Configuring CHAP Authentication

The tasks in this section explain how to implement authentication on a PPP link by using the Challenge-Handshake Authentication Protocol (CHAP). The tasks use the example that is shown in Figure 2-4 to illustrate a working CHAP scenario for dialing up a private network. Use the instructions as the basis for implementing CHAP authentication at your site.

Before you perform the next procedures, you must have done the following:

• Set up and tested the dial-up link between the dial-in server and dial-out machines that belong to trusted callers

• Obtained superuser permission for the local machine, either dial-in server or dial-out machine

Setting Up CHAP Authentication (Task Maps)

Table 5-4 Task Map for CHAP Authentication (Dial-in Server)

Table 5-5 Task Map for CHAP Authentication (Dial-out Machine)

Configuring CHAP Authentication on the Dial-in Server

The first task in setting up CHAP authentication is modifying the /etc/ppp/chap-secrets file. This file contains the CHAP security credentials, including the CHAP secret, that are used to authenticate callers on the link.

The next procedure implements CHAP authentication for a dial-in server in a private network. The PPP link is the only connection to the outside world. The only callers who can access the network have been granted permission by managers of the network, possibly including the system administrator.

How to Create a CHAP Credentials Database (Dial-in Server)

1. Assemble a list that contains the user names of all trusted callers.

   Trusted callers include all people who have been granted permission to call the private network.

2. Assign each user a CHAP secret.

   ---

   Note - Be sure to choose a good CHAP secret that is not easily guessed. No other restrictions are placed on the CHAP secret's contents.

   ---

   The method for assigning CHAP secrets depends on your site's security policy. Either you have the responsibility for creating the secrets, or the callers must create their own secrets. If you are not responsible for CHAP secret assignment, be sure to get the CHAP secrets that were created by, or for, each trusted caller.

3. Become an administrator on the dial-in server.

   For more information, see How to Use Your Assigned Administrative Rights in Oracle Solaris 11.1 Administration: Security Services.

4. Modify the /etc/ppp/chap-secrets file.

   This release includes an /etc/ppp/chap-secrets file that contains helpful comments but no options. You can add the following options for the server CallServe at the end of the existing /etc/ppp/chap-secrets file.

   account1  CallServe   key123   *
   account2  CallServe   key456   *

   key123 is the CHAP secret for trusted caller account1.

   key456 is the CHAP secret for trusted caller account2.

See Also

The following list provides references to related information.

• How to Create a CHAP Credentials Database (Dial-in Server)

• How to Add CHAP Support to the PPP Configuration Files (Dial-in Server)

• Configuring CHAP Authentication for Trusted Callers (Dial-out Machines)

Modifying the PPP Configuration Files for CHAP (Dial-in Server)

The task in this section explains how to update existing PPP configuration files to support CHAP authentication on the dial-in server.

How to Add CHAP Support to the PPP Configuration Files (Dial-in Server)

1. Log in to the dial-in server as superuser.
2. Modify the /etc/ppp/options file.

   Add the options that are shown in bold for CHAP support.

   # cat /etc/ppp/options
   lock
   nodefaultroute
   name CallServe
   auth

   name CallServe

   Defines CallServe as the CHAP name of the user on the local machine, in this instance the dial-in server

   auth

   Makes the local machine authenticate callers before establishing the link

3. Create the remaining PPP configuration files to support the trusted callers.

   See How to Configure Users of the Dial-in Server and How to Define Communications Over the Serial Line (Dial-in Server).

See Also

To configure CHAP authentication credentials for trusted callers, refer to How to Create a CHAP Credentials Database (Dial-in Server).

Configuring CHAP Authentication for Trusted Callers (Dial-out Machines)

This section contains tasks for setting up CHAP authentication on the dial-out machines of trusted callers. Depending on your site's security policy, either you or the trusted callers might be responsible for setting up CHAP authentication.

For remote callers to configure CHAP, ensure that the callers' local CHAP secrets match the callers' equivalent CHAP secrets in the dial-in server's /etc/ppp/chap-secrets file. Then give the callers the tasks in this section for configuring CHAP.

Configuring CHAP for trusted callers involves two tasks:

• Creating the callers' CHAP security credentials

• Configuring the callers' dial-out machines to support CHAP authentication

How to Configure CHAP Authentication Credentials for the Trusted Callers

This procedure shows how to set up CHAP credentials for two trusted callers. The steps in the procedure assume that you, the system administrator, are creating the CHAP credentials on the trusted callers' dial-out machines.

1. Become an administrator on the dial-out machine.

   For more information, see How to Use Your Assigned Administrative Rights in Oracle Solaris 11.1 Administration: Security Services.

   Using the sample CHAP configuration in Example of a Configuration Using CHAP Authentication, assume that the dial-out machine belongs to trusted caller account1.

2. Modify the chap-secrets database for caller account1.

   This release includes an /etc/ppp/chap-secrets file that has helpful comments but no options. You can add the following options to the existing /etc/ppp/chap-secrets file.

   account1  CallServe   key123   *

   CallServe is the name for the peer that account1 is trying to reach. key123 is the CHAP secret to be used for links between account1 and CallServer.

3. Become an administrator on the dial-out machine.

   For more information, see How to Use Your Assigned Administrative Rights in Oracle Solaris 11.1 Administration: Security Services.

   Assume that this machine belongs to caller account2.

4. Modify the /etc/ppp/chap-secrets database for caller account2.

   account2  CallServe   key456   *

   Now, account2 has secret key456 as its CHAP credentials for use over links to peer CallServe.

See Also

The following list provides references to related information.

• How to Create a CHAP Credentials Database (Dial-in Server)

• How to Configure CHAP Authentication Credentials for the Trusted Callers

Adding CHAP to the Configuration Files (Dial-out Machine)

To learn more about CHAP authentication, refer to Challenge-Handshake Authentication Protocol (CHAP). The next task configures the dial-out machine that belongs to caller account1, which is introduced in Example of a Configuration Using CHAP Authentication.

How to Add CHAP Support to the PPP Configuration Files (Dial-out Machine)

1. Log in to the dial-out machine as superuser.
2. Ensure that the /etc/ppp/options file has the following options.

   # cat /etc/ppp/options
   lock
   nodefaultroute

3. Create an /etc/ppp/peers/peer-name file for the remote machine CallServe.

   # cat /etc/ppp/peers/CallServe
   /dev/cua/a
   57600
   noipdefault
   defaultroute
   idle 120
   user account1
   connect "chat -U 'mypassword' -f /etc/ppp/mychat"

   The option user account1 sets account1 as the CHAP user name to be given to CallServe. For a description of the other options in the previous file, see the similar /etc/ppp/peers/myserver file in How to Define the Connection With an Individual Peer.

See Also

To test CHAP authentication by calling the dial-in server, refer to How to Call the Dial-in Server.