Re: [Qemu-devel] [PATCH v4 04/26] crypto: add support for anti-forensic split algorithm

[Fam Zheng]

On Fri, 03/11 16:55, Daniel P. Berrange wrote:
> On Mon, Mar 07, 2016 at 01:51:40PM +0800, Fam Zheng wrote:
> > On Mon, 02/29 12:00, Daniel P. Berrange wrote:
> > > The LUKS format specifies an anti-forensic split algorithm which
> > > is used to artificially expand the size of the key material on
> > > disk. This is an implementation of that algorithm.
> > > 
> > > Signed-off-by: Daniel P. Berrange <address@hidden>
> > > ---
> > >  crypto/Makefile.objs        |   1 +
> > >  crypto/afsplit.c            | 158 ++++++++++++++++++++++++++++++++++++
> > >  include/crypto/afsplit.h    | 135 +++++++++++++++++++++++++++++++
> > >  tests/.gitignore            |   1 +
> > >  tests/Makefile              |   2 +
> > >  tests/test-crypto-afsplit.c | 190 
> > > ++++++++++++++++++++++++++++++++++++++++++++
> > >  6 files changed, 487 insertions(+)
> > >  create mode 100644 crypto/afsplit.c
> > >  create mode 100644 include/crypto/afsplit.h
> > >  create mode 100644 tests/test-crypto-afsplit.c
> > > 
> 
> > > +static int qcrypto_afsplit_hash(QCryptoHashAlgorithm hash,
> > > +                                size_t blocklen,
> > > +                                uint8_t *block,
> > > +                                Error **errp)
> > > +{
> > > +    size_t digestlen = qcrypto_hash_digest_len(hash);
> > > +
> > > +    size_t hashcount = blocklen / digestlen;
> > 
> > Do you want to use DIV_ROUND_UP? Because if blocklen < digestlen, hashcount 
> > is
> > 0, and your for loop below will be skipped.
> 
> It is not needed actually - look a couple of lines
> further where we do  'if (finallen) { hashcount ++ }'.
> This achieves the same end result.

Yes you're right.

Reviewed-by: Fam Zheng <address@hidden>