1 // SPDX-License-Identifier: BSD-2-Clause
2 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
3 *
4 * LibTomCrypt is a library that provides various cryptographic
5 * algorithms in a highly modular and flexible manner.
6 *
7 * The library is free for all purposes without any express
8 * guarantee it works.
9 */
10 #include "tomcrypt_private.h"
11
12 /**
13 @file xcbc_init.c
14 XCBC Support, start an XCBC state
15 */
16
17 #ifdef LTC_XCBC
18
19 /** Initialize XCBC-MAC state
20 @param xcbc [out] XCBC state to initialize
21 @param cipher Index of cipher to use
22 @param key [in] Secret key
23 @param keylen Length of secret key in octets
24 Return CRYPT_OK on success
25 */
xcbc_init(xcbc_state * xcbc,int cipher,const unsigned char * key,unsigned long keylen)26 int xcbc_init(xcbc_state *xcbc, int cipher, const unsigned char *key, unsigned long keylen)
27 {
28 int x, y, err;
29 symmetric_key *skey;
30 unsigned long k1;
31
32 LTC_ARGCHK(xcbc != NULL);
33 LTC_ARGCHK(key != NULL);
34
35 /* schedule the key */
36 if ((err = cipher_is_valid(cipher)) != CRYPT_OK) {
37 return err;
38 }
39
40 #ifdef LTC_FAST
41 if (cipher_descriptor[cipher]->block_length % sizeof(LTC_FAST_TYPE)) {
42 return CRYPT_INVALID_ARG;
43 }
44 #endif
45
46 skey = NULL;
47
48 /* are we in pure XCBC mode with three keys? */
49 if (keylen & LTC_XCBC_PURE) {
50 keylen &= ~LTC_XCBC_PURE;
51
52 if (keylen < 2UL*cipher_descriptor[cipher]->block_length) {
53 return CRYPT_INVALID_ARG;
54 }
55
56 k1 = keylen - 2*cipher_descriptor[cipher]->block_length;
57 XMEMCPY(xcbc->K[0], key, k1);
58 XMEMCPY(xcbc->K[1], key+k1, cipher_descriptor[cipher]->block_length);
59 XMEMCPY(xcbc->K[2], key+k1 + cipher_descriptor[cipher]->block_length, cipher_descriptor[cipher]->block_length);
60 } else {
61 /* use the key expansion */
62 k1 = cipher_descriptor[cipher]->block_length;
63
64 /* schedule the user key */
65 skey = XCALLOC(1, sizeof(*skey));
66 if (skey == NULL) {
67 return CRYPT_MEM;
68 }
69
70 if ((err = cipher_descriptor[cipher]->setup(key, keylen, 0, skey)) != CRYPT_OK) {
71 goto done;
72 }
73
74 /* make the three keys */
75 for (y = 0; y < 3; y++) {
76 for (x = 0; x < cipher_descriptor[cipher]->block_length; x++) {
77 xcbc->K[y][x] = y + 1;
78 }
79 cipher_descriptor[cipher]->ecb_encrypt(xcbc->K[y], xcbc->K[y], skey);
80 }
81 }
82
83 /* setup K1 */
84 err = cipher_descriptor[cipher]->setup(xcbc->K[0], k1, 0, &xcbc->key);
85
86 /* setup struct */
87 zeromem(xcbc->IV, cipher_descriptor[cipher]->block_length);
88 xcbc->blocksize = cipher_descriptor[cipher]->block_length;
89 xcbc->cipher = cipher;
90 xcbc->buflen = 0;
91 done:
92 cipher_descriptor[cipher]->done(skey);
93 if (skey != NULL) {
94 #ifdef LTC_CLEAN_STACK
95 zeromem(skey, sizeof(*skey));
96 #endif
97 XFREE(skey);
98 }
99 return err;
100 }
101
102 #endif
103
104 /* ref: $Format:%D$ */
105 /* git commit: $Format:%H$ */
106 /* commit time: $Format:%ai$ */
107
108