1 /*
2 * Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.
3 *
4 * Licensed under the Apache License 2.0 (the "License"). You may not use
5 * this file except in compliance with the License. You can obtain a copy
6 * in the file LICENSE in the source distribution or at
7 * https://www.openssl.org/source/license.html
8 */
9
10 #include <openssl/trace.h>
11 #include "internal/cryptlib.h"
12 #include "bn_local.h"
13
14 /* How many bignums are in each "pool item"; */
15 #define BN_CTX_POOL_SIZE 16
16 /* The stack frame info is resizing, set a first-time expansion size; */
17 #define BN_CTX_START_FRAMES 32
18
19 /***********/
20 /* BN_POOL */
21 /***********/
22
23 /* A bundle of bignums that can be linked with other bundles */
24 typedef struct bignum_pool_item {
25 /* The bignum values */
26 BIGNUM vals[BN_CTX_POOL_SIZE];
27 /* Linked-list admin */
28 struct bignum_pool_item *prev, *next;
29 } BN_POOL_ITEM;
30 /* A linked-list of bignums grouped in bundles */
31 typedef struct bignum_pool {
32 /* Linked-list admin */
33 BN_POOL_ITEM *head, *current, *tail;
34 /* Stack depth and allocation size */
35 unsigned used, size;
36 } BN_POOL;
37 static void BN_POOL_init(BN_POOL *);
38 static void BN_POOL_finish(BN_POOL *);
39 static BIGNUM *BN_POOL_get(BN_POOL *, int);
40 static void BN_POOL_release(BN_POOL *, unsigned int);
41
42 /************/
43 /* BN_STACK */
44 /************/
45
46 /* A wrapper to manage the "stack frames" */
47 typedef struct bignum_ctx_stack {
48 /* Array of indexes into the bignum stack */
49 unsigned int *indexes;
50 /* Number of stack frames, and the size of the allocated array */
51 unsigned int depth, size;
52 } BN_STACK;
53 static void BN_STACK_init(BN_STACK *);
54 static void BN_STACK_finish(BN_STACK *);
55 static int BN_STACK_push(BN_STACK *, unsigned int);
56 static unsigned int BN_STACK_pop(BN_STACK *);
57
58 /**********/
59 /* BN_CTX */
60 /**********/
61
62 /* The opaque BN_CTX type */
63 struct bignum_ctx {
64 /* The bignum bundles */
65 BN_POOL pool;
66 /* The "stack frames", if you will */
67 BN_STACK stack;
68 /* The number of bignums currently assigned */
69 unsigned int used;
70 /* Depth of stack overflow */
71 int err_stack;
72 /* Block "gets" until an "end" (compatibility behaviour) */
73 int too_many;
74 /* Flags. */
75 int flags;
76 /* The library context */
77 OSSL_LIB_CTX *libctx;
78 };
79
80 #ifndef FIPS_MODULE
81 /* Debugging functionality */
ctxdbg(BIO * channel,const char * text,BN_CTX * ctx)82 static void ctxdbg(BIO *channel, const char *text, BN_CTX *ctx)
83 {
84 unsigned int bnidx = 0, fpidx = 0;
85 BN_POOL_ITEM *item = ctx->pool.head;
86 BN_STACK *stack = &ctx->stack;
87
88 BIO_printf(channel, "%s\n", text);
89 BIO_printf(channel, " (%16p): ", (void*)ctx);
90 while (bnidx < ctx->used) {
91 BIO_printf(channel, "%03x ",
92 item->vals[bnidx++ % BN_CTX_POOL_SIZE].dmax);
93 if (!(bnidx % BN_CTX_POOL_SIZE))
94 item = item->next;
95 }
96 BIO_printf(channel, "\n");
97 bnidx = 0;
98 BIO_printf(channel, " %16s : ", "");
99 while (fpidx < stack->depth) {
100 while (bnidx++ < stack->indexes[fpidx])
101 BIO_printf(channel, " ");
102 BIO_printf(channel, "^^^ ");
103 bnidx++;
104 fpidx++;
105 }
106 BIO_printf(channel, "\n");
107 }
108
109 # define CTXDBG(str, ctx) \
110 OSSL_TRACE_BEGIN(BN_CTX) { \
111 ctxdbg(trc_out, str, ctx); \
112 } OSSL_TRACE_END(BN_CTX)
113 #else
114 /* We do not want tracing in FIPS module */
115 # define CTXDBG(str, ctx) do {} while(0)
116 #endif /* FIPS_MODULE */
117
BN_CTX_new_ex(OSSL_LIB_CTX * ctx)118 BN_CTX *BN_CTX_new_ex(OSSL_LIB_CTX *ctx)
119 {
120 BN_CTX *ret;
121
122 if ((ret = OPENSSL_zalloc(sizeof(*ret))) == NULL) {
123 ERR_raise(ERR_LIB_BN, ERR_R_MALLOC_FAILURE);
124 return NULL;
125 }
126 /* Initialise the structure */
127 BN_POOL_init(&ret->pool);
128 BN_STACK_init(&ret->stack);
129 ret->libctx = ctx;
130 return ret;
131 }
132
133 #ifndef FIPS_MODULE
BN_CTX_new(void)134 BN_CTX *BN_CTX_new(void)
135 {
136 return BN_CTX_new_ex(NULL);
137 }
138 #endif
139
BN_CTX_secure_new_ex(OSSL_LIB_CTX * ctx)140 BN_CTX *BN_CTX_secure_new_ex(OSSL_LIB_CTX *ctx)
141 {
142 BN_CTX *ret = BN_CTX_new_ex(ctx);
143
144 if (ret != NULL)
145 ret->flags = BN_FLG_SECURE;
146 return ret;
147 }
148
149 #ifndef FIPS_MODULE
BN_CTX_secure_new(void)150 BN_CTX *BN_CTX_secure_new(void)
151 {
152 return BN_CTX_secure_new_ex(NULL);
153 }
154 #endif
155
BN_CTX_free(BN_CTX * ctx)156 void BN_CTX_free(BN_CTX *ctx)
157 {
158 if (ctx == NULL)
159 return;
160 #ifndef FIPS_MODULE
161 OSSL_TRACE_BEGIN(BN_CTX) {
162 BN_POOL_ITEM *pool = ctx->pool.head;
163 BIO_printf(trc_out,
164 "BN_CTX_free(): stack-size=%d, pool-bignums=%d\n",
165 ctx->stack.size, ctx->pool.size);
166 BIO_printf(trc_out, " dmaxs: ");
167 while (pool) {
168 unsigned loop = 0;
169 while (loop < BN_CTX_POOL_SIZE)
170 BIO_printf(trc_out, "%02x ", pool->vals[loop++].dmax);
171 pool = pool->next;
172 }
173 BIO_printf(trc_out, "\n");
174 } OSSL_TRACE_END(BN_CTX);
175 #endif
176 BN_STACK_finish(&ctx->stack);
177 BN_POOL_finish(&ctx->pool);
178 OPENSSL_free(ctx);
179 }
180
BN_CTX_start(BN_CTX * ctx)181 void BN_CTX_start(BN_CTX *ctx)
182 {
183 CTXDBG("ENTER BN_CTX_start()", ctx);
184 /* If we're already overflowing ... */
185 if (ctx->err_stack || ctx->too_many)
186 ctx->err_stack++;
187 /* (Try to) get a new frame pointer */
188 else if (!BN_STACK_push(&ctx->stack, ctx->used)) {
189 ERR_raise(ERR_LIB_BN, BN_R_TOO_MANY_TEMPORARY_VARIABLES);
190 ctx->err_stack++;
191 }
192 CTXDBG("LEAVE BN_CTX_start()", ctx);
193 }
194
BN_CTX_end(BN_CTX * ctx)195 void BN_CTX_end(BN_CTX *ctx)
196 {
197 if (ctx == NULL)
198 return;
199 CTXDBG("ENTER BN_CTX_end()", ctx);
200 if (ctx->err_stack)
201 ctx->err_stack--;
202 else {
203 unsigned int fp = BN_STACK_pop(&ctx->stack);
204 /* Does this stack frame have anything to release? */
205 if (fp < ctx->used)
206 BN_POOL_release(&ctx->pool, ctx->used - fp);
207 ctx->used = fp;
208 /* Unjam "too_many" in case "get" had failed */
209 ctx->too_many = 0;
210 }
211 CTXDBG("LEAVE BN_CTX_end()", ctx);
212 }
213
BN_CTX_get(BN_CTX * ctx)214 BIGNUM *BN_CTX_get(BN_CTX *ctx)
215 {
216 BIGNUM *ret;
217
218 CTXDBG("ENTER BN_CTX_get()", ctx);
219 if (ctx->err_stack || ctx->too_many)
220 return NULL;
221 if ((ret = BN_POOL_get(&ctx->pool, ctx->flags)) == NULL) {
222 /*
223 * Setting too_many prevents repeated "get" attempts from cluttering
224 * the error stack.
225 */
226 ctx->too_many = 1;
227 ERR_raise(ERR_LIB_BN, BN_R_TOO_MANY_TEMPORARY_VARIABLES);
228 return NULL;
229 }
230 /* OK, make sure the returned bignum is "zero" */
231 BN_zero(ret);
232 /* clear BN_FLG_CONSTTIME if leaked from previous frames */
233 ret->flags &= (~BN_FLG_CONSTTIME);
234 ctx->used++;
235 CTXDBG("LEAVE BN_CTX_get()", ctx);
236 return ret;
237 }
238
ossl_bn_get_libctx(BN_CTX * ctx)239 OSSL_LIB_CTX *ossl_bn_get_libctx(BN_CTX *ctx)
240 {
241 if (ctx == NULL)
242 return NULL;
243 return ctx->libctx;
244 }
245
246 /************/
247 /* BN_STACK */
248 /************/
249
BN_STACK_init(BN_STACK * st)250 static void BN_STACK_init(BN_STACK *st)
251 {
252 st->indexes = NULL;
253 st->depth = st->size = 0;
254 }
255
BN_STACK_finish(BN_STACK * st)256 static void BN_STACK_finish(BN_STACK *st)
257 {
258 OPENSSL_free(st->indexes);
259 st->indexes = NULL;
260 }
261
262
BN_STACK_push(BN_STACK * st,unsigned int idx)263 static int BN_STACK_push(BN_STACK *st, unsigned int idx)
264 {
265 if (st->depth == st->size) {
266 /* Need to expand */
267 unsigned int newsize =
268 st->size ? (st->size * 3 / 2) : BN_CTX_START_FRAMES;
269 unsigned int *newitems;
270
271 if ((newitems = OPENSSL_malloc(sizeof(*newitems) * newsize)) == NULL) {
272 ERR_raise(ERR_LIB_BN, ERR_R_MALLOC_FAILURE);
273 return 0;
274 }
275 if (st->depth)
276 memcpy(newitems, st->indexes, sizeof(*newitems) * st->depth);
277 OPENSSL_free(st->indexes);
278 st->indexes = newitems;
279 st->size = newsize;
280 }
281 st->indexes[(st->depth)++] = idx;
282 return 1;
283 }
284
BN_STACK_pop(BN_STACK * st)285 static unsigned int BN_STACK_pop(BN_STACK *st)
286 {
287 return st->indexes[--(st->depth)];
288 }
289
290 /***********/
291 /* BN_POOL */
292 /***********/
293
BN_POOL_init(BN_POOL * p)294 static void BN_POOL_init(BN_POOL *p)
295 {
296 p->head = p->current = p->tail = NULL;
297 p->used = p->size = 0;
298 }
299
BN_POOL_finish(BN_POOL * p)300 static void BN_POOL_finish(BN_POOL *p)
301 {
302 unsigned int loop;
303 BIGNUM *bn;
304
305 while (p->head) {
306 for (loop = 0, bn = p->head->vals; loop++ < BN_CTX_POOL_SIZE; bn++)
307 if (bn->d)
308 BN_clear_free(bn);
309 p->current = p->head->next;
310 OPENSSL_free(p->head);
311 p->head = p->current;
312 }
313 }
314
315
BN_POOL_get(BN_POOL * p,int flag)316 static BIGNUM *BN_POOL_get(BN_POOL *p, int flag)
317 {
318 BIGNUM *bn;
319 unsigned int loop;
320
321 /* Full; allocate a new pool item and link it in. */
322 if (p->used == p->size) {
323 BN_POOL_ITEM *item;
324
325 if ((item = OPENSSL_malloc(sizeof(*item))) == NULL) {
326 ERR_raise(ERR_LIB_BN, ERR_R_MALLOC_FAILURE);
327 return NULL;
328 }
329 for (loop = 0, bn = item->vals; loop++ < BN_CTX_POOL_SIZE; bn++) {
330 bn_init(bn);
331 if ((flag & BN_FLG_SECURE) != 0)
332 BN_set_flags(bn, BN_FLG_SECURE);
333 }
334 item->prev = p->tail;
335 item->next = NULL;
336
337 if (p->head == NULL)
338 p->head = p->current = p->tail = item;
339 else {
340 p->tail->next = item;
341 p->tail = item;
342 p->current = item;
343 }
344 p->size += BN_CTX_POOL_SIZE;
345 p->used++;
346 /* Return the first bignum from the new pool */
347 return item->vals;
348 }
349
350 if (!p->used)
351 p->current = p->head;
352 else if ((p->used % BN_CTX_POOL_SIZE) == 0)
353 p->current = p->current->next;
354 return p->current->vals + ((p->used++) % BN_CTX_POOL_SIZE);
355 }
356
BN_POOL_release(BN_POOL * p,unsigned int num)357 static void BN_POOL_release(BN_POOL *p, unsigned int num)
358 {
359 unsigned int offset = (p->used - 1) % BN_CTX_POOL_SIZE;
360
361 p->used -= num;
362 while (num--) {
363 bn_check_top(p->current->vals + offset);
364 if (offset == 0) {
365 offset = BN_CTX_POOL_SIZE - 1;
366 p->current = p->current->prev;
367 } else
368 offset--;
369 }
370 }
371