1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis */
2 /* SPDX-License-Identifier: Unlicense */
3 #include "tomcrypt_private.h"
4
5 /**
6 @file xcbc_init.c
7 XCBC Support, start an XCBC state
8 */
9
10 #ifdef LTC_XCBC
11
12 /** Initialize XCBC-MAC state
13 @param xcbc [out] XCBC state to initialize
14 @param cipher Index of cipher to use
15 @param key [in] Secret key
16 @param keylen Length of secret key in octets
17 Return CRYPT_OK on success
18 */
xcbc_init(xcbc_state * xcbc,int cipher,const unsigned char * key,unsigned long keylen)19 int xcbc_init(xcbc_state *xcbc, int cipher, const unsigned char *key, unsigned long keylen)
20 {
21 int x, y, err;
22 symmetric_key *skey;
23 unsigned long k1;
24
25 LTC_ARGCHK(xcbc != NULL);
26 LTC_ARGCHK(key != NULL);
27
28 /* schedule the key */
29 if ((err = cipher_is_valid(cipher)) != CRYPT_OK) {
30 return err;
31 }
32
33 #ifdef LTC_FAST
34 if (cipher_descriptor[cipher]->block_length % sizeof(LTC_FAST_TYPE)) {
35 return CRYPT_INVALID_ARG;
36 }
37 #endif
38
39 skey = NULL;
40
41 /* are we in pure XCBC mode with three keys? */
42 if (keylen & LTC_XCBC_PURE) {
43 keylen &= ~LTC_XCBC_PURE;
44
45 if (keylen < 2UL*cipher_descriptor[cipher]->block_length) {
46 return CRYPT_INVALID_ARG;
47 }
48
49 k1 = keylen - 2*cipher_descriptor[cipher]->block_length;
50 XMEMCPY(xcbc->K[0], key, k1);
51 XMEMCPY(xcbc->K[1], key+k1, cipher_descriptor[cipher]->block_length);
52 XMEMCPY(xcbc->K[2], key+k1 + cipher_descriptor[cipher]->block_length, cipher_descriptor[cipher]->block_length);
53 } else {
54 /* use the key expansion */
55 k1 = cipher_descriptor[cipher]->block_length;
56
57 /* schedule the user key */
58 skey = XCALLOC(1, sizeof(*skey));
59 if (skey == NULL) {
60 return CRYPT_MEM;
61 }
62
63 if ((err = cipher_descriptor[cipher]->setup(key, keylen, 0, skey)) != CRYPT_OK) {
64 goto done;
65 }
66
67 /* make the three keys */
68 for (y = 0; y < 3; y++) {
69 for (x = 0; x < cipher_descriptor[cipher]->block_length; x++) {
70 xcbc->K[y][x] = y + 1;
71 }
72 cipher_descriptor[cipher]->ecb_encrypt(xcbc->K[y], xcbc->K[y], skey);
73 }
74 }
75
76 /* setup K1 */
77 err = cipher_descriptor[cipher]->setup(xcbc->K[0], k1, 0, &xcbc->key);
78
79 /* setup struct */
80 zeromem(xcbc->IV, cipher_descriptor[cipher]->block_length);
81 xcbc->blocksize = cipher_descriptor[cipher]->block_length;
82 xcbc->cipher = cipher;
83 xcbc->buflen = 0;
84 done:
85 cipher_descriptor[cipher]->done(skey);
86 if (skey != NULL) {
87 #ifdef LTC_CLEAN_STACK
88 zeromem(skey, sizeof(*skey));
89 #endif
90 XFREE(skey);
91 }
92 return err;
93 }
94
95 #endif
96
97