> > =20 >> Hello, all. When importing some gnulib code to GRUB2 I stumbled across= =20 >> lib / gc-pbkdf2-sha1.c having comments taken from RFC2898. As far as I=
>> know RFC licence prohibits modifications. This seems to be GPL-incompa=
tible.
>> So is there are any licencing problem with this file?
>> =20
>
> Thanks for the report, I rewrote the comments to not use copyrighted
> words from elsewhere.
>
> =20
Thanks. I imported it to my grub-crypto branch.
> /Simon
>
> >From 24a6641b053b7fc8bf13b4149722e85d77db9920 Mon Sep 17 00:00:00 2001=
> From: Simon Josefsson <si...@josefsson.org>
> Date: Sun, 15 Nov 2009 13:52:55 +0100
> Subject: [PATCH] lib/gc-pbkdf2-sha1.c: Remove comments from RFC 2898.
>
> ---
> ChangeLog | 5 +++
> lib/gc-pbkdf2-sha1.c | 99 ++++--------------------------------------=
--------
> 2 files changed, 13 insertions(+), 91 deletions(-)
>
> diff --git a/ChangeLog b/ChangeLog
> index a241c5b..9fe5174 100644
> --- a/ChangeLog
> +++ b/ChangeLog
> @@ -1,3 +1,8 @@
> +2009-11-15 Simon Josefsson <si...@josefsson.org>
> +
> + * lib/gc-pbkdf2-sha1.c: Remove comments from RFC 2898. Reported
> + by Vladimir 'phcoder' Serbinenko <phco...@gmail.com>.
> +
> 2009-11-14 Eric Blake <e...@byu.net>
> =20
> fnmatch: avoid compiler warning
> diff --git a/lib/gc-pbkdf2-sha1.c b/lib/gc-pbkdf2-sha1.c
> index 3c864c6..0f5211b 100644
> --- a/lib/gc-pbkdf2-sha1.c
> +++ b/lib/gc-pbkdf2-sha1.c
> @@ -1,5 +1,5 @@
> /* gc-pbkdf2-sha1.c --- Password-Based Key Derivation Function a'la PK=
CS#5
> - Copyright (C) 2002, 2003, 2004, 2005, 2006 Free Software Foundation=
, Inc.
> + Copyright (C) 2002, 2003, 2004, 2005, 2006, 2009 Free Software Foun=
dation, Inc.
> =20
> This program is free software; you can redistribute it and/or modif=
y
> it under the terms of the GNU General Public License as published b=
y
> @@ -15,8 +15,7 @@
> along with this program; if not, write to the Free Software Foundat=
ion,
> Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. =
*/
> =20
> -/* Written by Simon Josefsson. The comments in this file are taken
> - from RFC 2898. */
> +/* Written by Simon Josefsson. */
> =20
> #include <config.h>
> =20
> @@ -25,32 +24,12 @@
> #include <stdlib.h>
> #include <string.h>
> =20
> -/*
> - * 5.2 PBKDF2
> - *
> - * PBKDF2 applies a pseudorandom function (see Appendix B.1 for an
> - * example) to derive keys. The length of the derived key is essentia=
lly
> - * unbounded. (However, the maximum effective search space for the
> - * derived key may be limited by the structure of the underlying
> - * pseudorandom function. See Appendix B.1 for further discussion.)
> - * PBKDF2 is recommended for new applications.
> - *
> - * PBKDF2 (P, S, c, dkLen)
> - *
> - * Options: PRF underlying pseudorandom function (hLen
> - * denotes the length in octets of the
> - * pseudorandom function output)
> - *
> - * Input: P password, an octet string (ASCII or UTF=
-8)
> - * S salt, an octet string
> - * c iteration count, a positive integer
> - * dkLen intended length in octets of the derive=
d
> - * key, a positive integer, at most
> - * (2^32 - 1) * hLen
> - *
> - * Output: DK derived key, a dkLen-octet string
> - */
> -
> +/* Implement PKCS#5 PBKDF2 as per RFC 2898. The PRF to use is hard
> + coded to be HMAC-SHA1. Inputs are the password P of length PLEN,
> + the salt S of length SLEN, the iteration counter C (> 0), and the
> + desired derived output length DKLEN. Output buffer is DK which
> + must have room for at least DKLEN octets. The output buffer will
> + be filled with the derived data. */
> Gc_rc
> gc_pbkdf2_sha1 (const char *P, size_t Plen,
> const char *S, size_t Slen,
> @@ -75,74 +54,12 @@ gc_pbkdf2_sha1 (const char *P, size_t Plen,
> if (dkLen =3D=3D 0)
> return GC_PKCS5_INVALID_DERIVED_KEY_LENGTH;
> =20
> - /*
> - *
> - * Steps:
> - *
> - * 1. If dkLen > (2^32 - 1) * hLen, output "derived key too long=
" and
> - * stop.
> - */
> -
> if (dkLen > 4294967295U)
> return GC_PKCS5_DERIVED_KEY_TOO_LONG;
> =20
> - /*
> - * 2. Let l be the number of hLen-octet blocks in the derived ke=
y,
> - * rounding up, and let r be the number of octets in the last=
> - * block:
> - *
> - * l =3D CEIL (dkLen / hLen) ,
> - * r =3D dkLen - (l - 1) * hLen .
> - *
> - * Here, CEIL (x) is the "ceiling" function, i.e. the smalles=
t
> - * integer greater than, or equal to, x.
> - */
> -
> l =3D ((dkLen - 1) / hLen) + 1;
> r =3D dkLen - (l - 1) * hLen;
> =20
> - /*
> - * 3. For each block of the derived key apply the function F def=
ined
> - * below to the password P, the salt S, the iteration count c=
, and
> - * the block index to compute the block:
> - *
> - * T_1 =3D F (P, S, c, 1) ,
> - * T_2 =3D F (P, S, c, 2) ,
> - * ...
> - * T_l =3D F (P, S, c, l) ,
> - *
> - * where the function F is defined as the exclusive-or sum of=
the
> - * first c iterates of the underlying pseudorandom function P=
RF
> - * applied to the password P and the concatenation of the sal=
t S
> - * and the block index i:
> - *
> - * F (P, S, c, i) =3D U_1 \xor U_2 \xor ... \xor U_=
c
> - *
> - * where
> - *
> - * U_1 =3D PRF (P, S || INT (i)) ,
> - * U_2 =3D PRF (P, U_1) ,
> - * ...
> - * U_c =3D PRF (P, U_{c-1}) .
> - *
> - * Here, INT (i) is a four-octet encoding of the integer i, m=
ost
> - * significant octet first.
> - *
> - * 4. Concatenate the blocks and extract the first dkLen octets =
to
> - * produce a derived key DK:
> - *
> - * DK =3D T_1 || T_2 || ... || T_l<0..r-1>
> - *
> - * 5. Output the derived key DK.
> - *
> - * Note. The construction of the function F follows a "belt-and-
> - * suspenders" approach. The iterates U_i are computed recursively =
to
> - * remove a degree of parallelism from an opponent; they are exclus=
ive-
> - * ored together to reduce concerns about the recursion degeneratin=
g
> - * into a small set of values.
> - *
> - */
> -
> tmp =3D malloc (tmplen);
> if (tmp =3D=3D NULL)
> return GC_MALLOC_ERROR;
> =20
--=20
Regards
Vladimir 'phcoder' Serbinenko
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