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 
63 /* How many bignums are in each "pool item"; */
64 #define BN_CTX_POOL_SIZE 16
65 /* The stack frame info is resizing, set a first-time expansion size; */
66 #define BN_CTX_START_FRAMES 32
67 
68 /* A bundle of bignums that can be linked with other bundles */
69 typedef struct bignum_pool_item {
70   /* The bignum values */
71   BIGNUM vals[BN_CTX_POOL_SIZE];
72   /* Linked-list admin */
73   struct bignum_pool_item *prev, *next;
74 } BN_POOL_ITEM;
75 
76 
77 typedef struct bignum_pool {
78   /* Linked-list admin */
79   BN_POOL_ITEM *head, *current, *tail;
80   /* Stack depth and allocation size */
81   unsigned used, size;
82 } BN_POOL;
83 
84 static void BN_POOL_init(BN_POOL *);
85 static void BN_POOL_finish(BN_POOL *);
86 static BIGNUM *BN_POOL_get(BN_POOL *);
87 static void BN_POOL_release(BN_POOL *, unsigned int);
88 
89 /************/
90 /* BN_STACK */
91 /************/
92 
93 /* A wrapper to manage the "stack frames" */
94 typedef struct bignum_ctx_stack {
95   /* Array of indexes into the bignum stack */
96   unsigned int *indexes;
97   /* Number of stack frames, and the size of the allocated array */
98   unsigned int depth, size;
99 } BN_STACK;
100 
101 static void		BN_STACK_init(BN_STACK *);
102 static void		BN_STACK_finish(BN_STACK *);
103 static int		BN_STACK_push(BN_STACK *, unsigned int);
104 static unsigned int	BN_STACK_pop(BN_STACK *);
105 
106 /**********/
107 /* BN_CTX */
108 /**********/
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 /************/
201 
BN_STACK_init(BN_STACK * st)202 static void BN_STACK_init(BN_STACK *st) {
203   st->indexes = NULL;
204   st->depth = st->size = 0;
205 }
206 
BN_STACK_finish(BN_STACK * st)207 static void BN_STACK_finish(BN_STACK *st) {
208   OPENSSL_free(st->indexes);
209 }
210 
BN_STACK_push(BN_STACK * st,unsigned int idx)211 static int BN_STACK_push(BN_STACK *st, unsigned int idx) {
212   if (st->depth == st->size) {
213     /* Need to expand */
214     unsigned int newsize =
215         (st->size ? (st->size * 3 / 2) : BN_CTX_START_FRAMES);
216     unsigned int *newitems = OPENSSL_malloc(newsize * sizeof(unsigned int));
217     if (!newitems) {
218       return 0;
219     }
220     if (st->depth) {
221       memcpy(newitems, st->indexes, st->depth * sizeof(unsigned int));
222     }
223     OPENSSL_free(st->indexes);
224     st->indexes = newitems;
225     st->size = newsize;
226   }
227 
228   st->indexes[(st->depth)++] = idx;
229   return 1;
230 }
231 
BN_STACK_pop(BN_STACK * st)232 static unsigned int BN_STACK_pop(BN_STACK *st) {
233   return st->indexes[--(st->depth)];
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     unsigned int loop = 0;
244     BIGNUM *bn = p->head->vals;
245     while (loop++ < BN_CTX_POOL_SIZE) {
246       if (bn->d) {
247         BN_clear_free(bn);
248       }
249       bn++;
250     }
251 
252     p->current = p->head->next;
253     OPENSSL_free(p->head);
254     p->head = p->current;
255   }
256 }
257 
BN_POOL_get(BN_POOL * p)258 static BIGNUM *BN_POOL_get(BN_POOL *p) {
259   if (p->used == p->size) {
260     BIGNUM *bn;
261     unsigned int loop = 0;
262     BN_POOL_ITEM *item = OPENSSL_malloc(sizeof(BN_POOL_ITEM));
263     if (!item) {
264       return NULL;
265     }
266 
267     /* Initialise the structure */
268     bn = item->vals;
269     while (loop++ < BN_CTX_POOL_SIZE) {
270       BN_init(bn++);
271     }
272 
273     item->prev = p->tail;
274     item->next = NULL;
275     /* Link it in */
276     if (!p->head) {
277       p->head = p->current = p->tail = item;
278     } else {
279       p->tail->next = item;
280       p->tail = item;
281       p->current = item;
282     }
283 
284     p->size += BN_CTX_POOL_SIZE;
285     p->used++;
286     /* Return the first bignum from the new pool */
287     return item->vals;
288   }
289 
290   if (!p->used) {
291     p->current = p->head;
292   } else if ((p->used % BN_CTX_POOL_SIZE) == 0) {
293     p->current = p->current->next;
294   }
295 
296   return p->current->vals + ((p->used++) % BN_CTX_POOL_SIZE);
297 }
298 
BN_POOL_release(BN_POOL * p,unsigned int num)299 static void BN_POOL_release(BN_POOL *p, unsigned int num) {
300   unsigned int offset = (p->used - 1) % BN_CTX_POOL_SIZE;
301   p->used -= num;
302 
303   while (num--) {
304     if (!offset) {
305       offset = BN_CTX_POOL_SIZE - 1;
306       p->current = p->current->prev;
307     } else {
308       offset--;
309     }
310   }
311 }
312