Clientless SSL VPN (WebVPN) allows for limited but valuable secure access to the corporate network from any location. Users can achieve secure browser-based access to corporate resources at anytime. This document provides a straightforward configuration for the Cisco Adaptive Security Appliance (ASA) 5500 series to allow Clientless SSL VPN access to internal network resources.
The SSL VPN technology can be utilized in three ways: Clientless SSL VPN, Thin-Client SSL VPN (Port Forwarding), and SSL VPN Client (SVC Tunnel Mode). Each has its own advantages and unique access to resources.
1. Clientless SSL VPN
A remote client needs only an SSL-enabled web browser to access http- or https-enabled web servers on the corporate LAN. Access is also available to browse for Windows files with the Common Internet File System (CIFS). A good example of http access is the Outlook Web Access (OWA) client.
2. Thin-Client SSL VPN (Port Forwarding)
A remote client must download a small, Java-based applet for secure access of TCP applications that use static port numbers. UDP is not supported. Examples include access to POP3, SMTP, IMAP, SSH, and Telnet. The user needs local administrative privileges because changes are made to files on the local machine. This method of SSL VPN does not work with applications that use dynamic port assignments, for example, several FTP applications.
Refer to Thin-Client SSL VPN (WebVPN) on ASA using ASDM Configuration Example in order to learn more about the Thin-Client SSL VPN.
3. SSL VPN Client (SVC-Tunnel Mode)
The SSL VPN Client downloads a small client to the remote workstation and allows full, secure access to the resources on the internal corporate network. The SVC can be downloaded permanently to the remote station, or it can be removed after the secure session ends.
Clientless SSL VPN can be configured on the Cisco VPN Concentrator 3000 and specific Cisco IOS® routers with Version 12.4(6)T and higher. Clientless SSL VPN access can also be configured on the Cisco ASA at the Command Line Interface (CLI) or with the Adaptive Security Device Manager (ASDM). The ASDM usage makes configurations more straightforward.
Clientless SSL VPN and ASDM must not be enabled on the same ASA interface. It is possible for the two technologies to coexist on the same interface if changes are made to the port numbers. It is highly recommended that ASDM is enabled on the inside interface, so WebVPN can be enabled on the outside interface.
Refer to SSL VPN Client (SVC) on ASA Using ASDM Configuration Example in order to know more details about the SSL VPN Client.
Clientless SSL VPN enables secure access to these resources on the corporate LAN:
HTTP and HTTPS to internal web servers
Windows file access and browsing
Citrix Servers with the Citrix thin client
The Cisco ASA adopts the role of a secure proxy for client computers which can then access pre-selected resources on the corporate LAN.
This document demonstrates a simple configuration with ASDM to enable the use of Clientless SSL VPN on the Cisco ASA. No client configuration is necessary if the client already has an SSL-enabled web browser. Most web browsers already have the capability to invoke SSL/TLS sessions. The resultant Cisco ASA command lines are also shown in this document.
Ensure that you meet these requirements before you attempt this configuration:
Client-SSL enabled browser, for example, Internet Explorer, Netscape, and Mozilla
ASA with Version 7.1 or higher
TCP port 443, which must not be blocked along the path from the client to the ASA
The information in this document is based on these software and hardware versions:
Cisco ASA Software Version 7.2(1)
Cisco ASDM 5.2(1)
Note: Refer to Allowing HTTPS Access for ASDM in order to allow the ASA to be configured by the ASDM.
Cisco ASA 5510 series
The information in this document was created from the devices in a specific lab environment. All the devices used in this document began with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.
Refer to the Cisco Technical Tips Conventions for more information on document conventions.
At this stage, you can issue the https://inside _IP Address from a web browser to access the ASDM application. Once ASDM has loaded, begin the configuration for WebVPN.
This section contains the information needed to configure the features described within this document.
This document uses this network setup:
Configure the WebVPN on the ASA with four major steps:
Enable the WebVPN on an ASA interface.
Create a list of servers and/or URLs for WebVPN access.
Create a group policy for WebVPN users.
Apply the new group policy to a Tunnel Group.
In ASDM, choose Configuration > VPN > WebVPN > WebVPN Access.
Choose the interface to terminate WebVPN users > Enable > Apply.
Choose Servers and URLs > Add.
Enter a name for the list of servers accessible by WebVPN. Click the Add button. The Add Server or URL dialogue box displays. Enter the name of each server. This is the name that the client sees. Choose the URL drop-down menu for each server and choose the appropriate protocol. Add servers to your list from the Add Server or URL dialogue box and click OK.
Click Apply > Save.
Expand General in the left menu of ASDM. Choose Group Policy > Add.
Choose Add Internal Group Policy. Uncheck the Tunneling Protocols: Inherit check box. Check the WebVPN check box.
Choose the WebVPN tab. Uncheck the Inherit check box. Choose from the list of features. Click OK > Apply.
Choose the Tunnel Group in the left column. Click the Edit button.
Click the Group Policy drop-down menu. Choose the policy that was created in Step 3.
It is important to note that if new Group Policies and Tunnel Groups are not created, the defaults are GroupPolicy 1 and DefaultWEBVPNGroup. Click the WebVPN tab.
Choose NetBIOS Servers. Click the Add button. Fill in the IP address of the WINS/NBNS server. Click OK > OK. Follow the prompts Apply > Save > Yes to write the configuration.
This configuration reflects the changes ASDM made to enable WebVPN:
ciscoasa#show running-config Building configuration... ASA Version 7.2(1) hostname ciscoasa domain-name cisco.com enable password 9jNfZuG3TC5tCVH0 encrypted names dns-guard interface Ethernet0/0 nameif outside security-level 0 ip address 172.22.1.160 255.255.255.0 interface Ethernet0/1 nameif inside security-level 100 ip address 10.2.2.1 255.255.255.0 interface Ethernet0/2 nameif DMZ1 security-level 50 no ip address interface Management0/0 description For Mgt only shutdown nameif Mgt security-level 0 ip address 10.10.10.1 255.255.255.0 management-only passwd 2KFQnbNIdI.2KYOU encrypted ftp mode passive dns server-group DefaultDNS domain-name cisco.com pager lines 24 logging enable logging asdm informational mtu outside 1500 mtu inside 1500 mtu DMZ1 1500 mtu Mgt 1500 icmp permit any outside asdm image disk0:/asdm521.bin no asdm history enable arp timeout 14400 global (outside) 1 interface nat (inside) 1 10.2.2.0 255.255.255.0 route outside 0.0.0.0 0.0.0.0 172.22.1.1 1 timeout xlate 3:00:00 timeout conn 1:00:00 half-closed 0:10:00 udp 0:02:00 icmp 0:00:02 timeout sunrpc 0:10:00 h323 0:05:00 h225 1:00:00 mgcp 0:05:00 mgcp-pat 0:05:00 timeout sip 0:30:00 sip_media 0:02:00 sip-invite 0:03:00 sip-disconnect 0:02:00 timeout uauth 0:05:00 absolute ! !--- group policy configurations ! group-policy GroupPolicy1 internal group-policy GroupPolicy1 attributes vpn-tunnel-protocol IPSec l2tp-ipsec webvpn webvpn functions url-entry file-access file-entry file-browsing mapi port-forward filter http-proxy auto-download citrix username cisco password 53QNetqK.Kqqfshe encrypted ! !--- asdm configurations ! http server enable http 10.2.2.0 255.255.255.0 inside ! no snmp-server location no snmp-server contact snmp-server enable traps snmp authentication linkup linkdown coldstart ! !--- tunnel group configurations ! tunnel-group DefaultWEBVPNGroup general-attributes default-group-policy GroupPolicy1 tunnel-group DefaultWEBVPNGroup webvpn-attributes nbns-server 10.2.2.2 master timeout 2 retry 2 ! telnet timeout 5 ssh 172.22.1.0 255.255.255.0 outside ssh timeout 5 console timeout 0 ! class-map inspection_default match default-inspection-traffic ! policy-map type inspect dns preset_dns_map parameters message-length maximum 512 policy-map global_policy class inspection_default inspect dns preset_dns_map inspect ftp inspect h323 h225 inspect h323 ras inspect rsh inspect rtsp inspect esmtp inspect sqlnet inspect skinny inspect sunrpc inspect xdmcp inspect sip inspect netbios inspect tftp ! service-policy global_policy global ! !--- webvpn configurations ! webvpn enable outside url-list ServerList "WSHAWLAP" cifs://10.2.2.2 1 url-list ServerList "FOCUS_SRV_1" https://10.2.2.3 2 url-list ServerList "FOCUS_SRV_2" http://10.2.2.4 3 ! prompt hostname context ! end
Clientless SSL VPN macro substitutions let you configure users for access to personalized resources that contain the user ID and password or other input parameters. Examples of such resources include bookmark entries, URL lists, and file shares.
Note: For security reasons, password substitutions are disabled for file-access URLs (cifs://).
Note: Also for security reasons, use caution when you introduce password substitutions for web links, especially for non-SSL instances.
These macro substitutions are supported:
CSCO_WEBVPN_USERNAME - SSL VPN user login ID
CSCO_WEBVPN_PASSWORD - SSL VPN user login password
CSCO_WEBVPN_INTERNAL_PASSWORD - SSL VPN user internal resource password
CSCO_WEBVPN_CONNECTION_PROFILE - SSL VPN user login group drop-down, a group alias within the connection profile
CSCO_WEBVPN_MACRO1 - Set through RADIUS/LDAP vendor-specific attribute
CSCO_WEBVPN_MACRO2 - Set through RADIUS/LDAP vendor-specific attribute
In order to know more about macro substitutions, refer to Clientless SSL VPN Macro Substitutions.
Use this section to confirm that your configuration works properly.
Establish a connection to your ASA device from an outside client to test this:
The client receives a Cisco WebVPN page that allows access to the corporate LAN in a secure fashion. The client is allowed only the access that is listed in the newly created group policy.
Authentication:A simple login and password was created on the ASA for this lab proof of concept. If a single and seamless sign-on to a domain for the WebVPN users is preferred, refer to this URL:
This section provides information you can use to troubleshoot your configuration.
Note: Do not interrupt the Copy File to Server command or navigate to a different screen while the copy process is in progress. If the operation is interrupted, it can cause an incomplete file to be saved on the server.
Note: Users can upload and download the new files with the WEBVPN client, but the user is not allowed to overwrite the files in CIFS on WEB VPN with the Copy File to Server command. When the user attempts to replace a file on the server, the user receives this message: "Unable to add the file."
Follow these instructions to troubleshoot your configuration.
In ASDM, choose Monitoring > Logging > Real-time Log Viewer > View. When a client connects to the ASA, note the establishment and termination of SSL and TLS sessions in the real-time logs.
In ASDM, choose Monitoring > VPN > VPN Statistics > Sessions. Look for the new WebVPN session. Be sure to choose the WebVPN filter and click Filter. If a problem occurs, temporarily bypass the ASA device to ensure that clients can access the desired network resources. Review the configuration steps listed in this document.
Note: Refer to Important Information on Debug Commands before the use of debug commands.
show webvpn ?—There are many show commands associated with WebVPN. In order to see the use of show commands in detail, refer to the command reference section of the Cisco Security Appliance.
debug webvpn ?—The use of debug commands can adversely impact the ASA. In order to see the use of debug commands in more detail, refer to the command reference section of the Cisco Security Appliance.
Only three WEB VPN clients can connect to ASA/PIX; the connection for the fourth client fails.
In most cases, this issue is related to a simultaneous login setting within the group policy.
Use this illustration to configure the desired number of simultaneous logins. In this example, the desired value was 20.
ciscoasa(config)# group-policy Bryan attributes ciscoasa(config-group-policy)# vpn-simultaneous-logins 20
If these bookmarks were configured for users to sign in to the clientless VPN, but, on the home screen under "Web Applications" they show up as grayed out, how can I enable these HTTP links so that the users are able to click them and go into the particular URL?
You should first make sure that the ASA can resolve the websites through DNS. Try to ping the websites by name. If the ASA cannot resolve the name, the link is grayed out. If the DNS servers are internal to your network, configure the DNS domain-lookup private interface.
The error message "the ica client received a corrupt ica file." occurs for Citrix over WEBVPN.
If you use the secure gateway mode for Citrix connection through WebVPN, the ICA file can corrupt. Because the ASA is not compatible with this mode of operation, create a new ICA file in the Direct Mode (non-secure mode).
When accessing CIFS links on the clientless WebVPN portal, users are prompted for credentials after clicking the bookmark. LDAP is used to authenticate both the resources and the users already have entered LDAP credentials to login to the VPN session.
You can use the auto-signon feature in this case. Under the specific group-policy being used and under its WebVPN attributes, configure this:
auto-signon allow uri cifs://X.X.X.X/* auth-type all
where X.X.X.X=IP of the CIFS server and *=rest of the path to reach the share file/folder in question.
An example configuration snippet is shown here:
hostname(config)# group-policy ExamplePolicy attributes hostname(config-group-policy)# webvpn hostname(config-group-webvpn)# auto-signon allow uri https://*.example.com/* auth-type all
For more information about this, refer to Configuring SSO with HTTP Basic or NTLM Authentication.
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Refer to Cisco Technical Tips Conventions for information on conventions used in this document.