1 /* $OpenBSD: rsa_sign.c,v 1.33 2021/11/01 20:53:08 tb 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 #include "x509_lcl.h" 70 71 /* Size of an SSL signature: MD5+SHA1 */ 72 #define SSL_SIG_LENGTH 36 73 74 static int encode_pkcs1(unsigned char **, int *, int , const unsigned char *, 75 unsigned int); 76 77 /* 78 * encode_pkcs1 encodes a DigestInfo prefix of hash `type' and digest `m', as 79 * described in EMSA-PKCS-v1_5-ENCODE, RFC 8017 section 9. step 2. This 80 * encodes the DigestInfo (T and tLen) but does not add the padding. 81 * 82 * On success, it returns one and sets `*out' to a newly allocated buffer 83 * containing the result and `*out_len' to its length. Freeing `*out' is 84 * the caller's responsibility. Failure is indicated by zero. 85 */ 86 static int 87 encode_pkcs1(unsigned char **out, int *out_len, int type, 88 const unsigned char *m, unsigned int m_len) 89 { 90 X509_SIG sig; 91 X509_ALGOR algor; 92 ASN1_TYPE parameter; 93 ASN1_OCTET_STRING digest; 94 uint8_t *der = NULL; 95 int len; 96 97 sig.algor = &algor; 98 if ((sig.algor->algorithm = OBJ_nid2obj(type)) == NULL) { 99 RSAerror(RSA_R_UNKNOWN_ALGORITHM_TYPE); 100 return 0; 101 } 102 if (sig.algor->algorithm->length == 0) { 103 RSAerror( 104 RSA_R_THE_ASN1_OBJECT_IDENTIFIER_IS_NOT_KNOWN_FOR_THIS_MD); 105 return 0; 106 } 107 parameter.type = V_ASN1_NULL; 108 parameter.value.ptr = NULL; 109 sig.algor->parameter = ¶meter; 110 111 sig.digest = &digest; 112 sig.digest->data = (unsigned char *)m; /* TMP UGLY CAST */ 113 sig.digest->length = m_len; 114 115 if ((len = i2d_X509_SIG(&sig, &der)) < 0) 116 return 0; 117 118 *out = der; 119 *out_len = len; 120 121 return 1; 122 } 123 124 int 125 RSA_sign(int type, const unsigned char *m, unsigned int m_len, 126 unsigned char *sigret, unsigned int *siglen, RSA *rsa) 127 { 128 const unsigned char *encoded = NULL; 129 unsigned char *tmps = NULL; 130 int encrypt_len, encoded_len = 0, ret = 0; 131 132 if ((rsa->flags & RSA_FLAG_SIGN_VER) && rsa->meth->rsa_sign != NULL) 133 return rsa->meth->rsa_sign(type, m, m_len, sigret, siglen, rsa); 134 135 /* Compute the encoded digest. */ 136 if (type == NID_md5_sha1) { 137 /* 138 * NID_md5_sha1 corresponds to the MD5/SHA1 combination in 139 * TLS 1.1 and earlier. It has no DigestInfo wrapper but 140 * otherwise is RSASSA-PKCS-v1.5. 141 */ 142 if (m_len != SSL_SIG_LENGTH) { 143 RSAerror(RSA_R_INVALID_DIGEST_LENGTH); 144 return 0; 145 } 146 encoded_len = SSL_SIG_LENGTH; 147 encoded = m; 148 } else { 149 if (!encode_pkcs1(&tmps, &encoded_len, type, m, m_len)) 150 goto err; 151 encoded = tmps; 152 } 153 if (encoded_len > RSA_size(rsa) - RSA_PKCS1_PADDING_SIZE) { 154 RSAerror(RSA_R_DIGEST_TOO_BIG_FOR_RSA_KEY); 155 goto err; 156 } 157 if ((encrypt_len = RSA_private_encrypt(encoded_len, encoded, sigret, 158 rsa, RSA_PKCS1_PADDING)) <= 0) 159 goto err; 160 161 *siglen = encrypt_len; 162 ret = 1; 163 164 err: 165 freezero(tmps, (size_t)encoded_len); 166 return (ret); 167 } 168 169 /* 170 * int_rsa_verify verifies an RSA signature in `sigbuf' using `rsa'. It may be 171 * called in two modes. If `rm' is NULL, it verifies the signature for the 172 * digest `m'. Otherwise, it recovers the digest from the signature, writing the 173 * digest to `rm' and the length to `*prm_len'. `type' is the NID of the digest 174 * algorithm to use. It returns one on successful verification and zero 175 * otherwise. 176 */ 177 int 178 int_rsa_verify(int type, const unsigned char *m, unsigned int m_len, 179 unsigned char *rm, size_t *prm_len, const unsigned char *sigbuf, 180 size_t siglen, RSA *rsa) 181 { 182 unsigned char *decrypt_buf, *encoded = NULL; 183 int decrypt_len, encoded_len = 0, ret = 0; 184 185 if (siglen != (size_t)RSA_size(rsa)) { 186 RSAerror(RSA_R_WRONG_SIGNATURE_LENGTH); 187 return 0; 188 } 189 190 /* Recover the encoded digest. */ 191 if ((decrypt_buf = malloc(siglen)) == NULL) { 192 RSAerror(ERR_R_MALLOC_FAILURE); 193 goto err; 194 } 195 if ((decrypt_len = RSA_public_decrypt((int)siglen, sigbuf, decrypt_buf, 196 rsa, RSA_PKCS1_PADDING)) <= 0) 197 goto err; 198 199 if (type == NID_md5_sha1) { 200 /* 201 * NID_md5_sha1 corresponds to the MD5/SHA1 combination in 202 * TLS 1.1 and earlier. It has no DigestInfo wrapper but 203 * otherwise is RSASSA-PKCS1-v1_5. 204 */ 205 if (decrypt_len != SSL_SIG_LENGTH) { 206 RSAerror(RSA_R_INVALID_DIGEST_LENGTH); 207 goto err; 208 } 209 210 if (rm != NULL) { 211 memcpy(rm, decrypt_buf, SSL_SIG_LENGTH); 212 *prm_len = SSL_SIG_LENGTH; 213 } else { 214 if (m_len != SSL_SIG_LENGTH) { 215 RSAerror(RSA_R_INVALID_MESSAGE_LENGTH); 216 goto err; 217 } 218 if (timingsafe_bcmp(decrypt_buf, 219 m, SSL_SIG_LENGTH) != 0) { 220 RSAerror(RSA_R_BAD_SIGNATURE); 221 goto err; 222 } 223 } 224 } else { 225 /* 226 * If recovering the digest, extract a digest-sized output from 227 * the end of `decrypt_buf' for `encode_pkcs1', then compare the 228 * decryption output as in a standard verification. 229 */ 230 if (rm != NULL) { 231 const EVP_MD *md; 232 233 if ((md = EVP_get_digestbynid(type)) == NULL) { 234 RSAerror(RSA_R_UNKNOWN_ALGORITHM_TYPE); 235 goto err; 236 } 237 if ((m_len = EVP_MD_size(md)) > (size_t)decrypt_len) { 238 RSAerror(RSA_R_INVALID_DIGEST_LENGTH); 239 goto err; 240 } 241 m = decrypt_buf + decrypt_len - m_len; 242 } 243 244 /* Construct the encoded digest and ensure it matches */ 245 if (!encode_pkcs1(&encoded, &encoded_len, type, m, m_len)) 246 goto err; 247 248 if (encoded_len != decrypt_len || 249 timingsafe_bcmp(encoded, decrypt_buf, encoded_len) != 0) { 250 RSAerror(RSA_R_BAD_SIGNATURE); 251 goto err; 252 } 253 254 /* Output the recovered digest. */ 255 if (rm != NULL) { 256 memcpy(rm, m, m_len); 257 *prm_len = m_len; 258 } 259 } 260 261 ret = 1; 262 err: 263 freezero(encoded, (size_t)encoded_len); 264 freezero(decrypt_buf, siglen); 265 return ret; 266 } 267 268 int 269 RSA_verify(int dtype, const unsigned char *m, unsigned int m_len, 270 const unsigned char *sigbuf, unsigned int siglen, RSA *rsa) 271 { 272 if ((rsa->flags & RSA_FLAG_SIGN_VER) && rsa->meth->rsa_verify) 273 return rsa->meth->rsa_verify(dtype, m, m_len, sigbuf, siglen, 274 rsa); 275 276 return int_rsa_verify(dtype, m, m_len, NULL, NULL, sigbuf, siglen, rsa); 277 } 278