Chapter 123. Using constrained delegation in IdM
Chapter 123. Using constrained delegation in IdM Learn more about how you can use the constrained delegation feature in Identity Management (IdM): Constrained delegation in Identity Management describes how constrained delegation works. Configuring a web console to allow a user authenticated with a smart card to SSH to a remote host without being asked to authenticate again describes a use case for constrained delegation in the context of using the Red Hat Enterprise Linux web console to SSH to a remote host without requiring authentication. Using Ansible to configure a web console to allow a user authenticated with a smart card to SSH to a remote host without being asked to authenticate again describes a use case for constrained delegation in the context of using Ansible to configure the use of the Red Hat Enterprise Linux web console to SSH to a remote host without requiring authentication. Configuring a web console client to allow a user authenticated with a smart card to run sudo without being asked to authenticate describes a use case for constrained delegation in the context of using the Red Hat Enterprise Linux web console to run sudo without requiring authentication. Using Ansible to configure a web console to allow a user authenticated with a smart card to run sudo without being asked to authenticate again describes a use case for constrained delegation in the context of using Ansible to configure the use of the Red Hat Enterprise Linux web console to run sudo without requiring authentication. 123.1. Constrained delegation in Identity Management The Service for User to Proxy ( S4U2proxy ) extension provides a service that obtains a service ticket to another service on behalf of a user. This feature is known as constrained delegation . The second service is typically a proxy performing some work on behalf of the first service, under the authorization context of the user. Using constrained delegation eliminates the need for the user to delegate their full ticket-granting ticket (TGT). Identity Management (IdM) traditionally uses the Kerberos S4U2proxy feature to allow the web server framework to obtain an LDAP service ticket on the user's behalf. The IdM-AD trust system also uses constrained delegation to obtain a cifs principal. You can use the S4U2proxy feature to configure a web console client to allow an IdM user that has authenticated with a smart card to achieve the following: Run commands with superuser privileges on the RHEL host on which the web console service is running without being asked to authenticate again. Access a remote host using SSH and access services on the host without being asked to authenticate again. Additional resources Using Ansible to configure a web console to allow a user authenticated with a smart card to SSH to a remote host without being asked to authenticate again Using Ansible to configure a web console to allow a user authenticated with a smart card to run sudo without being asked to authenticate again S4U2proxy Service constrained delegation 123.2. Configuring a web console to allow a user authenticated with a smart card to SSH to a remote host without being asked to authenticate again After you have logged in to a user account on the RHEL web console, as an Identity Management (IdM) system administrator you might need to connect to remote machines by using the SSH protocol. You can use the constrained delegation feature to use SSH without being asked to authenticate again. Follow this procedure to configure the web console to use constrained delegation. In the example below, the web console session runs on the myhost.idm.example.com host and it is being configured to access the remote.idm.example.com host by using SSH on behalf of the authenticated user. Prerequisites You have obtained an IdM admin ticket-granting ticket (TGT). You have root access to remote.idm.example.com . The web console service is present in IdM. The remote.idm.example.com host is present in IdM. The web console has created an S4U2Proxy Kerberos ticket in the user session. To verify that this is the case, log in to the web console as an IdM user, open the Terminal page, and enter: Procedure Create a list of the target hosts that can be accessed by the delegation rule: Create a service delegation target: Add the target host to the delegation target: Allow cockpit sessions to access the target host list by creating a service delegation rule and adding the HTTP service Kerberos principal to it: Create a service delegation rule: Add the web console client to the delegation rule: Add the delegation target to the delegation rule: Enable Kerberos authentication on the remote.idm.example.com host: SSH to remote.idm.example.com as root . Open the /etc/ssh/sshd_config file for editing. Enable GSSAPIAuthentication by uncommenting the GSSAPIAuthentication no line and replacing it with GSSAPIAuthentication yes . Restart the SSH service on remote.idm.example.com so that the above changes take effect immediately: Additional resources Logging in to the web console with smart cards Constrained delegation in Identity Management 123.3. Using Ansible to configure a web console to allow a user authenticated with a smart card to SSH to a remote host without being asked to authenticate again After you have logged in to a user account on the RHEL web console, as an Identity Management (IdM) system administrator you might need to connect to remote machines by using the SSH protocol. You can use the constrained delegation feature to use SSH without being asked to authenticate again. Follow this procedure to use the servicedelegationrule and servicedelegationtarget ansible-freeipa modules to configure a web console to use constrained delegation. In the example below, the web console session runs on the myhost.idm.example.com host and it is being configured to access the remote.idm.example.com host by using SSH on behalf of the authenticated user. Prerequisites The IdM admin password. root access to remote.idm.example.com . The web console service is present in IdM. The remote.idm.example.com host is present in IdM. The web console has created an S4U2Proxy Kerberos ticket in the user session. To verify that this is the case, log in to the web console as an IdM user, open the Terminal page, and enter: You have configured your Ansible control node to meet the following requirements: You are using Ansible version 2.13 or later. You have installed the ansible-freeipa package. The example assumes that in the ~/ MyPlaybooks / directory, you have created an Ansible inventory file with the fully-qualified domain name (FQDN) of the IdM server. The example assumes that the secret.yml Ansible vault stores your ipaadmin_password . The target node, that is the node on which the ansible-freeipa module is executed, is part of the IdM domain as an IdM client, server or replica. Procedure Navigate to your ~/ MyPlaybooks / directory: Create a web-console-smart-card-ssh.yml playbook with the following content: Create a task that ensures the presence of a delegation target: Add a task that adds the target host to the delegation target: Add a task that ensures the presence of a delegation rule: Add a task that ensures that the Kerberos principal of the web console client service is a member of the constrained delegation rule: Add a task that ensures that the constrained delegation rule is associated with the web-console-delegation-target delegation target: Save the file. Run the Ansible playbook. Specify the playbook file, the file storing the password protecting the secret.yml file, and the inventory file: Enable Kerberos authentication on remote.idm.example.com : SSH to remote.idm.example.com as root . Open the /etc/ssh/sshd_config file for editing. Enable GSSAPIAuthentication by uncommenting the GSSAPIAuthentication no line and replacing it with GSSAPIAuthentication yes . Additional resources Logging in to the web console with smart cards Constrained delegation in Identity Management README-servicedelegationrule.md and README-servicedelegationtarget.md in the /usr/share/doc/ansible-freeipa/ directory Sample playbooks in the /usr/share/doc/ansible-freeipa/playbooks/servicedelegationtarget and /usr/share/doc/ansible-freeipa/playbooks/servicedelegationrule directories 123.4. Configuring a web console to allow a user authenticated with a smart card to run sudo without being asked to authenticate again After you have logged in to a user account on the RHEL web console, as an Identity Management (IdM) system administrator you might need to run commands with superuser privileges. You can use the constrained delegation feature to run sudo on the system without being asked to authenticate again. Follow this procedure to configure a web console to use constrained delegation. In the example below, the web console session runs on the myhost.idm.example.com host. Prerequisites You have obtained an IdM admin ticket-granting ticket (TGT). The web console service is present in IdM. The myhost.idm.example.com host is present in IdM. You have enabled admin sudo access to domain administrators on the IdM server . The web console has created an S4U2Proxy Kerberos ticket in the user session. To verify that this is the case, log in to the web console as an IdM user, open the Terminal page, and enter: Procedure Create a list of the target hosts that can be accessed by the delegation rule: Create a service delegation target: Add the target host to the delegation target: Allow cockpit sessions to access the target host list by creating a service delegation rule and adding the HTTP service Kerberos principal to it: Create a service delegation rule: Add the web console service to the delegation rule: Add the delegation target to the delegation rule: Enable pam_sss_gss , the PAM module for authenticating users over the Generic Security Service Application Program Interface (GSSAPI) in cooperation with the System Security Services Daemon (SSSD): Open the /etc/sssd/sssd.conf file for editing. Specify that pam_sss_gss can provide authentication for the sudo and sudo -i commands in IdM your domain: Save and exit the file. Open the /etc/pam.d/sudo file for editing. Insert the following line to the top of the #%PAM-1.0 list to allow, but not require, GSSAPI authentication for sudo commands: Save and exit the file. Restart the SSSD service so that the above changes take effect immediately: Additional resources Logging in to the web console with smart cards Constrained delegation in Identity Management 123.5. Using Ansible to configure a web console to allow a user authenticated with a smart card to run sudo without being asked to authenticate again After you have logged in to a user account on the RHEL web console, as an Identity Management (IdM) system administrator you might need to run commands with superuser privileges. You can use the constrained delegation feature to run sudo on the system without being asked to authenticate again. Follow this procedure to use the ipaservicedelegationrule and ipaservicedelegationtarget ansible-freeipa modules to configure a web console to use constrained delegation. In the example below, the web console session runs on the myhost.idm.example.com host. Prerequisites You have obtained an IdM admin ticket-granting ticket (TGT) by authenticating to the web console session with a smart card.. The web console service has been enrolled into IdM. The myhost.idm.example.com host is present in IdM. You have enabled admin sudo access to domain administrators on the IdM server . The web console has created an S4U2Proxy Kerberos ticket in the user session. To verify that this is the case, log in to the web console as an IdM user, open the Terminal page, and enter: You have configured your Ansible control node to meet the following requirements: You are using Ansible version 2.13 or later. You have installed the ansible-freeipa package. The example assumes that 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 constrained delegation. The example assumes that the secret.yml Ansible vault stores your ipaadmin_password . The target node, that is the node on which the ansible-freeipa module is executed, is part of the IdM domain as an IdM client, server or replica. Procedure On your Ansible control node, navigate to your ~/ MyPlaybooks / directory: Create a web-console-smart-card-sudo.yml playbook with the following content: Create a task that ensures the presence of a delegation target: Add a task that adds the target host to the delegation target: Add a task that ensures the presence of a delegation rule: Add a task that ensures that the Kerberos principal of the web console service is a member of the constrained delegation rule: Add a task that ensures that the constrained delegation rule is associated with the sudo-web-console-delegation-target delegation target: Save the file. Run the Ansible playbook. Specify the playbook file, the file storing the password protecting the secret.yml file, and the inventory file: Enable pam_sss_gss , the PAM module for authenticating users over the Generic Security Service Application Program Interface (GSSAPI) in cooperation with the System Security Services Daemon (SSSD): Open the /etc/sssd/sssd.conf file for editing. Specify that pam_sss_gss can provide authentication for the sudo and sudo -i commands in IdM your domain: Save and exit the file. Open the /etc/pam.d/sudo file for editing. Insert the following line to the top of the #%PAM-1.0 list to allow, but not require, GSSAPI authentication for sudo commands: Save and exit the file. Restart the SSSD service so that the above changes take effect immediately: Additional resources Constrained delegation in Identity Management README-servicedelegationrule.md and README-servicedelegationtarget.md in the /usr/share/doc/ansible-freeipa/ directory Sample playbooks in the /usr/share/doc/ansible-freeipa/playbooks/servicedelegationtarget and /usr/share/doc/ansible-freeipa/playbooks/servicedelegationrule directories 123.6. Additional resources Managing remote systems in the web console
klist Ticket cache: FILE:/run/user/1894000001/cockpit-session-3692.ccache Default principal: user@IDM.EXAMPLE.COM Valid starting Expires Service principal 07/30/21 09:19:06 07/31/21 09:19:06 HTTP/myhost.idm.example.com@IDM.EXAMPLE.COM 07/30/21 09:19:06 07/31/21 09:19:06 krbtgt/IDM.EXAMPLE.COM@IDM.EXAMPLE.COM for client HTTP/myhost.idm.example.com@IDM.EXAMPLE.COM ipa servicedelegationtarget-add cockpit-target ipa servicedelegationtarget-add-member cockpit-target \ --principals=host/remote.idm.example.com@IDM.EXAMPLE.COM ipa servicedelegationrule-add cockpit-delegation ipa servicedelegationrule-add-member cockpit-delegation \ --principals=HTTP/myhost.idm.example.com@IDM.EXAMPLE.COM ipa servicedelegationrule-add-target cockpit-delegation \ --servicedelegationtargets=cockpit-target systemctl try-restart sshd.service klist Ticket cache: FILE:/run/user/1894000001/cockpit-session-3692.ccache Default principal: user@IDM.EXAMPLE.COM Valid starting Expires Service principal 07/30/21 09:19:06 07/31/21 09:19:06 HTTP/myhost.idm.example.com@IDM.EXAMPLE.COM 07/30/21 09:19:06 07/31/21 09:19:06 krbtgt/IDM.EXAMPLE.COM@IDM.EXAMPLE.COM for client HTTP/myhost.idm.example.com@IDM.EXAMPLE.COM cd ~/ MyPlaybooks / --- - name: Playbook to create a constrained delegation target hosts: ipaserver vars_files: - /home/user_name/MyPlaybooks/secret.yml tasks: - name: Ensure servicedelegationtarget web-console-delegation-target is present ipaservicedelegationtarget: ipaadmin_password: "{{ ipaadmin_password }}" name: web-console-delegation-target - name: Ensure servicedelegationtarget web-console-delegation-target member principal host/remote.idm.example.com@IDM.EXAMPLE.COM is present ipaservicedelegationtarget: ipaadmin_password: "{{ ipaadmin_password }}" name: web-console-delegation-target principal: host/remote.idm.example.com@IDM.EXAMPLE.COM action: member - name: Ensure servicedelegationrule delegation-rule is present ipaservicedelegationrule: ipaadmin_password: "{{ ipaadmin_password }}" name: web-console-delegation-rule - name: Ensure the Kerberos principal of the web console client service is added to the servicedelegationrule web-console-delegation-rule ipaservicedelegationrule: ipaadmin_password: "{{ ipaadmin_password }}" name: web-console-delegation-rule principal: HTTP/myhost.idm.example.com action: member - name: Ensure a constrained delegation rule is associated with a specific delegation target ipaservicedelegationrule: ipaadmin_password: "{{ ipaadmin_password }}" name: web-console-delegation-rule target: web-console-delegation-target action: member ansible-playbook --vault-password-file=password_file -v -i inventory web-console-smart-card-ssh.yml klist Ticket cache: FILE:/run/user/1894000001/cockpit-session-3692.ccache Default principal: user@IDM.EXAMPLE.COM Valid starting Expires Service principal 07/30/21 09:19:06 07/31/21 09:19:06 HTTP/myhost.idm.example.com@IDM.EXAMPLE.COM 07/30/21 09:19:06 07/31/21 09:19:06 krbtgt/IDM.EXAMPLE.COM@IDM.EXAMPLE.COM for client HTTP/myhost.idm.example.com@IDM.EXAMPLE.COM ipa servicedelegationtarget-add cockpit-target ipa servicedelegationtarget-add-member cockpit-target \ --principals=host/myhost.idm.example.com@IDM.EXAMPLE.COM ipa servicedelegationrule-add cockpit-delegation ipa servicedelegationrule-add-member cockpit-delegation \ --principals=HTTP/myhost.idm.example.com@IDM.EXAMPLE.COM ipa servicedelegationrule-add-target cockpit-delegation \ --servicedelegationtargets=cockpit-target [domain/idm.example.com] pam_gssapi_services = sudo, sudo-i auth sufficient pam_sss_gss.so systemctl restart sssd klist Ticket cache: FILE:/run/user/1894000001/cockpit-session-3692.ccache Default principal: user@IDM.EXAMPLE.COM Valid starting Expires Service principal 07/30/21 09:19:06 07/31/21 09:19:06 HTTP/myhost.idm.example.com@IDM.EXAMPLE.COM 07/30/21 09:19:06 07/31/21 09:19:06 krbtgt/IDM.EXAMPLE.COM@IDM.EXAMPLE.COM for client HTTP/myhost.idm.example.com@IDM.EXAMPLE.COM cd ~/ MyPlaybooks / --- - name: Playbook to create a constrained delegation target hosts: ipaserver vars_files: - /home/user_name/MyPlaybooks/secret.yml tasks: - name: Ensure servicedelegationtarget named sudo-web-console-delegation-target is present ipaservicedelegationtarget: ipaadmin_password: "{{ ipaadmin_password }}" name: sudo-web-console-delegation-target - name: Ensure that a member principal named host/myhost.idm.example.com@IDM.EXAMPLE.COM is present in a service delegation target named sudo-web-console-delegation-target ipaservicedelegationtarget: ipaadmin_password: "{{ ipaadmin_password }}" name: sudo-web-console-delegation-target principal: host/myhost.idm.example.com@IDM.EXAMPLE.COM action: member - name: Ensure servicedelegationrule named sudo-web-console-delegation-rule is present ipaservicedelegationrule: ipaadmin_password: "{{ ipaadmin_password }}" name: sudo-web-console-delegation-rule - name: Ensure the Kerberos principal of the web console service is added to the service delegation rule named sudo-web-console-delegation-rule ipaservicedelegationrule: ipaadmin_password: "{{ ipaadmin_password }}" name: sudo-web-console-delegation-rule principal: HTTP/myhost.idm.example.com action: member - name: Ensure a constrained delegation rule is associated with a specific delegation target ipaservicedelegationrule: ipaadmin_password: "{{ ipaadmin_password }}" name: sudo-web-console-delegation-rule target: sudo-web-console-delegation-target action: member ansible-playbook --vault-password-file=password_file -v -i inventory web-console-smart-card-sudo.yml [domain/idm.example.com] pam_gssapi_services = sudo, sudo-i auth sufficient pam_sss_gss.so systemctl restart sssd