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From:   Ard Biesheuvel <ardb@kernel.org>
Date:   Thu, 16 Jul 2020 17:37:32 +0300
Message-ID: <CAMj1kXHD4_nXydFnCwsjV_fyvmiD=L8QPBVudmnQfAJYfhu82g@mail.gmail.com>
Subject: Re: [PATCH v2 2/5] lib/mpi: Add mpi_sub_ui()
To:     Marcelo Henrique Cerri <marcelo.cerri@canonical.com>
Cc:     Herbert Xu <herbert@gondor.apana.org.au>,
        =?UTF-8?Q?Stephan_M=C3=BCller?= <smueller@chronox.de>,
        Linux Crypto Mailing List <linux-crypto@vger.kernel.org>,
        Tianjia Zhang <tianjia.zhang@linux.alibaba.com>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>, nhorman@redhat.com,
        simo@redhat.com
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On Thu, 16 Jul 2020 at 17:23, Marcelo Henrique Cerri
<marcelo.cerri@canonical.com> wrote:
>
> On Thu, Jul 16, 2020 at 04:53:24PM +0300, Ard Biesheuvel wrote:
> > On Thu, 16 Jul 2020 at 16:41, Marcelo Henrique Cerri
> > <marcelo.cerri@canonical.com> wrote:
> > >
> > > On Thu, Jul 16, 2020 at 04:09:39PM +0300, Ard Biesheuvel wrote:
> > > > On Thu, 16 Jul 2020 at 15:50, Marcelo Henrique Cerri
> > > > <marcelo.cerri@canonical.com> wrote:
> > > > >
> > > > > No. The code is really based on Gnu MP. I used the header from
> > > > > lib/mpi/mpi-pow.c as reference and that's source of the mention t=
o
> > > > > GnuPG that went unnoticed by me.
> > > > >
> > > >
> > > > So where did the file lib/mpi/mpi-sub-ui.c come from? From GnuPG or
> > > > from GnuMP? Did you modify the license statement? Because as propos=
ed,
> > > > this patch clearly is not acceptable from GPL compliance  point of
> > > > view.
> > >
> > > Sorry for the confusion. The code is from Gnu MP (not GnuPG).
> > >
> > > Gnu MP is distributed under either LGPLv3 or later or GPLv2 or later
> > > (check their license statement on the aors_ui.h file below).
> > >
> > > For mpi-sub-ui.h I added a SPDX identifier for GPLv2 or later and I
> > > kept the FSF copyright line.
> > >
> > > I also used the header from mpi-powm.c as a reference basically to
> > > inform the code was changed from its original form.
> > >
> > > Here lies my mistake, I didn't notice that part was referring to GnuP=
G
> > > instead of Gnu MP.
> > >
> > > So mpi-sub-ui.h header was actually intended to be:
> > >
> > >     // SPDX-License-Identifier: GPL-2.0-or-later
> > >     /* mpi-sub-ui.c  -  MPI functions
> > >      *      Copyright 1991, 1993, 1994, 1996, 1999-2002, 2004, 2012, =
2013, 2015
> > >      *      Free Software Foundation, Inc.
> > >      *
> > >      * This file is part of Gnu MP.
> > >      *
> > >      * Note: This code is heavily based on the GNU MP Library.
> > >      *      Actually it's the same code with only minor changes in th=
e
> > >      *      way the data is stored; this is to support the abstractio=
n
> > >      *      of an optional secure memory allocation which may be used
> > >      *      to avoid revealing of sensitive data due to paging etc.
> > >      *      The GNU MP Library itself is published under the LGPL;
> > >      *      however I decided to publish this code under the plain GP=
L.
> > >      */
> > >
> > > Or maybe instead of "This file is part of Gnu MP.", "This file is
> > > based on Gnu MP" might be more appropriate.
> > >
> > > Do you have any license concerns considering this updated header?
> > >
> >
> > Yes. How can this code be both part of GnuMP *and* be heavily based on
> > it, but with changes?
> >

You haven't answered this question yet. I suppose you just slapped a
different license text on this file, one that already existed in
lib/mpi?

> > Please avoid making changes to the original header, just add the SPDX
> > header in front, and add a clear justification in the commit log where
> > the file came from (preferably including git url and commit ID), and
> > what you based your assertion on that its license is compatible with
> > GPLv2.
>
> The commit message is stating the origin, but I can add a reference to
> the mercurial repo with its corresponding id.
>

Yes, please.

> >
> > Ideally, you would import the file *exactly* as it appears in the
> > upstream in one patch (with the above justification), and apply any
> > necessary changes in a subsequent patch, so it's  crystal clear that
> > we are complying with the original license.
>
> I'm not sure that's the ideal approach for this case. The logic is the
> same but since naming convention, macros, data types and etc are
> pretty different everything was basically re-written to fit the
> kernel. Adding the original file and then massively changing will just
> add unnecessary noise.
>

Do any of these modifications resemble the changes made to the GnuPG
versions of these routines?

> If you agree I will update the commit message with more details about
> the original source and then just update the comment header in
> mpi-sub-ui.c following closely the original header with minor
> adjustments to explain its origin and to fix some checkpatch warnings.
>

That is fine, provided that none of our modifications were taken from
the GnuPG version of this file without giving credit.


> Something like that:
>
> // SPDX-License-Identifier: GPL-2.0-or-later
> /* mpi-sub-ui.c - Subtract an unsigned integer from an MPI.
>  *
>  * Copyright 1991, 1993, 1994, 1996, 1999-2002, 2004, 2012, 2013, 2015
>  * Free Software Foundation, Inc.
>  *
>  * This file was based on the GNU MP Library source file:
>  * https://gmplib.org/repo/gmp-6.2/file/tip/mpz/aors_ui.h
>  *
>  * The GNU MP Library is free software; you can redistribute it and/or mo=
dify
>  * it under the terms of either:
>  *
>  *   * the GNU Lesser General Public License as published by the Free
>  *     Software Foundation; either version 3 of the License, or (at your
>  *     option) any later version.
>  *
>  * or
>  *
>  *   * the GNU General Public License as published by the Free Software
>  *     Foundation; either version 2 of the License, or (at your option) a=
ny
>  *     later version.
>  *
>  * or both in parallel, as here.
>  *
>  * The GNU MP Library is distributed in the hope that it will be useful, =
but
>  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABI=
LITY
>  * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public Licen=
se
>  * for more details.
>  *
>  * You should have received copies of the GNU General Public License and =
the
>  * GNU Lesser General Public License along with the GNU MP Library.  If n=
ot,
>  * see https://www.gnu.org/licenses/.
>  */
>
> >
> >
> >
> > >
> > > >
> > > >
> > > >
> > > > > You can find the original Gnu MP source that I used as reference =
in
> > > > > the file gmp-6.2.0/mpz/aors_ui.h from:
> > > > >
> > > > > https://gmplib.org/download/gmp/gmp-6.2.0.tar.lz
> > > > >
> > > > > I'm pasting the contents of gmp-6.2.0/mpz/aors_ui.h below for
> > > > > reference. Do you think we should use or adapt the original heade=
r
> > > > > instead?
> > > > >
> > > > > That said, assuming the patch set submitted by Tianjia is updated=
 to
> > > > > ensure that mpi_sub_ui() and other functions are returning alloca=
tion
> > > > > errors, we could drop this patch in favor of that patch set that =
is
> > > > > more extensive and also provides an implementation to mpi_sub_ui(=
).
> > > > >
> > > > >
> > > > > --->8---
> > > > > /* mpz_add_ui, mpz_sub_ui -- Add or subtract an mpz_t and an unsi=
gned
> > > > >    one-word integer.
> > > > >
> > > > > Copyright 1991, 1993, 1994, 1996, 1999-2002, 2004, 2012, 2013, 20=
15
> > > > > Free Software Foundation, Inc.
> > > > >
> > >
> > >
> > > Gnu MP license -.
> > >                 V
> > >
> > >
> > > > > This file is part of the GNU MP Library.
> > > > >
> > > > > The GNU MP Library is free software; you can redistribute it and/=
or modify
> > > > > it under the terms of either:
> > > > >
> > > > >   * the GNU Lesser General Public License as published by the Fre=
e
> > > > >     Software Foundation; either version 3 of the License, or (at =
your
> > > > >     option) any later version.
> > > > >
> > > > > or
> > > > >
> > > > >   * the GNU General Public License as published by the Free Softw=
are
> > > > >     Foundation; either version 2 of the License, or (at your opti=
on) any
> > > > >     later version.
> > > > >
> > > > > or both in parallel, as here.
> > > > >
> > > > > The GNU MP Library is distributed in the hope that it will be use=
ful, but
> > > > > WITHOUT ANY WARRANTY; without even the implied warranty of MERCHA=
NTABILITY
> > > > > or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public =
License
> > > > > for more details.
> > > > >
> > > > > You should have received copies of the GNU General Public License=
 and the
> > > > > GNU Lesser General Public License along with the GNU MP Library. =
 If not,
> > > > > see https://www.gnu.org/licenses/.  */
> > > > >
> > > > > #include "gmp-impl.h"
> > > > >
> > > > >
> > > > > #ifdef OPERATION_add_ui
> > > > > #define FUNCTION          mpz_add_ui
> > > > > #define FUNCTION2         mpz_add
> > > > > #define VARIATION_CMP     >=3D
> > > > > #define VARIATION_NEG
> > > > > #define VARIATION_UNNEG   -
> > > > > #endif
> > > > >
> > > > > #ifdef OPERATION_sub_ui
> > > > > #define FUNCTION          mpz_sub_ui
> > > > > #define FUNCTION2         mpz_sub
> > > > > #define VARIATION_CMP     <
> > > > > #define VARIATION_NEG     -
> > > > > #define VARIATION_UNNEG
> > > > > #endif
> > > > >
> > > > > #ifndef FUNCTION
> > > > > Error, need OPERATION_add_ui or OPERATION_sub_ui
> > > > > #endif
> > > > >
> > > > >
> > > > > void
> > > > > FUNCTION (mpz_ptr w, mpz_srcptr u, unsigned long int vval)
> > > > > {
> > > > >   mp_srcptr up;
> > > > >   mp_ptr wp;
> > > > >   mp_size_t usize, wsize;
> > > > >   mp_size_t abs_usize;
> > > > >
> > > > > #if BITS_PER_ULONG > GMP_NUMB_BITS  /* avoid warnings about shift=
 amount */
> > > > >   if (vval > GMP_NUMB_MAX)
> > > > >     {
> > > > >       mpz_t v;
> > > > >       mp_limb_t vl[2];
> > > > >       PTR(v) =3D vl;
> > > > >       vl[0] =3D vval & GMP_NUMB_MASK;
> > > > >       vl[1] =3D vval >> GMP_NUMB_BITS;
> > > > >       SIZ(v) =3D 2;
> > > > >       FUNCTION2 (w, u, v);
> > > > >       return;
> > > > >     }
> > > > > #endif
> > > > >
> > > > >   usize =3D SIZ (u);
> > > > >   if (usize =3D=3D 0)
> > > > >     {
> > > > >       MPZ_NEWALLOC (w, 1)[0] =3D vval;
> > > > >       SIZ (w) =3D VARIATION_NEG (vval !=3D 0);
> > > > >       return;
> > > > >     }
> > > > >
> > > > >   abs_usize =3D ABS (usize);
> > > > >
> > > > >   /* If not space for W (and possible carry), increase space.  */
> > > > >   wp =3D MPZ_REALLOC (w, abs_usize + 1);
> > > > >
> > > > >   /* These must be after realloc (U may be the same as W).  */
> > > > >   up =3D PTR (u);
> > > > >
> > > > >   if (usize VARIATION_CMP 0)
> > > > >     {
> > > > >       mp_limb_t cy;
> > > > >       cy =3D mpn_add_1 (wp, up, abs_usize, (mp_limb_t) vval);
> > > > >       wp[abs_usize] =3D cy;
> > > > >       wsize =3D VARIATION_NEG (abs_usize + cy);
> > > > >     }
> > > > >   else
> > > > >     {
> > > > >       /* The signs are different.  Need exact comparison to deter=
mine
> > > > >          which operand to subtract from which.  */
> > > > >       if (abs_usize =3D=3D 1 && up[0] < vval)
> > > > >         {
> > > > >           wp[0] =3D vval - up[0];
> > > > >           wsize =3D VARIATION_NEG 1;
> > > > >         }
> > > > >       else
> > > > >         {
> > > > >           mpn_sub_1 (wp, up, abs_usize, (mp_limb_t) vval);
> > > > >           /* Size can decrease with at most one limb.  */
> > > > >           wsize =3D VARIATION_UNNEG (abs_usize - (wp[abs_usize - =
1] =3D=3D 0));
> > > > >         }
> > > > >     }
> > > > >
> > > > >   SIZ (w) =3D wsize;
> > > > > }
> > > > > --->*---
> > > > >
> > > > >
> > > > >
> > > > > On Thu, Jul 16, 2020 at 11:41:17AM +0300, Ard Biesheuvel wrote:
> > > > > > On Thu, 16 Jul 2020 at 10:30, Herbert Xu <herbert@gondor.apana.=
org.au> wrote:
> > > > > > >
> > > > > > > On Sun, Jul 12, 2020 at 06:39:54PM +0200, Stephan M=C3=BCller=
 wrote:
> > > > > > > >
> > > > > > > > diff --git a/lib/mpi/mpi-sub-ui.c b/lib/mpi/mpi-sub-ui.c
> > > > > > > > new file mode 100644
> > > > > > > > index 000000000000..fa6b085bac36
> > > > > > > > --- /dev/null
> > > > > > > > +++ b/lib/mpi/mpi-sub-ui.c
> > > > > > > > @@ -0,0 +1,60 @@
> > > > > > > > +// SPDX-License-Identifier: GPL-2.0-or-later
> > > > > > > > +/* mpi-sub-ui.c  -  MPI functions
> > > > > > > > + *      Copyright 1991, 1993, 1994, 1996, 1999-2002, 2004,=
 2012, 2013, 2015
> > > > > > > > + *      Free Software Foundation, Inc.
> > > > > > > > + *
> > > > > > > > + * This file is part of GnuPG.
> > > > > > > > + *
> > > > > > > > + * Note: This code is heavily based on the GNU MP Library.
> > > > > > > > + *    Actually it's the same code with only minor changes =
in the
> > > > > > > > + *    way the data is stored; this is to support the abstr=
action
> > > > > > > > + *    of an optional secure memory allocation which may be=
 used
> > > > > > > > + *    to avoid revealing of sensitive data due to paging e=
tc.
> > > > > > > > + *    The GNU MP Library itself is published under the LGP=
L;
> > > > > > > > + *    however I decided to publish this code under the pla=
in GPL.
> > > > > > > > + */
> > > > > > >
> > > > > > > Hmm, you said that this code is from GNU MP.  But this notice=
 clearly
> > > > > > > says that it's part of GnuPG and is under GPL.  Though it doe=
sn't
> > > > > > > clarify what version of GPL it is.  Can you please clarify th=
is with
> > > > > > > the author?
> > > > > > >
> > > > > >
> > > > > > GnuPG was relicensed under GPLv3 in ~2007, IIRC, so given the
> > > > > > copyright years and the explicit statements that the file is pa=
rt of
> > > > > > GnuPG and not under the original LGPL license, there is no way =
we can
> > > > > > take this code under the kernel's GPLv2 license.
> > > > >
> > > > > --
> > > > > Regards,
> > > > > Marcelo
> > > > >
> > >
> > > --
> > > Regards,
> > > Marcelo
> > >
>
> --
> Regards,
> Marcelo
>