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 <stdio.h>
  64 #include <assert.h>
  65
  66 #include "cryptlib.h"
  67 #include "bn_lcl.h"
  68
  69 /*-
  70  * TODO list
  71  *
  72  * 1. Check a bunch of "(words+1)" type hacks in various bignum functions and
  73  * check they can be safely removed.
  74  *  - Check +1 and other ugliness in BN_from_montgomery()
  75  *
  76  * 2. Consider allowing a BN_new_ex() that, at least, lets you specify an
  77  * appropriate 'block' size that will be honoured by bn_expand_internal() to
  78  * prevent piddly little reallocations. OTOH, profiling bignum expansions in
  79  * BN_CTX doesn't show this to be a big issue.
  80  */
  81
  82 /* How many bignums are in each "pool item"; */
  83 #define BN_CTX_POOL_SIZE        16
  84 /* The stack frame info is resizing, set a first-time expansion size; */
  85 #define BN_CTX_START_FRAMES     32
  86
  87 /***********/
  88 /* BN_POOL */
  89 /***********/
  90
  91 /* A bundle of bignums that can be linked with other bundles */
  92 typedef struct bignum_pool_item
  93         {
  94         /* The bignum values */
  95         BIGNUM vals[BN_CTX_POOL_SIZE];
  96         /* Linked-list admin */
  97         struct bignum_pool_item *prev, *next;
  98         } BN_POOL_ITEM;
  99 /* A linked-list of bignums grouped in bundles */
 100 typedef struct bignum_pool
 101         {
 102         /* Linked-list admin */
 103         BN_POOL_ITEM *head, *current, *tail;
 104         /* Stack depth and allocation size */
 105         unsigned used, size;
 106         } BN_POOL;
 107 static void             BN_POOL_init(BN_POOL *);
 108 static void             BN_POOL_finish(BN_POOL *);
 109 #ifndef OPENSSL_NO_DEPRECATED
 110 static void             BN_POOL_reset(BN_POOL *);
 111 #endif
 112 static BIGNUM *         BN_POOL_get(BN_POOL *);
 113 static void             BN_POOL_release(BN_POOL *, unsigned int);
 114
 115 /************/
 116 /* BN_STACK */
 117 /************/
 118
 119 /* A wrapper to manage the "stack frames" */
 120 typedef struct bignum_ctx_stack
 121         {
 122         /* Array of indexes into the bignum stack */
 123         unsigned int *indexes;
 124         /* Number of stack frames, and the size of the allocated array */
 125         unsigned int depth, size;
 126         } BN_STACK;
 127 static void             BN_STACK_init(BN_STACK *);
 128 static void             BN_STACK_finish(BN_STACK *);
 129 #ifndef OPENSSL_NO_DEPRECATED
 130 static void             BN_STACK_reset(BN_STACK *);
 131 #endif
 132 static int              BN_STACK_push(BN_STACK *, unsigned int);
 133 static unsigned int     BN_STACK_pop(BN_STACK *);
 134
 135 /**********/
 136 /* BN_CTX */
 137 /**********/
 138
 139 /* The opaque BN_CTX type */
 140 struct bignum_ctx
 141         {
 142         /* The bignum bundles */
 143         BN_POOL pool;
 144         /* The "stack frames", if you will */
 145         BN_STACK stack;
 146         /* The number of bignums currently assigned */
 147         unsigned int used;
 148         /* Depth of stack overflow */
 149         int err_stack;
 150         /* Block "gets" until an "end" (compatibility behaviour) */
 151         int too_many;
 152         };
 153
 154 /* Enable this to find BN_CTX bugs */
 155 #ifdef BN_CTX_DEBUG
 156 static const char *ctxdbg_cur = NULL;
 157 static void ctxdbg(BN_CTX *ctx)
 158         {
 159         unsigned int bnidx = 0, fpidx = 0;
 160         BN_POOL_ITEM *item = ctx->pool.head;
 161         BN_STACK *stack = &ctx->stack;
 162         fprintf(stderr,"(%16p): ", ctx);
 163         while(bnidx < ctx->used)
 164                 {
 165                 fprintf(stderr,"%03x ", item->vals[bnidx++ % BN_CTX_POOL_SIZE].dmax);
 166                 if(!(bnidx % BN_CTX_POOL_SIZE))
 167                         item = item->next;
 168                 }
 169         fprintf(stderr,"\n");
 170         bnidx = 0;
 171         fprintf(stderr,"          : ");
 172         while(fpidx < stack->depth)
 173                 {
 174                 while(bnidx++ < stack->indexes[fpidx])
 175                         fprintf(stderr,"    ");
 176                 fprintf(stderr,"^^^ ");
 177                 bnidx++;
 178                 fpidx++;
 179                 }
 180         fprintf(stderr,"\n");
 181         }
 182 #define CTXDBG_ENTRY(str, ctx)  do { \
 183                                 ctxdbg_cur = (str); \
 184                                 fprintf(stderr,"Starting %s\n", ctxdbg_cur); \
 185                                 ctxdbg(ctx); \
 186                                 } while(0)
 187 #define CTXDBG_EXIT(ctx)        do { \
 188                                 fprintf(stderr,"Ending %s\n", ctxdbg_cur); \
 189                                 ctxdbg(ctx); \
 190                                 } while(0)
 191 #define CTXDBG_RET(ctx,ret)
 192 #else
 193 #define CTXDBG_ENTRY(str, ctx)
 194 #define CTXDBG_EXIT(ctx)
 195 #define CTXDBG_RET(ctx,ret)
 196 #endif
 197
 198 /* This function is an evil legacy and should not be used. This implementation
 199  * is WYSIWYG, though I've done my best. */
 200 #ifndef OPENSSL_NO_DEPRECATED
 201 void BN_CTX_init(BN_CTX *ctx)
 202         {
 203         /* Assume the caller obtained the context via BN_CTX_new() and so is
 204          * trying to reset it for use. Nothing else makes sense, least of all
 205          * binary compatibility from a time when they could declare a static
 206          * variable. */
 207         BN_POOL_reset(&ctx->pool);
 208         BN_STACK_reset(&ctx->stack);
 209         ctx->used = 0;
 210         ctx->err_stack = 0;
 211         ctx->too_many = 0;
 212         }
 213 #endif
 214
 215 BN_CTX *BN_CTX_new(void)
 216         {
 217         BN_CTX *ret = OPENSSL_malloc(sizeof(BN_CTX));
 218         if(!ret)
 219                 {
 220                 BNerr(BN_F_BN_CTX_NEW,ERR_R_MALLOC_FAILURE);
 221                 return NULL;
 222                 }
 223         /* Initialise the structure */
 224         BN_POOL_init(&ret->pool);
 225         BN_STACK_init(&ret->stack);
 226         ret->used = 0;
 227         ret->err_stack = 0;
 228         ret->too_many = 0;
 229         return ret;
 230         }
 231
 232 void BN_CTX_free(BN_CTX *ctx)
 233         {
 234         if (ctx == NULL)
 235                 return;
 236 #ifdef BN_CTX_DEBUG
 237         {
 238         BN_POOL_ITEM *pool = ctx->pool.head;
 239         fprintf(stderr,"BN_CTX_free, stack-size=%d, pool-bignums=%d\n",
 240                 ctx->stack.size, ctx->pool.size);
 241         fprintf(stderr,"dmaxs: ");
 242         while(pool) {
 243                 unsigned loop = 0;
 244                 while(loop < BN_CTX_POOL_SIZE)
 245                         fprintf(stderr,"%02x ", pool->vals[loop++].dmax);
 246                 pool = pool->next;
 247         }
 248         fprintf(stderr,"\n");
 249         }
 250 #endif
 251         BN_STACK_finish(&ctx->stack);
 252         BN_POOL_finish(&ctx->pool);
 253         OPENSSL_free(ctx);
 254         }
 255
 256 void BN_CTX_start(BN_CTX *ctx)
 257         {
 258         CTXDBG_ENTRY("BN_CTX_start", ctx);
 259         /* If we're already overflowing ... */
 260         if(ctx->err_stack || ctx->too_many)
 261                 ctx->err_stack++;
 262         /* (Try to) get a new frame pointer */
 263         else if(!BN_STACK_push(&ctx->stack, ctx->used))
 264                 {
 265                 BNerr(BN_F_BN_CTX_START,BN_R_TOO_MANY_TEMPORARY_VARIABLES);
 266                 ctx->err_stack++;
 267                 }
 268         CTXDBG_EXIT(ctx);
 269         }
 270
 271 void BN_CTX_end(BN_CTX *ctx)
 272         {
 273         CTXDBG_ENTRY("BN_CTX_end", ctx);
 274         if(ctx->err_stack)
 275                 ctx->err_stack--;
 276         else
 277                 {
 278                 unsigned int fp = BN_STACK_pop(&ctx->stack);
 279                 /* Does this stack frame have anything to release? */
 280                 if(fp < ctx->used)
 281                         BN_POOL_release(&ctx->pool, ctx->used - fp);
 282                 ctx->used = fp;
 283                 /* Unjam "too_many" in case "get" had failed */
 284                 ctx->too_many = 0;
 285                 }
 286         CTXDBG_EXIT(ctx);
 287         }
 288
 289 BIGNUM *BN_CTX_get(BN_CTX *ctx)
 290         {
 291         BIGNUM *ret;
 292         CTXDBG_ENTRY("BN_CTX_get", ctx);
 293         if(ctx->err_stack || ctx->too_many) return NULL;
 294         if((ret = BN_POOL_get(&ctx->pool)) == NULL)
 295                 {
 296                 /* Setting too_many prevents repeated "get" attempts from
 297                  * cluttering the error stack. */
 298                 ctx->too_many = 1;
 299                 BNerr(BN_F_BN_CTX_GET,BN_R_TOO_MANY_TEMPORARY_VARIABLES);
 300                 return NULL;
 301                 }
 302         /* OK, make sure the returned bignum is "zero" */
 303         BN_zero(ret);
 304         ctx->used++;
 305         CTXDBG_RET(ctx, ret);
 306         return ret;
 307         }
 308
 309 /************/
 310 /* BN_STACK */
 311 /************/
 312
 313 static void BN_STACK_init(BN_STACK *st)
 314         {
 315         st->indexes = NULL;
 316         st->depth = st->size = 0;
 317         }
 318
 319 static void BN_STACK_finish(BN_STACK *st)
 320         {
 321         if(st->size) OPENSSL_free(st->indexes);
 322         }
 323
 324 #ifndef OPENSSL_NO_DEPRECATED
 325 static void BN_STACK_reset(BN_STACK *st)
 326         {
 327         st->depth = 0;
 328         }
 329 #endif
 330
 331 static int BN_STACK_push(BN_STACK *st, unsigned int idx)
 332         {
 333         if(st->depth == st->size)
 334                 /* Need to expand */
 335                 {
 336                 unsigned int newsize = (st->size ?
 337                                 (st->size * 3 / 2) : BN_CTX_START_FRAMES);
 338                 unsigned int *newitems = OPENSSL_malloc(newsize *
 339                                                 sizeof(unsigned int));
 340                 if(!newitems) return 0;
 341                 if(st->depth)
 342                         memcpy(newitems, st->indexes, st->depth *
 343                                                 sizeof(unsigned int));
 344                 if(st->size) OPENSSL_free(st->indexes);
 345                 st->indexes = newitems;
 346                 st->size = newsize;
 347                 }
 348         st->indexes[(st->depth)++] = idx;
 349         return 1;
 350         }
 351
 352 static unsigned int BN_STACK_pop(BN_STACK *st)
 353         {
 354         return st->indexes[--(st->depth)];
 355         }
 356
 357 /***********/
 358 /* BN_POOL */
 359 /***********/
 360
 361 static void BN_POOL_init(BN_POOL *p)
 362         {
 363         p->head = p->current = p->tail = NULL;
 364         p->used = p->size = 0;
 365         }
 366
 367 static void BN_POOL_finish(BN_POOL *p)
 368         {
 369         while(p->head)
 370                 {
 371                 unsigned int loop = 0;
 372                 BIGNUM *bn = p->head->vals;
 373                 while(loop++ < BN_CTX_POOL_SIZE)
 374                         {
 375                         if(bn->d) BN_clear_free(bn);
 376                         bn++;
 377                         }
 378                 p->current = p->head->next;
 379                 OPENSSL_free(p->head);
 380                 p->head = p->current;
 381                 }
 382         }
 383
 384 #ifndef OPENSSL_NO_DEPRECATED
 385 static void BN_POOL_reset(BN_POOL *p)
 386         {
 387         BN_POOL_ITEM *item = p->head;
 388         while(item)
 389                 {
 390                 unsigned int loop = 0;
 391                 BIGNUM *bn = item->vals;
 392                 while(loop++ < BN_CTX_POOL_SIZE)
 393                         {
 394                         if(bn->d) BN_clear(bn);
 395                         bn++;
 396                         }
 397                 item = item->next;
 398                 }
 399         p->current = p->head;
 400         p->used = 0;
 401         }
 402 #endif
 403
 404 static BIGNUM *BN_POOL_get(BN_POOL *p)
 405         {
 406         if(p->used == p->size)
 407                 {
 408                 BIGNUM *bn;
 409                 unsigned int loop = 0;
 410                 BN_POOL_ITEM *item = OPENSSL_malloc(sizeof(BN_POOL_ITEM));
 411                 if(!item) return NULL;
 412                 /* Initialise the structure */
 413                 bn = item->vals;
 414                 while(loop++ < BN_CTX_POOL_SIZE)
 415                         BN_init(bn++);
 416                 item->prev = p->tail;
 417                 item->next = NULL;
 418                 /* Link it in */
 419                 if(!p->head)
 420                         p->head = p->current = p->tail = item;
 421                 else
 422                         {
 423                         p->tail->next = item;
 424                         p->tail = item;
 425                         p->current = item;
 426                         }
 427                 p->size += BN_CTX_POOL_SIZE;
 428                 p->used++;
 429                 /* Return the first bignum from the new pool */
 430                 return item->vals;
 431                 }
 432         if(!p->used)
 433                 p->current = p->head;
 434         else if((p->used % BN_CTX_POOL_SIZE) == 0)
 435                 p->current = p->current->next;
 436         return p->current->vals + ((p->used++) % BN_CTX_POOL_SIZE);
 437         }
 438
 439 static void BN_POOL_release(BN_POOL *p, unsigned int num)
 440         {
 441         unsigned int offset = (p->used - 1) % BN_CTX_POOL_SIZE;
 442         p->used -= num;
 443         while(num--)
 444                 {
 445                 bn_check_top(p->current->vals + offset);
 446                 if(!offset)
 447                         {
 448                         offset = BN_CTX_POOL_SIZE - 1;
 449                         p->current = p->current->prev;
 450                         }
 451                 else
 452                         offset--;
 453                 }
 454         }
 455