1 /* $OpenBSD: rsa_sign.c,v 1.31 2018/09/05 00:55:33 djm 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 "rsa_locl.h" 69 70 /* Size of an SSL signature: MD5+SHA1 */ 71 #define SSL_SIG_LENGTH 36 72 73 static int encode_pkcs1(unsigned char **, int *, int , const unsigned char *, 74 unsigned int); 75 76 /* 77 * encode_pkcs1 encodes a DigestInfo prefix of hash `type' and digest `m', as 78 * described in EMSA-PKCS-v1_5-ENCODE, RFC 8017 section 9. step 2. This 79 * encodes the DigestInfo (T and tLen) but does not add the padding. 80 * 81 * On success, it returns one and sets `*out' to a newly allocated buffer 82 * containing the result and `*out_len' to its length. Freeing `*out' is 83 * the caller's responsibility. Failure is indicated by zero. 84 */ 85 static int 86 encode_pkcs1(unsigned char **out, int *out_len, int type, 87 const unsigned char *m, unsigned int m_len) 88 { 89 X509_SIG sig; 90 X509_ALGOR algor; 91 ASN1_TYPE parameter; 92 ASN1_OCTET_STRING digest; 93 uint8_t *der = NULL; 94 int len; 95 96 sig.algor = &algor; 97 if ((sig.algor->algorithm = OBJ_nid2obj(type)) == NULL) { 98 RSAerror(RSA_R_UNKNOWN_ALGORITHM_TYPE); 99 return 0; 100 } 101 if (sig.algor->algorithm->length == 0) { 102 RSAerror( 103 RSA_R_THE_ASN1_OBJECT_IDENTIFIER_IS_NOT_KNOWN_FOR_THIS_MD); 104 return 0; 105 } 106 parameter.type = V_ASN1_NULL; 107 parameter.value.ptr = NULL; 108 sig.algor->parameter = ¶meter; 109 110 sig.digest = &digest; 111 sig.digest->data = (unsigned char*)m; /* TMP UGLY CAST */ 112 sig.digest->length = m_len; 113 114 if ((len = i2d_X509_SIG(&sig, &der)) < 0) 115 return 0; 116 117 *out = der; 118 *out_len = len; 119 120 return 1; 121 } 122 123 int 124 RSA_sign(int type, const unsigned char *m, unsigned int m_len, 125 unsigned char *sigret, unsigned int *siglen, RSA *rsa) 126 { 127 const unsigned char *encoded = NULL; 128 unsigned char *tmps = NULL; 129 int encrypt_len, encoded_len = 0, ret = 0; 130 131 if ((rsa->flags & RSA_FLAG_SIGN_VER) && rsa->meth->rsa_sign != NULL) 132 return rsa->meth->rsa_sign(type, m, m_len, sigret, siglen, rsa); 133 134 /* Compute the encoded digest. */ 135 if (type == NID_md5_sha1) { 136 /* 137 * NID_md5_sha1 corresponds to the MD5/SHA1 combination in 138 * TLS 1.1 and earlier. It has no DigestInfo wrapper but 139 * otherwise is RSASSA-PKCS-v1.5. 140 */ 141 if (m_len != SSL_SIG_LENGTH) { 142 RSAerror(RSA_R_INVALID_DIGEST_LENGTH); 143 return 0; 144 } 145 encoded_len = SSL_SIG_LENGTH; 146 encoded = m; 147 } else { 148 if (!encode_pkcs1(&tmps, &encoded_len, type, m, m_len)) 149 goto err; 150 encoded = tmps; 151 } 152 if (encoded_len > RSA_size(rsa) - RSA_PKCS1_PADDING_SIZE) { 153 RSAerror(RSA_R_DIGEST_TOO_BIG_FOR_RSA_KEY); 154 goto err; 155 } 156 if ((encrypt_len = RSA_private_encrypt(encoded_len, encoded, sigret, 157 rsa, RSA_PKCS1_PADDING)) <= 0) 158 goto err; 159 160 *siglen = encrypt_len; 161 ret = 1; 162 163 err: 164 freezero(tmps, (size_t)encoded_len); 165 return (ret); 166 } 167 168 /* 169 * int_rsa_verify verifies an RSA signature in `sigbuf' using `rsa'. It may be 170 * called in two modes. If `rm' is NULL, it verifies the signature for the 171 * digest `m'. Otherwise, it recovers the digest from the signature, writing the 172 * digest to `rm' and the length to `*prm_len'. `type' is the NID of the digest 173 * algorithm to use. It returns one on successful verification and zero 174 * otherwise. 175 */ 176 int 177 int_rsa_verify(int type, const unsigned char *m, unsigned int m_len, 178 unsigned char *rm, size_t *prm_len, const unsigned char *sigbuf, 179 size_t siglen, RSA *rsa) 180 { 181 unsigned char *decrypt_buf, *encoded = NULL; 182 int decrypt_len, encoded_len = 0, ret = 0; 183 184 if (siglen != (size_t)RSA_size(rsa)) { 185 RSAerror(RSA_R_WRONG_SIGNATURE_LENGTH); 186 return 0; 187 } 188 189 /* Recover the encoded digest. */ 190 if ((decrypt_buf = malloc(siglen)) == NULL) { 191 RSAerror(ERR_R_MALLOC_FAILURE); 192 goto err; 193 } 194 if ((decrypt_len = RSA_public_decrypt((int)siglen, sigbuf, decrypt_buf, 195 rsa, RSA_PKCS1_PADDING)) <= 0) 196 goto err; 197 198 if (type == NID_md5_sha1) { 199 /* 200 * NID_md5_sha1 corresponds to the MD5/SHA1 combination in 201 * TLS 1.1 and earlier. It has no DigestInfo wrapper but 202 * otherwise is RSASSA-PKCS1-v1_5. 203 */ 204 if (decrypt_len != SSL_SIG_LENGTH) { 205 RSAerror(RSA_R_INVALID_DIGEST_LENGTH); 206 goto err; 207 } 208 209 if (rm != NULL) { 210 memcpy(rm, decrypt_buf, SSL_SIG_LENGTH); 211 *prm_len = SSL_SIG_LENGTH; 212 } else { 213 if (m_len != SSL_SIG_LENGTH) { 214 RSAerror(RSA_R_INVALID_MESSAGE_LENGTH); 215 goto err; 216 } 217 if (timingsafe_bcmp(decrypt_buf, 218 m, SSL_SIG_LENGTH) != 0) { 219 RSAerror(RSA_R_BAD_SIGNATURE); 220 goto err; 221 } 222 } 223 } else { 224 /* 225 * If recovering the digest, extract a digest-sized output from 226 * the end of `decrypt_buf' for `encode_pkcs1', then compare the 227 * decryption output as in a standard verification. 228 */ 229 if (rm != NULL) { 230 const EVP_MD *md; 231 232 if ((md = EVP_get_digestbynid(type)) == NULL) { 233 RSAerror(RSA_R_UNKNOWN_ALGORITHM_TYPE); 234 goto err; 235 } 236 if ((m_len = EVP_MD_size(md)) > (size_t)decrypt_len) { 237 RSAerror(RSA_R_INVALID_DIGEST_LENGTH); 238 goto err; 239 } 240 m = decrypt_buf + decrypt_len - m_len; 241 } 242 243 /* Construct the encoded digest and ensure it matches */ 244 if (!encode_pkcs1(&encoded, &encoded_len, type, m, m_len)) 245 goto err; 246 247 if (encoded_len != decrypt_len || 248 timingsafe_bcmp(encoded, decrypt_buf, encoded_len) != 0) { 249 RSAerror(RSA_R_BAD_SIGNATURE); 250 goto err; 251 } 252 253 /* Output the recovered digest. */ 254 if (rm != NULL) { 255 memcpy(rm, m, m_len); 256 *prm_len = m_len; 257 } 258 } 259 260 ret = 1; 261 err: 262 freezero(encoded, (size_t)encoded_len); 263 freezero(decrypt_buf, siglen); 264 return ret; 265 } 266 267 int 268 RSA_verify(int dtype, const unsigned char *m, unsigned int m_len, 269 const unsigned char *sigbuf, unsigned int siglen, RSA *rsa) 270 { 271 if ((rsa->flags & RSA_FLAG_SIGN_VER) && rsa->meth->rsa_verify) 272 return rsa->meth->rsa_verify(dtype, m, m_len, sigbuf, siglen, 273 rsa); 274 275 return int_rsa_verify(dtype, m, m_len, NULL, NULL, sigbuf, siglen, rsa); 276 } 277