Web Agent Guides › Web Agent Configuration Guide › Use Web Agents with Proxy Servers › Configure Agents that Sit behind Proxy Servers › Customize the Cache-Control and ExpireForProxy Header Settings

Customize the Cache-Control and ExpireForProxy Header Settings

You can customize the cache-control and ExpireForProxy headers to secure Web resources without affecting in-place activation of application files (.doc, .pdf, and so on). You can set specific HTTP headers for the following types of content independently to further characterize the data handled by the proxy server:

• Auto-Authorized
• Unprotected
• Protected

Important! We recommend using the default settings unless you are familiar with the ramifications of changing these settings in accordance with RFC 2068. If you plan to change the default settings, note that the SiteMinder session cookie is updated on access of an unprotected page once a user has a session in order to track idle timeout. Therefore, unprotected pages should not be cached on a proxy that caches HTTP headers.

The following characteristics apply to setting headers to prevent caching by proxies:

• All redirects set a Cache-Control: no-cache header, regardless of agent activity.
• The web server sends the appropriate headers back to the proxy/client based on the HTTP protocol used (1.0 or 1.1 and higher).

All parameters should be configured using multi-value strings to suit the use of multiple headers, such as cache-control: private and cache-control: max-age=60.

The following is the new configuration:

1. ProxyHeadersDefaultTime - defaults to 60 seconds
2. ProxyHeadersTimeoutPercentage – defaults to 10 percent
3. Auto-authorized resources:
   • For HTTP/1.1, configure ProxyHeadersAutoAuth parameter(s):
   • ProxyHeadersAutoAuth

     Note: You must add this parameter manually.

     Default: Expires: Thu, 01 Dec 1994 16:00:00 GMT

     Example (suggested setting): ProxyHeadersAutoAuth="Cache-control: max-age=60"

   • For HTTP/1.0, configure ProxyHeadersAutoAuth10 parameter(s):
   • ProxyHeadersAutoAuth10

     Note: You must add this parameter manually.

     Default: Expires: Thu, 01 Dec 1994 16:00:00 GMT

     Example (suggested setting): ProxyHeadersAutoAuth10="Expires: Thu, 01 Dec 1994 16:00:00 GMT"

4. Unprotected content:
   • For HTTP/1.1, configure ProxyHeadersUnprotected parameter(s):
   • ProxyHeadersUnprotected

     Note: You must add this parameter manually.

     Default: Expires: Thu, 01 Dec 1994 16:00:00 GMT

     Cache-Control: no-cache

     Example (suggested setting): ProxyHeadersUnprotected="Cache-Control: private"

     ProxyHeadersUnprotected="Cache-Control: max-age=60"

   • For HTTP/1.0, configure ProxyHeadersUnprotected10 parameter(s):
   • ProxyHeadersUnprotected10

     Note: You must add this parameter manually.

     Default: Expires: Thu, 01 Dec 1994 16:00:00 GMT

     Cache-Control: no-cache

     Example (suggested setting): ProxyHeadersUnprotected10="Expires: Thu, 01 Dec 1994 16:00:00 GMT"

5. Protected content:
   • For HTTP/1.1, configure ProxyHeadersProtected parameter(s):
   • ProxyHeadersProtected

     Note: You must add this parameter manually.

     Default: Expires: Thu, 01 Dec 1994 16:00:00 GMT

     Cache-Control: no-cache

     Example (suggested settings): ProxyHeadersProtected="Cache-Control: private"

     ProxyHeadersProtected="Cache-Control: max-age=60"

   • For HTTP/1.0, configure ProxyHeadersProtected10 parameter(s):
   • ProxyHeadersProtected10

     Note: You must add this parameter manually.

     Default: Expires: Thu, 01 Dec 1994 16:00:00 GMT

     Cache-Control: no-cache

     Example (suggested settings): ProxyHeadersProtected10="Expires: Thu, 01 Dec 1994 16:00:00 GMT"

When configuring multiple headers, (for example, the cache-control headers in the suggested setting for unprotected HTTP/1.1 content), note the following:

• You must have multiple occurrences of the configuration parameter and you cannot separate these with a comma (,) or the plus-sign (+).
• As the values for these configuration parameters are HTTP response headers, they must comply with RFC 2616 (for HTTP/1.1), RFC 1945 (for HTTP/1.0) and RFC 822. Both HTTP/1.1 and HTTP/1.0 specify the format for an HTTP Header as that of an RFC 822 message, namely "Name: Value" (Name, followed by a colon, white space and then a value).

If you do not configure the Web Agent to set the appropriate cache expiration headers when a user accesses unprotected resources, then by default, the Web Agent will not set these headers, thereby allowing a proxy (or browser) to cache an SMSESSION cookie. This cached cookie can be re-used by the proxy (or browser) after the user has initiated a different session (and therefore a different user context), causing an unauthorized impersonation.