2 * Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.
4 * Licensed under the OpenSSL license (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 "internal/cryptlib.h"
16 * 1. Check a bunch of "(words+1)" type hacks in various bignum functions and
17 * check they can be safely removed.
18 * - Check +1 and other ugliness in BN_from_montgomery()
20 * 2. Consider allowing a BN_new_ex() that, at least, lets you specify an
21 * appropriate 'block' size that will be honoured by bn_expand_internal() to
22 * prevent piddly little reallocations. OTOH, profiling bignum expansions in
23 * BN_CTX doesn't show this to be a big issue.
26 /* How many bignums are in each "pool item"; */
27 #define BN_CTX_POOL_SIZE 16
28 /* The stack frame info is resizing, set a first-time expansion size; */
29 #define BN_CTX_START_FRAMES 32
35 /* A bundle of bignums that can be linked with other bundles */
36 typedef struct bignum_pool_item {
37 /* The bignum values */
38 BIGNUM vals[BN_CTX_POOL_SIZE];
39 /* Linked-list admin */
40 struct bignum_pool_item *prev, *next;
42 /* A linked-list of bignums grouped in bundles */
43 typedef struct bignum_pool {
44 /* Linked-list admin */
45 BN_POOL_ITEM *head, *current, *tail;
46 /* Stack depth and allocation size */
49 static void BN_POOL_init(BN_POOL *);
50 static void BN_POOL_finish(BN_POOL *);
51 static BIGNUM *BN_POOL_get(BN_POOL *, int);
52 static void BN_POOL_release(BN_POOL *, unsigned int);
58 /* A wrapper to manage the "stack frames" */
59 typedef struct bignum_ctx_stack {
60 /* Array of indexes into the bignum stack */
61 unsigned int *indexes;
62 /* Number of stack frames, and the size of the allocated array */
63 unsigned int depth, size;
65 static void BN_STACK_init(BN_STACK *);
66 static void BN_STACK_finish(BN_STACK *);
67 static int BN_STACK_push(BN_STACK *, unsigned int);
68 static unsigned int BN_STACK_pop(BN_STACK *);
74 /* The opaque BN_CTX type */
76 /* The bignum bundles */
78 /* The "stack frames", if you will */
80 /* The number of bignums currently assigned */
82 /* Depth of stack overflow */
84 /* Block "gets" until an "end" (compatibility behaviour) */
90 /* Enable this to find BN_CTX bugs */
92 static const char *ctxdbg_cur = NULL;
93 static void ctxdbg(BN_CTX *ctx)
95 unsigned int bnidx = 0, fpidx = 0;
96 BN_POOL_ITEM *item = ctx->pool.head;
97 BN_STACK *stack = &ctx->stack;
98 fprintf(stderr, "(%16p): ", ctx);
99 while (bnidx < ctx->used) {
100 fprintf(stderr, "%03x ", item->vals[bnidx++ % BN_CTX_POOL_SIZE].dmax);
101 if (!(bnidx % BN_CTX_POOL_SIZE))
104 fprintf(stderr, "\n");
106 fprintf(stderr, " : ");
107 while (fpidx < stack->depth) {
108 while (bnidx++ < stack->indexes[fpidx])
109 fprintf(stderr, " ");
110 fprintf(stderr, "^^^ ");
114 fprintf(stderr, "\n");
117 # define CTXDBG_ENTRY(str, ctx) do { \
118 ctxdbg_cur = (str); \
119 fprintf(stderr,"Starting %s\n", ctxdbg_cur); \
122 # define CTXDBG_EXIT(ctx) do { \
123 fprintf(stderr,"Ending %s\n", ctxdbg_cur); \
126 # define CTXDBG_RET(ctx,ret)
128 # define CTXDBG_ENTRY(str, ctx)
129 # define CTXDBG_EXIT(ctx)
130 # define CTXDBG_RET(ctx,ret)
134 BN_CTX *BN_CTX_new(void)
138 if ((ret = OPENSSL_zalloc(sizeof(*ret))) == NULL) {
139 BNerr(BN_F_BN_CTX_NEW, ERR_R_MALLOC_FAILURE);
142 /* Initialise the structure */
143 BN_POOL_init(&ret->pool);
144 BN_STACK_init(&ret->stack);
148 BN_CTX *BN_CTX_secure_new(void)
150 BN_CTX *ret = BN_CTX_new();
153 ret->flags = BN_FLG_SECURE;
157 void BN_CTX_free(BN_CTX *ctx)
163 BN_POOL_ITEM *pool = ctx->pool.head;
164 fprintf(stderr, "BN_CTX_free, stack-size=%d, pool-bignums=%d\n",
165 ctx->stack.size, ctx->pool.size);
166 fprintf(stderr, "dmaxs: ");
169 while (loop < BN_CTX_POOL_SIZE)
170 fprintf(stderr, "%02x ", pool->vals[loop++].dmax);
173 fprintf(stderr, "\n");
176 BN_STACK_finish(&ctx->stack);
177 BN_POOL_finish(&ctx->pool);
181 void BN_CTX_start(BN_CTX *ctx)
183 CTXDBG_ENTRY("BN_CTX_start", ctx);
184 /* If we're already overflowing ... */
185 if (ctx->err_stack || ctx->too_many)
187 /* (Try to) get a new frame pointer */
188 else if (!BN_STACK_push(&ctx->stack, ctx->used)) {
189 BNerr(BN_F_BN_CTX_START, BN_R_TOO_MANY_TEMPORARY_VARIABLES);
195 void BN_CTX_end(BN_CTX *ctx)
197 CTXDBG_ENTRY("BN_CTX_end", ctx);
201 unsigned int fp = BN_STACK_pop(&ctx->stack);
202 /* Does this stack frame have anything to release? */
204 BN_POOL_release(&ctx->pool, ctx->used - fp);
206 /* Unjam "too_many" in case "get" had failed */
212 BIGNUM *BN_CTX_get(BN_CTX *ctx)
216 CTXDBG_ENTRY("BN_CTX_get", ctx);
217 if (ctx->err_stack || ctx->too_many)
219 if ((ret = BN_POOL_get(&ctx->pool, ctx->flags)) == NULL) {
221 * Setting too_many prevents repeated "get" attempts from cluttering
225 BNerr(BN_F_BN_CTX_GET, BN_R_TOO_MANY_TEMPORARY_VARIABLES);
228 /* OK, make sure the returned bignum is "zero" */
231 CTXDBG_RET(ctx, ret);
239 static void BN_STACK_init(BN_STACK *st)
242 st->depth = st->size = 0;
245 static void BN_STACK_finish(BN_STACK *st)
247 OPENSSL_free(st->indexes);
252 static int BN_STACK_push(BN_STACK *st, unsigned int idx)
254 if (st->depth == st->size) {
256 unsigned int newsize =
257 st->size ? (st->size * 3 / 2) : BN_CTX_START_FRAMES;
258 unsigned int *newitems = OPENSSL_malloc(sizeof(*newitems) * newsize);
259 if (newitems == NULL)
262 memcpy(newitems, st->indexes, sizeof(*newitems) * st->depth);
263 OPENSSL_free(st->indexes);
264 st->indexes = newitems;
267 st->indexes[(st->depth)++] = idx;
271 static unsigned int BN_STACK_pop(BN_STACK *st)
273 return st->indexes[--(st->depth)];
280 static void BN_POOL_init(BN_POOL *p)
282 p->head = p->current = p->tail = NULL;
283 p->used = p->size = 0;
286 static void BN_POOL_finish(BN_POOL *p)
292 for (loop = 0, bn = p->head->vals; loop++ < BN_CTX_POOL_SIZE; bn++)
295 p->current = p->head->next;
296 OPENSSL_free(p->head);
297 p->head = p->current;
302 static BIGNUM *BN_POOL_get(BN_POOL *p, int flag)
307 /* Full; allocate a new pool item and link it in. */
308 if (p->used == p->size) {
309 BN_POOL_ITEM *item = OPENSSL_malloc(sizeof(*item));
312 for (loop = 0, bn = item->vals; loop++ < BN_CTX_POOL_SIZE; bn++) {
314 if ((flag & BN_FLG_SECURE) != 0)
315 BN_set_flags(bn, BN_FLG_SECURE);
317 item->prev = p->tail;
321 p->head = p->current = p->tail = item;
323 p->tail->next = item;
327 p->size += BN_CTX_POOL_SIZE;
329 /* Return the first bignum from the new pool */
334 p->current = p->head;
335 else if ((p->used % BN_CTX_POOL_SIZE) == 0)
336 p->current = p->current->next;
337 return p->current->vals + ((p->used++) % BN_CTX_POOL_SIZE);
340 static void BN_POOL_release(BN_POOL *p, unsigned int num)
342 unsigned int offset = (p->used - 1) % BN_CTX_POOL_SIZE;
346 bn_check_top(p->current->vals + offset);
348 offset = BN_CTX_POOL_SIZE - 1;
349 p->current = p->current->prev;