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qemu/crypto/cipher-gnutls.c.inc
Daniel P. Berrangé 3d2b61ffcd crypto: add gnutls cipher provider 
Add an implementation of the QEMU cipher APIs to the gnutls
crypto backend. XTS support is only available for gnutls
version >= 3.6.8. Since ECB mode is not exposed by gnutls
APIs, we can't use the private XTS code for compatibility.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
2021-07-14 14:15:52 +01:00

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/*
* QEMU Crypto cipher gnutls algorithms
*
* Copyright (c) 2021 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 2.1 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 "cipherpriv.h"
#include <gnutls/crypto.h>
#if GNUTLS_VERSION_NUMBER >= 0x030608
#define QEMU_GNUTLS_XTS
#endif
bool qcrypto_cipher_supports(QCryptoCipherAlgorithm alg,
QCryptoCipherMode mode)
{
switch (mode) {
case QCRYPTO_CIPHER_MODE_ECB:
case QCRYPTO_CIPHER_MODE_CBC:
switch (alg) {
case QCRYPTO_CIPHER_ALG_AES_128:
case QCRYPTO_CIPHER_ALG_AES_192:
case QCRYPTO_CIPHER_ALG_AES_256:
case QCRYPTO_CIPHER_ALG_DES:
case QCRYPTO_CIPHER_ALG_3DES:
return true;
default:
return false;
}
#ifdef QEMU_GNUTLS_XTS
case QCRYPTO_CIPHER_MODE_XTS:
switch (alg) {
case QCRYPTO_CIPHER_ALG_AES_128:
case QCRYPTO_CIPHER_ALG_AES_256:
return true;
default:
return false;
}
#endif
default:
return false;
}
}
typedef struct QCryptoCipherGnutls QCryptoCipherGnutls;
struct QCryptoCipherGnutls {
QCryptoCipher base;
gnutls_cipher_hd_t handle; /* XTS & CBC mode */
gnutls_cipher_algorithm_t galg; /* ECB mode */
guint8 *key; /* ECB mode */
size_t nkey; /* ECB mode */
size_t blocksize;
};
static void
qcrypto_gnutls_cipher_free(QCryptoCipher *cipher)
{
QCryptoCipherGnutls *ctx = container_of(cipher, QCryptoCipherGnutls, base);
g_free(ctx->key);
if (ctx->handle) {
gnutls_cipher_deinit(ctx->handle);
}
g_free(ctx);
}
static int
qcrypto_gnutls_cipher_encrypt(QCryptoCipher *cipher,
const void *in,
void *out,
size_t len,
Error **errp)
{
QCryptoCipherGnutls *ctx = container_of(cipher, QCryptoCipherGnutls, base);
int err;
if (len % ctx->blocksize) {
error_setg(errp, "Length %zu must be a multiple of block size %zu",
len, ctx->blocksize);
return -1;
}
if (ctx->handle) { /* CBC / XTS mode */
err = gnutls_cipher_encrypt2(ctx->handle,
in, len,
out, len);
if (err != 0) {
error_setg(errp, "Cannot encrypt data: %s",
gnutls_strerror(err));
return -1;
}
} else { /* ECB mode very inefficiently faked with CBC */
g_autofree unsigned char *iv = g_new0(unsigned char, ctx->blocksize);
while (len) {
gnutls_cipher_hd_t handle;
gnutls_datum_t gkey = { (unsigned char *)ctx->key, ctx->nkey };
int err = gnutls_cipher_init(&handle, ctx->galg, &gkey, NULL);
if (err != 0) {
error_setg(errp, "Cannot initialize cipher: %s",
gnutls_strerror(err));
return -1;
}
gnutls_cipher_set_iv(handle, iv, ctx->blocksize);
err = gnutls_cipher_encrypt2(handle,
in, ctx->blocksize,
out, ctx->blocksize);
if (err != 0) {
gnutls_cipher_deinit(handle);
error_setg(errp, "Cannot encrypt data: %s",
gnutls_strerror(err));
return -1;
}
gnutls_cipher_deinit(handle);
len -= ctx->blocksize;
in += ctx->blocksize;
out += ctx->blocksize;
}
}
return 0;
}
static int
qcrypto_gnutls_cipher_decrypt(QCryptoCipher *cipher,
const void *in,
void *out,
size_t len,
Error **errp)
{
QCryptoCipherGnutls *ctx = container_of(cipher, QCryptoCipherGnutls, base);
int err;
if (len % ctx->blocksize) {
error_setg(errp, "Length %zu must be a multiple of block size %zu",
len, ctx->blocksize);
return -1;
}
if (ctx->handle) { /* CBC / XTS mode */
err = gnutls_cipher_decrypt2(ctx->handle,
in, len,
out, len);
if (err != 0) {
error_setg(errp, "Cannot decrypt data: %s",
gnutls_strerror(err));
return -1;
}
} else { /* ECB mode very inefficiently faked with CBC */
g_autofree unsigned char *iv = g_new0(unsigned char, ctx->blocksize);
while (len) {
gnutls_cipher_hd_t handle;
gnutls_datum_t gkey = { (unsigned char *)ctx->key, ctx->nkey };
int err = gnutls_cipher_init(&handle, ctx->galg, &gkey, NULL);
if (err != 0) {
error_setg(errp, "Cannot initialize cipher: %s",
gnutls_strerror(err));
return -1;
}
gnutls_cipher_set_iv(handle, iv, ctx->blocksize);
err = gnutls_cipher_decrypt2(handle,
in, ctx->blocksize,
out, ctx->blocksize);
if (err != 0) {
gnutls_cipher_deinit(handle);
error_setg(errp, "Cannot encrypt data: %s",
gnutls_strerror(err));
return -1;
}
gnutls_cipher_deinit(handle);
len -= ctx->blocksize;
in += ctx->blocksize;
out += ctx->blocksize;
}
}
return 0;
}
static int
qcrypto_gnutls_cipher_setiv(QCryptoCipher *cipher,
const uint8_t *iv, size_t niv,
Error **errp)
{
QCryptoCipherGnutls *ctx = container_of(cipher, QCryptoCipherGnutls, base);
if (niv != ctx->blocksize) {
error_setg(errp, "Expected IV size %zu not %zu",
ctx->blocksize, niv);
return -1;
}
gnutls_cipher_set_iv(ctx->handle, (unsigned char *)iv, niv);
return 0;
}
static struct QCryptoCipherDriver gnutls_driver = {
.cipher_encrypt = qcrypto_gnutls_cipher_encrypt,
.cipher_decrypt = qcrypto_gnutls_cipher_decrypt,
.cipher_setiv = qcrypto_gnutls_cipher_setiv,
.cipher_free = qcrypto_gnutls_cipher_free,
};
static QCryptoCipher *qcrypto_cipher_ctx_new(QCryptoCipherAlgorithm alg,
QCryptoCipherMode mode,
const uint8_t *key,
size_t nkey,
Error **errp)
{
QCryptoCipherGnutls *ctx;
gnutls_datum_t gkey = { (unsigned char *)key, nkey };
gnutls_cipher_algorithm_t galg = GNUTLS_CIPHER_UNKNOWN;
int err;
switch (mode) {
#ifdef QEMU_GNUTLS_XTS
case QCRYPTO_CIPHER_MODE_XTS:
switch (alg) {
case QCRYPTO_CIPHER_ALG_AES_128:
galg = GNUTLS_CIPHER_AES_128_XTS;
break;
case QCRYPTO_CIPHER_ALG_AES_256:
galg = GNUTLS_CIPHER_AES_256_XTS;
break;
default:
break;
}
break;
#endif
case QCRYPTO_CIPHER_MODE_ECB:
case QCRYPTO_CIPHER_MODE_CBC:
switch (alg) {
case QCRYPTO_CIPHER_ALG_AES_128:
galg = GNUTLS_CIPHER_AES_128_CBC;
break;
case QCRYPTO_CIPHER_ALG_AES_192:
galg = GNUTLS_CIPHER_AES_192_CBC;
break;
case QCRYPTO_CIPHER_ALG_AES_256:
galg = GNUTLS_CIPHER_AES_256_CBC;
break;
case QCRYPTO_CIPHER_ALG_DES:
galg = GNUTLS_CIPHER_DES_CBC;
break;
case QCRYPTO_CIPHER_ALG_3DES:
galg = GNUTLS_CIPHER_3DES_CBC;
break;
default:
break;
}
break;
default:
break;
}
if (galg == GNUTLS_CIPHER_UNKNOWN) {
error_setg(errp, "Unsupported cipher algorithm %s with %s mode",
QCryptoCipherAlgorithm_str(alg),
QCryptoCipherMode_str(mode));
return NULL;
}
if (!qcrypto_cipher_validate_key_length(alg, mode, nkey, errp)) {
return NULL;
}
ctx = g_new0(QCryptoCipherGnutls, 1);
ctx->base.driver = &gnutls_driver;
if (mode == QCRYPTO_CIPHER_MODE_ECB) {
ctx->key = g_new0(guint8, nkey);
memcpy(ctx->key, key, nkey);
ctx->nkey = nkey;
ctx->galg = galg;
} else {
err = gnutls_cipher_init(&ctx->handle, galg, &gkey, NULL);
if (err != 0) {
error_setg(errp, "Cannot initialize cipher: %s",
gnutls_strerror(err));
goto error;
}
}
if (alg == QCRYPTO_CIPHER_ALG_DES ||
alg == QCRYPTO_CIPHER_ALG_3DES)
ctx->blocksize = 8;
else
ctx->blocksize = 16;
/*
* Our API contract for requires iv to be optional
* but nettle gets unhappy when called by gnutls
* in this case, so we just force set a default
* all-zeros IV, to match behaviour of other backends.
*/
if (mode != QCRYPTO_CIPHER_MODE_ECB) {
g_autofree unsigned char *iv = g_new0(unsigned char, ctx->blocksize);
gnutls_cipher_set_iv(ctx->handle, iv, ctx->blocksize);
}
return &ctx->base;
error:
qcrypto_gnutls_cipher_free(&ctx->base);
return NULL;
}
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