1 /* crypto/bn/bn_ctx.c */
2 /* Written by Ulf Moeller for the OpenSSL project. */
3 /* ====================================================================
4 * Copyright (c) 1998-2019 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 /* 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 /* Linked-list admin */
101 BN_POOL_ITEM *head, *current, *tail;
102 /* Stack depth and allocation size */
103 unsigned used, size;
104 } BN_POOL;
105 static void BN_POOL_init(BN_POOL *);
106 static void BN_POOL_finish(BN_POOL *);
107 #ifndef OPENSSL_NO_DEPRECATED
108 static void BN_POOL_reset(BN_POOL *);
109 #endif
110 static BIGNUM *BN_POOL_get(BN_POOL *);
111 static void BN_POOL_release(BN_POOL *, unsigned int);
112
113 /************/
114 /* BN_STACK */
115 /************/
116
117 /* A wrapper to manage the "stack frames" */
118 typedef struct bignum_ctx_stack {
119 /* Array of indexes into the bignum stack */
120 unsigned int *indexes;
121 /* Number of stack frames, and the size of the allocated array */
122 unsigned int depth, size;
123 } BN_STACK;
124 static void BN_STACK_init(BN_STACK *);
125 static void BN_STACK_finish(BN_STACK *);
126 #ifndef OPENSSL_NO_DEPRECATED
127 static void BN_STACK_reset(BN_STACK *);
128 #endif
129 static int BN_STACK_push(BN_STACK *, unsigned int);
130 static unsigned int BN_STACK_pop(BN_STACK *);
131
132 /**********/
133 /* BN_CTX */
134 /**********/
135
136 /* The opaque BN_CTX type */
137 struct bignum_ctx {
138 /* The bignum bundles */
139 BN_POOL pool;
140 /* The "stack frames", if you will */
141 BN_STACK stack;
142 /* The number of bignums currently assigned */
143 unsigned int used;
144 /* Depth of stack overflow */
145 int err_stack;
146 /* Block "gets" until an "end" (compatibility behaviour) */
147 int too_many;
148 };
149
150 /* Enable this to find BN_CTX bugs */
151 #ifdef BN_CTX_DEBUG
152 static const char *ctxdbg_cur = NULL;
ctxdbg(BN_CTX * ctx)153 static void ctxdbg(BN_CTX *ctx)
154 {
155 unsigned int bnidx = 0, fpidx = 0;
156 BN_POOL_ITEM *item = ctx->pool.head;
157 BN_STACK *stack = &ctx->stack;
158 fprintf(stderr, "(%16p): ", ctx);
159 while (bnidx < ctx->used) {
160 fprintf(stderr, "%03x ", item->vals[bnidx++ % BN_CTX_POOL_SIZE].dmax);
161 if (!(bnidx % BN_CTX_POOL_SIZE))
162 item = item->next;
163 }
164 fprintf(stderr, "\n");
165 bnidx = 0;
166 fprintf(stderr, " : ");
167 while (fpidx < stack->depth) {
168 while (bnidx++ < stack->indexes[fpidx])
169 fprintf(stderr, " ");
170 fprintf(stderr, "^^^ ");
171 bnidx++;
172 fpidx++;
173 }
174 fprintf(stderr, "\n");
175 }
176
177 # define CTXDBG_ENTRY(str, ctx) do { \
178 ctxdbg_cur = (str); \
179 fprintf(stderr,"Starting %s\n", ctxdbg_cur); \
180 ctxdbg(ctx); \
181 } while(0)
182 # define CTXDBG_EXIT(ctx) do { \
183 fprintf(stderr,"Ending %s\n", ctxdbg_cur); \
184 ctxdbg(ctx); \
185 } while(0)
186 # define CTXDBG_RET(ctx,ret)
187 #else
188 # define CTXDBG_ENTRY(str, ctx)
189 # define CTXDBG_EXIT(ctx)
190 # define CTXDBG_RET(ctx,ret)
191 #endif
192
193 /*
194 * This function is an evil legacy and should not be used. This
195 * implementation is WYSIWYG, though I've done my best.
196 */
197 #ifndef OPENSSL_NO_DEPRECATED
BN_CTX_init(BN_CTX * ctx)198 void BN_CTX_init(BN_CTX *ctx)
199 {
200 /*
201 * Assume the caller obtained the context via BN_CTX_new() and so is
202 * trying to reset it for use. Nothing else makes sense, least of all
203 * binary compatibility from a time when they could declare a static
204 * variable.
205 */
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
BN_CTX_new(void)214 BN_CTX *BN_CTX_new(void)
215 {
216 BN_CTX *ret = OPENSSL_malloc(sizeof(BN_CTX));
217 if (!ret) {
218 BNerr(BN_F_BN_CTX_NEW, ERR_R_MALLOC_FAILURE);
219 return NULL;
220 }
221 /* Initialise the structure */
222 BN_POOL_init(&ret->pool);
223 BN_STACK_init(&ret->stack);
224 ret->used = 0;
225 ret->err_stack = 0;
226 ret->too_many = 0;
227 return ret;
228 }
229
BN_CTX_free(BN_CTX * ctx)230 void BN_CTX_free(BN_CTX *ctx)
231 {
232 if (ctx == NULL)
233 return;
234 #ifdef BN_CTX_DEBUG
235 {
236 BN_POOL_ITEM *pool = ctx->pool.head;
237 fprintf(stderr, "BN_CTX_free, stack-size=%d, pool-bignums=%d\n",
238 ctx->stack.size, ctx->pool.size);
239 fprintf(stderr, "dmaxs: ");
240 while (pool) {
241 unsigned loop = 0;
242 while (loop < BN_CTX_POOL_SIZE)
243 fprintf(stderr, "%02x ", pool->vals[loop++].dmax);
244 pool = pool->next;
245 }
246 fprintf(stderr, "\n");
247 }
248 #endif
249 BN_STACK_finish(&ctx->stack);
250 BN_POOL_finish(&ctx->pool);
251 OPENSSL_free(ctx);
252 }
253
BN_CTX_start(BN_CTX * ctx)254 void BN_CTX_start(BN_CTX *ctx)
255 {
256 CTXDBG_ENTRY("BN_CTX_start", ctx);
257 /* If we're already overflowing ... */
258 if (ctx->err_stack || ctx->too_many)
259 ctx->err_stack++;
260 /* (Try to) get a new frame pointer */
261 else if (!BN_STACK_push(&ctx->stack, ctx->used)) {
262 BNerr(BN_F_BN_CTX_START, BN_R_TOO_MANY_TEMPORARY_VARIABLES);
263 ctx->err_stack++;
264 }
265 CTXDBG_EXIT(ctx);
266 }
267
BN_CTX_end(BN_CTX * ctx)268 void BN_CTX_end(BN_CTX *ctx)
269 {
270 CTXDBG_ENTRY("BN_CTX_end", ctx);
271 if (ctx->err_stack)
272 ctx->err_stack--;
273 else {
274 unsigned int fp = BN_STACK_pop(&ctx->stack);
275 /* Does this stack frame have anything to release? */
276 if (fp < ctx->used)
277 BN_POOL_release(&ctx->pool, ctx->used - fp);
278 ctx->used = fp;
279 /* Unjam "too_many" in case "get" had failed */
280 ctx->too_many = 0;
281 }
282 CTXDBG_EXIT(ctx);
283 }
284
BN_CTX_get(BN_CTX * ctx)285 BIGNUM *BN_CTX_get(BN_CTX *ctx)
286 {
287 BIGNUM *ret;
288 CTXDBG_ENTRY("BN_CTX_get", ctx);
289 if (ctx->err_stack || ctx->too_many)
290 return NULL;
291 if ((ret = BN_POOL_get(&ctx->pool)) == NULL) {
292 /*
293 * Setting too_many prevents repeated "get" attempts from cluttering
294 * the error stack.
295 */
296 ctx->too_many = 1;
297 BNerr(BN_F_BN_CTX_GET, BN_R_TOO_MANY_TEMPORARY_VARIABLES);
298 return NULL;
299 }
300 /* OK, make sure the returned bignum is "zero" */
301 BN_zero(ret);
302 /* clear BN_FLG_CONSTTIME if leaked from previous frames */
303 ret->flags &= (~BN_FLG_CONSTTIME);
304 ctx->used++;
305 CTXDBG_RET(ctx, ret);
306 return ret;
307 }
308
309 /************/
310 /* BN_STACK */
311 /************/
312
BN_STACK_init(BN_STACK * st)313 static void BN_STACK_init(BN_STACK *st)
314 {
315 st->indexes = NULL;
316 st->depth = st->size = 0;
317 }
318
BN_STACK_finish(BN_STACK * st)319 static void BN_STACK_finish(BN_STACK *st)
320 {
321 if (st->size)
322 OPENSSL_free(st->indexes);
323 }
324
325 #ifndef OPENSSL_NO_DEPRECATED
BN_STACK_reset(BN_STACK * st)326 static void BN_STACK_reset(BN_STACK *st)
327 {
328 st->depth = 0;
329 }
330 #endif
331
BN_STACK_push(BN_STACK * st,unsigned int idx)332 static int BN_STACK_push(BN_STACK *st, unsigned int idx)
333 {
334 if (st->depth == st->size)
335 /* Need to expand */
336 {
337 unsigned int newsize = (st->size ?
338 (st->size * 3 / 2) : BN_CTX_START_FRAMES);
339 unsigned int *newitems = OPENSSL_malloc(newsize *
340 sizeof(unsigned int));
341 if (!newitems)
342 return 0;
343 if (st->depth)
344 memcpy(newitems, st->indexes, st->depth * sizeof(unsigned int));
345 if (st->size)
346 OPENSSL_free(st->indexes);
347 st->indexes = newitems;
348 st->size = newsize;
349 }
350 st->indexes[(st->depth)++] = idx;
351 return 1;
352 }
353
BN_STACK_pop(BN_STACK * st)354 static unsigned int BN_STACK_pop(BN_STACK *st)
355 {
356 return st->indexes[--(st->depth)];
357 }
358
359 /***********/
360 /* BN_POOL */
361 /***********/
362
BN_POOL_init(BN_POOL * p)363 static void BN_POOL_init(BN_POOL *p)
364 {
365 p->head = p->current = p->tail = NULL;
366 p->used = p->size = 0;
367 }
368
BN_POOL_finish(BN_POOL * p)369 static void BN_POOL_finish(BN_POOL *p)
370 {
371 while (p->head) {
372 unsigned int loop = 0;
373 BIGNUM *bn = p->head->vals;
374 while (loop++ < BN_CTX_POOL_SIZE) {
375 if (bn->d)
376 BN_clear_free(bn);
377 bn++;
378 }
379 p->current = p->head->next;
380 OPENSSL_free(p->head);
381 p->head = p->current;
382 }
383 }
384
385 #ifndef OPENSSL_NO_DEPRECATED
BN_POOL_reset(BN_POOL * p)386 static void BN_POOL_reset(BN_POOL *p)
387 {
388 BN_POOL_ITEM *item = p->head;
389 while (item) {
390 unsigned int loop = 0;
391 BIGNUM *bn = item->vals;
392 while (loop++ < BN_CTX_POOL_SIZE) {
393 if (bn->d)
394 BN_clear(bn);
395 bn++;
396 }
397 item = item->next;
398 }
399 p->current = p->head;
400 p->used = 0;
401 }
402 #endif
403
BN_POOL_get(BN_POOL * p)404 static BIGNUM *BN_POOL_get(BN_POOL *p)
405 {
406 if (p->used == p->size) {
407 BIGNUM *bn;
408 unsigned int loop = 0;
409 BN_POOL_ITEM *item = OPENSSL_malloc(sizeof(BN_POOL_ITEM));
410 if (!item)
411 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 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
BN_POOL_release(BN_POOL * p,unsigned int num)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 bn_check_top(p->current->vals + offset);
444 if (!offset) {
445 offset = BN_CTX_POOL_SIZE - 1;
446 p->current = p->current->prev;
447 } else
448 offset--;
449 }
450 }
451