crypto/afsplit.c

   1 /*
   2  * QEMU Crypto anti forensic information splitter
   3  *
   4  * Copyright (c) 2015-2016 Red Hat, Inc.
   5  *
   6  * Derived from cryptsetup package lib/luks1/af.c
   7  *
   8  * Copyright (C) 2004, Clemens Fruhwirth <clemens@endorphin.org>
   9  * Copyright (C) 2009-2012, Red Hat, Inc. All rights reserved.
  10  *
  11  * This library is free software; you can redistribute it and/or
  12  * modify it under the terms of the GNU General Public License
  13  * as published by the Free Software Foundation; either version 2
  14  * of the License, or (at your option) any later version.
  15  *
  16  * This library is distributed in the hope that it will be useful,
  17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  19  * Lesser General Public License for more details.
  20  *
  21  * You should have received a copy of the GNU Lesser General Public
  22  * License along with this library; if not, see <http://www.gnu.org/licenses/>.
  23  *
  24  */
  25
  26 #include "qemu/osdep.h"
  27 #include "qemu/bswap.h"
  28 #include "crypto/afsplit.h"
  29 #include "crypto/random.h"
  30
  31
  32 static void qcrypto_afsplit_xor(size_t blocklen,
  33                                 const uint8_t *in1,
  34                                 const uint8_t *in2,
  35                                 uint8_t *out)
  36 {
  37     size_t i;
  38     for (i = 0; i < blocklen; i++) {
  39         out[i] = in1[i] ^ in2[i];
  40     }
  41 }
  42
  43
  44 static int qcrypto_afsplit_hash(QCryptoHashAlgorithm hash,
  45                                 size_t blocklen,
  46                                 uint8_t *block,
  47                                 Error **errp)
  48 {
  49     size_t digestlen = qcrypto_hash_digest_len(hash);
  50
  51     size_t hashcount = blocklen / digestlen;
  52     size_t finallen = blocklen % digestlen;
  53     uint32_t i;
  54
  55     if (finallen) {
  56         hashcount++;
  57     } else {
  58         finallen = digestlen;
  59     }
  60
  61     for (i = 0; i < hashcount; i++) {
  62         uint8_t *out = NULL;
  63         size_t outlen = 0;
  64         uint32_t iv = cpu_to_be32(i);
  65         struct iovec in[] = {
  66             { .iov_base = &iv,
  67               .iov_len = sizeof(iv) },
  68             { .iov_base = block + (i * digestlen),
  69               .iov_len = (i == (hashcount - 1)) ? finallen : digestlen },
  70         };
  71
  72         if (qcrypto_hash_bytesv(hash,
  73                                 in,
  74                                 G_N_ELEMENTS(in),
  75                                 &out, &outlen,
  76                                 errp) < 0) {
  77             return -1;
  78         }
  79
  80         assert(outlen == digestlen);
  81         memcpy(block + (i * digestlen), out,
  82                (i == (hashcount - 1)) ? finallen : digestlen);
  83         g_free(out);
  84     }
  85
  86     return 0;
  87 }
  88
  89
  90 int qcrypto_afsplit_encode(QCryptoHashAlgorithm hash,
  91                            size_t blocklen,
  92                            uint32_t stripes,
  93                            const uint8_t *in,
  94                            uint8_t *out,
  95                            Error **errp)
  96 {
  97     uint8_t *block = g_new0(uint8_t, blocklen);
  98     size_t i;
  99     int ret = -1;
 100
 101     for (i = 0; i < (stripes - 1); i++) {
 102         if (qcrypto_random_bytes(out + (i * blocklen), blocklen, errp) < 0) {
 103             goto cleanup;
 104         }
 105
 106         qcrypto_afsplit_xor(blocklen,
 107                             out + (i * blocklen),
 108                             block,
 109                             block);
 110         if (qcrypto_afsplit_hash(hash, blocklen, block,
 111                                  errp) < 0) {
 112             goto cleanup;
 113         }
 114     }
 115     qcrypto_afsplit_xor(blocklen,
 116                         in,
 117                         block,
 118                         out + (i * blocklen));
 119     ret = 0;
 120
 121  cleanup:
 122     g_free(block);
 123     return ret;
 124 }
 125
 126
 127 int qcrypto_afsplit_decode(QCryptoHashAlgorithm hash,
 128                            size_t blocklen,
 129                            uint32_t stripes,
 130                            const uint8_t *in,
 131                            uint8_t *out,
 132                            Error **errp)
 133 {
 134     uint8_t *block = g_new0(uint8_t, blocklen);
 135     size_t i;
 136     int ret = -1;
 137
 138     for (i = 0; i < (stripes - 1); i++) {
 139         qcrypto_afsplit_xor(blocklen,
 140                             in + (i * blocklen),
 141                             block,
 142                             block);
 143         if (qcrypto_afsplit_hash(hash, blocklen, block,
 144                                  errp) < 0) {
 145             goto cleanup;
 146         }
 147     }
 148
 149     qcrypto_afsplit_xor(blocklen,
 150                         in + (i * blocklen),
 151                         block,
 152                         out);
 153
 154     ret = 0;
 155
 156  cleanup:
 157     g_free(block);
 158     return ret;
 159 }