crypto/ivgen-essiv.c

   1 /*
   2  * QEMU Crypto block IV generator - essiv
   3  *
   4  * Copyright (c) 2015-2016 Red Hat, Inc.
   5  *
   6  * This library is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2 of the License, or (at your option) any later version.
  10  *
  11  * This library is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with this library; if not, see <http://www.gnu.org/licenses/>.
  18  *
  19  */
  20
  21 #include "qemu/osdep.h"
  22 #include "crypto/ivgen-essiv.h"
  23
  24 typedef struct QCryptoIVGenESSIV QCryptoIVGenESSIV;
  25 struct QCryptoIVGenESSIV {
  26     QCryptoCipher *cipher;
  27 };
  28
  29 static int qcrypto_ivgen_essiv_init(QCryptoIVGen *ivgen,
  30                                     const uint8_t *key, size_t nkey,
  31                                     Error **errp)
  32 {
  33     uint8_t *salt;
  34     size_t nhash;
  35     size_t nsalt;
  36     QCryptoIVGenESSIV *essiv = g_new0(QCryptoIVGenESSIV, 1);
  37
  38     /* Not necessarily the same as nkey */
  39     nsalt = qcrypto_cipher_get_key_len(ivgen->cipher);
  40
  41     nhash = qcrypto_hash_digest_len(ivgen->hash);
  42     /* Salt must be larger of hash size or key size */
  43     salt = g_new0(uint8_t, MAX(nhash, nsalt));
  44
  45     if (qcrypto_hash_bytes(ivgen->hash, (const gchar *)key, nkey,
  46                            &salt, &nhash,
  47                            errp) < 0) {
  48         g_free(essiv);
  49         return -1;
  50     }
  51
  52     /* Now potentially truncate salt to match cipher key len */
  53     essiv->cipher = qcrypto_cipher_new(ivgen->cipher,
  54                                        QCRYPTO_CIPHER_MODE_ECB,
  55                                        salt, MIN(nhash, nsalt),
  56                                        errp);
  57     if (!essiv->cipher) {
  58         g_free(essiv);
  59         g_free(salt);
  60         return -1;
  61     }
  62
  63     g_free(salt);
  64     ivgen->private = essiv;
  65
  66     return 0;
  67 }
  68
  69 static int qcrypto_ivgen_essiv_calculate(QCryptoIVGen *ivgen,
  70                                          uint64_t sector,
  71                                          uint8_t *iv, size_t niv,
  72                                          Error **errp)
  73 {
  74     QCryptoIVGenESSIV *essiv = ivgen->private;
  75     size_t ndata = qcrypto_cipher_get_block_len(ivgen->cipher);
  76     uint8_t *data = g_new(uint8_t, ndata);
  77
  78     sector = cpu_to_le64(sector);
  79     memcpy(data, (uint8_t *)&sector, ndata);
  80     if (sizeof(sector) < ndata) {
  81         memset(data + sizeof(sector), 0, ndata - sizeof(sector));
  82     }
  83
  84     if (qcrypto_cipher_encrypt(essiv->cipher,
  85                                data,
  86                                data,
  87                                ndata,
  88                                errp) < 0) {
  89         g_free(data);
  90         return -1;
  91     }
  92
  93     if (ndata > niv) {
  94         ndata = niv;
  95     }
  96     memcpy(iv, data, ndata);
  97     if (ndata < niv) {
  98         memset(iv + ndata, 0, niv - ndata);
  99     }
 100     g_free(data);
 101     return 0;
 102 }
 103
 104 static void qcrypto_ivgen_essiv_cleanup(QCryptoIVGen *ivgen)
 105 {
 106     QCryptoIVGenESSIV *essiv = ivgen->private;
 107
 108     qcrypto_cipher_free(essiv->cipher);
 109     g_free(essiv);
 110 }
 111
 112
 113 struct QCryptoIVGenDriver qcrypto_ivgen_essiv = {
 114     .init = qcrypto_ivgen_essiv_init,
 115     .calculate = qcrypto_ivgen_essiv_calculate,
 116     .cleanup = qcrypto_ivgen_essiv_cleanup,
 117 };
 118