/* gc-pbkdf2-sha1.c --- Password-Based Key Derivation Function a'la PKCS#5
- Copyright (C) 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
+ Copyright (C) 2002-2006, 2009-2014 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
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
- along with this program; if not, write to the Free Software Foundation,
- Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
+ along with this program; if not, see <http://www.gnu.org/licenses/>. */
-/* Written by Simon Josefsson. The comments in this file are taken
- from RFC 2898. */
+/* Written by Simon Josefsson. */
-#ifdef HAVE_CONFIG_H
-# include <config.h>
-#endif
+#include <config.h>
#include "gc.h"
#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,
- unsigned int c,
- char *DK, size_t dkLen)
+ const char *S, size_t Slen,
+ unsigned int c,
+ char *DK, size_t dkLen)
{
unsigned int hLen = 20;
char U[20];
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;
memset (T, 0, hLen);
for (u = 1; u <= c; u++)
- {
- if (u == 1)
- {
- tmp[Slen + 0] = (i & 0xff000000) >> 24;
- tmp[Slen + 1] = (i & 0x00ff0000) >> 16;
- tmp[Slen + 2] = (i & 0x0000ff00) >> 8;
- tmp[Slen + 3] = (i & 0x000000ff) >> 0;
-
- rc = gc_hmac_sha1 (P, Plen, tmp, tmplen, U);
- }
- else
- rc = gc_hmac_sha1 (P, Plen, U, hLen, U);
-
- if (rc != GC_OK)
- {
- free (tmp);
- return rc;
- }
-
- for (k = 0; k < hLen; k++)
- T[k] ^= U[k];
- }
+ {
+ if (u == 1)
+ {
+ tmp[Slen + 0] = (i & 0xff000000) >> 24;
+ tmp[Slen + 1] = (i & 0x00ff0000) >> 16;
+ tmp[Slen + 2] = (i & 0x0000ff00) >> 8;
+ tmp[Slen + 3] = (i & 0x000000ff) >> 0;
+
+ rc = gc_hmac_sha1 (P, Plen, tmp, tmplen, U);
+ }
+ else
+ rc = gc_hmac_sha1 (P, Plen, U, hLen, U);
+
+ if (rc != GC_OK)
+ {
+ free (tmp);
+ return rc;
+ }
+
+ for (k = 0; k < hLen; k++)
+ T[k] ^= U[k];
+ }
memcpy (DK + (i - 1) * hLen, T, i == l ? r : hLen);
}
projects / gnulib.git / blobdiff