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
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" \
60 bn = av_malloc(sizeof(*bn)); \
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) \
77 memset(buf, 0, len); \
78 if (bn_num_bytes(bn) <= len) \
79 mpz_export(buf, NULL, 1, 1, 0, 0, bn); \
81 #define bn_bin2bn(bn, buf, len) \
85 mpz_import(bn, len, 1, 1, 0, 0, buf); \
87 #define bn_hex2bn(bn, buf, ret) \
91 ret = (mpz_set_str(bn, buf, 16) == 0); \
95 #define bn_random(bn, num_bits) \
97 int bits = num_bits; \
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()); \
103 mpz_fdiv_r_2exp(bn, bn, num_bits); \
105 static int bn_modexp(FFBigNum bn, FFBigNum y, FFBigNum q, FFBigNum p)
107 mpz_powm(bn, y, q, p);
111 #define bn_new(bn) bn = gcry_mpi_new(1)
112 #define bn_free(bn) gcry_mpi_release(bn)
113 #define bn_set_word(bn, w) gcry_mpi_set_ui(bn, w)
114 #define bn_cmp(a, b) gcry_mpi_cmp(a, b)
115 #define bn_copy(to, from) gcry_mpi_set(to, from)
116 #define bn_sub_word(bn, w) gcry_mpi_sub_ui(bn, bn, w)
117 #define bn_cmp_1(bn) gcry_mpi_cmp_ui(bn, 1)
118 #define bn_num_bytes(bn) (gcry_mpi_get_nbits(bn) + 7) / 8
119 #define bn_bn2bin(bn, buf, len) gcry_mpi_print(GCRYMPI_FMT_USG, buf, len, NULL, bn)
120 #define bn_bin2bn(bn, buf, len) gcry_mpi_scan(&bn, GCRYMPI_FMT_USG, buf, len, NULL)
121 #define bn_hex2bn(bn, buf, ret) ret = (gcry_mpi_scan(&bn, GCRYMPI_FMT_HEX, buf, 0, 0) == 0)
122 #define bn_random(bn, num_bits) gcry_mpi_randomize(bn, num_bits, GCRY_WEAK_RANDOM)
123 static int bn_modexp(FFBigNum bn, FFBigNum y, FFBigNum q, FFBigNum p)
125 gcry_mpi_powm(bn, y, q, p);
129 #define bn_new(bn) bn = BN_new()
130 #define bn_free(bn) BN_free(bn)
131 #define bn_set_word(bn, w) BN_set_word(bn, w)
132 #define bn_cmp(a, b) BN_cmp(a, b)
133 #define bn_copy(to, from) BN_copy(to, from)
134 #define bn_sub_word(bn, w) BN_sub_word(bn, w)
135 #define bn_cmp_1(bn) BN_cmp(bn, BN_value_one())
136 #define bn_num_bytes(bn) BN_num_bytes(bn)
137 #define bn_bn2bin(bn, buf, len) BN_bn2bin(bn, buf)
138 #define bn_bin2bn(bn, buf, len) bn = BN_bin2bn(buf, len, 0)
139 #define bn_hex2bn(bn, buf, ret) ret = BN_hex2bn(&bn, buf)
140 #define bn_random(bn, num_bits) BN_rand(bn, num_bits, 0, 0)
141 static int bn_modexp(FFBigNum bn, FFBigNum y, FFBigNum q, FFBigNum p)
143 BN_CTX *ctx = BN_CTX_new();
145 return AVERROR(ENOMEM);
146 if (!BN_mod_exp(bn, y, q, p, ctx)) {
148 return AVERROR(EINVAL);
155 #define MAX_BYTES 18000
157 #define dh_new() av_mallocz(sizeof(FF_DH))
159 static FFBigNum dh_generate_key(FF_DH *dh)
163 num_bytes = bn_num_bytes(dh->p) - 1;
164 if (num_bytes <= 0 || num_bytes > MAX_BYTES)
167 bn_new(dh->priv_key);
170 bn_random(dh->priv_key, 8 * num_bytes);
174 bn_free(dh->priv_key);
178 if (bn_modexp(dh->pub_key, dh->g, dh->priv_key, dh->p) < 0)
184 static int dh_compute_key(FF_DH *dh, FFBigNum pub_key_bn,
185 uint32_t secret_key_len, uint8_t *secret_key)
194 if ((ret = bn_modexp(k, pub_key_bn, dh->priv_key, dh->p)) < 0) {
198 bn_bn2bin(k, secret_key, secret_key_len);
201 /* return the length of the shared secret key like DH_compute_key */
202 return secret_key_len;
205 void ff_dh_free(FF_DH *dh)
211 bn_free(dh->pub_key);
212 bn_free(dh->priv_key);
216 static int dh_is_valid_public_key(FFBigNum y, FFBigNum p, FFBigNum q)
219 int ret = AVERROR(EINVAL);
223 return AVERROR(ENOMEM);
225 /* y must lie in [2, p - 1] */
236 /* Verify with Sophie-Germain prime
238 * This is a nice test to make sure the public key position is calculated
239 * correctly. This test will fail in about 50% of the cases if applied to
242 /* y must fulfill y^q mod p = 1 */
243 if ((ret = bn_modexp(bn, y, q, p)) < 0)
246 ret = AVERROR(EINVAL);
257 av_cold FF_DH *ff_dh_init(int key_len)
262 if (!(dh = dh_new()))
269 bn_hex2bn(dh->p, P1024, ret);
273 bn_set_word(dh->g, 2);
274 dh->length = key_len;
284 int ff_dh_generate_public_key(FF_DH *dh)
291 if (!dh_generate_key(dh))
292 return AVERROR(EINVAL);
294 bn_hex2bn(q1, Q1024, ret);
296 return AVERROR(ENOMEM);
298 ret = dh_is_valid_public_key(dh->pub_key, dh->p, q1);
302 /* the public key is valid */
310 int ff_dh_write_public_key(FF_DH *dh, uint8_t *pub_key, int pub_key_len)
314 /* compute the length of the public key */
315 len = bn_num_bytes(dh->pub_key);
316 if (len <= 0 || len > pub_key_len)
317 return AVERROR(EINVAL);
319 /* convert the public key value into big-endian form */
320 memset(pub_key, 0, pub_key_len);
321 bn_bn2bin(dh->pub_key, pub_key + pub_key_len - len, len);
326 int ff_dh_compute_shared_secret_key(FF_DH *dh, const uint8_t *pub_key,
327 int pub_key_len, uint8_t *secret_key,
330 FFBigNum q1 = NULL, pub_key_bn = NULL;
333 /* convert the big-endian form of the public key into a bignum */
334 bn_bin2bn(pub_key_bn, pub_key, pub_key_len);
336 return AVERROR(ENOMEM);
338 /* convert the string containing a hexadecimal number into a bignum */
339 bn_hex2bn(q1, Q1024, ret);
341 ret = AVERROR(ENOMEM);
345 /* when the public key is valid we have to compute the shared secret key */
346 if ((ret = dh_is_valid_public_key(pub_key_bn, dh->p, q1)) < 0) {
348 } else if ((ret = dh_compute_key(dh, pub_key_bn, secret_key_len,
350 ret = AVERROR(EINVAL);