Re: [PATCH v6 6/7] tpm: ensure that the output of PCR read contains the correct digest size

[Roberto Sassu]

On 12/5/2018 1:46 AM, Jarkko Sakkinen wrote:
> On Tue, Dec 04, 2018 at 04:09:10PM -0800, Jarkko Sakkinen wrote:
> > On Tue, Dec 04, 2018 at 09:21:37AM +0100, Roberto Sassu wrote:
> > >   	out = (struct tpm2_pcr_read_out *)&buf.data[TPM_HEADER_SIZE];
> > >   	digest_size = be16_to_cpu(out->digest_size);
> > > -	if (digest_size > sizeof(digest->digest)) {
> > > +	if (digest_size > sizeof(digest->digest) ||
> > > +	    (!digest_size_ptr && digest_size != expected_digest_size)) {
> > >   		rc = -EINVAL;
> > >   		goto out;
> > >   	}
> >
> > Just noticed this but you must squash 4-6 because applying only
> > previous commits will result a broken tree. It will be much bigger
> > commit but won't be broken.
> >
> > I think you should also feed min_rsp_body_length as you should be
> > able to precalculate.
> >
> > Last time I was asking why this isn't a bug fix. It is even for
> > the existing code. The existing code should have a bug fix that
> > checks that the received digest size so that it is the expected
> > SHA1 size before we can apply this commit.
>
> My bad. This is not the same deal as the code because in the old code we
> always copy a constant block. Here we use the variable as parameter for
> memcpy() so it is better to check the size. You can ignore the last
> paragraph completely. Sorry, had to double check this one.
>
> There is no need to do any type of bug fix for the current tree.
>
> Still 4-6 need to be squashed in order to not put purposely the tree
> into broken state.

Ok. I keep the description of 5, and add few details from 4 and 6.

Roberto


> /Jarko

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