/* 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, "(%16p): ", ctx);

    while (bnidx < ctx->used) {

        fprintf(stderr, "%03x ", 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

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

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;

}

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);

}

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);

}

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);

}

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--;

    }

}