source: trunk/third/gaim-encryption/nss_mgf1.c @ 22512

Revision 22512, 2.9 KB checked in by ghudson, 18 years ago (diff)
This commit was generated by cvs2svn to compensate for changes in r22511, which included commits to RCS files with non-trunk default branches.
Line 
1/*
2 * Gaim-Encryption MGF-1 Mask Generation Function (see PKCS#1 v2.1)
3 *
4 * Copyright (C) 2003 William Tompkins
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
10 *
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14 * GNU General Public License for more details.
15 *
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, write to the Free Software
18 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
19 */
20
21#include <pk11func.h>
22
23/* for g_assert; PORT_Assert seems disabled... */
24#include <glib.h>
25
26#include "nss_mgf1.h"
27
28static const SECOidTag Hash_OID = SEC_OID_SHA1;
29
30/* Mask Generation function:  From a seed, produce a variably sized mask, and */
31/*   XOR it with the maskee.                                                  */
32
33/* Note- this is an inefficient implementation, as we repeatedly hash the     */
34/*         seed.  If we saved the intermediate context, we'd probably save    */
35/*         a bunch of time.  But, the NSS exported interface doesn't let us   */
36/*         do that easily, so we don't.                                       */
37
38static void memxor (unsigned char* a, unsigned char* b, int len) {
39   while (len-- > 0) {
40      *a++ ^= *b++;
41   }
42}
43
44int mgf1(unsigned char* maskee, unsigned int maskee_len,
45         unsigned char* seed, unsigned seed_len) {
46   
47   unsigned char* extended_seed = PORT_Alloc(seed_len + 4);
48   unsigned char* hash_out;
49   unsigned int hash_len;
50
51   unsigned long int counter = 0;
52   unsigned int counter_pos = seed_len;
53
54   unsigned int maskee_pos = 0;
55   unsigned int cur_block_size;
56
57   SECStatus rv;
58
59   hash_len = 20;
60
61   hash_out = PORT_Alloc(hash_len);
62   PORT_Memcpy(extended_seed, seed, seed_len);
63   
64   while (maskee_pos < maskee_len) {
65      /* Store counter at counter_pos, msb first */
66      extended_seed[counter_pos] = (unsigned char) ((counter >> 24) & 0xff);
67      extended_seed[counter_pos+1] = (unsigned char) ((counter >> 16) & 0xff);
68      extended_seed[counter_pos+2] = (unsigned char) ((counter >> 8) & 0xff);
69      extended_seed[counter_pos+3] = (unsigned char) (counter & 0xff);
70
71      rv = PK11_HashBuf(Hash_OID, hash_out, extended_seed, seed_len + 4);
72      g_assert(rv == SECSuccess);
73
74      cur_block_size = (maskee_len - maskee_pos);
75      if (cur_block_size > hash_len) cur_block_size = hash_len;
76
77      memxor(maskee + maskee_pos, hash_out, cur_block_size);
78      maskee_pos += cur_block_size;
79     
80      ++counter;
81   }
82
83   PORT_ZFree(extended_seed, seed_len+4);
84   PORT_ZFree(hash_out, hash_len);
85   return 1;
86}
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