/* crypto/bn/bn_ctx.c */
/* Written by Ulf Moeller for the OpenSSL project. */
/* ====================================================================
- * Copyright (c) 1998-2000 The OpenSSL Project. All rights reserved.
+ * 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
#include "cryptlib.h"
#include "bn_lcl.h"
-/* BN_CTX structure details */
-#define BN_CTX_NUM 32
-#define BN_CTX_NUM_POS 12
+/* TODO list
+ *
+ * 1. Check a bunch of "(words+1)" type hacks in various bignum functions and
+ * check they can be safely removed.
+ * - BN_bin2bn() looks pretty nasty with the miscellaneous +1 and +2 adjustments.
+ * Needs a full rubber-gloving, me thinks.
+ * - Check +1 and other ugliness in BN_from_montgomery()
+ * - Aspects of BN_bn2dec() also look a bit arbitrary
+ *
+ * 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
{
- int tos;
- BIGNUM bn[BN_CTX_NUM];
- int flags;
- int depth;
- int pos[BN_CTX_NUM_POS];
+ /* 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;
};
-#ifndef OPENSSL_NO_DEPRECATED
-void BN_CTX_init(BN_CTX *ctx)
+/* 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;
+ printf("(%08x): ", (unsigned int)ctx);
+ while(bnidx < ctx->used)
+ {
+ printf("%02x ", item->vals[bnidx++ % BN_CTX_POOL_SIZE].dmax);
+ if(!(bnidx % BN_CTX_POOL_SIZE))
+ item = item->next;
+ }
+ printf("\n");
+ bnidx = 0;
+ printf(" : ");
+ while(fpidx < stack->depth)
+ {
+ while(bnidx++ < stack->indexes[fpidx])
+ printf(" ");
+ printf("^^ ");
+ bnidx++;
+ fpidx++;
+ }
+ printf("\n");
+ }
+#define CTXDBG_ENTRY(str, ctx) do { \
+ ctxdbg_cur = (str); \
+ printf("Starting %s\n", ctxdbg_cur); \
+ ctxdbg(ctx); \
+ } while(0)
+#define CTXDBG_EXIT(ctx) do { \
+ printf("Ending %s\n", ctxdbg_cur); \
+ ctxdbg(ctx); \
+ } while(0)
+#define CTXDBG_RET(ctx,ret)
#else
-static void BN_CTX_init(BN_CTX *ctx)
+#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)
{
-#if 0 /* explicit version */
- int i;
- ctx->tos = 0;
- ctx->flags = 0;
- ctx->depth = 0;
+ /* 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;
- for (i = 0; i < BN_CTX_NUM; i++)
- BN_init(&(ctx->bn[i]));
-#else
- memset(ctx, 0, sizeof *ctx);
-#endif
}
+#endif
BN_CTX *BN_CTX_new(void)
{
- BN_CTX *ret;
-
- ret=(BN_CTX *)OPENSSL_malloc(sizeof(BN_CTX));
- if (ret == NULL)
+ BN_CTX *ret = OPENSSL_malloc(sizeof(BN_CTX));
+ if(!ret)
{
BNerr(BN_F_BN_CTX_NEW,ERR_R_MALLOC_FAILURE);
- return(NULL);
+ return NULL;
}
-
- BN_CTX_init(ret);
- ret->flags=BN_FLG_MALLOCED;
- return(ret);
+ /* 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)
{
- int i;
-
- if (ctx == NULL) return;
- assert(ctx->depth == 0);
-
- for (i=0; i < BN_CTX_NUM; i++) {
- bn_check_top(&(ctx->bn[i]));
- if (ctx->bn[i].d)
- BN_clear_free(&(ctx->bn[i]));
+#ifdef BN_CTX_DEBUG
+ BN_POOL_ITEM *pool = ctx->pool.head;
+ printf("BN_CTX_free, stack-size=%d, pool-bignums=%d\n",
+ ctx->stack.size, ctx->pool.size);
+ printf("dmaxs: ");
+ while(pool) {
+ unsigned loop = 0;
+ while(loop < BN_CTX_POOL_SIZE)
+ printf("%02x ", pool->vals[loop++].dmax);
+ pool = pool->next;
}
- if (ctx->flags & BN_FLG_MALLOCED)
- OPENSSL_free(ctx);
+ printf("\n");
+#endif
+ BN_STACK_finish(&ctx->stack);
+ BN_POOL_finish(&ctx->pool);
+ OPENSSL_free(ctx);
}
void BN_CTX_start(BN_CTX *ctx)
{
- if (ctx->depth < BN_CTX_NUM_POS)
- ctx->pos[ctx->depth] = ctx->tos;
- ctx->depth++;
+ 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))
+ {
+ /* I know this isn't BN_CTX_get, but ... */
+ BNerr(BN_F_BN_CTX_GET,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;
- /* Note: If BN_CTX_get is ever changed to allocate BIGNUMs dynamically,
- * make sure that if BN_CTX_get fails once it will return NULL again
- * until BN_CTX_end is called. (This is so that callers have to check
- * only the last return value.)
- */
- if (ctx->depth > BN_CTX_NUM_POS || ctx->tos >= BN_CTX_NUM)
+ CTXDBG_ENTRY("BN_CTX_get", ctx);
+ if(ctx->err_stack || ctx->too_many) return NULL;
+ if((ret = BN_POOL_get(&ctx->pool)) == NULL)
{
- if (!ctx->too_many)
- {
- BNerr(BN_F_BN_CTX_GET,BN_R_TOO_MANY_TEMPORARY_VARIABLES);
- /* disable error code until BN_CTX_end is called: */
- ctx->too_many = 1;
- }
+ /* 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;
}
- ret = ctx->bn + (ctx->tos++);
- /* always return a 'zeroed' bignum */
+ /* OK, make sure the returned bignum is "zero" */
BN_zero(ret);
+ ctx->used++;
+ CTXDBG_RET(ctx, ret);
return ret;
}
-void BN_CTX_end(BN_CTX *ctx)
+/************/
+/* 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 (ctx == NULL) return;
- assert(ctx->depth > 0);
- if (ctx->depth == 0)
- /* should never happen, but we can tolerate it if not in
- * debug mode (could be a 'goto err' in the calling function
- * before BN_CTX_start was reached) */
- BN_CTX_start(ctx);
+ if(st->size) OPENSSL_free(st->indexes);
+ }
- ctx->too_many = 0;
- ctx->depth--;
- if (ctx->depth < BN_CTX_NUM_POS)
-#ifndef BN_DEBUG
- ctx->tos = ctx->pos[ctx->depth];
-#else
- while(ctx->tos > ctx->pos[ctx->depth])
- bn_check_top(&ctx->bn[--(ctx->tos)]);
+#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--;
+ }
}
+
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