lib/libcrypto/bn/bn_ctx.c

   1 /* $OpenBSD: bn_ctx.c,v 1.15 2017/01/29 17:49:22 beck Exp $ */
   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 <string.h>
  65
  66 #include <openssl/opensslconf.h>
  67
  68 #include <openssl/err.h>
  69
  70 #include "bn_lcl.h"
  71
  72 /* TODO list
  73  *
  74  * 1. Check a bunch of "(words+1)" type hacks in various bignum functions and
  75  * check they can be safely removed.
  76  *  - Check +1 and other ugliness in BN_from_montgomery()
  77  *
  78  * 2. Consider allowing a BN_new_ex() that, at least, lets you specify an
  79  * appropriate 'block' size that will be honoured by bn_expand_internal() to
  80  * prevent piddly little reallocations. OTOH, profiling bignum expansions in
  81  * BN_CTX doesn't show this to be a big issue.
  82  */
  83
  84 /* How many bignums are in each "pool item"; */
  85 #define BN_CTX_POOL_SIZE        16
  86 /* The stack frame info is resizing, set a first-time expansion size; */
  87 #define BN_CTX_START_FRAMES     32
  88
  89 /***********/
  90 /* BN_POOL */
  91 /***********/
  92
  93 /* A bundle of bignums that can be linked with other bundles */
  94 typedef struct bignum_pool_item {
  95         /* The bignum values */
  96         BIGNUM vals[BN_CTX_POOL_SIZE];
  97         /* Linked-list admin */
  98         struct bignum_pool_item *prev, *next;
  99 } BN_POOL_ITEM;
 100
 101 /* A linked-list of bignums grouped in bundles */
 102 typedef struct bignum_pool {
 103         /* Linked-list admin */
 104         BN_POOL_ITEM *head, *current, *tail;
 105         /* Stack depth and allocation size */
 106         unsigned used, size;
 107 } BN_POOL;
 108
 109 static void             BN_POOL_init(BN_POOL *);
 110 static void             BN_POOL_finish(BN_POOL *);
 111 #ifndef OPENSSL_NO_DEPRECATED
 112 static void             BN_POOL_reset(BN_POOL *);
 113 #endif
 114 static BIGNUM *         BN_POOL_get(BN_POOL *);
 115 static void             BN_POOL_release(BN_POOL *, unsigned int);
 116
 117 /************/
 118 /* BN_STACK */
 119 /************/
 120
 121 /* A wrapper to manage the "stack frames" */
 122 typedef struct bignum_ctx_stack {
 123         /* Array of indexes into the bignum stack */
 124         unsigned int *indexes;
 125         /* Number of stack frames, and the size of the allocated array */
 126         unsigned int depth, size;
 127 } BN_STACK;
 128
 129 static void             BN_STACK_init(BN_STACK *);
 130 static void             BN_STACK_finish(BN_STACK *);
 131 #ifndef OPENSSL_NO_DEPRECATED
 132 static void             BN_STACK_reset(BN_STACK *);
 133 #endif
 134 static int              BN_STACK_push(BN_STACK *, unsigned int);
 135 static unsigned int     BN_STACK_pop(BN_STACK *);
 136
 137 /**********/
 138 /* BN_CTX */
 139 /**********/
 140
 141 /* The opaque BN_CTX type */
 142 struct bignum_ctx {
 143         /* The bignum bundles */
 144         BN_POOL pool;
 145         /* The "stack frames", if you will */
 146         BN_STACK stack;
 147         /* The number of bignums currently assigned */
 148         unsigned int used;
 149         /* Depth of stack overflow */
 150         int err_stack;
 151         /* Block "gets" until an "end" (compatibility behaviour) */
 152         int too_many;
 153 };
 154
 155 /* Enable this to find BN_CTX bugs */
 156 #ifdef BN_CTX_DEBUG
 157 static const char *ctxdbg_cur = NULL;
 158
 159 static void
 160 ctxdbg(BN_CTX *ctx)
 161 {
 162         unsigned int bnidx = 0, fpidx = 0;
 163         BN_POOL_ITEM *item = ctx->pool.head;
 164         BN_STACK *stack = &ctx->stack;
 165
 166         fprintf(stderr, "(%08x): ", (unsigned int)ctx);
 167         while (bnidx < ctx->used) {
 168                 fprintf(stderr, "%03x ",
 169                     item->vals[bnidx++ % BN_CTX_POOL_SIZE].dmax);
 170                 if (!(bnidx % BN_CTX_POOL_SIZE))
 171                         item = item->next;
 172         }
 173         fprintf(stderr, "\n");
 174         bnidx = 0;
 175         fprintf(stderr, "          : ");
 176         while (fpidx < stack->depth) {
 177                 while (bnidx++ < stack->indexes[fpidx])
 178                         fprintf(stderr, "    ");
 179                 fprintf(stderr, "^^^ ");
 180                 bnidx++;
 181                 fpidx++;
 182         }
 183         fprintf(stderr, "\n");
 184 }
 185 #define CTXDBG_ENTRY(str, ctx) \
 186         do { \
 187                 ctxdbg_cur = (str); \
 188                 fprintf(stderr, "Starting %s\n", ctxdbg_cur); \
 189                 ctxdbg(ctx); \
 190         } while(0)
 191
 192 #define CTXDBG_EXIT(ctx) \
 193         do { \
 194                 fprintf(stderr, "Ending %s\n", ctxdbg_cur); \
 195                 ctxdbg(ctx); \
 196         } while(0)
 197
 198 #define CTXDBG_RET(ctx,ret)
 199 #else
 200 #define CTXDBG_ENTRY(str, ctx)
 201 #define CTXDBG_EXIT(ctx)
 202 #define CTXDBG_RET(ctx,ret)
 203 #endif
 204
 205 /* This function is an evil legacy and should not be used. This implementation
 206  * is WYSIWYG, though I've done my best. */
 207 #ifndef OPENSSL_NO_DEPRECATED
 208 void
 209 BN_CTX_init(BN_CTX *ctx)
 210 {
 211         /* Assume the caller obtained the context via BN_CTX_new() and so is
 212          * trying to reset it for use. Nothing else makes sense, least of all
 213          * binary compatibility from a time when they could declare a static
 214          * variable. */
 215         BN_POOL_reset(&ctx->pool);
 216         BN_STACK_reset(&ctx->stack);
 217         ctx->used = 0;
 218         ctx->err_stack = 0;
 219         ctx->too_many = 0;
 220 }
 221 #endif
 222
 223 BN_CTX *
 224 BN_CTX_new(void)
 225 {
 226         BN_CTX *ret = malloc(sizeof(BN_CTX));
 227         if (!ret) {
 228                 BNerror(ERR_R_MALLOC_FAILURE);
 229                 return NULL;
 230         }
 231
 232         /* Initialise the structure */
 233         BN_POOL_init(&ret->pool);
 234         BN_STACK_init(&ret->stack);
 235         ret->used = 0;
 236         ret->err_stack = 0;
 237         ret->too_many = 0;
 238         return ret;
 239 }
 240
 241 void
 242 BN_CTX_free(BN_CTX *ctx)
 243 {
 244         if (ctx == NULL)
 245                 return;
 246 #ifdef BN_CTX_DEBUG
 247         {
 248                 BN_POOL_ITEM *pool = ctx->pool.head;
 249                 fprintf(stderr, "BN_CTX_free, stack-size=%d, pool-bignums=%d\n",
 250                     ctx->stack.size, ctx->pool.size);
 251                 fprintf(stderr, "dmaxs: ");
 252                 while (pool) {
 253                         unsigned loop = 0;
 254                         while (loop < BN_CTX_POOL_SIZE)
 255                                 fprintf(stderr, "%02x ",
 256                                     pool->vals[loop++].dmax);
 257                         pool = pool->next;
 258                 }
 259                 fprintf(stderr, "\n");
 260         }
 261 #endif
 262         BN_STACK_finish(&ctx->stack);
 263         BN_POOL_finish(&ctx->pool);
 264         free(ctx);
 265 }
 266
 267 void
 268 BN_CTX_start(BN_CTX *ctx)
 269 {
 270         CTXDBG_ENTRY("BN_CTX_start", ctx);
 271
 272         /* If we're already overflowing ... */
 273         if (ctx->err_stack || ctx->too_many)
 274                 ctx->err_stack++;
 275         /* (Try to) get a new frame pointer */
 276         else if (!BN_STACK_push(&ctx->stack, ctx->used)) {
 277                 BNerror(BN_R_TOO_MANY_TEMPORARY_VARIABLES);
 278                 ctx->err_stack++;
 279         }
 280         CTXDBG_EXIT(ctx);
 281 }
 282
 283 void
 284 BN_CTX_end(BN_CTX *ctx)
 285 {
 286         CTXDBG_ENTRY("BN_CTX_end", ctx);
 287
 288         if (ctx->err_stack)
 289                 ctx->err_stack--;
 290         else {
 291                 unsigned int fp = BN_STACK_pop(&ctx->stack);
 292                 /* Does this stack frame have anything to release? */
 293                 if (fp < ctx->used)
 294                         BN_POOL_release(&ctx->pool, ctx->used - fp);
 295                 ctx->used = fp;
 296                 /* Unjam "too_many" in case "get" had failed */
 297                 ctx->too_many = 0;
 298         }
 299         CTXDBG_EXIT(ctx);
 300 }
 301
 302 BIGNUM *
 303 BN_CTX_get(BN_CTX *ctx)
 304 {
 305         BIGNUM *ret;
 306
 307         CTXDBG_ENTRY("BN_CTX_get", ctx);
 308
 309         if (ctx->err_stack || ctx->too_many)
 310                 return NULL;
 311         if ((ret = BN_POOL_get(&ctx->pool)) == NULL) {
 312                 /* Setting too_many prevents repeated "get" attempts from
 313                  * cluttering the error stack. */
 314                 ctx->too_many = 1;
 315                 BNerror(BN_R_TOO_MANY_TEMPORARY_VARIABLES);
 316                 return NULL;
 317         }
 318         /* OK, make sure the returned bignum is "zero" */
 319         BN_zero(ret);
 320         ctx->used++;
 321         CTXDBG_RET(ctx, ret);
 322         return ret;
 323 }
 324
 325 /************/
 326 /* BN_STACK */
 327 /************/
 328
 329 static void
 330 BN_STACK_init(BN_STACK *st)
 331 {
 332         st->indexes = NULL;
 333         st->depth = st->size = 0;
 334 }
 335
 336 static void
 337 BN_STACK_finish(BN_STACK *st)
 338 {
 339         if (st->size)
 340                 free(st->indexes);
 341 }
 342
 343 #ifndef OPENSSL_NO_DEPRECATED
 344 static void
 345 BN_STACK_reset(BN_STACK *st)
 346 {
 347         st->depth = 0;
 348 }
 349 #endif
 350
 351 static int
 352 BN_STACK_push(BN_STACK *st, unsigned int idx)
 353 {
 354         if (st->depth == st->size)
 355                 /* Need to expand */
 356         {
 357                 unsigned int newsize = (st->size ?
 358                     (st->size * 3 / 2) : BN_CTX_START_FRAMES);
 359                 unsigned int *newitems = reallocarray(NULL,
 360                     newsize, sizeof(unsigned int));
 361                 if (!newitems)
 362                         return 0;
 363                 if (st->depth)
 364                         memcpy(newitems, st->indexes, st->depth *
 365                             sizeof(unsigned int));
 366                 if (st->size)
 367                         free(st->indexes);
 368                 st->indexes = newitems;
 369                 st->size = newsize;
 370         }
 371         st->indexes[(st->depth)++] = idx;
 372         return 1;
 373 }
 374
 375 static unsigned int
 376 BN_STACK_pop(BN_STACK *st)
 377 {
 378         return st->indexes[--(st->depth)];
 379 }
 380
 381 /***********/
 382 /* BN_POOL */
 383 /***********/
 384
 385 static void
 386 BN_POOL_init(BN_POOL *p)
 387 {
 388         p->head = p->current = p->tail = NULL;
 389         p->used = p->size = 0;
 390 }
 391
 392 static void
 393 BN_POOL_finish(BN_POOL *p)
 394 {
 395         while (p->head) {
 396                 unsigned int loop = 0;
 397                 BIGNUM *bn = p->head->vals;
 398                 while (loop++ < BN_CTX_POOL_SIZE) {
 399                         if (bn->d)
 400                                 BN_clear_free(bn);
 401                         bn++;
 402                 }
 403                 p->current = p->head->next;
 404                 free(p->head);
 405                 p->head = p->current;
 406         }
 407 }
 408
 409 #ifndef OPENSSL_NO_DEPRECATED
 410 static void
 411 BN_POOL_reset(BN_POOL *p)
 412 {
 413         BN_POOL_ITEM *item = p->head;
 414         while (item) {
 415                 unsigned int loop = 0;
 416                 BIGNUM *bn = item->vals;
 417                 while (loop++ < BN_CTX_POOL_SIZE) {
 418                         if (bn->d)
 419                                 BN_clear(bn);
 420                         bn++;
 421                 }
 422                 item = item->next;
 423         }
 424         p->current = p->head;
 425         p->used = 0;
 426 }
 427 #endif
 428
 429 static BIGNUM *
 430 BN_POOL_get(BN_POOL *p)
 431 {
 432         if (p->used == p->size) {
 433                 BIGNUM *bn;
 434                 unsigned int loop = 0;
 435                 BN_POOL_ITEM *item = malloc(sizeof(BN_POOL_ITEM));
 436                 if (!item)
 437                         return NULL;
 438                 /* Initialise the structure */
 439                 bn = item->vals;
 440                 while (loop++ < BN_CTX_POOL_SIZE)
 441                         BN_init(bn++);
 442                 item->prev = p->tail;
 443                 item->next = NULL;
 444                 /* Link it in */
 445                 if (!p->head)
 446                         p->head = p->current = p->tail = item;
 447                 else {
 448                         p->tail->next = item;
 449                         p->tail = item;
 450                         p->current = item;
 451                 }
 452                 p->size += BN_CTX_POOL_SIZE;
 453                 p->used++;
 454                 /* Return the first bignum from the new pool */
 455                 return item->vals;
 456         }
 457         if (!p->used)
 458                 p->current = p->head;
 459         else if ((p->used % BN_CTX_POOL_SIZE) == 0)
 460                 p->current = p->current->next;
 461         return p->current->vals + ((p->used++) % BN_CTX_POOL_SIZE);
 462 }
 463
 464 static void
 465 BN_POOL_release(BN_POOL *p, unsigned int num)
 466 {
 467         unsigned int offset = (p->used - 1) % BN_CTX_POOL_SIZE;
 468
 469         p->used -= num;
 470         while (num--) {
 471                 bn_check_top(p->current->vals + offset);
 472                 if (!offset) {
 473                         offset = BN_CTX_POOL_SIZE - 1;
 474                         p->current = p->current->prev;
 475                 } else
 476                         offset--;
 477         }
 478 }