1 /* Written by Ulf Moeller for the OpenSSL project. */
2 /* ====================================================================
3 * Copyright (c) 1998-2004 The OpenSSL Project. All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 *
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 *
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in
14 * the documentation and/or other materials provided with the
15 * distribution.
16 *
17 * 3. All advertising materials mentioning features or use of this
18 * software must display the following acknowledgment:
19 * "This product includes software developed by the OpenSSL Project
20 * for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
21 *
22 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
23 * endorse or promote products derived from this software without
24 * prior written permission. For written permission, please contact
25 * openssl-core@openssl.org.
26 *
27 * 5. Products derived from this software may not be called "OpenSSL"
28 * nor may "OpenSSL" appear in their names without prior written
29 * permission of the OpenSSL Project.
30 *
31 * 6. Redistributions of any form whatsoever must retain the following
32 * acknowledgment:
33 * "This product includes software developed by the OpenSSL Project
34 * for use in the OpenSSL Toolkit (http://www.openssl.org/)"
35 *
36 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
37 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
38 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
39 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
40 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
41 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
42 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
43 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
44 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
45 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
46 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
47 * OF THE POSSIBILITY OF SUCH DAMAGE.
48 * ====================================================================
49 *
50 * This product includes cryptographic software written by Eric Young
51 * (eay@cryptsoft.com). This product includes software written by Tim
52 * Hudson (tjh@cryptsoft.com). */
53
54
55 #include <openssl/bn.h>
56
57 #include <assert.h>
58 #include <string.h>
59
60 #include <openssl/err.h>
61 #include <openssl/mem.h>
62
63 #include "../../internal.h"
64
65
66 // The stack frame info is resizing, set a first-time expansion size;
67 #define BN_CTX_START_FRAMES 32
68
69
70 // BN_STACK
71
72 // A |BN_STACK| is a stack of |size_t| values.
73 typedef struct {
74 // Array of indexes into |ctx->bignums|.
75 size_t *indexes;
76 // Number of stack frames, and the size of the allocated array
77 size_t depth, size;
78 } BN_STACK;
79
80 static void BN_STACK_init(BN_STACK *);
81 static void BN_STACK_cleanup(BN_STACK *);
82 static int BN_STACK_push(BN_STACK *, size_t idx);
83 static size_t BN_STACK_pop(BN_STACK *);
84
85
86 // BN_CTX
87
88 DEFINE_STACK_OF(BIGNUM)
89
90 // The opaque BN_CTX type
91 struct bignum_ctx {
92 // bignums is the stack of |BIGNUM|s managed by this |BN_CTX|.
93 STACK_OF(BIGNUM) *bignums;
94 // stack is the stack of |BN_CTX_start| frames. It is the value of |used| at
95 // the time |BN_CTX_start| was called.
96 BN_STACK stack;
97 // used is the number of |BIGNUM|s from |bignums| that have been used.
98 size_t used;
99 // error is one if any operation on this |BN_CTX| failed. All subsequent
100 // operations will fail.
101 char error;
102 // defer_error is one if an operation on this |BN_CTX| has failed, but no
103 // error has been pushed to the queue yet. This is used to defer errors from
104 // |BN_CTX_start| to |BN_CTX_get|.
105 char defer_error;
106 };
107
BN_CTX_new(void)108 BN_CTX *BN_CTX_new(void) {
109 BN_CTX *ret = OPENSSL_malloc(sizeof(BN_CTX));
110 if (!ret) {
111 return NULL;
112 }
113
114 // Initialise the structure
115 ret->bignums = NULL;
116 BN_STACK_init(&ret->stack);
117 ret->used = 0;
118 ret->error = 0;
119 ret->defer_error = 0;
120 return ret;
121 }
122
BN_CTX_free(BN_CTX * ctx)123 void BN_CTX_free(BN_CTX *ctx) {
124 if (ctx == NULL) {
125 return;
126 }
127
128 // All |BN_CTX_start| calls must be matched with |BN_CTX_end|, otherwise the
129 // function may use more memory than expected, potentially without bound if
130 // done in a loop. Assert that all |BIGNUM|s have been released.
131 assert(ctx->used == 0 || ctx->error);
132 sk_BIGNUM_pop_free(ctx->bignums, BN_free);
133 BN_STACK_cleanup(&ctx->stack);
134 OPENSSL_free(ctx);
135 }
136
BN_CTX_start(BN_CTX * ctx)137 void BN_CTX_start(BN_CTX *ctx) {
138 if (ctx->error) {
139 // Once an operation has failed, |ctx->stack| no longer matches the number
140 // of |BN_CTX_end| calls to come. Do nothing.
141 return;
142 }
143
144 if (!BN_STACK_push(&ctx->stack, ctx->used)) {
145 ctx->error = 1;
146 // |BN_CTX_start| cannot fail, so defer the error to |BN_CTX_get|.
147 ctx->defer_error = 1;
148 }
149 }
150
BN_CTX_get(BN_CTX * ctx)151 BIGNUM *BN_CTX_get(BN_CTX *ctx) {
152 // Once any operation has failed, they all do.
153 if (ctx->error) {
154 if (ctx->defer_error) {
155 OPENSSL_PUT_ERROR(BN, BN_R_TOO_MANY_TEMPORARY_VARIABLES);
156 ctx->defer_error = 0;
157 }
158 return NULL;
159 }
160
161 if (ctx->bignums == NULL) {
162 ctx->bignums = sk_BIGNUM_new_null();
163 if (ctx->bignums == NULL) {
164 ctx->error = 1;
165 return NULL;
166 }
167 }
168
169 if (ctx->used == sk_BIGNUM_num(ctx->bignums)) {
170 BIGNUM *bn = BN_new();
171 if (bn == NULL || !sk_BIGNUM_push(ctx->bignums, bn)) {
172 OPENSSL_PUT_ERROR(BN, BN_R_TOO_MANY_TEMPORARY_VARIABLES);
173 BN_free(bn);
174 ctx->error = 1;
175 return NULL;
176 }
177 }
178
179 BIGNUM *ret = sk_BIGNUM_value(ctx->bignums, ctx->used);
180 BN_zero(ret);
181 // This is bounded by |sk_BIGNUM_num|, so it cannot overflow.
182 ctx->used++;
183 return ret;
184 }
185
BN_CTX_end(BN_CTX * ctx)186 void BN_CTX_end(BN_CTX *ctx) {
187 if (ctx->error) {
188 // Once an operation has failed, |ctx->stack| no longer matches the number
189 // of |BN_CTX_end| calls to come. Do nothing.
190 return;
191 }
192
193 ctx->used = BN_STACK_pop(&ctx->stack);
194 }
195
196
197 // BN_STACK
198
BN_STACK_init(BN_STACK * st)199 static void BN_STACK_init(BN_STACK *st) {
200 st->indexes = NULL;
201 st->depth = st->size = 0;
202 }
203
BN_STACK_cleanup(BN_STACK * st)204 static void BN_STACK_cleanup(BN_STACK *st) {
205 OPENSSL_free(st->indexes);
206 }
207
BN_STACK_push(BN_STACK * st,size_t idx)208 static int BN_STACK_push(BN_STACK *st, size_t idx) {
209 if (st->depth == st->size) {
210 // This function intentionally does not push to the error queue on error.
211 // Error-reporting is deferred to |BN_CTX_get|.
212 size_t new_size = st->size != 0 ? st->size * 3 / 2 : BN_CTX_START_FRAMES;
213 if (new_size <= st->size || new_size > ((size_t)-1) / sizeof(size_t)) {
214 return 0;
215 }
216 size_t *new_indexes =
217 OPENSSL_realloc(st->indexes, new_size * sizeof(size_t));
218 if (new_indexes == NULL) {
219 return 0;
220 }
221 st->indexes = new_indexes;
222 st->size = new_size;
223 }
224
225 st->indexes[st->depth] = idx;
226 st->depth++;
227 return 1;
228 }
229
BN_STACK_pop(BN_STACK * st)230 static size_t BN_STACK_pop(BN_STACK *st) {
231 assert(st->depth > 0);
232 st->depth--;
233 return st->indexes[st->depth];
234 }
235