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 "qemu/bswap.h"
  23 #include "crypto/ivgen-essiv.h"
  24
  25 typedef struct QCryptoIVGenESSIV QCryptoIVGenESSIV;
  26 struct QCryptoIVGenESSIV {
  27     QCryptoCipher *cipher;
  28 };
  29
  30 static int qcrypto_ivgen_essiv_init(QCryptoIVGen *ivgen,
  31                                     const uint8_t *key, size_t nkey,
  32                                     Error **errp)
  33 {
  34     uint8_t *salt;
  35     size_t nhash;
  36     size_t nsalt;
  37     QCryptoIVGenESSIV *essiv = g_new0(QCryptoIVGenESSIV, 1);
  38
  39     /* Not necessarily the same as nkey */
  40     nsalt = qcrypto_cipher_get_key_len(ivgen->cipher);
  41
  42     nhash = qcrypto_hash_digest_len(ivgen->hash);
  43     /* Salt must be larger of hash size or key size */
  44     salt = g_new0(uint8_t, MAX(nhash, nsalt));
  45
  46     if (qcrypto_hash_bytes(ivgen->hash, (const gchar *)key, nkey,
  47                            &salt, &nhash,
  48                            errp) < 0) {
  49         g_free(essiv);
  50         g_free(salt);
  51         return -1;
  52     }
  53
  54     /* Now potentially truncate salt to match cipher key len */
  55     essiv->cipher = qcrypto_cipher_new(ivgen->cipher,
  56                                        QCRYPTO_CIPHER_MODE_ECB,
  57                                        salt, MIN(nhash, nsalt),
  58                                        errp);
  59     if (!essiv->cipher) {
  60         g_free(essiv);
  61         g_free(salt);
  62         return -1;
  63     }
  64
  65     g_free(salt);
  66     ivgen->private = essiv;
  67
  68     return 0;
  69 }
  70
  71 static int qcrypto_ivgen_essiv_calculate(QCryptoIVGen *ivgen,
  72                                          uint64_t sector,
  73                                          uint8_t *iv, size_t niv,
  74                                          Error **errp)
  75 {
  76     QCryptoIVGenESSIV *essiv = ivgen->private;
  77     size_t ndata = qcrypto_cipher_get_block_len(ivgen->cipher);
  78     uint8_t *data = g_new(uint8_t, ndata);
  79
  80     sector = cpu_to_le64(sector);
  81     memcpy(data, (uint8_t *)&sector, MIN(sizeof(sector), ndata));
  82     if (sizeof(sector) < ndata) {
  83         memset(data + sizeof(sector), 0, ndata - sizeof(sector));
  84     }
  85
  86     if (qcrypto_cipher_encrypt(essiv->cipher,
  87                                data,
  88                                data,
  89                                ndata,
  90                                errp) < 0) {
  91         g_free(data);
  92         return -1;
  93     }
  94
  95     if (ndata > niv) {
  96         ndata = niv;
  97     }
  98     memcpy(iv, data, ndata);
  99     if (ndata < niv) {
 100         memset(iv + ndata, 0, niv - ndata);
 101     }
 102     g_free(data);
 103     return 0;
 104 }
 105
 106 static void qcrypto_ivgen_essiv_cleanup(QCryptoIVGen *ivgen)
 107 {
 108     QCryptoIVGenESSIV *essiv = ivgen->private;
 109
 110     qcrypto_cipher_free(essiv->cipher);
 111     g_free(essiv);
 112 }
 113
 114
 115 struct QCryptoIVGenDriver qcrypto_ivgen_essiv = {
 116     .init = qcrypto_ivgen_essiv_init,
 117     .calculate = qcrypto_ivgen_essiv_calculate,
 118     .cleanup = qcrypto_ivgen_essiv_cleanup,
 119 };
 120