[331] | 1 | /*
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| 2 | * Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.
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| 3 | *
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| 4 | * Licensed under the OpenSSL license (the "License"). You may not use
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| 5 | * this file except in compliance with the License. You can obtain a copy
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| 6 | * in the file LICENSE in the source distribution or at
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| 7 | * https://www.openssl.org/source/license.html
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| 8 | */
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| 9 |
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| 10 | #include "internal/cryptlib.h"
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| 11 | #include "bn_lcl.h"
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| 12 |
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| 13 | /*-
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| 14 | * TODO list
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| 15 | *
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| 16 | * 1. Check a bunch of "(words+1)" type hacks in various bignum functions and
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| 17 | * check they can be safely removed.
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| 18 | * - Check +1 and other ugliness in BN_from_montgomery()
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| 19 | *
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| 20 | * 2. Consider allowing a BN_new_ex() that, at least, lets you specify an
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| 21 | * appropriate 'block' size that will be honoured by bn_expand_internal() to
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| 22 | * prevent piddly little reallocations. OTOH, profiling bignum expansions in
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| 23 | * BN_CTX doesn't show this to be a big issue.
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| 24 | */
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| 25 |
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| 26 | /* How many bignums are in each "pool item"; */
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| 27 | #define BN_CTX_POOL_SIZE 16
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| 28 | /* The stack frame info is resizing, set a first-time expansion size; */
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| 29 | #define BN_CTX_START_FRAMES 32
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| 30 |
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| 31 | /***********/
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| 32 | /* BN_POOL */
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| 33 | /***********/
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| 34 |
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| 35 | /* A bundle of bignums that can be linked with other bundles */
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| 36 | typedef struct bignum_pool_item {
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| 37 | /* The bignum values */
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| 38 | BIGNUM vals[BN_CTX_POOL_SIZE];
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| 39 | /* Linked-list admin */
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| 40 | struct bignum_pool_item *prev, *next;
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| 41 | } BN_POOL_ITEM;
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| 42 | /* A linked-list of bignums grouped in bundles */
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| 43 | typedef struct bignum_pool {
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| 44 | /* Linked-list admin */
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| 45 | BN_POOL_ITEM *head, *current, *tail;
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| 46 | /* Stack depth and allocation size */
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| 47 | unsigned used, size;
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| 48 | } BN_POOL;
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| 49 | static void BN_POOL_init(BN_POOL *);
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| 50 | static void BN_POOL_finish(BN_POOL *);
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| 51 | static BIGNUM *BN_POOL_get(BN_POOL *, int);
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| 52 | static void BN_POOL_release(BN_POOL *, unsigned int);
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| 53 |
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| 54 | /************/
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| 55 | /* BN_STACK */
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| 56 | /************/
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| 57 |
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| 58 | /* A wrapper to manage the "stack frames" */
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| 59 | typedef struct bignum_ctx_stack {
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| 60 | /* Array of indexes into the bignum stack */
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| 61 | unsigned int *indexes;
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| 62 | /* Number of stack frames, and the size of the allocated array */
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| 63 | unsigned int depth, size;
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| 64 | } BN_STACK;
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| 65 | static void BN_STACK_init(BN_STACK *);
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| 66 | static void BN_STACK_finish(BN_STACK *);
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| 67 | static int BN_STACK_push(BN_STACK *, unsigned int);
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| 68 | static unsigned int BN_STACK_pop(BN_STACK *);
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| 69 |
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| 70 | /**********/
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| 71 | /* BN_CTX */
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| 72 | /**********/
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| 73 |
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| 74 | /* The opaque BN_CTX type */
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| 75 | struct bignum_ctx {
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| 76 | /* The bignum bundles */
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| 77 | BN_POOL pool;
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| 78 | /* The "stack frames", if you will */
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| 79 | BN_STACK stack;
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| 80 | /* The number of bignums currently assigned */
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| 81 | unsigned int used;
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| 82 | /* Depth of stack overflow */
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| 83 | int err_stack;
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| 84 | /* Block "gets" until an "end" (compatibility behaviour) */
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| 85 | int too_many;
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| 86 | /* Flags. */
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| 87 | int flags;
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| 88 | };
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| 89 |
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| 90 | /* Enable this to find BN_CTX bugs */
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| 91 | #ifdef BN_CTX_DEBUG
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| 92 | static const char *ctxdbg_cur = NULL;
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| 93 | static void ctxdbg(BN_CTX *ctx)
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| 94 | {
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| 95 | unsigned int bnidx = 0, fpidx = 0;
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| 96 | BN_POOL_ITEM *item = ctx->pool.head;
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| 97 | BN_STACK *stack = &ctx->stack;
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| 98 | fprintf(stderr, "(%16p): ", ctx);
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| 99 | while (bnidx < ctx->used) {
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| 100 | fprintf(stderr, "%03x ", item->vals[bnidx++ % BN_CTX_POOL_SIZE].dmax);
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| 101 | if (!(bnidx % BN_CTX_POOL_SIZE))
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| 102 | item = item->next;
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| 103 | }
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| 104 | fprintf(stderr, "\n");
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| 105 | bnidx = 0;
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| 106 | fprintf(stderr, " : ");
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| 107 | while (fpidx < stack->depth) {
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| 108 | while (bnidx++ < stack->indexes[fpidx])
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| 109 | fprintf(stderr, " ");
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| 110 | fprintf(stderr, "^^^ ");
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| 111 | bnidx++;
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| 112 | fpidx++;
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| 113 | }
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| 114 | fprintf(stderr, "\n");
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| 115 | }
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| 116 |
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| 117 | # define CTXDBG_ENTRY(str, ctx) do { \
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| 118 | ctxdbg_cur = (str); \
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| 119 | fprintf(stderr,"Starting %s\n", ctxdbg_cur); \
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| 120 | ctxdbg(ctx); \
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| 121 | } while(0)
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| 122 | # define CTXDBG_EXIT(ctx) do { \
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| 123 | fprintf(stderr,"Ending %s\n", ctxdbg_cur); \
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| 124 | ctxdbg(ctx); \
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| 125 | } while(0)
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| 126 | # define CTXDBG_RET(ctx,ret)
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| 127 | #else
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| 128 | # define CTXDBG_ENTRY(str, ctx)
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| 129 | # define CTXDBG_EXIT(ctx)
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| 130 | # define CTXDBG_RET(ctx,ret)
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| 131 | #endif
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| 132 |
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| 133 |
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| 134 | BN_CTX *BN_CTX_new(void)
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| 135 | {
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| 136 | BN_CTX *ret;
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| 137 |
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| 138 | if ((ret = OPENSSL_zalloc(sizeof(*ret))) == NULL) {
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| 139 | BNerr(BN_F_BN_CTX_NEW, ERR_R_MALLOC_FAILURE);
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| 140 | return NULL;
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| 141 | }
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| 142 | /* Initialise the structure */
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| 143 | BN_POOL_init(&ret->pool);
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| 144 | BN_STACK_init(&ret->stack);
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| 145 | return ret;
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| 146 | }
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| 147 |
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| 148 | BN_CTX *BN_CTX_secure_new(void)
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| 149 | {
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| 150 | BN_CTX *ret = BN_CTX_new();
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| 151 |
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| 152 | if (ret != NULL)
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| 153 | ret->flags = BN_FLG_SECURE;
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| 154 | return ret;
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| 155 | }
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| 156 |
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| 157 | void BN_CTX_free(BN_CTX *ctx)
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| 158 | {
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| 159 | if (ctx == NULL)
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| 160 | return;
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| 161 | #ifdef BN_CTX_DEBUG
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| 162 | {
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| 163 | BN_POOL_ITEM *pool = ctx->pool.head;
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| 164 | fprintf(stderr, "BN_CTX_free, stack-size=%d, pool-bignums=%d\n",
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| 165 | ctx->stack.size, ctx->pool.size);
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| 166 | fprintf(stderr, "dmaxs: ");
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| 167 | while (pool) {
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| 168 | unsigned loop = 0;
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| 169 | while (loop < BN_CTX_POOL_SIZE)
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| 170 | fprintf(stderr, "%02x ", pool->vals[loop++].dmax);
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| 171 | pool = pool->next;
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| 172 | }
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| 173 | fprintf(stderr, "\n");
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| 174 | }
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| 175 | #endif
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| 176 | BN_STACK_finish(&ctx->stack);
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| 177 | BN_POOL_finish(&ctx->pool);
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| 178 | OPENSSL_free(ctx);
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| 179 | }
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| 180 |
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| 181 | void BN_CTX_start(BN_CTX *ctx)
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| 182 | {
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| 183 | CTXDBG_ENTRY("BN_CTX_start", ctx);
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| 184 | /* If we're already overflowing ... */
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| 185 | if (ctx->err_stack || ctx->too_many)
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| 186 | ctx->err_stack++;
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| 187 | /* (Try to) get a new frame pointer */
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| 188 | else if (!BN_STACK_push(&ctx->stack, ctx->used)) {
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| 189 | BNerr(BN_F_BN_CTX_START, BN_R_TOO_MANY_TEMPORARY_VARIABLES);
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| 190 | ctx->err_stack++;
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| 191 | }
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| 192 | CTXDBG_EXIT(ctx);
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| 193 | }
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| 194 |
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| 195 | void BN_CTX_end(BN_CTX *ctx)
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| 196 | {
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| 197 | CTXDBG_ENTRY("BN_CTX_end", ctx);
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| 198 | if (ctx->err_stack)
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| 199 | ctx->err_stack--;
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| 200 | else {
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| 201 | unsigned int fp = BN_STACK_pop(&ctx->stack);
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| 202 | /* Does this stack frame have anything to release? */
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| 203 | if (fp < ctx->used)
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| 204 | BN_POOL_release(&ctx->pool, ctx->used - fp);
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| 205 | ctx->used = fp;
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| 206 | /* Unjam "too_many" in case "get" had failed */
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| 207 | ctx->too_many = 0;
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| 208 | }
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| 209 | CTXDBG_EXIT(ctx);
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| 210 | }
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| 211 |
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| 212 | BIGNUM *BN_CTX_get(BN_CTX *ctx)
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| 213 | {
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| 214 | BIGNUM *ret;
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| 215 |
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| 216 | CTXDBG_ENTRY("BN_CTX_get", ctx);
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| 217 | if (ctx->err_stack || ctx->too_many)
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| 218 | return NULL;
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| 219 | if ((ret = BN_POOL_get(&ctx->pool, ctx->flags)) == NULL) {
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| 220 | /*
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| 221 | * Setting too_many prevents repeated "get" attempts from cluttering
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| 222 | * the error stack.
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| 223 | */
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| 224 | ctx->too_many = 1;
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| 225 | BNerr(BN_F_BN_CTX_GET, BN_R_TOO_MANY_TEMPORARY_VARIABLES);
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| 226 | return NULL;
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| 227 | }
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| 228 | /* OK, make sure the returned bignum is "zero" */
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| 229 | BN_zero(ret);
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| 230 | ctx->used++;
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| 231 | CTXDBG_RET(ctx, ret);
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| 232 | return ret;
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| 233 | }
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| 234 |
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| 235 | /************/
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| 236 | /* BN_STACK */
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| 237 | /************/
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| 238 |
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| 239 | static void BN_STACK_init(BN_STACK *st)
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| 240 | {
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| 241 | st->indexes = NULL;
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| 242 | st->depth = st->size = 0;
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| 243 | }
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| 244 |
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| 245 | static void BN_STACK_finish(BN_STACK *st)
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| 246 | {
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| 247 | OPENSSL_free(st->indexes);
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| 248 | st->indexes = NULL;
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| 249 | }
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| 250 |
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| 251 |
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| 252 | static int BN_STACK_push(BN_STACK *st, unsigned int idx)
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| 253 | {
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| 254 | if (st->depth == st->size) {
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| 255 | /* Need to expand */
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| 256 | unsigned int newsize =
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| 257 | st->size ? (st->size * 3 / 2) : BN_CTX_START_FRAMES;
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| 258 | unsigned int *newitems = OPENSSL_malloc(sizeof(*newitems) * newsize);
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| 259 | if (newitems == NULL)
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| 260 | return 0;
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| 261 | if (st->depth)
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| 262 | memcpy(newitems, st->indexes, sizeof(*newitems) * st->depth);
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| 263 | OPENSSL_free(st->indexes);
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| 264 | st->indexes = newitems;
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| 265 | st->size = newsize;
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| 266 | }
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| 267 | st->indexes[(st->depth)++] = idx;
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| 268 | return 1;
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| 269 | }
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| 270 |
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| 271 | static unsigned int BN_STACK_pop(BN_STACK *st)
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| 272 | {
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| 273 | return st->indexes[--(st->depth)];
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| 274 | }
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| 275 |
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| 276 | /***********/
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| 277 | /* BN_POOL */
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| 278 | /***********/
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| 279 |
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| 280 | static void BN_POOL_init(BN_POOL *p)
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| 281 | {
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| 282 | p->head = p->current = p->tail = NULL;
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| 283 | p->used = p->size = 0;
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| 284 | }
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| 285 |
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| 286 | static void BN_POOL_finish(BN_POOL *p)
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| 287 | {
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| 288 | unsigned int loop;
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| 289 | BIGNUM *bn;
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| 290 |
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| 291 | while (p->head) {
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| 292 | for (loop = 0, bn = p->head->vals; loop++ < BN_CTX_POOL_SIZE; bn++)
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| 293 | if (bn->d)
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| 294 | BN_clear_free(bn);
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| 295 | p->current = p->head->next;
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| 296 | OPENSSL_free(p->head);
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| 297 | p->head = p->current;
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| 298 | }
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| 299 | }
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| 300 |
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| 301 |
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| 302 | static BIGNUM *BN_POOL_get(BN_POOL *p, int flag)
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| 303 | {
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| 304 | BIGNUM *bn;
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| 305 | unsigned int loop;
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| 306 |
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| 307 | /* Full; allocate a new pool item and link it in. */
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| 308 | if (p->used == p->size) {
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| 309 | BN_POOL_ITEM *item = OPENSSL_malloc(sizeof(*item));
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| 310 | if (item == NULL)
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| 311 | return NULL;
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| 312 | for (loop = 0, bn = item->vals; loop++ < BN_CTX_POOL_SIZE; bn++) {
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| 313 | bn_init(bn);
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| 314 | if ((flag & BN_FLG_SECURE) != 0)
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| 315 | BN_set_flags(bn, BN_FLG_SECURE);
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| 316 | }
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| 317 | item->prev = p->tail;
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| 318 | item->next = NULL;
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| 319 |
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| 320 | if (p->head == NULL)
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| 321 | p->head = p->current = p->tail = item;
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| 322 | else {
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| 323 | p->tail->next = item;
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| 324 | p->tail = item;
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| 325 | p->current = item;
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| 326 | }
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| 327 | p->size += BN_CTX_POOL_SIZE;
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| 328 | p->used++;
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| 329 | /* Return the first bignum from the new pool */
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| 330 | return item->vals;
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| 331 | }
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| 332 |
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| 333 | if (!p->used)
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| 334 | p->current = p->head;
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| 335 | else if ((p->used % BN_CTX_POOL_SIZE) == 0)
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| 336 | p->current = p->current->next;
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| 337 | return p->current->vals + ((p->used++) % BN_CTX_POOL_SIZE);
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| 338 | }
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| 339 |
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| 340 | static void BN_POOL_release(BN_POOL *p, unsigned int num)
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| 341 | {
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| 342 | unsigned int offset = (p->used - 1) % BN_CTX_POOL_SIZE;
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| 343 |
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| 344 | p->used -= num;
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| 345 | while (num--) {
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| 346 | bn_check_top(p->current->vals + offset);
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| 347 | if (offset == 0) {
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| 348 | offset = BN_CTX_POOL_SIZE - 1;
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| 349 | p->current = p->current->prev;
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| 350 | } else
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| 351 | offset--;
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| 352 | }
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| 353 | }
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