linux-kernel - Re: [RFC][Patch 2/3]integrity: IMA as an integrity service provider

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Message-Id: <1182350923.5688.27.camel@localhost.localdomain>
Date:	Wed, 20 Jun 2007 10:48:43 -0400
From:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:	James Morris <jmorris@...ei.org>
Cc:	linux-kernel@...r.kernel.org, safford@...son.ibm.com,
	serue@...ux.vnet.ibm.com, zohar@...ibm.com, sailer@...ibm.com
Subject: Re: [RFC][Patch 2/3]integrity: IMA as an integrity service provider

On Tue, 2007-06-19 at 22:18 -0400, James Morris wrote:
> On Mon, 18 Jun 2007, Mimi Zohar wrote:
> 
> 
> > +/* what could we exclude
> > + *   - non-executable/non-library files ?
> > + *   - /proc /dev ?
> > + * Only measure files opened for read-only or execute
> > + */
> > +static int skip_measurement(struct inode *inode, int mask)
> > +{
> > +	if ((inode->i_sb->s_magic == PROC_SUPER_MAGIC) ||
> > +	    (inode->i_sb->s_magic == SYSFS_MAGIC)) {
> > +		return 1;	/*can't measure */
> > +	}
> 
> I'm pretty sure you should skip measurement for many more pseudo 
> filesystems than this.

The LSM module controls what is measured and should only be calling
integrity_measure() for appropriate files.  IBAC, for example, only
calls integrity_measure() for executables from bprm_check_security()
and file_mmap() and for other regular files from inode_permission(), 
based on the existence of the 'security.measure' xattr, which is 
labeled by a userspace application.  The integrity provider, here,
is just doing a quick sanity check, but I'll definitely make it 
more complete and fix the comment to make this clearer.

Thanks!

Mimi

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