1/* gc-pbkdf2-sha1.c --- Password-Based Key Derivation Function a'la PKCS#5
2 Copyright (C) 2002-2006, 2009-2012 Free Software Foundation, Inc.
3
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 2.1, or (at your option)
7 any later version.
8
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.
13
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/>. */
16
17/* Written by Simon Josefsson. */
18
19#include <config.h>
20
21#include "gc.h"
22
23#include <stdlib.h>
24#include <string.h>
25
26/* Implement PKCS#5 PBKDF2 as per RFC 2898. The PRF to use is hard
27 coded to be HMAC-SHA1. Inputs are the password P of length PLEN,
28 the salt S of length SLEN, the iteration counter C (> 0), and the
29 desired derived output length DKLEN. Output buffer is DK which
30 must have room for at least DKLEN octets. The output buffer will
31 be filled with the derived data. */
32Gc_rc
33gc_pbkdf2_sha1 (const char *P, size_t Plen,
34 const char *S, size_t Slen,
35 unsigned int c,
36 char *DK, size_t dkLen)
37{
38 unsigned int hLen = 20;
39 char U[20];
40 char T[20];
41 unsigned int u;
42 unsigned int l;
43 unsigned int r;
44 unsigned int i;
45 unsigned int k;
46 int rc;
47 char *tmp;
48 size_t tmplen = Slen + 4;
49
50 if (c == 0)
51 return GC_PKCS5_INVALID_ITERATION_COUNT;
52
53 if (dkLen == 0)
54 return GC_PKCS5_INVALID_DERIVED_KEY_LENGTH;
55
56 if (dkLen > 4294967295U)
57 return GC_PKCS5_DERIVED_KEY_TOO_LONG;
58
59 l = ((dkLen - 1) / hLen) + 1;
60 r = dkLen - (l - 1) * hLen;
61
62 tmp = malloc (tmplen);
63 if (tmp == NULL)
64 return GC_MALLOC_ERROR;
65
66 memcpy (tmp, S, Slen);
67
68 for (i = 1; i <= l; i++)
69 {
70 memset (T, 0, hLen);
71
72 for (u = 1; u <= c; u++)
73 {
74 if (u == 1)
75 {
76 tmp[Slen + 0] = (i & 0xff000000) >> 24;
77 tmp[Slen + 1] = (i & 0x00ff0000) >> 16;
78 tmp[Slen + 2] = (i & 0x0000ff00) >> 8;
79 tmp[Slen + 3] = (i & 0x000000ff) >> 0;
80
81 rc = gc_hmac_sha1 (P, Plen, tmp, tmplen, U);
82 }
83 else
84 rc = gc_hmac_sha1 (P, Plen, U, hLen, U);
85
86 if (rc != GC_OK)
87 {
88 free (tmp);
89 return rc;
90 }
91
92 for (k = 0; k < hLen; k++)
93 T[k] ^= U[k];
94 }
95
96 memcpy (DK + (i - 1) * hLen, T, i == l ? r : hLen);
97 }
98
99 free (tmp);
100
101 return GC_OK;
102}
103