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 Libav.
9 * Libav 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 * Libav 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 Libav; 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
31 #include "libavutil/random_seed.h"
34 "FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD1" \
35 "29024E088A67CC74020BBEA63B139B22514A08798E3404DD" \
36 "EF9519B3CD3A431B302B0A6DF25F14374FE1356D6D51C245" \
37 "E485B576625E7EC6F44C42E9A637ED6B0BFF5CB6F406B7ED" \
38 "EE386BFB5A899FA5AE9F24117C4B1FE649286651ECE65381" \
42 "7FFFFFFFFFFFFFFFE487ED5110B4611A62633145C06E0E68" \
43 "948127044533E63A0105DF531D89CD9128A5043CC71A026E" \
44 "F7CA8CD9E69D218D98158536F92F8A1BA7F09AB6B6A8E122" \
45 "F242DABB312F3F637A262174D31BF6B585FFAE5B7A035BF6" \
46 "F71C35FDAD44CFD2D74F9208BE258FF324943328F67329C0" \
49 #if CONFIG_NETTLE || CONFIG_GCRYPT
53 bn = av_malloc(sizeof(*bn)); \
62 #define bn_set_word(bn, w) mpz_set_ui(bn, w)
63 #define bn_cmp(a, b) mpz_cmp(a, b)
64 #define bn_copy(to, from) mpz_set(to, from)
65 #define bn_sub_word(bn, w) mpz_sub_ui(bn, bn, w)
66 #define bn_cmp_1(bn) mpz_cmp_ui(bn, 1)
67 #define bn_num_bytes(bn) (mpz_sizeinbase(bn, 2) + 7) / 8
68 #define bn_bn2bin(bn, buf, len) nettle_mpz_get_str_256(len, buf, bn)
69 #define bn_bin2bn(bn, buf, len) \
73 nettle_mpz_set_str_256_u(bn, len, buf); \
75 #define bn_hex2bn(bn, buf, ret) \
79 ret = (mpz_set_str(bn, buf, 16) == 0); \
83 #define bn_modexp(bn, y, q, p) mpz_powm(bn, y, q, p)
84 #define bn_random(bn, num_bytes) \
87 gmp_randinit_mt(rs); \
88 gmp_randseed_ui(rs, av_get_random_seed()); \
89 mpz_urandomb(bn, rs, num_bytes); \
93 #define bn_new(bn) bn = gcry_mpi_new(1)
94 #define bn_free(bn) gcry_mpi_release(bn)
95 #define bn_set_word(bn, w) gcry_mpi_set_ui(bn, w)
96 #define bn_cmp(a, b) gcry_mpi_cmp(a, b)
97 #define bn_copy(to, from) gcry_mpi_set(to, from)
98 #define bn_sub_word(bn, w) gcry_mpi_sub_ui(bn, bn, w)
99 #define bn_cmp_1(bn) gcry_mpi_cmp_ui(bn, 1)
100 #define bn_num_bytes(bn) (gcry_mpi_get_nbits(bn) + 7) / 8
101 #define bn_bn2bin(bn, buf, len) gcry_mpi_print(GCRYMPI_FMT_USG, buf, len, NULL, bn)
102 #define bn_bin2bn(bn, buf, len) gcry_mpi_scan(&bn, GCRYMPI_FMT_USG, buf, len, NULL)
103 #define bn_hex2bn(bn, buf, ret) ret = (gcry_mpi_scan(&bn, GCRYMPI_FMT_HEX, buf, 0, 0) == 0)
104 #define bn_modexp(bn, y, q, p) gcry_mpi_powm(bn, y, q, p)
105 #define bn_random(bn, num_bytes) gcry_mpi_randomize(bn, num_bytes, GCRY_WEAK_RANDOM)
108 #define MAX_BYTES 18000
110 #define dh_new() av_malloc(sizeof(FF_DH))
112 static FFBigNum dh_generate_key(FF_DH *dh)
116 num_bytes = bn_num_bytes(dh->p) - 1;
117 if (num_bytes <= 0 || num_bytes > MAX_BYTES)
120 bn_new(dh->priv_key);
123 bn_random(dh->priv_key, num_bytes);
127 bn_free(dh->priv_key);
131 bn_modexp(dh->pub_key, dh->g, dh->priv_key, dh->p);
136 static int dh_compute_key(FF_DH *dh, FFBigNum pub_key_bn,
137 uint32_t secret_key_len, uint8_t *secret_key)
142 num_bytes = bn_num_bytes(dh->p);
143 if (num_bytes <= 0 || num_bytes > MAX_BYTES)
150 bn_modexp(k, pub_key_bn, dh->priv_key, dh->p);
151 bn_bn2bin(k, secret_key, secret_key_len);
154 /* return the length of the shared secret key like DH_compute_key */
155 return secret_key_len;
158 void ff_dh_free(FF_DH *dh)
162 bn_free(dh->pub_key);
163 bn_free(dh->priv_key);
167 #define bn_new(bn) bn = BN_new()
168 #define bn_free(bn) BN_free(bn)
169 #define bn_set_word(bn, w) BN_set_word(bn, w)
170 #define bn_cmp(a, b) BN_cmp(a, b)
171 #define bn_copy(to, from) BN_copy(to, from)
172 #define bn_sub_word(bn, w) BN_sub_word(bn, w)
173 #define bn_cmp_1(bn) BN_cmp(bn, BN_value_one())
174 #define bn_num_bytes(bn) BN_num_bytes(bn)
175 #define bn_bn2bin(bn, buf, len) BN_bn2bin(bn, buf)
176 #define bn_bin2bn(bn, buf, len) bn = BN_bin2bn(buf, len, 0)
177 #define bn_hex2bn(bn, buf, ret) ret = BN_hex2bn(&bn, buf)
178 #define bn_modexp(bn, y, q, p) \
180 BN_CTX *ctx = BN_CTX_new(); \
182 return AVERROR(ENOMEM); \
183 if (!BN_mod_exp(bn, y, q, p, ctx)) { \
185 return AVERROR(EINVAL); \
190 #define dh_new() DH_new()
191 #define dh_generate_key(dh) DH_generate_key(dh)
193 static int dh_compute_key(FF_DH *dh, FFBigNum pub_key_bn,
194 uint32_t secret_key_len, uint8_t *secret_key)
196 if (secret_key_len < DH_size(dh))
197 return AVERROR(EINVAL);
198 return DH_compute_key(secret_key, pub_key_bn, dh);
201 void ff_dh_free(FF_DH *dh)
207 static int dh_is_valid_public_key(FFBigNum y, FFBigNum p, FFBigNum q)
210 int ret = AVERROR(EINVAL);
214 return AVERROR(ENOMEM);
216 /* y must lie in [2, p - 1] */
227 /* Verify with Sophie-Germain prime
229 * This is a nice test to make sure the public key position is calculated
230 * correctly. This test will fail in about 50% of the cases if applied to
233 /* y must fulfill y^q mod p = 1 */
234 bn_modexp(bn, y, q, p);
246 av_cold FF_DH *ff_dh_init(int key_len)
251 if (!(dh = dh_new()))
258 bn_hex2bn(dh->p, P1024, ret);
262 bn_set_word(dh->g, 2);
263 dh->length = key_len;
273 int ff_dh_generate_public_key(FF_DH *dh)
280 if (!dh_generate_key(dh))
281 return AVERROR(EINVAL);
283 bn_hex2bn(q1, Q1024, ret);
285 return AVERROR(ENOMEM);
287 ret = dh_is_valid_public_key(dh->pub_key, dh->p, q1);
291 /* the public key is valid */
299 int ff_dh_write_public_key(FF_DH *dh, uint8_t *pub_key, int pub_key_len)
303 /* compute the length of the public key */
304 len = bn_num_bytes(dh->pub_key);
305 if (len <= 0 || len > pub_key_len)
306 return AVERROR(EINVAL);
308 /* convert the public key value into big-endian form */
309 memset(pub_key, 0, pub_key_len);
310 bn_bn2bin(dh->pub_key, pub_key + pub_key_len - len, len);
315 int ff_dh_compute_shared_secret_key(FF_DH *dh, const uint8_t *pub_key,
316 int pub_key_len, uint8_t *secret_key,
319 FFBigNum q1 = NULL, pub_key_bn = NULL;
322 /* convert the big-endian form of the public key into a bignum */
323 bn_bin2bn(pub_key_bn, pub_key, pub_key_len);
325 return AVERROR(ENOMEM);
327 /* convert the string containing a hexadecimal number into a bignum */
328 bn_hex2bn(q1, Q1024, ret);
330 ret = AVERROR(ENOMEM);
334 /* when the public key is valid we have to compute the shared secret key */
335 if ((ret = dh_is_valid_public_key(pub_key_bn, dh->p, q1)) < 0) {
337 } else if ((ret = dh_compute_key(dh, pub_key_bn, secret_key_len,
339 ret = AVERROR(EINVAL);