Federation Security Services Guide › Securing a Federated Environment

Securing a Federated Environment

This section contains the following topics:

Protecting Federated Communication

Protecting Federated Communication

Several mechanisms help secure transactions between federated partners, such as encrypting assertions and using SSL connections between partner sites.

When setting up a federated environment with SiteMinder, here are some recommendations for protecting your environment:

• Enforcing the one time use of assertions.
• Securing connections at the asserting and relying parties.
• Protecting against cross-site scripting.

These topics are described in the sections that follow.

Setting a One Time Use Condition for an Assertion

In compliance with the SAML 1.x and 2.0 specifications, SiteMinder can enforce the one time use of an assertion. By generating an assertion that is intended for one-time use, it tells the relying party not to retain the assertion for future transactions. Reusing an assertion beyond its validity results in authentication decisions that are based on out-of-date identity information.

If SiteMinder is acting as the asserting party (Producer/IdP), you can configure the one time use of an assertion. For a SAML 1.x affiliate, you can select the Set DoNotCache Condition setting. For a SAML 2.0 IdP, you can select the Set OneTimeUse Condition setting. Both of these configuration settings enable SiteMinder to insert the proper elements in an assertion that indicate the one-time use condition.

Note: Do not confuse the one time use of an assertion with the single use policy for SAML 1.x and 2.0 HTTP-POST single sign-on. The single use policy is only for POST transactions, but the one time use feature is for HTTP-Artifact and HTTP-POST.

Securing Connections Across the Federated Environment

Identity information that is sent between federated partners or a partner and an application is best protected when communication takes place over a secure connection.

Securing the Connection Between the Relying Party and the Target Application

Secure data transmission from the relying party to the client-site target application. Using a secure connection as the communication channel makes your environment less vulnerable to security attacks.

For example, an assertion can contain attributes that the relying party extracts and sends to the client application. The relying party can pass these attributes to the application using HTTP header variables or cookies. Attributes stored in headers or cookies can be overwritten at the client side, allowing a malicious user to impersonate other users. Using an SSL connection protects an environment from this type of security breach.

As a best practice, protect against this vulnerability by setting the UseSecureCookies parameter in the appropriate Agent Configuration Object (ACO). The UseSecureCookies parameter instructs Federation Web Services to generate cookies that are marked with the "secure" flag. This flag indicates that the cookie is sent only over an SSL communication channel.

Note: The ACO to modify differs depending on the setup of your federation environment. If you deploy Federation Web Services on the same system as the Web Agent is installed, edit the ACO for the Web Agent. If you deploy Federation Web Services on a different system than the Web Agent, edit the unique ACO you created for Federation Web Services.

Securing the Initial Authentication at the SiteMinder Asserting Party

The initial authentication of a user at a SiteMinder asserting party presents a potential vulnerability. When a user first authenticates to establish a user session at the asserting party, a session ID cookie is written to the browser. If the cookie is sent over a non-SSL connection, an attacker can obtain the cookie and can steal sensitive user information. The attacker can then use the information, for impersonation or identity theft.

As a best practice, protect against this vulnerability by setting the Web Agent parameter UseSecureCookies, which you can modify in the Agent Configuration Object. The UseSecureCookies parameter instructs the Web Agent to generate cookies that are marked with the "secure" flag. This flag indicates that the browser passes the cookie only over an SSL connection, which increases security. In general, establishing SSL connections for all URLs is recommended.

Protecting Against Cross-Site Scripting

A Cross Site Scripting (XSS) attack can occur when an application displays input text from a browser without filtering for characters that can form an executable script. The input text is typically data from a post or data from query parameters on a URL. The display of these characters in a browser can lead to an unwanted script being executed on the browser.

SiteMinder provides several JSPs for use with SiteMinder federation functionality. These JSPs check characters in a request to be sure that unsafe information in the output stream is not displayed in the browser.

When SiteMinder receives a federation request, the following JSPs scan the decoded values for cross-site scripting characters:

• idpdiscovery.jsp

  Used at the relying party for Identity Provider Discovery.

• linkaccount.jsp

  Used at the relying party for dynamic account linking.

• sample_application.jsp

  Used at the IDP to initiate single sign-on. You can use this sample application to direct the user to the SSO Service and then to the custom web application. Typically, you use your own application.

• signoutconfirmurl.jsp

  Used at the Account Partner for WS-Federation sign out.

• unsolicited_application.jsp

  Used for IdP-initiated single sign-on when the user is sent directly to the web application and not initially to the SSO Service.

The pages scan the request for the following characters:

Each SiteMinder-provided JSP contains a variable that defines the characters to scan. You can modify these JSPs to expand the character set.