This routine allows an application to acquire a handle for
a pre-existing credential by name. GSSAPI implementations must
impose a local access-control policy on callers of this routine
to prevent unauthorized callers from acquiring credentials to which
they are not entitled. This routine is not intended to provide
a "login to the network" function, as such a function would result
in the creation of new credentials rather than merely acquiring
a handle to existing credentials.
If desired_name is GSS_C_NO_NAME, the call is interpreted
as a request for a credential handle that will invoke default behavior
when passed to gss_init_sec_context (if
cred_usage is GSS_C_INITIATE or GSS_C_BOTH) or gss_accept_sec_context (if
cred_usage is GSS_C_ACCEPT or GSS_C_BOTH).
This routine is expected to be used primarily by context acceptors.