1 /* crypto/rsa/rsa_pk1.c */ 2 /* Copyright (C) 1995-1998 Eric Young (eay (at) cryptsoft.com) 3 * All rights reserved. 4 * 5 * This package is an SSL implementation written 6 * by Eric Young (eay (at) 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 (at) 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 (at) 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 (at) 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 67 int 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 { 75 RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_TYPE_1,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 93 int RSA_padding_check_PKCS1_type_1(unsigned char *to, int tlen, 94 const unsigned char *from, int flen, int num) 95 { 96 int i,j; 97 const unsigned char *p; 98 99 p=from; 100 if ((num != (flen+1)) || (*(p++) != 01)) 101 { 102 RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1,RSA_R_BLOCK_TYPE_IS_NOT_01); 103 return(-1); 104 } 105 106 /* scan over padding data */ 107 j=flen-1; /* one for type. */ 108 for (i=0; i<j; i++) 109 { 110 if (*p != 0xff) /* should decrypt to 0xff */ 111 { 112 if (*p == 0) 113 { p++; break; } 114 else { 115 RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1,RSA_R_BAD_FIXED_HEADER_DECRYPT); 116 return(-1); 117 } 118 } 119 p++; 120 } 121 122 if (i == j) 123 { 124 RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1,RSA_R_NULL_BEFORE_BLOCK_MISSING); 125 return(-1); 126 } 127 128 if (i < 8) 129 { 130 RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1,RSA_R_BAD_PAD_BYTE_COUNT); 131 return(-1); 132 } 133 i++; /* Skip over the '\0' */ 134 j-=i; 135 if (j > tlen) 136 { 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 } 144 145 int 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 { 153 RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_TYPE_2,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 { 169 if (*p == '\0') 170 do { 171 if (RAND_bytes(p,1) <= 0) 172 return(0); 173 } while (*p == '\0'); 174 p++; 175 } 176 177 *(p++)='\0'; 178 179 memcpy(p,from,(unsigned int)flen); 180 return(1); 181 } 182 183 int RSA_padding_check_PKCS1_type_2(unsigned char *to, int tlen, 184 const unsigned char *from, int flen, 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 /* PKCS#1 v1.5 decryption. See "PKCS #1 v2.2: RSA Cryptography 196 * Standard", section 7.2.2. */ 197 198 if (flen > num) 199 goto err; 200 201 if (num < 11) 202 goto err; 203 204 em = OPENSSL_malloc(num); 205 if (em == NULL) 206 { 207 RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_2, ERR_R_MALLOC_FAILURE); 208 return -1; 209 } 210 memset(em, 0, num); 211 /* 212 * Always do this zero-padding copy (even when num == flen) to avoid 213 * leaking that information. The copy still leaks some side-channel 214 * information, but it's impossible to have a fixed memory access 215 * pattern since we can't read out of the bounds of |from|. 216 * 217 * TODO(emilia): Consider porting BN_bn2bin_padded from BoringSSL. 218 */ 219 memcpy(em + num - flen, from, flen); 220 221 good = constant_time_is_zero(em[0]); 222 good &= constant_time_eq(em[1], 2); 223 224 found_zero_byte = 0; 225 for (i = 2; i < num; i++) 226 { 227 unsigned int equals0 = constant_time_is_zero(em[i]); 228 zero_index = constant_time_select_int(~found_zero_byte & equals0, i, zero_index); 229 found_zero_byte |= equals0; 230 } 231 232 /* 233 * PS must be at least 8 bytes long, and it starts two bytes into |em|. 234 * If we never found a 0-byte, then |zero_index| is 0 and the check 235 * also fails. 236 */ 237 good &= constant_time_ge((unsigned int)(zero_index), 2 + 8); 238 239 /* Skip the zero byte. This is incorrect if we never found a zero-byte 240 * but in this case we also do not copy the message out. */ 241 msg_index = zero_index + 1; 242 mlen = num - msg_index; 243 244 /* For good measure, do this check in constant time as well; it could 245 * leak something if |tlen| was assuming valid padding. */ 246 good &= constant_time_ge((unsigned int)(tlen), (unsigned int)(mlen)); 247 248 /* 249 * We can't continue in constant-time because we need to copy the result 250 * and we cannot fake its length. This unavoidably leaks timing 251 * information at the API boundary. 252 * TODO(emilia): this could be addressed at the call site, 253 * see BoringSSL commit 0aa0767340baf925bda4804882aab0cb974b2d26. 254 */ 255 if (!good) 256 { 257 mlen = -1; 258 goto err; 259 } 260 261 memcpy(to, em + msg_index, mlen); 262 263 err: 264 if (em != NULL) 265 OPENSSL_free(em); 266 if (mlen == -1) 267 RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_2, RSA_R_PKCS_DECODING_ERROR); 268 return mlen; 269 } 270
