Chapter 5. Configuring smart card authentication with the web console for centrally managed users


You can configure smart card authentication in the RHEL web console for users who are centrally managed by:

  • Identity Management
  • Active Directory which is connected in the cross-forest trust with Identity Management

Prerequisites

5.1. Smart-card authentication for centrally managed users

A smart card is a physical device, which can provide personal authentication using certificates stored on the card. Personal authentication means that you can use smart cards in the same way as user passwords.

You can store user credentials on the smart card in the form of a private key and a certificate. Special software and hardware is used to access them. You insert the smart card into a reader or a USB socket and supply the PIN code for the smart card instead of providing your password.

Identity Management (IdM) supports smart-card authentication with:

Note

If you want to start using smart card authentication, see the hardware requirements: Smart Card support in RHEL8+.

5.2. Enabling smart-card authentication for the web console

To use smart-card authentication in the web console, enable this authentication method in the cockpit.conf file.

Additionally, you can disable password authentication in the same file.

Prerequisites

Procedure

  1. Log in to the RHEL 10 web console.
  1. Click Terminal.
  2. In the /etc/cockpit/cockpit.conf, set the ClientCertAuthentication to yes:

    [WebService]
    ClientCertAuthentication = yes
    Copy to Clipboard
  3. Optional: Disable password-based authentication in cockpit.conf with:

    [Basic]
    action = none
    Copy to Clipboard

    This configuration disables password authentication and you must always use the smart card.

  4. Restart the web console to ensure that the cockpit.service accepts the change:

    # systemctl restart cockpit
    Copy to Clipboard

5.3. Logging in to the web console with smart cards

You can use smart cards to log in to the web console.

Prerequisites

  • A valid certificate stored in your smart card that is associated to a user account created in a Active Directory or Identity Management domain.
  • PIN to unlock the smart card.
  • The smart card has been put into the reader.

Procedure

  1. Log in to the RHEL 10 web console.

+ The browser asks you to add the PIN protecting the certificate stored on the smart card.

  1. In the Password Required dialog box, enter PIN and click OK.
  2. In the User Identification Request dialog box, select the certificate stored in the smart card.
  3. Select Remember this decision.

    The system does not open this window next time.

    Note

    This step does not apply to Google Chrome users.

  4. Click OK.

You are now connected and the web console displays its content.

5.4. Enabling passwordless sudo authentication for smart-card users

You can configure passwordless authentication to sudo and other services for smart card users in the web console.

As an alternative, if you use RHEL Identity Management, you can declare the initial web console certificate authentication as trusted for authenticating to sudo, SSH, or other services. For that purpose, the web console automatically creates an S4U2Proxy Kerberos ticket in the user session.

Prerequisites

Procedure

  1. Set up constraint delegation rules to list which hosts the ticket can access.

    Example 5.1. Setting up constraint delegation rules

    The web console session runs host host.example.com and should be trusted to access its own host with sudo. Additionally, we are adding second trusted host - remote.example.com.

    • Create the following delegation:

      • Run the following commands to add a list of target machines a particular rule can access:

        # ipa servicedelegationtarget-add cockpit-target
        # ipa servicedelegationtarget-add-member cockpit-target \ --principals=host/host.example.com@EXAMPLE.COM \ --principals=host/remote.example.com@EXAMPLE.COM
        Copy to Clipboard
      • To allow the web console sessions (HTTP/principal) to access that host list, use the following commands:

        # ipa servicedelegationrule-add cockpit-delegation
        # ipa servicedelegationrule-add-member cockpit-delegation \ --principals=HTTP/host.example.com@EXAMPLE.COM
        # ipa servicedelegationrule-add-target cockpit-delegation \ --servicedelegationtargets=cockpit-target
        Copy to Clipboard
  2. Enable GSS authentication in the corresponding services:

    1. For sudo, enable the pam_sss_gss module in the /etc/sssd/sssd.conf file:

      1. As root, add an entry for your domain to the /etc/sssd/sssd.conf configuration file.

        [domain/example.com]
        pam_gssapi_services = sudo, sudo-i
        Copy to Clipboard
      2. Enable the module in the /etc/pam.d/sudo file on the first line.

        auth sufficient pam_sss_gss.so
        Copy to Clipboard
    2. For SSH, update the GSSAPIAuthentication option in the /etc/ssh/sshd_config file to yes.
Warning

The delegated S4U ticket is not forwarded to remote SSH hosts when connecting to them from the web console. Authenticating to sudo on a remote host with your ticket will not work.

Verification

  1. Log in to the web console using a smart card.
  2. Click the Limited access button.
  3. Authenticate using your smart card.

Alternatively:

  • Try to connect to a different host with SSH.

5.5. Limiting user sessions and memory to prevent a DoS attack

A certificate authentication is protected by separating and isolating instances of the cockpit-ws web server against attackers who wants to impersonate another user. However, this introduces a potential denial of service (DoS) attack: A remote attacker could create a large number of certificates and send a large number of HTTPS requests to cockpit-ws each using a different certificate.

To prevent such DoS attacks, the collective resources of these web server instances are limited. By default, limits for the number of connections and memory usage are set to 200 threads and 75 % (soft) or 90 % (hard) memory limit.

The example procedure demonstrates resource protection by limiting the number of connections and memory.

Procedure

  1. In the terminal, open the system-cockpithttps.slice configuration file:

    # systemctl edit system-cockpithttps.slice
    Copy to Clipboard
  2. Limit the TasksMax to 100 and CPUQuota to 30%:

    [Slice]
    # change existing value
    TasksMax=100
    # add new restriction
    CPUQuota=30%
    Copy to Clipboard
  3. To apply the changes, restart the system:

    # systemctl daemon-reload
    # systemctl stop cockpit
    Copy to Clipboard

Now, the new memory and user session lower the risk of DoS attacks on the cockpit-ws web server.

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