18.2.1. Procedure – Configuring out-of-band gateway authentication

Purpose: 

To configure gateway authentication, complete the following steps.

Warning
  • The admin user is a special PSM user and not a member of any user groups, nor can it belong to any group. Since usermapping policies are based on user groups, performing gateway authentication with the admin user is likely to result in usermapping errors.

  • When using SSL-encrypted RDP connections, or connections that use the Credential Security Service Provider (CredSSP) authentication method, some Microsoft RDP clients restart the connection during the authentication process. This would require the user to perform gateway authentication on the PSM web interface twice. To avoid this situation, PSM temporarily caches the successful gateway authentication results if the client terminates the connection at a certain step while establishing the connection. The cache is used to automatically authenticate the restarted connection without user interaction.

    In this case, the restarted connection coming from the same source IP and targeting the same destination IP:port pair will be authenticated from the cache. The cache is deleted after three minutes, or when a connection is authenticated from the cache.

    However, caching the authentication results has the following side-effect: if a different connection targets the same destination IP:port pair from seemingly the same source IP address within the brief period when PSM expects the original connection to be re-established, the new connection can access the target server without having to authenticate on the PSM gateway. Normally, this can occur only if the clients are behind a NAT.

  • If the clients are behind a device that performs network address translation (NAT), it will seem to PSM as if every connection was initiated from the same IP address. Therefore, in such cases using out-of-band gateway authentication is not recommended for security reasons, especially for RDP connections. If possible, use inband gateway authentication instead.

Steps: 

  1. Navigate to the Connections page of the traffic (for example to SSH Control > Connections), and select the connection policy to modify.

  2. Select the Gateway authentication option. This is the option to configure gateway authentication via the web interface of PSM.

    Figure 18.2. <Protocol name> Connections > Gateway Authentication — Configuring gateway authentication

    <Protocol name> Connections > Gateway Authentication — Configuring gateway authentication
  3. To accept the gateway authentication only from the host that initiated the connection, select Require same IP.

    Note

    This option has no effect if the clients are behind a device that performs network address translation (NAT). In such cases, use inband gateway authentication instead.

  4. By default, any user can perform gateway authentication for the connections. To allow only members of a specific group authenticate the connections of this connection policy, select Groups, click and enter the name of the group whose members can authenticate the connections. This group must exist on the AAA > Group Management page. For details on creating and managing usergroups, see Section 5.7, Managing user rights and usergroups. Repeat this step to add further groups if needed.

  5. For SSH, RDP, Telnet and Citrix ICA connections, you may want to set a usermapping policy in the Usermapping policy field. For details on usermapping policies, see Procedure 18.1, Configuring usermapping policies.

  6. Click . After that, users accessing these connections must perform gateway authentication as described in Procedure 18.2.2, Performing out-of-band gateway authentication on PSM.

  7. Optional step: To restrict the availability of selected channels of the connection based on the username used for gateway authentication, edit the channel policy used in the connection.

    1. Navigate to the channel policy used in the connection (for example, SSH Control > Channel Policies).

    2. Select Gateway Group, click and enter the name of the user group allowed to use this type of the channel. The user group must correspond to the username used for the gateway authentication. Repeat this step until all permitted groups are listed.

      You may list local user lists as defined in Procedure 7.8, Creating and editing user lists, or LDAP groups (for details on accessing LDAP servers from PSM, see Procedure 7.9, Authenticating users to an LDAP server). Note the following behavior of PSM:

      • If you list multiple groups, members of any of the groups can access the channel.

        Note

        When listing both a whitelist and blacklist in the Gateway Group section and a username appears on both lists, the user will be able to access the channel.

      • If a local user list and an LDAP group has the same name and the LDAP server is configured in the connection that uses this channel policy, both the members of the LDAP group and the members of the local user list can access the channel.

    3. Click .

  8. Optional step: If you want to provide a limited PSM web interface to your users that can be used only for gateway authentication and 4-eyes authorization, set up a dedicated user-only web login address. For details, see Procedure 4.3.1, Configuring user and administrator login addresses.

  9. Optional step: You can configure a message for users accessing PSM for out-of-band authentication. The message is displayed when they log in to PSM.

    1. Navigate to Basic Settings > Management > Web gateway authentication.

    2. Select Enable web gateway authentication banner.

      Figure 18.3. Basic Settings > Management > Web gateway authentication — Configuring a banner

      Basic Settings > Management > Web gateway authentication — Configuring a banner
    3. Enter the message in the Banner field. You can use the following text formatting options:

      == Title ==
      === Subtitle ===
      
      This is plain text.
      [http://address.to/ Link text]
      
      # First numbered list item.
      # Second numbered list item.
      
      * First bulleted list item.
      * Second bulleted list item.
    4. Click .

  10. Optional step: If your users have sessions to several remote server, or access a server several times a day, performing the gateway authentication for every session can be a nuisance. To permit your users to authenticate on the PSM web interface once, and open sessions without repeating the gateway authentication, select Enable auto-assign and click . Note that the user must leave the browser window (or tab) of PSM open.