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