--- /dev/null
+/*
+ * QEMU Crypto XTS cipher mode
+ *
+ * Copyright (c) 2015-2016 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/>.
+ *
+ * This code is originally derived from public domain / WTFPL code in
+ * LibTomCrypt crytographic library http://libtom.org. The XTS code
+ * was donated by Elliptic Semiconductor Inc (www.ellipticsemi.com)
+ * to the LibTom Projects
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "crypto/xts.h"
+
+static void xts_mult_x(uint8_t *I)
+{
+ int x;
+ uint8_t t, tt;
+
+ for (x = t = 0; x < 16; x++) {
+ tt = I[x] >> 7;
+ I[x] = ((I[x] << 1) | t) & 0xFF;
+ t = tt;
+ }
+ if (tt) {
+ I[0] ^= 0x87;
+ }
+}
+
+
+/**
+ * xts_tweak_uncrypt:
+ * @param ctxt: the cipher context
+ * @param func: the cipher function
+ * @src: buffer providing the cipher text of XTS_BLOCK_SIZE bytes
+ * @dst: buffer to output the plain text of XTS_BLOCK_SIZE bytes
+ * @iv: the initialization vector tweak of XTS_BLOCK_SIZE bytes
+ *
+ * Decrypt data with a tweak
+ */
+static void xts_tweak_decrypt(const void *ctx,
+ xts_cipher_func *func,
+ const uint8_t *src,
+ uint8_t *dst,
+ uint8_t *iv)
+{
+ unsigned long x;
+
+ /* tweak encrypt block i */
+ for (x = 0; x < XTS_BLOCK_SIZE; x++) {
+ dst[x] = src[x] ^ iv[x];
+ }
+
+ func(ctx, XTS_BLOCK_SIZE, dst, dst);
+
+ for (x = 0; x < XTS_BLOCK_SIZE; x++) {
+ dst[x] = dst[x] ^ iv[x];
+ }
+
+ /* LFSR the tweak */
+ xts_mult_x(iv);
+}
+
+
+void xts_decrypt(const void *datactx,
+ const void *tweakctx,
+ xts_cipher_func *encfunc,
+ xts_cipher_func *decfunc,
+ uint8_t *iv,
+ size_t length,
+ uint8_t *dst,
+ const uint8_t *src)
+{
+ uint8_t PP[XTS_BLOCK_SIZE], CC[XTS_BLOCK_SIZE], T[XTS_BLOCK_SIZE];
+ unsigned long i, m, mo, lim;
+
+ /* get number of blocks */
+ m = length >> 4;
+ mo = length & 15;
+
+ /* must have at least one full block */
+ g_assert(m != 0);
+
+ if (mo == 0) {
+ lim = m;
+ } else {
+ lim = m - 1;
+ }
+
+ /* encrypt the iv */
+ encfunc(tweakctx, XTS_BLOCK_SIZE, T, iv);
+
+ for (i = 0; i < lim; i++) {
+ xts_tweak_decrypt(datactx, decfunc, src, dst, T);
+
+ src += XTS_BLOCK_SIZE;
+ dst += XTS_BLOCK_SIZE;
+ }
+
+ /* if length is not a multiple of XTS_BLOCK_SIZE then */
+ if (mo > 0) {
+ memcpy(CC, T, XTS_BLOCK_SIZE);
+ xts_mult_x(CC);
+
+ /* PP = tweak decrypt block m-1 */
+ xts_tweak_decrypt(datactx, decfunc, src, PP, CC);
+
+ /* Pm = first length % XTS_BLOCK_SIZE bytes of PP */
+ for (i = 0; i < mo; i++) {
+ CC[i] = src[XTS_BLOCK_SIZE + i];
+ dst[XTS_BLOCK_SIZE + i] = PP[i];
+ }
+ for (; i < XTS_BLOCK_SIZE; i++) {
+ CC[i] = PP[i];
+ }
+
+ /* Pm-1 = Tweak uncrypt CC */
+ xts_tweak_decrypt(datactx, decfunc, CC, dst, T);
+ }
+
+ /* Decrypt the iv back */
+ decfunc(tweakctx, XTS_BLOCK_SIZE, iv, T);
+}
+
+
+/**
+ * xts_tweak_crypt:
+ * @param ctxt: the cipher context
+ * @param func: the cipher function
+ * @src: buffer providing the plain text of XTS_BLOCK_SIZE bytes
+ * @dst: buffer to output the cipher text of XTS_BLOCK_SIZE bytes
+ * @iv: the initialization vector tweak of XTS_BLOCK_SIZE bytes
+ *
+ * Encrypt data with a tweak
+ */
+static void xts_tweak_encrypt(const void *ctx,
+ xts_cipher_func *func,
+ const uint8_t *src,
+ uint8_t *dst,
+ uint8_t *iv)
+{
+ unsigned long x;
+
+ /* tweak encrypt block i */
+ for (x = 0; x < XTS_BLOCK_SIZE; x++) {
+ dst[x] = src[x] ^ iv[x];
+ }
+
+ func(ctx, XTS_BLOCK_SIZE, dst, dst);
+
+ for (x = 0; x < XTS_BLOCK_SIZE; x++) {
+ dst[x] = dst[x] ^ iv[x];
+ }
+
+ /* LFSR the tweak */
+ xts_mult_x(iv);
+}
+
+
+void xts_encrypt(const void *datactx,
+ const void *tweakctx,
+ xts_cipher_func *encfunc,
+ xts_cipher_func *decfunc,
+ uint8_t *iv,
+ size_t length,
+ uint8_t *dst,
+ const uint8_t *src)
+{
+ uint8_t PP[XTS_BLOCK_SIZE], CC[XTS_BLOCK_SIZE], T[XTS_BLOCK_SIZE];
+ unsigned long i, m, mo, lim;
+
+ /* get number of blocks */
+ m = length >> 4;
+ mo = length & 15;
+
+ /* must have at least one full block */
+ g_assert(m != 0);
+
+ if (mo == 0) {
+ lim = m;
+ } else {
+ lim = m - 1;
+ }
+
+ /* encrypt the iv */
+ encfunc(tweakctx, XTS_BLOCK_SIZE, T, iv);
+
+ for (i = 0; i < lim; i++) {
+ xts_tweak_encrypt(datactx, encfunc, src, dst, T);
+
+ dst += XTS_BLOCK_SIZE;
+ src += XTS_BLOCK_SIZE;
+ }
+
+ /* if length is not a multiple of XTS_BLOCK_SIZE then */
+ if (mo > 0) {
+ /* CC = tweak encrypt block m-1 */
+ xts_tweak_encrypt(datactx, encfunc, src, CC, T);
+
+ /* Cm = first length % XTS_BLOCK_SIZE bytes of CC */
+ for (i = 0; i < mo; i++) {
+ PP[i] = src[XTS_BLOCK_SIZE + i];
+ dst[XTS_BLOCK_SIZE + i] = CC[i];
+ }
+
+ for (; i < XTS_BLOCK_SIZE; i++) {
+ PP[i] = CC[i];
+ }
+
+ /* Cm-1 = Tweak encrypt PP */
+ xts_tweak_encrypt(datactx, encfunc, PP, dst, T);
+ }
+
+ /* Decrypt the iv back */
+ decfunc(tweakctx, XTS_BLOCK_SIZE, iv, T);
+}
Code Review / kvmfornfv.git / blobdiff