bn_lib.c

一个用于点对点传输加密的工具包源码

/* crypto/bn/bn_lib.c */
/* Copyright (C) 1995-1998 Eric Young ([e-mail])
 * All rights reserved.
 *
 * This package is an SSL implementation written
 * by Eric Young ([e-mail]).
 * 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 ([e-mail]).
 * 
 * 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 ([e-mail])"
 *    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 ([e-mail])"
 * 
 * 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.]
 */

#ifndef BN_DEBUG
# undef NDEBUG /* avoid conflicting definitions */
# define NDEBUG
#endif

#include <assert.h>
#include <stdio.h>
#include "cryptlib.h"
#include "bn_lcl.h"

const char *BN_version="Big Number" OPENSSL_VERSION_PTEXT;

/* For a 32 bit machine
 * 2 -   4 ==  128
 * 3 -   8 ==  256
 * 4 -  16 ==  512
 * 5 -  32 == 1024
 * 6 -  64 == 2048
 * 7 - 128 == 4096
 * 8 - 256 == 8192
 */
static int bn_limit_bits=0;
static int bn_limit_num=8;        /* (1<<bn_limit_bits) */
static int bn_limit_bits_low=0;
static int bn_limit_num_low=8;    /* (1<<bn_limit_bits_low) */
static int bn_limit_bits_high=0;
static int bn_limit_num_high=8;   /* (1<<bn_limit_bits_high) */
static int bn_limit_bits_mont=0;
static int bn_limit_num_mont=8;   /* (1<<bn_limit_bits_mont) */

void BN_set_params(int mult, int high, int low, int mont)
	{
	if (mult >= 0)
		{
		if (mult > (sizeof(int)*8)-1)
			mult=sizeof(int)*8-1;
		bn_limit_bits=mult;
		bn_limit_num=1<<mult;
		}
	if (high >= 0)
		{
		if (high > (sizeof(int)*8)-1)
			high=sizeof(int)*8-1;
		bn_limit_bits_high=high;
		bn_limit_num_high=1<<high;
		}
	if (low >= 0)
		{
		if (low > (sizeof(int)*8)-1)
			low=sizeof(int)*8-1;
		bn_limit_bits_low=low;
		bn_limit_num_low=1<<low;
		}
	if (mont >= 0)
		{
		if (mont > (sizeof(int)*8)-1)
			mont=sizeof(int)*8-1;
		bn_limit_bits_mont=mont;
		bn_limit_num_mont=1<<mont;
		}
	}

int BN_get_params(int which)
	{
	if      (which == 0) return(bn_limit_bits);
	else if (which == 1) return(bn_limit_bits_high);
	else if (which == 2) return(bn_limit_bits_low);
	else if (which == 3) return(bn_limit_bits_mont);
	else return(0);
	}

BIGNUM *BN_value_one(void)
	{
	static BN_ULONG data_one=1L;
	static BIGNUM const_one={&data_one,1,1,0};

	return(&const_one);
	}

char *BN_options(void)
	{
	static int init=0;
	static char data[16];

	if (!init)
		{
		init++;
#ifdef BN_LLONG
		sprintf(data,"bn(%d,%d)",(int)sizeof(BN_ULLONG)*8,
			(int)sizeof(BN_ULONG)*8);
#else
		sprintf(data,"bn(%d,%d)",(int)sizeof(BN_ULONG)*8,
			(int)sizeof(BN_ULONG)*8);
#endif
		}
	return(data);
	}

int BN_num_bits_word(BN_ULONG l)
	{
	static const char bits[256]={
		0,1,2,2,3,3,3,3,4,4,4,4,4,4,4,4,
		5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
		6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
		6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
		7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
		7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
		7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
		7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
		8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,
		8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,
		8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,
		8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,
		8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,
		8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,
		8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,
		8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,
		};

#if defined(SIXTY_FOUR_BIT_LONG)
	if (l & 0xffffffff00000000L)
		{
		if (l & 0xffff000000000000L)
			{
			if (l & 0xff00000000000000L)
				{
				return(bits[(int)(l>>56)]+56);
				}
			else	return(bits[(int)(l>>48)]+48);
			}
		else
			{
			if (l & 0x0000ff0000000000L)
				{
				return(bits[(int)(l>>40)]+40);
				}
			else	return(bits[(int)(l>>32)]+32);
			}
		}
	else
#else
#ifdef SIXTY_FOUR_BIT
	if (l & 0xffffffff00000000LL)
		{
		if (l & 0xffff000000000000LL)
			{
			if (l & 0xff00000000000000LL)
				{
				return(bits[(int)(l>>56)]+56);
				}
			else	return(bits[(int)(l>>48)]+48);
			}
		else
			{
			if (l & 0x0000ff0000000000LL)
				{
				return(bits[(int)(l>>40)]+40);
				}
			else	return(bits[(int)(l>>32)]+32);
			}
		}
	else
#endif
#endif
		{
#if defined(THIRTY_TWO_BIT) || defined(SIXTY_FOUR_BIT) || defined(SIXTY_FOUR_BIT_LONG)
		if (l & 0xffff0000L)
			{
			if (l & 0xff000000L)
				return(bits[(int)(l>>24L)]+24);
			else	return(bits[(int)(l>>16L)]+16);
			}
		else
#endif
			{
#if defined(SIXTEEN_BIT) || defined(THIRTY_TWO_BIT) || defined(SIXTY_FOUR_BIT) || defined(SIXTY_FOUR_BIT_LONG)
			if (l & 0xff00L)
				return(bits[(int)(l>>8)]+8);
			else	
#endif
				return(bits[(int)(l   )]  );
			}
		}
	}

int BN_num_bits(const BIGNUM *a)
	{
	BN_ULONG l;
	int i;

	bn_check_top(a);

	if (a->top == 0) return(0);
	l=a->d[a->top-1];
	assert(l != 0);
	i=(a->top-1)*BN_BITS2;
	return(i+BN_num_bits_word(l));
	}

void BN_clear_free(BIGNUM *a)
	{
	int i;

	if (a == NULL) return;
	if (a->d != NULL)
		{
		memset(a->d,0,a->dmax*sizeof(a->d[0]));
		if (!(BN_get_flags(a,BN_FLG_STATIC_DATA)))
			OPENSSL_free(a->d);
		}
	i=BN_get_flags(a,BN_FLG_MALLOCED);
	memset(a,0,sizeof(BIGNUM));
	if (i)
		OPENSSL_free(a);
	}

void BN_free(BIGNUM *a)
	{
	if (a == NULL) return;
	if ((a->d != NULL) && !(BN_get_flags(a,BN_FLG_STATIC_DATA)))
		OPENSSL_free(a->d);
	a->flags|=BN_FLG_FREE; /* REMOVE? */
	if (a->flags & BN_FLG_MALLOCED)
		OPENSSL_free(a);
	}

void BN_init(BIGNUM *a)
	{
	memset(a,0,sizeof(BIGNUM));
	}

BIGNUM *BN_new(void)
	{
	BIGNUM *ret;

	if ((ret=(BIGNUM *)OPENSSL_malloc(sizeof(BIGNUM))) == NULL)
		{
		BNerr(BN_F_BN_NEW,ERR_R_MALLOC_FAILURE);
		return(NULL);
		}
	ret->flags=BN_FLG_MALLOCED;
	ret->top=0;
	ret->neg=0;
	ret->dmax=0;
	ret->d=NULL;
	return(ret);
	}

/* This is an internal function that should not be used in applications.
 * It ensures that 'b' has enough room for a 'words' word number number.
 * It is mostly used by the various BIGNUM routines. If there is an error,
 * NULL is returned. If not, 'b' is returned. */

BIGNUM *bn_expand2(BIGNUM *b, int words)
	{
	BN_ULONG *A,*a;
	const BN_ULONG *B;
	int i;

	bn_check_top(b);

	if (words > b->dmax)
		{
		bn_check_top(b);	
		if (BN_get_flags(b,BN_FLG_STATIC_DATA))
			{
			BNerr(BN_F_BN_EXPAND2,BN_R_EXPAND_ON_STATIC_BIGNUM_DATA);
			return(NULL);
			}
		a=A=(BN_ULONG *)OPENSSL_malloc(sizeof(BN_ULONG)*(words+1));
		if (A == NULL)
			{
			BNerr(BN_F_BN_EXPAND2,ERR_R_MALLOC_FAILURE);
			return(NULL);
			}
#if 1
		B=b->d;
		/* Check if the previous number needs to be copied */
		if (B != NULL)
			{
#if 0
			/* This lot is an unrolled loop to copy b->top 
			 * BN_ULONGs from B to A
			 */
/*
 * I have nothing against unrolling but it's usually done for
 * several reasons, namely:
 * - minimize percentage of decision making code, i.e. branches;
 * - avoid cache trashing;
 * - make it possible to schedule loads earlier;
 * Now let's examine the code below. The cornerstone of C is
 * "programmer is always right" and that's what we love it for:-)
 * For this very reason C compilers have to be paranoid when it
 * comes to data aliasing and assume the worst. Yeah, but what
 * does it mean in real life? This means that loop body below will
 * be compiled to sequence of loads immediately followed by stores
 * as compiler assumes the worst, something in A==B+1 style. As a
 * result CPU pipeline is going to starve for incoming data. Secondly
 * if A and B happen to share same cache line such code is going to
 * cause severe cache trashing. Both factors have severe impact on
 * performance of modern CPUs and this is the reason why this
 * particular piece of code is #ifdefed away and replaced by more
 * "friendly" version found in #else section below. This comment
 * also applies to BN_copy function.
 *
 *					<[e-mail]>
 */
			for (i=b->top&(~7); i>0; i-=8)
				{
				A[0]=B[0]; A[1]=B[1]; A[2]=B[2]; A[3]=B[3];
				A[4]=B[4]; A[5]=B[5]; A[6]=B[6]; A[7]=B[7];
				A+=8;
				B+=8;
				}
			switch (b->top&7)
				{
			case 7:
				A[6]=B[6];
			case 6:
				A[5]=B[5];