gost_keywrap.c revision 296341 
1/**********************************************************************
2 *                          keywrap.c                                 *
3 *             Copyright (c) 2005-2006 Cryptocom LTD                  *
4 *         This file is distributed under the same license as OpenSSL *
5 *                                                                    *
6 * Implementation of CryptoPro key wrap algorithm, as defined in      *
7 *               RFC 4357 p 6.3 and 6.4                               *
8 *                  Doesn't need OpenSSL                              *
9 **********************************************************************/
10#include <string.h>
11#include "gost89.h"
12#include "gost_keywrap.h"
13
14/*-
15 * Diversifies key using random UserKey Material
16 * Implements RFC 4357 p 6.5 key diversification algorithm
17 *
18 * inputKey - 32byte key to be diversified
19 * ukm - 8byte user key material
20 * outputKey - 32byte buffer to store diversified key
21 *
22 */
23void keyDiversifyCryptoPro(gost_ctx * ctx, const unsigned char *inputKey,
24                           const unsigned char *ukm, unsigned char *outputKey)
25{
26
27    u4 k, s1, s2;
28    int i, j, mask;
29    unsigned char S[8];
30    memcpy(outputKey, inputKey, 32);
31    for (i = 0; i < 8; i++) {
32        /* Make array of integers from key */
33        /* Compute IV S */
34        s1 = 0, s2 = 0;
35        for (j = 0, mask = 1; j < 8; j++, mask <<= 1) {
36            k = ((u4) outputKey[4 * j]) | (outputKey[4 * j + 1] << 8) |
37                (outputKey[4 * j + 2] << 16) | (outputKey[4 * j + 3] << 24);
38            if (mask & ukm[i]) {
39                s1 += k;
40            } else {
41                s2 += k;
42            }
43        }
44        S[0] = (unsigned char)(s1 & 0xff);
45        S[1] = (unsigned char)((s1 >> 8) & 0xff);
46        S[2] = (unsigned char)((s1 >> 16) & 0xff);
47        S[3] = (unsigned char)((s1 >> 24) & 0xff);
48        S[4] = (unsigned char)(s2 & 0xff);
49        S[5] = (unsigned char)((s2 >> 8) & 0xff);
50        S[6] = (unsigned char)((s2 >> 16) & 0xff);
51        S[7] = (unsigned char)((s2 >> 24) & 0xff);
52        gost_key(ctx, outputKey);
53        gost_enc_cfb(ctx, S, outputKey, outputKey, 4);
54    }
55}
56
57/*-
58 * Wraps key using RFC 4357 6.3
59 * ctx - gost encryption context, initialized with some S-boxes
60 * keyExchangeKey (KEK) 32-byte (256-bit) shared key
61 * ukm - 8 byte (64 bit) user key material,
62 * sessionKey - 32-byte (256-bit) key to be wrapped
63 * wrappedKey - 44-byte buffer to store wrapped key
64 */
65
66int keyWrapCryptoPro(gost_ctx * ctx, const unsigned char *keyExchangeKey,
67                     const unsigned char *ukm,
68                     const unsigned char *sessionKey,
69                     unsigned char *wrappedKey)
70{
71    unsigned char kek_ukm[32];
72    keyDiversifyCryptoPro(ctx, keyExchangeKey, ukm, kek_ukm);
73    gost_key(ctx, kek_ukm);
74    memcpy(wrappedKey, ukm, 8);
75    gost_enc(ctx, sessionKey, wrappedKey + 8, 4);
76    gost_mac_iv(ctx, 32, ukm, sessionKey, 32, wrappedKey + 40);
77    return 1;
78}
79
80/*-
81 * Unwraps key using RFC 4357 6.4
82 * ctx - gost encryption context, initialized with some S-boxes
83 * keyExchangeKey 32-byte shared key
84 * wrappedKey  44 byte key to be unwrapped (concatenation of 8-byte UKM,
85 * 32 byte  encrypted key and 4 byte MAC
86 *
87 * sessionKEy - 32byte buffer to store sessionKey in
88 * Returns 1 if key is decrypted successfully, and 0 if MAC doesn't match
89 */
90
91int keyUnwrapCryptoPro(gost_ctx * ctx, const unsigned char *keyExchangeKey,
92                       const unsigned char *wrappedKey,
93                       unsigned char *sessionKey)
94{
95    unsigned char kek_ukm[32], cek_mac[4];
96    keyDiversifyCryptoPro(ctx, keyExchangeKey, wrappedKey
97                          /* First 8 bytes of wrapped Key is ukm */
98                          , kek_ukm);
99    gost_key(ctx, kek_ukm);
100    gost_dec(ctx, wrappedKey + 8, sessionKey, 4);
101    gost_mac_iv(ctx, 32, wrappedKey, sessionKey, 32, cek_mac);
102    if (memcmp(cek_mac, wrappedKey + 40, 4)) {
103        return 0;
104    }
105    return 1;
106}
107