1/*
2 * Copyright 1995-2016 The OpenSSL Project Authors. All Rights Reserved.
3 *
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
8 */
9
10#include <stdio.h>
11#include "internal/cryptlib.h"
12#include <openssl/bn.h>
13#include <openssl/rsa.h>
14#include <openssl/objects.h>
15#include <openssl/x509.h>
16#include "crypto/x509.h"
17#include "rsa_local.h"
18
19/* Size of an SSL signature: MD5+SHA1 */
20#define SSL_SIG_LENGTH 36
21
22/*
23 * encode_pkcs1 encodes a DigestInfo prefix of hash |type| and digest |m|, as
24 * described in EMSA-PKCS1-v1_5-ENCODE, RFC 3447 section 9.2 step 2. This
25 * encodes the DigestInfo (T and tLen) but does not add the padding.
26 *
27 * On success, it returns one and sets |*out| to a newly allocated buffer
28 * containing the result and |*out_len| to its length. The caller must free
29 * |*out| with |OPENSSL_free|. Otherwise, it returns zero.
30 */
31static int encode_pkcs1(unsigned char **out, int *out_len, int type,
32 const unsigned char *m, unsigned int m_len)
33{
34 X509_SIG sig;
35 X509_ALGOR algor;
36 ASN1_TYPE parameter;
37 ASN1_OCTET_STRING digest;
38 uint8_t *der = NULL;
39 int len;
40
41 sig.algor = &algor;
42 sig.algor->algorithm = OBJ_nid2obj(type);
43 if (sig.algor->algorithm == NULL) {
44 RSAerr(RSA_F_ENCODE_PKCS1, RSA_R_UNKNOWN_ALGORITHM_TYPE);
45 return 0;
46 }
47 if (OBJ_length(sig.algor->algorithm) == 0) {
48 RSAerr(RSA_F_ENCODE_PKCS1,
49 RSA_R_THE_ASN1_OBJECT_IDENTIFIER_IS_NOT_KNOWN_FOR_THIS_MD);
50 return 0;
51 }
52 parameter.type = V_ASN1_NULL;
53 parameter.value.ptr = NULL;
54 sig.algor->parameter = &parameter;
55
56 sig.digest = &digest;
57 sig.digest->data = (unsigned char *)m;
58 sig.digest->length = m_len;
59
60 len = i2d_X509_SIG(&sig, &der);
61 if (len < 0)
62 return 0;
63
64 *out = der;
65 *out_len = len;
66 return 1;
67}
68
69int RSA_sign(int type, const unsigned char *m, unsigned int m_len,
70 unsigned char *sigret, unsigned int *siglen, RSA *rsa)
71{
72 int encrypt_len, encoded_len = 0, ret = 0;
73 unsigned char *tmps = NULL;
74 const unsigned char *encoded = NULL;
75
76 if (rsa->meth->rsa_sign) {
77 return rsa->meth->rsa_sign(type, m, m_len, sigret, siglen, rsa);
78 }
79
80 /* Compute the encoded digest. */
81 if (type == NID_md5_sha1) {
82 /*
83 * NID_md5_sha1 corresponds to the MD5/SHA1 combination in TLS 1.1 and
84 * earlier. It has no DigestInfo wrapper but otherwise is
85 * RSASSA-PKCS1-v1_5.
86 */
87 if (m_len != SSL_SIG_LENGTH) {
88 RSAerr(RSA_F_RSA_SIGN, RSA_R_INVALID_MESSAGE_LENGTH);
89 return 0;
90 }
91 encoded_len = SSL_SIG_LENGTH;
92 encoded = m;
93 } else {
94 if (!encode_pkcs1(&tmps, &encoded_len, type, m, m_len))
95 goto err;
96 encoded = tmps;
97 }
98
99 if (encoded_len > RSA_size(rsa) - RSA_PKCS1_PADDING_SIZE) {
100 RSAerr(RSA_F_RSA_SIGN, RSA_R_DIGEST_TOO_BIG_FOR_RSA_KEY);
101 goto err;
102 }
103 encrypt_len = RSA_private_encrypt(encoded_len, encoded, sigret, rsa,
104 RSA_PKCS1_PADDING);
105 if (encrypt_len <= 0)
106 goto err;
107
108 *siglen = encrypt_len;
109 ret = 1;
110
111err:
112 OPENSSL_clear_free(tmps, (size_t)encoded_len);
113 return ret;
114}
115
116/*
117 * int_rsa_verify verifies an RSA signature in |sigbuf| using |rsa|. It may be
118 * called in two modes. If |rm| is NULL, it verifies the signature for digest
119 * |m|. Otherwise, it recovers the digest from the signature, writing the digest
120 * to |rm| and the length to |*prm_len|. |type| is the NID of the digest
121 * algorithm to use. It returns one on successful verification and zero
122 * otherwise.
123 */
124int int_rsa_verify(int type, const unsigned char *m, unsigned int m_len,
125 unsigned char *rm, size_t *prm_len,
126 const unsigned char *sigbuf, size_t siglen, RSA *rsa)
127{
128 int decrypt_len, ret = 0, encoded_len = 0;
129 unsigned char *decrypt_buf = NULL, *encoded = NULL;
130
131 if (siglen != (size_t)RSA_size(rsa)) {
132 RSAerr(RSA_F_INT_RSA_VERIFY, RSA_R_WRONG_SIGNATURE_LENGTH);
133 return 0;
134 }
135
136 /* Recover the encoded digest. */
137 decrypt_buf = OPENSSL_malloc(siglen);
138 if (decrypt_buf == NULL) {
139 RSAerr(RSA_F_INT_RSA_VERIFY, ERR_R_MALLOC_FAILURE);
140 goto err;
141 }
142
143 decrypt_len = RSA_public_decrypt((int)siglen, sigbuf, decrypt_buf, rsa,
144 RSA_PKCS1_PADDING);
145 if (decrypt_len <= 0)
146 goto err;
147
148 if (type == NID_md5_sha1) {
149 /*
150 * NID_md5_sha1 corresponds to the MD5/SHA1 combination in TLS 1.1 and
151 * earlier. It has no DigestInfo wrapper but otherwise is
152 * RSASSA-PKCS1-v1_5.
153 */
154 if (decrypt_len != SSL_SIG_LENGTH) {
155 RSAerr(RSA_F_INT_RSA_VERIFY, RSA_R_BAD_SIGNATURE);
156 goto err;
157 }
158
159 if (rm != NULL) {
160 memcpy(rm, decrypt_buf, SSL_SIG_LENGTH);
161 *prm_len = SSL_SIG_LENGTH;
162 } else {
163 if (m_len != SSL_SIG_LENGTH) {
164 RSAerr(RSA_F_INT_RSA_VERIFY, RSA_R_INVALID_MESSAGE_LENGTH);
165 goto err;
166 }
167
168 if (memcmp(decrypt_buf, m, SSL_SIG_LENGTH) != 0) {
169 RSAerr(RSA_F_INT_RSA_VERIFY, RSA_R_BAD_SIGNATURE);
170 goto err;
171 }
172 }
173 } else if (type == NID_mdc2 && decrypt_len == 2 + 16
174 && decrypt_buf[0] == 0x04 && decrypt_buf[1] == 0x10) {
175 /*
176 * Oddball MDC2 case: signature can be OCTET STRING. check for correct
177 * tag and length octets.
178 */
179 if (rm != NULL) {
180 memcpy(rm, decrypt_buf + 2, 16);
181 *prm_len = 16;
182 } else {
183 if (m_len != 16) {
184 RSAerr(RSA_F_INT_RSA_VERIFY, RSA_R_INVALID_MESSAGE_LENGTH);
185 goto err;
186 }
187
188 if (memcmp(m, decrypt_buf + 2, 16) != 0) {
189 RSAerr(RSA_F_INT_RSA_VERIFY, RSA_R_BAD_SIGNATURE);
190 goto err;
191 }
192 }
193 } else {
194 /*
195 * If recovering the digest, extract a digest-sized output from the end
196 * of |decrypt_buf| for |encode_pkcs1|, then compare the decryption
197 * output as in a standard verification.
198 */
199 if (rm != NULL) {
200 const EVP_MD *md = EVP_get_digestbynid(type);
201 if (md == NULL) {
202 RSAerr(RSA_F_INT_RSA_VERIFY, RSA_R_UNKNOWN_ALGORITHM_TYPE);
203 goto err;
204 }
205
206 m_len = EVP_MD_size(md);
207 if (m_len > (size_t)decrypt_len) {
208 RSAerr(RSA_F_INT_RSA_VERIFY, RSA_R_INVALID_DIGEST_LENGTH);
209 goto err;
210 }
211 m = decrypt_buf + decrypt_len - m_len;
212 }
213
214 /* Construct the encoded digest and ensure it matches. */
215 if (!encode_pkcs1(&encoded, &encoded_len, type, m, m_len))
216 goto err;
217
218 if (encoded_len != decrypt_len
219 || memcmp(encoded, decrypt_buf, encoded_len) != 0) {
220 RSAerr(RSA_F_INT_RSA_VERIFY, RSA_R_BAD_SIGNATURE);
221 goto err;
222 }
223
224 /* Output the recovered digest. */
225 if (rm != NULL) {
226 memcpy(rm, m, m_len);
227 *prm_len = m_len;
228 }
229 }
230
231 ret = 1;
232
233err:
234 OPENSSL_clear_free(encoded, (size_t)encoded_len);
235 OPENSSL_clear_free(decrypt_buf, siglen);
236 return ret;
237}
238
239int RSA_verify(int type, const unsigned char *m, unsigned int m_len,
240 const unsigned char *sigbuf, unsigned int siglen, RSA *rsa)
241{
242
243 if (rsa->meth->rsa_verify) {
244 return rsa->meth->rsa_verify(type, m, m_len, sigbuf, siglen, rsa);
245 }
246
247 return int_rsa_verify(type, m, m_len, NULL, NULL, sigbuf, siglen, rsa);
248}
249