android / platform / external / openssl.git / f42d491ab90c82302b0054c62014c1ee9b638aff / . / crypto / dh / dh_gen.c

/* crypto/dh/dh_gen.c */ | |

/* 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.] | |

*/ | |

/* NB: These functions have been upgraded - the previous prototypes are in | |

* dh_depr.c as wrappers to these ones. | |

* - Geoff | |

*/ | |

#include <stdio.h> | |

#include "cryptlib.h" | |

#include <openssl/bn.h> | |

#include <openssl/dh.h> | |

#ifdef OPENSSL_FIPS | |

#include <openssl/fips.h> | |

#endif | |

static int dh_builtin_genparams(DH *ret, int prime_len, int generator, BN_GENCB *cb); | |

int DH_generate_parameters_ex(DH *ret, int prime_len, int generator, BN_GENCB *cb) | |

{ | |

#ifdef OPENSSL_FIPS | |

if (FIPS_mode() && !(ret->meth->flags & DH_FLAG_FIPS_METHOD) | |

&& !(ret->flags & DH_FLAG_NON_FIPS_ALLOW)) | |

{ | |

DHerr(DH_F_DH_GENERATE_PARAMETERS_EX, DH_R_NON_FIPS_METHOD); | |

return 0; | |

} | |

#endif | |

if(ret->meth->generate_params) | |

return ret->meth->generate_params(ret, prime_len, generator, cb); | |

#ifdef OPENSSL_FIPS | |

if (FIPS_mode()) | |

return FIPS_dh_generate_parameters_ex(ret, prime_len, | |

generator, cb); | |

#endif | |

return dh_builtin_genparams(ret, prime_len, generator, cb); | |

} | |

/* We generate DH parameters as follows | |

* find a prime q which is prime_len/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. | |

*/ | |

static int dh_builtin_genparams(DH *ret, int prime_len, int generator, BN_GENCB *cb) | |

{ | |

BIGNUM *t1,*t2; | |

int g,ok= -1; | |

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) | |

{ | |

DHerr(DH_F_DH_BUILTIN_GENPARAMS, 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; | |

} | |

#if 0 /* does not work for safe primes */ | |

else if (generator == DH_GENERATOR_3) | |

{ | |

if (!BN_set_word(t1,12)) goto err; | |

if (!BN_set_word(t2,5)) goto err; | |

g=3; | |

} | |

#endif | |

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_len,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 == -1) | |

{ | |

DHerr(DH_F_DH_BUILTIN_GENPARAMS,ERR_R_BN_LIB); | |

ok=0; | |

} | |

if (ctx != NULL) | |

{ | |

BN_CTX_end(ctx); | |

BN_CTX_free(ctx); | |

} | |

return ok; | |

} |