Re: [RFC PATCH V1 01/12] audit: add container id

[Richard Guy Briggs]

On 2018-04-18 15:39, Stefan Berger wrote:
> On 04/18/2018 03:23 PM, Richard Guy Briggs wrote:
> > On 2018-04-18 14:45, Stefan Berger wrote:
> > > On 03/15/2018 11:58 PM, Richard Guy Briggs wrote:
> > > > On 2018-03-15 16:27, Stefan Berger wrote:
> > > > > On 03/01/2018 02:41 PM, Richard Guy Briggs wrote:
> > > > > > Implement the proc fs write to set the audit container ID of a process,
> > > > > > emitting an AUDIT_CONTAINER record to document the event.
> > > > > > 
> > > > > > This is a write from the container orchestrator task to a proc entry of
> > > > > > the form /proc/PID/containerid where PID is the process ID of the newly
> > > > > > created task that is to become the first task in a container, or an
> > > > > > additional task added to a container.
> > > > > > 
> > > > > > The write expects up to a u64 value (unset: 18446744073709551615).
> > > > > > 
> > > > > > This will produce a record such as this:
> > > > > > type=UNKNOWN[1333] msg=audit(1519903238.968:261): op=set pid=596 uid=0 subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 auid=0 tty=pts0 ses=1 opid=596 old-contid=18446744073709551615 contid=123455 res=0
> > > > > > 
> > > > > > The "op" field indicates an initial set.  The "pid" to "ses" fields are
> > > > > > the orchestrator while the "opid" field is the object's PID, the process
> > > > > > being "contained".  Old and new container ID values are given in the
> > > > > > "contid" fields, while res indicates its success.
> > > > > > 
> > > > > > It is not permitted to self-set, unset or re-set the container ID.  A
> > > > > > child inherits its parent's container ID, but then can be set only once
> > > > > > after.
> > > > > > 
> > > > > > See: https://github.com/linux-audit/audit-kernel/issues/32
> > > > > > 
> > > > > > 
> > > > > >     /* audit_rule_data supports filter rules with both integer and string
> > > > > >      * fields.  It corresponds with AUDIT_ADD_RULE, AUDIT_DEL_RULE and
> > > > > > diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> > > > > > index 4e0a4ac..0ee1e59 100644
> > > > > > --- a/kernel/auditsc.c
> > > > > > +++ b/kernel/auditsc.c
> > > > > > @@ -2073,6 +2073,92 @@ int audit_set_loginuid(kuid_t loginuid)
> > > > > >     	return rc;
> > > > > >     }
> > > > > > 
> > > > > > +static int audit_set_containerid_perm(struct task_struct *task, u64 containerid)
> > > > > > +{
> > > > > > +	struct task_struct *parent;
> > > > > > +	u64 pcontainerid, ccontainerid;
> > > > > > +	pid_t ppid;
> > > > > > +
> > > > > > +	/* Don't allow to set our own containerid */
> > > > > > +	if (current == task)
> > > > > > +		return -EPERM;
> > > > > > +	/* Don't allow the containerid to be unset */
> > > > > > +	if (!cid_valid(containerid))
> > > > > > +		return -EINVAL;
> > > > > > +	/* if we don't have caps, reject */
> > > > > > +	if (!capable(CAP_AUDIT_CONTROL))
> > > > > > +		return -EPERM;
> > > > > > +	/* if containerid is unset, allow */
> > > > > > +	if (!audit_containerid_set(task))
> > > > > > +		return 0;
> > > > > I am wondering whether there should be a check for the target process that
> > > > > will receive the containerid to not have CAP_SYS_ADMIN that would otherwise
> > > > > allow it to arbitrarily unshare()/clone() and leave the set of namespaces
> > > > > that may make up the container whose containerid we assign here?
> > > > This is a reasonable question.  This has been debated and I understood
> > > > the conclusion was that without a clear definition of a "container", the
> > > > task still remains in that container that just now has more
> > > > sub-namespaces (in the case of hierarchical namespaces), we don't want
> > > > to restrict it in such a way and that allows it to create nested
> > > > containers.  I see setns being more problematic if it could switch to
> > > > another existing namespace that was set up by the orchestrator for a
> > > > different container.  The coming v2 patchset acknowledges this situation
> > > > with the network namespace being potentially shared by multiple
> > > > containers.
> > > Are you going to post v2 soon? We would like to build on top of it for IMA
> > > namespacing and auditing inside of IMA namespaces.
> > I don't know if it addresses your specific needs, but V2 was posted on
> > March 16th along with userspace patches:
> > 	https://www.redhat.com/archives/linux-audit/2018-March/msg00110.html
> > 	https://www.redhat.com/archives/linux-audit/2018-March/msg00124.html
> > 
> > V3 is pending.
> Thanks. I hadn't actually looked at primarily due to the ghak and ghau in
> the title. Whatever these may mean.

They are Github issue numbers:
GHAK: GitHub Audit Kernel
GHAU: GitHub Audit Userspace
GHAD: GitHub Audit Documentation
GHAT: GitHub Audit Testsuite

> Does V2 or will V3 prevent a privileged process to setns() to a whole
> different set of namespaces and still be audited with that initial container
> id ?

No, not significantly different from V1 in that respect.

It does not prevent setns(), but will maintain its containerid.

It will prevent games by blocking a child and parent from setting each
other's containerids.

It does check that the task being conainered does not yet have any
children or peer threads.

- RGB

--
Richard Guy Briggs <rgb@xxxxxxxxxx>
Sr. S/W Engineer, Kernel Security, Base Operating Systems
Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
Voice: +1.647.777.2635, Internal: (81) 32635