2 * Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.
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
10 #include <openssl/trace.h>
11 #include "internal/cryptlib.h"
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()
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.
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
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
;
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 */
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);
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
;
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
*);
75 /* The opaque BN_CTX type */
77 /* The bignum bundles */
79 /* The "stack frames", if you will */
81 /* The number of bignums currently assigned */
83 /* Depth of stack overflow */
85 /* Block "gets" until an "end" (compatibility behaviour) */
89 /* The library context */
94 /* Debugging functionality */
95 static void ctxdbg(BIO
*channel
, const char *text
, BN_CTX
*ctx
)
97 unsigned int bnidx
= 0, fpidx
= 0;
98 BN_POOL_ITEM
*item
= ctx
->pool
.head
;
99 BN_STACK
*stack
= &ctx
->stack
;
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
))
109 BIO_printf(channel
, "\n");
111 BIO_printf(channel
, " %16s : ", "");
112 while (fpidx
< stack
->depth
) {
113 while (bnidx
++ < stack
->indexes
[fpidx
])
114 BIO_printf(channel
, " ");
115 BIO_printf(channel
, "^^^ ");
119 BIO_printf(channel
, "\n");
122 # define CTXDBG(str, ctx) \
123 OSSL_TRACE_BEGIN(BN_CTX) { \
124 ctxdbg(trc_out, str, ctx); \
125 } OSSL_TRACE_END(BN_CTX)
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_MODULE */
131 BN_CTX
*BN_CTX_new_ex(OPENSSL_CTX
*ctx
)
135 if ((ret
= OPENSSL_zalloc(sizeof(*ret
))) == NULL
) {
136 BNerr(BN_F_BN_CTX_NEW_EX
, ERR_R_MALLOC_FAILURE
);
139 /* Initialise the structure */
140 BN_POOL_init(&ret
->pool
);
141 BN_STACK_init(&ret
->stack
);
147 BN_CTX
*BN_CTX_new(void)
149 return BN_CTX_new_ex(NULL
);
153 BN_CTX
*BN_CTX_secure_new_ex(OPENSSL_CTX
*ctx
)
155 BN_CTX
*ret
= BN_CTX_new_ex(ctx
);
158 ret
->flags
= BN_FLG_SECURE
;
163 BN_CTX
*BN_CTX_secure_new(void)
165 return BN_CTX_secure_new_ex(NULL
);
169 void BN_CTX_free(BN_CTX
*ctx
)
174 OSSL_TRACE_BEGIN(BN_CTX
) {
175 BN_POOL_ITEM
*pool
= ctx
->pool
.head
;
177 "BN_CTX_free(): stack-size=%d, pool-bignums=%d\n",
178 ctx
->stack
.size
, ctx
->pool
.size
);
179 BIO_printf(trc_out
, " dmaxs: ");
182 while (loop
< BN_CTX_POOL_SIZE
)
183 BIO_printf(trc_out
, "%02x ", pool
->vals
[loop
++].dmax
);
186 BIO_printf(trc_out
, "\n");
187 } OSSL_TRACE_END(BN_CTX
);
189 BN_STACK_finish(&ctx
->stack
);
190 BN_POOL_finish(&ctx
->pool
);
194 void BN_CTX_start(BN_CTX
*ctx
)
196 CTXDBG("ENTER BN_CTX_start()", ctx
);
197 /* If we're already overflowing ... */
198 if (ctx
->err_stack
|| ctx
->too_many
)
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
);
205 CTXDBG("LEAVE BN_CTX_start()", ctx
);
208 void BN_CTX_end(BN_CTX
*ctx
)
212 CTXDBG("ENTER BN_CTX_end()", ctx
);
216 unsigned int fp
= BN_STACK_pop(&ctx
->stack
);
217 /* Does this stack frame have anything to release? */
219 BN_POOL_release(&ctx
->pool
, ctx
->used
- fp
);
221 /* Unjam "too_many" in case "get" had failed */
224 CTXDBG("LEAVE BN_CTX_end()", ctx
);
227 BIGNUM
*BN_CTX_get(BN_CTX
*ctx
)
231 CTXDBG("ENTER BN_CTX_get()", ctx
);
232 if (ctx
->err_stack
|| ctx
->too_many
)
234 if ((ret
= BN_POOL_get(&ctx
->pool
, ctx
->flags
)) == NULL
) {
236 * Setting too_many prevents repeated "get" attempts from cluttering
240 BNerr(BN_F_BN_CTX_GET
, BN_R_TOO_MANY_TEMPORARY_VARIABLES
);
243 /* OK, make sure the returned bignum is "zero" */
245 /* clear BN_FLG_CONSTTIME if leaked from previous frames */
246 ret
->flags
&= (~BN_FLG_CONSTTIME
);
248 CTXDBG("LEAVE BN_CTX_get()", ctx
);
252 OPENSSL_CTX
*bn_get_lib_ctx(BN_CTX
*ctx
)
263 static void BN_STACK_init(BN_STACK
*st
)
266 st
->depth
= st
->size
= 0;
269 static void BN_STACK_finish(BN_STACK
*st
)
271 OPENSSL_free(st
->indexes
);
276 static int BN_STACK_push(BN_STACK
*st
, unsigned int idx
)
278 if (st
->depth
== st
->size
) {
280 unsigned int newsize
=
281 st
->size
? (st
->size
* 3 / 2) : BN_CTX_START_FRAMES
;
282 unsigned int *newitems
;
284 if ((newitems
= OPENSSL_malloc(sizeof(*newitems
) * newsize
)) == NULL
) {
285 BNerr(BN_F_BN_STACK_PUSH
, ERR_R_MALLOC_FAILURE
);
289 memcpy(newitems
, st
->indexes
, sizeof(*newitems
) * st
->depth
);
290 OPENSSL_free(st
->indexes
);
291 st
->indexes
= newitems
;
294 st
->indexes
[(st
->depth
)++] = idx
;
298 static unsigned int BN_STACK_pop(BN_STACK
*st
)
300 return st
->indexes
[--(st
->depth
)];
307 static void BN_POOL_init(BN_POOL
*p
)
309 p
->head
= p
->current
= p
->tail
= NULL
;
310 p
->used
= p
->size
= 0;
313 static void BN_POOL_finish(BN_POOL
*p
)
319 for (loop
= 0, bn
= p
->head
->vals
; loop
++ < BN_CTX_POOL_SIZE
; bn
++)
322 p
->current
= p
->head
->next
;
323 OPENSSL_free(p
->head
);
324 p
->head
= p
->current
;
329 static BIGNUM
*BN_POOL_get(BN_POOL
*p
, int flag
)
334 /* Full; allocate a new pool item and link it in. */
335 if (p
->used
== p
->size
) {
338 if ((item
= OPENSSL_malloc(sizeof(*item
))) == NULL
) {
339 BNerr(BN_F_BN_POOL_GET
, ERR_R_MALLOC_FAILURE
);
342 for (loop
= 0, bn
= item
->vals
; loop
++ < BN_CTX_POOL_SIZE
; bn
++) {
344 if ((flag
& BN_FLG_SECURE
) != 0)
345 BN_set_flags(bn
, BN_FLG_SECURE
);
347 item
->prev
= p
->tail
;
351 p
->head
= p
->current
= p
->tail
= item
;
353 p
->tail
->next
= item
;
357 p
->size
+= BN_CTX_POOL_SIZE
;
359 /* Return the first bignum from the new pool */
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
);
370 static void BN_POOL_release(BN_POOL
*p
, unsigned int num
)
372 unsigned int offset
= (p
->used
- 1) % BN_CTX_POOL_SIZE
;
376 bn_check_top(p
->current
->vals
+ offset
);
378 offset
= BN_CTX_POOL_SIZE
- 1;
379 p
->current
= p
->current
->prev
;