k5_size_checksum
k5_size_checksum(krb5_checksum *checksum, size_t *sizep);
kret = k5_size_checksum(authenticator->checksum, &required);
if (!k5_size_checksum(checksum, &required) && required <= remain) {
check(k5_size_checksum(cksum, &elen));
check(k5_size_checksum(cksum2, &elen2));