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 { \
112 ctxdbg(trc_out, str, ctx); \
113 } \
114 OSSL_TRACE_END(BN_CTX)
115 #else
116 /* We do not want tracing in FIPS module */
117 #define CTXDBG(str, ctx) \
118 do { \
119 } while (0)
120 #endif /* FIPS_MODULE */
121
BN_CTX_new_ex(OSSL_LIB_CTX * ctx)122 BN_CTX *BN_CTX_new_ex(OSSL_LIB_CTX *ctx)
123 {
124 BN_CTX *ret;
125
126 if ((ret = OPENSSL_zalloc(sizeof(*ret))) == NULL)
127 return NULL;
128 /* Initialise the structure */
129 BN_POOL_init(&ret->pool);
130 BN_STACK_init(&ret->stack);
131 ret->libctx = ctx;
132 return ret;
133 }
134
135 #ifndef FIPS_MODULE
BN_CTX_new(void)136 BN_CTX *BN_CTX_new(void)
137 {
138 return BN_CTX_new_ex(NULL);
139 }
140 #endif
141
BN_CTX_secure_new_ex(OSSL_LIB_CTX * ctx)142 BN_CTX *BN_CTX_secure_new_ex(OSSL_LIB_CTX *ctx)
143 {
144 BN_CTX *ret = BN_CTX_new_ex(ctx);
145
146 if (ret != NULL)
147 ret->flags = BN_FLG_SECURE;
148 return ret;
149 }
150
151 #ifndef FIPS_MODULE
BN_CTX_secure_new(void)152 BN_CTX *BN_CTX_secure_new(void)
153 {
154 return BN_CTX_secure_new_ex(NULL);
155 }
156 #endif
157
BN_CTX_free(BN_CTX * ctx)158 void BN_CTX_free(BN_CTX *ctx)
159 {
160 if (ctx == NULL)
161 return;
162 #ifndef FIPS_MODULE
163 OSSL_TRACE_BEGIN(BN_CTX)
164 {
165 BN_POOL_ITEM *pool = ctx->pool.head;
166 BIO_printf(trc_out,
167 "BN_CTX_free(): stack-size=%d, pool-bignums=%d\n",
168 ctx->stack.size, ctx->pool.size);
169 BIO_printf(trc_out, " dmaxs: ");
170 while (pool) {
171 unsigned loop = 0;
172 while (loop < BN_CTX_POOL_SIZE)
173 BIO_printf(trc_out, "%02x ", pool->vals[loop++].dmax);
174 pool = pool->next;
175 }
176 BIO_printf(trc_out, "\n");
177 }
178 OSSL_TRACE_END(BN_CTX);
179 #endif
180 BN_STACK_finish(&ctx->stack);
181 BN_POOL_finish(&ctx->pool);
182 OPENSSL_free(ctx);
183 }
184
BN_CTX_start(BN_CTX * ctx)185 void BN_CTX_start(BN_CTX *ctx)
186 {
187 CTXDBG("ENTER BN_CTX_start()", ctx);
188 /* If we're already overflowing ... */
189 if (ctx->err_stack || ctx->too_many)
190 ctx->err_stack++;
191 /* (Try to) get a new frame pointer */
192 else if (!BN_STACK_push(&ctx->stack, ctx->used)) {
193 ERR_raise(ERR_LIB_BN, BN_R_TOO_MANY_TEMPORARY_VARIABLES);
194 ctx->err_stack++;
195 }
196 CTXDBG("LEAVE BN_CTX_start()", ctx);
197 }
198
BN_CTX_end(BN_CTX * ctx)199 void BN_CTX_end(BN_CTX *ctx)
200 {
201 if (ctx == NULL)
202 return;
203 CTXDBG("ENTER BN_CTX_end()", ctx);
204 if (ctx->err_stack)
205 ctx->err_stack--;
206 else {
207 unsigned int fp = BN_STACK_pop(&ctx->stack);
208 /* Does this stack frame have anything to release? */
209 if (fp < ctx->used)
210 BN_POOL_release(&ctx->pool, ctx->used - fp);
211 ctx->used = fp;
212 /* Unjam "too_many" in case "get" had failed */
213 ctx->too_many = 0;
214 }
215 CTXDBG("LEAVE BN_CTX_end()", ctx);
216 }
217
BN_CTX_get(BN_CTX * ctx)218 BIGNUM *BN_CTX_get(BN_CTX *ctx)
219 {
220 BIGNUM *ret;
221
222 CTXDBG("ENTER BN_CTX_get()", ctx);
223 if (ctx->err_stack || ctx->too_many)
224 return NULL;
225 if ((ret = BN_POOL_get(&ctx->pool, ctx->flags)) == NULL) {
226 /*
227 * Setting too_many prevents repeated "get" attempts from cluttering
228 * the error stack.
229 */
230 ctx->too_many = 1;
231 ERR_raise(ERR_LIB_BN, BN_R_TOO_MANY_TEMPORARY_VARIABLES);
232 return NULL;
233 }
234 /* OK, make sure the returned bignum is "zero" */
235 BN_zero(ret);
236 /* clear BN_FLG_CONSTTIME if leaked from previous frames */
237 ret->flags &= (~BN_FLG_CONSTTIME);
238 ctx->used++;
239 CTXDBG("LEAVE BN_CTX_get()", ctx);
240 return ret;
241 }
242
ossl_bn_get_libctx(BN_CTX * ctx)243 OSSL_LIB_CTX *ossl_bn_get_libctx(BN_CTX *ctx)
244 {
245 if (ctx == NULL)
246 return NULL;
247 return ctx->libctx;
248 }
249
250 /************/
251 /* BN_STACK */
252 /************/
253
BN_STACK_init(BN_STACK * st)254 static void BN_STACK_init(BN_STACK *st)
255 {
256 st->indexes = NULL;
257 st->depth = st->size = 0;
258 }
259
BN_STACK_finish(BN_STACK * st)260 static void BN_STACK_finish(BN_STACK *st)
261 {
262 OPENSSL_free(st->indexes);
263 st->indexes = NULL;
264 }
265
BN_STACK_push(BN_STACK * st,unsigned int idx)266 static int BN_STACK_push(BN_STACK *st, unsigned int idx)
267 {
268 if (st->depth == st->size) {
269 /* Need to expand */
270 unsigned int newsize = st->size ? (st->size * 3 / 2) : BN_CTX_START_FRAMES;
271 unsigned int *newitems;
272
273 if ((newitems = OPENSSL_malloc(sizeof(*newitems) * newsize)) == NULL)
274 return 0;
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
BN_POOL_get(BN_POOL * p,int flag)315 static BIGNUM *BN_POOL_get(BN_POOL *p, int flag)
316 {
317 BIGNUM *bn;
318 unsigned int loop;
319
320 /* Full; allocate a new pool item and link it in. */
321 if (p->used == p->size) {
322 BN_POOL_ITEM *item;
323
324 if ((item = OPENSSL_malloc(sizeof(*item))) == NULL)
325 return NULL;
326 for (loop = 0, bn = item->vals; loop++ < BN_CTX_POOL_SIZE; bn++) {
327 bn_init(bn);
328 if ((flag & BN_FLG_SECURE) != 0)
329 BN_set_flags(bn, BN_FLG_SECURE);
330 }
331 item->prev = p->tail;
332 item->next = NULL;
333
334 if (p->head == NULL)
335 p->head = p->current = p->tail = item;
336 else {
337 p->tail->next = item;
338 p->tail = item;
339 p->current = item;
340 }
341 p->size += BN_CTX_POOL_SIZE;
342 p->used++;
343 /* Return the first bignum from the new pool */
344 return item->vals;
345 }
346
347 if (!p->used)
348 p->current = p->head;
349 else if ((p->used % BN_CTX_POOL_SIZE) == 0)
350 p->current = p->current->next;
351 return p->current->vals + ((p->used++) % BN_CTX_POOL_SIZE);
352 }
353
BN_POOL_release(BN_POOL * p,unsigned int num)354 static void BN_POOL_release(BN_POOL *p, unsigned int num)
355 {
356 unsigned int offset = (p->used - 1) % BN_CTX_POOL_SIZE;
357
358 p->used -= num;
359 while (num--) {
360 bn_check_top(p->current->vals + offset);
361 if (offset == 0) {
362 offset = BN_CTX_POOL_SIZE - 1;
363 p->current = p->current->prev;
364 } else
365 offset--;
366 }
367 }
368