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

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Date:   Thu, 19 Oct 2017 09:08:10 -0400
From:   Richard Guy Briggs <rgb@...hat.com>
To:     linux-security-module@...r.kernel.org, linux-audit@...hat.com,
        linux-kernel@...r.kernel.org
Cc:     Kees Cook <keescook@...omium.org>,
        Andy Lutomirski <luto@...nel.org>,
        "Serge E . Hallyn" <serge.hallyn@...ntu.com>,
        James Morris <james.l.morris@...cle.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 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?

> 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
> 
> --
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- 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