xref: /freebsd/crypto/openssl/crypto/bn/bn_ctx.c (revision 39beb93c) 
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,"%02x ", 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 	}
454 
455