linux-kernel - Re: [RFC] [Patch 1/1] IBAC Patch

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Date:	Fri, 09 Mar 2007 08:19:36 -0500
From:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:	Randy Dunlap <randy.dunlap@...cle.com>
Cc:	linux-security-module@...r.kernel.org, safford@...son.ibm.com,
	serue@...ux.vnet.ibm.com, kjhall@...ux.vnet.ibm.com,
	zohar@...ibm.com, linux-kernel@...r.kernel.org
Subject: Re: [RFC] [Patch 1/1] IBAC Patch

On Thu, 2007-03-08 at 15:08 -0800, Randy Dunlap wrote:
> On Thu, 08 Mar 2007 17:58:16 -0500 Mimi Zohar wrote:
> 
> > This is a request for comments for a new Integrity Based Access
> > Control(IBAC) LSM module which bases access control decisions
> > on the new integrity framework services. 
> > 
> > (Hopefully this will help clarify the interaction between an LSM 
> > module and LIM module.)
> > 
> > Index: linux-2.6.21-rc3-mm2/security/ibac/Kconfig
> > ===================================================================
> > --- /dev/null
> > +++ linux-2.6.21-rc3-mm2/security/ibac/Kconfig
> > @@ -0,0 +1,36 @@
> > +config SECURITY_IBAC
> > +	boolean "IBAC support"
> > +	depends on SECURITY && SECURITY_NETWORK && INTEGRITY
> > +	help
> > +	  Integrity Based Access Control(IBAC) implements integrity
> > +	  based access control.
> 
> Please make the help text do more than repeat the words I B A C...
> Put a short explanation or say something like:
> 	  See Documentation/security/foobar.txt for more information.
> (and add that file)

Agreed.  Perhaps something like:

Integrity Based Access Control(IBAC) uses the Linux Integrity
Module(LIM) API calls to verify an executable's metadata and 
data's integrity.  Based on the results, execution permission 
is permitted/denied.  Integrity providers may implement the 
LIM hooks differently.  For more information on integrity
verification refer to the specific integrity provider 
documentation. 

> > +config SECURITY_IBAC_BOOTPARAM
> > +	bool "IBAC boot parameter"
> > +	depends on SECURITY_IBAC
> > +	default y
> > +	help
> > +	  This option adds a kernel parameter 'ibac', which allows IBAC
> > +	  to be disabled at boot.  If this option is selected, IBAC
> > +	  functionality can be disabled with ibac=0 on the kernel
> > +	  command line.  The purpose of this option is to allow a
> > +	  single kernel image to be distributed with IBAC built in,
> > +	  but not necessarily enabled.
> > +
> > +	  If you are unsure how to answer this question, answer N.
> 
> What's the downside to having this always builtin instead of
> yet another config option?

The ability of changing LSM modules at runtime might be perceived
as problematic.

> > +static struct security_operations ibac_security_ops = {
> > +	.bprm_check_security = ibac_bprm_check_security
> > +};
> > +
> > +static int __init init_ibac(void)
> > +{
> > +	int rc;
> > +
> > +	if (!ibac_enabled)
> > +		return 0;
> > +
> > +	rc = register_security(&ibac_security_ops);
> > +	if (rc != 0)
> > +		panic("IBAC: Unable to register with kernel\n");
> 
> Normally we would not want to see a panic() from a register_xyz()
> failure, but I guess you are arguing that an ibac register_security()
> failure needs to halt everything??

Yes, as this implies that another LSM module registered the hooks first,
preventing IBAC from registering itself. 

Thank you for your other comments.  They'll be addressed in the next
ibac patch release.

Mimi Zohar

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