summaryrefslogtreecommitdiff
path: root/source4/heimdal/lib/hcrypto/dh.c
blob: 3ad37f87a78c7ded677b28b522817909959edaa0 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
/*
 * Copyright (c) 2006 - 2007 Kungliga Tekniska Högskolan
 * (Royal Institute of Technology, Stockholm, Sweden).
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * 3. Neither the name of the Institute nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdio.h>
#include <stdlib.h>
#include <krb5-types.h>
#include <rfc2459_asn1.h>

#include <dh.h>

#include <roken.h>

/**
 * @page page_dh DH - Diffie-Hellman key exchange
 *
 * Diffie-Hellman key exchange is a protocol that allows two parties
 * to establish a shared secret key.
 *
 * Include and example how to use DH_new() and friends here.
 *
 * See the library functions here: @ref hcrypto_dh
 */

/**
 * Create a new DH object using DH_new_method(NULL), see DH_new_method().
 *
 * @return a newly allocated DH object.
 *
 * @ingroup hcrypto_dh
 */

DH *
DH_new(void)
{
    return DH_new_method(NULL);
}

/**
 * Create a new DH object from the given engine, if the NULL is used,
 * the default engine is used. Free the DH object with DH_free().
 *
 * @param engine The engine to use to allocate the DH object.
 *
 * @return a newly allocated DH object.
 *
 * @ingroup hcrypto_dh
 */

DH *
DH_new_method(ENGINE *engine)
{
    DH *dh;

    dh = calloc(1, sizeof(*dh));
    if (dh == NULL)
	return NULL;

    dh->references = 1;

    if (engine) {
	ENGINE_up_ref(engine);
	dh->engine = engine;
    } else {
	dh->engine = ENGINE_get_default_DH();
    }

    if (dh->engine) {
	dh->meth = ENGINE_get_DH(dh->engine);
	if (dh->meth == NULL) {
	    ENGINE_finish(engine);
	    free(dh);
	    return 0;
	}
    }

    if (dh->meth == NULL)
	dh->meth = DH_get_default_method();

    (*dh->meth->init)(dh);

    return dh;
}

/**
 * Free a DH object and release related resources, like ENGINE, that
 * the object was using.
 *
 * @param dh object to be freed.
 *
 * @ingroup hcrypto_dh
 */

void
DH_free(DH *dh)
{
    if (dh->references <= 0)
	abort();

    if (--dh->references > 0)
	return;

    (*dh->meth->finish)(dh);

    if (dh->engine)
	ENGINE_finish(dh->engine);

#define free_if(f) if (f) { BN_free(f); }
    free_if(dh->p);
    free_if(dh->g);
    free_if(dh->pub_key);
    free_if(dh->priv_key);
    free_if(dh->q);
    free_if(dh->j);
    free_if(dh->counter);
#undef free_if

    memset(dh, 0, sizeof(*dh));
    free(dh);
}

/**
 * Add a reference to the DH object. The object should be free with
 * DH_free() to drop the reference.
 *
 * @param dh the object to increase the reference count too.
 *
 * @return the updated reference count, can't safely be used except
 * for debug printing.
 *
 * @ingroup hcrypto_dh
 */

int
DH_up_ref(DH *dh)
{
    return ++dh->references;
}

/**
 * The maximum output size of the DH_compute_key() function.
 *
 * @param dh The DH object to get the size from.
 *
 * @return the maximum size in bytes of the out data.
 *
 * @ingroup hcrypto_dh
 */

int
DH_size(const DH *dh)
{
    return BN_num_bytes(dh->p);
}

/**
 * Set the data index idx in the DH object to data.
 *
 * @param dh DH object.
 * @param idx index to set the data for.
 * @param data data to store for the index idx.
 *
 * @return 1 on success.
 *
 * @ingroup hcrypto_dh
 */

int
DH_set_ex_data(DH *dh, int idx, void *data)
{
    dh->ex_data.sk = data;
    return 1;
}

/**
 * Get the data for index idx in the DH object.
 *
 * @param dh DH object.
 * @param idx index to get the data for.
 *
 * @return the object store in index idx
 *
 * @ingroup hcrypto_dh
 */

void *
DH_get_ex_data(DH *dh, int idx)
{
    return dh->ex_data.sk;
}

/**
 * Generate DH parameters for the DH object give parameters.
 *
 * @param dh The DH object to generate parameters for.
 * @param prime_len length of the prime
 * @param generator generator, g
 * @param cb Callback parameters to show progress, can be NULL.
 *
 * @return the maximum size in bytes of the out data.
 *
 * @ingroup hcrypto_dh
 */

int
DH_generate_parameters_ex(DH *dh, int prime_len, int generator, BN_GENCB *cb)
{
    if (dh->meth->generate_params)
	return dh->meth->generate_params(dh, prime_len, generator, cb);
    return 0;
}

/**
 * Check that the public key is sane.
 *
 * @param dh the local peer DH parameters.
 * @param pub_key the remote peer public key parameters.
 * @param codes return that the failures of the pub_key are.
 *
 * @return 1 on success, 0 on failure and *codes is set the the
 * combined fail check for the public key
 *
 * @ingroup hcrypto_dh
 */

int
DH_check_pubkey(const DH *dh, const BIGNUM *pub_key, int *codes)
{
    BIGNUM *bn = NULL, *sum = NULL;
    int ret = 0;

    *codes = 0;

    /**
     * Checks that the function performs are:
     * - pub_key is not negative
     */

    if (BN_is_negative(pub_key))
	goto out;

    /**
     * - pub_key > 1    and    pub_key < p - 1,
     *    to avoid small subgroups attack.
     */

    bn = BN_new();
    if (bn == NULL)
	goto out;

    if (!BN_set_word(bn, 1))
	goto out;

    if (BN_cmp(bn, pub_key) >= 0)
	*codes |= DH_CHECK_PUBKEY_TOO_SMALL;

    sum = BN_new();
    if (sum == NULL)
	goto out;

    BN_uadd(sum, pub_key, bn);

    if (BN_cmp(sum, dh->p) >= 0)
	*codes |= DH_CHECK_PUBKEY_TOO_LARGE;

    /**
     * - if g == 2, pub_key have more then one bit set,
     *   if bits set is 1, log_2(pub_key) is trival
     */

    if (!BN_set_word(bn, 2))
	goto out;

    if (BN_cmp(bn, pub_key) == 0) {
	unsigned i, n = BN_num_bits(pub_key);
	unsigned bits = 0;

	for (i = 0; i <= n; i++)
	    if (BN_is_bit_set(pub_key, i))
		bits++;

	if (bits > 1) {
	    *codes |= DH_CHECK_PUBKEY_TOO_SMALL;
	    goto out;
	}
    }

    ret = 1;
out:
    if (bn)
	BN_free(bn);
    if (sum)
	BN_free(sum);

    return ret;
}

/**
 * Generate a new DH private-public key pair. The dh parameter must be
 * allocted first with DH_new(). dh->p and dp->g must be set.
 *
 * @param dh dh parameter.
 *
 * @return 1 on success.
 *
 * @ingroup hcrypto_dh
 */

int
DH_generate_key(DH *dh)
{
    return dh->meth->generate_key(dh);
}

/**
 * Complute the shared secret key.
 *
 * @param shared_key the resulting shared key, need to be at least
 * DH_size() large.
 * @param peer_pub_key the peer's public key.
 * @param dh the dh key pair.
 *
 * @return 1 on success.
 *
 * @ingroup hcrypto_dh
 */

int
DH_compute_key(unsigned char *shared_key,
	       const BIGNUM *peer_pub_key, DH *dh)
{
    int codes;

    /**
     * Checks that the pubkey passed in is valid using
     * DH_check_pubkey().
     */

    if (!DH_check_pubkey(dh, peer_pub_key, &codes) || codes != 0)
	return -1;

    return dh->meth->compute_key(shared_key, peer_pub_key, dh);
}

/**
 * Set a new method for the DH keypair.
 *
 * @param dh dh parameter.
 * @param method the new method for the DH parameter.
 *
 * @return 1 on success.
 *
 * @ingroup hcrypto_dh
 */

int
DH_set_method(DH *dh, const DH_METHOD *method)
{
    (*dh->meth->finish)(dh);
    if (dh->engine) {
	ENGINE_finish(dh->engine);
	dh->engine = NULL;
    }
    dh->meth = method;
    (*dh->meth->init)(dh);
    return 1;
}

/*
 *
 */

static int
dh_null_generate_key(DH *dh)
{
    return 0;
}

static int
dh_null_compute_key(unsigned char *shared,const BIGNUM *pub, DH *dh)
{
    return 0;
}

static int
dh_null_init(DH *dh)
{
    return 1;
}

static int
dh_null_finish(DH *dh)
{
    return 1;
}

static int
dh_null_generate_params(DH *dh, int prime_num, int len, BN_GENCB *cb)
{
    return 0;
}

static const DH_METHOD dh_null_method = {
    "hcrypto null DH",
    dh_null_generate_key,
    dh_null_compute_key,
    NULL,
    dh_null_init,
    dh_null_finish,
    0,
    NULL,
    dh_null_generate_params
};

extern const DH_METHOD _hc_dh_imath_method;
static const DH_METHOD *dh_default_method = &_hc_dh_imath_method;

/**
 * Return the dummy DH implementation.
 *
 * @return pointer to a DH_METHOD.
 *
 * @ingroup hcrypto_dh
 */

const DH_METHOD *
DH_null_method(void)
{
    return &dh_null_method;
}

/**
 * Set the default DH implementation.
 *
 * @param meth pointer to a DH_METHOD.
 *
 * @ingroup hcrypto_dh
 */

void
DH_set_default_method(const DH_METHOD *meth)
{
    dh_default_method = meth;
}

/**
 * Return the default DH implementation.
 *
 * @return pointer to a DH_METHOD.
 *
 * @ingroup hcrypto_dh
 */

const DH_METHOD *
DH_get_default_method(void)
{
    return dh_default_method;
}

/*
 *
 */

static int
bn2heim_int(BIGNUM *bn, heim_integer *integer)
{
    integer->length = BN_num_bytes(bn);
    integer->data = malloc(integer->length);
    if (integer->data == NULL) {
	integer->length = 0;
	return ENOMEM;
    }
    BN_bn2bin(bn, integer->data);
    integer->negative = BN_is_negative(bn);
    return 0;
}

/**
 *
 */

int
i2d_DHparams(DH *dh, unsigned char **pp)
{
    DHParameter data;
    size_t size;
    int ret;

    memset(&data, 0, sizeof(data));

    if (bn2heim_int(dh->p, &data.prime) ||
	bn2heim_int(dh->g, &data.base))
    {
	free_DHParameter(&data);
	return -1;
    }

    if (pp == NULL) {
	size = length_DHParameter(&data);
	free_DHParameter(&data);
    } else {
	void *p;
	size_t len;

	ASN1_MALLOC_ENCODE(DHParameter, p, len, &data, &size, ret);
	free_DHParameter(&data);
	if (ret)
	    return -1;
	if (len != size)
	    abort();

	memcpy(*pp, p, size);
	free(p);

	*pp += size;
    }

    return size;
}