cleaned up errno handling.
[gnutls.git] / lib / x509 / pbkdf2-sha1.c
blob7d7b85954ad6a36b4940a40c5923b8e831f1bb04
1 /* gc-pbkdf2-sha1.c --- Password-Based Key Derivation Function a'la PKCS#5
2 Copyright (C) 2002-2012 Free Software Foundation, Inc.
4 This program is free software; you can redistribute it and/or modify
5 it under the terms of the GNU Lesser General Public License as published by
6 the Free Software Foundation; either version 3, or (at your option)
7 any later version.
9 This program is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 GNU Lesser General Public License for more details.
14 You should have received a copy of the GNU Lesser General Public License
15 along with this program. If not, see <http://www.gnu.org/licenses/>
19 /* Written by Simon Josefsson. The comments in this file are taken
20 from RFC 2898. */
22 #include <gnutls_int.h>
23 #include <gnutls_datum.h>
24 #include <gnutls_errors.h>
25 #include <gnutls_hash_int.h>
26 #include <pbkdf2-sha1.h>
29 * 5.2 PBKDF2
31 * PBKDF2 applies a pseudorandom function (see Appendix B.1 for an
32 * example) to derive keys. The length of the derived key is essentially
33 * unbounded. (However, the maximum effective search space for the
34 * derived key may be limited by the structure of the underlying
35 * pseudorandom function. See Appendix B.1 for further discussion.)
36 * PBKDF2 is recommended for new applications.
38 * PBKDF2 (P, S, c, dkLen)
40 * Options: PRF underlying pseudorandom function (hLen
41 * denotes the length in octets of the
42 * pseudorandom function output)
44 * Input: P password, an octet string (ASCII or UTF-8)
45 * S salt, an octet string
46 * c iteration count, a positive integer
47 * dkLen intended length in octets of the derived
48 * key, a positive integer, at most
49 * (2^32 - 1) * hLen
51 * Output: DK derived key, a dkLen-octet string
54 int
55 _gnutls_pbkdf2_sha1 (const char *P, size_t Plen,
56 const unsigned char *S, size_t Slen,
57 unsigned int c, unsigned char *DK, size_t dkLen)
59 unsigned int hLen = 20;
60 char U[20];
61 char T[20];
62 unsigned int u;
63 unsigned int l;
64 unsigned int r;
65 unsigned int i;
66 unsigned int k;
67 int rc;
68 char *tmp;
69 size_t tmplen = Slen + 4;
71 if (c == 0)
73 gnutls_assert ();
74 return GNUTLS_E_INVALID_REQUEST;
77 if (dkLen == 0)
79 gnutls_assert ();
80 return GNUTLS_E_INVALID_REQUEST;
84 * Steps:
86 * 1. If dkLen > (2^32 - 1) * hLen, output "derived key too long" and
87 * stop.
90 if (dkLen > 4294967295U)
92 gnutls_assert ();
93 return GNUTLS_E_INVALID_REQUEST;
97 * 2. Let l be the number of hLen-octet blocks in the derived key,
98 * rounding up, and let r be the number of octets in the last
99 * block:
101 * l = CEIL (dkLen / hLen) ,
102 * r = dkLen - (l - 1) * hLen .
104 * Here, CEIL (x) is the "ceiling" function, i.e. the smallest
105 * integer greater than, or equal to, x.
108 l = ((dkLen - 1) / hLen) + 1;
109 r = dkLen - (l - 1) * hLen;
112 * 3. For each block of the derived key apply the function F defined
113 * below to the password P, the salt S, the iteration count c, and
114 * the block index to compute the block:
116 * T_1 = F (P, S, c, 1) ,
117 * T_2 = F (P, S, c, 2) ,
118 * ...
119 * T_l = F (P, S, c, l) ,
121 * where the function F is defined as the exclusive-or sum of the
122 * first c iterates of the underlying pseudorandom function PRF
123 * applied to the password P and the concatenation of the salt S
124 * and the block index i:
126 * F (P, S, c, i) = U_1 \xor U_2 \xor ... \xor U_c
128 * where
130 * U_1 = PRF (P, S || INT (i)) ,
131 * U_2 = PRF (P, U_1) ,
132 * ...
133 * U_c = PRF (P, U_{c-1}) .
135 * Here, INT (i) is a four-octet encoding of the integer i, most
136 * significant octet first.
138 * 4. Concatenate the blocks and extract the first dkLen octets to
139 * produce a derived key DK:
141 * DK = T_1 || T_2 || ... || T_l<0..r-1>
143 * 5. Output the derived key DK.
145 * Note. The construction of the function F follows a "belt-and-
146 * suspenders" approach. The iterates U_i are computed recursively to
147 * remove a degree of parallelism from an opponent; they are exclusive-
148 * ored together to reduce concerns about the recursion degenerating
149 * into a small set of values.
153 tmp = gnutls_malloc (tmplen);
154 if (tmp == NULL)
156 gnutls_assert ();
157 return GNUTLS_E_MEMORY_ERROR;
160 memcpy (tmp, S, Slen);
162 for (i = 1; i <= l; i++)
164 memset (T, 0, hLen);
166 for (u = 1; u <= c; u++)
168 if (u == 1)
170 tmp[Slen + 0] = (i & 0xff000000) >> 24;
171 tmp[Slen + 1] = (i & 0x00ff0000) >> 16;
172 tmp[Slen + 2] = (i & 0x0000ff00) >> 8;
173 tmp[Slen + 3] = (i & 0x000000ff) >> 0;
175 rc =
176 _gnutls_hmac_fast (GNUTLS_MAC_SHA1, P, Plen, tmp, tmplen, U);
178 else
179 rc = _gnutls_hmac_fast (GNUTLS_MAC_SHA1, P, Plen, U, hLen, U);
181 if (rc < 0)
183 gnutls_free (tmp);
184 return rc;
187 for (k = 0; k < hLen; k++)
188 T[k] ^= U[k];
191 memcpy (DK + (i - 1) * hLen, T, i == l ? r : hLen);
194 gnutls_free (tmp);
196 return 0;