Re: [PATCH ghak90 (was ghak32) V4 03/10] audit: log container info of syscalls

[Richard Guy Briggs <rgb@redhat.com>]

On 2018-10-24 16:55, Paul Moore wrote:
> On Wed, Oct 24, 2018 at 11:15 AM Richard Guy Briggs <rgb@redhat.com> wrote:
> > On 2018-10-19 19:16, Paul Moore wrote:
> > > On Sun, Aug 5, 2018 at 4:32 AM Richard Guy Briggs <rgb@redhat.com> wrote:
> > > > Create a new audit record AUDIT_CONTAINER to document the audit
> > > > container identifier of a process if it is present.
> > > >
> > > > Called from audit_log_exit(), syscalls are covered.
> > > >
> > > > A sample raw event:
> > > > type=SYSCALL msg=audit(1519924845.499:257): arch=c000003e syscall=257 success=yes exit=3 a0=ffffff9c a1=56374e1cef30 a2=241 a3=1b6 items=2 ppid=606 pid=635 auid=0 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=pts0 ses=3 comm="bash" exe="/usr/bin/bash" subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 key="tmpcontainerid"
> > > > type=CWD msg=audit(1519924845.499:257): cwd="/root"
> > > > type=PATH msg=audit(1519924845.499:257): item=0 name="/tmp/" inode=13863 dev=00:27 mode=041777 ouid=0 ogid=0 rdev=00:00 obj=system_u:object_r:tmp_t:s0 nametype= PARENT cap_fp=0000000000000000 cap_fi=0000000000000000 cap_fe=0 cap_fver=0
> > > > type=PATH msg=audit(1519924845.499:257): item=1 name="/tmp/tmpcontainerid" inode=17729 dev=00:27 mode=0100644 ouid=0 ogid=0 rdev=00:00 obj=unconfined_u:object_r:user_tmp_t:s0 nametype=CREATE cap_fp=0000000000000000 cap_fi=0000000000000000 cap_fe=0 cap_fver=0
> > > > type=PROCTITLE msg=audit(1519924845.499:257): proctitle=62617368002D6300736C65657020313B206563686F2074657374203E202F746D702F746D70636F6E7461696E65726964
> > > > type=CONTAINER msg=audit(1519924845.499:257): op=task contid=123458
> > > >
> > > > See: https://github.com/linux-audit/audit-kernel/issues/90
> > > > See: https://github.com/linux-audit/audit-userspace/issues/51
> > > > See: https://github.com/linux-audit/audit-testsuite/issues/64
> > > > See: https://github.com/linux-audit/audit-kernel/wiki/RFE-Audit-Container-ID
> > > > Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
> > > > Acked-by: Serge Hallyn <serge@hallyn.com>
> > > > Acked-by: Steve Grubb <sgrubb@redhat.com>
> > > > ---
> > > >  include/linux/audit.h      |  7 +++++++
> > > >  include/uapi/linux/audit.h |  1 +
> > > >  kernel/audit.c             | 24 ++++++++++++++++++++++++
> > > >  kernel/auditsc.c           |  3 +++
> > > >  4 files changed, 35 insertions(+)
> > >
> > > ...
> > >
> > > > @@ -2045,6 +2045,30 @@ void audit_log_session_info(struct audit_buffer *ab)
> > > >         audit_log_format(ab, " auid=%u ses=%u", auid, sessionid);
> > > >  }
> > > >
> > > > +/*
> > > > + * audit_log_contid - report container info
> > > > + * @tsk: task to be recorded
> > > > + * @context: task or local context for record
> > > > + * @op: contid string description
> > > > + */
> > > > +int audit_log_contid(struct task_struct *tsk,
> > > > +                            struct audit_context *context, char *op)
> > > > +{
> > > > +       struct audit_buffer *ab;
> > > > +
> > > > +       if (!audit_contid_set(tsk))
> > > > +               return 0;
> > > > +       /* Generate AUDIT_CONTAINER record with container ID */
> > > > +       ab = audit_log_start(context, GFP_KERNEL, AUDIT_CONTAINER);
> > > > +       if (!ab)
> > > > +               return -ENOMEM;
> > > > +       audit_log_format(ab, "op=%s contid=%llu",
> > > > +                        op, audit_get_contid(tsk));
> > > > +       audit_log_end(ab);
> > > > +       return 0;
> > > > +}
> > > > +EXPORT_SYMBOL(audit_log_contid);
> > >
> > > As discussed in the previous iteration of the patch, I prefer
> > > AUDIT_CONTAINER_ID here over AUDIT_CONTAINER.  If you feel strongly
> > > about keeping it as-is with AUDIT_CONTAINER I suppose I could live
> > > with that, but it is isn't my first choice.
> >
> > I don't have a strong opinion on this one, mildly preferring the shorter
> > one only because it is shorter.
> 
> We already have multiple AUDIT_CONTAINER* record types, so it seems as
> though we should use "AUDIT_CONTAINER" as a prefix of sorts, rather
> than a type itself.

I'm fine with that.  I'd still like to hear Steve's input.  He had
stronger opinions than me.

> > > However, I do care about the "op" field in this record.  It just
> > > doesn't make any sense; the way you are using it it is more of a
> > > context field than an operations field, and even then why is the
> > > context important from a logging and/or security perspective?  Drop it
> > > please.
> >
> > I'll rename it to whatever you like.  I'd suggest "ref=".  The reason I
> > think it is important is there are multiple sources that aren't always
> > obvious from the other records to which it is associated.  In the case
> > of ptrace and signals, there can be many target tasks listed (OBJ_PID)
> > with no other way to distinguish the matching audit container identifier
> > records all for one event.  This is in addition to the default syscall
> > container identifier record.  I'm not currently happy with the text
> > content to link the two, but that should be solvable (most obvious is
> > taret PID).  Throwing away this information seems shortsighted.
> 
> It would be helpful if you could generate real audit events
> demonstrating the problems you are describing, as well as a more
> standard syscall event, so we can discuss some possible solutions.

If the auditted process is in a container and it ptraces or signals
another process in a container, there will be two AUDIT_CONTAINER
records for the same event that won't be identified as to which record
belongs to which process or other record (SYSCALL vs 1+ OBJ_PID
records).  There could be many signals recorded, each with their own
OBJ_PID record.  The first is stored in the audit context and additional
ones are stored in a chained struct that can accommodate 16 entries each.

(See audit_signal_info(), __audit_ptrace().)

(As a side note, on code inspection it appears that a signal target
would get overwritten by a ptrace action if they were to happen in that
order.)

> paul moore

- RGB

--
Richard Guy Briggs <rgb@redhat.com>
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