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This chapter describes the Cisco IOS Firewall Authentication Proxy feature. Authentication proxy provides dynamic, per-user authentication and authorization, authenticating users against industry standard TACACS+ and RADIUS authentication protocols. Authenticating and authorizing connections by user provides more robust protection against network attacks.
For a complete description of the authentication proxy commands in this chapter, refer to the "Authentication Proxy Commands" chapter of the Cisco IOS Security Command Reference. To locate documentation of other commands that appear in this chapter, use the command reference master index or search online.
This chapter has the following sections:
The Cisco IOS Firewall authentication proxy feature allows network administrators to apply specific security policies on a per-user basis. Previously, user identity and related authorized access was associated with a user's IP address, or a single security policy had to be applied to an entire user group or sub network. Now, users can be identified and authorized on the basis of their per-user policy, and access privileges tailored on an individual basis are possible, as opposed to general policy applied across multiple users.
With the authentication proxy feature, users can log in to the network or access the Internet via HTTP, and their specific access profiles are automatically retrieved and applied from a CiscoSecure ACS, or other RADIUS, or TACACS+ authentication server. The user profiles are active only when there is active traffic from the authenticated users.
The authentication proxy is compatible with other Cisco IOS security features such as Network Address Translation (NAT), Context-based Access Control (CBAC), IP Security (IPSec) encryption, and Cisco Secure VPN Client (VPN client) software.
This section has the following sections:
Figure 17 illustrates the authentication proxy HTML login page.
Users must successfully authenticate with the authentication server by entering a valid username and password.
If the authentication succeeds, the user's authorization profile is retrieved from the AAA server. The authentication proxy uses the information in this profile to create dynamic access control entries (ACEs) and add them to the inbound (input) access control list (ACL) of an input interface, and to the outbound (output) ACL of an output interface, if an output ACL exists at the interface. By doing this, the firewall allows authenticated users access to the network as permitted by the authorization profile. For example, a user can initiate a Telnet connection through the firewall if Telnet is permitted in the user's profile.
If the authentication fails, the authentication proxy reports the failure to the user, and prompts the user with multiple retries. If the user fails to authenticate after five attempts, the user must wait two minutes and initiate another HTTP session to trigger authentication proxy.
The login page is refreshed each time the user makes requests to access information from a web server.
The authentication proxy customizes each of the access list entries in the user profile by replacing the source IP addresses in the downloaded access list with the source IP address of the authenticated host.
At the same time that dynamic ACEs are added to the interface configuration, the authentication proxy sends a message to the user confirming that the login was successful. Figure 18 illustrates the login status in the HTML page.
The authentication proxy sets up an inactivity (idle) timer for each user profile. As long as there is activity through the firewall, new traffic initiated from the user's host does not trigger the authentication proxy, and authorized user traffic is permitted access through the firewall.
If the idle timer expires, the authentication proxy removes the user's profile information and dynamic access lists entries. When this happens, traffic from the client host is blocked. The user must initiate another HTTP connection to trigger the authentication proxy.
This section has the following sections:
Users should enable JavaScript on the browser prior to initiating an HTTP connection. With JavaScript enabled on the browser, secure authentication is done automatically, and the user sees the authentication message shown in Figure 18. The HTTP connection is completed automatically for the user.
If the client browser does not support JavaScript, or if site security policy prevents users from enabling JavaScript, any login attempt generates a popup window with instructions for manually completing the connection. Figure 19 illustrates the authentication proxy login status message with JavaScript disabled on the browser.
To close this window, click Close on the browser File menu.
After closing the popup window, the user should click Reload (Refresh for Internet Explorer) on the browser window in which the authentication login page is displayed. If the user's last authentication attempt succeeds, clicking Reload brings up the web page the user is trying to retrieve. If the user's last attempt fails, clicking Reload causes the authentication proxy to intercept the client HTTP traffic again, prompting the user with another login page soliciting the username and password.
If JavaScript is not enabled, it is strongly recommended that site administrators advise users of the correct procedure for closing the popup window as described in the "Establishing User Connections with JavaScript Disabled" section.
Unlike some Cisco IOS Firewall features that operate transparently to the user, the authentication proxy feature requires some user interaction on the client host. Table 20 describes the interaction of the authentication proxy with the client host.
| Authentication Proxy Action with Client | Description |
|---|---|
Triggering on HTTP connections | If a user is not currently authenticated at the firewall router, any HTTP connection initiated by the user triggers the authentication proxy. If the user is already authenticated, the authentication proxy is transparent to the user. |
Logging in using the login page | Triggering the authentication proxy generates an HTML-based login page.The user must enter a username and password to authenticate with the AAA server. Figure 17 illustrates the authentication proxy login page. |
Authenticating the user at the client | Following the login attempt, the authentication proxy action can vary depending on whether JavaScript is enabled in the browser. If JavaScript is enabled, and authentication is successful, the authentication proxy displays a message indicating the status of the authentication as shown in Figure 18. After displaying the authentication status, the proxy automatically completes the HTTP connection. If JavaScript is disabled, and authentication is successful, the authentication proxy generates a popup window with additional instructions for completing the connection. See Figure 19. If authentication is unsuccessful in any case, the user must log in again from the login page. |
Here are a few examples of when you might use the authentication proxy:
Apply the authentication proxy in the inbound direction at any interface on the router where you want per-user authentication and authorization. Applying the authentication proxy inbound at an interface causes it to intercept a user's initial connection request before that request is subjected to any other processing by the firewall. If the user fails to authenticate with the AAA server, the connection request is dropped.
How you apply the authentication proxy depends on your security policy. For example, you can block all traffic through an interface, and enable the authentication proxy feature to require authentication and authorization for all user initiated HTTP connections. Users are authorized for services only after successful authentication with the AAA server.
The authentication proxy feature also allows you to use standard access lists to specify a host or group of hosts whose initial HTTP traffic triggers the proxy.
Figure 20 shows the authentication proxy applied at the LAN interface with all network users required to authenticate upon the initial connection (all traffic is blocked at each interface).
Figure 21 shows the authentication proxy applied at the dial-in interface with all network traffic blocked at each interface.
Using a one-time password, users enter the username and one-time password in the HTML login page as usual.
Users must enter the correct token password within the first three attempts. After three incorrect entries, the user must enter two valid token passwords in succession before authentication is granted with the AAA server.
The authentication proxy is compatible with Cisco IOS software and with Cisco IOS security features:
The authentication proxy works transparently with the Cisco IOS Firewall IDS and IPSec encryption features. The following sections describe the relationship of the NAT, CBAC, and VPN client software features with the authentication proxy:
The authentication proxy feature is compatible with NAT; however, to run successfully with NAT, you must configure CBAC.
For example, when dynamic NAT is configured, the client's IP address might be translated to different addresses during the time the user is authenticated with the authentication proxy. Assume that the client is running a HTTP session. The user's original IP address is 10.1.1.1, which is translated by NAT to 192.168.2.2. NAT guarantees that during this session, 10.1.1.1 is always translated to 192.168.2.2. When the user is first authenticated, a set of dynamic ACEs is created to support the user. Subsequent sessions can use different NAT addresses, which are not covered by the original dynamic ACEs created by the authentication proxy. In this case, it is strongly recommended that you configure CBAC to take care of the translated addresses and to create the matching ACEs.
CBAC ensures that the translated address for the session is associated with the original host address.
To run successfully in all configurations, and to ensure return traffic for authorized user connections is permitted through the firewall, configure CBAC with the authentication proxy.
Because the authentication proxy does not create ACEs to support return traffic or data channel traffic, you must either create static ACLs to allow the return traffic or configure CBAC inspection rules in the firewall configuration.
Using the authentication proxy, network administrators can apply an extra layer of security and access control for VPN client traffic. If a VPN client initiates an HTTP connection, the authentication proxy first checks for prior client authentication. If the client is authenticated, authorized traffic is permitted. If the client is not authenticated, the HTTP request triggers the authentication proxy, and the user is prompted for a username and password.
If the user authentication is successful, the authentication proxy retrieves the user profile from the AAA server. The source address in the user profile entries is replaced with the IP address of the authenticated VPN client from the decrypted packet.
The authentication proxy monitors the level of incoming HTTP requests. For each request, the authentication proxy prompts for the user's login credentials. A high number of open requests could indicate that the router is the subject of a denial-of-service (DoS) attack. The authentication proxy limits the level of open requests and drops additional requests until the number of open requests has dropped below 40.
If the firewall is experiencing a high level of connection requests requiring authentication, legitimate network users might experience delays when making connections, or the connection might be rejected and the user must try the connection again.
Lock-and-key is another Cisco IOS Firewall feature that uses authentication and dynamic access list to provide user access through the firewall. Table 21 compares the authentication proxy and Lock-and-key features.
| Lock-and-Key | Authentication Proxy |
|---|---|
Triggers on Telnet connection requests. | Triggers on HTTP connection requests. |
TACACS+, RADIUS, or local authentication. | TACACS+ or RADIUS authentication and authorization. |
Access lists are configured on the router only. | Access lists are retrieved from the AAA server only. |
Access privileges are granted based on the user's host IP address. | Access privileges are granted on a per-user and host IP address basis. |
Access lists are limited to one entry for each host IP address. | Access lists can have multiple entries as defined by the user profiles on the AAA server. |
Associates a fixed IP addresses with a specific user. Users must log in from the host with that IP address. | Allows DHCP-based host IP addresses, meaning that users can log in from any host location and obtain authentication and authorization. |
Use the authentication proxy in any network environment that provides a per-user security policy. Use Lock-and-key in network environments that might benefit from local authentication and a limited number of router-based access control policies based on host addresses. Use Lock-and-key in environments not using the Cisco Secure Integrated Software.
Prior to configuring authentication proxy, review the following:
To configure the authentication proxy feature, perform the following tasks:
For authentication proxy configuration examples using the commands in this chapter, refer to the "Authentication Proxy Configuration Examples" section at the end of this chapter.
You must configure the authentication proxy for AAA services. Use the following commands in global configuration mode to enable authorization and to define the authorization methods:
| Command | Purpose | |
|---|---|---|
Step 1 | router(config)# aaa new-model | Enables the AAA functionality on the router. |
Step 2 | router(config)# aaa authentication login default TACACS+ RADIUS | Defines the list of authentication methods at login. |
Step 3 | router(config)# aaa authorization auth-proxy default [method1 [method2...]] | Use the auth-proxy keyword to enable authentication proxy for AAA methods. |
Step 4 | router(config)# tacacs-server host hostname | Specifies an AAA server. For RADIUS servers, use the radius server host command. |
Step 5 | router(config)# tacacs-server key key | Sets the authentication and encryption key for communications between the router and the AAA server. For RADIUS servers use the radius server key command. |
Step 6 | router(config)# access-list access-list-number | Creates an ACL entry to allow the AAA server return traffic to the firewall. The source address is the IP address of the AAA server, and the destination is the IP address of the router interface where the AAA server resides. |
In addition to configuring AAA on the firewall router, the authentication proxy requires a per-user access profile configuration on the AAA server. To support the authentication proxy, configure the AAA authorization service "auth-proxy" on the AAA server as outlined here:
default authorization = permit
key = cisco
user = newuser1 {
login = cleartext cisco
service = auth-proxy
{
priv-lvl=15
proxyacl#1="permit tcp any any eq 26"
proxyacl#2="permit icmp any host 60.0.0.2"
proxyacl#3="permit tcp any any eq ftp"
proxyacl#4="permit tcp any any eq ftp-data"
proxyacl#5="permit tcp any any eq smtp"
proxyacl#6="permit tcp any any eq telnet"
}
}
Refer to the "AAA Server User Profile Example" section for sample AAA server configurations.
To use the authentication proxy, you must also enable the HTTP server on the firewall and set the HTTP server authentication method to use AAA. Enter the following commands in global configuration mode:
| Command | Purpose | |
|---|---|---|
Step 1 | router(config)# ip http server | Enables the HTTP server on the router. The authentication proxy uses the HTTP server to communicate with the client for user authentication. |
Step 2 | router(config)# ip http authentication aaa | Sets the HTTP server authentication method to AAA. |
Step 3 | router(config)# ip http access-class access-list-number | Specifies the access list for the HTTP server. Use the standard access list number configured in the "Interface Configuration" section. |
 |
Note Set the auth-cache-time option for any authentication proxy rule to a higher value than the idle timeout value for any CBAC inspection rule. When the authentication proxy removes an authentication cache along with its associated dynamic user ACL, there might be some idle connections monitored by CBAC, and removal of user-specific ACLs could cause those idle connections to hang. If CBAC has a shorter idle timeout, CBAC resets these connections when the idle timeout expires; that is, before the authentication proxy removes the user profile. |
To configure the authentication proxy, use the following commands, beginning in global configuration mode:
| Command | Purpose | |
|---|---|---|
Step 1 | router(config)# ip auth-proxy auth-cache-time min | Sets the global authentication proxy idle timeout value in minutes. If the timeout expires, user authentication entries are removed, along with any associated dynamic access lists. The default value is 60minutes. |
Step 2 | router(config)# ip auth-proxy auth-proxy-banner | (Optional) Displays the name of the firewall router in the authentication proxy login page. The banner is disabled by default. |
Step 3 | router(config)# ip auth-proxy name auth-proxy-name http[auth-cache-time min] [list std-access-list] | Creates authentication proxy rules. The rules define how you apply authentication proxy. This command associates connections initiating HTTP protocol traffic with an authentication proxy name. You can associate the named rule with an access control list, providing control over which hosts use the authentication proxy feature. If no standard access list is defined, the named authentication proxy rule intercepts HTTP traffic from all hosts whose connection initiating packets are received at the configured interface. (Optional) The auth-cache-time option overrides the global authentication proxy cache timer. This option provides more control over timeout values for a specific authentication proxy rule. If no value is specified, the proxy rule assumes the value set with the ip auth-proxy auth-cache-time command. (Optional) The list option allows you to apply a standard access list to a named authentication proxy rule. HTTP connections initiated from hosts in the access list are intercepted by the authentication proxy. |
Step 4 | router(config)# interface type | Enters interface configuration mode by specifying the interface type on which to apply the authentication proxy. |
Step 5 | router(config-if)# ip auth-proxy auth-proxy-name | In interface configuration mode, applies the named authentication proxy rule at the interface. This command enables the authentication proxy rule with that name. |
Verifying the authentication proxy configuration can have several components:
To check the current authentication proxy configuration, use the show ip auth-proxy configuration command in privileged EXEC mode:
| Command | Purpose |
|---|---|
router# show ip auth-proxy configuration | Displays the authentication proxy configuration. |
In the following example, the global authentication proxy idle timeout value is set to 60 minutes, the named authentication proxy rule is "pxy," and the idle timeout value for this named rule is 1 minute. The display shows that no host list is specified, meaning that all connections initiating HTTP traffic at the interface are subject to the authentication proxy rule.
router# show ip auth-proxy configuration Authentication cache time is 60 minutes Authentication Proxy Rule Configuration Auth-proxy name pxy http list not specified auth-cache-time 1 minutes
To verify that the authentication proxy is successfully configured on the router, ask a user to initiate an HTTP connection through the router. The user must have authentication and authorization configured at the AAA server. If the user authentication is successful, the firewall completes the HTTP connection for the user. If the authentication is unsuccessful, check the access list and the AAA server configurations.
Display the user authentication entries using the show ip auth-proxy cache command in privileged EXEC mode:
| Command | Purpose |
|---|---|
router# show ip auth-proxy cache | Displays the list of user authentication entries. |
The authentication proxy cache lists the host IP address, the source port number, the timeout value for the authentication proxy, and the state of the connection. If the authentication proxy state is HTTP_ESTAB, the user authentication was successful.
router# show ip auth-proxy cache Authentication Proxy Cache Client IP 192.168.25.215 Port 57882, timeout 1, state HTTP_ESTAB
Wait for one minute, which is the timeout value for this named rule, and ask the user to try the connection again. After one minute, the user connection is denied because the authentication proxy has removed the user's authentication entry and any associated dynamic ACLs. The user is presented with a new authentication login page and must log in again to gain access through the firewall.
To verify client connections using the authentication proxy with JavaScript enabled on the client browser, follow this procedure:
Step 2 At the authentication proxy login page, enter a username and password.
Step 3 Click OK to submit the username and password to the AAA server.
A popup window appears indicating whether the login attempt succeeded or failed. If the authentication is successful, the connection is completed automatically. If the authentication fails, the authentication proxy reports the failure to the user, and prompts the user with multiple retries.
|
Note If the authentication attempt is unsuccessful after five attempts, the user must wait two minutes and initiate another HTTP session to trigger authentication proxy. |
The authentication proxy design requires JavaScript to ensure secure authentication. You can use the authentication proxy without enabling JavaScript on the browser, but this poses a potential security risk if users do not properly establish network connections. The following procedure provides the steps to properly establish a connection with JavaScript disabled. Network administrators are strongly advised to instruct users on how to properly establish connections using the procedure in this section.
|
Note Failure to follow this procedure can cause user credentials to be passed to a network web server other than the authentication proxy or can cause the authentication proxy to reject the login attempt. |
To verify client connections using the authentication proxy with JavaScript disabled on the client browser, follow this procedure:
This generates the authentication proxy login page.
Step 2 From the authentication proxy login page at the client, enter the username and password.
Step 3 Click OK to submit the username and password to the AAA server.
A popup window appears indicating whether the login attempt succeeded or failed. If the popup window indicates successful authentication, go to Step 7.
Step 4 If the popup window displays a failed authentication message, click Close on the browser File menu.
|
Note Do not click Reload (Refresh for Internet Explorer) to close the popup window. |
Step 5 From the original authentication login page, click Reload (Refresh for Internet Explorer) on the browser toolbar. The user login credentials are cleared from the form.
|
Note Do not click OK. You must click Reload or Refresh to clear the username and password and to reload the form before attempting to log in again. |
Step 6 Enter the username and password again.
If the authentication is successful, a window appears displaying a successful authentication message. If the window displays a failed authentication message, go to Step 4.
Step 7 Click Close on the browser File menu.
Step 8 From the original authentication proxy login page, click Reload (Refresh for Internet Explorer) on the browser toolbar.
The authentication proxy completes the authenticated connection with the web server.
This section describes how to view dynamic access list entries and how to manually remove authentication entries. This section contains the following sections:
To view dynamic access lists and any temporary access list entries that are currently established by the authentication proxy, use the show ip access-lists command in privileged EXEC mode:
| Command | Purpose |
|---|---|
router# show ip access-lists | Displays the standard and extended access lists configured on the firewall, including dynamic ACL entries. |
Consider the following example where ACL 105 is applied inbound at the input interface where you configure authentication proxy. The initial display shows the contents of the ACLs prior to authentication. The second display shows the same displays after user authentication with the AAA server.
|
Note If NAT is configured, the show ip access list command might display the translated host IP address for the dynamic ACL entry. This depends on whether the ACL is applied on the interface where NAT is applied inside or outside. If the ACL is applied on the NAT outside interface, the translated address is displayed. If the ACL is applied on the NAT inside interface, the IP address of the host initiating the connection is displayed. The show ip auth-proxy cache command always displays the IP address of the host initiating the connection. |
For example, the following is a list of ACL entries prior to the authentication proxy:
Router# show ip access-lists . . . Extended IP access list 105 deny tcp any any eq telnet deny udp any any permit tcp any any (28 matches) permit ip any any
The ACL entries following user authentication are shown in boldface type:
Router# show ip access-lists . . . Extended IP access list 105 permit tcp host 192.168.25.215 any eq 26 permit icmp host 192.168.25.215 host 60.0.0.2 permit tcp host 192.168.25.215 any eq telnet permit tcp host 192.168.25.215 any eq ftp permit tcp host 192.168.25.215 any eq ftp-data permit tcp host 192.168.25.215 any eq smtpdeny tcp any any eq telnetdeny udp any anypermit tcp any any (76 matches)permit ip any any
| Command | Purpose |
|---|---|
router# clear ip auth-proxy cache | Deletes authentication proxy entries from the firewall before they time out. Use an asterisk to delete all authentication cache entries. Enter a specific IP address to delete an entry for a single host. |
Throughout these examples, the "!" symbol indicates a comment line. Comment lines precede the configuration entries being described.
The following examples highlight the specific authentication proxy configuration entries. These examples do not represent a complete router configuration. Complete router configurations using the authentication proxy are included later in this chapter.
This section has the following sections:
aaa new-model aaa authentication login default group tacacs group radius ! Set up the aaa new model to use the authentication proxy. aaa authorization auth-proxy default group tacacs group radius ! Define the AAA servers used by the router. tacacs-server host 172.31.54.143 tacacs-server key cisco radius-server host 172.31.54.143 radius-server key cisco
! Enable the HTTP server on the router. ip http server ! Set the HTTP server authentication method to AAA. ip http authentication aaa ! Define standard access list 61 to deny any host. access-list 61 deny any ! Use ACL 61 to deny connections from any host to the HTTP server. ip http access-class 61
! Set the global authentication proxy timeout value. ip auth-proxy auth-cache-time 60 ! Apply a name to the authentication proxy configuration rule. ip auth-proxy name HQ_users http
! Apply the authentication proxy rule at an interface. interface e0ip address 10.1.1.210 255.255.255.0 ip auth-proxy HQ_users
This example shows a router configuration with the authentication proxy, IPSec, and CBAC features. Figure 22 illustrates the configuration.
In this example, Host A initiates an HTTP connection with the web server (WWW). The HTTP traffic between Router 1 and Router 2 is encrypted using IPSec. The authentication proxy, IPSec, and CBAC are configured at interface Serial0 on Router 2, which is acting as the firewall. ACL 105 blocks all traffic at interface Serial0. ACL 102 is applied at interface Ethernet0 on Router 2 to block traffic on that interface, except traffic from the AAA server.
When Host A initiates an HTTP connection with the web server, the authentication proxy prompts the user at Host A for a username and password. These credentials are verified with the AAA server for authentication and authorization. If authentication is successful, the per-user ACLs are downloaded to the firewall to permit services.
The following examples provide both the Router 1 and Router 2 configurations for completeness.
! Configure Router 1 for IPSec. version 12.0 service timestamps debug uptime service timestamps log uptime no service password-encryption ! hostname Router1 ! logging buffered 4096 debugging no logging console enable secret 5 $1$E0OB$AQF1vFZM3fLr3LQAOsudL/ enable password junk ! username Router2 password 0 welcome crypto isakmp policy 1 authentication pre-share crypto isakmp key cisco1234 address 10.0.0.2 ! crypto ipsec transform-set rule_1 ah-sha-hmac esp-des esp-sha-hmac ! ! crypto map testtag 10 ipsec-isakmp set peer 10.0.0.2 set transform-set rule_1 match address 155 ! interface Ethernet0/0 ip address 192.168.23.2 255.255.255.0 no ip directed-broadcast no ip route-cache no ip mroute-cache ! interface Serial3/1 ip address 10.0.0.1 255.0.0.0 no ip directed-broadcast encapsulation PPP ip route-cache no ip mroute-cache no keepalive no fair-queue clockrate 56000 crypto map testtag ! ! ip classless ip route 192.168.123.0 255.255.255.0 10.0.0.2 ! Identify the IPSec specific traffic. access-list 155 permit tcp host 192.168.23.13 host 192.168.123.14 eq www access-list 155 permit tcp host 192.168.23.13 eq www host 192.168.123.14
! Configure Router 2 as the firewall, using the authentication proxy, IPSec, and CBAC. version 12.0 service timestamps debug uptime service timestamps log uptime no service password-encryption ! hostname Router2 ! logging buffered 4096 debugging aaa new-model aaa authentication login default group tacacs aaa authentication login console_line none aaa authentication login special none aaa authentication ppp default group tacacs aaa authorization exec default group tacacs ! Configure AAA for the authentication proxy. aaa authorization auth-proxy default group tacacs+ enable password junk ! ! Create the CBAC inspection rule HTTP_TEST. ip inspect name rule22 http ip inspect name rule22 tcp ip inspect name rule22 ftp ip inspect name rule22 smtp ! ! Create the authentication proxy rule PXY. ip auth-proxy name pxy http ! Turn on display of the router name in the authentication proxy login page. ip auth-proxy auth-proxy-banner ip audit notify log ip audit po max-events 100 ! ! Configure IPSec. crypto isakmp policy 1 authentication pre-share crypto isakmp key cisco1234 address 10.0.0.1 ! crypto ipsec transform-set rule_1 ah-sha-hmac esp-des esp-sha-hmac ! crypto map testtag 10 ipsec-isakmp set peer 10.0.0.1 set transform-set rule_1 match address 155 ! ! Apply the CBAC inspection rule and the authentication proxy rule at interface ! Serial0/0. interface Serial0/0 ip address 10.0.0.2 255.0.0.0 ip access-group 105 in no ip directed-broadcast ip inspect rule22 in ip auth-proxy pxy encapsulation ppp no ip route-cache no ip mroute-cache no keepalive no fair-queue crypto map testtag ! interface Ethernet0/1 ip address 192.168.123.2 255.255.255.0 ip access-group 102 in no ip directed-broadcast ip route-cache no ip mroute-cache ! no ip classless ip route 192.168.23.0 255.255.255.0 10.0.0.1 ip route 192.168.50.0 255.255.255.0 16.0.0.1 ! Configure the HTTP server. ip http server ip http access-class 15 ip http authentication aaa ! ! Create ACL 15 to block all traffic for the http server. access-list 15 deny any ! Create ACL 102 to block all traffic inbound on interface Ethernet0/1 except for ! traffic from the AAA server. access-list 102 permit tcp host 192.168.123.20 eq tacacs host 192.168.123.2 access-list 102 deny tcp any any access-list 102 deny udp any any access-list 102 permit ip any any ! Create ACL 105 to block all traffic inbound on interface Serial0/0. Permit only IP ! protocol traffic. access-list 105 deny tcp any any access-list 105 deny udp any any access-list 105 permit ip any any ! Identify the IPSec specific traffic. access-list 155 permit tcp host 192.168.123.14 host 192.168.23.13 eq www access-list 155 permit tcp host 192.168.123.14 eq www host 192.168.23.13 ! ! Define the AAA server host and encryption key. tacacs-server host 192.168.123.14 tacacs-server key cisco ! line con 0 exec-timeout 0 0 login authentication special transport input none line aux 0 transport input all speed 38400 flowcontrol hardware line vty 0 4 password lab
This example provides a router configuration with the authentication proxy, IPSec, NAT, and CBAC features. Figure 23 illustrates the configuration.
In this example, Host A initiates an HTTP connection with the web server (WWW). The HTTP traffic between Router 1 (interface BRI0) and Router 2 (interface Serial2) is encrypted using IPSec. The authentication proxy is configured on Router 2, which is acting as the firewall. The authentication proxy, NAT, and CBAC are configured at interface Serial2, which is acting as the firewall. ACL 105 blocks all traffic at interface Serial2. ACL 102 is applied at interface Ethernet0 on Router 2 to block traffic on that interface, except traffic from the AAA server. In this example, the authentication proxy uses standard ACL 10 to specify the hosts using the authentication proxy feature.
When any host in ACL 10 initiates an HTTP connection with the web server, the authentication proxy prompts the user at that host for a username and password. These credentials are verified with AAA server for authentication and authorization. If authentication is successful, the per-user ACLs are downloaded to the firewall to permit services.
The following examples provide both the Router 1 and Router 2 configurations for completeness.
! Configure Router 1 for IPSec. version 12.0 service timestamps debug uptime service timestamps log uptime no service password-encryption ! hostname Router1 ! logging buffered 4096 debugging no logging console ! isdn switch-type basic-5ess ! crypto isakmp policy 1 authentication pre-share crypto isakmp key cisco1234 address 16.0.0.2 crypto ipsec transform-set rule_1 ah-sha-hmac esp-des esp-sha-hmac ! ! crypto map testtag 10 ipsec-isakmp set peer 16.0.0.2 set transform-set rule_1 match address 155 ! ! process-max-time 200 ! interface BRI0 ip address 16.0.0.1 255.0.0.0 no ip directed-broadcast encapsulation ppp dialer idle-timeout 5000 dialer map ip 16.0.0.2 name router2 broadcast 50006 dialer-group 1 isdn switch-type basic-5ess crypto map testtag ! interface FastEthernet0 ip address 192.168.50.2 255.255.255.0 no ip directed-broadcast ! ip classless ip route 192.168.150.0 255.255.255.0 16.0.0.2 no ip http server ! Identify the IPSec specific traffic. access-list 155 permit tcp host 192.168.50.13 host 192.168.150.100 eq www access-list 155 permit tcp host 192.168.50.13 eq www host 192.168.150.100 dialer-list 1 protocol ip permit ! line con 0 exec-timeout 0 0 transport input none line aux 0 line vty 0 4 password lab login
! Configure Router 2 as the firewall, using the authentication proxy, IPSec, NAT, and ! CBAC. version 12.0 service timestamps debug uptime service timestamps log uptime no service password-encryption ! hostname router2 ! logging buffered 4096 debugging aaa new-model aaa authentication login default group tacacs+ aaa authentication login console_line none aaa authorization exec default group tacacs+ ! Configure AAA for the authentication proxy. aaa authorization auth-proxy default group tacacs+ ! ! Create the CBAC inspection rule "rule44." ip inspect name rule44 http java-list 5 ip inspect name rule44 tcp ip inspect name rule44 ftp ip inspect name rule44 smtp ! ! Create the authentication proxy rule "pxy." Set the timeout value for rule ! pxy to three minutes. Standard ACL 10 is applied to the rule. ip auth-proxy name pxy http list 10 auth-cache-time 3 isdn switch-type primary-5ess ! ! Configure IPSec. crypto isakmp policy 1 authentication pre-share crypto isakmp key cisco1234 address 16.0.0.1 ! ! crypto ipsec transform-set rule_1 ah-sha-hmac esp-des esp-sha-hmac ! ! crypto map testtag 10 ipsec-isakmp set peer 16.0.0.1 set transform-set rule_1 match address 155 ! controller T1 2/0 framing esf linecode b8zs pri-group timeslots 1-24 ! ! Apply ACL 102 inbound at interface Ethernet0/1 and configure NAT. interface Ethernet0/1 ip address 192.168.150.2 255.255.255.0 ip access-group 102 in no ip directed-broadcast ip nat inside no ip mroute-cache ! ! Apply the authentication proxy rule PXY, CBAC inspection rule HTTP_TEST, NAT, and ! and ACL 105 at interface Serial2/0:23. interface Serial2/0:23 ip address 16.0.0.2 255.0.0.0 ip access-group 105 in no ip directed-broadcast ip nat outside ip inspect rule44 in ip auth-proxy pxy encapsulation ppp ip mroute-cache dialer idle-timeout 5000 dialer map ip 16.0.0.1 name router1 broadcast 71011 dialer-group 1 isdn switch-type primary-5ess fair-queue 64 256 0 crypto map testtag ! ! Use NAT to translate the Web server address. ip nat inside source static 192.168.150.14 192.168.150.100 ip classless ip route 192.168.50.0 255.255.255.0 16.0.0.1 ! Configure the HTTP server. ip http server ip http access-class 15 ip http authentication aaa ! ! Create standard ACL 5 to specify the list of hosts from which to accept java applets. ! ACL 5 is used to block Java applets in the CBAC inspection rule named "rule44," which ! is applied at interface Serial2/0:23. access-list 5 permit any ! Create standard ACL 10 to specify the hosts using the authentication proxy. This ACL ! used in the authentication proxy rule named "PXY", which is applied at interface ! Serial2/0:23. access-list 10 permit any ! Create ACL 15 to block all traffic for the http server. access-list 15 deny any ! Create extended ACL 102 to block all traffic inbound on interface Ethernet0/1 ! except for traffic from the AAA server. access-list 102 permit tcp host 192.168.150.20 eq tacacs 192.168.150.2 access-list 102 deny tcp any any access-list 102 deny udp any any access-list 102 permit ip any any ! Create extended ACL 105 to block all TCP and UDP traffic inbound on interface ! Serial2/0:23. access-list 105 deny tcp any any access-list 105 deny udp any any access-list 105 permit ip any any ! Identify the IPSec specific traffic. access-list 155 permit tcp host 192.168.150.100 host 192.168.50.13 eq www access-list 155 permit tcp host 192.168.150.100 eq www host 192.168.50.13 dialer-list 1 protocol ip permit ! Define the AAA server host and encryption key. tacacs-server host 192.168.126.14 tacacs-server key cisco ! line con 0 exec-timeout 0 0 ! Define the AAA server host and encryption key. login authentication console_line transport input none line aux 0 line vty 0 4 password lab ! ! end
This section includes examples of the authentication proxy user profile entries on the AAA servers. The proxyacl entries define the user access privileges. After successfully using the authentication proxy to log in, these entries are transferred to the firewall router. Each entry in the profile must specify permit access for the service or application. The source address in each entry is set to "any," which is replaced with the IP address of the authenticating host when the profile is downloaded to the firewall. The privilege level must be set to 15 for all AAA users.
This section has the following sections:
This section describes how to configure authentication proxy on CiscoSecure ACS 2.3 for Windows NT. For detailed information about CiscoSecure ACS, refer to the documentation for that product.
The following sample configuration is for the TACACS+ service of CiscoSecure ACS for Windows NT.
a. Scroll down to New Services.
b. Add a new service, "auth-proxy" in the Service field. Leave the Protocol field empty.
c. Select both the User and Group check boxes for the new service.
d. Scoll down to Advance Configuration Options and check the Per-user Advance TACACS+ features.
e. Click Submit.
Step 2 Click the Network Configuration icon.
a. Click the Add Entry icon for Network Access Servers and fill in the Network Access Server Hostname, IP address, and key (the key configured on the router) fields.
b. Select TACACS+ (Cisco) for the Authenticate Using option.
c. Click the Submit + Restart icon.
Step 3 Click the Group Setup icon.
a. Select a user group from the drop-down menu.
b. Select the Users in Group check box.
c. Select a user from the user list.
d. In the User Setup list, scroll down to TACACS+ Settings and select the "auth-proxy" check box.
e. Select the Custom Attributes check box.
f. Add the profiles entries (do not use single or double quotes around the entries) and set the privilege level to 15.
priv-lvl=15 proxyacl#1=permit tcp any any eq 26 proxyacl#2=permit icmp any host 60.0.0.2 proxyacl#3=permit tcp any any eq ftp proxyacl#4=permit tcp any any eq ftp-data proxyacl#5=permit tcp any any eq smtp proxyacl#6=permit tcp any any eq telnet
g. Click Submit.
Step 4 Click the User Setup icon.
a. Click List All Users.
b. Add a username.
c. Scoll down to User Setup Password Authentication.
d. Select SDI SecurID Token Card from the Password Authentication drop-down menu.
e. Select the previous configured user group 1.
f. Click Submit.
Step 5 Click Group Setup icon again.
a. Select the user group 1.
b. Click Users in Group.
c. Click Edit Settings.
d. Click the Submit + Restart icon to make sure the latest configuration is updated and sent to the AAA server.
This section describes how to configure authentication proxy on CiscoSecure ACS 2.3 for UNIX. For detailed information regarding CiscoSecure ACS, refer to the documentation for that product.
To manage the CiscoSecure ACS using the Administrator program, you need a web browser that supports Java and JavaScript. You must enable Java in the browser application. You can start the Java-based CiscoSecure Administrator advanced configuration program from any of the CiscoSecure ACS Administrator web pages.
The following sample configuration procedure is for the TACACS+ service of CiscoSecure ACS 2.3 for UNIX.
The Java-based CiscoSecure Administrator advanced configuration program appears. It might require a few minutes to load.
Step 2 In the CiscoSecure Administrator advanced configuration program, locate and deselect Browse in the Navigator pane of the tabbed Members page.
This displays the Create New Profile icon.
Step 3 In the Navigator pane, do one of the following:
Step 4 Click Create Profile to display the New Profile dialog box.
Step 5 Make sure the Group check box is cleared.
Step 6 Enter the name of the user you want to create and click OK. The new user appears in the tree.
Step 7 Click the icon for the group or user profile in the tree that is displayed in the Navigator pane of the tabbed Members page.
Step 8 If necessary, in the Profile pane, click the Profile icon to expand it.
A list or dialog box that contains attributes applicable to the selected profile or service appears in the window at the bottom right of the screen. The information in this window changes depending on what you have selected in the Profile pane.
Step 9 Click Service-String.
Step 10 Click string, enter auth-proxy in the text field, and click Apply.
Step 11 Select the Option menu.
Step 12 On the Option menu, click Default Attributes.
Step 13 Change the attribute from Deny to Permit.
Step 14 Click Apply.
Step 15 On the Option menu, click Attribute and enter the privilege level in the text field:
priv-lvl=15
Step 16 On the Option menu, click Attribute and enter the proxyacl entries in the text field:
proxyacl#1="permit tcp any any eq 26"
Repeat this step for each additional service or protocol to add:
proxyacl#2="permit icmp any host 60.0.0.2" proxyacl#3="permit tcp any any eq ftp" proxyacl#4="permit tcp any any eq ftp-data" proxyacl#5="permit tcp any any eq smtp" proxyacl#6="permit tcp any any eq telnet"
Step 17 When you have finished making all your changes, click Submit.
default authorization = permit
key = cisco
user = Brian {
login = cleartext cisco
service = auth-proxy
{
priv-lvl=15
proxyacl#1="permit tcp any any eq 26"
proxyacl#2="permit icmp any host 60.0.0.2
proxyacl#3="permit tcp any any eq ftp"
proxyacl#4="permit tcp any any eq ftp-data"
proxyacl#5="permit tcp any any eq smtp"
proxyacl#6="permit tcp any any eq telnet"
}
}
Bob Password = "cisco" User-Service-Type=Outbound-User cisco-avpair = "auth-proxy:priv-lvl=15", cisco-avpair = "auth-proxy:proxyacl#1=permit tcp any any eq 26", cisco-avpair = "auth-proxy:proxyacl#2=permit icmp any host 60.0.0.2", cisco-avpair = "auth-proxy:proxyacl#3=permit tcp any any eq ftp", cisco-avpair = "auth-proxy:proxyacl#4=permit tcp any any eq ftp-data", cisco-avpair = "auth-proxy:proxyacl#5=permit tcp any any eq smtp", cisco-avpair = "auth-proxy:proxyacl#6=permit tcp any any eq telnet"
Alice Password = "cisco" User-Service = Dialout-Framed-User cisco-avpair = "auth-proxy:priv-lvl=15", cisco-avpair = "auth-proxy:proxyacl#1=permit tcp any any eq 26", cisco-avpair = "auth-proxy:proxyacl#2=permit icmp any host 60.0.0.2", cisco-avpair = "auth-proxy:proxyacl#3=permit tcp any any eq ftp", cisco-avpair = "auth-proxy:proxyacl#4=permit tcp any any eq ftp-data", cisco-avpair = "auth-proxy:proxyacl#5=permit tcp any any eq smtp", cisco-avpair = "auth-proxy:proxyacl#6=permit tcp any any eq telnet"
Posted: Thu Aug 10 08:50:34 PDT 2000
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