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