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During the execution of a BrowserProfile, when the user authenticates at the SSO service, the IdentityProvider typically issues the user a special type of NameIdentifier called a ShibHandle in conjunction with the authentication assertion.  At that point, the !IdP may cache the identifier so it can subsequently map that identifier to the actual principal upon request.

In Shibboleth, the identifier and the principal are represented by objects of type  {{SAMLNameIdentifier}}  and  {{LocalPrincipal}} , respectively:

{code}
import org.opensaml.SAMLNameIdentifier;
import edu.internet2.middleware.shibboleth.common.LocalPrincipal;
{code}

 {{SAMLNameIdentifier}}  is an OpenSAML construct while  {{LocalPrincipal}}  implements  {{java.security.Principal}} .  As users enter and leave the system, a one-to-one correspondence between  {{SAMLNameIdentifier}}  and  {{LocalPrincipal}}  is maintained by the !IdP.

h2. Interface  {{NameIdentifierMapping}} 

Shibboleth's code handling of this mapping is based on the  {{NameIdentifierMapping}}  interface:

{code}
package edu.internet2.middleware.shibboleth.common;
public interface NameIdentifierMapping {
  public String getId();
  public URI getNameIdentifierFormat();
  public LocalPrincipal getPrincipal(SAMLNameIdentifier nameId, ServiceProvider sp, IdentityProvider idp);
  public SAMLNameIdentifier getNameIdentifier(LocalPrincipal principal, ServiceProvider sp, IdentityProvider idp);
  public void destroy();
}
{code}

The primary methods of the interface are  {{getPrincipal}}  and  {{getNameIdentifier}} , which represent the desired mapping between  {{LocalPrincipal}}  and  {{SAMLNameIdentifier}} .

h2. Class  {{BaseNameIdentifierMapping}} 

The abstract class  {{BaseNameIdentifierMapping}}  is the superclass of all implementations of the  {{NameIdentifierMapping}}  interface:

{code}
package edu.internet2.middleware.shibboleth.common.provider;
public abstract class BaseNameIdentifierMapping implements NameIdentifierMapping;
{code}

 {{BaseNameIdentifierMapping}}  implements methods  {{getId}}  and  {{getNameIdentifierFormat}}  \(which correspond to a pair of configuration options\) but does not implement the methods  {{getPrincipal}}  and  {{getNameIdentifier}}  \(which are left to subclasses\).

h2. Class  {{PrincipalNameIdentifier}} 

The simplest implementation of  {{NameIdentifierMapping}}  is  {{PrincipalNameIdentifier}} , which maps the value of the  {{<saml:NameIdentifier>}}  element directly to a local principal of the same name.

{code}
package edu.internet2.middleware.shibboleth.common.provider;
public class PrincipalNameIdentifier extends BaseNameIdentifierMapping;
{code}

The  {{PrincipalNameIdentifier}}  mapping is used whenever the principal name and the value of the  {{<saml:NameIdentifier>}}  element are identical.

h2. Class  {{X509SubjectNameNameIdentifierMapping}} 

Another implementation of  {{NameIdentifierMapping}}  called  {{X509SubjectNameNameIdentifierMapping}}  was originally developed for e-authentication conformance testing:

{code}
package edu.internet2.middleware.shibboleth.common.provider;
public class X509SubjectNameNameIdentifierMapping extends BaseNameIdentifierMapping implements NameIdentifierMapping;
{code}

 {{X509SubjectNameNameIdentifierMapping}}  assumes the principal name is embedded in the DN.  In the  {{getPrincipal}}  method, the principal name is extracted from the DN by regular expression matching.

h2. Class  {{AQHNameIdentifierMapping}} 

Neither  {{PrincipalNameIdentifier}}  nor  {{X509SubjectNameNameIdentifierMapping}}  are very desirable in practice since they provide no privacy.  To ensure privacy, an opaque identifier called a ShibHandle is used.  Shibboleth handles are transient, that is, they have a relatively short lifetime.  The lifetime of a Shibboleth handle is governed by a configuration option called  {{handleTTL}}  \(handle time-to-live\), which is a member of the abstract class  {{AQHNameIdentifierMapping}} :

{code}
package edu.internet2.middleware.shibboleth.common.provider;
public abstract class AQHNameIdentifierMapping extends BaseNameIdentifierMapping;
{code}

Two important classes \( {{SharedMemoryShibHandle}}  and  {{CryptoShibHandle=\) extend =AQHNameIdentifierMapping}} .

h2. Class  {{SharedMemoryShibHandle}} 

The default implementation of  {{NameIdentifierMapping}}  is called  {{SharedMemoryShibHandle}} :

{code}
package edu.internet2.middleware.shibboleth.common.provider;
public class SharedMemoryShibHandle extends AQHNameIdentifierMapping implements NameIdentifierMapping;
{code}

 {{SharedMemoryShibHandle}} , the Shibboleth workhorse implementation of  {{NameIdentifierMapping}} , defines a memory cache that is maintained as handles are generated or expired.

h2. Class  {{CryptoShibHandle}} 

The most complicated implementation of  {{NameIdentifierMapping}}  is called  {{CryptoShibHandle}} :

{code}
package edu.internet2.middleware.shibboleth.common.provider;
public class CryptoShibHandle extends AQHNameIdentifierMapping implements NameIdentifierMapping;
{code}

 {{CryptoShibHandle}}  concatenates an initialization vector, an HMAC, an expiration time, and a principal name, which is then encrypted, encoded and inserted into the  {{<saml:NameIdentifier>}}  element.  \(On the surface, an instance of  {{CryptoShibHandle}}  looks just like an ordinary ShibHandle.\)  Later the AA decodes and decrypts the value of the  {{<saml:NameIdentifier>}}  element to recover the principal name.  No caching is required in this case.

 {{CryptoShibHandle}}  presupposes a number of configuration options:

*  {{KeyStorePath}}  \(required\)
*  {{KeyStorePassword}}  \(required\)
*  {{KeyStoreKeyAlias}}  \(required\)
*  {{KeyStoreKeyPassword}}  \(required\)
*  {{KeyStoreType}}  \(optional\)
*  {{Cipher}}  \(optional\)
*  {{MAC}}  \(optional\)

Reasonable defaults are provided for the optional config options listed above.

h2. Class  {{NameMapper}} 

 {{NameMapper}}  incorporates all of the above \(except =X509SubjectNameNameIdentifierMapping=\) to produce a fully functional implementation:

{code}
package edu.internet2.middleware.shibboleth.common;
public class NameMapper;
{code}
							
 {{NameMapper}}  loads a default NameMapping element \(if no such element is defined in the !IdP config file idp.xml\).  The default mapping is  {{SharedMemoryShibHandle}}  with  {{handleTTL}}  set to 1800 seconds.

 {{NameMapper}}  defines two new configuration options called  {{type}}  and  {{class}} .  Each NameMapping element in idp.xml must have exactly one of the  {{type}}  or  {{class}}  attributes.  A  {{type}}  attribute refers to one of the three aliases \(described below\).  A  {{class}}  attribute is the fully qualified class name of an implementation of  {{NameIdentifierMapping}} .

The  {{NameMapper}}  class pre-registers three mappings:

{html}<table>{html}
  {html}<tr>{html}
	 {html}<th align="left">{html}Alias{html}</th>{html}
	 {html}<th align="left">{html}Class{html}</th>{html}
  {html}</tr>{html}
  {html}<tr>{html}
	 {html}<td align="left">{html}{html}<tt>{html}CryptoHandleGenerator{html}</tt>{html}{html}</td>{html}
	 {html}<td align="left">{html}{html}<tt>{html}edu.internet2.middleware.shibboleth.common.provider.CryptoShibHandle{html}</tt>{html}{html}</td>{html}
  {html}</tr>{html}
  {html}<tr>{html}
	 {html}<td align="left">{html}{html}<tt>{html}SharedMemoryShibHandle{html}</tt>{html}{html}</td>{html}
	 {html}<td align="left">{html}{html}<tt>{html}edu.internet2.middleware.shibboleth.common.provider.SharedMemoryShibHandle{html}</tt>{html}{html}</td>{html}
  {html}</tr>{html}
  {html}<tr>{html}
	 {html}<td align="left">{html}{html}<tt>{html}Principal{html}</tt>{html}{html}</td>{html}
	 {html}<td align="left">{html}{html}<tt>{html}edu.internet2.middleware.shibboleth.common.provider.PrincipalNameIdentifier{html}</tt>{html}{html}</td>{html}
  {html}</tr>{html}
{html}</table>{html}

One of the above aliases is used as the value of the  {{type}}  attribute in a NameMapping element.

-\- Main.TomScavo \- 23 Mar 2005