linux-kernel - Re: [PATCH GHAK16 V5 00/10] capabilities: do not audit log BPRM

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Message-ID: <alpine.LFD.2.20.1710201229350.11454@t440.gateway.2wire.net>
Date:   Fri, 20 Oct 2017 12:29:50 +1100 (AEDT)
From:   James Morris <james.l.morris@...cle.com>
To:     Richard Guy Briggs <rgb@...hat.com>
cc:     linux-security-module@...r.kernel.org, linux-audit@...hat.com,
        linux-kernel@...r.kernel.org, Kees Cook <keescook@...omium.org>,
        Andy Lutomirski <luto@...nel.org>,
        "Serge E . Hallyn" <serge.hallyn@...ntu.com>,
        Paul Moore <pmoore@...hat.com>,
        Steve Grubb <sgrubb@...hat.com>, Eric Paris <eparis@...hat.com>
Subject: Re: [PATCH GHAK16 V5 00/10] capabilities: do not audit log BPRM_FCAPS
 on set*id

On Thu, 19 Oct 2017, Richard Guy Briggs wrote:

> On 2017-10-11 20:57, Richard Guy Briggs wrote:
> > The audit subsystem is adding a BPRM_FCAPS record when auditing setuid
> > application execution (SYSCALL execve). This is not expected as it was
> > supposed to be limited to when the file system actually had capabilities
> > in an extended attribute.  It lists all capabilities making the event
> > really ugly to parse what is happening.  The PATH record correctly
> > records the setuid bit and owner.  Suppress the BPRM_FCAPS record on
> > set*id.
> 
> <crickets>
> 
> Serge?  James?  Can one of you two take this via your trees since Paul
> has backed down citing (reasonably) that it is mostly capabilities
> patches rather than audit?
> 

Sure, I will take it.


> > See: https://github.com/linux-audit/audit-kernel/issues/16
> > 
> > The first to eighth patches just massage the logic to make it easier to
> > understand.  Some of them could be squashed together.
> > 
> > The patch that resolves this issue is the ninth.  
> > 
> > It would be possible to address the original issue with a change of
> > 	"!uid_eq(new->euid, root_uid) || !uid_eq(new->uid, root_uid)"
> > to
> > 	"!(uid_eq(new->euid, root_uid) || uid_eq(new->uid, root_uid))"
> > but it took me long enough to understand this logic that I don't think
> > I'd be doing any favours by leaving it this difficult to understand.
> > 
> > The final patch attempts to address all the conditions that need logging
> > based on mailing list conversations, recoginizing there is probably some
> > duplication in the logic.
> > 
> > Passes: (ltp 20170516)
> > 	./runltp -f syscalls -s cap
> > 	./runltp -f securebits
> > 	./runltp -f cap_bounds
> > 	./runltp -f filecaps
> > 	make TARGETS=capabilities kselftest (when run locally, fails over nfs)
> > 
> > Since this is mostly capabilities related rather than audit, could this go
> > through the capabilites (Serge) or security (James) trees please?  Thanks!
> > 
> > v5
> >   rebase on linux-security/next 4.14-rc2
> >   added comment block header to handle_privileged_root()
> >   moved comment in handle_privileged_root()
> >   moved root_privileged() check back into handle_privileged_root()
> > 
> > v4
> >   rebase on kees' 4.13 commoncap changes
> >   minor local func renames
> > 
> > v3
> >   refactor into several sub-functions
> >   convert most macros to inline funcs
> > 
> > v2
> >   use macros to clarify intent of calculations
> >   fix original logic error
> >   address additional audit logging conditions
> > 
> > Richard Guy Briggs (10):
> >   capabilities: factor out cap_bprm_set_creds privileged root
> >   capabilities: intuitive names for cap gain status
> >   capabilities: rename has_cap to has_fcap
> >   capabilities: use root_priveleged inline to clarify logic
> >   capabilities: use intuitive names for id changes
> >   capabilities: move audit log decision to function
> >   capabilities: remove a layer of conditional logic
> >   capabilities: invert logic for clarity
> >   capabilities: fix logic for effective root or real root
> >   capabilities: audit log other surprising conditions
> > 
> >  security/commoncap.c | 193 ++++++++++++++++++++++++++++++++++-----------------
> >  1 file changed, 128 insertions(+), 65 deletions(-)
> > 
> > -- 
> > 1.8.3.1
> > 
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-security-module" in
> > the body of a message to majordomo@...r.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 
> - 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
> 

-- 
James Morris
<james.l.morris@...cle.com>