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 16-4 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 19-4 Task Map for CHAP Authentication (Dial-in Server)
Table 19-5 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.
Note - UNIX or PAM authentication mechanisms do not work with CHAP. For example, you cannot
use the PPP login option as described in How to Create a PAP Credentials Database (Dial-in Server). If your authentication scenario requires
PAM or UNIX-style authentication, choose PAP instead.
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)
- 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.
- 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.
- Become superuser on the dial-in server or assume an equivalent role.
Roles contain authorizations and privileged commands. For more information about roles, see Configuring RBAC (Task Map) in System Administration Guide: Security Services. To configure
a role with the Primary Administrator profile, see Chapter 2, Working With the Solaris Management Console (Tasks), in System Administration Guide: Basic Administration.
- Modify the /etc/ppp/chap-secrets file.
Solaris PPP 4.0 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.
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)
- Log in to the dial-in server as superuser.
- 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
- 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:
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.
- Become superuser on a dial-out machine or assume an equivalent role.
Roles contain authorizations and privileged commands. For more information about roles, see Configuring RBAC (Task Map) in System Administration Guide: Security Services. To configure
a role with the Primary Administrator profile, see Chapter 2, Working With the Solaris Management Console (Tasks), in System Administration Guide: Basic Administration.
Using the sample CHAP configuration in Example of a Configuration Using CHAP Authentication, assume that the dial-out machine belongs to
trusted caller account1.
- Modify the chap-secrets database for caller account1.
Solaris PPP 4.0 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.
- Become superuser on another dial-out machine or assume an equivalent role.
Roles contain authorizations and privileged commands. For more information about roles, see Configuring RBAC (Task Map) in System Administration Guide: Security Services. To configure
a role with the Primary Administrator profile, see Chapter 2, Working With the Solaris Management Console (Tasks), in System Administration Guide: Basic Administration.
Assume that this machine belongs to caller account2.
- 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.
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)
- Log in to the dial-out machine as superuser.
- Ensure that the /etc/ppp/options file has the following options.
# cat /etc/ppp/options
lock
nodefaultroute
- 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.
