linux-kernel - Re: [PATCH v5 03/21] evm: re-release

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Date:	Fri, 20 May 2011 08:43:27 -0500
From:	"Serge E. Hallyn" <serge@...lyn.com>
To:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
Cc:	"Serge E. Hallyn" <serge@...lyn.com>,
	linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	James Morris <jmorris@...ei.org>,
	David Safford <safford@...son.ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Greg KH <greg@...ah.com>,
	Dmitry Kasatkin <dmitry.kasatkin@...ia.com>,
	Mimi Zohar <zohar@...ibm.com>
Subject: Re: [PATCH v5 03/21] evm: re-release

Quoting Mimi Zohar (zohar@...ux.vnet.ibm.com):
> On Thu, 2011-05-19 at 16:37 -0500, Serge E. Hallyn wrote: 
> > Quoting Mimi Zohar (zohar@...ux.vnet.ibm.com):
> > ...
> > > +extern int evm_hmac_size;
> > ...
> > > +int evm_hmac_size = SHA1_DIGEST_SIZE;
> > 
> > I think I object to having both MAX_DIGEST_SIZE and evm_hmac_size, both
> > of which are set to SHA1_DIGEST_SIZE throughout this patchset.  Especially
> > because of the comment I was about to make on patch 4/21, where you
> > then prepend the hmac with a 'type' byte, and start passing around
> > MAX_DIGEST_SIZE+1 and evm_hmac_size+1.
> > 
> > Even if you're going to be using those differently in a later patchset,
> > let's focus on this set for now and keep things simpler.  One constant
> > for the hmac size, and then please define a new one (in patch 4) for
> > the annotated digest size.  I can't think think of a good name.  Which
> > suggests that perhaps you should define a nicely typed struct to contain
> > the header+hmac...
> > 
> > I see no other problems, so presuming that these are nicely addressed
> > I expect to happily ack.
> > 
> > thanks,
> > -serge
> 
> Ok, MAX_DIGEST_SIZE was defined in the first patch of this patchset,
> which moves the iint from IMA to integrity, but it seems to be
> unnecessary for any of the additional EVM or IMA extensions, including
> support for additional IMA hash sizes.  I'll remove MAX_DIGEST_SIZE.
> 
> The reason for introducing the extra byte at this point in the patch

Right, just to be clear, I had no complaints about introducing the extra
byte now.

> set, as opposed to waiting to do so in the digital signature patches, is
> to permit existing labeled systems to continue to run properly (and be
> bisect safe).  Defining a structure is a good idea.
> 
> thanks,
> 
> Mimi

Sorry to be adding work.  I just fear misinterpretations of the +1 will
cause hard to debug maintenance snafus.

thanks,
-serge
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