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 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 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 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 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