/* crypto/bn/bn_ctx.c */

 /* Written by Ulf Moeller for the OpenSSL project. */

 /* ====================================================================

  * Copyright (c) 1998-2004 The OpenSSL Project.  All rights reserved.

  *

  * 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 above 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 acknowledgment:

  *    "This product includes software developed by the OpenSSL Project

  *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"

  *

  * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to

  *    endorse or promote products derived from this software without

  *    prior written permission. For written permission, please contact

  *    openssl-core@openssl.org.

  *

  * 5. Products derived from this software may not be called "OpenSSL"

  *    nor may "OpenSSL" appear in their names without prior written

  *    permission of the OpenSSL Project.

  *

  * 6. Redistributions of any form whatsoever must retain the following

  *    acknowledgment:

  *    "This product includes software developed by the OpenSSL Project

  *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"

  *

  * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY

  * EXPRESSED 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 OpenSSL PROJECT OR

  * ITS 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.

  * ====================================================================

  *

  * This product includes cryptographic software written by Eric Young

  * (eay@cryptsoft.com).  This product includes software written by Tim

  * Hudson (tjh@cryptsoft.com).

  *

  */

 #if !defined(BN_CTX_DEBUG) && !defined(BN_DEBUG)

 #ifndef NDEBUG

 #define NDEBUG

 #endif

 #endif

 #include <stdio.h>

 #include <assert.h>

 #include "cryptlib.h"

 #include "bn_lcl.h"

 /* TODO list

  *

  * 1. Check a bunch of "(words+1)" type hacks in various bignum functions and

  * check they can be safely removed.

  *  - Check +1 and other ugliness in BN_from_montgomery()

  *

  * 2. Consider allowing a BN_new_ex() that, at least, lets you specify an

  * appropriate 'block' size that will be honoured by bn_expand_internal() to

  * prevent piddly little reallocations. OTOH, profiling bignum expansions in

  * BN_CTX doesn't show this to be a big issue.

  */

 /* How many bignums are in each "pool item"; */

 #define BN_CTX_POOL_SIZE	16

 /* The stack frame info is resizing, set a first-time expansion size; */

 #define BN_CTX_START_FRAMES	32

 /***********/

 /* BN_POOL */

 /***********/

 /* A bundle of bignums that can be linked with other bundles */

 typedef struct bignum_pool_item

 	{

 	/* The bignum values */

 	BIGNUM vals[BN_CTX_POOL_SIZE];

 	/* Linked-list admin */

 	struct bignum_pool_item *prev, *next;

 	} BN_POOL_ITEM;

 /* A linked-list of bignums grouped in bundles */

 typedef struct bignum_pool

 	{

 	/* Linked-list admin */

 	BN_POOL_ITEM *head, *current, *tail;

 	/* Stack depth and allocation size */

 	unsigned used, size;

 	} BN_POOL;

 static void		BN_POOL_init(BN_POOL *);

 static void		BN_POOL_finish(BN_POOL *);

 #ifndef OPENSSL_NO_DEPRECATED

 static void		BN_POOL_reset(BN_POOL *);

 #endif

 static BIGNUM *		BN_POOL_get(BN_POOL *);

 static void		BN_POOL_release(BN_POOL *, unsigned int);

 /************/

 /* BN_STACK */

 /************/

 /* A wrapper to manage the "stack frames" */

 typedef struct bignum_ctx_stack

 	{

 	/* Array of indexes into the bignum stack */

 	unsigned int *indexes;

 	/* Number of stack frames, and the size of the allocated array */

 	unsigned int depth, size;

 	} BN_STACK;

 static void		BN_STACK_init(BN_STACK *);

 static void		BN_STACK_finish(BN_STACK *);

 #ifndef OPENSSL_NO_DEPRECATED

 static void		BN_STACK_reset(BN_STACK *);

 #endif

 static int		BN_STACK_push(BN_STACK *, unsigned int);

 static unsigned int	BN_STACK_pop(BN_STACK *);

 /**********/

 /* BN_CTX */

 /**********/

 /* The opaque BN_CTX type */

 struct bignum_ctx

 	{

 	/* The bignum bundles */

 	BN_POOL pool;

 	/* The "stack frames", if you will */

 	BN_STACK stack;

 	/* The number of bignums currently assigned */

 	unsigned int used;

 	/* Depth of stack overflow */

 	int err_stack;

 	/* Block "gets" until an "end" (compatibility behaviour) */

 	int too_many;

 	};

 /* Enable this to find BN_CTX bugs */

 #ifdef BN_CTX_DEBUG

 static const char *ctxdbg_cur = NULL;

 static void ctxdbg(BN_CTX *ctx)

 	{

 	unsigned int bnidx = 0, fpidx = 0;

 	BN_POOL_ITEM *item = ctx->pool.head;

 	BN_STACK *stack = &ctx->stack;

 	fprintf(stderr,"(%08x): ", (unsigned int)ctx);

 	while(bnidx < ctx->used)

 		{

 		fprintf(stderr,"%02x ", item->vals[bnidx++ % BN_CTX_POOL_SIZE].dmax);

 		if(!(bnidx % BN_CTX_POOL_SIZE))

 			item = item->next;

 		}

 	fprintf(stderr,"\n");

 	bnidx = 0;

 	fprintf(stderr,"          : ");

 	while(fpidx < stack->depth)

 		{

 		while(bnidx++ < stack->indexes[fpidx])

 			fprintf(stderr,"   ");

 		fprintf(stderr,"^^ ");

 		bnidx++;

 		fpidx++;

 		}

 	fprintf(stderr,"\n");

 	}

 #define CTXDBG_ENTRY(str, ctx)	do { \

 				ctxdbg_cur = (str); \

 				fprintf(stderr,"Starting %s\n", ctxdbg_cur); \

 				ctxdbg(ctx); \

 				} while(0)

 #define CTXDBG_EXIT(ctx)	do { \

 				fprintf(stderr,"Ending %s\n", ctxdbg_cur); \

 				ctxdbg(ctx); \

 				} while(0)

 #define CTXDBG_RET(ctx,ret)

 #else

 #define CTXDBG_ENTRY(str, ctx)

 #define CTXDBG_EXIT(ctx)

 #define CTXDBG_RET(ctx,ret)

 #endif

 /* This function is an evil legacy and should not be used. This implementation

  * is WYSIWYG, though I've done my best. */

 #ifndef OPENSSL_NO_DEPRECATED

 EXPORT_C void BN_CTX_init(BN_CTX *ctx)

 	{

 	/* Assume the caller obtained the context via BN_CTX_new() and so is

 	 * trying to reset it for use. Nothing else makes sense, least of all

 	 * binary compatibility from a time when they could declare a static

 	 * variable. */

 	BN_POOL_reset(&ctx->pool);

 	BN_STACK_reset(&ctx->stack);

 	ctx->used = 0;

 	ctx->err_stack = 0;

 	ctx->too_many = 0;

 	}

 #endif

 EXPORT_C BN_CTX *BN_CTX_new(void)

 	{

 	BN_CTX *ret = OPENSSL_malloc(sizeof(BN_CTX));

 	if(!ret)

 		{

 		BNerr(BN_F_BN_CTX_NEW,ERR_R_MALLOC_FAILURE);

 		return NULL;

 		}

 	/* Initialise the structure */

 	BN_POOL_init(&ret->pool);

 	BN_STACK_init(&ret->stack);

 	ret->used = 0;

 	ret->err_stack = 0;

 	ret->too_many = 0;

 	return ret;

 	}

 EXPORT_C void BN_CTX_free(BN_CTX *ctx)

 	{

 	if (ctx == NULL)

 		return;

 #ifdef BN_CTX_DEBUG

 	{

 	BN_POOL_ITEM *pool = ctx->pool.head;

 	fprintf(stderr,"BN_CTX_free, stack-size=%d, pool-bignums=%d\n",

 		ctx->stack.size, ctx->pool.size);

 	fprintf(stderr,"dmaxs: ");

 	while(pool) {

 		unsigned loop = 0;

 		while(loop < BN_CTX_POOL_SIZE)

 			fprintf(stderr,"%02x ", pool->vals[loop++].dmax);

 		pool = pool->next;

 	}

 	fprintf(stderr,"\n");

 	}

 #endif

 	BN_STACK_finish(&ctx->stack);

 	BN_POOL_finish(&ctx->pool);

 	OPENSSL_free(ctx);

 	}

 EXPORT_C void BN_CTX_start(BN_CTX *ctx)

 	{

 	CTXDBG_ENTRY("BN_CTX_start", ctx);

 	/* If we're already overflowing ... */

 	if(ctx->err_stack || ctx->too_many)

 		ctx->err_stack++;

 	/* (Try to) get a new frame pointer */

 	else if(!BN_STACK_push(&ctx->stack, ctx->used))

 		{

 		BNerr(BN_F_BN_CTX_START,BN_R_TOO_MANY_TEMPORARY_VARIABLES);

 		ctx->err_stack++;

 		}

 	CTXDBG_EXIT(ctx);

 	}

 EXPORT_C void BN_CTX_end(BN_CTX *ctx)

 	{

 	CTXDBG_ENTRY("BN_CTX_end", ctx);

 	if(ctx->err_stack)

 		ctx->err_stack--;

 	else

 		{

 		unsigned int fp = BN_STACK_pop(&ctx->stack);

 		/* Does this stack frame have anything to release? */

 		if(fp < ctx->used)

 			BN_POOL_release(&ctx->pool, ctx->used - fp);

 		ctx->used = fp;

 		/* Unjam "too_many" in case "get" had failed */

 		ctx->too_many = 0;

 		}

 	CTXDBG_EXIT(ctx);

 	}

 EXPORT_C BIGNUM *BN_CTX_get(BN_CTX *ctx)

 	{

 	BIGNUM *ret;

 	CTXDBG_ENTRY("BN_CTX_get", ctx);

 	if(ctx->err_stack || ctx->too_many) return NULL;

 	if((ret = BN_POOL_get(&ctx->pool)) == NULL)

 		{

 		/* Setting too_many prevents repeated "get" attempts from

 		 * cluttering the error stack. */

 		ctx->too_many = 1;

 		BNerr(BN_F_BN_CTX_GET,BN_R_TOO_MANY_TEMPORARY_VARIABLES);

 		return NULL;

 		}

 	/* OK, make sure the returned bignum is "zero" */

 	BN_zero(ret);

 	ctx->used++;

 	CTXDBG_RET(ctx, ret);

 	return ret;

 	}

 /************/

 /* BN_STACK */

 /************/

 static void BN_STACK_init(BN_STACK *st)

 	{

 	st->indexes = NULL;

 	st->depth = st->size = 0;

 	}

 static void BN_STACK_finish(BN_STACK *st)

 	{

 	if(st->size) OPENSSL_free(st->indexes);

 	}

 #ifndef OPENSSL_NO_DEPRECATED

 static void BN_STACK_reset(BN_STACK *st)

 	{

 	st->depth = 0;

 	}

 #endif

 static int BN_STACK_push(BN_STACK *st, unsigned int idx)

 	{

 	if(st->depth == st->size)

 		/* Need to expand */

 		{

 		unsigned int newsize = (st->size ?

 				(st->size * 3 / 2) : BN_CTX_START_FRAMES);

 		unsigned int *newitems = OPENSSL_malloc(newsize *

 						sizeof(unsigned int));

 		if(!newitems) return 0;

 		if(st->depth)

 			memcpy(newitems, st->indexes, st->depth *

 						sizeof(unsigned int));

 		if(st->size) OPENSSL_free(st->indexes);

 		st->indexes = newitems;

 		st->size = newsize;

 		}

 	st->indexes[(st->depth)++] = idx;

 	return 1;

 	}

 static unsigned int BN_STACK_pop(BN_STACK *st)

 	{

 	return st->indexes[--(st->depth)];

 	}

 /***********/

 /* BN_POOL */

 /***********/

 static void BN_POOL_init(BN_POOL *p)

 	{

 	p->head = p->current = p->tail = NULL;

 	p->used = p->size = 0;

 	}

 static void BN_POOL_finish(BN_POOL *p)

 	{

 	while(p->head)

 		{

 		unsigned int loop = 0;

 		BIGNUM *bn = p->head->vals;

 		while(loop++ < BN_CTX_POOL_SIZE)

 			{

 			if(bn->d) BN_clear_free(bn);

 			bn++;

 			}

 		p->current = p->head->next;

 		OPENSSL_free(p->head);

 		p->head = p->current;

 		}

 	}

 #ifndef OPENSSL_NO_DEPRECATED

 static void BN_POOL_reset(BN_POOL *p)

 	{

 	BN_POOL_ITEM *item = p->head;

 	while(item)

 		{

 		unsigned int loop = 0;

 		BIGNUM *bn = item->vals;

 		while(loop++ < BN_CTX_POOL_SIZE)

 			{

 			if(bn->d) BN_clear(bn);

 			bn++;

 			}

 		item = item->next;

 		}

 	p->current = p->head;

 	p->used = 0;

 	}

 #endif

 static BIGNUM *BN_POOL_get(BN_POOL *p)

 	{

 	if(p->used == p->size)

 		{

 		BIGNUM *bn;

 		unsigned int loop = 0;

 		BN_POOL_ITEM *item = OPENSSL_malloc(sizeof(BN_POOL_ITEM));

 		if(!item) return NULL;

 		/* Initialise the structure */

 		bn = item->vals;

 		while(loop++ < BN_CTX_POOL_SIZE)

 			BN_init(bn++);

 		item->prev = p->tail;

 		item->next = NULL;

 		/* Link it in */

 		if(!p->head)

 			p->head = p->current = p->tail = item;

 		else

 			{

 			p->tail->next = item;

 			p->tail = item;

 			p->current = item;

 			}

 		p->size += BN_CTX_POOL_SIZE;

 		p->used++;

 		/* Return the first bignum from the new pool */

 		return item->vals;

 		}

 	if(!p->used)

 		p->current = p->head;

 	else if((p->used % BN_CTX_POOL_SIZE) == 0)

 		p->current = p->current->next;

 	return p->current->vals + ((p->used++) % BN_CTX_POOL_SIZE);

 	}

 static void BN_POOL_release(BN_POOL *p, unsigned int num)

 	{

 	unsigned int offset = (p->used - 1) % BN_CTX_POOL_SIZE;

 	p->used -= num;

 	while(num--)

 		{

 		bn_check_top(p->current->vals + offset);

 		if(!offset)

 			{

 			offset = BN_CTX_POOL_SIZE - 1;

 			p->current = p->current->prev;

 			}

 		else

 			offset--;

 		}

 	}