1/*
2 * hmac.c
3 *
4 * implementation of hmac auth_type_t
5 *
6 * David A. McGrew
7 * Cisco Systems, Inc.
8 */
9/*
10 *
11 * Copyright(c) 2001-2006 Cisco Systems, Inc.
12 * All rights reserved.
13 *
14 * Redistribution and use in source and binary forms, with or without
15 * modification, are permitted provided that the following conditions
16 * are met:
17 *
18 *   Redistributions of source code must retain the above copyright
19 *   notice, this list of conditions and the following disclaimer.
20 *
21 *   Redistributions in binary form must reproduce the above
22 *   copyright notice, this list of conditions and the following
23 *   disclaimer in the documentation and/or other materials provided
24 *   with the distribution.
25 *
26 *   Neither the name of the Cisco Systems, Inc. nor the names of its
27 *   contributors may be used to endorse or promote products derived
28 *   from this software without specific prior written permission.
29 *
30 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
31 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
32 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
33 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
34 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
35 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
36 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
37 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
38 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
39 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
40 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
41 * OF THE POSSIBILITY OF SUCH DAMAGE.
42 *
43 */
44
45#include "hmac.h"
46#include "alloc.h"
47
48/* the debug module for authentiation */
49
50debug_module_t mod_hmac = {
51  0,                  /* debugging is off by default */
52  "hmac sha-1"        /* printable name for module   */
53};
54
55
56err_status_t
57hmac_alloc(auth_t **a, int key_len, int out_len) {
58  extern auth_type_t hmac;
59  uint8_t *pointer;
60
61  debug_print(mod_hmac, "allocating auth func with key length %d", key_len);
62  debug_print(mod_hmac, "                          tag length %d", out_len);
63
64  /*
65   * check key length - note that we don't support keys larger
66   * than 20 bytes yet
67   */
68  if (key_len > 20)
69    return err_status_bad_param;
70
71  /* check output length - should be less than 20 bytes */
72  if (out_len > 20)
73    return err_status_bad_param;
74
75  /* allocate memory for auth and hmac_ctx_t structures */
76  pointer = (uint8_t*)crypto_alloc(sizeof(hmac_ctx_t) + sizeof(auth_t));
77  if (pointer == NULL)
78    return err_status_alloc_fail;
79
80  /* set pointers */
81  *a = (auth_t *)pointer;
82  (*a)->type = &hmac;
83  (*a)->state = pointer + sizeof(auth_t);
84  (*a)->out_len = out_len;
85  (*a)->key_len = key_len;
86  (*a)->prefix_len = 0;
87
88  /* increment global count of all hmac uses */
89  hmac.ref_count++;
90
91  return err_status_ok;
92}
93
94err_status_t
95hmac_dealloc(auth_t *a) {
96  extern auth_type_t hmac;
97
98  /* zeroize entire state*/
99  octet_string_set_to_zero((uint8_t *)a,
100			   sizeof(hmac_ctx_t) + sizeof(auth_t));
101
102  /* free memory */
103  crypto_free(a);
104
105  /* decrement global count of all hmac uses */
106  hmac.ref_count--;
107
108  return err_status_ok;
109}
110
111err_status_t
112hmac_init(hmac_ctx_t *state, const uint8_t *key, int key_len) {
113  int i;
114  uint8_t ipad[64];
115
116    /*
117   * check key length - note that we don't support keys larger
118   * than 20 bytes yet
119   */
120  if (key_len > 20)
121    return err_status_bad_param;
122
123  /*
124   * set values of ipad and opad by exoring the key into the
125   * appropriate constant values
126   */
127  for (i=0; i < key_len; i++) {
128    ipad[i] = key[i] ^ 0x36;
129    state->opad[i] = key[i] ^ 0x5c;
130  }
131  /* set the rest of ipad, opad to constant values */
132  for (   ; i < 64; i++) {
133    ipad[i] = 0x36;
134    ((uint8_t *)state->opad)[i] = 0x5c;
135  }
136
137  debug_print(mod_hmac, "ipad: %s", octet_string_hex_string(ipad, 64));
138
139  /* initialize sha1 context */
140  sha1_init(&state->init_ctx);
141
142  /* hash ipad ^ key */
143  sha1_update(&state->init_ctx, ipad, 64);
144  memcpy(&state->ctx, &state->init_ctx, sizeof(sha1_ctx_t));
145
146  return err_status_ok;
147}
148
149err_status_t
150hmac_start(hmac_ctx_t *state) {
151
152  memcpy(&state->ctx, &state->init_ctx, sizeof(sha1_ctx_t));
153
154  return err_status_ok;
155}
156
157err_status_t
158hmac_update(hmac_ctx_t *state, const uint8_t *message, int msg_octets) {
159
160  debug_print(mod_hmac, "input: %s",
161	      octet_string_hex_string(message, msg_octets));
162
163  /* hash message into sha1 context */
164  sha1_update(&state->ctx, message, msg_octets);
165
166  return err_status_ok;
167}
168
169err_status_t
170hmac_compute(hmac_ctx_t *state, const void *message,
171	     int msg_octets, int tag_len, uint8_t *result) {
172  uint32_t hash_value[5];
173  uint32_t H[5];
174  int i;
175
176  /* check tag length, return error if we can't provide the value expected */
177  if (tag_len > 20)
178    return err_status_bad_param;
179
180  /* hash message, copy output into H */
181  hmac_update(state, (const uint8_t*)message, msg_octets);
182  sha1_final(&state->ctx, H);
183
184  /*
185   * note that we don't need to debug_print() the input, since the
186   * function hmac_update() already did that for us
187   */
188  debug_print(mod_hmac, "intermediate state: %s",
189	      octet_string_hex_string((uint8_t *)H, 20));
190
191  /* re-initialize hash context */
192  sha1_init(&state->ctx);
193
194  /* hash opad ^ key  */
195  sha1_update(&state->ctx, (uint8_t *)state->opad, 64);
196
197  /* hash the result of the inner hash */
198  sha1_update(&state->ctx, (uint8_t *)H, 20);
199
200  /* the result is returned in the array hash_value[] */
201  sha1_final(&state->ctx, hash_value);
202
203  /* copy hash_value to *result */
204  for (i=0; i < tag_len; i++)
205    result[i] = ((uint8_t *)hash_value)[i];
206
207  debug_print(mod_hmac, "output: %s",
208	      octet_string_hex_string((uint8_t *)hash_value, tag_len));
209
210  return err_status_ok;
211}
212
213
214/* begin test case 0 */
215
216uint8_t
217hmac_test_case_0_key[20] = {
218  0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b,
219  0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b,
220  0x0b, 0x0b, 0x0b, 0x0b
221};
222
223uint8_t
224hmac_test_case_0_data[8] = {
225  0x48, 0x69, 0x20, 0x54, 0x68, 0x65, 0x72, 0x65   /* "Hi There" */
226};
227
228uint8_t
229hmac_test_case_0_tag[20] = {
230  0xb6, 0x17, 0x31, 0x86, 0x55, 0x05, 0x72, 0x64,
231  0xe2, 0x8b, 0xc0, 0xb6, 0xfb, 0x37, 0x8c, 0x8e,
232  0xf1, 0x46, 0xbe, 0x00
233};
234
235auth_test_case_t
236hmac_test_case_0 = {
237  20,                        /* octets in key            */
238  hmac_test_case_0_key,      /* key                      */
239  8,                         /* octets in data           */
240  hmac_test_case_0_data,     /* data                     */
241  20,                        /* octets in tag            */
242  hmac_test_case_0_tag,      /* tag                      */
243  NULL                       /* pointer to next testcase */
244};
245
246/* end test case 0 */
247
248char hmac_description[] = "hmac sha-1 authentication function";
249
250/*
251 * auth_type_t hmac is the hmac metaobject
252 */
253
254auth_type_t
255hmac  = {
256  (auth_alloc_func)      hmac_alloc,
257  (auth_dealloc_func)    hmac_dealloc,
258  (auth_init_func)       hmac_init,
259  (auth_compute_func)    hmac_compute,
260  (auth_update_func)     hmac_update,
261  (auth_start_func)      hmac_start,
262  (char *)               hmac_description,
263  (int)                  0,  /* instance count */
264  (auth_test_case_t *)  &hmac_test_case_0,
265  (debug_module_t *)    &mod_hmac
266};
267
268