0e4aa0d2d2
override key-generation implementations by placing handlers in the methods for DSA and DH. Also, parameter generation for DSA and DH is possible by another new handler for each method.
175 lines
6.3 KiB
C
175 lines
6.3 KiB
C
/* crypto/dh/dh_gen.c */
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/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
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* All rights reserved.
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*
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* This package is an SSL implementation written
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* by Eric Young (eay@cryptsoft.com).
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* The implementation was written so as to conform with Netscapes SSL.
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*
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* This library is free for commercial and non-commercial use as long as
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* the following conditions are aheared to. The following conditions
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* apply to all code found in this distribution, be it the RC4, RSA,
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* lhash, DES, etc., code; not just the SSL code. The SSL documentation
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* included with this distribution is covered by the same copyright terms
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* except that the holder is Tim Hudson (tjh@cryptsoft.com).
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*
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* Copyright remains Eric Young's, and as such any Copyright notices in
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* the code are not to be removed.
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* If this package is used in a product, Eric Young should be given attribution
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* as the author of the parts of the library used.
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* This can be in the form of a textual message at program startup or
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* in documentation (online or textual) provided with the package.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* "This product includes cryptographic software written by
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* Eric Young (eay@cryptsoft.com)"
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* The word 'cryptographic' can be left out if the rouines from the library
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* being used are not cryptographic related :-).
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* 4. If you include any Windows specific code (or a derivative thereof) from
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* the apps directory (application code) you must include an acknowledgement:
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* "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
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*
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* THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* The licence and distribution terms for any publically available version or
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* derivative of this code cannot be changed. i.e. this code cannot simply be
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* copied and put under another distribution licence
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* [including the GNU Public Licence.]
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*/
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/* NB: These functions have been upgraded - the previous prototypes are in
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* dh_depr.c as wrappers to these ones.
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* - Geoff
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*/
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#include <stdio.h>
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#include "cryptlib.h"
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#include <openssl/bn.h>
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#include <openssl/dh.h>
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static int dh_builtin_genparams(DH *ret, int prime_len, int generator, BN_GENCB *cb);
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int DH_generate_parameters_ex(DH *ret, int prime_len, int generator, BN_GENCB *cb)
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{
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if(ret->meth->generate_params)
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return ret->meth->generate_params(ret, prime_len, generator, cb);
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return dh_builtin_genparams(ret, prime_len, generator, cb);
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}
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/* We generate DH parameters as follows
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* find a prime q which is prime_len/2 bits long.
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* p=(2*q)+1 or (p-1)/2 = q
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* For this case, g is a generator if
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* g^((p-1)/q) mod p != 1 for values of q which are the factors of p-1.
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* Since the factors of p-1 are q and 2, we just need to check
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* g^2 mod p != 1 and g^q mod p != 1.
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*
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* Having said all that,
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* there is another special case method for the generators 2, 3 and 5.
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* for 2, p mod 24 == 11
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* for 3, p mod 12 == 5 <<<<< does not work for safe primes.
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* for 5, p mod 10 == 3 or 7
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*
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* Thanks to Phil Karn <karn@qualcomm.com> for the pointers about the
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* special generators and for answering some of my questions.
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*
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* I've implemented the second simple method :-).
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* Since DH should be using a safe prime (both p and q are prime),
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* this generator function can take a very very long time to run.
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*/
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/* Actually there is no reason to insist that 'generator' be a generator.
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* It's just as OK (and in some sense better) to use a generator of the
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* order-q subgroup.
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*/
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static int dh_builtin_genparams(DH *ret, int prime_len, int generator, BN_GENCB *cb)
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{
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BIGNUM *t1,*t2;
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int g,ok= -1;
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BN_CTX *ctx=NULL;
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ctx=BN_CTX_new();
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if (ctx == NULL) goto err;
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BN_CTX_start(ctx);
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t1 = BN_CTX_get(ctx);
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t2 = BN_CTX_get(ctx);
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if (t1 == NULL || t2 == NULL) goto err;
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/* Make sure 'ret' has the necessary elements */
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if(!ret->p && ((ret->p = BN_new()) == NULL)) goto err;
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if(!ret->g && ((ret->g = BN_new()) == NULL)) goto err;
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if (generator <= 1)
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{
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DHerr(DH_F_DH_GENERATE_PARAMETERS, DH_R_BAD_GENERATOR);
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goto err;
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}
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if (generator == DH_GENERATOR_2)
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{
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if (!BN_set_word(t1,24)) goto err;
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if (!BN_set_word(t2,11)) goto err;
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g=2;
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}
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#if 0 /* does not work for safe primes */
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else if (generator == DH_GENERATOR_3)
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{
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if (!BN_set_word(t1,12)) goto err;
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if (!BN_set_word(t2,5)) goto err;
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g=3;
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}
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#endif
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else if (generator == DH_GENERATOR_5)
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{
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if (!BN_set_word(t1,10)) goto err;
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if (!BN_set_word(t2,3)) goto err;
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/* BN_set_word(t3,7); just have to miss
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* out on these ones :-( */
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g=5;
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}
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else
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{
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/* in the general case, don't worry if 'generator' is a
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* generator or not: since we are using safe primes,
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* it will generate either an order-q or an order-2q group,
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* which both is OK */
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if (!BN_set_word(t1,2)) goto err;
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if (!BN_set_word(t2,1)) goto err;
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g=generator;
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}
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if(!BN_generate_prime_ex(ret->p,prime_len,1,t1,t2,cb)) goto err;
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if(!BN_GENCB_call(cb, 3, 0)) goto err;
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if (!BN_set_word(ret->g,g)) goto err;
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ok=1;
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err:
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if (ok == -1)
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{
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DHerr(DH_F_DH_GENERATE_PARAMETERS,ERR_R_BN_LIB);
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ok=0;
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}
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if (ctx != NULL)
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{
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BN_CTX_end(ctx);
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BN_CTX_free(ctx);
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}
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return ok;
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}
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