Added two new methods to the SecurityContext interface:

public SecurityPrincipal getSecurityPrincipal();
public SecurityPrincipal[] getSecurityPrincipals();

Implemented these methods in the SAMLSecurityContext class.

The latter requires that the SAMLPrincipal class implement the SecurityContext
interface.  This was easy since the SAMLPrincipal class already has a type
member (Bug 6689).

Decreased the visibility of two methods in the SAMLSecurityContext class:

static SAMLPrincipal getSAMLPrincipal(SAMLIdentity identity);
static List getSAMLPrincipals(BasicAttribute attribute);

Developers should call the convenience methods in the SAMLIdentity class and
the BasicAttribute class instead.

All resources have been committed to CVS HEAD.  This new feature will be
distributed with GS-ST v0.5.4 (which will not be publicly released).

(In reply to comment #0)
> 
> public interface SecurityPrincipal extends Principal {
>     public String getType();
> }

The above is necessary but not sufficient.  I need the following interface:

public interface SecurityPrincipal extends IssuedSecurityItem {
    public String getName();
    public String getType();
}

This permits the following generalization in SAMLSecurityContextLogger:

SecurityPrincipal[] principals = secCtx.getSecurityPrincipals();
assert (principals != null);
for (int i = 0; i < principals.length; i++) {
    String msg = "CallerID=" + quote(callerID) +
                 " SecurityPrincipal" +
                 " ID=" + principals[i].getId() +
                 " Trusted=" +
                   (principals[i].isTrusted() ? "true" : "false") +
                 " Name=" +
                   quote(principals[i].getName()) +
                 " Type=" +
                   principals[i].getType();
    logger.info(msg);
}

This simplifies other implementations of SecurityContextLogger, and in the case
of TGSecurityContextLogger, it eliminates that implementation entirely.

Refactored the getTeraGridPrincipal method in the GatewaySecurityContext class:

http://viewcvs.globus.org/viewcvs.cgi/gridshib/saml/teragrid/java/tests/org/teragrid/ncsa/gridshib/security/GatewaySecurityContext.java?r1=1.5&r2=1.6

The above simplification, and the modification to SAMLSecurityContextLogger
described in Comment #4, was the goal of this bug (which depends on Bug 6689
and Bug 6691).  I can now move on to GridShib for GT and finish the
implementation of TeraGridGatewayPDP (Bug 6668).