| /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com) |
| * All rights reserved. |
| * |
| * This package is an SSL implementation written |
| * by Eric Young (eay@cryptsoft.com). |
| * The implementation was written so as to conform with Netscapes SSL. |
| * |
| * This library is free for commercial and non-commercial use as long as |
| * the following conditions are aheared to. The following conditions |
| * apply to all code found in this distribution, be it the RC4, RSA, |
| * lhash, DES, etc., code; not just the SSL code. The SSL documentation |
| * included with this distribution is covered by the same copyright terms |
| * except that the holder is Tim Hudson (tjh@cryptsoft.com). |
| * |
| * Copyright remains Eric Young's, and as such any Copyright notices in |
| * the code are not to be removed. |
| * If this package is used in a product, Eric Young should be given attribution |
| * as the author of the parts of the library used. |
| * This can be in the form of a textual message at program startup or |
| * in documentation (online or textual) provided with the package. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * 1. Redistributions of source code must retain the copyright |
| * notice, this list of conditions and the following disclaimer. |
| * 2. Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * 3. All advertising materials mentioning features or use of this software |
| * must display the following acknowledgement: |
| * "This product includes cryptographic software written by |
| * Eric Young (eay@cryptsoft.com)" |
| * The word 'cryptographic' can be left out if the rouines from the library |
| * being used are not cryptographic related :-). |
| * 4. If you include any Windows specific code (or a derivative thereof) from |
| * the apps directory (application code) you must include an acknowledgement: |
| * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)" |
| * |
| * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND |
| * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE |
| * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
| * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
| * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
| * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
| * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
| * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| * SUCH DAMAGE. |
| * |
| * The licence and distribution terms for any publically available version or |
| * derivative of this code cannot be changed. i.e. this code cannot simply be |
| * copied and put under another distribution licence |
| * [including the GNU Public Licence.] */ |
| |
| #include <openssl/dh.h> |
| |
| #include <openssl/bn.h> |
| #include <openssl/err.h> |
| |
| #include "internal.h" |
| |
| #define OPENSSL_DH_MAX_MODULUS_BITS 10000 |
| |
| static int generate_parameters(DH *ret, int prime_bits, int generator, BN_GENCB *cb) { |
| /* We generate DH parameters as follows |
| * find a prime q which is prime_bits/2 bits long. |
| * p=(2*q)+1 or (p-1)/2 = q |
| * For this case, g is a generator if |
| * g^((p-1)/q) mod p != 1 for values of q which are the factors of p-1. |
| * Since the factors of p-1 are q and 2, we just need to check |
| * g^2 mod p != 1 and g^q mod p != 1. |
| * |
| * Having said all that, |
| * there is another special case method for the generators 2, 3 and 5. |
| * for 2, p mod 24 == 11 |
| * for 3, p mod 12 == 5 <<<<< does not work for safe primes. |
| * for 5, p mod 10 == 3 or 7 |
| * |
| * Thanks to Phil Karn <karn@qualcomm.com> for the pointers about the |
| * special generators and for answering some of my questions. |
| * |
| * I've implemented the second simple method :-). |
| * Since DH should be using a safe prime (both p and q are prime), |
| * this generator function can take a very very long time to run. |
| */ |
| |
| /* Actually there is no reason to insist that 'generator' be a generator. |
| * It's just as OK (and in some sense better) to use a generator of the |
| * order-q subgroup. |
| */ |
| |
| BIGNUM *t1, *t2; |
| int g, ok = 0; |
| BN_CTX *ctx = NULL; |
| |
| ctx = BN_CTX_new(); |
| if (ctx == NULL) { |
| goto err; |
| } |
| BN_CTX_start(ctx); |
| t1 = BN_CTX_get(ctx); |
| t2 = BN_CTX_get(ctx); |
| if (t1 == NULL || t2 == NULL) { |
| goto err; |
| } |
| |
| /* Make sure 'ret' has the necessary elements */ |
| if (!ret->p && ((ret->p = BN_new()) == NULL)) { |
| goto err; |
| } |
| if (!ret->g && ((ret->g = BN_new()) == NULL)) { |
| goto err; |
| } |
| |
| if (generator <= 1) { |
| OPENSSL_PUT_ERROR(DH, generate_parameters, DH_R_BAD_GENERATOR); |
| goto err; |
| } |
| if (generator == DH_GENERATOR_2) { |
| if (!BN_set_word(t1, 24)) { |
| goto err; |
| } |
| if (!BN_set_word(t2, 11)) { |
| goto err; |
| } |
| g = 2; |
| } else if (generator == DH_GENERATOR_5) { |
| if (!BN_set_word(t1, 10)) { |
| goto err; |
| } |
| if (!BN_set_word(t2, 3)) { |
| goto err; |
| } |
| /* BN_set_word(t3,7); just have to miss |
| * out on these ones :-( */ |
| g = 5; |
| } else { |
| /* in the general case, don't worry if 'generator' is a |
| * generator or not: since we are using safe primes, |
| * it will generate either an order-q or an order-2q group, |
| * which both is OK */ |
| if (!BN_set_word(t1, 2)) { |
| goto err; |
| } |
| if (!BN_set_word(t2, 1)) { |
| goto err; |
| } |
| g = generator; |
| } |
| |
| if (!BN_generate_prime_ex(ret->p, prime_bits, 1, t1, t2, cb)) { |
| goto err; |
| } |
| if (!BN_GENCB_call(cb, 3, 0)) { |
| goto err; |
| } |
| if (!BN_set_word(ret->g, g)) { |
| goto err; |
| } |
| ok = 1; |
| |
| err: |
| if (!ok) { |
| OPENSSL_PUT_ERROR(DH, generate_parameters, ERR_R_BN_LIB); |
| } |
| |
| if (ctx != NULL) { |
| BN_CTX_end(ctx); |
| BN_CTX_free(ctx); |
| } |
| return ok; |
| } |
| |
| static int generate_key(DH *dh) { |
| int ok = 0; |
| int generate_new_key = 0; |
| unsigned l; |
| BN_CTX *ctx; |
| BN_MONT_CTX *mont = NULL; |
| BIGNUM *pub_key = NULL, *priv_key = NULL; |
| BIGNUM local_priv; |
| |
| ctx = BN_CTX_new(); |
| if (ctx == NULL) { |
| goto err; |
| } |
| |
| if (dh->priv_key == NULL) { |
| priv_key = BN_new(); |
| if (priv_key == NULL) { |
| goto err; |
| } |
| generate_new_key = 1; |
| } else { |
| priv_key = dh->priv_key; |
| } |
| |
| if (dh->pub_key == NULL) { |
| pub_key = BN_new(); |
| if (pub_key == NULL) { |
| goto err; |
| } |
| } else { |
| pub_key = dh->pub_key; |
| } |
| |
| mont = |
| BN_MONT_CTX_set_locked(&dh->method_mont_p, CRYPTO_LOCK_DH, dh->p, ctx); |
| if (!mont) { |
| goto err; |
| } |
| |
| if (generate_new_key) { |
| if (dh->q) { |
| do { |
| if (!BN_rand_range(priv_key, dh->q)) { |
| goto err; |
| } |
| } while (BN_is_zero(priv_key) || BN_is_one(priv_key)); |
| } else { |
| /* secret exponent length */ |
| DH_check_standard_parameters(dh); |
| l = dh->priv_length ? dh->priv_length : BN_num_bits(dh->p) - 1; |
| if (!BN_rand(priv_key, l, 0, 0)) { |
| goto err; |
| } |
| } |
| } |
| |
| BN_with_flags(&local_priv, priv_key, BN_FLG_CONSTTIME); |
| if (!BN_mod_exp_mont(pub_key, dh->g, &local_priv, dh->p, ctx, mont)) { |
| goto err; |
| } |
| |
| dh->pub_key = pub_key; |
| dh->priv_key = priv_key; |
| ok = 1; |
| |
| err: |
| if (ok != 1) { |
| OPENSSL_PUT_ERROR(DH, generate_key, ERR_R_BN_LIB); |
| } |
| |
| if (pub_key != NULL && dh->pub_key == NULL) { |
| BN_free(pub_key); |
| } |
| if (priv_key != NULL && dh->priv_key == NULL) { |
| BN_free(priv_key); |
| } |
| BN_CTX_free(ctx); |
| return ok; |
| } |
| |
| static int compute_key(DH *dh, unsigned char *out, const BIGNUM *pub_key) { |
| BN_CTX *ctx = NULL; |
| BN_MONT_CTX *mont = NULL; |
| BIGNUM *shared_key; |
| int ret = -1; |
| int check_result; |
| BIGNUM local_priv; |
| |
| if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) { |
| OPENSSL_PUT_ERROR(DH, compute_key, DH_R_MODULUS_TOO_LARGE); |
| goto err; |
| } |
| |
| ctx = BN_CTX_new(); |
| if (ctx == NULL) { |
| goto err; |
| } |
| BN_CTX_start(ctx); |
| shared_key = BN_CTX_get(ctx); |
| if (shared_key == NULL) { |
| goto err; |
| } |
| |
| if (dh->priv_key == NULL) { |
| OPENSSL_PUT_ERROR(DH, compute_key, DH_R_NO_PRIVATE_VALUE); |
| goto err; |
| } |
| |
| mont = |
| BN_MONT_CTX_set_locked(&dh->method_mont_p, CRYPTO_LOCK_DH, dh->p, ctx); |
| if (!mont) { |
| goto err; |
| } |
| |
| if (!DH_check_pub_key(dh, pub_key, &check_result) || check_result) { |
| OPENSSL_PUT_ERROR(DH, compute_key, DH_R_INVALID_PUBKEY); |
| goto err; |
| } |
| |
| BN_with_flags(&local_priv, dh->priv_key, BN_FLG_CONSTTIME); |
| if (!BN_mod_exp_mont(shared_key, pub_key, &local_priv, dh->p, ctx, |
| mont)) { |
| OPENSSL_PUT_ERROR(DH, compute_key, ERR_R_BN_LIB); |
| goto err; |
| } |
| |
| ret = BN_bn2bin(shared_key, out); |
| |
| err: |
| if (ctx != NULL) { |
| BN_CTX_end(ctx); |
| BN_CTX_free(ctx); |
| } |
| |
| return ret; |
| } |
| |
| const struct dh_method DH_default_method = { |
| { |
| 0 /* references */, |
| 1 /* is_static */, |
| }, |
| NULL /* app_data */, |
| NULL /* init */, |
| NULL /* finish */, |
| generate_parameters, |
| generate_key, |
| compute_key, |
| }; |