Re: [RFC][PATCH 3/3] audit: Audit proc cmdline value

[William Roberts <bill.c.roberts@gmail.com>]

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The race was non existent. I had the VMA locked. I switched to this to keep
the code that gets the cmdline value almost unchanged to try and reduce
bugs. I can still author a patch on top of this later to optimize. However
the buffer is smaller. Before it was page size, now its path max....iirc is
smaller.
On Jan 14, 2014 5:45 PM, "Richard Guy Briggs" <rgb@redhat.com> wrote:

> On 14/01/06, William Roberts wrote:
> > During an audit event, cache and print the value of the process's
> > cmdline value (proc/<pid>/cmdline). This is useful in situations
> > where processes are started via fork'd virtual machines where the
> > comm field is incorrect. Often times, setting the comm field still
> > is insufficient as the comm width is not very wide and most
> > virtual machine "package names" do not fit. Also, during execution,
> > many threads have their comm field set as well. By tying it back to
> > the global cmdline value for the process, audit records will be more
> > complete in systems with these properties. An example of where this
> > is useful and applicable is in the realm of Android. With Android,
> > their is no fork/exec for VM instances. The bare, preloaded Dalvik
> > VM listens for a fork and specialize request. When this request comes
> > in, the VM forks, and the loads the specific application (specializing).
> > This was done to take advantage of COW and to not require a load of
> > basic packages by the VM on very app spawn. When this spawn occurs,
> > the package name is set via setproctitle() and shows up in procfs.
> > Many of these package names are longer then 16 bytes, the historical
> > width of task->comm. Having the cmdline in the audit records will
> > couple the application back to the record directly. Also, on my
> > Debian development box, some audit records were more useful then
> > what was printed under comm.
>
> So...  What happenned to allocating only what you need instead of the
> full 4k buffer?  Your test results showed promise with only 64 or 128
> bytes allocated.  I recall seeing some discussion about a race between
> testing for the size needed and actually filling the buffer, but was
> hoping that would be worked on rather than reverting back to the full
> 4k.
>
> > The cached cmdline is tied to the life-cycle of the audit_context
> > structure and is built on demand.
> >
> > Example denial prior to patch (Ubuntu):
> > CALL msg=audit(1387828084.070:361): arch=c000003e syscall=82 success=yes
> exit=0 a0=4184bf a1=418547 a2=0 a3=0 items=0 ppid=1 pid=1329
> auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0
> ses=4294967295 tty=(none) comm="console-kit-dae"
> exe="/usr/sbin/console-kit-daemon"
> subj=system_u:system_r:consolekit_t:s0-s0:c0.c255 key=(null)
> >
> > After Patches (Ubuntu):
> > type=SYSCALL msg=audit(1387828084.070:361): arch=c000003e syscall=82
> success=yes exit=0 a0=4184bf a1=418547 a2=0 a3=0 items=0 ppid=1 pid=1329
> auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0
> ses=4294967295 tty=(none) comm="console-kit-dae"
> exe="/usr/sbin/console-kit-daemon"
> subj=system_u:system_r:consolekit_t:s0-s0:c0.c255
> cmdline="/usr/lib/dbus-1.0/dbus-daemon-launch-helper" key=(null)
> >
> > Example denial prior to patch (Android):
> > type=1300 msg=audit(248323.940:247): arch=40000028 syscall=54 per=840000
> success=yes exit=0 a0=39 a1=540b a2=2 a3=750eecec items=0 ppid=224 pid=1858
> auid=4294967295 uid=1002 gid=1002 euid=1002 suid=1002 fsuid=1002 egid=1002
> sgid=1002 fsgid=1002 tty=(none) ses=4294967295 comm="bt_hc_worker"
> exe="/system/bin/app_process" subj=u:r:bluetooth:s0 key=(null)
> >
> > After Patches (Android):
> > type=1300 msg=audit(248323.940:247): arch=40000028 syscall=54 per=840000
> success=yes exit=0 a0=39 a1=540b a2=2 a3=750eecec items=0 ppid=224 pid=1858
> auid=4294967295 uid=1002 gid=1002 euid=1002 suid=1002 fsuid=1002 egid=1002
> sgid=1002 fsgid=1002 tty=(none) ses=4294967295 comm="bt_hc_worker"
> exe="/system/bin/app_process" cmdline="com.android.bluetooth"
> subj=u:r:bluetooth:s0 key=(null)
> >
> > Signed-off-by: William Roberts <wroberts@tresys.com>
> > ---
> >  kernel/audit.h   |    1 +
> >  kernel/auditsc.c |   32 ++++++++++++++++++++++++++++++++
> >  2 files changed, 33 insertions(+)
> >
> > diff --git a/kernel/audit.h b/kernel/audit.h
> > index b779642..bd6211f 100644
> > --- a/kernel/audit.h
> > +++ b/kernel/audit.h
> > @@ -202,6 +202,7 @@ struct audit_context {
> >               } execve;
> >       };
> >       int fds[2];
> > +     char *cmdline;
> >
> >  #if AUDIT_DEBUG
> >       int                 put_count;
> > diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> > index 90594c9..a4c2003 100644
> > --- a/kernel/auditsc.c
> > +++ b/kernel/auditsc.c
> > @@ -842,6 +842,12 @@ static inline struct audit_context
> *audit_get_context(struct task_struct *tsk,
> >       return context;
> >  }
> >
> > +static inline void audit_cmdline_free(struct audit_context *context)
> > +{
> > +     kfree(context->cmdline);
> > +     context->cmdline = NULL;
> > +}
> > +
> >  static inline void audit_free_names(struct audit_context *context)
> >  {
> >       struct audit_names *n, *next;
> > @@ -955,6 +961,7 @@ static inline void audit_free_context(struct
> audit_context *context)
> >       audit_free_aux(context);
> >       kfree(context->filterkey);
> >       kfree(context->sockaddr);
> > +     audit_cmdline_free(context);
> >       kfree(context);
> >  }
> >
> > @@ -1271,6 +1278,30 @@ static void show_special(struct audit_context
> *context, int *call_panic)
> >       audit_log_end(ab);
> >  }
> >
> > +static void audit_log_cmdline(struct audit_buffer *ab, struct
> task_struct *tsk,
> > +                      struct audit_context *context)
> > +{
> > +     int res;
> > +     char *buf;
> > +     char *msg = "(null)";
> > +     audit_log_format(ab, " cmdline=");
> > +
> > +     /* Not  cached */
> > +     if (!context->cmdline) {
> > +             buf = kmalloc(PATH_MAX, GFP_KERNEL);
> > +             if (!buf)
> > +                     goto out;
> > +             res = get_cmdline(tsk, buf, PATH_MAX);
> > +             /* Ensure NULL terminated */
> > +             if (buf[res-1] != '\0')
> > +                     buf[res-1] = '\0';
> > +             context->cmdline = buf;
> > +     }
> > +     msg = context->cmdline;
> > +out:
> > +     audit_log_untrustedstring(ab, msg);
> > +}
> > +
> >  static void audit_log_exit(struct audit_context *context, struct
> task_struct *tsk)
> >  {
> >       int i, call_panic = 0;
> > @@ -1302,6 +1333,7 @@ static void audit_log_exit(struct audit_context
> *context, struct task_struct *ts
> >                        context->name_count);
> >
> >       audit_log_task_info(ab, tsk);
> > +     audit_log_cmdline(ab, tsk, context);
> >       audit_log_key(ab, context->filterkey);
> >       audit_log_end(ab);
> >
> > --
> > 1.7.9.5
> >
> > --
> > Linux-audit mailing list
> > Linux-audit@redhat.com
> > https://www.redhat.com/mailman/listinfo/linux-audit
>
> - RGB
>
> --
> Richard Guy Briggs <rbriggs@redhat.com>
> 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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