yading@11: /* yading@11: * RTMP Diffie-Hellmann utilities yading@11: * Copyright (c) 2009 Andrej Stepanchuk yading@11: * Copyright (c) 2009-2010 Howard Chu yading@11: * Copyright (c) 2012 Samuel Pitoiset yading@11: * yading@11: * This file is part of FFmpeg. yading@11: * yading@11: * FFmpeg is free software; you can redistribute it and/or yading@11: * modify it under the terms of the GNU Lesser General Public yading@11: * License as published by the Free Software Foundation; either yading@11: * version 2.1 of the License, or (at your option) any later version. yading@11: * yading@11: * FFmpeg is distributed in the hope that it will be useful, yading@11: * but WITHOUT ANY WARRANTY; without even the implied warranty of yading@11: * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU yading@11: * Lesser General Public License for more details. yading@11: * yading@11: * You should have received a copy of the GNU Lesser General Public yading@11: * License along with FFmpeg; if not, write to the Free Software yading@11: * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA yading@11: */ yading@11: yading@11: /** yading@11: * @file yading@11: * RTMP Diffie-Hellmann utilities yading@11: */ yading@11: yading@11: #include "config.h" yading@11: #include "rtmpdh.h" yading@11: #include "libavutil/random_seed.h" yading@11: yading@11: #define P1024 \ yading@11: "FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD1" \ yading@11: "29024E088A67CC74020BBEA63B139B22514A08798E3404DD" \ yading@11: "EF9519B3CD3A431B302B0A6DF25F14374FE1356D6D51C245" \ yading@11: "E485B576625E7EC6F44C42E9A637ED6B0BFF5CB6F406B7ED" \ yading@11: "EE386BFB5A899FA5AE9F24117C4B1FE649286651ECE65381" \ yading@11: "FFFFFFFFFFFFFFFF" yading@11: yading@11: #define Q1024 \ yading@11: "7FFFFFFFFFFFFFFFE487ED5110B4611A62633145C06E0E68" \ yading@11: "948127044533E63A0105DF531D89CD9128A5043CC71A026E" \ yading@11: "F7CA8CD9E69D218D98158536F92F8A1BA7F09AB6B6A8E122" \ yading@11: "F242DABB312F3F637A262174D31BF6B585FFAE5B7A035BF6" \ yading@11: "F71C35FDAD44CFD2D74F9208BE258FF324943328F67329C0" \ yading@11: "FFFFFFFFFFFFFFFF" yading@11: yading@11: #if CONFIG_NETTLE || CONFIG_GCRYPT yading@11: #if CONFIG_NETTLE yading@11: #define bn_new(bn) \ yading@11: do { \ yading@11: bn = av_malloc(sizeof(*bn)); \ yading@11: if (bn) \ yading@11: mpz_init2(bn, 1); \ yading@11: } while (0) yading@11: #define bn_free(bn) \ yading@11: do { \ yading@11: mpz_clear(bn); \ yading@11: av_free(bn); \ yading@11: } while (0) yading@11: #define bn_set_word(bn, w) mpz_set_ui(bn, w) yading@11: #define bn_cmp(a, b) mpz_cmp(a, b) yading@11: #define bn_copy(to, from) mpz_set(to, from) yading@11: #define bn_sub_word(bn, w) mpz_sub_ui(bn, bn, w) yading@11: #define bn_cmp_1(bn) mpz_cmp_ui(bn, 1) yading@11: #define bn_num_bytes(bn) (mpz_sizeinbase(bn, 2) + 7) / 8 yading@11: #define bn_bn2bin(bn, buf, len) nettle_mpz_get_str_256(len, buf, bn) yading@11: #define bn_bin2bn(bn, buf, len) \ yading@11: do { \ yading@11: bn_new(bn); \ yading@11: if (bn) \ yading@11: nettle_mpz_set_str_256_u(bn, len, buf); \ yading@11: } while (0) yading@11: #define bn_hex2bn(bn, buf, ret) \ yading@11: do { \ yading@11: bn_new(bn); \ yading@11: if (bn) \ yading@11: ret = (mpz_set_str(bn, buf, 16) == 0); \ yading@11: } while (0) yading@11: #define bn_modexp(bn, y, q, p) mpz_powm(bn, y, q, p) yading@11: #define bn_random(bn, num_bytes) \ yading@11: do { \ yading@11: gmp_randstate_t rs; \ yading@11: gmp_randinit_mt(rs); \ yading@11: gmp_randseed_ui(rs, av_get_random_seed()); \ yading@11: mpz_urandomb(bn, rs, num_bytes); \ yading@11: gmp_randclear(rs); \ yading@11: } while (0) yading@11: #elif CONFIG_GCRYPT yading@11: #define bn_new(bn) bn = gcry_mpi_new(1) yading@11: #define bn_free(bn) gcry_mpi_release(bn) yading@11: #define bn_set_word(bn, w) gcry_mpi_set_ui(bn, w) yading@11: #define bn_cmp(a, b) gcry_mpi_cmp(a, b) yading@11: #define bn_copy(to, from) gcry_mpi_set(to, from) yading@11: #define bn_sub_word(bn, w) gcry_mpi_sub_ui(bn, bn, w) yading@11: #define bn_cmp_1(bn) gcry_mpi_cmp_ui(bn, 1) yading@11: #define bn_num_bytes(bn) (gcry_mpi_get_nbits(bn) + 7) / 8 yading@11: #define bn_bn2bin(bn, buf, len) gcry_mpi_print(GCRYMPI_FMT_USG, buf, len, NULL, bn) yading@11: #define bn_bin2bn(bn, buf, len) gcry_mpi_scan(&bn, GCRYMPI_FMT_USG, buf, len, NULL) yading@11: #define bn_hex2bn(bn, buf, ret) ret = (gcry_mpi_scan(&bn, GCRYMPI_FMT_HEX, buf, 0, 0) == 0) yading@11: #define bn_modexp(bn, y, q, p) gcry_mpi_powm(bn, y, q, p) yading@11: #define bn_random(bn, num_bytes) gcry_mpi_randomize(bn, num_bytes, GCRY_WEAK_RANDOM) yading@11: #endif yading@11: yading@11: #define MAX_BYTES 18000 yading@11: yading@11: #define dh_new() av_malloc(sizeof(FF_DH)) yading@11: yading@11: static FFBigNum dh_generate_key(FF_DH *dh) yading@11: { yading@11: int num_bytes; yading@11: yading@11: num_bytes = bn_num_bytes(dh->p) - 1; yading@11: if (num_bytes <= 0 || num_bytes > MAX_BYTES) yading@11: return NULL; yading@11: yading@11: bn_new(dh->priv_key); yading@11: if (!dh->priv_key) yading@11: return NULL; yading@11: bn_random(dh->priv_key, num_bytes); yading@11: yading@11: bn_new(dh->pub_key); yading@11: if (!dh->pub_key) { yading@11: bn_free(dh->priv_key); yading@11: return NULL; yading@11: } yading@11: yading@11: bn_modexp(dh->pub_key, dh->g, dh->priv_key, dh->p); yading@11: yading@11: return dh->pub_key; yading@11: } yading@11: yading@11: static int dh_compute_key(FF_DH *dh, FFBigNum pub_key_bn, yading@11: uint32_t pub_key_len, uint8_t *secret_key) yading@11: { yading@11: FFBigNum k; yading@11: int num_bytes; yading@11: yading@11: num_bytes = bn_num_bytes(dh->p); yading@11: if (num_bytes <= 0 || num_bytes > MAX_BYTES) yading@11: return -1; yading@11: yading@11: bn_new(k); yading@11: if (!k) yading@11: return -1; yading@11: yading@11: bn_modexp(k, pub_key_bn, dh->priv_key, dh->p); yading@11: bn_bn2bin(k, secret_key, pub_key_len); yading@11: bn_free(k); yading@11: yading@11: /* return the length of the shared secret key like DH_compute_key */ yading@11: return pub_key_len; yading@11: } yading@11: yading@11: void ff_dh_free(FF_DH *dh) yading@11: { yading@11: bn_free(dh->p); yading@11: bn_free(dh->g); yading@11: bn_free(dh->pub_key); yading@11: bn_free(dh->priv_key); yading@11: av_free(dh); yading@11: } yading@11: #elif CONFIG_OPENSSL yading@11: #define bn_new(bn) bn = BN_new() yading@11: #define bn_free(bn) BN_free(bn) yading@11: #define bn_set_word(bn, w) BN_set_word(bn, w) yading@11: #define bn_cmp(a, b) BN_cmp(a, b) yading@11: #define bn_copy(to, from) BN_copy(to, from) yading@11: #define bn_sub_word(bn, w) BN_sub_word(bn, w) yading@11: #define bn_cmp_1(bn) BN_cmp(bn, BN_value_one()) yading@11: #define bn_num_bytes(bn) BN_num_bytes(bn) yading@11: #define bn_bn2bin(bn, buf, len) BN_bn2bin(bn, buf) yading@11: #define bn_bin2bn(bn, buf, len) bn = BN_bin2bn(buf, len, 0) yading@11: #define bn_hex2bn(bn, buf, ret) ret = BN_hex2bn(&bn, buf) yading@11: #define bn_modexp(bn, y, q, p) \ yading@11: do { \ yading@11: BN_CTX *ctx = BN_CTX_new(); \ yading@11: if (!ctx) \ yading@11: return AVERROR(ENOMEM); \ yading@11: if (!BN_mod_exp(bn, y, q, p, ctx)) { \ yading@11: BN_CTX_free(ctx); \ yading@11: return AVERROR(EINVAL); \ yading@11: } \ yading@11: BN_CTX_free(ctx); \ yading@11: } while (0) yading@11: yading@11: #define dh_new() DH_new() yading@11: #define dh_generate_key(dh) DH_generate_key(dh) yading@11: #define dh_compute_key(dh, pub, len, secret) DH_compute_key(secret, pub, dh) yading@11: yading@11: void ff_dh_free(FF_DH *dh) yading@11: { yading@11: DH_free(dh); yading@11: } yading@11: #endif yading@11: yading@11: static int dh_is_valid_public_key(FFBigNum y, FFBigNum p, FFBigNum q) yading@11: { yading@11: FFBigNum bn = NULL; yading@11: int ret = AVERROR(EINVAL); yading@11: yading@11: bn_new(bn); yading@11: if (!bn) yading@11: return AVERROR(ENOMEM); yading@11: yading@11: /* y must lie in [2, p - 1] */ yading@11: bn_set_word(bn, 1); yading@11: if (!bn_cmp(y, bn)) yading@11: goto fail; yading@11: yading@11: /* bn = p - 2 */ yading@11: bn_copy(bn, p); yading@11: bn_sub_word(bn, 1); yading@11: if (!bn_cmp(y, bn)) yading@11: goto fail; yading@11: yading@11: /* Verify with Sophie-Germain prime yading@11: * yading@11: * This is a nice test to make sure the public key position is calculated yading@11: * correctly. This test will fail in about 50% of the cases if applied to yading@11: * random data. yading@11: */ yading@11: /* y must fulfill y^q mod p = 1 */ yading@11: bn_modexp(bn, y, q, p); yading@11: yading@11: if (bn_cmp_1(bn)) yading@11: goto fail; yading@11: yading@11: ret = 0; yading@11: fail: yading@11: bn_free(bn); yading@11: yading@11: return ret; yading@11: } yading@11: yading@11: av_cold FF_DH *ff_dh_init(int key_len) yading@11: { yading@11: FF_DH *dh; yading@11: int ret; yading@11: yading@11: if (!(dh = dh_new())) yading@11: return NULL; yading@11: yading@11: bn_new(dh->g); yading@11: if (!dh->g) yading@11: goto fail; yading@11: yading@11: bn_hex2bn(dh->p, P1024, ret); yading@11: if (!ret) yading@11: goto fail; yading@11: yading@11: bn_set_word(dh->g, 2); yading@11: dh->length = key_len; yading@11: yading@11: return dh; yading@11: yading@11: fail: yading@11: ff_dh_free(dh); yading@11: yading@11: return NULL; yading@11: } yading@11: yading@11: int ff_dh_generate_public_key(FF_DH *dh) yading@11: { yading@11: int ret = 0; yading@11: yading@11: while (!ret) { yading@11: FFBigNum q1 = NULL; yading@11: yading@11: if (!dh_generate_key(dh)) yading@11: return AVERROR(EINVAL); yading@11: yading@11: bn_hex2bn(q1, Q1024, ret); yading@11: if (!ret) yading@11: return AVERROR(ENOMEM); yading@11: yading@11: ret = dh_is_valid_public_key(dh->pub_key, dh->p, q1); yading@11: bn_free(q1); yading@11: yading@11: if (!ret) { yading@11: /* the public key is valid */ yading@11: break; yading@11: } yading@11: } yading@11: yading@11: return ret; yading@11: } yading@11: yading@11: int ff_dh_write_public_key(FF_DH *dh, uint8_t *pub_key, int pub_key_len) yading@11: { yading@11: int len; yading@11: yading@11: /* compute the length of the public key */ yading@11: len = bn_num_bytes(dh->pub_key); yading@11: if (len <= 0 || len > pub_key_len) yading@11: return AVERROR(EINVAL); yading@11: yading@11: /* convert the public key value into big-endian form */ yading@11: memset(pub_key, 0, pub_key_len); yading@11: bn_bn2bin(dh->pub_key, pub_key + pub_key_len - len, len); yading@11: yading@11: return 0; yading@11: } yading@11: yading@11: int ff_dh_compute_shared_secret_key(FF_DH *dh, const uint8_t *pub_key, yading@11: int pub_key_len, uint8_t *secret_key) yading@11: { yading@11: FFBigNum q1 = NULL, pub_key_bn = NULL; yading@11: int ret; yading@11: yading@11: /* convert the big-endian form of the public key into a bignum */ yading@11: bn_bin2bn(pub_key_bn, pub_key, pub_key_len); yading@11: if (!pub_key_bn) yading@11: return AVERROR(ENOMEM); yading@11: yading@11: /* convert the string containing a hexadecimal number into a bignum */ yading@11: bn_hex2bn(q1, Q1024, ret); yading@11: if (!ret) { yading@11: ret = AVERROR(ENOMEM); yading@11: goto fail; yading@11: } yading@11: yading@11: /* when the public key is valid we have to compute the shared secret key */ yading@11: if ((ret = dh_is_valid_public_key(pub_key_bn, dh->p, q1)) < 0) { yading@11: goto fail; yading@11: } else if ((ret = dh_compute_key(dh, pub_key_bn, pub_key_len, yading@11: secret_key)) < 0) { yading@11: ret = AVERROR(EINVAL); yading@11: goto fail; yading@11: } yading@11: yading@11: fail: yading@11: bn_free(pub_key_bn); yading@11: bn_free(q1); yading@11: yading@11: return ret; yading@11: } yading@11: