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_unregister_all
140 * bool silc_hmac_unregister_all(void);
144 * Unregisters all registered HMACs.
147 bool silc_hmac_unregister_all(void);
149 /****f* silccrypt/SilcHMACAPI/silc_hmac_alloc
153 * bool silc_hmac_alloc(char *name, SilcHash hash, SilcHmac *new_hmac);
157 * Allocates a new SilcHmac object of name of `name'. The `hash' may
158 * be provided as argument. If provided it is used as the hash function
159 * of the HMAC. If it is NULL then the hash function is allocated and
160 * the name of the hash algorithm is derived from the `name'. Returns
161 * FALSE if such HMAC does not exist.
164 bool silc_hmac_alloc(char *name, SilcHash hash, SilcHmac *new_hmac);
166 /****f* silccrypt/SilcHMACAPI/silc_hmac_free
170 * void silc_hmac_free(SilcHmac hmac);
174 * Frees the allocated HMAC context. The key that may have been set
175 * with the silc_hmac_set_key is also destroyed.
178 void silc_hmac_free(SilcHmac hmac);
180 /****f* silccrypt/SilcHMACAPI/silc_hmac_is_supported
184 * bool silc_hmac_is_supported(const char *name);
188 * Returns TRUE if the HMAC indicated by the `name' exists.
191 bool silc_hmac_is_supported(const char *name);
193 /****f* silccrypt/SilcHMACAPI/silc_hmac_get_supported
197 * char *silc_hmac_get_supported(void);
201 * Returns comma (`,') separated list of registered HMACs. This is
202 * used for example when sending supported HMAC list during the SILC
203 * Key Exchange protocol (SKE). The caller must free the returned
207 char *silc_hmac_get_supported(void);
209 /****f* silccrypt/SilcHMACAPI/silc_hmac_len
213 * SilcUInt32 silc_hmac_len(SilcHmac hmac);
217 * Returns the length of the MAC that the HMAC will produce.
220 SilcUInt32 silc_hmac_len(SilcHmac hmac);
222 /****f* silccrypt/SilcHMACAPI/silc_hmac_get_hash
226 * SilcHash silc_hmac_get_hash(SilcHmac hmac);
230 * Returns the SilcHash context that has been associated with the
231 * HMAC context. The caller must not free the returned context.
234 SilcHash silc_hmac_get_hash(SilcHmac hmac);
236 /****f* silccrypt/SilcHMACAPI/silc_hmac_get_name
240 * const char *silc_hmac_get_name(SilcHmac hmac);
244 * Returns the name of the HMAC context.
247 const char *silc_hmac_get_name(SilcHmac hmac);
249 /****f* silccrypt/SilcHMACAPI/silc_hmac_set_key
253 * void silc_hmac_set_key(SilcHmac hmac, const unsigned char *key,
254 * SilcUInt32 key_len);
258 * Sets the key to be used in the HMAC operation. This must be set
259 * before calling silc_hmac_make or silc_hmac_final functions. If
260 * you do not want to set the key you can still produce a MAC by
261 * calling the silc_hmac_make_with_key where you give the key as
262 * argument. Usually application still wants to set the key.
265 void silc_hmac_set_key(SilcHmac hmac, const unsigned char *key,
268 /****f* silccrypt/SilcHMACAPI/silc_hmac_make
272 * void silc_hmac_make(SilcHmac hmac, unsigned char *data,
273 * SilcUInt32 data_len, unsigned char *return_hash,
274 * SilcUInt32 *return_len);
278 * Computes a MAC from a data buffer indicated by the `data' of the
279 * length of `data_len'. The returned MAC is copied into the
280 * `return_hash' pointer which must be at least the size of the
281 * value silc_hmac_len returns. The returned length is still
282 * returned to `return_len'.
285 void silc_hmac_make(SilcHmac hmac, unsigned char *data,
286 SilcUInt32 data_len, unsigned char *return_hash,
287 SilcUInt32 *return_len);
289 /****f* silccrypt/SilcHMACAPI/silc_hmac_make_with_key
293 * void silc_hmac_make_with_key(SilcHmac hmac, unsigned char *data,
294 * SilcUInt32 data_len,
295 * unsigned char *key, SilcUInt32 key_len,
296 * unsigned char *return_hash,
297 * SilcUInt32 *return_len);
301 * Same as the silc_hmac_make but takes the key for the HMAC as
302 * argument. If this is used the key that may have been set by calling
303 * silc_hmac_set_key is ignored.
306 void silc_hmac_make_with_key(SilcHmac hmac, unsigned char *data,
308 unsigned char *key, SilcUInt32 key_len,
309 unsigned char *return_hash,
310 SilcUInt32 *return_len);
312 /****f* silccrypt/SilcHMACAPI/silc_hmac_make_truncated
316 * void silc_hmac_make_truncated(SilcHmac hmac,
317 * unsigned char *data,
318 * SilcUInt32 data_len,
319 * SilcUInt32 truncated_len,
320 * unsigned char *return_hash);
324 * Same as the silc_hmac_make except that the returned MAC is
325 * truncated to the length indicated by the `truncated_len'. Some
326 * special applications may need this function. The `return_hash'
327 * must be at least the size of `truncated_len'.
331 * For security reasons, one should not truncate to less than half
332 * of the length of the true MAC lenght. However, since this routine
333 * may be used to non-critical applications this allows these dangerous
337 void silc_hmac_make_truncated(SilcHmac hmac,
340 SilcUInt32 truncated_len,
341 unsigned char *return_hash);
343 /****f* silccrypt/SilcHMACAPI/silc_hmac_init
347 * void silc_hmac_init(SilcHmac hmac);
351 * Sometimes calling the silc_hmac_make might not be the most
352 * optimal case of doing MACs. If you have a lot of different data
353 * that you need to put together for computing a MAC you may either
354 * put them into a buffer and compute the MAC from the buffer by
355 * calling the silc_hmac_make, or you can use the silc_hmac_init,
356 * silc_hmac_update and silc_hmac_final to do the MAC. This function
357 * prepares the allocated HMAC context for this kind of MAC
358 * computation. The caller must have been called the function
359 * silc_hmac_set_key before calling this function. To add the
360 * data to be used in the MAC computation call the silc_hmac_update
364 void silc_hmac_init(SilcHmac hmac);
366 /****f* silccrypt/SilcHMACAPI/silc_hmac_init_with_key
370 * void silc_hmac_init_with_key(SilcHmac hmac, const unsigned char *key,
371 * SilcUInt32 key_len);
375 * Same as silc_hmac_init but initializes with specific key. The
376 * key that may have been set with silc_hmac_set_key is ignored.
379 void silc_hmac_init_with_key(SilcHmac hmac, const unsigned char *key,
382 /****f* silccrypt/SilcHMACAPI/silc_hmac_update
386 * void silc_hmac_update(SilcHmac hmac, const unsigned char *data,
387 * SilcUInt32 data_len);
391 * This function may be called to add data to be used in the MAC
392 * computation. This can be called multiple times to add data from
393 * many sources before actually performing the HMAC. Once you've
394 * added all the data you need you can call the silc_hmac_final to
395 * actually produce the MAC.
399 * unsigned char mac[20];
400 * SilcUInt32 mac_len;
402 * silc_hmac_init(hmac);
403 * silc_hmac_update(hmac, data, data_len);
404 * silc_hmac_update(hmac, more_data, more_data_len);
405 * silc_hmac_final(hmac, mac, &mac_len);
408 void silc_hmac_update(SilcHmac hmac, const unsigned char *data,
409 SilcUInt32 data_len);
411 /****f* silccrypt/SilcHMACAPI/silc_hmac_final
415 * void silc_hmac_final(SilcHmac hmac, unsigned char *return_hash,
416 * SilcUInt32 *return_len);
420 * This function is used to produce the final MAC from the data
421 * that has been added to the HMAC context by calling the
422 * silc_hmac_update function. The MAC is copied in to the
423 * `return_hash' pointer which must be at least the size that
424 * the silc_hmac_len returns. The length of the MAC is still
425 * returned into `return_len'.
428 void silc_hmac_final(SilcHmac hmac, unsigned char *return_hash,
429 SilcUInt32 *return_len);