--- /dev/null
+/* 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). */
+
+
+#include <openssl/bn.h>
+
+#include <string.h>
+
+#include <openssl/err.h>
+#include <openssl/mem.h>
+
+#include "../../internal.h"
+
+
+// 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
+
+// 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;
+
+
+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 *);
+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;
+};
+
+BN_CTX *BN_CTX_new(void) {
+ BN_CTX *ret = OPENSSL_malloc(sizeof(BN_CTX));
+ if (!ret) {
+ OPENSSL_PUT_ERROR(BN, 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;
+ }
+
+ BN_STACK_finish(&ctx->stack);
+ BN_POOL_finish(&ctx->pool);
+ OPENSSL_free(ctx);
+}
+
+void BN_CTX_start(BN_CTX *ctx) {
+ // If we're already overflowing ...
+ if (ctx->err_stack || ctx->too_many) {
+ ctx->err_stack++;
+ } else if (!BN_STACK_push(&ctx->stack, ctx->used)) {
+ // (Try to) get a new frame pointer
+ OPENSSL_PUT_ERROR(BN, BN_R_TOO_MANY_TEMPORARY_VARIABLES);
+ ctx->err_stack++;
+ }
+}
+
+BIGNUM *BN_CTX_get(BN_CTX *ctx) {
+ BIGNUM *ret;
+ if (ctx->err_stack || ctx->too_many) {
+ return NULL;
+ }
+
+ ret = BN_POOL_get(&ctx->pool);
+ if (ret == NULL) {
+ // Setting too_many prevents repeated "get" attempts from
+ // cluttering the error stack.
+ ctx->too_many = 1;
+ OPENSSL_PUT_ERROR(BN, BN_R_TOO_MANY_TEMPORARY_VARIABLES);
+ return NULL;
+ }
+
+ // OK, make sure the returned bignum is "zero"
+ BN_zero(ret);
+ ctx->used++;
+ return ret;
+}
+
+void BN_CTX_end(BN_CTX *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;
+ }
+}
+
+
+// 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);
+}
+
+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) {
+ OPENSSL_memcpy(newitems, st->indexes, st->depth * sizeof(unsigned int));
+ }
+ 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)];
+}
+
+
+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) {
+ for (size_t i = 0; i < BN_CTX_POOL_SIZE; i++) {
+ BN_clear_free(&p->head->vals[i]);
+ }
+
+ p->current = p->head->next;
+ OPENSSL_free(p->head);
+ p->head = p->current;
+ }
+}
+
+static BIGNUM *BN_POOL_get(BN_POOL *p) {
+ if (p->used == p->size) {
+ BN_POOL_ITEM *item = OPENSSL_malloc(sizeof(BN_POOL_ITEM));
+ if (!item) {
+ return NULL;
+ }
+
+ // Initialise the structure
+ for (size_t i = 0; i < BN_CTX_POOL_SIZE; i++) {
+ BN_init(&item->vals[i]);
+ }
+
+ 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--) {
+ if (!offset) {
+ offset = BN_CTX_POOL_SIZE - 1;
+ p->current = p->current->prev;
+ } else {
+ offset--;
+ }
+ }
+}
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