sbin/cgdconfig/pkcs5_pbkdf2.c

   1 /* $NetBSD: pkcs5_pbkdf2.c,v 1.13 2008/04/21 15:23:35 christos Exp $ */
   2
   3 /*-
   4  * Copyright (c) 2002, 2003 The NetBSD Foundation, Inc.
   5  * All rights reserved.
   6  *
   7  * This code is derived from software contributed to The NetBSD Foundation
   8  * by Roland C. Dowdeswell.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
  20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
  21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
  23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  29  * POSSIBILITY OF SUCH DAMAGE.
  30  */
  31
  32 /*
  33  * This code is an implementation of PKCS #5 PBKDF2 which is described
  34  * in:
  35  *
  36  * ``PKCS #5 v2.0: Password-Based Cryptography Standard'', RSA Laboratories,
  37  * March 25, 1999.
  38  *
  39  * and can be found at the following URL:
  40  *
  41  *      http://www.rsasecurity.com/rsalabs/pkcs/pkcs-5/
  42  *
  43  * It was also republished as RFC 2898.
  44  */
  45
  46
  47 #include <sys/cdefs.h>
  48 #ifndef lint
  49 __RCSID("$NetBSD: pkcs5_pbkdf2.c,v 1.13 2008/04/21 15:23:35 christos Exp $");
  50 #endif
  51
  52 #include <sys/resource.h>
  53 #include <sys/endian.h>
  54
  55 #include <assert.h>
  56 #include <stdlib.h>
  57 #include <string.h>
  58 #include <err.h>
  59 #include <util.h>
  60
  61 #include <openssl/hmac.h>
  62
  63 #include "pkcs5_pbkdf2.h"
  64 #include "utils.h"
  65
  66 static void     prf_iterate(u_int8_t *, const u_int8_t *, size_t,
  67                             const u_int8_t *, size_t, size_t, size_t);
  68 static int      pkcs5_pbkdf2_time(size_t, size_t);
  69
  70 #define PRF_BLOCKLEN    20
  71
  72 static void
  73 prf_iterate(u_int8_t *r, const u_int8_t *P, size_t Plen,
  74             const u_int8_t *S, size_t Slen, size_t c, size_t ind)
  75 {
  76         int              first_time = 1;
  77         size_t           i;
  78         size_t           datalen;
  79         unsigned int     tmplen;
  80         u_int8_t        *data;
  81         u_int8_t         tmp[EVP_MAX_MD_SIZE];
  82
  83         data = emalloc(Slen + 4);
  84         (void)memcpy(data, S, Slen);
  85         be32enc(data + Slen, ind);
  86         datalen = Slen + 4;
  87
  88         for (i=0; i < c; i++) {
  89                 (void)HMAC(EVP_sha1(), P, Plen, data, datalen, tmp, &tmplen);
  90
  91                 assert(tmplen == PRF_BLOCKLEN);
  92
  93                 if (first_time) {
  94                         (void)memcpy(r, tmp, PRF_BLOCKLEN);
  95                         first_time = 0;
  96                 } else
  97                         memxor(r, tmp, PRF_BLOCKLEN);
  98                 (void)memcpy(data, tmp, PRF_BLOCKLEN);
  99                 datalen = PRF_BLOCKLEN;
 100         }
 101         free(data);
 102 }
 103
 104 /*
 105  * pkcs5_pbkdf2 takes all of its lengths in bytes.
 106  */
 107
 108 int
 109 pkcs5_pbkdf2(u_int8_t **r, size_t dkLen, const u_int8_t *P, size_t Plen,
 110              const u_int8_t *S, size_t Slen, size_t c, int compat)
 111 {
 112         size_t  i;
 113         size_t  l;
 114
 115         /* sanity */
 116         if (!r)
 117                 return -1;
 118         if (dkLen == 0)
 119                 return -1;
 120         if (c < 1)
 121                 return -1;
 122
 123         /* Step 2 */
 124         l = (dkLen + PRF_BLOCKLEN - 1) / PRF_BLOCKLEN;
 125
 126         /* allocate the output */
 127         *r = emalloc(l * PRF_BLOCKLEN);
 128
 129         /* Step 3 */
 130         for (i = 0; i < l; i++)
 131                 prf_iterate(*r + (PRF_BLOCKLEN * i), P, Plen, S, Slen, c,
 132                         (compat?i:i+1));
 133
 134         /* Step 4 and 5
 135          *  by the structure of the code, we do not need to concatenate
 136          *  the blocks, they're already concatenated.  We do not extract
 137          *  the first dkLen octets, since we [naturally] assume that the
 138          *  calling function will use only the octets that it needs and
 139          *  the free(3) will free all of the allocated memory.
 140          */
 141         return 0;
 142 }
 143
 144 /*
 145  * We use predefined lengths for the password and salt to ensure that
 146  * no analysis can be done on the output of the calibration based on
 147  * those parameters.  We do not do the same for dkLen because:
 148  *      1.  dkLen is known to the attacker if they know the iteration
 149  *          count, and
 150  *      2.  using the wrong dkLen will skew the calibration by an
 151  *          integral factor n = (dkLen / 160).
 152  */
 153
 154 #define CAL_PASSLEN        64
 155 #define CAL_SALTLEN        64
 156 #define CAL_TIME        30000           /* Minimum number of microseconds that
 157                                          * are considered significant.
 158                                          */
 159
 160 /*
 161  * We return the user time in microseconds that c iterations
 162  * of the algorithm take.
 163  */
 164
 165 static int
 166 pkcs5_pbkdf2_time(size_t dkLen, size_t c)
 167 {
 168         struct rusage    start;
 169         struct rusage    end;
 170         int              ret;
 171         u_int8_t        *r = NULL;
 172         u_int8_t         P[CAL_PASSLEN];
 173         u_int8_t         S[CAL_SALTLEN];
 174
 175         (void)getrusage(RUSAGE_SELF, &start);
 176         /* XXX compat flag at end to be removed when _OLD keygen method is */
 177         ret = pkcs5_pbkdf2(&r, dkLen, P, sizeof(P), S, sizeof(S), c, 0);
 178         if (ret)
 179                 return ret;
 180         (void)getrusage(RUSAGE_SELF, &end);
 181         free(r);
 182
 183         return (end.ru_utime.tv_sec - start.ru_utime.tv_sec) * 1000000
 184              + (end.ru_utime.tv_usec - start.ru_utime.tv_usec);
 185 }
 186
 187 int
 188 pkcs5_pbkdf2_calibrate(size_t dkLen, int microseconds)
 189 {
 190         size_t  c;
 191         int     t = 0;
 192         size_t  ret, i;
 193
 194         for (i = 0; i < 5; i++) {
 195                 /*
 196                  * First we get a meaningfully long time by doubling the
 197                  * iteration count until it takes longer than CAL_TIME.  This
 198                  * should take approximately 2 * CAL_TIME.
 199                  */
 200                 for (c = 1;; c *= 2) {
 201                         t = pkcs5_pbkdf2_time(dkLen, c);
 202                         if (t > CAL_TIME)
 203                                 break;
 204                 }
 205
 206                 /* Now that we know that, we scale it. */
 207                 ret = (size_t) ((u_int64_t) c * microseconds / t);
 208
 209                 /*
 210                  * Since it is quite important to not get this wrong,
 211                  * we test the result.
 212                  */
 213
 214                 t = pkcs5_pbkdf2_time(dkLen, ret);
 215
 216                 /* if we are over 5% off, return an error */
 217                 if (abs(microseconds - t) > (microseconds / 20))
 218                         continue;
 219                 return ret;
 220         }
 221         return -1;
 222 }