rsa_pk1.c revision 344604
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; 101 102 /* 103 * The format is 104 * 00 || 01 || PS || 00 || D 105 * PS - padding string, at least 8 bytes of FF 106 * D - data. 107 */ 108 109 if (num < 11) 110 return -1; 111 112 /* Accept inputs with and without the leading 0-byte. */ 113 if (num == flen) { 114 if ((*p++) != 0x00) { 115 RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1, 116 RSA_R_INVALID_PADDING); 117 return -1; 118 } 119 flen--; 120 } 121 122 if ((num != (flen + 1)) || (*(p++) != 01)) { 123 RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1, 124 RSA_R_BLOCK_TYPE_IS_NOT_01); 125 return (-1); 126 } 127 128 /* scan over padding data */ 129 j = flen - 1; /* one for type. */ 130 for (i = 0; i < j; i++) { 131 if (*p != 0xff) { /* should decrypt to 0xff */ 132 if (*p == 0) { 133 p++; 134 break; 135 } else { 136 RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1, 137 RSA_R_BAD_FIXED_HEADER_DECRYPT); 138 return (-1); 139 } 140 } 141 p++; 142 } 143 144 if (i == j) { 145 RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1, 146 RSA_R_NULL_BEFORE_BLOCK_MISSING); 147 return (-1); 148 } 149 150 if (i < 8) { 151 RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1, 152 RSA_R_BAD_PAD_BYTE_COUNT); 153 return (-1); 154 } 155 i++; /* Skip over the '\0' */ 156 j -= i; 157 if (j > tlen) { 158 RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1, RSA_R_DATA_TOO_LARGE); 159 return (-1); 160 } 161 memcpy(to, p, (unsigned int)j); 162 163 return (j); 164} 165 166int RSA_padding_add_PKCS1_type_2(unsigned char *to, int tlen, 167 const unsigned char *from, int flen) 168{ 169 int i, j; 170 unsigned char *p; 171 172 if (flen > (tlen - 11)) { 173 RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_TYPE_2, 174 RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE); 175 return (0); 176 } 177 178 p = (unsigned char *)to; 179 180 *(p++) = 0; 181 *(p++) = 2; /* Public Key BT (Block Type) */ 182 183 /* pad out with non-zero random data */ 184 j = tlen - 3 - flen; 185 186 if (RAND_bytes(p, j) <= 0) 187 return (0); 188 for (i = 0; i < j; i++) { 189 if (*p == '\0') 190 do { 191 if (RAND_bytes(p, 1) <= 0) 192 return (0); 193 } while (*p == '\0'); 194 p++; 195 } 196 197 *(p++) = '\0'; 198 199 memcpy(p, from, (unsigned int)flen); 200 return (1); 201} 202 203int RSA_padding_check_PKCS1_type_2(unsigned char *to, int tlen, 204 const unsigned char *from, int flen, 205 int num) 206{ 207 int i; 208 /* |em| is the encoded message, zero-padded to exactly |num| bytes */ 209 unsigned char *em = NULL; 210 unsigned int good, found_zero_byte, mask; 211 int zero_index = 0, msg_index, mlen = -1; 212 213 if (tlen < 0 || flen < 0) 214 return -1; 215 216 /* 217 * PKCS#1 v1.5 decryption. See "PKCS #1 v2.2: RSA Cryptography Standard", 218 * section 7.2.2. 219 */ 220 221 if (flen > num || num < 11) { 222 RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_2, 223 RSA_R_PKCS_DECODING_ERROR); 224 return -1; 225 } 226 227 em = OPENSSL_malloc(num); 228 if (em == NULL) { 229 RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_2, ERR_R_MALLOC_FAILURE); 230 return -1; 231 } 232 /* 233 * Caller is encouraged to pass zero-padded message created with 234 * BN_bn2binpad. Trouble is that since we can't read out of |from|'s 235 * bounds, it's impossible to have an invariant memory access pattern 236 * in case |from| was not zero-padded in advance. 237 */ 238 for (from += flen, em += num, i = 0; i < num; i++) { 239 mask = ~constant_time_is_zero(flen); 240 flen -= 1 & mask; 241 from -= 1 & mask; 242 *--em = *from & mask; 243 } 244 from = em; 245 246 good = constant_time_is_zero(from[0]); 247 good &= constant_time_eq(from[1], 2); 248 249 /* scan over padding data */ 250 found_zero_byte = 0; 251 for (i = 2; i < num; i++) { 252 unsigned int equals0 = constant_time_is_zero(from[i]); 253 254 zero_index = constant_time_select_int(~found_zero_byte & equals0, 255 i, zero_index); 256 found_zero_byte |= equals0; 257 } 258 259 /* 260 * PS must be at least 8 bytes long, and it starts two bytes into |from|. 261 * If we never found a 0-byte, then |zero_index| is 0 and the check 262 * also fails. 263 */ 264 good &= constant_time_ge(zero_index, 2 + 8); 265 266 /* 267 * Skip the zero byte. This is incorrect if we never found a zero-byte 268 * but in this case we also do not copy the message out. 269 */ 270 msg_index = zero_index + 1; 271 mlen = num - msg_index; 272 273 /* 274 * For good measure, do this check in constant time as well. 275 */ 276 good &= constant_time_ge(tlen, mlen); 277 278 /* 279 * Even though we can't fake result's length, we can pretend copying 280 * |tlen| bytes where |mlen| bytes would be real. Last |tlen| of |num| 281 * bytes are viewed as circular buffer with start at |tlen|-|mlen'|, 282 * where |mlen'| is "saturated" |mlen| value. Deducing information 283 * about failure or |mlen| would take attacker's ability to observe 284 * memory access pattern with byte granularity *as it occurs*. It 285 * should be noted that failure is indistinguishable from normal 286 * operation if |tlen| is fixed by protocol. 287 */ 288 tlen = constant_time_select_int(constant_time_lt(num, tlen), num, tlen); 289 msg_index = constant_time_select_int(good, msg_index, num - tlen); 290 mlen = num - msg_index; 291 for (from += msg_index, mask = good, i = 0; i < tlen; i++) { 292 unsigned int equals = constant_time_eq(i, mlen); 293 294 from -= tlen & equals; /* if (i == mlen) rewind */ 295 mask &= mask ^ equals; /* if (i == mlen) mask = 0 */ 296 to[i] = constant_time_select_8(mask, from[i], to[i]); 297 } 298 299 OPENSSL_cleanse(em, num); 300 OPENSSL_free(em); 301 RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_2, RSA_R_PKCS_DECODING_ERROR); 302 err_clear_last_constant_time(1 & good); 303 304 return constant_time_select_int(good, mlen, -1); 305} 306