crypto/rsa/rsa_pk1.c

   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
  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         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
  93 int 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
 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         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
 182 int 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 }