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 return NULL;
124 /* Initialise the structure */
125 BN_POOL_init(&ret->pool);
126 BN_STACK_init(&ret->stack);
127 ret->libctx = ctx;
128 return ret;
129 }
130
131 #ifndef FIPS_MODULE
BN_CTX_new(void)132 BN_CTX *BN_CTX_new(void)
133 {
134 return BN_CTX_new_ex(NULL);
135 }
136 #endif
137
BN_CTX_secure_new_ex(OSSL_LIB_CTX * ctx)138 BN_CTX *BN_CTX_secure_new_ex(OSSL_LIB_CTX *ctx)
139 {
140 BN_CTX *ret = BN_CTX_new_ex(ctx);
141
142 if (ret != NULL)
143 ret->flags = BN_FLG_SECURE;
144 return ret;
145 }
146
147 #ifndef FIPS_MODULE
BN_CTX_secure_new(void)148 BN_CTX *BN_CTX_secure_new(void)
149 {
150 return BN_CTX_secure_new_ex(NULL);
151 }
152 #endif
153
BN_CTX_free(BN_CTX * ctx)154 void BN_CTX_free(BN_CTX *ctx)
155 {
156 if (ctx == NULL)
157 return;
158 #ifndef FIPS_MODULE
159 OSSL_TRACE_BEGIN(BN_CTX) {
160 BN_POOL_ITEM *pool = ctx->pool.head;
161 BIO_printf(trc_out,
162 "BN_CTX_free(): stack-size=%d, pool-bignums=%d\n",
163 ctx->stack.size, ctx->pool.size);
164 BIO_printf(trc_out, " dmaxs: ");
165 while (pool) {
166 unsigned loop = 0;
167 while (loop < BN_CTX_POOL_SIZE)
168 BIO_printf(trc_out, "%02x ", pool->vals[loop++].dmax);
169 pool = pool->next;
170 }
171 BIO_printf(trc_out, "\n");
172 } OSSL_TRACE_END(BN_CTX);
173 #endif
174 BN_STACK_finish(&ctx->stack);
175 BN_POOL_finish(&ctx->pool);
176 OPENSSL_free(ctx);
177 }
178
BN_CTX_start(BN_CTX * ctx)179 void BN_CTX_start(BN_CTX *ctx)
180 {
181 CTXDBG("ENTER BN_CTX_start()", ctx);
182 /* If we're already overflowing ... */
183 if (ctx->err_stack || ctx->too_many)
184 ctx->err_stack++;
185 /* (Try to) get a new frame pointer */
186 else if (!BN_STACK_push(&ctx->stack, ctx->used)) {
187 ERR_raise(ERR_LIB_BN, BN_R_TOO_MANY_TEMPORARY_VARIABLES);
188 ctx->err_stack++;
189 }
190 CTXDBG("LEAVE BN_CTX_start()", ctx);
191 }
192
BN_CTX_end(BN_CTX * ctx)193 void BN_CTX_end(BN_CTX *ctx)
194 {
195 if (ctx == NULL)
196 return;
197 CTXDBG("ENTER BN_CTX_end()", ctx);
198 if (ctx->err_stack)
199 ctx->err_stack--;
200 else {
201 unsigned int fp = BN_STACK_pop(&ctx->stack);
202 /* Does this stack frame have anything to release? */
203 if (fp < ctx->used)
204 BN_POOL_release(&ctx->pool, ctx->used - fp);
205 ctx->used = fp;
206 /* Unjam "too_many" in case "get" had failed */
207 ctx->too_many = 0;
208 }
209 CTXDBG("LEAVE BN_CTX_end()", ctx);
210 }
211
BN_CTX_get(BN_CTX * ctx)212 BIGNUM *BN_CTX_get(BN_CTX *ctx)
213 {
214 BIGNUM *ret;
215
216 CTXDBG("ENTER BN_CTX_get()", ctx);
217 if (ctx->err_stack || ctx->too_many)
218 return NULL;
219 if ((ret = BN_POOL_get(&ctx->pool, ctx->flags)) == NULL) {
220 /*
221 * Setting too_many prevents repeated "get" attempts from cluttering
222 * the error stack.
223 */
224 ctx->too_many = 1;
225 ERR_raise(ERR_LIB_BN, BN_R_TOO_MANY_TEMPORARY_VARIABLES);
226 return NULL;
227 }
228 /* OK, make sure the returned bignum is "zero" */
229 BN_zero(ret);
230 /* clear BN_FLG_CONSTTIME if leaked from previous frames */
231 ret->flags &= (~BN_FLG_CONSTTIME);
232 ctx->used++;
233 CTXDBG("LEAVE BN_CTX_get()", ctx);
234 return ret;
235 }
236
ossl_bn_get_libctx(BN_CTX * ctx)237 OSSL_LIB_CTX *ossl_bn_get_libctx(BN_CTX *ctx)
238 {
239 if (ctx == NULL)
240 return NULL;
241 return ctx->libctx;
242 }
243
244 /************/
245 /* BN_STACK */
246 /************/
247
BN_STACK_init(BN_STACK * st)248 static void BN_STACK_init(BN_STACK *st)
249 {
250 st->indexes = NULL;
251 st->depth = st->size = 0;
252 }
253
BN_STACK_finish(BN_STACK * st)254 static void BN_STACK_finish(BN_STACK *st)
255 {
256 OPENSSL_free(st->indexes);
257 st->indexes = NULL;
258 }
259
260
BN_STACK_push(BN_STACK * st,unsigned int idx)261 static int BN_STACK_push(BN_STACK *st, unsigned int idx)
262 {
263 if (st->depth == st->size) {
264 /* Need to expand */
265 unsigned int newsize =
266 st->size ? (st->size * 3 / 2) : BN_CTX_START_FRAMES;
267 unsigned int *newitems;
268
269 if ((newitems = OPENSSL_malloc(sizeof(*newitems) * newsize)) == NULL)
270 return 0;
271 if (st->depth)
272 memcpy(newitems, st->indexes, sizeof(*newitems) * st->depth);
273 OPENSSL_free(st->indexes);
274 st->indexes = newitems;
275 st->size = newsize;
276 }
277 st->indexes[(st->depth)++] = idx;
278 return 1;
279 }
280
BN_STACK_pop(BN_STACK * st)281 static unsigned int BN_STACK_pop(BN_STACK *st)
282 {
283 return st->indexes[--(st->depth)];
284 }
285
286 /***********/
287 /* BN_POOL */
288 /***********/
289
BN_POOL_init(BN_POOL * p)290 static void BN_POOL_init(BN_POOL *p)
291 {
292 p->head = p->current = p->tail = NULL;
293 p->used = p->size = 0;
294 }
295
BN_POOL_finish(BN_POOL * p)296 static void BN_POOL_finish(BN_POOL *p)
297 {
298 unsigned int loop;
299 BIGNUM *bn;
300
301 while (p->head) {
302 for (loop = 0, bn = p->head->vals; loop++ < BN_CTX_POOL_SIZE; bn++)
303 if (bn->d)
304 BN_clear_free(bn);
305 p->current = p->head->next;
306 OPENSSL_free(p->head);
307 p->head = p->current;
308 }
309 }
310
311
BN_POOL_get(BN_POOL * p,int flag)312 static BIGNUM *BN_POOL_get(BN_POOL *p, int flag)
313 {
314 BIGNUM *bn;
315 unsigned int loop;
316
317 /* Full; allocate a new pool item and link it in. */
318 if (p->used == p->size) {
319 BN_POOL_ITEM *item;
320
321 if ((item = OPENSSL_malloc(sizeof(*item))) == NULL)
322 return NULL;
323 for (loop = 0, bn = item->vals; loop++ < BN_CTX_POOL_SIZE; bn++) {
324 bn_init(bn);
325 if ((flag & BN_FLG_SECURE) != 0)
326 BN_set_flags(bn, BN_FLG_SECURE);
327 }
328 item->prev = p->tail;
329 item->next = NULL;
330
331 if (p->head == NULL)
332 p->head = p->current = p->tail = item;
333 else {
334 p->tail->next = item;
335 p->tail = item;
336 p->current = item;
337 }
338 p->size += BN_CTX_POOL_SIZE;
339 p->used++;
340 /* Return the first bignum from the new pool */
341 return item->vals;
342 }
343
344 if (!p->used)
345 p->current = p->head;
346 else if ((p->used % BN_CTX_POOL_SIZE) == 0)
347 p->current = p->current->next;
348 return p->current->vals + ((p->used++) % BN_CTX_POOL_SIZE);
349 }
350
BN_POOL_release(BN_POOL * p,unsigned int num)351 static void BN_POOL_release(BN_POOL *p, unsigned int num)
352 {
353 unsigned int offset = (p->used - 1) % BN_CTX_POOL_SIZE;
354
355 p->used -= num;
356 while (num--) {
357 bn_check_top(p->current->vals + offset);
358 if (offset == 0) {
359 offset = BN_CTX_POOL_SIZE - 1;
360 p->current = p->current->prev;
361 } else
362 offset--;
363 }
364 }
365
