src/tls/pkcs1.c

   1 /*
   2  * PKCS #1 (RSA Encryption)
   3  * Copyright (c) 2006-2009, Jouni Malinen <j@w1.fi>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License version 2 as
   7  * published by the Free Software Foundation.
   8  *
   9  * Alternatively, this software may be distributed under the terms of BSD
  10  * license.
  11  *
  12  * See README and COPYING for more details.
  13  */
  14
  15 #include "includes.h"
  16
  17 #include "common.h"
  18 #include "rsa.h"
  19 #include "pkcs1.h"
  20
  21
  22 static int pkcs1_generate_encryption_block(u8 block_type, size_t modlen,
  23                                            const u8 *in, size_t inlen,
  24                                            u8 *out, size_t *outlen)
  25 {
  26         size_t ps_len;
  27         u8 *pos;
  28
  29         /*
  30          * PKCS #1 v1.5, 8.1:
  31          *
  32          * EB = 00 || BT || PS || 00 || D
  33          * BT = 00 or 01 for private-key operation; 02 for public-key operation
  34          * PS = k-3-||D||; at least eight octets
  35          * (BT=0: PS=0x00, BT=1: PS=0xff, BT=2: PS=pseudorandom non-zero)
  36          * k = length of modulus in octets (modlen)
  37          */
  38
  39         if (modlen < 12 || modlen > *outlen || inlen > modlen - 11) {
  40                 wpa_printf(MSG_DEBUG, "PKCS #1: %s - Invalid buffer "
  41                            "lengths (modlen=%lu outlen=%lu inlen=%lu)",
  42                            __func__, (unsigned long) modlen,
  43                            (unsigned long) *outlen,
  44                            (unsigned long) inlen);
  45                 return -1;
  46         }
  47
  48         pos = out;
  49         *pos++ = 0x00;
  50         *pos++ = block_type; /* BT */
  51         ps_len = modlen - inlen - 3;
  52         switch (block_type) {
  53         case 0:
  54                 os_memset(pos, 0x00, ps_len);
  55                 pos += ps_len;
  56                 break;
  57         case 1:
  58                 os_memset(pos, 0xff, ps_len);
  59                 pos += ps_len;
  60                 break;
  61         case 2:
  62                 if (os_get_random(pos, ps_len) < 0) {
  63                         wpa_printf(MSG_DEBUG, "PKCS #1: %s - Failed to get "
  64                                    "random data for PS", __func__);
  65                         return -1;
  66                 }
  67                 while (ps_len--) {
  68                         if (*pos == 0x00)
  69                                 *pos = 0x01;
  70                         pos++;
  71                 }
  72                 break;
  73         default:
  74                 wpa_printf(MSG_DEBUG, "PKCS #1: %s - Unsupported block type "
  75                            "%d", __func__, block_type);
  76                 return -1;
  77         }
  78         *pos++ = 0x00;
  79         os_memcpy(pos, in, inlen); /* D */
  80
  81         return 0;
  82 }
  83
  84
  85 int pkcs1_encrypt(int block_type, struct crypto_rsa_key *key,
  86                   int use_private, const u8 *in, size_t inlen,
  87                   u8 *out, size_t *outlen)
  88 {
  89         size_t modlen;
  90
  91         modlen = crypto_rsa_get_modulus_len(key);
  92
  93         if (pkcs1_generate_encryption_block(block_type, modlen, in, inlen,
  94                                             out, outlen) < 0)
  95                 return -1;
  96
  97         return crypto_rsa_exptmod(out, modlen, out, outlen, key, use_private);
  98 }
  99
 100
 101 int pkcs1_v15_private_key_decrypt(struct crypto_rsa_key *key,
 102                                   const u8 *in, size_t inlen,
 103                                   u8 *out, size_t *outlen)
 104 {
 105         int res;
 106         u8 *pos, *end;
 107
 108         res = crypto_rsa_exptmod(in, inlen, out, outlen, key, 1);
 109         if (res)
 110                 return res;
 111
 112         if (*outlen < 2 || out[0] != 0 || out[1] != 2)
 113                 return -1;
 114
 115         /* Skip PS (pseudorandom non-zero octets) */
 116         pos = out + 2;
 117         end = out + *outlen;
 118         while (*pos && pos < end)
 119                 pos++;
 120         if (pos == end)
 121                 return -1;
 122         pos++;
 123
 124         *outlen -= pos - out;
 125
 126         /* Strip PKCS #1 header */
 127         os_memmove(out, pos, *outlen);
 128
 129         return 0;
 130 }
 131
 132
 133 int pkcs1_decrypt_public_key(struct crypto_rsa_key *key,
 134                              const u8 *crypt, size_t crypt_len,
 135                              u8 *plain, size_t *plain_len)
 136 {
 137         size_t len;
 138         u8 *pos;
 139
 140         len = *plain_len;
 141         if (crypto_rsa_exptmod(crypt, crypt_len, plain, &len, key, 0) < 0)
 142                 return -1;
 143
 144         /*
 145          * PKCS #1 v1.5, 8.1:
 146          *
 147          * EB = 00 || BT || PS || 00 || D
 148          * BT = 00 or 01
 149          * PS = k-3-||D|| times (00 if BT=00) or (FF if BT=01)
 150          * k = length of modulus in octets
 151          */
 152
 153         if (len < 3 + 8 + 16 /* min hash len */ ||
 154             plain[0] != 0x00 || (plain[1] != 0x00 && plain[1] != 0x01)) {
 155                 wpa_printf(MSG_INFO, "LibTomCrypt: Invalid signature EB "
 156                            "structure");
 157                 return -1;
 158         }
 159
 160         pos = plain + 3;
 161         if (plain[1] == 0x00) {
 162                 /* BT = 00 */
 163                 if (plain[2] != 0x00) {
 164                         wpa_printf(MSG_INFO, "LibTomCrypt: Invalid signature "
 165                                    "PS (BT=00)");
 166                         return -1;
 167                 }
 168                 while (pos + 1 < plain + len && *pos == 0x00 && pos[1] == 0x00)
 169                         pos++;
 170         } else {
 171                 /* BT = 01 */
 172                 if (plain[2] != 0xff) {
 173                         wpa_printf(MSG_INFO, "LibTomCrypt: Invalid signature "
 174                                    "PS (BT=01)");
 175                         return -1;
 176                 }
 177                 while (pos < plain + len && *pos == 0xff)
 178                         pos++;
 179         }
 180
 181         if (pos - plain - 2 < 8) {
 182                 /* PKCS #1 v1.5, 8.1: At least eight octets long PS */
 183                 wpa_printf(MSG_INFO, "LibTomCrypt: Too short signature "
 184                            "padding");
 185                 return -1;
 186         }
 187
 188         if (pos + 16 /* min hash len */ >= plain + len || *pos != 0x00) {
 189                 wpa_printf(MSG_INFO, "LibTomCrypt: Invalid signature EB "
 190                            "structure (2)");
 191                 return -1;
 192         }
 193         pos++;
 194         len -= pos - plain;
 195
 196         /* Strip PKCS #1 header */
 197         os_memmove(plain, pos, len);
 198         *plain_len = len;
 199
 200         return 0;
 201 }