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 | } |
384 | |