Re: [PATCH ghak90 V6 02/10] audit: add container id

On Wed, May 29, 2019 at 11:29:05AM -0400, Paul Moore wrote: > On Wed, May 29, 2019 at 10:57 AM Tycho Andersen <tycho(a)tycho.ws&gt; wrote: > > > > On Mon, Apr 08, 2019 at 11:39:09PM -0400, Richard Guy Briggs wrote: > > > It is not permitted to unset the audit container identifier. > > > A child inherits its parent's audit container identifier. > > > > ... > > > > > /** > > > + * audit_set_contid - set current task's audit contid > > > + * @contid: contid value > > > + * > > > + * Returns 0 on success, -EPERM on permission failure. > > > + * > > > + * Called (set) from fs/proc/base.c::proc_contid_write(). > > > + */ > > > +int audit_set_contid(struct task_struct *task, u64 contid) > > > +{ > > > + u64 oldcontid; > > > + int rc = 0; > > > + struct audit_buffer *ab; > > > + uid_t uid; > > > + struct tty_struct *tty; > > > + char comm[sizeof(current->comm)]; > > > + > > > + task_lock(task); > > > + /* Can't set if audit disabled */ > > > + if (!task->audit) { > > > + task_unlock(task); > > > + return -ENOPROTOOPT; > > > + } > > > + oldcontid = audit_get_contid(task); > > > + read_lock(&tasklist_lock); > > > + /* Don't allow the audit containerid to be unset */ > > > + if (!audit_contid_valid(contid)) > > > + rc = -EINVAL; > > > + /* if we don't have caps, reject */ > > > + else if (!capable(CAP_AUDIT_CONTROL)) > > > + rc = -EPERM; > > > + /* if task has children or is not single-threaded, deny */ > > > + else if (!list_empty(&task->children)) > > > + rc = -EBUSY; > > > + else if (!(thread_group_leader(task) && thread_group_empty(task))) > > > + rc = -EALREADY; > > > + read_unlock(&tasklist_lock); > > > + if (!rc) > > > + task->audit->contid = contid; > > > + task_unlock(task); > > > + > > > + if (!audit_enabled) > > > + return rc; > > > > ...but it is allowed to change it (assuming > > capable(CAP_AUDIT_CONTROL), of course)? Seems like this might be more > > immediately useful since we still live in the world of majority > > privileged containers if we didn't allow changing it, in addition to > > un-setting it. > > The idea is that only container orchestrators should be able to > set/modify the audit container ID, and since setting the audit > container ID can have a significant effect on the records captured > (and their routing to multiple daemons when we get there) modifying > the audit container ID is akin to modifying the audit configuration > which is why it is gated by CAP_AUDIT_CONTROL. The current thinking > is that you would only change the audit container ID from one > set/inherited value to another if you were nesting containers, in > which case the nested container orchestrator would need to be granted > CAP_AUDIT_CONTROL (which everyone to date seems to agree is a workable > compromise). But then don't you want some kind of ns_capable() instead (probably not the obvious one, though...)? With capable(), you can't really nest using the audit-id and user namespaces together.