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1 | /* | |
2 | * Copyright 2000-2019 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 | /*- | |
15 | * TODO list | |
16 | * | |
17 | * 1. Check a bunch of "(words+1)" type hacks in various bignum functions and | |
18 | * check they can be safely removed. | |
19 | * - Check +1 and other ugliness in BN_from_montgomery() | |
20 | * | |
21 | * 2. Consider allowing a BN_new_ex() that, at least, lets you specify an | |
22 | * appropriate 'block' size that will be honoured by bn_expand_internal() to | |
23 | * prevent piddly little reallocations. OTOH, profiling bignum expansions in | |
24 | * BN_CTX doesn't show this to be a big issue. | |
25 | */ | |
26 | ||
27 | /* How many bignums are in each "pool item"; */ | |
28 | #define BN_CTX_POOL_SIZE 16 | |
29 | /* The stack frame info is resizing, set a first-time expansion size; */ | |
30 | #define BN_CTX_START_FRAMES 32 | |
31 | ||
32 | /***********/ | |
33 | /* BN_POOL */ | |
34 | /***********/ | |
35 | ||
36 | /* A bundle of bignums that can be linked with other bundles */ | |
37 | typedef struct bignum_pool_item { | |
38 | /* The bignum values */ | |
39 | BIGNUM vals[BN_CTX_POOL_SIZE]; | |
40 | /* Linked-list admin */ | |
41 | struct bignum_pool_item *prev, *next; | |
42 | } BN_POOL_ITEM; | |
43 | /* A linked-list of bignums grouped in bundles */ | |
44 | typedef struct bignum_pool { | |
45 | /* Linked-list admin */ | |
46 | BN_POOL_ITEM *head, *current, *tail; | |
47 | /* Stack depth and allocation size */ | |
48 | unsigned used, size; | |
49 | } BN_POOL; | |
50 | static void BN_POOL_init(BN_POOL *); | |
51 | static void BN_POOL_finish(BN_POOL *); | |
52 | static BIGNUM *BN_POOL_get(BN_POOL *, int); | |
53 | static void BN_POOL_release(BN_POOL *, unsigned int); | |
54 | ||
55 | /************/ | |
56 | /* BN_STACK */ | |
57 | /************/ | |
58 | ||
59 | /* A wrapper to manage the "stack frames" */ | |
60 | typedef struct bignum_ctx_stack { | |
61 | /* Array of indexes into the bignum stack */ | |
62 | unsigned int *indexes; | |
63 | /* Number of stack frames, and the size of the allocated array */ | |
64 | unsigned int depth, size; | |
65 | } BN_STACK; | |
66 | static void BN_STACK_init(BN_STACK *); | |
67 | static void BN_STACK_finish(BN_STACK *); | |
68 | static int BN_STACK_push(BN_STACK *, unsigned int); | |
69 | static unsigned int BN_STACK_pop(BN_STACK *); | |
70 | ||
71 | /**********/ | |
72 | /* BN_CTX */ | |
73 | /**********/ | |
74 | ||
75 | /* The opaque BN_CTX type */ | |
76 | struct bignum_ctx { | |
77 | /* The bignum bundles */ | |
78 | BN_POOL pool; | |
79 | /* The "stack frames", if you will */ | |
80 | BN_STACK stack; | |
81 | /* The number of bignums currently assigned */ | |
82 | unsigned int used; | |
83 | /* Depth of stack overflow */ | |
84 | int err_stack; | |
85 | /* Block "gets" until an "end" (compatibility behaviour) */ | |
86 | int too_many; | |
87 | /* Flags. */ | |
88 | int flags; | |
89 | /* The library context */ | |
90 | OPENSSL_CTX *libctx; | |
91 | }; | |
92 | ||
93 | #ifndef FIPS_MODE | |
94 | /* Debugging functionality */ | |
95 | static void ctxdbg(BIO *channel, const char *text, BN_CTX *ctx) | |
96 | { | |
97 | unsigned int bnidx = 0, fpidx = 0; | |
98 | BN_POOL_ITEM *item = ctx->pool.head; | |
99 | BN_STACK *stack = &ctx->stack; | |
100 | ||
101 | BIO_printf(channel, "%s\n", text); | |
102 | BIO_printf(channel, " (%16p): ", (void*)ctx); | |
103 | while (bnidx < ctx->used) { | |
104 | BIO_printf(channel, "%03x ", | |
105 | item->vals[bnidx++ % BN_CTX_POOL_SIZE].dmax); | |
106 | if (!(bnidx % BN_CTX_POOL_SIZE)) | |
107 | item = item->next; | |
108 | } | |
109 | BIO_printf(channel, "\n"); | |
110 | bnidx = 0; | |
111 | BIO_printf(channel, " %16s : ", ""); | |
112 | while (fpidx < stack->depth) { | |
113 | while (bnidx++ < stack->indexes[fpidx]) | |
114 | BIO_printf(channel, " "); | |
115 | BIO_printf(channel, "^^^ "); | |
116 | bnidx++; | |
117 | fpidx++; | |
118 | } | |
119 | BIO_printf(channel, "\n"); | |
120 | } | |
121 | ||
122 | # define CTXDBG(str, ctx) \ | |
123 | OSSL_TRACE_BEGIN(BN_CTX) { \ | |
124 | ctxdbg(trc_out, str, ctx); \ | |
125 | } OSSL_TRACE_END(BN_CTX) | |
126 | #else | |
127 | /* TODO(3.0): Consider if we want to do this in FIPS mode */ | |
128 | # define CTXDBG(str, ctx) do {} while(0) | |
129 | #endif /* FIPS_MODE */ | |
130 | ||
131 | BN_CTX *BN_CTX_new_ex(OPENSSL_CTX *ctx) | |
132 | { | |
133 | BN_CTX *ret; | |
134 | ||
135 | if ((ret = OPENSSL_zalloc(sizeof(*ret))) == NULL) { | |
136 | BNerr(BN_F_BN_CTX_NEW_EX, ERR_R_MALLOC_FAILURE); | |
137 | return NULL; | |
138 | } | |
139 | /* Initialise the structure */ | |
140 | BN_POOL_init(&ret->pool); | |
141 | BN_STACK_init(&ret->stack); | |
142 | ret->libctx = ctx; | |
143 | return ret; | |
144 | } | |
145 | ||
146 | #ifndef FIPS_MODE | |
147 | BN_CTX *BN_CTX_new(void) | |
148 | { | |
149 | return BN_CTX_new_ex(NULL); | |
150 | } | |
151 | #endif | |
152 | ||
153 | BN_CTX *BN_CTX_secure_new_ex(OPENSSL_CTX *ctx) | |
154 | { | |
155 | BN_CTX *ret = BN_CTX_new_ex(ctx); | |
156 | ||
157 | if (ret != NULL) | |
158 | ret->flags = BN_FLG_SECURE; | |
159 | return ret; | |
160 | } | |
161 | ||
162 | #ifndef FIPS_MODE | |
163 | BN_CTX *BN_CTX_secure_new(void) | |
164 | { | |
165 | return BN_CTX_secure_new_ex(NULL); | |
166 | } | |
167 | #endif | |
168 | ||
169 | void BN_CTX_free(BN_CTX *ctx) | |
170 | { | |
171 | if (ctx == NULL) | |
172 | return; | |
173 | #ifndef FIPS_MODE | |
174 | OSSL_TRACE_BEGIN(BN_CTX) { | |
175 | BN_POOL_ITEM *pool = ctx->pool.head; | |
176 | BIO_printf(trc_out, | |
177 | "BN_CTX_free(): stack-size=%d, pool-bignums=%d\n", | |
178 | ctx->stack.size, ctx->pool.size); | |
179 | BIO_printf(trc_out, " dmaxs: "); | |
180 | while (pool) { | |
181 | unsigned loop = 0; | |
182 | while (loop < BN_CTX_POOL_SIZE) | |
183 | BIO_printf(trc_out, "%02x ", pool->vals[loop++].dmax); | |
184 | pool = pool->next; | |
185 | } | |
186 | BIO_printf(trc_out, "\n"); | |
187 | } OSSL_TRACE_END(BN_CTX); | |
188 | #endif | |
189 | BN_STACK_finish(&ctx->stack); | |
190 | BN_POOL_finish(&ctx->pool); | |
191 | OPENSSL_free(ctx); | |
192 | } | |
193 | ||
194 | void BN_CTX_start(BN_CTX *ctx) | |
195 | { | |
196 | CTXDBG("ENTER BN_CTX_start()", ctx); | |
197 | /* If we're already overflowing ... */ | |
198 | if (ctx->err_stack || ctx->too_many) | |
199 | ctx->err_stack++; | |
200 | /* (Try to) get a new frame pointer */ | |
201 | else if (!BN_STACK_push(&ctx->stack, ctx->used)) { | |
202 | BNerr(BN_F_BN_CTX_START, BN_R_TOO_MANY_TEMPORARY_VARIABLES); | |
203 | ctx->err_stack++; | |
204 | } | |
205 | CTXDBG("LEAVE BN_CTX_start()", ctx); | |
206 | } | |
207 | ||
208 | void BN_CTX_end(BN_CTX *ctx) | |
209 | { | |
210 | if (ctx == NULL) | |
211 | return; | |
212 | CTXDBG("ENTER BN_CTX_end()", ctx); | |
213 | if (ctx->err_stack) | |
214 | ctx->err_stack--; | |
215 | else { | |
216 | unsigned int fp = BN_STACK_pop(&ctx->stack); | |
217 | /* Does this stack frame have anything to release? */ | |
218 | if (fp < ctx->used) | |
219 | BN_POOL_release(&ctx->pool, ctx->used - fp); | |
220 | ctx->used = fp; | |
221 | /* Unjam "too_many" in case "get" had failed */ | |
222 | ctx->too_many = 0; | |
223 | } | |
224 | CTXDBG("LEAVE BN_CTX_end()", ctx); | |
225 | } | |
226 | ||
227 | BIGNUM *BN_CTX_get(BN_CTX *ctx) | |
228 | { | |
229 | BIGNUM *ret; | |
230 | ||
231 | CTXDBG("ENTER BN_CTX_get()", ctx); | |
232 | if (ctx->err_stack || ctx->too_many) | |
233 | return NULL; | |
234 | if ((ret = BN_POOL_get(&ctx->pool, ctx->flags)) == NULL) { | |
235 | /* | |
236 | * Setting too_many prevents repeated "get" attempts from cluttering | |
237 | * the error stack. | |
238 | */ | |
239 | ctx->too_many = 1; | |
240 | BNerr(BN_F_BN_CTX_GET, BN_R_TOO_MANY_TEMPORARY_VARIABLES); | |
241 | return NULL; | |
242 | } | |
243 | /* OK, make sure the returned bignum is "zero" */ | |
244 | BN_zero(ret); | |
245 | /* clear BN_FLG_CONSTTIME if leaked from previous frames */ | |
246 | ret->flags &= (~BN_FLG_CONSTTIME); | |
247 | ctx->used++; | |
248 | CTXDBG("LEAVE BN_CTX_get()", ctx); | |
249 | return ret; | |
250 | } | |
251 | ||
252 | OPENSSL_CTX *bn_get_lib_ctx(BN_CTX *ctx) | |
253 | { | |
254 | if (ctx == NULL) | |
255 | return NULL; | |
256 | return ctx->libctx; | |
257 | } | |
258 | ||
259 | /************/ | |
260 | /* BN_STACK */ | |
261 | /************/ | |
262 | ||
263 | static void BN_STACK_init(BN_STACK *st) | |
264 | { | |
265 | st->indexes = NULL; | |
266 | st->depth = st->size = 0; | |
267 | } | |
268 | ||
269 | static void BN_STACK_finish(BN_STACK *st) | |
270 | { | |
271 | OPENSSL_free(st->indexes); | |
272 | st->indexes = NULL; | |
273 | } | |
274 | ||
275 | ||
276 | static int BN_STACK_push(BN_STACK *st, unsigned int idx) | |
277 | { | |
278 | if (st->depth == st->size) { | |
279 | /* Need to expand */ | |
280 | unsigned int newsize = | |
281 | st->size ? (st->size * 3 / 2) : BN_CTX_START_FRAMES; | |
282 | unsigned int *newitems; | |
283 | ||
284 | if ((newitems = OPENSSL_malloc(sizeof(*newitems) * newsize)) == NULL) { | |
285 | BNerr(BN_F_BN_STACK_PUSH, ERR_R_MALLOC_FAILURE); | |
286 | return 0; | |
287 | } | |
288 | if (st->depth) | |
289 | memcpy(newitems, st->indexes, sizeof(*newitems) * st->depth); | |
290 | OPENSSL_free(st->indexes); | |
291 | st->indexes = newitems; | |
292 | st->size = newsize; | |
293 | } | |
294 | st->indexes[(st->depth)++] = idx; | |
295 | return 1; | |
296 | } | |
297 | ||
298 | static unsigned int BN_STACK_pop(BN_STACK *st) | |
299 | { | |
300 | return st->indexes[--(st->depth)]; | |
301 | } | |
302 | ||
303 | /***********/ | |
304 | /* BN_POOL */ | |
305 | /***********/ | |
306 | ||
307 | static void BN_POOL_init(BN_POOL *p) | |
308 | { | |
309 | p->head = p->current = p->tail = NULL; | |
310 | p->used = p->size = 0; | |
311 | } | |
312 | ||
313 | static void BN_POOL_finish(BN_POOL *p) | |
314 | { | |
315 | unsigned int loop; | |
316 | BIGNUM *bn; | |
317 | ||
318 | while (p->head) { | |
319 | for (loop = 0, bn = p->head->vals; loop++ < BN_CTX_POOL_SIZE; bn++) | |
320 | if (bn->d) | |
321 | BN_clear_free(bn); | |
322 | p->current = p->head->next; | |
323 | OPENSSL_free(p->head); | |
324 | p->head = p->current; | |
325 | } | |
326 | } | |
327 | ||
328 | ||
329 | static BIGNUM *BN_POOL_get(BN_POOL *p, int flag) | |
330 | { | |
331 | BIGNUM *bn; | |
332 | unsigned int loop; | |
333 | ||
334 | /* Full; allocate a new pool item and link it in. */ | |
335 | if (p->used == p->size) { | |
336 | BN_POOL_ITEM *item; | |
337 | ||
338 | if ((item = OPENSSL_malloc(sizeof(*item))) == NULL) { | |
339 | BNerr(BN_F_BN_POOL_GET, ERR_R_MALLOC_FAILURE); | |
340 | return NULL; | |
341 | } | |
342 | for (loop = 0, bn = item->vals; loop++ < BN_CTX_POOL_SIZE; bn++) { | |
343 | bn_init(bn); | |
344 | if ((flag & BN_FLG_SECURE) != 0) | |
345 | BN_set_flags(bn, BN_FLG_SECURE); | |
346 | } | |
347 | item->prev = p->tail; | |
348 | item->next = NULL; | |
349 | ||
350 | if (p->head == NULL) | |
351 | p->head = p->current = p->tail = item; | |
352 | else { | |
353 | p->tail->next = item; | |
354 | p->tail = item; | |
355 | p->current = item; | |
356 | } | |
357 | p->size += BN_CTX_POOL_SIZE; | |
358 | p->used++; | |
359 | /* Return the first bignum from the new pool */ | |
360 | return item->vals; | |
361 | } | |
362 | ||
363 | if (!p->used) | |
364 | p->current = p->head; | |
365 | else if ((p->used % BN_CTX_POOL_SIZE) == 0) | |
366 | p->current = p->current->next; | |
367 | return p->current->vals + ((p->used++) % BN_CTX_POOL_SIZE); | |
368 | } | |
369 | ||
370 | static void BN_POOL_release(BN_POOL *p, unsigned int num) | |
371 | { | |
372 | unsigned int offset = (p->used - 1) % BN_CTX_POOL_SIZE; | |
373 | ||
374 | p->used -= num; | |
375 | while (num--) { | |
376 | bn_check_top(p->current->vals + offset); | |
377 | if (offset == 0) { | |
378 | offset = BN_CTX_POOL_SIZE - 1; | |
379 | p->current = p->current->prev; | |
380 | } else | |
381 | offset--; | |
382 | } | |
383 | } |