linux-kernel - Re: [RFC PATCH ghak21 0/4] audit: address ANOM

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Message-ID: <20180308114757.lfhtgilerp337iy7@madcap2.tricolour.ca>
Date:   Thu, 8 Mar 2018 06:47:57 -0500
From:   Richard Guy Briggs <rgb@...hat.com>
To:     Steve Grubb <sgrubb@...hat.com>
Cc:     Linux-Audit Mailing List <linux-audit@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH ghak21 0/4] audit: address ANOM_LINK excess records

On 2018-02-14 22:46, Richard Guy Briggs wrote:
> On 2018-02-14 11:49, Steve Grubb wrote:
> > On Wednesday, February 14, 2018 11:18:20 AM EST Richard Guy Briggs wrote:
> > > Audit link denied events were being unexpectedly produced in a disjoint
> > > way when audit was disabled, and when they were expected, there were
> > > duplicate PATH records.  This patchset addresses both issues for
> > > symlinks and hardlinks.
> > > 
> > > This was introduced with
> > > 	commit b24a30a7305418ff138ff51776fc555ec57c011a
> > > 	("audit: fix event coverage of AUDIT_ANOM_LINK")
> > > 	commit a51d9eaa41866ab6b4b6ecad7b621f8b66ece0dc
> > > 	("fs: add link restriction audit reporting")
> > > 
> > > Here are the resulting events:
> > 
> > Have these been tested with ausearch-test?
> 
> Not yet.

I should have reported that a day or two later I ran the ausearch-test
which passed.

> > > symlink:
> > > type=PROCTITLE msg=audit(02/14/2018 04:40:21.635:238) : proctitle=cat
> > > my-passwd type=PATH msg=audit(02/14/2018 04:40:21.635:238) : item=1
> > > name=/tmp/my-passwd inode=17618 dev=00:27 mode=link,777 ouid=rgb ogid=rgb
> > > rdev=00:00 obj=unconfined_u:object_r:user_tmp_t:s0 nametype=NORMAL
> > > cap_fp=none cap_fi=none cap_fe=0 cap_fver=0 type=PATH msg=audit(02/14/2018
> > > 04:40:21.635:238) : item=0 name=/tmp inode=13446 dev=00:27
> > > mode=dir,sticky,777 ouid=root ogid=root rdev=00:00
> > > obj=system_u:object_r:tmp_t:s0 nametype=PARENT cap_fp=none cap_fi=none
> > > cap_fe=0 cap_fver=0 type=CWD msg=audit(02/14/2018 04:40:21.635:238) :
> > > cwd=/tmp
> > > type=SYSCALL msg=audit(02/14/2018 04:40:21.635:238) : arch=x86_64
> > > syscall=openat success=no exit=EACCES(Permission denied) a0=0xffffff9c
> > > a1=0x7ffc6c1acdda a2=O_RDONLY a3=0x0 items=2 ppid=549 pid=606 auid=root
> > > uid=root gid=root euid=root suid=root fsuid=root egid=root sgid=root
> > > fsgid=root tty=ttyS0 ses=1 comm= cat exe=/usr/bin/cat
> > > subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 key=(null)
> > > type=ANOM_LINK msg=audit(02/14/2018 04:40:21.635:238) : op=follow_link
> > > ppid=549 pid=606 auid=root uid=root gid=root euid=root suid=root
> > > fsuid=root egid=roo t sgid=root fsgid=root tty=ttyS0 ses=1 comm=cat
> > > exe=/usr/bin/cat
> > > subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 res=no
> > 
> > This record duplicates the SYSCALL event except for the op field. I would 
> > suggest that is the only field needed.
> 
> Agreed, but at the moment, removal of fields isn't possible unless there
> is a conflict, and even then the value should simply be corrected if
> possible.
> 
> > > ----
> > > hardlink:
> > > type=PROCTITLE msg=audit(02/14/2018 04:40:25.373:239) : proctitle=ln test
> > > test-ln type=PATH msg=audit(02/14/2018 04:40:25.373:239) : item=1
> > > name=/tmp inode=13446 dev=00:27 mode=dir,sticky,777 ouid=root ogid=root
> > > rdev=00:00 obj=system_u:object_r:tmp_t:s0 nametype=PARENT cap_fp=none
> > > cap_fi=none cap_fe=0 cap_fver=0 type=PATH msg=audit(02/14/2018
> > > 04:40:25.373:239) : item=0 name=test inode=17619 dev=00:27 mode=file,700
> > > ouid=root ogid=root rdev=00:00 obj=unconfined_u:object_r:user_tmp_t:s0
> > > nametype=NORMAL cap_fp=none cap_fi=none cap_fe=0 cap_fver=0 type=CWD
> > > msg=audit(02/14/2018 04:40:25.373:239) : cwd=/tmp
> > > type=SYSCALL msg=audit(02/14/2018 04:40:25.373:239) : arch=x86_64
> > > syscall=linkat success=no exit=EPERM(Operation not permitted)
> > > a0=0xffffff9c a1=0x7fffe6c3f628 a2=0xffffff9c a3=0x7fffe6c3f62d items=2
> > > ppid=578 pid=607 auid=rgb uid=rgb gid=rgb euid=rgb suid=rgb fsuid=rgb
> > > egid=rgb sgid=rgb fsgid=rgb tty=pts0 ses=3 comm=ln exe=/usr/bin/ln
> > > subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 key=(null)
> > > type=ANOM_LINK msg=audit(02/14/2018 04:40:25.373:239) : op=linkat ppid=578
> > > pid=607 auid=rgb uid=rgb gid=rgb euid=rgb suid=rgb fsuid=rgb egid=rgb
> > > sgid=rgb fsgid=rgb tty=pts0 ses=3 comm=ln exe=/usr/bin/ln
> > > subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 res=no
> > > 
> > > The remaining problem is how to address this when syscall logging is
> > > disabled since it needs a parent path record and/or a CWD record to
> > > complete it.  It could also use a proctitle record too.  In fact, it
> > > looks like we need a way to have multiple auxiliary records to support
> > > an arbitrary record.  Comments please.
> > 
> > Perhaps this can only be emitted correctly with SYSCALL auditing enabled. 
> > Otherwise, the event should stand completely on its own without syscall and 
> > path records. The information from them can be added, but it risks hitting 
> > the record size limit.
> 
> As Paul just pointed out (which rang a bell...) in:
> 	https://github.com/linux-audit/audit-kernel/issues/51#issuecomment-365759325
> CONFIG_AUDITSYSCALL is now forced on and if you sabbotage your
> audit.rules with -a task,never, your warranty is void.
> 
> So now, the lurking questions in the back of my head about the
> availability of syscall records has been alleviated and we should always
> see a syscall record available unless an audit rule says we are not
> interested.
> 
> > -Steve
> > 
> > > See: https://github.com/linux-audit/audit-kernel/issues/21
> > > See also: https://github.com/linux-audit/audit-kernel/issues/51
> > > 
> > > Richard Guy Briggs (4):
> > >   audit: make ANOM_LINK obey audit_enabled and audit_dummy_context
> > >   audit: link denied should not directly generate PATH record
> > >   audit: add refused symlink to audit_names
> > >   audit: add parent of refused symlink to audit_names
> > > 
> > >  fs/namei.c     | 10 ++++++++++
> > >  kernel/audit.c | 13 ++-----------
> > >  2 files changed, 12 insertions(+), 11 deletions(-)
> 
> - 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