[PATCH v17 20/23] Audit: Add a new record for multiple subject LSM attributes

[Stephen Smalley]

On Thu, May 14, 2020 at 7:30 PM Casey Schaufler <casey at schaufler-ca.com> wrote:
>
> Create a new audit record type to contain the subject information
> when there are multiple security modules that require such data.
> This record is emitted before the other records for the event, but
> is linked with the same timestamp and serial number.
>
> Reviewed-by: Kees Cook <keescook at chromium.org>
> Signed-off-by: Casey Schaufler <casey at schaufler-ca.com>
> Cc: linux-audit at redhat.com
> ---

With this patch, I see userspace audit records like this one:

type=SYSTEM_BOOT msg=audit(1589816792.181:103): pid=789 uid=0
auid=4294967295 ses=4294967295 subj=? subj=system_u:system_r:init_t:s0
msg=' comm="systemd-update-utmp"
exe="/usr/lib/systemd/systemd-update-utmp" hostname=? addr=?
terminal=? res=success'

I'm guessing that userspace is appending the second subj= field when
it sees subj=? or otherwise is missing subj= information?

Then we have kernel audit records like this:

type=PROCTITLE msg=audit(1589816791.959:101): proctitle=2F7362696E2F617564697463
746C002D52002F6574632F61756469742F61756469742E72756C6573
type=SYSCALL msg=audit(1589816791.959:101): arch=c000003e syscall=44
success=yes exit=1056 a0=3 a1=7fff9ccc98a0 a2=420 a3=0 items=0
ppid=773 pid=783 auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0
egid=0 sgid=0 fsgid=0 tty=(none) ses=4294967295 comm="auditctl"
exe="/usr/sbin/auditctl" subj=? key=(null)
type=UNKNOWN[1420] msg=audit(1589816791.959:101):
subj_selinux=system_u:system_r:unconfined_service_t:s0
subj_apparmor==unconfined
type=CONFIG_CHANGE msg=audit(1589816791.959:101): auid=4294967295
ses=4294967295 subj=? op=add_rule key=(null) list=1 res=1
type=UNKNOWN[1420] msg=audit(1589816791.959:101):
subj_selinux=system_u:system_r:unconfined_service_t:s0
subj_apparmor==unconfined

where we are getting multiple copies of the new record type, one for
each record type that had subj=?.

Not sure what it is the audit folks want here.

This is with multiple LSMs enabled; need to confirm that no change
occurs if only one is enabled.