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diff --git a/src/lib/libcrypto/rsa/rsa_oaep.c b/src/lib/libcrypto/rsa/rsa_oaep.c
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1/* $OpenBSD: rsa_oaep.c,v 1.39 2024/03/26 05:37:28 joshua Exp $ */
2/*
3 * Copyright 1999-2018 The OpenSSL Project Authors. 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
56/* EME-OAEP as defined in RFC 2437 (PKCS #1 v2.0) */
57
58/* See Victor Shoup, "OAEP reconsidered," Nov. 2000,
59 * <URL: http://www.shoup.net/papers/oaep.ps.Z>
60 * for problems with the security proof for the
61 * original OAEP scheme, which EME-OAEP is based on.
62 *
63 * A new proof can be found in E. Fujisaki, T. Okamoto,
64 * D. Pointcheval, J. Stern, "RSA-OEAP is Still Alive!",
65 * Dec. 2000, <URL: http://eprint.iacr.org/2000/061/>.
66 * The new proof has stronger requirements for the
67 * underlying permutation: "partial-one-wayness" instead
68 * of one-wayness. For the RSA function, this is
69 * an equivalent notion.
70 */
71
72#include <stdio.h>
73#include <stdlib.h>
74#include <string.h>
75
76#include <openssl/bn.h>
77#include <openssl/err.h>
78#include <openssl/evp.h>
79#include <openssl/rsa.h>
80#include <openssl/sha.h>
81
82#include "constant_time.h"
83#include "evp_local.h"
84#include "rsa_local.h"
85
86int
87RSA_padding_add_PKCS1_OAEP(unsigned char *to, int tlen,
88 const unsigned char *from, int flen, const unsigned char *param, int plen)
89{
90 return RSA_padding_add_PKCS1_OAEP_mgf1(to, tlen, from, flen, param,
91 plen, NULL, NULL);
92}
93LCRYPTO_ALIAS(RSA_padding_add_PKCS1_OAEP);
94
95int
96RSA_padding_add_PKCS1_OAEP_mgf1(unsigned char *to, int tlen,
97 const unsigned char *from, int flen, const unsigned char *param, int plen,
98 const EVP_MD *md, const EVP_MD *mgf1md)
99{
100 int i, emlen = tlen - 1;
101 unsigned char *db, *seed;
102 unsigned char *dbmask = NULL;
103 unsigned char seedmask[EVP_MAX_MD_SIZE];
104 int mdlen, dbmask_len = 0;
105 int rv = 0;
106
107 if (md == NULL)
108 md = EVP_sha1();
109 if (mgf1md == NULL)
110 mgf1md = md;
111
112 if ((mdlen = EVP_MD_size(md)) <= 0)
113 goto err;
114
115 if (flen > emlen - 2 * mdlen - 1) {
116 RSAerror(RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE);
117 goto err;
118 }
119
120 if (emlen < 2 * mdlen + 1) {
121 RSAerror(RSA_R_KEY_SIZE_TOO_SMALL);
122 goto err;
123 }
124
125 to[0] = 0;
126 seed = to + 1;
127 db = to + mdlen + 1;
128
129 if (!EVP_Digest((void *)param, plen, db, NULL, md, NULL))
130 goto err;
131
132 memset(db + mdlen, 0, emlen - flen - 2 * mdlen - 1);
133 db[emlen - flen - mdlen - 1] = 0x01;
134 memcpy(db + emlen - flen - mdlen, from, flen);
135 arc4random_buf(seed, mdlen);
136
137 dbmask_len = emlen - mdlen;
138 if ((dbmask = malloc(dbmask_len)) == NULL) {
139 RSAerror(ERR_R_MALLOC_FAILURE);
140 goto err;
141 }
142
143 if (PKCS1_MGF1(dbmask, dbmask_len, seed, mdlen, mgf1md) < 0)
144 goto err;
145 for (i = 0; i < dbmask_len; i++)
146 db[i] ^= dbmask[i];
147 if (PKCS1_MGF1(seedmask, mdlen, db, dbmask_len, mgf1md) < 0)
148 goto err;
149 for (i = 0; i < mdlen; i++)
150 seed[i] ^= seedmask[i];
151
152 rv = 1;
153
154 err:
155 explicit_bzero(seedmask, sizeof(seedmask));
156 freezero(dbmask, dbmask_len);
157
158 return rv;
159}
160LCRYPTO_ALIAS(RSA_padding_add_PKCS1_OAEP_mgf1);
161
162int
163RSA_padding_check_PKCS1_OAEP(unsigned char *to, int tlen,
164 const unsigned char *from, int flen, int num, const unsigned char *param,
165 int plen)
166{
167 return RSA_padding_check_PKCS1_OAEP_mgf1(to, tlen, from, flen, num,
168 param, plen, NULL, NULL);
169}
170LCRYPTO_ALIAS(RSA_padding_check_PKCS1_OAEP);
171
172int
173RSA_padding_check_PKCS1_OAEP_mgf1(unsigned char *to, int tlen,
174 const unsigned char *from, int flen, int num, const unsigned char *param,
175 int plen, const EVP_MD *md, const EVP_MD *mgf1md)
176{
177 int i, dblen = 0, mlen = -1, one_index = 0, msg_index;
178 unsigned int good = 0, found_one_byte, mask;
179 const unsigned char *maskedseed, *maskeddb;
180 unsigned char seed[EVP_MAX_MD_SIZE], phash[EVP_MAX_MD_SIZE];
181 unsigned char *db = NULL, *em = NULL;
182 int mdlen;
183
184 if (md == NULL)
185 md = EVP_sha1();
186 if (mgf1md == NULL)
187 mgf1md = md;
188
189 if ((mdlen = EVP_MD_size(md)) <= 0)
190 return -1;
191
192 if (tlen <= 0 || flen <= 0)
193 return -1;
194
195 /*
196 * |num| is the length of the modulus; |flen| is the length of the
197 * encoded message. Therefore, for any |from| that was obtained by
198 * decrypting a ciphertext, we must have |flen| <= |num|. Similarly,
199 * |num| >= 2 * |mdlen| + 2 must hold for the modulus irrespective
200 * of the ciphertext, see PKCS #1 v2.2, section 7.1.2.
201 * This does not leak any side-channel information.
202 */
203 if (num < flen || num < 2 * mdlen + 2) {
204 RSAerror(RSA_R_OAEP_DECODING_ERROR);
205 return -1;
206 }
207
208 dblen = num - mdlen - 1;
209 if ((db = malloc(dblen)) == NULL) {
210 RSAerror(ERR_R_MALLOC_FAILURE);
211 goto cleanup;
212 }
213 if ((em = malloc(num)) == NULL) {
214 RSAerror(ERR_R_MALLOC_FAILURE);
215 goto cleanup;
216 }
217
218 /*
219 * Caller is encouraged to pass zero-padded message created with
220 * BN_bn2binpad. Trouble is that since we can't read out of |from|'s
221 * bounds, it's impossible to have an invariant memory access pattern
222 * in case |from| was not zero-padded in advance.
223 */
224 for (from += flen, em += num, i = 0; i < num; i++) {
225 mask = ~constant_time_is_zero(flen);
226 flen -= 1 & mask;
227 from -= 1 & mask;
228 *--em = *from & mask;
229 }
230
231 /*
232 * The first byte must be zero, however we must not leak if this is
233 * true. See James H. Manger, "A Chosen Ciphertext Attack on RSA
234 * Optimal Asymmetric Encryption Padding (OAEP) [...]", CRYPTO 2001).
235 */
236 good = constant_time_is_zero(em[0]);
237
238 maskedseed = em + 1;
239 maskeddb = em + 1 + mdlen;
240
241 if (PKCS1_MGF1(seed, mdlen, maskeddb, dblen, mgf1md))
242 goto cleanup;
243 for (i = 0; i < mdlen; i++)
244 seed[i] ^= maskedseed[i];
245
246 if (PKCS1_MGF1(db, dblen, seed, mdlen, mgf1md))
247 goto cleanup;
248 for (i = 0; i < dblen; i++)
249 db[i] ^= maskeddb[i];
250
251 if (!EVP_Digest((void *)param, plen, phash, NULL, md, NULL))
252 goto cleanup;
253
254 good &= constant_time_is_zero(timingsafe_memcmp(db, phash, mdlen));
255
256 found_one_byte = 0;
257 for (i = mdlen; i < dblen; i++) {
258 /*
259 * Padding consists of a number of 0-bytes, followed by a 1.
260 */
261 unsigned int equals1 = constant_time_eq(db[i], 1);
262 unsigned int equals0 = constant_time_is_zero(db[i]);
263
264 one_index = constant_time_select_int(~found_one_byte & equals1,
265 i, one_index);
266 found_one_byte |= equals1;
267 good &= (found_one_byte | equals0);
268 }
269
270 good &= found_one_byte;
271
272 /*
273 * At this point |good| is zero unless the plaintext was valid,
274 * so plaintext-awareness ensures timing side-channels are no longer a
275 * concern.
276 */
277 msg_index = one_index + 1;
278 mlen = dblen - msg_index;
279
280 /*
281 * For good measure, do this check in constant time as well.
282 */
283 good &= constant_time_ge(tlen, mlen);
284
285 /*
286 * Even though we can't fake result's length, we can pretend copying
287 * |tlen| bytes where |mlen| bytes would be real. The last |tlen| of
288 * |dblen| bytes are viewed as a circular buffer starting at |tlen|-|mlen'|,
289 * where |mlen'| is the "saturated" |mlen| value. Deducing information
290 * about failure or |mlen| would require an attacker to observe
291 * memory access patterns with byte granularity *as it occurs*. It
292 * should be noted that failure is indistinguishable from normal
293 * operation if |tlen| is fixed by protocol.
294 */
295 tlen = constant_time_select_int(constant_time_lt(dblen - mdlen - 1, tlen),
296 dblen - mdlen - 1, tlen);
297 msg_index = constant_time_select_int(good, msg_index, dblen - tlen);
298 mlen = dblen - msg_index;
299 for (mask = good, i = 0; i < tlen; i++) {
300 unsigned int equals = constant_time_eq(msg_index, dblen);
301
302 msg_index -= tlen & equals; /* rewind at EOF */
303 mask &= ~equals; /* mask = 0 at EOF */
304 to[i] = constant_time_select_8(mask, db[msg_index++], to[i]);
305 }
306
307 /*
308 * To avoid chosen ciphertext attacks, the error message should not
309 * reveal which kind of decoding error happened.
310 */
311 RSAerror(RSA_R_OAEP_DECODING_ERROR);
312 err_clear_last_constant_time(1 & good);
313
314 cleanup:
315 explicit_bzero(seed, sizeof(seed));
316 freezero(db, dblen);
317 freezero(em, num);
318
319 return constant_time_select_int(good, mlen, -1);
320}
321LCRYPTO_ALIAS(RSA_padding_check_PKCS1_OAEP_mgf1);
322
323int
324PKCS1_MGF1(unsigned char *mask, long len, const unsigned char *seed,
325 long seedlen, const EVP_MD *dgst)
326{
327 long i, outlen = 0;
328 unsigned char cnt[4];
329 EVP_MD_CTX *md_ctx;
330 unsigned char md[EVP_MAX_MD_SIZE];
331 int mdlen;
332 int rv = -1;
333
334 if ((md_ctx = EVP_MD_CTX_new()) == NULL)
335 goto err;
336
337 mdlen = EVP_MD_size(dgst);
338 if (mdlen < 0)
339 goto err;
340 for (i = 0; outlen < len; i++) {
341 cnt[0] = (unsigned char)((i >> 24) & 255);
342 cnt[1] = (unsigned char)((i >> 16) & 255);
343 cnt[2] = (unsigned char)((i >> 8)) & 255;
344 cnt[3] = (unsigned char)(i & 255);
345 if (!EVP_DigestInit_ex(md_ctx, dgst, NULL) ||
346 !EVP_DigestUpdate(md_ctx, seed, seedlen) ||
347 !EVP_DigestUpdate(md_ctx, cnt, 4))
348 goto err;
349 if (outlen + mdlen <= len) {
350 if (!EVP_DigestFinal_ex(md_ctx, mask + outlen, NULL))
351 goto err;
352 outlen += mdlen;
353 } else {
354 if (!EVP_DigestFinal_ex(md_ctx, md, NULL))
355 goto err;
356 memcpy(mask + outlen, md, len - outlen);
357 outlen = len;
358 }
359 }
360
361 rv = 0;
362
363 err:
364 EVP_MD_CTX_free(md_ctx);
365
366 return rv;
367}
368LCRYPTO_ALIAS(PKCS1_MGF1);
generated by cgit v1.2.3-55-g6feb (git 2.39.1) at 2025-05-06 23:33:18 +0000