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 "FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD1" \
43 "29024E088A67CC74020BBEA63B139B22514A08798E3404DD" \
44 "EF9519B3CD3A431B302B0A6DF25F14374FE1356D6D51C245" \
45 "E485B576625E7EC6F44C42E9A637ED6B0BFF5CB6F406B7ED" \
46 "EE386BFB5A899FA5AE9F24117C4B1FE649286651ECE65381" \
50 "7FFFFFFFFFFFFFFFE487ED5110B4611A62633145C06E0E68" \
51 "948127044533E63A0105DF531D89CD9128A5043CC71A026E" \
52 "F7CA8CD9E69D218D98158536F92F8A1BA7F09AB6B6A8E122" \
53 "F242DABB312F3F637A262174D31BF6B585FFAE5B7A035BF6" \
54 "F71C35FDAD44CFD2D74F9208BE258FF324943328F67329C0" \
57 #if CONFIG_GMP || CONFIG_GCRYPT
61 bn = av_malloc(sizeof(*bn)); \
70 #define bn_set_word(bn, w) mpz_set_ui(bn, w)
71 #define bn_cmp(a, b) mpz_cmp(a, b)
72 #define bn_copy(to, from) mpz_set(to, from)
73 #define bn_sub_word(bn, w) mpz_sub_ui(bn, bn, w)
74 #define bn_cmp_1(bn) mpz_cmp_ui(bn, 1)
75 #define bn_num_bytes(bn) (mpz_sizeinbase(bn, 2) + 7) / 8
76 #define bn_bn2bin(bn, buf, len) \
78 memset(buf, 0, len); \
79 if (bn_num_bytes(bn) <= len) \
80 mpz_export(buf, NULL, 1, 1, 0, 0, bn); \
82 #define bn_bin2bn(bn, buf, len) \
86 mpz_import(bn, len, 1, 1, 0, 0, buf); \
88 #define bn_hex2bn(bn, buf, ret) \
92 ret = (mpz_set_str(bn, buf, 16) == 0); \
96 #define bn_modexp(bn, y, q, p) mpz_powm(bn, y, q, p)
97 #define bn_random(bn, num_bits) \
99 int bits = num_bits; \
101 for (bits = num_bits; bits > 0; bits -= 32) { \
102 mpz_mul_2exp(bn, bn, 32); \
103 mpz_add_ui(bn, bn, av_get_random_seed()); \
105 mpz_fdiv_r_2exp(bn, bn, num_bits); \
110 if (!gcry_control(GCRYCTL_INITIALIZATION_FINISHED_P)) { \
111 if (!gcry_check_version("1.5.4")) \
112 return AVERROR(EINVAL); \
113 gcry_control(GCRYCTL_DISABLE_SECMEM, 0); \
114 gcry_control(GCRYCTL_INITIALIZATION_FINISHED, 0); \
116 bn = gcry_mpi_new(1); \
118 #define bn_free(bn) gcry_mpi_release(bn)
119 #define bn_set_word(bn, w) gcry_mpi_set_ui(bn, w)
120 #define bn_cmp(a, b) gcry_mpi_cmp(a, b)
121 #define bn_copy(to, from) gcry_mpi_set(to, from)
122 #define bn_sub_word(bn, w) gcry_mpi_sub_ui(bn, bn, w)
123 #define bn_cmp_1(bn) gcry_mpi_cmp_ui(bn, 1)
124 #define bn_num_bytes(bn) (gcry_mpi_get_nbits(bn) + 7) / 8
125 #define bn_bn2bin(bn, buf, len) gcry_mpi_print(GCRYMPI_FMT_USG, buf, len, NULL, bn)
126 #define bn_bin2bn(bn, buf, len) gcry_mpi_scan(&bn, GCRYMPI_FMT_USG, buf, len, NULL)
127 #define bn_hex2bn(bn, buf, ret) ret = (gcry_mpi_scan(&bn, GCRYMPI_FMT_HEX, buf, 0, 0) == 0)
128 #define bn_modexp(bn, y, q, p) gcry_mpi_powm(bn, y, q, p)
129 #define bn_random(bn, num_bits) gcry_mpi_randomize(bn, num_bits, GCRY_WEAK_RANDOM)
132 #define MAX_BYTES 18000
134 #define dh_new() av_malloc(sizeof(FF_DH))
136 static FFBigNum dh_generate_key(FF_DH *dh)
140 num_bytes = bn_num_bytes(dh->p) - 1;
141 if (num_bytes <= 0 || num_bytes > MAX_BYTES)
144 bn_new(dh->priv_key);
147 bn_random(dh->priv_key, 8 * num_bytes);
151 bn_free(dh->priv_key);
155 bn_modexp(dh->pub_key, dh->g, dh->priv_key, dh->p);
160 static int dh_compute_key(FF_DH *dh, FFBigNum pub_key_bn,
161 uint32_t secret_key_len, uint8_t *secret_key)
169 bn_modexp(k, pub_key_bn, dh->priv_key, dh->p);
170 bn_bn2bin(k, secret_key, secret_key_len);
173 /* return the length of the shared secret key like DH_compute_key */
174 return secret_key_len;
177 void ff_dh_free(FF_DH *dh)
183 bn_free(dh->pub_key);
184 bn_free(dh->priv_key);
188 #define bn_new(bn) bn = BN_new()
189 #define bn_free(bn) BN_free(bn)
190 #define bn_set_word(bn, w) BN_set_word(bn, w)
191 #define bn_cmp(a, b) BN_cmp(a, b)
192 #define bn_copy(to, from) BN_copy(to, from)
193 #define bn_sub_word(bn, w) BN_sub_word(bn, w)
194 #define bn_cmp_1(bn) BN_cmp(bn, BN_value_one())
195 #define bn_num_bytes(bn) BN_num_bytes(bn)
196 #define bn_bn2bin(bn, buf, len) BN_bn2bin(bn, buf)
197 #define bn_bin2bn(bn, buf, len) bn = BN_bin2bn(buf, len, 0)
198 #define bn_hex2bn(bn, buf, ret) ret = BN_hex2bn(&bn, buf)
199 #define bn_modexp(bn, y, q, p) \
201 BN_CTX *ctx = BN_CTX_new(); \
203 return AVERROR(ENOMEM); \
204 if (!BN_mod_exp(bn, y, q, p, ctx)) { \
206 return AVERROR(EINVAL); \
211 #define dh_new() DH_new()
212 #define dh_generate_key(dh) DH_generate_key(dh)
214 static int dh_compute_key(FF_DH *dh, FFBigNum pub_key_bn,
215 uint32_t secret_key_len, uint8_t *secret_key)
217 if (secret_key_len < DH_size(dh))
218 return AVERROR(EINVAL);
219 return DH_compute_key(secret_key, pub_key_bn, dh);
222 void ff_dh_free(FF_DH *dh)
230 static int dh_is_valid_public_key(FFBigNum y, FFBigNum p, FFBigNum q)
233 int ret = AVERROR(EINVAL);
237 return AVERROR(ENOMEM);
239 /* y must lie in [2, p - 1] */
250 /* Verify with Sophie-Germain prime
252 * This is a nice test to make sure the public key position is calculated
253 * correctly. This test will fail in about 50% of the cases if applied to
256 /* y must fulfill y^q mod p = 1 */
257 bn_modexp(bn, y, q, p);
269 av_cold FF_DH *ff_dh_init(int key_len)
274 if (!(dh = dh_new()))
281 bn_hex2bn(dh->p, P1024, ret);
285 bn_set_word(dh->g, 2);
286 dh->length = key_len;
296 int ff_dh_generate_public_key(FF_DH *dh)
303 if (!dh_generate_key(dh))
304 return AVERROR(EINVAL);
306 bn_hex2bn(q1, Q1024, ret);
308 return AVERROR(ENOMEM);
310 ret = dh_is_valid_public_key(dh->pub_key, dh->p, q1);
314 /* the public key is valid */
322 int ff_dh_write_public_key(FF_DH *dh, uint8_t *pub_key, int pub_key_len)
326 /* compute the length of the public key */
327 len = bn_num_bytes(dh->pub_key);
328 if (len <= 0 || len > pub_key_len)
329 return AVERROR(EINVAL);
331 /* convert the public key value into big-endian form */
332 memset(pub_key, 0, pub_key_len);
333 bn_bn2bin(dh->pub_key, pub_key + pub_key_len - len, len);
338 int ff_dh_compute_shared_secret_key(FF_DH *dh, const uint8_t *pub_key,
339 int pub_key_len, uint8_t *secret_key,
342 FFBigNum q1 = NULL, pub_key_bn = NULL;
345 /* convert the big-endian form of the public key into a bignum */
346 bn_bin2bn(pub_key_bn, pub_key, pub_key_len);
348 return AVERROR(ENOMEM);
350 /* convert the string containing a hexadecimal number into a bignum */
351 bn_hex2bn(q1, Q1024, ret);
353 ret = AVERROR(ENOMEM);
357 /* when the public key is valid we have to compute the shared secret key */
358 if ((ret = dh_is_valid_public_key(pub_key_bn, dh->p, q1)) < 0) {
360 } else if ((ret = dh_compute_key(dh, pub_key_bn, secret_key_len,
362 ret = AVERROR(EINVAL);