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/*
* Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the OpenSSL license (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
#include "internal/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 *);
static BIGNUM *BN_POOL_get(BN_POOL *, int);
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 *);
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;
/* Flags. */
int flags;
};
/* 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
BN_CTX *BN_CTX_new(void)
{
BN_CTX *ret;
if ((ret = OPENSSL_zalloc(sizeof(*ret))) == NULL) {
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);
return ret;
}
BN_CTX *BN_CTX_secure_new(void)
{
BN_CTX *ret = BN_CTX_new();
if (ret != NULL)
ret->flags = BN_FLG_SECURE;
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, ctx->flags)) == 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)
{
OPENSSL_free(st->indexes);
st->indexes = NULL;
}
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(sizeof(*newitems) * newsize);
if (newitems == NULL)
return 0;
if (st->depth)
memcpy(newitems, st->indexes, sizeof(*newitems) * st->depth);
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)
{
unsigned int loop;
BIGNUM *bn;
while (p->head) {
for (loop = 0, bn = p->head->vals; loop++ < BN_CTX_POOL_SIZE; bn++)
if (bn->d)
BN_clear_free(bn);
p->current = p->head->next;
OPENSSL_free(p->head);
p->head = p->current;
}
}
static BIGNUM *BN_POOL_get(BN_POOL *p, int flag)
{
BIGNUM *bn;
unsigned int loop;
/* Full; allocate a new pool item and link it in. */
if (p->used == p->size) {
BN_POOL_ITEM *item = OPENSSL_malloc(sizeof(*item));
if (item == NULL)
return NULL;
for (loop = 0, bn = item->vals; loop++ < BN_CTX_POOL_SIZE; bn++) {
bn_init(bn);
if ((flag & BN_FLG_SECURE) != 0)
BN_set_flags(bn, BN_FLG_SECURE);
}
item->prev = p->tail;
item->next = NULL;
if (p->head == NULL)
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 == 0) {
offset = BN_CTX_POOL_SIZE - 1;
p->current = p->current->prev;
} else
offset--;
}
}