crypto/bn/bn_ctx.c

   1 /* Written by Ulf Moeller for the OpenSSL project. */
   2 /* ====================================================================
   3  * Copyright (c) 1998-2004 The OpenSSL Project.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  *
   9  * 1. Redistributions of source code must retain the above copyright
  10  *    notice, this list of conditions and the following disclaimer.
  11  *
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in
  14  *    the documentation and/or other materials provided with the
  15  *    distribution.
  16  *
  17  * 3. All advertising materials mentioning features or use of this
  18  *    software must display the following acknowledgment:
  19  *    "This product includes software developed by the OpenSSL Project
  20  *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
  21  *
  22  * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
  23  *    endorse or promote products derived from this software without
  24  *    prior written permission. For written permission, please contact
  25  *    openssl-core@openssl.org.
  26  *
  27  * 5. Products derived from this software may not be called "OpenSSL"
  28  *    nor may "OpenSSL" appear in their names without prior written
  29  *    permission of the OpenSSL Project.
  30  *
  31  * 6. Redistributions of any form whatsoever must retain the following
  32  *    acknowledgment:
  33  *    "This product includes software developed by the OpenSSL Project
  34  *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
  35  *
  36  * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
  37  * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  38  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  39  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
  40  * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  41  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  42  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  43  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  44  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  45  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  46  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
  47  * OF THE POSSIBILITY OF SUCH DAMAGE.
  48  * ====================================================================
  49  *
  50  * This product includes cryptographic software written by Eric Young
  51  * (eay@cryptsoft.com).  This product includes software written by Tim
  52  * Hudson (tjh@cryptsoft.com).
  53  *
  54  */
  55
  56 #include "internal/cryptlib.h"
  57 #include "bn_lcl.h"
  58
  59 /*-
  60  * TODO list
  61  *
  62  * 1. Check a bunch of "(words+1)" type hacks in various bignum functions and
  63  * check they can be safely removed.
  64  *  - Check +1 and other ugliness in BN_from_montgomery()
  65  *
  66  * 2. Consider allowing a BN_new_ex() that, at least, lets you specify an
  67  * appropriate 'block' size that will be honoured by bn_expand_internal() to
  68  * prevent piddly little reallocations. OTOH, profiling bignum expansions in
  69  * BN_CTX doesn't show this to be a big issue.
  70  */
  71
  72 /* How many bignums are in each "pool item"; */
  73 #define BN_CTX_POOL_SIZE        16
  74 /* The stack frame info is resizing, set a first-time expansion size; */
  75 #define BN_CTX_START_FRAMES     32
  76
  77 /***********/
  78 /* BN_POOL */
  79 /***********/
  80
  81 /* A bundle of bignums that can be linked with other bundles */
  82 typedef struct bignum_pool_item {
  83     /* The bignum values */
  84     BIGNUM vals[BN_CTX_POOL_SIZE];
  85     /* Linked-list admin */
  86     struct bignum_pool_item *prev, *next;
  87 } BN_POOL_ITEM;
  88 /* A linked-list of bignums grouped in bundles */
  89 typedef struct bignum_pool {
  90     /* Linked-list admin */
  91     BN_POOL_ITEM *head, *current, *tail;
  92     /* Stack depth and allocation size */
  93     unsigned used, size;
  94 } BN_POOL;
  95 static void BN_POOL_init(BN_POOL *);
  96 static void BN_POOL_finish(BN_POOL *);
  97 static BIGNUM *BN_POOL_get(BN_POOL *, int);
  98 static void BN_POOL_release(BN_POOL *, unsigned int);
  99
 100 /************/
 101 /* BN_STACK */
 102 /************/
 103
 104 /* A wrapper to manage the "stack frames" */
 105 typedef struct bignum_ctx_stack {
 106     /* Array of indexes into the bignum stack */
 107     unsigned int *indexes;
 108     /* Number of stack frames, and the size of the allocated array */
 109     unsigned int depth, size;
 110 } BN_STACK;
 111 static void BN_STACK_init(BN_STACK *);
 112 static void BN_STACK_finish(BN_STACK *);
 113 static int BN_STACK_push(BN_STACK *, unsigned int);
 114 static unsigned int BN_STACK_pop(BN_STACK *);
 115
 116 /**********/
 117 /* BN_CTX */
 118 /**********/
 119
 120 /* The opaque BN_CTX type */
 121 struct bignum_ctx {
 122     /* The bignum bundles */
 123     BN_POOL pool;
 124     /* The "stack frames", if you will */
 125     BN_STACK stack;
 126     /* The number of bignums currently assigned */
 127     unsigned int used;
 128     /* Depth of stack overflow */
 129     int err_stack;
 130     /* Block "gets" until an "end" (compatibility behaviour) */
 131     int too_many;
 132     /* Flags. */
 133     int flags;
 134 };
 135
 136 /* Enable this to find BN_CTX bugs */
 137 #ifdef BN_CTX_DEBUG
 138 static const char *ctxdbg_cur = NULL;
 139 static void ctxdbg(BN_CTX *ctx)
 140 {
 141     unsigned int bnidx = 0, fpidx = 0;
 142     BN_POOL_ITEM *item = ctx->pool.head;
 143     BN_STACK *stack = &ctx->stack;
 144     fprintf(stderr, "(%16p): ", ctx);
 145     while (bnidx < ctx->used) {
 146         fprintf(stderr, "%03x ", item->vals[bnidx++ % BN_CTX_POOL_SIZE].dmax);
 147         if (!(bnidx % BN_CTX_POOL_SIZE))
 148             item = item->next;
 149     }
 150     fprintf(stderr, "\n");
 151     bnidx = 0;
 152     fprintf(stderr, "          : ");
 153     while (fpidx < stack->depth) {
 154         while (bnidx++ < stack->indexes[fpidx])
 155             fprintf(stderr, "    ");
 156         fprintf(stderr, "^^^ ");
 157         bnidx++;
 158         fpidx++;
 159     }
 160     fprintf(stderr, "\n");
 161 }
 162
 163 # define CTXDBG_ENTRY(str, ctx)  do { \
 164                                 ctxdbg_cur = (str); \
 165                                 fprintf(stderr,"Starting %s\n", ctxdbg_cur); \
 166                                 ctxdbg(ctx); \
 167                                 } while(0)
 168 # define CTXDBG_EXIT(ctx)        do { \
 169                                 fprintf(stderr,"Ending %s\n", ctxdbg_cur); \
 170                                 ctxdbg(ctx); \
 171                                 } while(0)
 172 # define CTXDBG_RET(ctx,ret)
 173 #else
 174 # define CTXDBG_ENTRY(str, ctx)
 175 # define CTXDBG_EXIT(ctx)
 176 # define CTXDBG_RET(ctx,ret)
 177 #endif
 178
 179
 180 BN_CTX *BN_CTX_new(void)
 181 {
 182     BN_CTX *ret;
 183
 184     if ((ret = OPENSSL_zalloc(sizeof(*ret))) == NULL) {
 185         BNerr(BN_F_BN_CTX_NEW, ERR_R_MALLOC_FAILURE);
 186         return NULL;
 187     }
 188     /* Initialise the structure */
 189     BN_POOL_init(&ret->pool);
 190     BN_STACK_init(&ret->stack);
 191     return ret;
 192 }
 193
 194 BN_CTX *BN_CTX_secure_new(void)
 195 {
 196     BN_CTX *ret = BN_CTX_new();
 197
 198     if (ret != NULL)
 199         ret->flags = BN_FLG_SECURE;
 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
 262     CTXDBG_ENTRY("BN_CTX_get", ctx);
 263     if (ctx->err_stack || ctx->too_many)
 264         return NULL;
 265     if ((ret = BN_POOL_get(&ctx->pool, ctx->flags)) == NULL) {
 266         /*
 267          * Setting too_many prevents repeated "get" attempts from cluttering
 268          * the error stack.
 269          */
 270         ctx->too_many = 1;
 271         BNerr(BN_F_BN_CTX_GET, BN_R_TOO_MANY_TEMPORARY_VARIABLES);
 272         return NULL;
 273     }
 274     /* OK, make sure the returned bignum is "zero" */
 275     BN_zero(ret);
 276     ctx->used++;
 277     CTXDBG_RET(ctx, ret);
 278     return ret;
 279 }
 280
 281 /************/
 282 /* BN_STACK */
 283 /************/
 284
 285 static void BN_STACK_init(BN_STACK *st)
 286 {
 287     st->indexes = NULL;
 288     st->depth = st->size = 0;
 289 }
 290
 291 static void BN_STACK_finish(BN_STACK *st)
 292 {
 293     OPENSSL_free(st->indexes);
 294     st->indexes = NULL;
 295 }
 296
 297
 298 static int BN_STACK_push(BN_STACK *st, unsigned int idx)
 299 {
 300     if (st->depth == st->size) {
 301         /* Need to expand */
 302         unsigned int newsize =
 303             st->size ? (st->size * 3 / 2) : BN_CTX_START_FRAMES;
 304         unsigned int *newitems = OPENSSL_malloc(sizeof(*newitems) * newsize);
 305         if (newitems == NULL)
 306             return 0;
 307         if (st->depth)
 308             memcpy(newitems, st->indexes, sizeof(*newitems) * st->depth);
 309         OPENSSL_free(st->indexes);
 310         st->indexes = newitems;
 311         st->size = newsize;
 312     }
 313     st->indexes[(st->depth)++] = idx;
 314     return 1;
 315 }
 316
 317 static unsigned int BN_STACK_pop(BN_STACK *st)
 318 {
 319     return st->indexes[--(st->depth)];
 320 }
 321
 322 /***********/
 323 /* BN_POOL */
 324 /***********/
 325
 326 static void BN_POOL_init(BN_POOL *p)
 327 {
 328     p->head = p->current = p->tail = NULL;
 329     p->used = p->size = 0;
 330 }
 331
 332 static void BN_POOL_finish(BN_POOL *p)
 333 {
 334     unsigned int loop;
 335     BIGNUM *bn;
 336
 337     while (p->head) {
 338         for (loop = 0, bn = p->head->vals; loop++ < BN_CTX_POOL_SIZE; bn++)
 339             if (bn->d)
 340                 BN_clear_free(bn);
 341         p->current = p->head->next;
 342         OPENSSL_free(p->head);
 343         p->head = p->current;
 344     }
 345 }
 346
 347
 348 static BIGNUM *BN_POOL_get(BN_POOL *p, int flag)
 349 {
 350     BIGNUM *bn;
 351     unsigned int loop;
 352
 353     /* Full; allocate a new pool item and link it in. */
 354     if (p->used == p->size) {
 355         BN_POOL_ITEM *item = OPENSSL_malloc(sizeof(*item));
 356         if (item == NULL)
 357             return NULL;
 358         for (loop = 0, bn = item->vals; loop++ < BN_CTX_POOL_SIZE; bn++) {
 359             bn_init(bn);
 360             if ((flag & BN_FLG_SECURE) != 0)
 361                 BN_set_flags(bn, BN_FLG_SECURE);
 362         }
 363         item->prev = p->tail;
 364         item->next = NULL;
 365
 366         if (p->head == NULL)
 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
 379     if (!p->used)
 380         p->current = p->head;
 381     else if ((p->used % BN_CTX_POOL_SIZE) == 0)
 382         p->current = p->current->next;
 383     return p->current->vals + ((p->used++) % BN_CTX_POOL_SIZE);
 384 }
 385
 386 static void BN_POOL_release(BN_POOL *p, unsigned int num)
 387 {
 388     unsigned int offset = (p->used - 1) % BN_CTX_POOL_SIZE;
 389
 390     p->used -= num;
 391     while (num--) {
 392         bn_check_top(p->current->vals + offset);
 393         if (offset == 0) {
 394             offset = BN_CTX_POOL_SIZE - 1;
 395             p->current = p->current->prev;
 396         } else
 397             offset--;
 398     }
 399 }