1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
2 *
3 * LibTomCrypt is a library that provides various cryptographic
4 * algorithms in a highly modular and flexible manner.
5 *
6 * The library is free for all purposes without any express
7 * guarantee it works.
8 */
9 #include "tomcrypt.h"
10
11 /**
12 @file hmac_init.c
13 HMAC support, initialize state, Tom St Denis/Dobes Vandermeer
14 */
15
16 #ifdef LTC_HMAC
17
18 #define LTC_HMAC_BLOCKSIZE hash_descriptor[hash].blocksize
19
20 /**
21 Initialize an HMAC context.
22 @param hmac The HMAC state
23 @param hash The index of the hash you want to use
24 @param key The secret key
25 @param keylen The length of the secret key (octets)
26 @return CRYPT_OK if successful
27 */
hmac_init(hmac_state * hmac,int hash,const unsigned char * key,unsigned long keylen)28 int hmac_init(hmac_state *hmac, int hash, const unsigned char *key, unsigned long keylen)
29 {
30 unsigned char *buf;
31 unsigned long hashsize;
32 unsigned long i, z;
33 int err;
34
35 LTC_ARGCHK(hmac != NULL);
36 LTC_ARGCHK(key != NULL);
37
38 /* valid hash? */
39 if ((err = hash_is_valid(hash)) != CRYPT_OK) {
40 return err;
41 }
42 hmac->hash = hash;
43 hashsize = hash_descriptor[hash].hashsize;
44
45 /* valid key length? */
46 if (keylen == 0) {
47 return CRYPT_INVALID_KEYSIZE;
48 }
49
50 /* allocate ram for buf */
51 buf = XMALLOC(LTC_HMAC_BLOCKSIZE);
52 if (buf == NULL) {
53 return CRYPT_MEM;
54 }
55
56 /* allocate memory for key */
57 hmac->key = XMALLOC(LTC_HMAC_BLOCKSIZE);
58 if (hmac->key == NULL) {
59 XFREE(buf);
60 return CRYPT_MEM;
61 }
62
63 /* (1) make sure we have a large enough key */
64 if(keylen > LTC_HMAC_BLOCKSIZE) {
65 z = LTC_HMAC_BLOCKSIZE;
66 if ((err = hash_memory(hash, key, keylen, hmac->key, &z)) != CRYPT_OK) {
67 goto LBL_ERR;
68 }
69 keylen = hashsize;
70 } else {
71 XMEMCPY(hmac->key, key, (size_t)keylen);
72 }
73
74 if(keylen < LTC_HMAC_BLOCKSIZE) {
75 zeromem((hmac->key) + keylen, (size_t)(LTC_HMAC_BLOCKSIZE - keylen));
76 }
77
78 /* Create the initialization vector for step (3) */
79 for(i=0; i < LTC_HMAC_BLOCKSIZE; i++) {
80 buf[i] = hmac->key[i] ^ 0x36;
81 }
82
83 /* Pre-pend that to the hash data */
84 if ((err = hash_descriptor[hash].init(&hmac->md)) != CRYPT_OK) {
85 goto LBL_ERR;
86 }
87
88 if ((err = hash_descriptor[hash].process(&hmac->md, buf, LTC_HMAC_BLOCKSIZE)) != CRYPT_OK) {
89 goto LBL_ERR;
90 }
91 goto done;
92 LBL_ERR:
93 /* free the key since we failed */
94 XFREE(hmac->key);
95 done:
96 #ifdef LTC_CLEAN_STACK
97 zeromem(buf, LTC_HMAC_BLOCKSIZE);
98 #endif
99
100 XFREE(buf);
101 return err;
102 }
103
104 #endif
105
106 /* ref: HEAD -> master, tag: v1.18.1 */
107 /* git commit: e08fd8630f9d9771226466877064055ee7e863d0 */
108 /* commit time: 2018-01-22 11:02:57 +0100 */
109