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 "qapi/error.h"
  23 #include "qemu/bswap.h"
  24 #include "crypto/ivgen-essiv.h"
  25
  26 typedef struct QCryptoIVGenESSIV QCryptoIVGenESSIV;
  27 struct QCryptoIVGenESSIV {
  28     QCryptoCipher *cipher;
  29 };
  30
  31 static int qcrypto_ivgen_essiv_init(QCryptoIVGen *ivgen,
  32                                     const uint8_t *key, size_t nkey,
  33                                     Error **errp)
  34 {
  35     uint8_t *salt;
  36     size_t nhash;
  37     size_t nsalt;
  38     QCryptoIVGenESSIV *essiv = g_new0(QCryptoIVGenESSIV, 1);
  39
  40     /* Not necessarily the same as nkey */
  41     nsalt = qcrypto_cipher_get_key_len(ivgen->cipher);
  42
  43     nhash = qcrypto_hash_digest_len(ivgen->hash);
  44     /* Salt must be larger of hash size or key size */
  45     salt = g_new0(uint8_t, MAX(nhash, nsalt));
  46
  47     if (qcrypto_hash_bytes(ivgen->hash, (const gchar *)key, nkey,
  48                            &salt, &nhash,
  49                            errp) < 0) {
  50         g_free(essiv);
  51         g_free(salt);
  52         return -1;
  53     }
  54
  55     /* Now potentially truncate salt to match cipher key len */
  56     essiv->cipher = qcrypto_cipher_new(ivgen->cipher,
  57                                        QCRYPTO_CIPHER_MODE_ECB,
  58                                        salt, MIN(nhash, nsalt),
  59                                        errp);
  60     if (!essiv->cipher) {
  61         g_free(essiv);
  62         g_free(salt);
  63         return -1;
  64     }
  65
  66     g_free(salt);
  67     ivgen->private = essiv;
  68
  69     return 0;
  70 }
  71
  72 static int qcrypto_ivgen_essiv_calculate(QCryptoIVGen *ivgen,
  73                                          uint64_t sector,
  74                                          uint8_t *iv, size_t niv,
  75                                          Error **errp)
  76 {
  77     QCryptoIVGenESSIV *essiv = ivgen->private;
  78     size_t ndata = qcrypto_cipher_get_block_len(ivgen->cipher);
  79     uint8_t *data = g_new(uint8_t, ndata);
  80
  81     sector = cpu_to_le64(sector);
  82     memcpy(data, (uint8_t *)&sector, MIN(sizeof(sector), ndata));
  83     if (sizeof(sector) < ndata) {
  84         memset(data + sizeof(sector), 0, ndata - sizeof(sector));
  85     }
  86
  87     if (qcrypto_cipher_encrypt(essiv->cipher,
  88                                data,
  89                                data,
  90                                ndata,
  91                                errp) < 0) {
  92         g_free(data);
  93         return -1;
  94     }
  95
  96     if (ndata > niv) {
  97         ndata = niv;
  98     }
  99     memcpy(iv, data, ndata);
 100     if (ndata < niv) {
 101         memset(iv + ndata, 0, niv - ndata);
 102     }
 103     g_free(data);
 104     return 0;
 105 }
 106
 107 static void qcrypto_ivgen_essiv_cleanup(QCryptoIVGen *ivgen)
 108 {
 109     QCryptoIVGenESSIV *essiv = ivgen->private;
 110
 111     qcrypto_cipher_free(essiv->cipher);
 112     g_free(essiv);
 113 }
 114
 115
 116 struct QCryptoIVGenDriver qcrypto_ivgen_essiv = {
 117     .init = qcrypto_ivgen_essiv_init,
 118     .calculate = qcrypto_ivgen_essiv_calculate,
 119     .cleanup = qcrypto_ivgen_essiv_cleanup,
 120 };
 121