1 /* $OpenBSD: rsa_sign.c,v 1.36 2023/07/08 12:26:45 beck Exp $ */
2 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
3 * All rights reserved.
4 *
5 * This package is an SSL implementation written
6 * by Eric Young (eay@cryptsoft.com).
7 * The implementation was written so as to conform with Netscapes SSL.
8 *
9 * This library is free for commercial and non-commercial use as long as
10 * the following conditions are aheared to. The following conditions
11 * apply to all code found in this distribution, be it the RC4, RSA,
12 * lhash, DES, etc., code; not just the SSL code. The SSL documentation
13 * included with this distribution is covered by the same copyright terms
14 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
15 *
16 * Copyright remains Eric Young's, and as such any Copyright notices in
17 * the code are not to be removed.
18 * If this package is used in a product, Eric Young should be given attribution
19 * as the author of the parts of the library used.
20 * This can be in the form of a textual message at program startup or
21 * in documentation (online or textual) provided with the package.
22 *
23 * Redistribution and use in source and binary forms, with or without
24 * modification, are permitted provided that the following conditions
25 * are met:
26 * 1. Redistributions of source code must retain the copyright
27 * notice, this list of conditions and the following disclaimer.
28 * 2. Redistributions in binary form must reproduce the above copyright
29 * notice, this list of conditions and the following disclaimer in the
30 * documentation and/or other materials provided with the distribution.
31 * 3. All advertising materials mentioning features or use of this software
32 * must display the following acknowledgement:
33 * "This product includes cryptographic software written by
34 * Eric Young (eay@cryptsoft.com)"
35 * The word 'cryptographic' can be left out if the rouines from the library
36 * being used are not cryptographic related :-).
37 * 4. If you include any Windows specific code (or a derivative thereof) from
38 * the apps directory (application code) you must include an acknowledgement:
39 * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
40 *
41 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
42 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
43 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
44 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
45 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
46 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
47 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
48 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
49 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
50 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
51 * SUCH DAMAGE.
52 *
53 * The licence and distribution terms for any publically available version or
54 * derivative of this code cannot be changed. i.e. this code cannot simply be
55 * copied and put under another distribution licence
56 * [including the GNU Public Licence.]
57 */
58
59 #include <stdio.h>
60 #include <string.h>
61
62 #include <openssl/bn.h>
63 #include <openssl/err.h>
64 #include <openssl/objects.h>
65 #include <openssl/rsa.h>
66 #include <openssl/x509.h>
67
68 #include "asn1_local.h"
69 #include "rsa_local.h"
70 #include "x509_local.h"
71
72 /* Size of an SSL signature: MD5+SHA1 */
73 #define SSL_SIG_LENGTH 36
74
75 static int encode_pkcs1(unsigned char **, int *, int , const unsigned char *,
76 unsigned int);
77
78 /*
79 * encode_pkcs1 encodes a DigestInfo prefix of hash `type' and digest `m', as
80 * described in EMSA-PKCS-v1_5-ENCODE, RFC 8017 section 9. step 2. This
81 * encodes the DigestInfo (T and tLen) but does not add the padding.
82 *
83 * On success, it returns one and sets `*out' to a newly allocated buffer
84 * containing the result and `*out_len' to its length. Freeing `*out' is
85 * the caller's responsibility. Failure is indicated by zero.
86 */
87 static int
encode_pkcs1(unsigned char ** out,int * out_len,int type,const unsigned char * m,unsigned int m_len)88 encode_pkcs1(unsigned char **out, int *out_len, int type,
89 const unsigned char *m, unsigned int m_len)
90 {
91 X509_SIG sig;
92 X509_ALGOR algor;
93 ASN1_TYPE parameter;
94 ASN1_OCTET_STRING digest;
95 uint8_t *der = NULL;
96 int len;
97
98 sig.algor = &algor;
99 if ((sig.algor->algorithm = OBJ_nid2obj(type)) == NULL) {
100 RSAerror(RSA_R_UNKNOWN_ALGORITHM_TYPE);
101 return 0;
102 }
103 if (sig.algor->algorithm->length == 0) {
104 RSAerror(
105 RSA_R_THE_ASN1_OBJECT_IDENTIFIER_IS_NOT_KNOWN_FOR_THIS_MD);
106 return 0;
107 }
108 parameter.type = V_ASN1_NULL;
109 parameter.value.ptr = NULL;
110 sig.algor->parameter = ¶meter;
111
112 sig.digest = &digest;
113 sig.digest->data = (unsigned char *)m; /* TMP UGLY CAST */
114 sig.digest->length = m_len;
115
116 if ((len = i2d_X509_SIG(&sig, &der)) < 0)
117 return 0;
118
119 *out = der;
120 *out_len = len;
121
122 return 1;
123 }
124
125 int
RSA_sign(int type,const unsigned char * m,unsigned int m_len,unsigned char * sigret,unsigned int * siglen,RSA * rsa)126 RSA_sign(int type, const unsigned char *m, unsigned int m_len,
127 unsigned char *sigret, unsigned int *siglen, RSA *rsa)
128 {
129 const unsigned char *encoded = NULL;
130 unsigned char *tmps = NULL;
131 int encrypt_len, encoded_len = 0, ret = 0;
132
133 if ((rsa->flags & RSA_FLAG_SIGN_VER) && rsa->meth->rsa_sign != NULL)
134 return rsa->meth->rsa_sign(type, m, m_len, sigret, siglen, rsa);
135
136 /* Compute the encoded digest. */
137 if (type == NID_md5_sha1) {
138 /*
139 * NID_md5_sha1 corresponds to the MD5/SHA1 combination in
140 * TLS 1.1 and earlier. It has no DigestInfo wrapper but
141 * otherwise is RSASSA-PKCS-v1.5.
142 */
143 if (m_len != SSL_SIG_LENGTH) {
144 RSAerror(RSA_R_INVALID_DIGEST_LENGTH);
145 return 0;
146 }
147 encoded_len = SSL_SIG_LENGTH;
148 encoded = m;
149 } else {
150 if (!encode_pkcs1(&tmps, &encoded_len, type, m, m_len))
151 goto err;
152 encoded = tmps;
153 }
154 if (encoded_len > RSA_size(rsa) - RSA_PKCS1_PADDING_SIZE) {
155 RSAerror(RSA_R_DIGEST_TOO_BIG_FOR_RSA_KEY);
156 goto err;
157 }
158 if ((encrypt_len = RSA_private_encrypt(encoded_len, encoded, sigret,
159 rsa, RSA_PKCS1_PADDING)) <= 0)
160 goto err;
161
162 *siglen = encrypt_len;
163 ret = 1;
164
165 err:
166 freezero(tmps, (size_t)encoded_len);
167 return (ret);
168 }
169 LCRYPTO_ALIAS(RSA_sign);
170
171 /*
172 * int_rsa_verify verifies an RSA signature in `sigbuf' using `rsa'. It may be
173 * called in two modes. If `rm' is NULL, it verifies the signature for the
174 * digest `m'. Otherwise, it recovers the digest from the signature, writing the
175 * digest to `rm' and the length to `*prm_len'. `type' is the NID of the digest
176 * algorithm to use. It returns one on successful verification and zero
177 * otherwise.
178 */
179 int
int_rsa_verify(int type,const unsigned char * m,unsigned int m_len,unsigned char * rm,size_t * prm_len,const unsigned char * sigbuf,size_t siglen,RSA * rsa)180 int_rsa_verify(int type, const unsigned char *m, unsigned int m_len,
181 unsigned char *rm, size_t *prm_len, const unsigned char *sigbuf,
182 size_t siglen, RSA *rsa)
183 {
184 unsigned char *decrypt_buf, *encoded = NULL;
185 int decrypt_len, encoded_len = 0, ret = 0;
186
187 if (siglen != (size_t)RSA_size(rsa)) {
188 RSAerror(RSA_R_WRONG_SIGNATURE_LENGTH);
189 return 0;
190 }
191
192 /* Recover the encoded digest. */
193 if ((decrypt_buf = malloc(siglen)) == NULL) {
194 RSAerror(ERR_R_MALLOC_FAILURE);
195 goto err;
196 }
197 if ((decrypt_len = RSA_public_decrypt((int)siglen, sigbuf, decrypt_buf,
198 rsa, RSA_PKCS1_PADDING)) <= 0)
199 goto err;
200
201 if (type == NID_md5_sha1) {
202 /*
203 * NID_md5_sha1 corresponds to the MD5/SHA1 combination in
204 * TLS 1.1 and earlier. It has no DigestInfo wrapper but
205 * otherwise is RSASSA-PKCS1-v1_5.
206 */
207 if (decrypt_len != SSL_SIG_LENGTH) {
208 RSAerror(RSA_R_INVALID_DIGEST_LENGTH);
209 goto err;
210 }
211
212 if (rm != NULL) {
213 memcpy(rm, decrypt_buf, SSL_SIG_LENGTH);
214 *prm_len = SSL_SIG_LENGTH;
215 } else {
216 if (m_len != SSL_SIG_LENGTH) {
217 RSAerror(RSA_R_INVALID_MESSAGE_LENGTH);
218 goto err;
219 }
220 if (timingsafe_bcmp(decrypt_buf,
221 m, SSL_SIG_LENGTH) != 0) {
222 RSAerror(RSA_R_BAD_SIGNATURE);
223 goto err;
224 }
225 }
226 } else {
227 /*
228 * If recovering the digest, extract a digest-sized output from
229 * the end of `decrypt_buf' for `encode_pkcs1', then compare the
230 * decryption output as in a standard verification.
231 */
232 if (rm != NULL) {
233 const EVP_MD *md;
234
235 if ((md = EVP_get_digestbynid(type)) == NULL) {
236 RSAerror(RSA_R_UNKNOWN_ALGORITHM_TYPE);
237 goto err;
238 }
239 if ((m_len = EVP_MD_size(md)) > (size_t)decrypt_len) {
240 RSAerror(RSA_R_INVALID_DIGEST_LENGTH);
241 goto err;
242 }
243 m = decrypt_buf + decrypt_len - m_len;
244 }
245
246 /* Construct the encoded digest and ensure it matches */
247 if (!encode_pkcs1(&encoded, &encoded_len, type, m, m_len))
248 goto err;
249
250 if (encoded_len != decrypt_len ||
251 timingsafe_bcmp(encoded, decrypt_buf, encoded_len) != 0) {
252 RSAerror(RSA_R_BAD_SIGNATURE);
253 goto err;
254 }
255
256 /* Output the recovered digest. */
257 if (rm != NULL) {
258 memcpy(rm, m, m_len);
259 *prm_len = m_len;
260 }
261 }
262
263 ret = 1;
264 err:
265 freezero(encoded, (size_t)encoded_len);
266 freezero(decrypt_buf, siglen);
267 return ret;
268 }
269
270 int
RSA_verify(int dtype,const unsigned char * m,unsigned int m_len,const unsigned char * sigbuf,unsigned int siglen,RSA * rsa)271 RSA_verify(int dtype, const unsigned char *m, unsigned int m_len,
272 const unsigned char *sigbuf, unsigned int siglen, RSA *rsa)
273 {
274 if ((rsa->flags & RSA_FLAG_SIGN_VER) && rsa->meth->rsa_verify)
275 return rsa->meth->rsa_verify(dtype, m, m_len, sigbuf, siglen,
276 rsa);
277
278 return int_rsa_verify(dtype, m, m_len, NULL, NULL, sigbuf, siglen, rsa);
279 }
280 LCRYPTO_ALIAS(RSA_verify);
281