illumos-gate: Missing authorization in illumos ipmgmtd allows local users to change persistent IPMP group membership

A missing authorization check in the illumos IP management daemon (ipmgmtd) allows a local user to change the persistent IP multipathing (IPMP) configuration. The ipmgmtd door dispatch table in usr/src/cmd/cmd-inet/lib/ipmgmtd/ipmgmt_door.c does not require the solaris.network.interface.config authorization for the IPMGMT_CMD_IPMP_UPDATE command, although its handler, ipmgmt_ipmp_update_handler(), writes to the persistent ipadm configuration when the IPMGMT_PERSIST flag is set. An unprivileged local user can therefore add interfaces to, or remove them from, existing IPMP groups in the stored configuration. The running configuration is not changed; the modification takes effect when the stored configuration is next applied, such as at boot, and may disrupt network connectivity. The flaw has existed since 2021 (illumos-gate commit a73be61a), and affects any illumos distribution prior to illumos-gate commit e8d3efa1.