Re: [PATCH 0/2] namespaces: log namespaces per task

[Richard Guy Briggs]

On 14/05/02, Serge E. Hallyn wrote:
> Quoting Richard Guy Briggs (rgb@xxxxxxxxxx):
> > I saw no replies to my questions when I replied a year after Aris' posting, so
> > I don't know if it was ignored or got lost in stale threads:
> >         https://www.redhat.com/archives/linux-audit/2013-March/msg00020.html
> >         https://www.redhat.com/archives/linux-audit/2013-March/msg00033.html
> > 	(https://lists.linux-foundation.org/pipermail/containers/2013-March/032063.html)
> >         https://www.redhat.com/archives/linux-audit/2014-January/msg00180.html
> > 
> > I've tried to answer a number of questions that were raised in that thread.
> > 
> > The goal is not quite identical to Aris' patchset.
> > 
> > The purpose is to track namespaces in use by logged processes from the
> > perspective of init_*_ns.  The first patch defines a function to list them.
> > The second patch provides an example of usage for audit_log_task_info() which
> > is used by syscall audits, among others.  audit_log_task() and
> > audit_common_recv_message() would be other potential use cases.
> > 
> > Use a serial number per namespace (unique across one boot of one kernel)
> > instead of the inode number (which is claimed to have had the right to change
> > reserved and is not necessarily unique if there is more than one proc fs).  It
> > could be argued that the inode numbers have now become a defacto interface and
> > can't change now, but I'm proposing this approach to see if this helps address
> > some of the objections to the earlier patchset.
> > 
> > There could also have messages added to track the creation and the destruction
> > of namespaces, listing the parent for hierarchical namespaces such as pidns,
> > userns, and listing other ids for non-hierarchical namespaces, as well as other
> > information to help identify a namespace.
> > 
> > There has been some progress made for audit in net namespaces and pid
> > namespaces since this previous thread.  net namespaces are now served as peers
> > by one auditd in the init_net namespace with processes in a non-init_net
> > namespace being able to write records if they are in the init_user_ns and have
> > CAP_AUDIT_WRITE.  Processes in a non-init_pid_ns can now similarly write
> > records.  As for CAP_AUDIT_READ, I just posted a patchset to check capabilities
> > of userspace processes that try to join netlink broadcast groups.
> > 
> > 
> > Questions:
> > Is there a way to link serial numbers of namespaces involved in migration of a
> > container to another kernel?  (I had a brief look at CRIU.)  Is there a unique
> > identifier for each running instance of a kernel?  Or at least some identifier
> > within the container migration realm?
> 
> Eric Biederman has always been adamantly opposed to adding new namespaces
> of namespaces, so the fact that you're asking this question concerns me.

I have seen that position and I don't fully understand the justification
for it other than added complexity.

One way that occured to me to be able to identify a kernel instance was
to look at CPU serial numbers or other CPU entity intended to be
globally unique, but that isn't universally available.

Another possibility was RTC reading at time of boot, but that isn't good
enough either.

Both are dubious in VMs anyways.

> The way things are right now, since audit belongs to the init userns,
> we can get away with saying if a container 'migrates', the new kernel
> will see a different set of serials, and noone should care.  However,
> if we're going to be allowing containers to have their own audit
> namespace/layer/whatever, then this becomes more of a concern.

Having a container have its own audit daemon (partitionned appropriately
in the kernel) would be a long-term goal.

> That said, I'll now look at the patches while pretending that problem
> does not exist :)  If I ack, it'll be on correctness of the code, but
> we'll still have to deal with this issue.

Getting some discussion about this migration challenge was a significant
motivation for posting this patch, so I'm hoping others will weigh in.

Thanks for your review, Serge.

> > What additional events should list this information?
> > 
> > Does this present any kind of information leak?  Only CAP_AUDIT_CONTROL (and
> > proposed CAP_AUDIT_READ) in init_user_ns can get to this information in the
> > init namespace at the moment.
> > 
> > 
> > Proposed output format:
> > This differs slightly from Aristeu's patch because of the label conflict with
> > "pid=" due to including it in existing records rather than it being a seperate
> > record:
> >         type=SYSCALL msg=audit(1398112249.996:65): arch=c000003e syscall=272 success=yes exit=0 a0=40000000 a1=ffffffffffffffff a2=0 a3=22 items=0 ppid=1 pid=566 auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=(none) ses=4294967295 comm="(t-daemon)" exe="/usr/lib/systemd/systemd" mntns=5 netns=97 utsns=2 ipcns=1 pidns=4 userns=3 subj=system_u:system_r:init_t:s0 key=(null)
> > 
> > 
> > Note: This set does not try to solve the non-init namespace audit messages and
> > auditd problem yet.  That will come later, likely with additional auditd
> > instances running in another namespace with a limited ability to influence the
> > master auditd.  I echo Eric B's idea that messages destined for different
> > namespaces would have to be tailored for that namespace with references that
> > make sense (such as the right pid number reported to that pid namespace, and
> > not leaking info about parents or peers).
> > 
> > 
> > Richard Guy Briggs (2):
> >   namespaces: give each namespace a serial number
> >   audit: log namespace serial numbers
> > 
> >  fs/mount.h                     |    1 +
> >  fs/namespace.c                 |    1 +
> >  include/linux/audit.h          |    7 +++++++
> >  include/linux/ipc_namespace.h  |    1 +
> >  include/linux/nsproxy.h        |    8 ++++++++
> >  include/linux/pid_namespace.h  |    1 +
> >  include/linux/user_namespace.h |    1 +
> >  include/linux/utsname.h        |    1 +
> >  include/net/net_namespace.h    |    1 +
> >  init/version.c                 |    1 +
> >  ipc/msgutil.c                  |    1 +
> >  ipc/namespace.c                |    2 ++
> >  kernel/audit.c                 |   38 ++++++++++++++++++++++++++++++++++++++
> >  kernel/nsproxy.c               |   24 ++++++++++++++++++++++++
> >  kernel/pid.c                   |    1 +
> >  kernel/pid_namespace.c         |    2 ++
> >  kernel/user.c                  |    1 +
> >  kernel/user_namespace.c        |    2 ++
> >  kernel/utsname.c               |    2 ++
> >  net/core/net_namespace.c       |    4 +++-
> >  20 files changed, 99 insertions(+), 1 deletions(-)
> > 
> > _______________________________________________
> > Containers mailing list
> > Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx
> > https://lists.linuxfoundation.org/mailman/listinfo/containers

- RGB

--
Richard Guy Briggs <rbriggs@xxxxxxxxxx>
Senior Software Engineer, Kernel Security, AMER ENG Base Operating Systems, Red Hat
Remote, Ottawa, Canada
Voice: +1.647.777.2635, Internal: (81) 32635, Alt: +1.613.693.0684x3545
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