1/* crypto/rsa/rsa_pk1.c */ 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 "constant_time_locl.h" 60 61#include <stdio.h> 62#include "cryptlib.h" 63#include <openssl/bn.h> 64#include <openssl/rsa.h> 65#include <openssl/rand.h> 66 67int RSA_padding_add_PKCS1_type_1(unsigned char *to, int tlen, 68 const unsigned char *from, int flen) 69{ 70 int j; 71 unsigned char *p; 72 73 if (flen > (tlen - RSA_PKCS1_PADDING_SIZE)) { 74 RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_TYPE_1, 75 RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE); 76 return (0); 77 } 78 79 p = (unsigned char *)to; 80 81 *(p++) = 0; 82 *(p++) = 1; /* Private Key BT (Block Type) */ 83 84 /* pad out with 0xff data */ 85 j = tlen - 3 - flen; 86 memset(p, 0xff, j); 87 p += j; 88 *(p++) = '\0'; 89 memcpy(p, from, (unsigned int)flen); 90 return (1); 91} 92 93int RSA_padding_check_PKCS1_type_1(unsigned char *to, int tlen, 94 const unsigned char *from, int flen, 95 int num) 96{ 97 int i, j; 98 const unsigned char *p; 99 100 p = from; 101 if ((num != (flen + 1)) || (*(p++) != 01)) { 102 RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1, 103 RSA_R_BLOCK_TYPE_IS_NOT_01); 104 return (-1); 105 } 106 107 /* scan over padding data */ 108 j = flen - 1; /* one for type. */ 109 for (i = 0; i < j; i++) { 110 if (*p != 0xff) { /* should decrypt to 0xff */ 111 if (*p == 0) { 112 p++; 113 break; 114 } else { 115 RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1, 116 RSA_R_BAD_FIXED_HEADER_DECRYPT); 117 return (-1); 118 } 119 } 120 p++; 121 } 122 123 if (i == j) { 124 RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1, 125 RSA_R_NULL_BEFORE_BLOCK_MISSING); 126 return (-1); 127 } 128 129 if (i < 8) { 130 RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1, 131 RSA_R_BAD_PAD_BYTE_COUNT); 132 return (-1); 133 } 134 i++; /* Skip over the '\0' */ 135 j -= i; 136 if (j > tlen) { 137 RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1, RSA_R_DATA_TOO_LARGE); 138 return (-1); 139 } 140 memcpy(to, p, (unsigned int)j); 141 142 return (j); 143} 144 145int RSA_padding_add_PKCS1_type_2(unsigned char *to, int tlen, 146 const unsigned char *from, int flen) 147{ 148 int i, j; 149 unsigned char *p; 150 151 if (flen > (tlen - 11)) { 152 RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_TYPE_2, 153 RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE); 154 return (0); 155 } 156 157 p = (unsigned char *)to; 158 159 *(p++) = 0; 160 *(p++) = 2; /* Public Key BT (Block Type) */ 161 162 /* pad out with non-zero random data */ 163 j = tlen - 3 - flen; 164 165 if (RAND_bytes(p, j) <= 0) 166 return (0); 167 for (i = 0; i < j; i++) { 168 if (*p == '\0') 169 do { 170 if (RAND_bytes(p, 1) <= 0) 171 return (0); 172 } while (*p == '\0'); 173 p++; 174 } 175 176 *(p++) = '\0'; 177 178 memcpy(p, from, (unsigned int)flen); 179 return (1); 180} 181 182int RSA_padding_check_PKCS1_type_2(unsigned char *to, int tlen, 183 const unsigned char *from, int flen, 184 int num) 185{ 186 int i; 187 /* |em| is the encoded message, zero-padded to exactly |num| bytes */ 188 unsigned char *em = NULL; 189 unsigned int good, found_zero_byte; 190 int zero_index = 0, msg_index, mlen = -1; 191 192 if (tlen < 0 || flen < 0) 193 return -1; 194 195 /* 196 * PKCS#1 v1.5 decryption. See "PKCS #1 v2.2: RSA Cryptography Standard", 197 * section 7.2.2. 198 */ 199 200 if (flen > num) 201 goto err; 202 203 if (num < 11) 204 goto err; 205 206 em = OPENSSL_malloc(num); 207 if (em == NULL) { 208 RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_2, ERR_R_MALLOC_FAILURE); 209 return -1; 210 } 211 memset(em, 0, num); 212 /* 213 * Always do this zero-padding copy (even when num == flen) to avoid 214 * leaking that information. The copy still leaks some side-channel 215 * information, but it's impossible to have a fixed memory access 216 * pattern since we can't read out of the bounds of |from|. 217 * 218 * TODO(emilia): Consider porting BN_bn2bin_padded from BoringSSL. 219 */ 220 memcpy(em + num - flen, from, flen); 221 222 good = constant_time_is_zero(em[0]); 223 good &= constant_time_eq(em[1], 2); 224 225 found_zero_byte = 0; 226 for (i = 2; i < num; i++) { 227 unsigned int equals0 = constant_time_is_zero(em[i]); 228 zero_index = 229 constant_time_select_int(~found_zero_byte & equals0, i, 230 zero_index); 231 found_zero_byte |= equals0; 232 } 233 234 /* 235 * PS must be at least 8 bytes long, and it starts two bytes into |em|. 236 * If we never found a 0-byte, then |zero_index| is 0 and the check 237 * also fails. 238 */ 239 good &= constant_time_ge((unsigned int)(zero_index), 2 + 8); 240 241 /* 242 * Skip the zero byte. This is incorrect if we never found a zero-byte 243 * but in this case we also do not copy the message out. 244 */ 245 msg_index = zero_index + 1; 246 mlen = num - msg_index; 247 248 /* 249 * For good measure, do this check in constant time as well; it could 250 * leak something if |tlen| was assuming valid padding. 251 */ 252 good &= constant_time_ge((unsigned int)(tlen), (unsigned int)(mlen)); 253 254 /* 255 * We can't continue in constant-time because we need to copy the result 256 * and we cannot fake its length. This unavoidably leaks timing 257 * information at the API boundary. 258 * TODO(emilia): this could be addressed at the call site, 259 * see BoringSSL commit 0aa0767340baf925bda4804882aab0cb974b2d26. 260 */ 261 if (!good) { 262 mlen = -1; 263 goto err; 264 } 265 266 memcpy(to, em + msg_index, mlen); 267 268 err: 269 if (em != NULL) 270 OPENSSL_free(em); 271 if (mlen == -1) 272 RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_2, 273 RSA_R_PKCS_DECODING_ERROR); 274 return mlen; 275} 276