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Re: RFC comments in lib / gc-pbkdf2-sha1.c
From: |
Simon Josefsson |
Subject: |
Re: RFC comments in lib / gc-pbkdf2-sha1.c |
Date: |
Sun, 15 Nov 2009 13:53:23 +0100 |
User-agent: |
Gnus/5.110011 (No Gnus v0.11) Emacs/23.1 (gnu/linux) |
Vladimir 'phcoder' Serbinenko <address@hidden> writes:
> Hello, all. When importing some gnulib code to GRUB2 I stumbled across
> lib / gc-pbkdf2-sha1.c having comments taken from RFC2898. As far as I
> know RFC licence prohibits modifications. This seems to be GPL-incompatible.
> So is there are any licencing problem with this file?
Thanks for the report, I rewrote the comments to not use copyrighted
words from elsewhere.
/Simon
>From 24a6641b053b7fc8bf13b4149722e85d77db9920 Mon Sep 17 00:00:00 2001
From: Simon Josefsson <address@hidden>
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 <address@hidden>
+
+ * lib/gc-pbkdf2-sha1.c: Remove comments from RFC 2898. Reported
+ by Vladimir 'phcoder' Serbinenko <address@hidden>.
+
2009-11-14 Eric Blake <address@hidden>
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 PKCS#5
- Copyright (C) 2002, 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
+ Copyright (C) 2002, 2003, 2004, 2005, 2006, 2009 Free Software Foundation,
Inc.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
@@ -15,8 +15,7 @@
along with this program; if not, write to the Free Software Foundation,
Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
-/* Written by Simon Josefsson. The comments in this file are taken
- from RFC 2898. */
+/* Written by Simon Josefsson. */
#include <config.h>
@@ -25,32 +24,12 @@
#include <stdlib.h>
#include <string.h>
-/*
- * 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 essentially
- * 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 derived
- * 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 == 0)
return GC_PKCS5_INVALID_DERIVED_KEY_LENGTH;
- /*
- *
- * 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;
- /*
- * 2. Let l be the number of hLen-octet blocks in the derived key,
- * rounding up, and let r be the number of octets in the last
- * block:
- *
- * l = CEIL (dkLen / hLen) ,
- * r = dkLen - (l - 1) * hLen .
- *
- * Here, CEIL (x) is the "ceiling" function, i.e. the smallest
- * integer greater than, or equal to, x.
- */
-
l = ((dkLen - 1) / hLen) + 1;
r = dkLen - (l - 1) * hLen;
- /*
- * 3. For each block of the derived key apply the function F defined
- * below to the password P, the salt S, the iteration count c, and
- * the block index to compute the block:
- *
- * T_1 = F (P, S, c, 1) ,
- * T_2 = F (P, S, c, 2) ,
- * ...
- * T_l = 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 PRF
- * applied to the password P and the concatenation of the salt S
- * and the block index i:
- *
- * F (P, S, c, i) = U_1 \xor U_2 \xor ... \xor U_c
- *
- * where
- *
- * U_1 = PRF (P, S || INT (i)) ,
- * U_2 = PRF (P, U_1) ,
- * ...
- * U_c = PRF (P, U_{c-1}) .
- *
- * Here, INT (i) is a four-octet encoding of the integer i, most
- * significant octet first.
- *
- * 4. Concatenate the blocks and extract the first dkLen octets to
- * produce a derived key DK:
- *
- * DK = 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 exclusive-
- * ored together to reduce concerns about the recursion degenerating
- * into a small set of values.
- *
- */
-
tmp = malloc (tmplen);
if (tmp == NULL)
return GC_MALLOC_ERROR;
--
1.6.5.2