IdM servers and AD Domain Controllers

Additional resources

Chapter 7. Configuring DNS and realm settings for a trust

Before you connect Identity Management (IdM) and Active Directory (AD) in a trust, you need to ensure that servers see each other and resolve domain names correctly. This scenario describes configuring DNS to allow using domain names between:

  • One primary IdM server using integrated DNS server and Certification Authority.
  • One AD Domain Controller.

DNS settings require:

  • Configuring DNS zones in the IdM server
  • Configuring conditional DNS forwarding in AD
  • Verifying correctness of the DNS configuration

7.1. 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.
Note

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:

$ ipa dns-update-system-records --dry-run

The generated list can look for example like this:

IPA DNS records:
  _kerberos-master._tcp.idm.example.com. 86400 IN SRV 0 100 88 server.idm.example.com.
  _kerberos-master._udp.idm.example.com. 86400 IN SRV 0 100 88 server.idm.example.com.
  _kerberos._tcp.idm.example.com. 86400 IN SRV 0 100 88 server.idm.example.com.
  _kerberos._tcp.idm.example.com. 86400 IN SRV 0 100 88 server.idm.example.com.
  _kerberos.idm.example.com. 86400 IN TXT "IDM.EXAMPLE.COM"
  _kpasswd._tcp.idm.example.com. 86400 IN SRV 0 100 464 server.idm.example.com.
  _kpasswd._udp.idm.example.com. 86400 IN SRV 0 100 464 server.idm.example.com.
  _ldap._tcp.idm.example.com. 86400 IN SRV 0 100 389 server.idm.example.com.
  _ipa-ca.idm.example.com. 86400 IN A 192.168.122.2

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.

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

This section describes how to add a new DNS forward zone to the Identity Management (IdM) server 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.

    Screenshot of the IdM Web UI displaying the contents of the DNS drop-down sub-menu of the "Network Services" tab. The DNS drop-down menu has four options: DNS Zones - DNS Forward Zones - DNS Servers - DNS Global Configuration. "DNS Forward Zones" is highlighted.

  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 new forward zone.
  9. Click on the Add button.

    Screenshot of the "Add DNS forward zone" pop-up window with text entry fields for "Zone name" - "Reverse zone IP network" - "Zone forwarders." The "Forward policy" option has three radial buttons for "forward first" - "forward only" - "forward disabled." There is a checkbox for "Skip overlap check" and there are four buttons at the bottom: "Add" - "Add and Add Another" - "Add and Edit" - "Cancel."

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.

Note

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

Screenshot displaying a popup window that reads "DNSSEC validation failed - record ad.example.com SOA failed DNSSEC validation on server 192.168.122.2. Please verify your DNSSEC configuration or disable DNSSEC validation on all IPA servers."

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.

7.3. 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
Note

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:

named-pkcs11[2572]: no valid DS resolving 'host.ad.example.com/A/IN':  192.168.100.25#53

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.

7.4. 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.

7.5. 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.

    [admin@server ~]# dig +short -t SRV _kerberos._udp.idm.example.com.
    0 100 88 server.idm.example.com.
    
    [admin@server ~]# 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.

    [admin@server ~]# 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:

      [admin@server ~]$ 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:

        [admin@server ~]$ 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:

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

Chapter 8. Configuring IdM clients in an Active Directory DNS domain

If you have client systems in a DNS domain controlled by Active Directory and you require those clients to be able to join the IdM Server to benefit from its RHEL features, you can configure users to access a client using a host name from the Active Directory DNS domain.

Important

This is not a recommended configuration and has some limitations. Red Hat recommends to always deploy IdM clients in a DNS zone different from the ones owned by Active Directory and access IdM clients through their IdM host names.

Your IdM client configuration depends on whether you require single sign-on with Kerberos.

8.1. 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:

    [root@idm-client.ad.example.com ~]# 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.

8.2. 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

Procedure

  • Use certmonger to request a certificate using the FQDN:

    [root@idm-client.ad.example.com ~]# 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/idm-client.ad.example.com@IDM.EXAMPLE.COM \
          -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).

8.3. 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

8.4. 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

Procedure

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

    [root@idm-server.idm.example.com ~]# 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:

    [root@idm-server.idm.example.com ~]# 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:

    [root@idm-client.idm.example.com ~]# 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/idm-client.idm.example.com@IDM.EXAMPLE.COM \
          -U id-kp-serverAuth

Chapter 9. Setting up a trust

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

Prerequisites

9.1. 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.

Note

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:

    [root@ipaserver ~]# dnf install ipa-server-trust-ad samba-client
  2. Authenticate as the IdM administrative user:

    [root@ipaserver ~]# kinit admin
  3. Run the ipa-adtrust-install utility:

    [root@ipaserver ~]# 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.

    [root@ipaserver ~]# net conf setparm global 'rpc server dynamic port range' 55000-65000
    [root@ipaserver ~]# firewall-cmd --add-port=55000-65000/tcp
    [root@ipaserver ~]# firewall-cmd --runtime-to-permanent
  9. Make sure that DNS is properly configured, as described in Verifying the DNS configuration for a trust.

    Important

    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:

    [root@ipaserver ~]# ipactl restart
  11. Use the smbclient utility to verify that Samba responds to Kerberos authentication from the IdM side:

    [root@ipaserver ~]# 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)
    ...

9.2. 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.

Prerequisites

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 the Active Directory domain ID range type. This is the most common configuration.

      [root@server ~]# 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:

      [root@server ~]# ipa trust-add --type=ad ad.example.com --admin <ad_admin_username> --password --range-type=ipa-ad-trust-posix
Warning

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.

9.3. 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.

    ipa trust trusts

  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.

    ipa trust add

  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.

      The Range Type section of the IdM WebUI displays 3 radio buttons to choose the appropriate range type - Detect

      Warning

      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.

      idm trust added

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

9.4. 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:

    [root@ipaserver ~]# kinit user@AD.EXAMPLE.COM
  2. Request service tickets for a service within the IdM domain:

    [root@server ~]# 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/IPA.DOMAIN@AD.DOMAIN.

[root@server ]# klist
Ticket cache: KEYRING:persistent:0:krb_ccache_hRtox00
Default principal: user@AD.EXAMPLE.COM

Valid starting       Expires              Service principal
03.05.2016 18:31:06  04.05.2016 04:31:01  host/server.idm.example.com@IDM.EXAMPLE.COM
	renew until 04.05.2016 18:31:00
03.05.2016 18:31:06 04.05.2016 04:31:01 krbtgt/IDM.EXAMPLE.COM@AD.EXAMPLE.COM
	renew until 04.05.2016 18:31:00
03.05.2016 18:31:01  04.05.2016 04:31:01  krbtgt/AD.EXAMPLE.COM@AD.EXAMPLE.COM
	renew until 04.05.2016 18:31:00

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.

9.5. 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.

    [root@server ~]# dig +short -t SRV _kerberos._udp.dc._msdcs.idm.example.com.
    0 100 88 server.idm.example.com.
    
    [root@server ~]# 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:

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

.

9.6. 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

9.7. 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:

    [root@existing_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.

    [root@new_trust_agent]# ipactl restart
  3. Remove all entries from the SSSD cache on the trust agent:

    [root@new_trust_agent]# sssctl cache-remove
  4. Verify that the replica has the AD trust agent role installed:.

    [root@existing_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.

9.8. 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.

    [root@server ~]# 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.

    [root@server ~]# ipa idrange-mod --auto-private-groups=hybrid AD.EXAMPLE.COM_id_range
  3. Reset the SSSD cache to enable the new setting.

    [root@server ~]# sss_cache -E

9.9. 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 ServerID 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.

    Screenshot of the ID Ranges tab of the IPA Server section of the IdM WebUI. A user selects the hybrid option from the Auth private groups dropdown menu.

  5. Click the Save button to save your changes.

Chapter 10. Troubleshooting setting up a cross-forest trust

This chapter discusses troubleshooting the process of configuring a cross-forest trust between your Identity Management (IdM) environment and an Active Directory (AD) forest.

10.1. 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.

      Note

      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.

        Note

        By default, RHEL 9 does not allow SHA-1 encryption, which is an algorithm that AD requires. Make sure you have enabled the AD-SUPPORT system-wide cryptographic subpolicy to allow SHA-1 encryption in your RHEL 9 IdM servers for communication with AD Domain Controllers. See <link TBA>.

  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.

    Note

    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.

10.2. Checklist of prerequisites for establishing an AD trust

You can use the following checklist to review the prerequisites for creating a trust with an AD domain.

Table 10.1. Table

ComponentConfigurationAdditional details

Product versions

Your Active Directory domain is using a supported version of Windows Server.

Supported versions of Windows Server

AD Administrator privileges

The Active Directory administration account must be a member of one of the following groups:

  • Enterprise Admin (EA) group in the AD forest
  • Domain Admins (DA) group in the forest root domain for your AD forest
 

Networking

IPv6 support is enabled in the Linux kernel for all IdM servers.

IPv6 requirements in IdM

Date and time

Make sure date and time settings on both servers match.

Time service requirements for IdM

Encryption types

The following AD accounts have AES encryption keys:

  • AD Administrator
  • AD user accounts
  • AD services

If you have recently enabled AES encryption in AD, generate new AES keys with the following steps:

  1. Re-establish trust relationships between any AD domains in your forest.
  2. Change the passwords for the AD Administrator, user accounts, and services.

Firewall

You have opened all necessary ports on IdM servers and AD Domain Controllers for bidirectional communication.

Ports required for communication between IdM and AD

DNS

  • IdM and AD each have unique primary DNS domains.
  • IdM and AD DNS domains do not overlap.
  • Proper DNS service (SRV) records for LDAP and Kerberos services.
  • You can resolve DNS records from all DNS domains in the trust.
  • Kerberos realm names are the upper-case versions of primary DNS domain names. For example, DNS domain example.com has a corresponding Kerberos realm EXAMPLE.COM

Configuring DNS and realm settings for a trust

Topology

Ensure you are attempting to establish a trust with an IdM server you have configured as a trust controller.

Trust controllers and trust agents

10.3. Gathering debug logs of an attempt to establish an AD trust

If you are experiencing issues with establishing a trust between an IdM environment and AD domain, use the following steps to enable detailed error logging so you can gather logs of an attempt to establish a trust. You can review these logs to help with your troubleshooting efforts, or you can provide them in a Red Hat Technical Support case.

Prerequisites

  • You need root permissions to restart IdM services.

Procedure

  1. To enable debugging for the IdM server, create the file /etc/ipa/server.conf with the following contents.

    [global]
    debug=True
  2. Restart the httpd service to load the debugging configuration.

    [root@trust_controller ~]# systemctl restart httpd
  3. Stop the smb and winbind services.

    [root@trust_controller ~]# systemctl stop smb winbind
  4. Set the debugging log level for the smb and winbind services.

    [root@trust_controller ~]# net conf setparm global 'log level' 100
  5. To enable debug logging for Samba client code used by the IdM framework, edit the /usr/share/ipa/smb.conf.empty configuration file to have the following contents.

        [global]
        log level = 100
  6. Remove previous Samba logs.

    [root@trust_controller ~]# rm /var/log/samba/log.*
  7. Start the smb and winbind services.

    [root@trust_controller ~]# systemctl start smb winbind
  8. Print a timestamp as you attempt to establish a trust with verbose mode enabled.

    [root@trust_controller ~]# date; ipa -vvv trust-add --type=ad ad.example.com
  9. Review the following error log files for information about the failed request:

    1. /var/log/httpd/error_log
    2. /var/log/samba/log.*
  10. Disable debugging.

    [root@trust_controller ~]# mv /etc/ipa/server.conf /etc/ipa/server.conf.backup
    [root@trust_controller ~]# systemctl restart httpd
    [root@trust_controller ~]# systemctl stop smb winbind
    [root@trust_controller ~]# net conf setparm global 'log level' 0
    [root@trust_controller ~]# mv /usr/share/ipa/smb.conf.empty /usr/share/ipa/smb.conf.empty.backup
    [root@trust_controller ~]# systemctl start smb winbind
  11. (Optional) If you are unable to determine the cause of the authentication issue:

    1. Collect and archive the log files you recently generated.

      [root@trust_controller ~]# tar -xcvf debugging-trust.tar /var/log/httpd/error_log /var/log/samba/log.*
    2. Open a Red Hat Technical Support case and provide the timestamp and debug logs from the attempt.

Additional resources

Chapter 11. Troubleshooting client access to services in the other forest

After configuring a trust between your Identity Management (IdM) and Active Directory (AD) environments, you might experience issues where a client in one domain is not able to access a service in the other domain. Use the following diagrams to troubleshoot the issue.

11.1. 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.

diagram showing how an AD client communicates with an AD Domain Controller and an IdM server

  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.

11.2. 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.

diagram showing how an AD client in a chile domain communicates with multiple layers of AD Domain Controllers and an IdM server

  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.

11.3. Flow of information when an IdM client requests services from an AD server

The following diagram explains the flow of information when an Identity Management (IdM) client requests a service in the Active Directory (AD) domain when you have configured a two-way trust between IdM and AD.

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

Note

By default, IdM establishes a one-way trust to AD, which means it is not possible to issue cross-realm ticket-granting ticket (TGT) for resources in an AD forest. To be able to request tickets to services from trusted AD domains, configure a two-way trust.

diagram showing how an IdM client communicates with an IdM server and an AD Domain Controller

  1. The IdM client requests a ticket-granting ticket (TGT) from the IdM Kerberos Distribution Center (KDC) for the AD service it wants to contact.
  2. The IdM KDC recognizes that the service belongs to the AD realm, verifies that the realm is known and trusted, and that the client is allowed to request services from that realm.
  3. Using information from the IdM Directory Server about the user principal, the IdM KDC creates a cross-realm TGT with a Privileged Attribute Certificate (MS-PAC) record about the user principal.
  4. The IdM KDC sends back a cross-realm TGT to the IdM client.
  5. The IdM client contacts the AD KDC to request a ticket for the AD service, presenting the cross-realm TGT that contains the MS-PAC provided by the IdM KDC.
  6. The AD server validates and filters the PAC, and returns a ticket for the AD service.
  7. The IPA client can now contact the AD service.

Additional resources

Chapter 12. Removing the trust using the command line

This section describes how to remove the Identity Management (IdM)/Active Directory (AD) trust on the IdM side using the command line interface.

Prerequisites

Procedure

  1. Use the ipa trust-del command to remove the trust configuration from IdM.

    [root@server ~]# ipa trust-del ad_domain_name
    ------------------------------
    Deleted trust "ad_domain_name"
    ------------------------------
  2. Remove the trust object from your Active Directory configuration.

Verification steps

  • Use the ipa trust-show command to confirm that the trust has been removed.

    [root@server ~]# ipa trust-show ad.example.com
    ipa: ERROR: ad.example.com: trust not found

Chapter 13. Removing the trust using the IdM Web UI

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

Prerequisites

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. Select the trust you want to remove.

    A screenshot of the IdM Web UI displaying the "Trusts" page which is a subpage of the "IPA Server" tab. This page has a table listing "Realm names" and checkbox next to the first entry of "AD.EXAMPLE.COM" is checked.

  5. Click the Delete button.
  6. In the Remove trusts dialog box, click Delete.

    A screenshot of a pop-up window titled "Remove trusts." The content of the warning is "Are you sure you want to delete selected entries?" and lists "AD.EXAMPLE.COM" below. There are "Delete" and "Cancel" buttons at the bottom right.

  7. Remove the trust object from your Active Directory configuration.

Verification steps

  • If the trust has been successfully deleted, the Web UI displays a green pop-up with the text:

    A screenshot of the IdM Web UI displaying the "Trusts" page with a pop-up window at the top that says "1 item(s) deleted." The table on the "Trusts" page does not have any entries.

Legal Notice

Copyright © 2022 Red Hat, Inc.
The text of and illustrations in this document are licensed by Red Hat under a Creative Commons Attribution–Share Alike 3.0 Unported license ("CC-BY-SA"). An explanation of CC-BY-SA is available at http://creativecommons.org/licenses/by-sa/3.0/. In accordance with CC-BY-SA, if you distribute this document or an adaptation of it, you must provide the URL for the original version.
Red Hat, as the licensor of this document, waives the right to enforce, and agrees not to assert, Section 4d of CC-BY-SA to the fullest extent permitted by applicable law.
Red Hat, Red Hat Enterprise Linux, the Shadowman logo, the Red Hat logo, JBoss, OpenShift, Fedora, the Infinity logo, and RHCE are trademarks of Red Hat, Inc., registered in the United States and other countries.
Linux® is the registered trademark of Linus Torvalds in the United States and other countries.
Java® is a registered trademark of Oracle and/or its affiliates.
XFS® is a trademark of Silicon Graphics International Corp. or its subsidiaries in the United States and/or other countries.
MySQL® is a registered trademark of MySQL AB in the United States, the European Union and other countries.
Node.js® is an official trademark of Joyent. Red Hat is not formally related to or endorsed by the official Joyent Node.js open source or commercial project.
The OpenStack® Word Mark and OpenStack logo are either registered trademarks/service marks or trademarks/service marks of the OpenStack Foundation, in the United States and other countries and are used with the OpenStack Foundation's permission. We are not affiliated with, endorsed or sponsored by the OpenStack Foundation, or the OpenStack community.
All other trademarks are the property of their respective owners.