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 #include <openssl/bn.h>
56
57 #include <string.h>
58
59 #include <openssl/err.h>
60 #include <openssl/mem.h>
61
62 #include "../../internal.h"
63
64
65 /* How many bignums are in each "pool item"; */
66 #define BN_CTX_POOL_SIZE 16
67 /* The stack frame info is resizing, set a first-time expansion size; */
68 #define BN_CTX_START_FRAMES 32
69
70 /* A bundle of bignums that can be linked with other bundles */
71 typedef struct bignum_pool_item {
72 /* The bignum values */
73 BIGNUM vals[BN_CTX_POOL_SIZE];
74 /* Linked-list admin */
75 struct bignum_pool_item *prev, *next;
76 } BN_POOL_ITEM;
77
78
79 typedef struct bignum_pool {
80 /* Linked-list admin */
81 BN_POOL_ITEM *head, *current, *tail;
82 /* Stack depth and allocation size */
83 unsigned used, size;
84 } BN_POOL;
85
86 static void BN_POOL_init(BN_POOL *);
87 static void BN_POOL_finish(BN_POOL *);
88 static BIGNUM *BN_POOL_get(BN_POOL *);
89 static void BN_POOL_release(BN_POOL *, unsigned int);
90
91 /************/
92 /* BN_STACK */
93 /************/
94
95 /* A wrapper to manage the "stack frames" */
96 typedef struct bignum_ctx_stack {
97 /* Array of indexes into the bignum stack */
98 unsigned int *indexes;
99 /* Number of stack frames, and the size of the allocated array */
100 unsigned int depth, size;
101 } BN_STACK;
102
103 static void BN_STACK_init(BN_STACK *);
104 static void BN_STACK_finish(BN_STACK *);
105 static int BN_STACK_push(BN_STACK *, unsigned int);
106 static unsigned int BN_STACK_pop(BN_STACK *);
107
108 /**********/
109 /* BN_CTX */
110 /**********/
111
112 /* The opaque BN_CTX type */
113 struct bignum_ctx {
114 /* The bignum bundles */
115 BN_POOL pool;
116 /* The "stack frames", if you will */
117 BN_STACK stack;
118 /* The number of bignums currently assigned */
119 unsigned int used;
120 /* Depth of stack overflow */
121 int err_stack;
122 /* Block "gets" until an "end" (compatibility behaviour) */
123 int too_many;
124 };
125
BN_CTX_new(void)126 BN_CTX *BN_CTX_new(void) {
127 BN_CTX *ret = OPENSSL_malloc(sizeof(BN_CTX));
128 if (!ret) {
129 OPENSSL_PUT_ERROR(BN, ERR_R_MALLOC_FAILURE);
130 return NULL;
131 }
132
133 /* Initialise the structure */
134 BN_POOL_init(&ret->pool);
135 BN_STACK_init(&ret->stack);
136 ret->used = 0;
137 ret->err_stack = 0;
138 ret->too_many = 0;
139 return ret;
140 }
141
BN_CTX_free(BN_CTX * ctx)142 void BN_CTX_free(BN_CTX *ctx) {
143 if (ctx == NULL) {
144 return;
145 }
146
147 BN_STACK_finish(&ctx->stack);
148 BN_POOL_finish(&ctx->pool);
149 OPENSSL_free(ctx);
150 }
151
BN_CTX_start(BN_CTX * ctx)152 void BN_CTX_start(BN_CTX *ctx) {
153 /* If we're already overflowing ... */
154 if (ctx->err_stack || ctx->too_many) {
155 ctx->err_stack++;
156 } else if (!BN_STACK_push(&ctx->stack, ctx->used)) {
157 /* (Try to) get a new frame pointer */
158 OPENSSL_PUT_ERROR(BN, BN_R_TOO_MANY_TEMPORARY_VARIABLES);
159 ctx->err_stack++;
160 }
161 }
162
BN_CTX_get(BN_CTX * ctx)163 BIGNUM *BN_CTX_get(BN_CTX *ctx) {
164 BIGNUM *ret;
165 if (ctx->err_stack || ctx->too_many) {
166 return NULL;
167 }
168
169 ret = BN_POOL_get(&ctx->pool);
170 if (ret == NULL) {
171 /* Setting too_many prevents repeated "get" attempts from
172 * cluttering the error stack. */
173 ctx->too_many = 1;
174 OPENSSL_PUT_ERROR(BN, BN_R_TOO_MANY_TEMPORARY_VARIABLES);
175 return NULL;
176 }
177
178 /* OK, make sure the returned bignum is "zero" */
179 BN_zero(ret);
180 ctx->used++;
181 return ret;
182 }
183
BN_CTX_end(BN_CTX * ctx)184 void BN_CTX_end(BN_CTX *ctx) {
185 if (ctx->err_stack) {
186 ctx->err_stack--;
187 } else {
188 unsigned int fp = BN_STACK_pop(&ctx->stack);
189 /* Does this stack frame have anything to release? */
190 if (fp < ctx->used) {
191 BN_POOL_release(&ctx->pool, ctx->used - fp);
192 }
193
194 ctx->used = fp;
195 /* Unjam "too_many" in case "get" had failed */
196 ctx->too_many = 0;
197 }
198 }
199
200 /************/
201 /* BN_STACK */
202 /************/
203
BN_STACK_init(BN_STACK * st)204 static void BN_STACK_init(BN_STACK *st) {
205 st->indexes = NULL;
206 st->depth = st->size = 0;
207 }
208
BN_STACK_finish(BN_STACK * st)209 static void BN_STACK_finish(BN_STACK *st) {
210 OPENSSL_free(st->indexes);
211 }
212
BN_STACK_push(BN_STACK * st,unsigned int idx)213 static int BN_STACK_push(BN_STACK *st, unsigned int idx) {
214 if (st->depth == st->size) {
215 /* Need to expand */
216 unsigned int newsize =
217 (st->size ? (st->size * 3 / 2) : BN_CTX_START_FRAMES);
218 unsigned int *newitems = OPENSSL_malloc(newsize * sizeof(unsigned int));
219 if (!newitems) {
220 return 0;
221 }
222 if (st->depth) {
223 OPENSSL_memcpy(newitems, st->indexes, st->depth * sizeof(unsigned int));
224 }
225 OPENSSL_free(st->indexes);
226 st->indexes = newitems;
227 st->size = newsize;
228 }
229
230 st->indexes[(st->depth)++] = idx;
231 return 1;
232 }
233
BN_STACK_pop(BN_STACK * st)234 static unsigned int BN_STACK_pop(BN_STACK *st) {
235 return st->indexes[--(st->depth)];
236 }
237
BN_POOL_init(BN_POOL * p)238 static void BN_POOL_init(BN_POOL *p) {
239 p->head = p->current = p->tail = NULL;
240 p->used = p->size = 0;
241 }
242
BN_POOL_finish(BN_POOL * p)243 static void BN_POOL_finish(BN_POOL *p) {
244 while (p->head) {
245 for (size_t i = 0; i < BN_CTX_POOL_SIZE; i++) {
246 BN_clear_free(&p->head->vals[i]);
247 }
248
249 p->current = p->head->next;
250 OPENSSL_free(p->head);
251 p->head = p->current;
252 }
253 }
254
BN_POOL_get(BN_POOL * p)255 static BIGNUM *BN_POOL_get(BN_POOL *p) {
256 if (p->used == p->size) {
257 BN_POOL_ITEM *item = OPENSSL_malloc(sizeof(BN_POOL_ITEM));
258 if (!item) {
259 return NULL;
260 }
261
262 /* Initialise the structure */
263 for (size_t i = 0; i < BN_CTX_POOL_SIZE; i++) {
264 BN_init(&item->vals[i]);
265 }
266
267 item->prev = p->tail;
268 item->next = NULL;
269 /* Link it in */
270 if (!p->head) {
271 p->head = p->current = p->tail = item;
272 } else {
273 p->tail->next = item;
274 p->tail = item;
275 p->current = item;
276 }
277
278 p->size += BN_CTX_POOL_SIZE;
279 p->used++;
280 /* Return the first bignum from the new pool */
281 return item->vals;
282 }
283
284 if (!p->used) {
285 p->current = p->head;
286 } else if ((p->used % BN_CTX_POOL_SIZE) == 0) {
287 p->current = p->current->next;
288 }
289
290 return p->current->vals + ((p->used++) % BN_CTX_POOL_SIZE);
291 }
292
BN_POOL_release(BN_POOL * p,unsigned int num)293 static void BN_POOL_release(BN_POOL *p, unsigned int num) {
294 unsigned int offset = (p->used - 1) % BN_CTX_POOL_SIZE;
295 p->used -= num;
296
297 while (num--) {
298 if (!offset) {
299 offset = BN_CTX_POOL_SIZE - 1;
300 p->current = p->current->prev;
301 } else {
302 offset--;
303 }
304 }
305 }
306