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Date:   Sat, 30 Mar 2019 08:55:36 -0400
From:   Richard Guy Briggs <rgb@...hat.com>
To:     Ondrej Mosnacek <omosnace@...hat.com>
Cc:     containers@...ts.linux-foundation.org, linux-api@...r.kernel.org,
        Linux-Audit Mailing List <linux-audit@...hat.com>,
        linux-fsdevel@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        netdev@...r.kernel.org, netfilter-devel@...r.kernel.org,
        Paul Moore <paul@...l-moore.com>,
        Steve Grubb <sgrubb@...hat.com>,
        David Howells <dhowells@...hat.com>,
        Simo Sorce <simo@...hat.com>,
        Eric Paris <eparis@...isplace.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        "Eric W . Biederman" <ebiederm@...ssion.com>, nhorman@...driver.com
Subject: Re: [PATCH ghak90 V5 05/10] audit: add containerid support for
 ptrace and signals

On 2019-03-27 22:04, Richard Guy Briggs wrote:
> On 2019-03-27 22:17, Ondrej Mosnacek wrote:
> > On Fri, Mar 15, 2019 at 7:34 PM Richard Guy Briggs <rgb@...hat.com> wrote:
> > > Add audit container identifier support to ptrace and signals.  In
> > > particular, the "ref" field provides a way to label the auxiliary record
> > > to which it is associated.
> > >
> > > Signed-off-by: Richard Guy Briggs <rgb@...hat.com>
> > > Acked-by: Serge Hallyn <serge@...lyn.com>
> > > Signed-off-by: Richard Guy Briggs <rgb@...hat.com>
> > > ---
> > >  include/linux/audit.h |  1 +
> > >  kernel/audit.c        |  2 ++
> > >  kernel/audit.h        |  2 ++
> > >  kernel/auditsc.c      | 23 +++++++++++++++++------
> > >  4 files changed, 22 insertions(+), 6 deletions(-)
> > >
> > > diff --git a/include/linux/audit.h b/include/linux/audit.h
> > > index 43438192ca2a..ebd6625ca80e 100644
> > > --- a/include/linux/audit.h
> > > +++ b/include/linux/audit.h
> > > @@ -35,6 +35,7 @@ struct audit_sig_info {
> > >         uid_t           uid;
> > >         pid_t           pid;
> > >         char            ctx[0];
> > > +       u64             cid;
> > >  };
> > 
> > It seems like this structure implicitly defines the format of some
> > message that is sent to userspace... If so, how will userspace detect
> > that a new format (including the cid) is being used? Even assuming the
> > fixed order as pointed out by Neil, the message still seems to be
> > variable-sized so userspace cannot even use the length to infer that.
> > Am I missing something here? (I hope I am :)
> 
> How humble of you again.  No, you're not missing something.  This ends
> up being an api change...  That can be fixed in userspace by checking
> for AUDIT_FEATURE_BITMAP_CONTAINERID, but how do we make a newer kernel
> not break an older userspace...  I think this was the original rationale
> for adding it after the ctx but totally missing the fact that the latter
> is a variable-length field.

The way to address this on Steve Grubb's advice is to create a new
message type that incorporates a new struct with the structure above,
leaving the old one with the old message type deprecated.  I've coded
this up along with userspace support.

> This patch really should be split into audit_sig_cid changes in a patch
> by itself and target_cid changes which could go with the second and
> fourth patches.

I've also done this which Paul had already asked for, not quite in this
form.

I believe this addresses all the outstanding issues.

> > >  struct audit_buffer;
> > > diff --git a/kernel/audit.c b/kernel/audit.c
> > > index 8cc0e88d7f2a..cfa659b3f6c4 100644
> > > --- a/kernel/audit.c
> > > +++ b/kernel/audit.c
> > > @@ -138,6 +138,7 @@ struct audit_net {
> > >  kuid_t         audit_sig_uid = INVALID_UID;
> > >  pid_t          audit_sig_pid = -1;
> > >  u32            audit_sig_sid = 0;
> > > +u64            audit_sig_cid = AUDIT_CID_UNSET;
> > >
> > >  /* Records can be lost in several ways:
> > >     0) [suppressed in audit_alloc]
> > > @@ -1515,6 +1516,7 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
> > >                         memcpy(sig_data->ctx, ctx, len);
> > >                         security_release_secctx(ctx, len);
> > >                 }
> > > +               sig_data->cid = audit_sig_cid;
> > >                 audit_send_reply(skb, seq, AUDIT_SIGNAL_INFO, 0, 0,
> > >                                  sig_data, sizeof(*sig_data) + len);
> > >                 kfree(sig_data);
> > > diff --git a/kernel/audit.h b/kernel/audit.h
> > > index c00e2ee3c6b3..c5ac6436317e 100644
> > > --- a/kernel/audit.h
> > > +++ b/kernel/audit.h
> > > @@ -148,6 +148,7 @@ struct audit_context {
> > >         kuid_t              target_uid;
> > >         unsigned int        target_sessionid;
> > >         u32                 target_sid;
> > > +       u64                 target_cid;
> > >         char                target_comm[TASK_COMM_LEN];
> > >
> > >         struct audit_tree_refs *trees, *first_trees;
> > > @@ -344,6 +345,7 @@ extern void audit_filter_inodes(struct task_struct *tsk,
> > >  extern pid_t audit_sig_pid;
> > >  extern kuid_t audit_sig_uid;
> > >  extern u32 audit_sig_sid;
> > > +extern u64 audit_sig_cid;
> > >
> > >  extern int audit_filter(int msgtype, unsigned int listtype);
> > >
> > > diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> > > index a8c8b44b954d..f04e115df5dc 100644
> > > --- a/kernel/auditsc.c
> > > +++ b/kernel/auditsc.c
> > > @@ -113,6 +113,7 @@ struct audit_aux_data_pids {
> > >         kuid_t                  target_uid[AUDIT_AUX_PIDS];
> > >         unsigned int            target_sessionid[AUDIT_AUX_PIDS];
> > >         u32                     target_sid[AUDIT_AUX_PIDS];
> > > +       u64                     target_cid[AUDIT_AUX_PIDS];
> > >         char                    target_comm[AUDIT_AUX_PIDS][TASK_COMM_LEN];
> > >         int                     pid_count;
> > >  };
> > > @@ -1514,7 +1515,7 @@ static void audit_log_exit(void)
> > >         for (aux = context->aux_pids; aux; aux = aux->next) {
> > >                 struct audit_aux_data_pids *axs = (void *)aux;
> > >
> > > -               for (i = 0; i < axs->pid_count; i++)
> > > +               for (i = 0; i < axs->pid_count; i++) {
> > >                         if (audit_log_pid_context(context, axs->target_pid[i],
> > >                                                   axs->target_auid[i],
> > >                                                   axs->target_uid[i],
> > > @@ -1522,14 +1523,20 @@ static void audit_log_exit(void)
> > >                                                   axs->target_sid[i],
> > >                                                   axs->target_comm[i]))
> > >                                 call_panic = 1;
> > > +                       audit_log_contid(context, axs->target_cid[i]);
> > > +               }
> > >         }
> > >
> > > -       if (context->target_pid &&
> > > -           audit_log_pid_context(context, context->target_pid,
> > > -                                 context->target_auid, context->target_uid,
> > > -                                 context->target_sessionid,
> > > -                                 context->target_sid, context->target_comm))
> > > +       if (context->target_pid) {
> > > +               if (audit_log_pid_context(context, context->target_pid,
> > > +                                         context->target_auid,
> > > +                                         context->target_uid,
> > > +                                         context->target_sessionid,
> > > +                                         context->target_sid,
> > > +                                         context->target_comm))
> > >                         call_panic = 1;
> > > +               audit_log_contid(context, context->target_cid);
> > > +       }
> > >
> > >         if (context->pwd.dentry && context->pwd.mnt) {
> > >                 ab = audit_log_start(context, GFP_KERNEL, AUDIT_CWD);
> > > @@ -2360,6 +2367,7 @@ void __audit_ptrace(struct task_struct *t)
> > >         context->target_uid = task_uid(t);
> > >         context->target_sessionid = audit_get_sessionid(t);
> > >         security_task_getsecid(t, &context->target_sid);
> > > +       context->target_cid = audit_get_contid(t);
> > >         memcpy(context->target_comm, t->comm, TASK_COMM_LEN);
> > >  }
> > >
> > > @@ -2387,6 +2395,7 @@ int audit_signal_info(int sig, struct task_struct *t)
> > >                 else
> > >                         audit_sig_uid = uid;
> > >                 security_task_getsecid(current, &audit_sig_sid);
> > > +               audit_sig_cid = audit_get_contid(current);
> > >         }
> > >
> > >         if (!audit_signals || audit_dummy_context())
> > > @@ -2400,6 +2409,7 @@ int audit_signal_info(int sig, struct task_struct *t)
> > >                 ctx->target_uid = t_uid;
> > >                 ctx->target_sessionid = audit_get_sessionid(t);
> > >                 security_task_getsecid(t, &ctx->target_sid);
> > > +               ctx->target_cid = audit_get_contid(t);
> > >                 memcpy(ctx->target_comm, t->comm, TASK_COMM_LEN);
> > >                 return 0;
> > >         }
> > > @@ -2421,6 +2431,7 @@ int audit_signal_info(int sig, struct task_struct *t)
> > >         axp->target_uid[axp->pid_count] = t_uid;
> > >         axp->target_sessionid[axp->pid_count] = audit_get_sessionid(t);
> > >         security_task_getsecid(t, &axp->target_sid[axp->pid_count]);
> > > +       axp->target_cid[axp->pid_count] = audit_get_contid(t);
> > >         memcpy(axp->target_comm[axp->pid_count], t->comm, TASK_COMM_LEN);
> > >         axp->pid_count++;
> > >
> > 
> > Ondrej Mosnacek <omosnace at redhat dot com>
> 
> - RGB

- RGB

--
Richard Guy Briggs <rgb@...hat.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

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