On 5/18/2020 5:16 PM, Casey Schaufler wrote: > On 5/18/2020 3:21 PM, Paul Moore wrote: >> On Mon, May 18, 2020 at 4:43 PM Casey Schaufler <casey@xxxxxxxxxxxxxxxx> wrote: >>> On 5/18/2020 11:02 AM, Stephen Smalley wrote: >>>> On Thu, May 14, 2020 at 7:30 PM Casey Schaufler <casey@xxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxx> >>>>> Signed-off-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx> >>>>> Cc: linux-audit@xxxxxxxxxx >>>>> --- >>>> 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? >>> I haven't looked at the userspace code, but I expect you're right. >>> It looks like there will need to be some change in the userspace >>> for the multiple LSM case. The "completion" shown here isn't correct, >>> because it only fills in one of the subject attributes, not both. >> Wait, didn't we agree on a a "subj=? subj_selinux=XXX >> subj_apparmor=YYY subj_smack=ZZZ" format? It looks like there are two >> 'subj' fields in the record above which is bad, don't do that please. > That's not something that's coming from the kernel. OK, I see that I missed one in netlbl_audit_start_common(), although I don't think that's where this event came from. > I'll check again, but I think that everyplace in the kernel that > produces a subj= has been trained to create a type=1420 record > instead. > >>>> 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=?. >>> While obviously wasteful, the type=1420 behavior is consistent with >>> the subj=? behavior, which is to duplicate the subj= value. I know >>> we've got enough hobgoblins in the audit system that we don't need >>> to add any more in the name of a foolish consistency. >> You need to provide a bit more reason why we need byte-for-byte >> duplicate records in a single event. As it currently stands this >> looks like something we definitely don't want. > The CONFIG_CHANGE record already duplicates the subj= information > in the SYSCALL record. I just maintained the duplication. You're > right, it's silly to have two identical type=1420 records for the event. > I will have to come up with a mechanism to prevent the duplication. > with luck, there's already a similar case for some other record. > >> -- >> paul moore >> www.paul-moore.com
