linux-kernel - Re: [PATCH -v2 3/4] AUDIT: collect info when execve results in caps in pE

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Message-ID: <20081104192844.GA13390@us.ibm.com>
Date:	Tue, 4 Nov 2008 13:28:44 -0600
From:	"Serge E. Hallyn" <serue@...ibm.com>
To:	Eric Paris <eparis@...hat.com>
Cc:	linux-kernel@...r.kernel.org, linux-audit@...hat.com,
	sgrubb@...hat.com, morgan@...nel.org, viro@...IV.linux.org.uk
Subject: Re: [PATCH -v2 3/4] AUDIT: collect info when execve results in
	caps in pE

Quoting Eric Paris (eparis@...hat.com):
> On Tue, 2008-11-04 at 10:35 -0600, Serge E. Hallyn wrote:
> > Quoting Eric Paris (eparis@...hat.com):
> > > diff --git a/security/commoncap.c b/security/commoncap.c
> > > index 8bb95ed..534abb5 100644
> > > --- a/security/commoncap.c
> > > +++ b/security/commoncap.c
> > > @@ -8,6 +8,7 @@
> > >   */
> > > 
> > >  #include <linux/capability.h>
> > > +#include <linux/audit.h>
> > >  #include <linux/module.h>
> > >  #include <linux/init.h>
> > >  #include <linux/kernel.h>
> > > @@ -373,6 +374,9 @@ int cap_bprm_set_security (struct linux_binprm *bprm)
> > > 
> > >  void cap_bprm_apply_creds (struct linux_binprm *bprm, int unsafe)
> > >  {
> > > +	kernel_cap_t pP = current->cap_permitted;
> > > +	kernel_cap_t pE = current->cap_effective;
> > > +
> > >  	if (bprm->e_uid != current->uid || bprm->e_gid != current->gid ||
> > >  	    !cap_issubset(bprm->cap_post_exec_permitted,
> > >  			  current->cap_permitted)) {
> > > @@ -407,6 +411,12 @@ void cap_bprm_apply_creds (struct linux_binprm *bprm, int unsafe)
> > >  	}
> > > 
> > >  	/* AUD: Audit candidate if current->cap_effective is set */
> > > +	if (!cap_isclear(current->cap_effective)) {
> > > +		if (!cap_issubset(current->cap_effective, CAP_FULL_SET) ||
> > 
> > Hi Eric,
> > 
> > can you explain what the cap_issubset() check is for here?
> 
> I'm glad you noticed it, because it is backwards!
> 
> should be
> 
> if (!cap_issubset(CAP_FULL_SET, current->cap_effective) ||
> 
> The idea is that I don't care to audit
> 1) full set &&
> 2) this is root &&
> 3) root should have a full set

Cool, that makes sense.

Would you mind adding a trivial patch to your set commenting
cap_issubset() in capability.h?  If you feel it's too outside the scope
of this set I'll send such separately.  Every time I see code using
it, it takes me 5 mins to remember which order they're supposed to be
in...

> This would still consider a root without a full set because the bset had
> been changed to be an interesting event.  I'm fine with that.
> 
> I'll send -v3 once I hear comments on everything else....
> 
> -Eric

thanks,
-serge
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