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
33 "FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD1" \
34 "29024E088A67CC74020BBEA63B139B22514A08798E3404DD" \
35 "EF9519B3CD3A431B302B0A6DF25F14374FE1356D6D51C245" \
36 "E485B576625E7EC6F44C42E9A637ED6B0BFF5CB6F406B7ED" \
37 "EE386BFB5A899FA5AE9F24117C4B1FE649286651ECE65381" \
41 "7FFFFFFFFFFFFFFFE487ED5110B4611A62633145C06E0E68" \
42 "948127044533E63A0105DF531D89CD9128A5043CC71A026E" \
43 "F7CA8CD9E69D218D98158536F92F8A1BA7F09AB6B6A8E122" \
44 "F242DABB312F3F637A262174D31BF6B585FFAE5B7A035BF6" \
45 "F71C35FDAD44CFD2D74F9208BE258FF324943328F67329C0" \
48 #if CONFIG_NETTLE || CONFIG_GCRYPT
52 bn = av_malloc(sizeof(*bn)); \
61 #define bn_set_word(bn, w) mpz_set_ui(bn, w)
62 #define bn_cmp(a, b) mpz_cmp(a, b)
63 #define bn_copy(to, from) mpz_set(to, from)
64 #define bn_sub_word(bn, w) mpz_sub_ui(bn, bn, w)
65 #define bn_cmp_1(bn) mpz_cmp_ui(bn, 1)
66 #define bn_num_bytes(bn) (mpz_sizeinbase(bn, 2) + 7) / 8
67 #define bn_bn2bin(bn, buf, len) nettle_mpz_get_str_256(len, buf, bn)
68 #define bn_bin2bn(bn, buf, len) \
72 nettle_mpz_set_str_256_u(bn, len, buf); \
74 #define bn_hex2bn(bn, buf, ret) \
78 ret = (mpz_set_str(bn, buf, 16) == 0); \
80 #define bn_modexp(bn, y, q, p) mpz_powm(bn, y, q, p)
81 #define bn_random(bn, num_bytes) mpz_random(bn, num_bytes);
83 #define bn_new(bn) bn = gcry_mpi_new(1)
84 #define bn_free(bn) gcry_mpi_release(bn)
85 #define bn_set_word(bn, w) gcry_mpi_set_ui(bn, w)
86 #define bn_cmp(a, b) gcry_mpi_cmp(a, b)
87 #define bn_copy(to, from) gcry_mpi_set(to, from)
88 #define bn_sub_word(bn, w) gcry_mpi_sub_ui(bn, bn, w)
89 #define bn_cmp_1(bn) gcry_mpi_cmp_ui(bn, 1)
90 #define bn_num_bytes(bn) (gcry_mpi_get_nbits(bn) + 7) / 8
91 #define bn_bn2bin(bn, buf, len) gcry_mpi_print(GCRYMPI_FMT_USG, buf, len, NULL, bn)
92 #define bn_bin2bn(bn, buf, len) gcry_mpi_scan(&bn, GCRYMPI_FMT_USG, buf, len, NULL)
93 #define bn_hex2bn(bn, buf, ret) ret = (gcry_mpi_scan(&bn, GCRYMPI_FMT_HEX, buf, 0, 0) == 0)
94 #define bn_modexp(bn, y, q, p) gcry_mpi_powm(bn, y, q, p)
95 #define bn_random(bn, num_bytes) gcry_mpi_randomize(bn, num_bytes, GCRY_WEAK_RANDOM)
98 #define MAX_BYTES 18000
100 #define dh_new() av_malloc(sizeof(FF_DH))
102 static FFBigNum dh_generate_key(FF_DH *dh)
106 num_bytes = bn_num_bytes(dh->p) - 1;
107 if (num_bytes <= 0 || num_bytes > MAX_BYTES)
110 bn_new(dh->priv_key);
113 bn_random(dh->priv_key, num_bytes);
117 bn_free(dh->priv_key);
121 bn_modexp(dh->pub_key, dh->g, dh->priv_key, dh->p);
126 static int dh_compute_key(FF_DH *dh, FFBigNum pub_key_bn,
127 uint32_t pub_key_len, uint8_t *secret_key)
132 num_bytes = bn_num_bytes(dh->p);
133 if (num_bytes <= 0 || num_bytes > MAX_BYTES)
140 bn_modexp(k, pub_key_bn, dh->priv_key, dh->p);
141 bn_bn2bin(k, secret_key, pub_key_len);
144 /* return the length of the shared secret key like DH_compute_key */
148 void ff_dh_free(FF_DH *dh)
152 bn_free(dh->pub_key);
153 bn_free(dh->priv_key);
157 #define bn_new(bn) bn = BN_new()
158 #define bn_free(bn) BN_free(bn)
159 #define bn_set_word(bn, w) BN_set_word(bn, w)
160 #define bn_cmp(a, b) BN_cmp(a, b)
161 #define bn_copy(to, from) BN_copy(to, from)
162 #define bn_sub_word(bn, w) BN_sub_word(bn, w)
163 #define bn_cmp_1(bn) BN_cmp(bn, BN_value_one())
164 #define bn_num_bytes(bn) BN_num_bytes(bn)
165 #define bn_bn2bin(bn, buf, len) BN_bn2bin(bn, buf)
166 #define bn_bin2bn(bn, buf, len) bn = BN_bin2bn(buf, len, 0)
167 #define bn_hex2bn(bn, buf, ret) ret = BN_hex2bn(&bn, buf)
168 #define bn_modexp(bn, y, q, p) \
170 BN_CTX *ctx = BN_CTX_new(); \
172 return AVERROR(ENOMEM); \
173 if (!BN_mod_exp(bn, y, q, p, ctx)) { \
175 return AVERROR(EINVAL); \
180 #define dh_new() DH_new()
181 #define dh_generate_key(dh) DH_generate_key(dh)
182 #define dh_compute_key(dh, pub, len, secret) DH_compute_key(secret, pub, dh)
184 void ff_dh_free(FF_DH *dh)
190 static int dh_is_valid_public_key(FFBigNum y, FFBigNum p, FFBigNum q)
193 int ret = AVERROR(EINVAL);
197 return AVERROR(ENOMEM);
199 /* y must lie in [2, p - 1] */
210 /* Verify with Sophie-Germain prime
212 * This is a nice test to make sure the public key position is calculated
213 * correctly. This test will fail in about 50% of the cases if applied to
216 /* y must fulfill y^q mod p = 1 */
217 bn_modexp(bn, y, q, p);
229 av_cold FF_DH *ff_dh_init(int key_len)
234 if (!(dh = dh_new()))
241 bn_hex2bn(dh->p, P1024, ret);
245 bn_set_word(dh->g, 2);
246 dh->length = key_len;
256 int ff_dh_generate_public_key(FF_DH *dh)
263 if (!dh_generate_key(dh))
264 return AVERROR(EINVAL);
266 bn_hex2bn(q1, Q1024, ret);
268 return AVERROR(ENOMEM);
270 ret = dh_is_valid_public_key(dh->pub_key, dh->p, q1);
274 /* the public key is valid */
282 int ff_dh_write_public_key(FF_DH *dh, uint8_t *pub_key, int pub_key_len)
286 /* compute the length of the public key */
287 len = bn_num_bytes(dh->pub_key);
288 if (len <= 0 || len > pub_key_len)
289 return AVERROR(EINVAL);
291 /* convert the public key value into big-endian form */
292 memset(pub_key, 0, pub_key_len);
293 bn_bn2bin(dh->pub_key, pub_key + pub_key_len - len, len);
298 int ff_dh_compute_shared_secret_key(FF_DH *dh, const uint8_t *pub_key,
299 int pub_key_len, uint8_t *secret_key)
301 FFBigNum q1 = NULL, pub_key_bn = NULL;
304 /* convert the big-endian form of the public key into a bignum */
305 bn_bin2bn(pub_key_bn, pub_key, pub_key_len);
307 return AVERROR(ENOMEM);
309 /* convert the string containing a hexadecimal number into a bignum */
310 bn_hex2bn(q1, Q1024, ret);
312 ret = AVERROR(ENOMEM);
316 /* when the public key is valid we have to compute the shared secret key */
317 if ((ret = dh_is_valid_public_key(pub_key_bn, dh->p, q1)) < 0) {
319 } else if ((ret = dh_compute_key(dh, pub_key_bn, pub_key_len,
321 ret = AVERROR(EINVAL);