2 * RTMP Diffie-Hellmann utilities
3 * Copyright (c) 2009 Andrej Stepanchuk
4 * Copyright (c) 2009-2010 Howard Chu
5 * Copyright (c) 2012 Samuel Pitoiset
7 * This file is part of FFmpeg.
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.
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.
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
26 * RTMP Diffie-Hellmann utilities
34 #include "libavutil/attributes.h"
35 #include "libavutil/error.h"
36 #include "libavutil/mem.h"
37 #include "libavutil/random_seed.h"
42 #include <mbedtls/ctr_drbg.h>
43 #include <mbedtls/entropy.h>
47 "FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD1" \
48 "29024E088A67CC74020BBEA63B139B22514A08798E3404DD" \
49 "EF9519B3CD3A431B302B0A6DF25F14374FE1356D6D51C245" \
50 "E485B576625E7EC6F44C42E9A637ED6B0BFF5CB6F406B7ED" \
51 "EE386BFB5A899FA5AE9F24117C4B1FE649286651ECE65381" \
55 "7FFFFFFFFFFFFFFFE487ED5110B4611A62633145C06E0E68" \
56 "948127044533E63A0105DF531D89CD9128A5043CC71A026E" \
57 "F7CA8CD9E69D218D98158536F92F8A1BA7F09AB6B6A8E122" \
58 "F242DABB312F3F637A262174D31BF6B585FFAE5B7A035BF6" \
59 "F71C35FDAD44CFD2D74F9208BE258FF324943328F67329C0" \
65 bn = av_malloc(sizeof(*bn)); \
74 #define bn_set_word(bn, w) mpz_set_ui(bn, w)
75 #define bn_cmp(a, b) mpz_cmp(a, b)
76 #define bn_copy(to, from) mpz_set(to, from)
77 #define bn_sub_word(bn, w) mpz_sub_ui(bn, bn, w)
78 #define bn_cmp_1(bn) mpz_cmp_ui(bn, 1)
79 #define bn_num_bytes(bn) (mpz_sizeinbase(bn, 2) + 7) / 8
80 #define bn_bn2bin(bn, buf, len) \
82 memset(buf, 0, len); \
83 if (bn_num_bytes(bn) <= len) \
84 mpz_export(buf, NULL, 1, 1, 0, 0, bn); \
86 #define bn_bin2bn(bn, buf, len) \
90 mpz_import(bn, len, 1, 1, 0, 0, buf); \
92 #define bn_hex2bn(bn, buf, ret) \
96 ret = (mpz_set_str(bn, buf, 16) == 0); \
100 #define bn_random(bn, num_bits) \
102 int bits = num_bits; \
104 for (bits = num_bits; bits > 0; bits -= 32) { \
105 mpz_mul_2exp(bn, bn, 32); \
106 mpz_add_ui(bn, bn, av_get_random_seed()); \
108 mpz_fdiv_r_2exp(bn, bn, num_bits); \
110 static int bn_modexp(FFBigNum bn, FFBigNum y, FFBigNum q, FFBigNum p)
112 mpz_powm(bn, y, q, p);
118 if (!gcry_control(GCRYCTL_INITIALIZATION_FINISHED_P)) { \
119 if (!gcry_check_version("1.5.4")) \
120 return AVERROR(EINVAL); \
121 gcry_control(GCRYCTL_DISABLE_SECMEM, 0); \
122 gcry_control(GCRYCTL_INITIALIZATION_FINISHED, 0); \
124 bn = gcry_mpi_new(1); \
126 #define bn_free(bn) gcry_mpi_release(bn)
127 #define bn_set_word(bn, w) gcry_mpi_set_ui(bn, w)
128 #define bn_cmp(a, b) gcry_mpi_cmp(a, b)
129 #define bn_copy(to, from) gcry_mpi_set(to, from)
130 #define bn_sub_word(bn, w) gcry_mpi_sub_ui(bn, bn, w)
131 #define bn_cmp_1(bn) gcry_mpi_cmp_ui(bn, 1)
132 #define bn_num_bytes(bn) (gcry_mpi_get_nbits(bn) + 7) / 8
133 #define bn_bn2bin(bn, buf, len) gcry_mpi_print(GCRYMPI_FMT_USG, buf, len, NULL, bn)
134 #define bn_bin2bn(bn, buf, len) gcry_mpi_scan(&bn, GCRYMPI_FMT_USG, buf, len, NULL)
135 #define bn_hex2bn(bn, buf, ret) ret = (gcry_mpi_scan(&bn, GCRYMPI_FMT_HEX, buf, 0, 0) == 0)
136 #define bn_random(bn, num_bits) gcry_mpi_randomize(bn, num_bits, GCRY_WEAK_RANDOM)
137 static int bn_modexp(FFBigNum bn, FFBigNum y, FFBigNum q, FFBigNum p)
139 gcry_mpi_powm(bn, y, q, p);
143 #define bn_new(bn) bn = BN_new()
144 #define bn_free(bn) BN_free(bn)
145 #define bn_set_word(bn, w) BN_set_word(bn, w)
146 #define bn_cmp(a, b) BN_cmp(a, b)
147 #define bn_copy(to, from) BN_copy(to, from)
148 #define bn_sub_word(bn, w) BN_sub_word(bn, w)
149 #define bn_cmp_1(bn) BN_cmp(bn, BN_value_one())
150 #define bn_num_bytes(bn) BN_num_bytes(bn)
151 #define bn_bn2bin(bn, buf, len) BN_bn2bin(bn, buf)
152 #define bn_bin2bn(bn, buf, len) bn = BN_bin2bn(buf, len, 0)
153 #define bn_hex2bn(bn, buf, ret) ret = BN_hex2bn(&bn, buf)
154 #define bn_random(bn, num_bits) BN_rand(bn, num_bits, 0, 0)
155 static int bn_modexp(FFBigNum bn, FFBigNum y, FFBigNum q, FFBigNum p)
157 BN_CTX *ctx = BN_CTX_new();
159 return AVERROR(ENOMEM);
160 if (!BN_mod_exp(bn, y, q, p, ctx)) {
162 return AVERROR(EINVAL);
170 bn = av_malloc(sizeof(*bn)); \
172 mbedtls_mpi_init(bn); \
174 #define bn_free(bn) \
176 mbedtls_mpi_free(bn); \
179 #define bn_set_word(bn, w) mbedtls_mpi_lset(bn, w)
180 #define bn_cmp(a, b) mbedtls_mpi_cmp_mpi(a, b)
181 #define bn_copy(to, from) mbedtls_mpi_copy(to, from)
182 #define bn_sub_word(bn, w) mbedtls_mpi_sub_int(bn, bn, w)
183 #define bn_cmp_1(bn) mbedtls_mpi_cmp_int(bn, 1)
184 #define bn_num_bytes(bn) (mbedtls_mpi_bitlen(bn) + 7) / 8
185 #define bn_bn2bin(bn, buf, len) mbedtls_mpi_write_binary(bn, buf, len)
186 #define bn_bin2bn(bn, buf, len) \
190 mbedtls_mpi_read_binary(bn, buf, len); \
192 #define bn_hex2bn(bn, buf, ret) \
196 ret = (mbedtls_mpi_read_string(bn, 16, buf) == 0); \
200 #define bn_random(bn, num_bits) \
202 mbedtls_entropy_context entropy_ctx; \
203 mbedtls_ctr_drbg_context ctr_drbg_ctx; \
205 mbedtls_entropy_init(&entropy_ctx); \
206 mbedtls_ctr_drbg_init(&ctr_drbg_ctx); \
207 mbedtls_ctr_drbg_seed(&ctr_drbg_ctx, \
208 mbedtls_entropy_func, \
211 mbedtls_mpi_fill_random(bn, (num_bits + 7) / 8, mbedtls_ctr_drbg_random, &ctr_drbg_ctx); \
212 mbedtls_ctr_drbg_free(&ctr_drbg_ctx); \
213 mbedtls_entropy_free(&entropy_ctx); \
215 #define bn_modexp(bn, y, q, p) mbedtls_mpi_exp_mod(bn, y, q, p, 0)
219 #define MAX_BYTES 18000
221 #define dh_new() av_mallocz(sizeof(FF_DH))
223 static FFBigNum dh_generate_key(FF_DH *dh)
227 num_bytes = bn_num_bytes(dh->p) - 1;
228 if (num_bytes <= 0 || num_bytes > MAX_BYTES)
231 bn_new(dh->priv_key);
234 bn_random(dh->priv_key, 8 * num_bytes);
238 bn_free(dh->priv_key);
242 if (bn_modexp(dh->pub_key, dh->g, dh->priv_key, dh->p) < 0)
248 static int dh_compute_key(FF_DH *dh, FFBigNum pub_key_bn,
249 uint32_t secret_key_len, uint8_t *secret_key)
258 if ((ret = bn_modexp(k, pub_key_bn, dh->priv_key, dh->p)) < 0) {
262 bn_bn2bin(k, secret_key, secret_key_len);
265 /* return the length of the shared secret key like DH_compute_key */
266 return secret_key_len;
269 void ff_dh_free(FF_DH *dh)
275 bn_free(dh->pub_key);
276 bn_free(dh->priv_key);
280 static int dh_is_valid_public_key(FFBigNum y, FFBigNum p, FFBigNum q)
283 int ret = AVERROR(EINVAL);
287 return AVERROR(ENOMEM);
289 /* y must lie in [2, p - 1] */
300 /* Verify with Sophie-Germain prime
302 * This is a nice test to make sure the public key position is calculated
303 * correctly. This test will fail in about 50% of the cases if applied to
306 /* y must fulfill y^q mod p = 1 */
307 if ((ret = bn_modexp(bn, y, q, p)) < 0)
310 ret = AVERROR(EINVAL);
321 av_cold FF_DH *ff_dh_init(int key_len)
326 if (!(dh = dh_new()))
333 bn_hex2bn(dh->p, P1024, ret);
337 bn_set_word(dh->g, 2);
338 dh->length = key_len;
348 int ff_dh_generate_public_key(FF_DH *dh)
355 if (!dh_generate_key(dh))
356 return AVERROR(EINVAL);
358 bn_hex2bn(q1, Q1024, ret);
360 return AVERROR(ENOMEM);
362 ret = dh_is_valid_public_key(dh->pub_key, dh->p, q1);
366 /* the public key is valid */
374 int ff_dh_write_public_key(FF_DH *dh, uint8_t *pub_key, int pub_key_len)
378 /* compute the length of the public key */
379 len = bn_num_bytes(dh->pub_key);
380 if (len <= 0 || len > pub_key_len)
381 return AVERROR(EINVAL);
383 /* convert the public key value into big-endian form */
384 memset(pub_key, 0, pub_key_len);
385 bn_bn2bin(dh->pub_key, pub_key + pub_key_len - len, len);
390 int ff_dh_compute_shared_secret_key(FF_DH *dh, const uint8_t *pub_key,
391 int pub_key_len, uint8_t *secret_key,
394 FFBigNum q1 = NULL, pub_key_bn = NULL;
397 /* convert the big-endian form of the public key into a bignum */
398 bn_bin2bn(pub_key_bn, pub_key, pub_key_len);
400 return AVERROR(ENOMEM);
402 /* convert the string containing a hexadecimal number into a bignum */
403 bn_hex2bn(q1, Q1024, ret);
405 ret = AVERROR(ENOMEM);
409 /* when the public key is valid we have to compute the shared secret key */
410 if ((ret = dh_is_valid_public_key(pub_key_bn, dh->p, q1)) < 0) {
412 } else if ((ret = dh_compute_key(dh, pub_key_bn, secret_key_len,
414 ret = AVERROR(EINVAL);