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_done.c
15  HMAC support, terminate stream, Tom St Denis/Dobes Vandermeer
16*/
17
18#ifdef LTC_HMAC
19
20#define HMAC_BLOCKSIZE hash_descriptor[hash].blocksize
21
22/**
23   Terminate an HMAC session
24   @param hmac    The HMAC state
25   @param out     [out] The destination of the HMAC authentication tag
26   @param outlen  [in/out]  The max size and resulting size of the HMAC authentication tag
27   @return CRYPT_OK if successful
28*/
29int hmac_done(hmac_state *hmac, unsigned char *out, unsigned long *outlen)
30{
31    unsigned char *buf, *isha;
32    unsigned long hashsize, i;
33    int hash, err;
34
35    LTC_ARGCHK(hmac  != NULL);
36    LTC_ARGCHK(out   != NULL);
37
38    /* test hash */
39    hash = hmac->hash;
40    if((err = hash_is_valid(hash)) != CRYPT_OK) {
41        return err;
42    }
43
44    /* get the hash message digest size */
45    hashsize = hash_descriptor[hash].hashsize;
46
47    /* allocate buffers */
48    buf  = XMALLOC(HMAC_BLOCKSIZE);
49    isha = XMALLOC(hashsize);
50    if (buf == NULL || isha == NULL) {
51       if (buf != NULL) {
52          XFREE(buf);
53       }
54       if (isha != NULL) {
55          XFREE(isha);
56       }
57       return CRYPT_MEM;
58    }
59
60    /* Get the hash of the first HMAC vector plus the data */
61    if ((err = hash_descriptor[hash].done(&hmac->md, isha)) != CRYPT_OK) {
62       goto LBL_ERR;
63    }
64
65    /* Create the second HMAC vector vector for step (3) */
66    for(i=0; i < HMAC_BLOCKSIZE; i++) {
67        buf[i] = hmac->key[i] ^ 0x5C;
68    }
69
70    /* Now calculate the "outer" hash for step (5), (6), and (7) */
71    if ((err = hash_descriptor[hash].init(&hmac->md)) != CRYPT_OK) {
72       goto LBL_ERR;
73    }
74    if ((err = hash_descriptor[hash].process(&hmac->md, buf, HMAC_BLOCKSIZE)) != CRYPT_OK) {
75       goto LBL_ERR;
76    }
77    if ((err = hash_descriptor[hash].process(&hmac->md, isha, hashsize)) != CRYPT_OK) {
78       goto LBL_ERR;
79    }
80    if ((err = hash_descriptor[hash].done(&hmac->md, buf)) != CRYPT_OK) {
81       goto LBL_ERR;
82    }
83
84    /* copy to output  */
85    for (i = 0; i < hashsize && i < *outlen; i++) {
86        out[i] = buf[i];
87    }
88    *outlen = i;
89
90    err = CRYPT_OK;
91LBL_ERR:
92    XFREE(hmac->key);
93#ifdef LTC_CLEAN_STACK
94    zeromem(isha, hashsize);
95    zeromem(buf,  hashsize);
96    zeromem(hmac, sizeof(*hmac));
97#endif
98
99    XFREE(isha);
100    XFREE(buf);
101
102    return err;
103}
104
105#endif
106
107/* $Source: /cvs/libtom/libtomcrypt/src/mac/hmac/hmac_done.c,v $ */
108/* $Revision: 1.5 $ */
109/* $Date: 2006/11/03 00:39:49 $ */
110