2 * Implementation of Password-Based Cryptography as per PKCS#5
3 * Copyright (C) 2002,2003 Simon Josefsson
4 * Copyright (C) 2004 Free Software Foundation
7 * Copyright (C) 2004, Clemens Fruhwirth <clemens@endorphin.org>
8 * Copyright (C) 2009-2012, Red Hat, Inc. All rights reserved.
10 * This file is free software; you can redistribute it and/or
11 * modify it under the terms of the GNU Lesser General Public
12 * License as published by the Free Software Foundation; either
13 * version 2.1 of the License, or (at your option) any later version.
15 * This file is distributed in the hope that it will be useful,
16 * but WITHOUT ANY WARRANTY; without even the implied warranty of
17 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
18 * Lesser General Public License for more details.
20 * You should have received a copy of the GNU Lesser General Public
21 * License along with this file; if not, write to the Free Software
22 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
26 #include <netinet/in.h>
32 #include "crypto_backend.h"
35 static volatile uint64_t __PBKDF2_global_j = 0;
36 static volatile uint64_t __PBKDF2_performance = 0;
41 * PBKDF2 applies a pseudorandom function (see Appendix B.1 for an
42 * example) to derive keys. The length of the derived key is essentially
43 * unbounded. (However, the maximum effective search space for the
44 * derived key may be limited by the structure of the underlying
45 * pseudorandom function. See Appendix B.1 for further discussion.)
46 * PBKDF2 is recommended for new applications.
48 * PBKDF2 (P, S, c, dkLen)
50 * Options: PRF underlying pseudorandom function (hLen
51 * denotes the length in octets of the
52 * pseudorandom function output)
54 * Input: P password, an octet string (ASCII or UTF-8)
55 * S salt, an octet string
56 * c iteration count, a positive integer
57 * dkLen intended length in octets of the derived
58 * key, a positive integer, at most
61 * Output: DK derived key, a dkLen-octet string
64 #define MAX_PRF_BLOCK_LEN 80
66 static int pkcs5_pbkdf2(const char *hash,
67 const char *P, size_t Plen,
68 const char *S, size_t Slen,
69 unsigned int c, unsigned int dkLen,
70 char *DK, int perfcheck)
72 struct crypt_hmac *hmac;
73 char U[MAX_PRF_BLOCK_LEN];
74 char T[MAX_PRF_BLOCK_LEN];
75 int i, k, rc = -EINVAL;
76 unsigned int u, hLen, l, r;
77 size_t tmplen = Slen + 4;
84 hLen = crypt_hmac_size(hash);
85 if (hLen == 0 || hLen > MAX_PRF_BLOCK_LEN)
98 * 1. If dkLen > (2^32 - 1) * hLen, output "derived key too long" and
102 if (dkLen > 4294967295U)
106 * 2. Let l be the number of hLen-octet blocks in the derived key,
107 * rounding up, and let r be the number of octets in the last
110 * l = CEIL (dkLen / hLen) ,
111 * r = dkLen - (l - 1) * hLen .
113 * Here, CEIL (x) is the "ceiling" function, i.e. the smallest
114 * integer greater than, or equal to, x.
120 r = dkLen - (l - 1) * hLen;
123 * 3. For each block of the derived key apply the function F defined
124 * below to the password P, the salt S, the iteration count c, and
125 * the block index to compute the block:
127 * T_1 = F (P, S, c, 1) ,
128 * T_2 = F (P, S, c, 2) ,
130 * T_l = F (P, S, c, l) ,
132 * where the function F is defined as the exclusive-or sum of the
133 * first c iterates of the underlying pseudorandom function PRF
134 * applied to the password P and the concatenation of the salt S
135 * and the block index i:
137 * F (P, S, c, i) = U_1 \xor U_2 \xor ... \xor U_c
141 * U_1 = PRF (P, S || INT (i)) ,
142 * U_2 = PRF (P, U_1) ,
144 * U_c = PRF (P, U_{c-1}) .
146 * Here, INT (i) is a four-octet encoding of the integer i, most
147 * significant octet first.
149 * 4. Concatenate the blocks and extract the first dkLen octets to
150 * produce a derived key DK:
152 * DK = T_1 || T_2 || ... || T_l<0..r-1>
154 * 5. Output the derived key DK.
156 * Note. The construction of the function F follows a "belt-and-
157 * suspenders" approach. The iterates U_i are computed recursively to
158 * remove a degree of parallelism from an opponent; they are exclusive-
159 * ored together to reduce concerns about the recursion degenerating
160 * into a small set of values.
164 if (crypt_hmac_init(&hmac, hash, P, Plen))
167 for (i = 1; (uint) i <= l; i++) {
170 for (u = 1; u <= c ; u++) {
172 memcpy(tmp, S, Slen);
173 tmp[Slen + 0] = (i & 0xff000000) >> 24;
174 tmp[Slen + 1] = (i & 0x00ff0000) >> 16;
175 tmp[Slen + 2] = (i & 0x0000ff00) >> 8;
176 tmp[Slen + 3] = (i & 0x000000ff) >> 0;
178 if (crypt_hmac_write(hmac, tmp, tmplen))
181 if (crypt_hmac_write(hmac, U, hLen))
185 if (crypt_hmac_final(hmac, U, hLen))
188 for (k = 0; (uint) k < hLen; k++)
191 if (perfcheck && __PBKDF2_performance) {
200 memcpy(DK + (i - 1) * hLen, T, (uint) i == l ? r : hLen);
204 crypt_hmac_destroy(hmac);
208 int PBKDF2_HMAC(const char *hash,
209 const char *password, size_t passwordLen,
210 const char *salt, size_t saltLen, unsigned int iterations,
211 char *dKey, size_t dKeyLen)
213 return pkcs5_pbkdf2(hash, password, passwordLen, salt, saltLen,
214 iterations, (unsigned int)dKeyLen, dKey, 0);
217 int PBKDF2_HMAC_ready(const char *hash)
219 if (crypt_hmac_size(hash) < 20)
225 static void sigvtalarm(int foo __attribute__((unused)))
227 __PBKDF2_performance = __PBKDF2_global_j;
230 /* This code benchmarks PBKDF2 and returns iterations/second using wth specified hash */
231 int PBKDF2_performance_check(const char *hash, uint64_t *iter)
237 if (__PBKDF2_global_j)
240 if (PBKDF2_HMAC_ready(hash) < 0)
243 /* If crypto backend is not implemented in userspace,
244 * but uses some kernel part, we must measure also time
245 * spent in kernel. */
246 if (crypt_backend_flags() & CRYPT_BACKEND_KERNEL) {
247 timer_type = ITIMER_PROF;
248 signal(SIGPROF,sigvtalarm);
250 timer_type = ITIMER_VIRTUAL;
251 signal(SIGVTALRM,sigvtalarm);
254 it.it_interval.tv_usec = 0;
255 it.it_interval.tv_sec = 0;
256 it.it_value.tv_usec = 0;
257 it.it_value.tv_sec = 1;
258 if (setitimer(timer_type, &it, NULL) < 0)
261 r = pkcs5_pbkdf2(hash, "foo", 3, "bar", 3, ~(0U), 1, &buf, 1);
263 *iter = __PBKDF2_performance;
264 __PBKDF2_global_j = 0;
265 __PBKDF2_performance = 0;