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1/*
2 * RTMP Diffie-Hellmann utilities
3 * Copyright (c) 2009 Andrej Stepanchuk
4 * Copyright (c) 2009-2010 Howard Chu
5 * Copyright (c) 2012 Samuel Pitoiset
6 *
7 * This file is part of FFmpeg.
8 *
9 * FFmpeg is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU Lesser General Public
11 * License as published by the Free Software Foundation; either
12 * version 2.1 of the License, or (at your option) any later version.
13 *
14 * FFmpeg is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17 * Lesser General Public License for more details.
18 *
19 * You should have received a copy of the GNU Lesser General Public
20 * License along with FFmpeg; if not, write to the Free Software
21 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
22 */
23
24/**
25 * @file
26 * RTMP Diffie-Hellmann utilities
27 */
28
29#include <stdint.h>
30#include <string.h>
31
32#include "config.h"
33
34#include "libavutil/attributes.h"
35#include "libavutil/error.h"
36#include "libavutil/mem.h"
37#include "libavutil/random_seed.h"
38
39#include "rtmpdh.h"
40
41#define P1024 \
42 "FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD1" \
43 "29024E088A67CC74020BBEA63B139B22514A08798E3404DD" \
44 "EF9519B3CD3A431B302B0A6DF25F14374FE1356D6D51C245" \
45 "E485B576625E7EC6F44C42E9A637ED6B0BFF5CB6F406B7ED" \
46 "EE386BFB5A899FA5AE9F24117C4B1FE649286651ECE65381" \
47 "FFFFFFFFFFFFFFFF"
48
49#define Q1024 \
50 "7FFFFFFFFFFFFFFFE487ED5110B4611A62633145C06E0E68" \
51 "948127044533E63A0105DF531D89CD9128A5043CC71A026E" \
52 "F7CA8CD9E69D218D98158536F92F8A1BA7F09AB6B6A8E122" \
53 "F242DABB312F3F637A262174D31BF6B585FFAE5B7A035BF6" \
54 "F71C35FDAD44CFD2D74F9208BE258FF324943328F67329C0" \
55 "FFFFFFFFFFFFFFFF"
56
57#if CONFIG_GMP
58#define bn_new(bn) \
59 do { \
60 bn = av_malloc(sizeof(*bn)); \
61 if (bn) \
62 mpz_init2(bn, 1); \
63 } while (0)
64#define bn_free(bn) \
65 do { \
66 mpz_clear(bn); \
67 av_free(bn); \
68 } while (0)
69#define bn_set_word(bn, w) mpz_set_ui(bn, w)
70#define bn_cmp(a, b) mpz_cmp(a, b)
71#define bn_copy(to, from) mpz_set(to, from)
72#define bn_sub_word(bn, w) mpz_sub_ui(bn, bn, w)
73#define bn_cmp_1(bn) mpz_cmp_ui(bn, 1)
74#define bn_num_bytes(bn) (mpz_sizeinbase(bn, 2) + 7) / 8
75#define bn_bn2bin(bn, buf, len) \
76 do { \
77 memset(buf, 0, len); \
78 if (bn_num_bytes(bn) <= len) \
79 mpz_export(buf, NULL, 1, 1, 0, 0, bn); \
80 } while (0)
81#define bn_bin2bn(bn, buf, len) \
82 do { \
83 bn_new(bn); \
84 if (bn) \
85 mpz_import(bn, len, 1, 1, 0, 0, buf); \
86 } while (0)
87#define bn_hex2bn(bn, buf, ret) \
88 do { \
89 bn_new(bn); \
90 if (bn) \
91 ret = (mpz_set_str(bn, buf, 16) == 0); \
92 else \
93 ret = 1; \
94 } while (0)
95#define bn_random(bn, num_bits) \
96 do { \
97 int bits = num_bits; \
98 mpz_set_ui(bn, 0); \
99 for (bits = num_bits; bits > 0; bits -= 32) { \
100 mpz_mul_2exp(bn, bn, 32); \
101 mpz_add_ui(bn, bn, av_get_random_seed()); \
102 } \
103 mpz_fdiv_r_2exp(bn, bn, num_bits); \
104 } while (0)
105static int bn_modexp(FFBigNum bn, FFBigNum y, FFBigNum q, FFBigNum p)
106{
107 mpz_powm(bn, y, q, p);
108 return 0;
109}
110#elif CONFIG_GCRYPT
111#define bn_new(bn) \
112 do { \
113 if (!gcry_control(GCRYCTL_INITIALIZATION_FINISHED_P)) { \
114 if (!gcry_check_version("1.5.4")) \
115 return AVERROR(EINVAL); \
116 gcry_control(GCRYCTL_DISABLE_SECMEM, 0); \
117 gcry_control(GCRYCTL_INITIALIZATION_FINISHED, 0); \
118 } \
119 bn = gcry_mpi_new(1); \
120 } while (0)
121#define bn_free(bn) gcry_mpi_release(bn)
122#define bn_set_word(bn, w) gcry_mpi_set_ui(bn, w)
123#define bn_cmp(a, b) gcry_mpi_cmp(a, b)
124#define bn_copy(to, from) gcry_mpi_set(to, from)
125#define bn_sub_word(bn, w) gcry_mpi_sub_ui(bn, bn, w)
126#define bn_cmp_1(bn) gcry_mpi_cmp_ui(bn, 1)
127#define bn_num_bytes(bn) (gcry_mpi_get_nbits(bn) + 7) / 8
128#define bn_bn2bin(bn, buf, len) gcry_mpi_print(GCRYMPI_FMT_USG, buf, len, NULL, bn)
129#define bn_bin2bn(bn, buf, len) gcry_mpi_scan(&bn, GCRYMPI_FMT_USG, buf, len, NULL)
130#define bn_hex2bn(bn, buf, ret) ret = (gcry_mpi_scan(&bn, GCRYMPI_FMT_HEX, buf, 0, 0) == 0)
131#define bn_random(bn, num_bits) gcry_mpi_randomize(bn, num_bits, GCRY_WEAK_RANDOM)
132static int bn_modexp(FFBigNum bn, FFBigNum y, FFBigNum q, FFBigNum p)
133{
134 gcry_mpi_powm(bn, y, q, p);
135 return 0;
136}
137#elif CONFIG_OPENSSL
138#define bn_new(bn) bn = BN_new()
139#define bn_free(bn) BN_free(bn)
140#define bn_set_word(bn, w) BN_set_word(bn, w)
141#define bn_cmp(a, b) BN_cmp(a, b)
142#define bn_copy(to, from) BN_copy(to, from)
143#define bn_sub_word(bn, w) BN_sub_word(bn, w)
144#define bn_cmp_1(bn) BN_cmp(bn, BN_value_one())
145#define bn_num_bytes(bn) BN_num_bytes(bn)
146#define bn_bn2bin(bn, buf, len) BN_bn2bin(bn, buf)
147#define bn_bin2bn(bn, buf, len) bn = BN_bin2bn(buf, len, 0)
148#define bn_hex2bn(bn, buf, ret) ret = BN_hex2bn(&bn, buf)
149#define bn_random(bn, num_bits) BN_rand(bn, num_bits, 0, 0)
150static int bn_modexp(FFBigNum bn, FFBigNum y, FFBigNum q, FFBigNum p)
151{
152 BN_CTX *ctx = BN_CTX_new();
153 if (!ctx)
154 return AVERROR(ENOMEM);
155 if (!BN_mod_exp(bn, y, q, p, ctx)) {
156 BN_CTX_free(ctx);
157 return AVERROR(EINVAL);
158 }
159 BN_CTX_free(ctx);
160 return 0;
161}
162#endif
163
164#define MAX_BYTES 18000
165
166#define dh_new() av_mallocz(sizeof(FF_DH))
167
168static FFBigNum dh_generate_key(FF_DH *dh)
169{
170 int num_bytes;
171
172 num_bytes = bn_num_bytes(dh->p) - 1;
173 if (num_bytes <= 0 || num_bytes > MAX_BYTES)
174 return NULL;
175
176 bn_new(dh->priv_key);
177 if (!dh->priv_key)
178 return NULL;
179 bn_random(dh->priv_key, 8 * num_bytes);
180
181 bn_new(dh->pub_key);
182 if (!dh->pub_key) {
183 bn_free(dh->priv_key);
184 return NULL;
185 }
186
187 if (bn_modexp(dh->pub_key, dh->g, dh->priv_key, dh->p) < 0)
188 return NULL;
189
190 return dh->pub_key;
191}
192
193static int dh_compute_key(FF_DH *dh, FFBigNum pub_key_bn,
194 uint32_t secret_key_len, uint8_t *secret_key)
195{
196 FFBigNum k;
197 int ret;
198
199 bn_new(k);
200 if (!k)
201 return -1;
202
203 if ((ret = bn_modexp(k, pub_key_bn, dh->priv_key, dh->p)) < 0) {
204 bn_free(k);
205 return ret;
206 }
207 bn_bn2bin(k, secret_key, secret_key_len);
208 bn_free(k);
209
210 /* return the length of the shared secret key like DH_compute_key */
211 return secret_key_len;
212}
213
214void ff_dh_free(FF_DH *dh)
215{
216 if (!dh)
217 return;
218 bn_free(dh->p);
219 bn_free(dh->g);
220 bn_free(dh->pub_key);
221 bn_free(dh->priv_key);
222 av_free(dh);
223}
224
225static int dh_is_valid_public_key(FFBigNum y, FFBigNum p, FFBigNum q)
226{
227 FFBigNum bn = NULL;
228 int ret = AVERROR(EINVAL);
229
230 bn_new(bn);
231 if (!bn)
232 return AVERROR(ENOMEM);
233
234 /* y must lie in [2, p - 1] */
235 bn_set_word(bn, 1);
236 if (!bn_cmp(y, bn))
237 goto fail;
238
239 /* bn = p - 2 */
240 bn_copy(bn, p);
241 bn_sub_word(bn, 1);
242 if (!bn_cmp(y, bn))
243 goto fail;
244
245 /* Verify with Sophie-Germain prime
246 *
247 * This is a nice test to make sure the public key position is calculated
248 * correctly. This test will fail in about 50% of the cases if applied to
249 * random data.
250 */
251 /* y must fulfill y^q mod p = 1 */
252 if ((ret = bn_modexp(bn, y, q, p)) < 0)
253 goto fail;
254
255 ret = AVERROR(EINVAL);
256 if (bn_cmp_1(bn))
257 goto fail;
258
259 ret = 0;
260fail:
261 bn_free(bn);
262
263 return ret;
264}
265
266av_cold FF_DH *ff_dh_init(int key_len)
267{
268 FF_DH *dh;
269 int ret;
270
271 if (!(dh = dh_new()))
272 return NULL;
273
274 bn_new(dh->g);
275 if (!dh->g)
276 goto fail;
277
278 bn_hex2bn(dh->p, P1024, ret);
279 if (!ret)
280 goto fail;
281
282 bn_set_word(dh->g, 2);
283 dh->length = key_len;
284
285 return dh;
286
287fail:
288 ff_dh_free(dh);
289
290 return NULL;
291}
292
293int ff_dh_generate_public_key(FF_DH *dh)
294{
295 int ret = 0;
296
297 while (!ret) {
298 FFBigNum q1 = NULL;
299
300 if (!dh_generate_key(dh))
301 return AVERROR(EINVAL);
302
303 bn_hex2bn(q1, Q1024, ret);
304 if (!ret)
305 return AVERROR(ENOMEM);
306
307 ret = dh_is_valid_public_key(dh->pub_key, dh->p, q1);
308 bn_free(q1);
309
310 if (!ret) {
311 /* the public key is valid */
312 break;
313 }
314 }
315
316 return ret;
317}
318
319int ff_dh_write_public_key(FF_DH *dh, uint8_t *pub_key, int pub_key_len)
320{
321 int len;
322
323 /* compute the length of the public key */
324 len = bn_num_bytes(dh->pub_key);
325 if (len <= 0 || len > pub_key_len)
326 return AVERROR(EINVAL);
327
328 /* convert the public key value into big-endian form */
329 memset(pub_key, 0, pub_key_len);
330 bn_bn2bin(dh->pub_key, pub_key + pub_key_len - len, len);
331
332 return 0;
333}
334
335int ff_dh_compute_shared_secret_key(FF_DH *dh, const uint8_t *pub_key,
336 int pub_key_len, uint8_t *secret_key,
337 int secret_key_len)
338{
339 FFBigNum q1 = NULL, pub_key_bn = NULL;
340 int ret;
341
342 /* convert the big-endian form of the public key into a bignum */
343 bn_bin2bn(pub_key_bn, pub_key, pub_key_len);
344 if (!pub_key_bn)
345 return AVERROR(ENOMEM);
346
347 /* convert the string containing a hexadecimal number into a bignum */
348 bn_hex2bn(q1, Q1024, ret);
349 if (!ret) {
350 ret = AVERROR(ENOMEM);
351 goto fail;
352 }
353
354 /* when the public key is valid we have to compute the shared secret key */
355 if ((ret = dh_is_valid_public_key(pub_key_bn, dh->p, q1)) < 0) {
356 goto fail;
357 } else if ((ret = dh_compute_key(dh, pub_key_bn, secret_key_len,
358 secret_key)) < 0) {
359 ret = AVERROR(EINVAL);
360 goto fail;
361 }
362
363fail:
364 bn_free(pub_key_bn);
365 bn_free(q1);
366
367 return ret;
368}
369
generated by cgit at 2024-05-17 08:36:42 (GMT)