crypto/bn/bn_ctx.c

   1 /* crypto/bn/bn_ctx.c */
   2 /* Written by Ulf Moeller for the OpenSSL project. */
   3 /* ====================================================================
   4  * Copyright (c) 1998-2004 The OpenSSL Project.  All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  *
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  *
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in
  15  *    the documentation and/or other materials provided with the
  16  *    distribution.
  17  *
  18  * 3. All advertising materials mentioning features or use of this
  19  *    software must display the following acknowledgment:
  20  *    "This product includes software developed by the OpenSSL Project
  21  *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
  22  *
  23  * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
  24  *    endorse or promote products derived from this software without
  25  *    prior written permission. For written permission, please contact
  26  *    openssl-core@openssl.org.
  27  *
  28  * 5. Products derived from this software may not be called "OpenSSL"
  29  *    nor may "OpenSSL" appear in their names without prior written
  30  *    permission of the OpenSSL Project.
  31  *
  32  * 6. Redistributions of any form whatsoever must retain the following
  33  *    acknowledgment:
  34  *    "This product includes software developed by the OpenSSL Project
  35  *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
  36  *
  37  * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
  38  * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  39  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  40  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
  41  * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  42  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  43  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  44  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  45  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  46  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  47  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
  48  * OF THE POSSIBILITY OF SUCH DAMAGE.
  49  * ====================================================================
  50  *
  51  * This product includes cryptographic software written by Eric Young
  52  * (eay@cryptsoft.com).  This product includes software written by Tim
  53  * Hudson (tjh@cryptsoft.com).
  54  *
  55  */
  56
  57 #if !defined(BN_CTX_DEBUG) && !defined(BN_DEBUG)
  58 # ifndef NDEBUG
  59 #  define NDEBUG
  60 # endif
  61 #endif
  62
  63 #include <assert.h>
  64
  65 #include "internal/cryptlib.h"
  66 #include "bn_lcl.h"
  67
  68 /*-
  69  * TODO list
  70  *
  71  * 1. Check a bunch of "(words+1)" type hacks in various bignum functions and
  72  * check they can be safely removed.
  73  *  - Check +1 and other ugliness in BN_from_montgomery()
  74  *
  75  * 2. Consider allowing a BN_new_ex() that, at least, lets you specify an
  76  * appropriate 'block' size that will be honoured by bn_expand_internal() to
  77  * prevent piddly little reallocations. OTOH, profiling bignum expansions in
  78  * BN_CTX doesn't show this to be a big issue.
  79  */
  80
  81 /* How many bignums are in each "pool item"; */
  82 #define BN_CTX_POOL_SIZE        16
  83 /* The stack frame info is resizing, set a first-time expansion size; */
  84 #define BN_CTX_START_FRAMES     32
  85
  86 /***********/
  87 /* BN_POOL */
  88 /***********/
  89
  90 /* A bundle of bignums that can be linked with other bundles */
  91 typedef struct bignum_pool_item {
  92     /* The bignum values */
  93     BIGNUM vals[BN_CTX_POOL_SIZE];
  94     /* Linked-list admin */
  95     struct bignum_pool_item *prev, *next;
  96 } BN_POOL_ITEM;
  97 /* A linked-list of bignums grouped in bundles */
  98 typedef struct bignum_pool {
  99     /* Linked-list admin */
 100     BN_POOL_ITEM *head, *current, *tail;
 101     /* Stack depth and allocation size */
 102     unsigned used, size;
 103 } BN_POOL;
 104 static void BN_POOL_init(BN_POOL *);
 105 static void BN_POOL_finish(BN_POOL *);
 106 static BIGNUM *BN_POOL_get(BN_POOL *);
 107 static void BN_POOL_release(BN_POOL *, unsigned int);
 108
 109 /************/
 110 /* BN_STACK */
 111 /************/
 112
 113 /* A wrapper to manage the "stack frames" */
 114 typedef struct bignum_ctx_stack {
 115     /* Array of indexes into the bignum stack */
 116     unsigned int *indexes;
 117     /* Number of stack frames, and the size of the allocated array */
 118     unsigned int depth, size;
 119 } BN_STACK;
 120 static void BN_STACK_init(BN_STACK *);
 121 static void BN_STACK_finish(BN_STACK *);
 122 static int BN_STACK_push(BN_STACK *, unsigned int);
 123 static unsigned int BN_STACK_pop(BN_STACK *);
 124
 125 /**********/
 126 /* BN_CTX */
 127 /**********/
 128
 129 /* The opaque BN_CTX type */
 130 struct bignum_ctx {
 131     /* The bignum bundles */
 132     BN_POOL pool;
 133     /* The "stack frames", if you will */
 134     BN_STACK stack;
 135     /* The number of bignums currently assigned */
 136     unsigned int used;
 137     /* Depth of stack overflow */
 138     int err_stack;
 139     /* Block "gets" until an "end" (compatibility behaviour) */
 140     int too_many;
 141 };
 142
 143 /* Enable this to find BN_CTX bugs */
 144 #ifdef BN_CTX_DEBUG
 145 static const char *ctxdbg_cur = NULL;
 146 static void ctxdbg(BN_CTX *ctx)
 147 {
 148     unsigned int bnidx = 0, fpidx = 0;
 149     BN_POOL_ITEM *item = ctx->pool.head;
 150     BN_STACK *stack = &ctx->stack;
 151     fprintf(stderr, "(%16p): ", ctx);
 152     while (bnidx < ctx->used) {
 153         fprintf(stderr, "%03x ", item->vals[bnidx++ % BN_CTX_POOL_SIZE].dmax);
 154         if (!(bnidx % BN_CTX_POOL_SIZE))
 155             item = item->next;
 156     }
 157     fprintf(stderr, "\n");
 158     bnidx = 0;
 159     fprintf(stderr, "          : ");
 160     while (fpidx < stack->depth) {
 161         while (bnidx++ < stack->indexes[fpidx])
 162             fprintf(stderr, "    ");
 163         fprintf(stderr, "^^^ ");
 164         bnidx++;
 165         fpidx++;
 166     }
 167     fprintf(stderr, "\n");
 168 }
 169
 170 # define CTXDBG_ENTRY(str, ctx)  do { \
 171                                 ctxdbg_cur = (str); \
 172                                 fprintf(stderr,"Starting %s\n", ctxdbg_cur); \
 173                                 ctxdbg(ctx); \
 174                                 } while(0)
 175 # define CTXDBG_EXIT(ctx)        do { \
 176                                 fprintf(stderr,"Ending %s\n", ctxdbg_cur); \
 177                                 ctxdbg(ctx); \
 178                                 } while(0)
 179 # define CTXDBG_RET(ctx,ret)
 180 #else
 181 # define CTXDBG_ENTRY(str, ctx)
 182 # define CTXDBG_EXIT(ctx)
 183 # define CTXDBG_RET(ctx,ret)
 184 #endif
 185
 186
 187 BN_CTX *BN_CTX_new(void)
 188 {
 189     BN_CTX *ret = OPENSSL_malloc(sizeof(*ret));
 190     if (!ret) {
 191         BNerr(BN_F_BN_CTX_NEW, ERR_R_MALLOC_FAILURE);
 192         return NULL;
 193     }
 194     /* Initialise the structure */
 195     BN_POOL_init(&ret->pool);
 196     BN_STACK_init(&ret->stack);
 197     ret->used = 0;
 198     ret->err_stack = 0;
 199     ret->too_many = 0;
 200     return ret;
 201 }
 202
 203 void BN_CTX_free(BN_CTX *ctx)
 204 {
 205     if (ctx == NULL)
 206         return;
 207 #ifdef BN_CTX_DEBUG
 208     {
 209         BN_POOL_ITEM *pool = ctx->pool.head;
 210         fprintf(stderr, "BN_CTX_free, stack-size=%d, pool-bignums=%d\n",
 211                 ctx->stack.size, ctx->pool.size);
 212         fprintf(stderr, "dmaxs: ");
 213         while (pool) {
 214             unsigned loop = 0;
 215             while (loop < BN_CTX_POOL_SIZE)
 216                 fprintf(stderr, "%02x ", pool->vals[loop++].dmax);
 217             pool = pool->next;
 218         }
 219         fprintf(stderr, "\n");
 220     }
 221 #endif
 222     BN_STACK_finish(&ctx->stack);
 223     BN_POOL_finish(&ctx->pool);
 224     OPENSSL_free(ctx);
 225 }
 226
 227 void BN_CTX_start(BN_CTX *ctx)
 228 {
 229     CTXDBG_ENTRY("BN_CTX_start", ctx);
 230     /* If we're already overflowing ... */
 231     if (ctx->err_stack || ctx->too_many)
 232         ctx->err_stack++;
 233     /* (Try to) get a new frame pointer */
 234     else if (!BN_STACK_push(&ctx->stack, ctx->used)) {
 235         BNerr(BN_F_BN_CTX_START, BN_R_TOO_MANY_TEMPORARY_VARIABLES);
 236         ctx->err_stack++;
 237     }
 238     CTXDBG_EXIT(ctx);
 239 }
 240
 241 void BN_CTX_end(BN_CTX *ctx)
 242 {
 243     CTXDBG_ENTRY("BN_CTX_end", ctx);
 244     if (ctx->err_stack)
 245         ctx->err_stack--;
 246     else {
 247         unsigned int fp = BN_STACK_pop(&ctx->stack);
 248         /* Does this stack frame have anything to release? */
 249         if (fp < ctx->used)
 250             BN_POOL_release(&ctx->pool, ctx->used - fp);
 251         ctx->used = fp;
 252         /* Unjam "too_many" in case "get" had failed */
 253         ctx->too_many = 0;
 254     }
 255     CTXDBG_EXIT(ctx);
 256 }
 257
 258 BIGNUM *BN_CTX_get(BN_CTX *ctx)
 259 {
 260     BIGNUM *ret;
 261     CTXDBG_ENTRY("BN_CTX_get", ctx);
 262     if (ctx->err_stack || ctx->too_many)
 263         return NULL;
 264     if ((ret = BN_POOL_get(&ctx->pool)) == NULL) {
 265         /*
 266          * Setting too_many prevents repeated "get" attempts from cluttering
 267          * the error stack.
 268          */
 269         ctx->too_many = 1;
 270         BNerr(BN_F_BN_CTX_GET, BN_R_TOO_MANY_TEMPORARY_VARIABLES);
 271         return NULL;
 272     }
 273     /* OK, make sure the returned bignum is "zero" */
 274     BN_zero(ret);
 275     ctx->used++;
 276     CTXDBG_RET(ctx, ret);
 277     return ret;
 278 }
 279
 280 /************/
 281 /* BN_STACK */
 282 /************/
 283
 284 static void BN_STACK_init(BN_STACK *st)
 285 {
 286     st->indexes = NULL;
 287     st->depth = st->size = 0;
 288 }
 289
 290 static void BN_STACK_finish(BN_STACK *st)
 291 {
 292     if (st->size)
 293         OPENSSL_free(st->indexes);
 294 }
 295
 296
 297 static int BN_STACK_push(BN_STACK *st, unsigned int idx)
 298 {
 299     if (st->depth == st->size)
 300         /* Need to expand */
 301     {
 302         unsigned int newsize = (st->size ?
 303                                 (st->size * 3 / 2) : BN_CTX_START_FRAMES);
 304         unsigned int *newitems = OPENSSL_malloc(newsize *
 305                                                 sizeof(unsigned int));
 306         if (!newitems)
 307             return 0;
 308         if (st->depth)
 309             memcpy(newitems, st->indexes, st->depth * sizeof(unsigned int));
 310         if (st->size)
 311             OPENSSL_free(st->indexes);
 312         st->indexes = newitems;
 313         st->size = newsize;
 314     }
 315     st->indexes[(st->depth)++] = idx;
 316     return 1;
 317 }
 318
 319 static unsigned int BN_STACK_pop(BN_STACK *st)
 320 {
 321     return st->indexes[--(st->depth)];
 322 }
 323
 324 /***********/
 325 /* BN_POOL */
 326 /***********/
 327
 328 static void BN_POOL_init(BN_POOL *p)
 329 {
 330     p->head = p->current = p->tail = NULL;
 331     p->used = p->size = 0;
 332 }
 333
 334 static void BN_POOL_finish(BN_POOL *p)
 335 {
 336     while (p->head) {
 337         unsigned int loop = 0;
 338         BIGNUM *bn = p->head->vals;
 339         while (loop++ < BN_CTX_POOL_SIZE) {
 340             if (bn->d)
 341                 BN_clear_free(bn);
 342             bn++;
 343         }
 344         p->current = p->head->next;
 345         OPENSSL_free(p->head);
 346         p->head = p->current;
 347     }
 348 }
 349
 350
 351 static BIGNUM *BN_POOL_get(BN_POOL *p)
 352 {
 353     if (p->used == p->size) {
 354         BIGNUM *bn;
 355         unsigned int loop = 0;
 356         BN_POOL_ITEM *item = OPENSSL_malloc(sizeof(*item));
 357         if (!item)
 358             return NULL;
 359         /* Initialise the structure */
 360         bn = item->vals;
 361         while (loop++ < BN_CTX_POOL_SIZE)
 362             BN_init(bn++);
 363         item->prev = p->tail;
 364         item->next = NULL;
 365         /* Link it in */
 366         if (!p->head)
 367             p->head = p->current = p->tail = item;
 368         else {
 369             p->tail->next = item;
 370             p->tail = item;
 371             p->current = item;
 372         }
 373         p->size += BN_CTX_POOL_SIZE;
 374         p->used++;
 375         /* Return the first bignum from the new pool */
 376         return item->vals;
 377     }
 378     if (!p->used)
 379         p->current = p->head;
 380     else if ((p->used % BN_CTX_POOL_SIZE) == 0)
 381         p->current = p->current->next;
 382     return p->current->vals + ((p->used++) % BN_CTX_POOL_SIZE);
 383 }
 384
 385 static void BN_POOL_release(BN_POOL *p, unsigned int num)
 386 {
 387     unsigned int offset = (p->used - 1) % BN_CTX_POOL_SIZE;
 388     p->used -= num;
 389     while (num--) {
 390         bn_check_top(p->current->vals + offset);
 391         if (!offset) {
 392             offset = BN_CTX_POOL_SIZE - 1;
 393             p->current = p->current->prev;
 394         } else
 395             offset--;
 396     }
 397 }