5 Author: Pekka Riikonen <priikone@silcnet.org>
7 Copyright (C) 1999 - 2002 Pekka Riikonen
9 This program is free software; you can redistribute it and/or modify
10 it under the terms of the GNU General Public License as published by
11 the Free Software Foundation; version 2 of the License.
13 This program is distributed in the hope that it will be useful,
14 but WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 GNU General Public License for more details.
23 /****h* silccrypt/SILC HMAC Interface
27 * This is the interface for HMAC, or the keyed hash values, that are
28 * used for packet and message authentication. These routines uses
29 * already implemented hash functions from the SilcHashAPI. These
30 * routines were created according to RFC 2104.
34 /****s* silccrypt/SilcHMACAPI/SilcHmac
38 * typedef struct SilcHmacStruct *SilcHmac;
42 * This context is the actual HMAC context and is allocated
43 * by silc_hmac_alloc and given as argument usually to all
44 * silc_hmac_* functions. It is freed by the silc_hmac_free
48 typedef struct SilcHmacStruct *SilcHmac;
50 /****s* silccrypt/SilcHMACAPI/SilcHmacObject
54 * typedef struct { ... } SilcHmacObject;
58 * This structure represents one HMAC. The HMAC's name and the
59 * MAC length is defined in the structure. This structure is
60 * then given as argument to the silc_hmac_register. That function
61 * is used to register all HMACs into SILC. They can be then
62 * allocated by the name found in this structure by calling the
71 /* Marks for all hmacs. This can be used in silc_hmac_unregister
72 to unregister all hmacs at once. */
73 #define SILC_ALL_HMACS ((SilcHmacObject *)1)
75 /* Default hmacs for silc_hmac_register_default(). */
76 extern DLLAPI const SilcHmacObject silc_default_hmacs[];
78 /* Default HMAC in the SILC protocol */
79 #define SILC_DEFAULT_HMAC "hmac-sha1-96"
83 /****f* silccrypt/SilcHMACAPI/silc_hmac_register
87 * bool silc_hmac_register(const SilcHmacObject *hmac);
91 * Registers a new HMAC into the SILC. This function is used at the
92 * initialization of the SILC. All registered HMACs should be
93 * unregistered with silc_hmac_unregister. The `hmac' includes the
94 * name of the HMAC and the length of the MAC. Usually this
95 * function is not called directly. Instead, application can call
96 * the silc_hmac_register_default to register all default HMACs
97 * that are builtin the sources. Returns FALSE on error.
100 bool silc_hmac_register(const SilcHmacObject *hmac);
102 /****f* silccrypt/SilcHMACAPI/silc_hmac_unregister
106 * bool silc_hmac_unregister(SilcHmacObject *hmac);
110 * Unregister a HMAC from SILC by the HMAC structure `hmac'. This
111 * should be called for all registered HMAC's. Returns FALSE on
115 bool silc_hmac_unregister(SilcHmacObject *hmac);
117 /****f* silccrypt/SilcHMACAPI/silc_hmac_register_default
121 * bool silc_hmac_register_default(void);
125 * Registers all default HMACs into the SILC. These are the HMACs
126 * that are builtin in the sources. See the list of default HMACs
127 * in the silchmac.c source file. The application may use this
128 * to register default HMACs if specific HMAC in any specific order
129 * is not wanted (application's configuration usually may decide
130 * the order of the registration, in which case this should not be
134 bool silc_hmac_register_default(void);
136 /****f* silccrypt/SilcHMACAPI/silc_hmac_alloc
140 * bool silc_hmac_alloc(char *name, SilcHash hash, SilcHmac *new_hmac);
144 * Allocates a new SilcHmac object of name of `name'. The `hash' may
145 * be provided as argument. If provided it is used as the hash function
146 * of the HMAC. If it is NULL then the hash function is allocated and
147 * the name of the hash algorithm is derived from the `name'. Returns
148 * FALSE if such HMAC does not exist.
151 bool silc_hmac_alloc(char *name, SilcHash hash, SilcHmac *new_hmac);
153 /****f* silccrypt/SilcHMACAPI/silc_hmac_free
157 * void silc_hmac_free(SilcHmac hmac);
161 * Frees the allocated HMAC context. The key that may have been set
162 * with the silc_hmac_set_key is also destroyed.
165 void silc_hmac_free(SilcHmac hmac);
167 /****f* silccrypt/SilcHMACAPI/silc_hmac_is_supported
171 * bool silc_hmac_is_supported(const char *name);
175 * Returns TRUE if the HMAC indicated by the `name' exists.
178 bool silc_hmac_is_supported(const char *name);
180 /****f* silccrypt/SilcHMACAPI/silc_hmac_get_supported
184 * char *silc_hmac_get_supported(void);
188 * Returns comma (`,') separated list of registered HMACs. This is
189 * used for example when sending supported HMAC list during the SILC
190 * Key Exchange protocol (SKE). The caller must free the returned
194 char *silc_hmac_get_supported(void);
196 /****f* silccrypt/SilcHMACAPI/silc_hmac_len
200 * SilcUInt32 silc_hmac_len(SilcHmac hmac);
204 * Returns the length of the MAC that the HMAC will produce.
207 SilcUInt32 silc_hmac_len(SilcHmac hmac);
209 /****f* silccrypt/SilcHMACAPI/silc_hmac_get_hash
213 * SilcHash silc_hmac_get_hash(SilcHmac hmac);
217 * Returns the SilcHash context that has been associated with the
218 * HMAC context. The caller must not free the returned context.
221 SilcHash silc_hmac_get_hash(SilcHmac hmac);
223 /****f* silccrypt/SilcHMACAPI/silc_hmac_get_name
227 * const char *silc_hmac_get_name(SilcHmac hmac);
231 * Returns the name of the HMAC context.
234 const char *silc_hmac_get_name(SilcHmac hmac);
236 /****f* silccrypt/SilcHMACAPI/silc_hmac_set_key
240 * void silc_hmac_set_key(SilcHmac hmac, const unsigned char *key,
241 * SilcUInt32 key_len);
245 * Sets the key to be used in the HMAC operation. This must be set
246 * before calling silc_hmac_make or silc_hmac_final functions. If
247 * you do not want to set the key you can still produce a MAC by
248 * calling the silc_hmac_make_with_key where you give the key as
249 * argument. Usually application still wants to set the key.
252 void silc_hmac_set_key(SilcHmac hmac, const unsigned char *key,
255 /****f* silccrypt/SilcHMACAPI/silc_hmac_make
259 * void silc_hmac_make(SilcHmac hmac, unsigned char *data,
260 * SilcUInt32 data_len, unsigned char *return_hash,
261 * SilcUInt32 *return_len);
265 * Computes a MAC from a data buffer indicated by the `data' of the
266 * length of `data_len'. The returned MAC is copied into the
267 * `return_hash' pointer which must be at least the size of the
268 * value silc_hmac_len returns. The returned length is still
269 * returned to `return_len'.
272 void silc_hmac_make(SilcHmac hmac, unsigned char *data,
273 SilcUInt32 data_len, unsigned char *return_hash,
274 SilcUInt32 *return_len);
276 /****f* silccrypt/SilcHMACAPI/silc_hmac_make_with_key
280 * void silc_hmac_make_with_key(SilcHmac hmac, unsigned char *data,
281 * SilcUInt32 data_len,
282 * unsigned char *key, SilcUInt32 key_len,
283 * unsigned char *return_hash,
284 * SilcUInt32 *return_len);
288 * Same as the silc_hmac_make but takes the key for the HMAC as
289 * argument. If this is used the key that may have been set by calling
290 * silc_hmac_set_key is ignored.
293 void silc_hmac_make_with_key(SilcHmac hmac, unsigned char *data,
295 unsigned char *key, SilcUInt32 key_len,
296 unsigned char *return_hash,
297 SilcUInt32 *return_len);
299 /****f* silccrypt/SilcHMACAPI/silc_hmac_make_truncated
303 * void silc_hmac_make_truncated(SilcHmac hmac,
304 * unsigned char *data,
305 * SilcUInt32 data_len,
306 * SilcUInt32 truncated_len,
307 * unsigned char *return_hash);
311 * Same as the silc_hmac_make except that the returned MAC is
312 * truncated to the length indicated by the `truncated_len'. Some
313 * special applications may need this function. The `return_hash'
314 * must be at least the size of `truncated_len'.
318 * For security reasons, one should not truncate to less than half
319 * of the length of the true MAC lenght. However, since this routine
320 * may be used to non-critical applications this allows these dangerous
324 void silc_hmac_make_truncated(SilcHmac hmac,
327 SilcUInt32 truncated_len,
328 unsigned char *return_hash);
330 /****f* silccrypt/SilcHMACAPI/silc_hmac_init
334 * void silc_hmac_init(SilcHmac hmac);
338 * Sometimes calling the silc_hmac_make might not be the most
339 * optimal case of doing MACs. If you have a lot of different data
340 * that you need to put together for computing a MAC you may either
341 * put them into a buffer and compute the MAC from the buffer by
342 * calling the silc_hmac_make, or you can use the silc_hmac_init,
343 * silc_hmac_update and silc_hmac_final to do the MAC. This function
344 * prepares the allocated HMAC context for this kind of MAC
345 * computation. The caller must have been called the function
346 * silc_hmac_set_key before calling this function. To add the
347 * data to be used in the MAC computation call the silc_hmac_update
351 void silc_hmac_init(SilcHmac hmac);
353 /****f* silccrypt/SilcHMACAPI/silc_hmac_init_with_key
357 * void silc_hmac_init_with_key(SilcHmac hmac, const unsigned char *key,
358 * SilcUInt32 key_len);
362 * Same as silc_hmac_init but initializes with specific key. The
363 * key that may have been set with silc_hmac_set_key is ignored.
366 void silc_hmac_init_with_key(SilcHmac hmac, const unsigned char *key,
369 /****f* silccrypt/SilcHMACAPI/silc_hmac_update
373 * void silc_hmac_update(SilcHmac hmac, const unsigned char *data,
374 * SilcUInt32 data_len);
378 * This function may be called to add data to be used in the MAC
379 * computation. This can be called multiple times to add data from
380 * many sources before actually performing the HMAC. Once you've
381 * added all the data you need you can call the silc_hmac_final to
382 * actually produce the MAC.
386 * unsigned char mac[20];
387 * SilcUInt32 mac_len;
389 * silc_hmac_init(hmac);
390 * silc_hmac_update(hmac, data, data_len);
391 * silc_hmac_update(hmac, more_data, more_data_len);
392 * silc_hmac_final(hmac, mac, &mac_len);
395 void silc_hmac_update(SilcHmac hmac, const unsigned char *data,
396 SilcUInt32 data_len);
398 /****f* silccrypt/SilcHMACAPI/silc_hmac_final
402 * void silc_hmac_final(SilcHmac hmac, unsigned char *return_hash,
403 * SilcUInt32 *return_len);
407 * This function is used to produce the final MAC from the data
408 * that has been added to the HMAC context by calling the
409 * silc_hmac_update function. The MAC is copied in to the
410 * `return_hash' pointer which must be at least the size that
411 * the silc_hmac_len returns. The length of the MAC is still
412 * returned into `return_len'.
415 void silc_hmac_final(SilcHmac hmac, unsigned char *return_hash,
416 SilcUInt32 *return_len);