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qemu/crypto/cipher-gcrypt.c
Daniel P. Berrange eaec903c5b crypto: wire up XTS mode for cipher APIs 
Introduce 'XTS' as a permitted mode for the cipher APIs.
With XTS the key provided must be twice the size of the
key normally required for any given algorithm. This is
because the key will be split into two pieces for use
in XTS mode.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
2016-03-17 14:41:15 +00:00

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/*
* QEMU Crypto cipher libgcrypt algorithms
*
* Copyright (c) 2015 Red Hat, Inc.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, see <http://www.gnu.org/licenses/>.
*
*/
#include "qemu/osdep.h"
#include "crypto/xts.h"
#include <gcrypt.h>
bool qcrypto_cipher_supports(QCryptoCipherAlgorithm alg)
{
switch (alg) {
case QCRYPTO_CIPHER_ALG_DES_RFB:
case QCRYPTO_CIPHER_ALG_AES_128:
case QCRYPTO_CIPHER_ALG_AES_192:
case QCRYPTO_CIPHER_ALG_AES_256:
case QCRYPTO_CIPHER_ALG_CAST5_128:
case QCRYPTO_CIPHER_ALG_SERPENT_128:
case QCRYPTO_CIPHER_ALG_SERPENT_192:
case QCRYPTO_CIPHER_ALG_SERPENT_256:
case QCRYPTO_CIPHER_ALG_TWOFISH_128:
case QCRYPTO_CIPHER_ALG_TWOFISH_256:
return true;
default:
return false;
}
}
typedef struct QCryptoCipherGcrypt QCryptoCipherGcrypt;
struct QCryptoCipherGcrypt {
gcry_cipher_hd_t handle;
gcry_cipher_hd_t tweakhandle;
size_t blocksize;
uint8_t *iv;
};
QCryptoCipher *qcrypto_cipher_new(QCryptoCipherAlgorithm alg,
QCryptoCipherMode mode,
const uint8_t *key, size_t nkey,
Error **errp)
{
QCryptoCipher *cipher;
QCryptoCipherGcrypt *ctx;
gcry_error_t err;
int gcryalg, gcrymode;
switch (mode) {
case QCRYPTO_CIPHER_MODE_ECB:
case QCRYPTO_CIPHER_MODE_XTS:
gcrymode = GCRY_CIPHER_MODE_ECB;
break;
case QCRYPTO_CIPHER_MODE_CBC:
gcrymode = GCRY_CIPHER_MODE_CBC;
break;
default:
error_setg(errp, "Unsupported cipher mode %d", mode);
return NULL;
}
if (!qcrypto_cipher_validate_key_length(alg, mode, nkey, errp)) {
return NULL;
}
switch (alg) {
case QCRYPTO_CIPHER_ALG_DES_RFB:
gcryalg = GCRY_CIPHER_DES;
break;
case QCRYPTO_CIPHER_ALG_AES_128:
gcryalg = GCRY_CIPHER_AES128;
break;
case QCRYPTO_CIPHER_ALG_AES_192:
gcryalg = GCRY_CIPHER_AES192;
break;
case QCRYPTO_CIPHER_ALG_AES_256:
gcryalg = GCRY_CIPHER_AES256;
break;
case QCRYPTO_CIPHER_ALG_CAST5_128:
gcryalg = GCRY_CIPHER_CAST5;
break;
case QCRYPTO_CIPHER_ALG_SERPENT_128:
gcryalg = GCRY_CIPHER_SERPENT128;
break;
case QCRYPTO_CIPHER_ALG_SERPENT_192:
gcryalg = GCRY_CIPHER_SERPENT192;
break;
case QCRYPTO_CIPHER_ALG_SERPENT_256:
gcryalg = GCRY_CIPHER_SERPENT256;
break;
case QCRYPTO_CIPHER_ALG_TWOFISH_128:
gcryalg = GCRY_CIPHER_TWOFISH128;
break;
case QCRYPTO_CIPHER_ALG_TWOFISH_256:
gcryalg = GCRY_CIPHER_TWOFISH;
break;
default:
error_setg(errp, "Unsupported cipher algorithm %d", alg);
return NULL;
}
cipher = g_new0(QCryptoCipher, 1);
cipher->alg = alg;
cipher->mode = mode;
ctx = g_new0(QCryptoCipherGcrypt, 1);
err = gcry_cipher_open(&ctx->handle, gcryalg, gcrymode, 0);
if (err != 0) {
error_setg(errp, "Cannot initialize cipher: %s",
gcry_strerror(err));
goto error;
}
if (cipher->mode == QCRYPTO_CIPHER_MODE_XTS) {
err = gcry_cipher_open(&ctx->tweakhandle, gcryalg, gcrymode, 0);
if (err != 0) {
error_setg(errp, "Cannot initialize cipher: %s",
gcry_strerror(err));
goto error;
}
}
if (cipher->alg == QCRYPTO_CIPHER_ALG_DES_RFB) {
/* We're using standard DES cipher from gcrypt, so we need
* to munge the key so that the results are the same as the
* bizarre RFB variant of DES :-)
*/
uint8_t *rfbkey = qcrypto_cipher_munge_des_rfb_key(key, nkey);
err = gcry_cipher_setkey(ctx->handle, rfbkey, nkey);
g_free(rfbkey);
ctx->blocksize = 8;
} else {
if (cipher->mode == QCRYPTO_CIPHER_MODE_XTS) {
nkey /= 2;
err = gcry_cipher_setkey(ctx->handle, key, nkey);
if (err != 0) {
error_setg(errp, "Cannot set key: %s",
gcry_strerror(err));
goto error;
}
err = gcry_cipher_setkey(ctx->tweakhandle, key + nkey, nkey);
} else {
err = gcry_cipher_setkey(ctx->handle, key, nkey);
}
if (err != 0) {
error_setg(errp, "Cannot set key: %s",
gcry_strerror(err));
goto error;
}
switch (cipher->alg) {
case QCRYPTO_CIPHER_ALG_AES_128:
case QCRYPTO_CIPHER_ALG_AES_192:
case QCRYPTO_CIPHER_ALG_AES_256:
case QCRYPTO_CIPHER_ALG_SERPENT_128:
case QCRYPTO_CIPHER_ALG_SERPENT_192:
case QCRYPTO_CIPHER_ALG_SERPENT_256:
case QCRYPTO_CIPHER_ALG_TWOFISH_128:
case QCRYPTO_CIPHER_ALG_TWOFISH_256:
ctx->blocksize = 16;
break;
case QCRYPTO_CIPHER_ALG_CAST5_128:
ctx->blocksize = 8;
break;
default:
g_assert_not_reached();
}
}
if (cipher->mode == QCRYPTO_CIPHER_MODE_XTS) {
ctx->iv = g_new0(uint8_t, ctx->blocksize);
}
cipher->opaque = ctx;
return cipher;
error:
gcry_cipher_close(ctx->handle);
if (cipher->mode == QCRYPTO_CIPHER_MODE_XTS) {
gcry_cipher_close(ctx->tweakhandle);
}
g_free(ctx);
g_free(cipher);
return NULL;
}
void qcrypto_cipher_free(QCryptoCipher *cipher)
{
QCryptoCipherGcrypt *ctx;
if (!cipher) {
return;
}
ctx = cipher->opaque;
gcry_cipher_close(ctx->handle);
if (cipher->mode == QCRYPTO_CIPHER_MODE_XTS) {
gcry_cipher_close(ctx->tweakhandle);
}
g_free(ctx->iv);
g_free(ctx);
g_free(cipher);
}
static void qcrypto_gcrypt_xts_encrypt(const void *ctx,
size_t length,
uint8_t *dst,
const uint8_t *src)
{
gcry_error_t err;
err = gcry_cipher_encrypt((gcry_cipher_hd_t)ctx, dst, length, src, length);
g_assert(err == 0);
}
static void qcrypto_gcrypt_xts_decrypt(const void *ctx,
size_t length,
uint8_t *dst,
const uint8_t *src)
{
gcry_error_t err;
err = gcry_cipher_decrypt((gcry_cipher_hd_t)ctx, dst, length, src, length);
g_assert(err == 0);
}
int qcrypto_cipher_encrypt(QCryptoCipher *cipher,
const void *in,
void *out,
size_t len,
Error **errp)
{
QCryptoCipherGcrypt *ctx = cipher->opaque;
gcry_error_t err;
if (len % ctx->blocksize) {
error_setg(errp, "Length %zu must be a multiple of block size %zu",
len, ctx->blocksize);
return -1;
}
if (cipher->mode == QCRYPTO_CIPHER_MODE_XTS) {
xts_encrypt(ctx->handle, ctx->tweakhandle,
qcrypto_gcrypt_xts_encrypt,
qcrypto_gcrypt_xts_decrypt,
ctx->iv, len, out, in);
} else {
err = gcry_cipher_encrypt(ctx->handle,
out, len,
in, len);
if (err != 0) {
error_setg(errp, "Cannot encrypt data: %s",
gcry_strerror(err));
return -1;
}
}
return 0;
}
int qcrypto_cipher_decrypt(QCryptoCipher *cipher,
const void *in,
void *out,
size_t len,
Error **errp)
{
QCryptoCipherGcrypt *ctx = cipher->opaque;
gcry_error_t err;
if (len % ctx->blocksize) {
error_setg(errp, "Length %zu must be a multiple of block size %zu",
len, ctx->blocksize);
return -1;
}
if (cipher->mode == QCRYPTO_CIPHER_MODE_XTS) {
xts_decrypt(ctx->handle, ctx->tweakhandle,
qcrypto_gcrypt_xts_encrypt,
qcrypto_gcrypt_xts_decrypt,
ctx->iv, len, out, in);
} else {
err = gcry_cipher_decrypt(ctx->handle,
out, len,
in, len);
if (err != 0) {
error_setg(errp, "Cannot decrypt data: %s",
gcry_strerror(err));
return -1;
}
}
return 0;
}
int qcrypto_cipher_setiv(QCryptoCipher *cipher,
const uint8_t *iv, size_t niv,
Error **errp)
{
QCryptoCipherGcrypt *ctx = cipher->opaque;
gcry_error_t err;
if (niv != ctx->blocksize) {
error_setg(errp, "Expected IV size %zu not %zu",
ctx->blocksize, niv);
return -1;
}
if (ctx->iv) {
memcpy(ctx->iv, iv, niv);
} else {
gcry_cipher_reset(ctx->handle);
err = gcry_cipher_setiv(ctx->handle, iv, niv);
if (err != 0) {
error_setg(errp, "Cannot set IV: %s",
gcry_strerror(err));
return -1;
}
}
return 0;
}
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