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361 lines
9.5 KiB
C
361 lines
9.5 KiB
C
/*
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* Copyright 2000-2019 The OpenSSL Project Authors. All Rights Reserved.
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*
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* Licensed under the OpenSSL license (the "License"). You may not use
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* this file except in compliance with the License. You can obtain a copy
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* in the file LICENSE in the source distribution or at
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* https://www.openssl.org/source/license.html
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*/
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#include "internal/cryptlib.h"
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#include "bn_lcl.h"
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/*-
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* TODO list
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*
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* 1. Check a bunch of "(words+1)" type hacks in various bignum functions and
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* check they can be safely removed.
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* - Check +1 and other ugliness in BN_from_montgomery()
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*
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* 2. Consider allowing a BN_new_ex() that, at least, lets you specify an
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* appropriate 'block' size that will be honoured by bn_expand_internal() to
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* prevent piddly little reallocations. OTOH, profiling bignum expansions in
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* BN_CTX doesn't show this to be a big issue.
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*/
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/* How many bignums are in each "pool item"; */
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#define BN_CTX_POOL_SIZE 16
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/* The stack frame info is resizing, set a first-time expansion size; */
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#define BN_CTX_START_FRAMES 32
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/***********/
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/* BN_POOL */
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/***********/
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/* A bundle of bignums that can be linked with other bundles */
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typedef struct bignum_pool_item {
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/* The bignum values */
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BIGNUM vals[BN_CTX_POOL_SIZE];
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/* Linked-list admin */
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struct bignum_pool_item *prev, *next;
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} BN_POOL_ITEM;
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/* A linked-list of bignums grouped in bundles */
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typedef struct bignum_pool {
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/* Linked-list admin */
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BN_POOL_ITEM *head, *current, *tail;
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/* Stack depth and allocation size */
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unsigned used, size;
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} BN_POOL;
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static void BN_POOL_init(BN_POOL *);
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static void BN_POOL_finish(BN_POOL *);
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static BIGNUM *BN_POOL_get(BN_POOL *, int);
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static void BN_POOL_release(BN_POOL *, unsigned int);
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/************/
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/* BN_STACK */
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/************/
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/* A wrapper to manage the "stack frames" */
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typedef struct bignum_ctx_stack {
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/* Array of indexes into the bignum stack */
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unsigned int *indexes;
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/* Number of stack frames, and the size of the allocated array */
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unsigned int depth, size;
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} BN_STACK;
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static void BN_STACK_init(BN_STACK *);
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static void BN_STACK_finish(BN_STACK *);
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static int BN_STACK_push(BN_STACK *, unsigned int);
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static unsigned int BN_STACK_pop(BN_STACK *);
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/**********/
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/* BN_CTX */
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/**********/
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/* The opaque BN_CTX type */
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struct bignum_ctx {
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/* The bignum bundles */
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BN_POOL pool;
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/* The "stack frames", if you will */
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BN_STACK stack;
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/* The number of bignums currently assigned */
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unsigned int used;
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/* Depth of stack overflow */
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int err_stack;
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/* Block "gets" until an "end" (compatibility behaviour) */
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int too_many;
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/* Flags. */
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int flags;
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};
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/* Enable this to find BN_CTX bugs */
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#ifdef BN_CTX_DEBUG
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static const char *ctxdbg_cur = NULL;
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static void ctxdbg(BN_CTX *ctx)
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{
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unsigned int bnidx = 0, fpidx = 0;
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BN_POOL_ITEM *item = ctx->pool.head;
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BN_STACK *stack = &ctx->stack;
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fprintf(stderr, "(%16p): ", ctx);
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while (bnidx < ctx->used) {
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fprintf(stderr, "%03x ", item->vals[bnidx++ % BN_CTX_POOL_SIZE].dmax);
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if (!(bnidx % BN_CTX_POOL_SIZE))
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item = item->next;
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}
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fprintf(stderr, "\n");
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bnidx = 0;
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fprintf(stderr, " : ");
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while (fpidx < stack->depth) {
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while (bnidx++ < stack->indexes[fpidx])
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fprintf(stderr, " ");
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fprintf(stderr, "^^^ ");
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bnidx++;
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fpidx++;
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}
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fprintf(stderr, "\n");
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}
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# define CTXDBG_ENTRY(str, ctx) do { \
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ctxdbg_cur = (str); \
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fprintf(stderr,"Starting %s\n", ctxdbg_cur); \
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ctxdbg(ctx); \
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} while(0)
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# define CTXDBG_EXIT(ctx) do { \
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fprintf(stderr,"Ending %s\n", ctxdbg_cur); \
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ctxdbg(ctx); \
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} while(0)
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# define CTXDBG_RET(ctx,ret)
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#else
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# define CTXDBG_ENTRY(str, ctx)
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# define CTXDBG_EXIT(ctx)
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# define CTXDBG_RET(ctx,ret)
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#endif
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BN_CTX *BN_CTX_new(void)
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{
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BN_CTX *ret;
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if ((ret = OPENSSL_zalloc(sizeof(*ret))) == NULL) {
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BNerr(BN_F_BN_CTX_NEW, ERR_R_MALLOC_FAILURE);
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return NULL;
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}
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/* Initialise the structure */
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BN_POOL_init(&ret->pool);
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BN_STACK_init(&ret->stack);
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return ret;
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}
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BN_CTX *BN_CTX_secure_new(void)
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{
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BN_CTX *ret = BN_CTX_new();
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if (ret != NULL)
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ret->flags = BN_FLG_SECURE;
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return ret;
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}
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void BN_CTX_free(BN_CTX *ctx)
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{
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if (ctx == NULL)
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return;
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#ifdef BN_CTX_DEBUG
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{
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BN_POOL_ITEM *pool = ctx->pool.head;
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fprintf(stderr, "BN_CTX_free, stack-size=%d, pool-bignums=%d\n",
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ctx->stack.size, ctx->pool.size);
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fprintf(stderr, "dmaxs: ");
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while (pool) {
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unsigned loop = 0;
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while (loop < BN_CTX_POOL_SIZE)
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fprintf(stderr, "%02x ", pool->vals[loop++].dmax);
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pool = pool->next;
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}
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fprintf(stderr, "\n");
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}
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#endif
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BN_STACK_finish(&ctx->stack);
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BN_POOL_finish(&ctx->pool);
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OPENSSL_free(ctx);
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}
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void BN_CTX_start(BN_CTX *ctx)
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{
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CTXDBG_ENTRY("BN_CTX_start", ctx);
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/* If we're already overflowing ... */
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if (ctx->err_stack || ctx->too_many)
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ctx->err_stack++;
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/* (Try to) get a new frame pointer */
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else if (!BN_STACK_push(&ctx->stack, ctx->used)) {
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BNerr(BN_F_BN_CTX_START, BN_R_TOO_MANY_TEMPORARY_VARIABLES);
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ctx->err_stack++;
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}
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CTXDBG_EXIT(ctx);
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}
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void BN_CTX_end(BN_CTX *ctx)
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{
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CTXDBG_ENTRY("BN_CTX_end", ctx);
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if (ctx->err_stack)
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ctx->err_stack--;
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else {
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unsigned int fp = BN_STACK_pop(&ctx->stack);
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/* Does this stack frame have anything to release? */
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if (fp < ctx->used)
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BN_POOL_release(&ctx->pool, ctx->used - fp);
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ctx->used = fp;
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/* Unjam "too_many" in case "get" had failed */
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ctx->too_many = 0;
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}
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CTXDBG_EXIT(ctx);
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}
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BIGNUM *BN_CTX_get(BN_CTX *ctx)
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{
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BIGNUM *ret;
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CTXDBG_ENTRY("BN_CTX_get", ctx);
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if (ctx->err_stack || ctx->too_many)
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return NULL;
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if ((ret = BN_POOL_get(&ctx->pool, ctx->flags)) == NULL) {
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/*
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* Setting too_many prevents repeated "get" attempts from cluttering
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* the error stack.
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*/
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ctx->too_many = 1;
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BNerr(BN_F_BN_CTX_GET, BN_R_TOO_MANY_TEMPORARY_VARIABLES);
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return NULL;
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}
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/* OK, make sure the returned bignum is "zero" */
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BN_zero(ret);
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/* clear BN_FLG_CONSTTIME if leaked from previous frames */
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ret->flags &= (~BN_FLG_CONSTTIME);
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ctx->used++;
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CTXDBG_RET(ctx, ret);
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return ret;
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}
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/************/
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/* BN_STACK */
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/************/
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static void BN_STACK_init(BN_STACK *st)
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{
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st->indexes = NULL;
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st->depth = st->size = 0;
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}
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static void BN_STACK_finish(BN_STACK *st)
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{
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OPENSSL_free(st->indexes);
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st->indexes = NULL;
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}
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static int BN_STACK_push(BN_STACK *st, unsigned int idx)
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{
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if (st->depth == st->size) {
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/* Need to expand */
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unsigned int newsize =
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st->size ? (st->size * 3 / 2) : BN_CTX_START_FRAMES;
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unsigned int *newitems;
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if ((newitems = OPENSSL_malloc(sizeof(*newitems) * newsize)) == NULL) {
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BNerr(BN_F_BN_STACK_PUSH, ERR_R_MALLOC_FAILURE);
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return 0;
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}
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if (st->depth)
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memcpy(newitems, st->indexes, sizeof(*newitems) * st->depth);
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OPENSSL_free(st->indexes);
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st->indexes = newitems;
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st->size = newsize;
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}
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st->indexes[(st->depth)++] = idx;
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return 1;
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}
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static unsigned int BN_STACK_pop(BN_STACK *st)
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{
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return st->indexes[--(st->depth)];
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}
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/***********/
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/* BN_POOL */
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/***********/
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static void BN_POOL_init(BN_POOL *p)
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{
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p->head = p->current = p->tail = NULL;
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p->used = p->size = 0;
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}
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static void BN_POOL_finish(BN_POOL *p)
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{
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unsigned int loop;
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BIGNUM *bn;
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while (p->head) {
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for (loop = 0, bn = p->head->vals; loop++ < BN_CTX_POOL_SIZE; bn++)
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if (bn->d)
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BN_clear_free(bn);
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p->current = p->head->next;
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OPENSSL_free(p->head);
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p->head = p->current;
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}
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}
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static BIGNUM *BN_POOL_get(BN_POOL *p, int flag)
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{
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BIGNUM *bn;
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unsigned int loop;
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/* Full; allocate a new pool item and link it in. */
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if (p->used == p->size) {
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BN_POOL_ITEM *item;
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if ((item = OPENSSL_malloc(sizeof(*item))) == NULL) {
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BNerr(BN_F_BN_POOL_GET, ERR_R_MALLOC_FAILURE);
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return NULL;
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}
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for (loop = 0, bn = item->vals; loop++ < BN_CTX_POOL_SIZE; bn++) {
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bn_init(bn);
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if ((flag & BN_FLG_SECURE) != 0)
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BN_set_flags(bn, BN_FLG_SECURE);
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}
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item->prev = p->tail;
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item->next = NULL;
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if (p->head == NULL)
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p->head = p->current = p->tail = item;
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else {
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p->tail->next = item;
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p->tail = item;
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p->current = item;
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}
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p->size += BN_CTX_POOL_SIZE;
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p->used++;
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/* Return the first bignum from the new pool */
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return item->vals;
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}
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if (!p->used)
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p->current = p->head;
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else if ((p->used % BN_CTX_POOL_SIZE) == 0)
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p->current = p->current->next;
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return p->current->vals + ((p->used++) % BN_CTX_POOL_SIZE);
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}
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static void BN_POOL_release(BN_POOL *p, unsigned int num)
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{
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unsigned int offset = (p->used - 1) % BN_CTX_POOL_SIZE;
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p->used -= num;
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while (num--) {
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bn_check_top(p->current->vals + offset);
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if (offset == 0) {
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offset = BN_CTX_POOL_SIZE - 1;
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p->current = p->current->prev;
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} else
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offset--;
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}
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}
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