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 * Tom St Denis, tomstdenis@gmail.com, http://libtomcrypt.com
10 */
11#include "tomcrypt.h"
12
13/**
14  @file hmac_init.c
15  HMAC support, initialize state, Tom St Denis/Dobes Vandermeer
16*/
17
18#ifdef LTC_HMAC
19
20#define HMAC_BLOCKSIZE hash_descriptor[hash].blocksize
21
22/**
23   Initialize an HMAC context.
24   @param hmac     The HMAC state
25   @param hash     The index of the hash you want to use
26   @param key      The secret key
27   @param keylen   The length of the secret key (octets)
28   @return CRYPT_OK if successful
29*/
30int hmac_init(hmac_state *hmac, int hash, const unsigned char *key, unsigned long keylen)
31{
32    unsigned char *buf;
33    unsigned long hashsize;
34    unsigned long i, z;
35    int err;
36
37    LTC_ARGCHK(hmac != NULL);
38    LTC_ARGCHK(key  != NULL);
39
40    /* valid hash? */
41    if ((err = hash_is_valid(hash)) != CRYPT_OK) {
42        return err;
43    }
44    hmac->hash = hash;
45    hashsize   = hash_descriptor[hash].hashsize;
46
47    /* valid key length? */
48    if (keylen == 0) {
49        return CRYPT_INVALID_KEYSIZE;
50    }
51
52    /* allocate ram for buf */
53    buf = XMALLOC(HMAC_BLOCKSIZE);
54    if (buf == NULL) {
55       return CRYPT_MEM;
56    }
57
58    /* allocate memory for key */
59    hmac->key = XMALLOC(HMAC_BLOCKSIZE);
60    if (hmac->key == NULL) {
61       XFREE(buf);
62       return CRYPT_MEM;
63    }
64
65    /* (1) make sure we have a large enough key */
66    if(keylen > HMAC_BLOCKSIZE) {
67        z = HMAC_BLOCKSIZE;
68        if ((err = hash_memory(hash, key, keylen, hmac->key, &z)) != CRYPT_OK) {
69           goto LBL_ERR;
70        }
71        if(hashsize < HMAC_BLOCKSIZE) {
72            zeromem((hmac->key) + hashsize, (size_t)(HMAC_BLOCKSIZE - hashsize));
73        }
74        keylen = hashsize;
75    } else {
76        XMEMCPY(hmac->key, key, (size_t)keylen);
77        if(keylen < HMAC_BLOCKSIZE) {
78            zeromem((hmac->key) + keylen, (size_t)(HMAC_BLOCKSIZE - keylen));
79        }
80    }
81
82    /* Create the initial vector for step (3) */
83    for(i=0; i < HMAC_BLOCKSIZE;   i++) {
84       buf[i] = hmac->key[i] ^ 0x36;
85    }
86
87    /* Pre-pend that to the hash data */
88    if ((err = hash_descriptor[hash].init(&hmac->md)) != CRYPT_OK) {
89       goto LBL_ERR;
90    }
91
92    if ((err = hash_descriptor[hash].process(&hmac->md, buf, HMAC_BLOCKSIZE)) != CRYPT_OK) {
93       goto LBL_ERR;
94    }
95    goto done;
96LBL_ERR:
97    /* free the key since we failed */
98    XFREE(hmac->key);
99done:
100#ifdef LTC_CLEAN_STACK
101   zeromem(buf, HMAC_BLOCKSIZE);
102#endif
103
104   XFREE(buf);
105   return err;
106}
107
108#endif
109
110/* $Source: /cvs/libtom/libtomcrypt/src/mac/hmac/hmac_init.c,v $ */
111/* $Revision: 1.5 $ */
112/* $Date: 2006/11/03 00:39:49 $ */
113