krb5_get_creds() fetches credentials specified by
opt by first looking in the
ccache, and then it doesn't exists, fetch the credential from the KDC using the krbtgts in
ccache. The credential is returned in
out_creds and should be freed using the function
krb5_free_creds().
The structure
krb5_get_creds_opt controls the behavior of
krb5_get_creds(). The structure is opaque to consumers that can set the content of the structure with accessors functions. All accessor functions make copies of the data that is passed into accessor functions, so external consumers free the memory before calling
krb5_get_creds().
The structure
krb5_get_creds_opt is allocated with
krb5_get_creds_opt_alloc() and freed with
krb5_get_creds_opt_free(). The free function also frees the content of the structure set by the accessor functions.
krb5_get_creds_opt_add_options() and
krb5_get_creds_opt_set_options() adds and sets options to the
krb5_get_creds_opt structure . The possible options to set are
KRB5_GC_CACHED
Only check the ccache, don't got out on network to fetch credential.
KRB5_GC_USER_USER
request a user to user ticket. This options doesn't store the resulting user to user credential in the ccache.
KRB5_GC_EXPIRED_OK
returns the credential even if it is expired, default behavior is trying to refetch the credential from the KDC.
KRB5_GC_NO_STORE
Do not store the resulting credentials in the ccache.
krb5_get_creds_opt_set_enctype() sets the preferred encryption type of the application. Don't set this unless you have to since if there is no match in the KDC, the function call will fail.
krb5_get_creds_opt_set_impersonate() sets the principal to impersonate., Returns a ticket that have the impersonation principal as a client and the requestor as the service. Note that the requested principal have to be the same as the client principal in the krbtgt.
krb5_get_creds_opt_set_ticket() sets the extra ticket used in user-to-user or contrained delegation use case.