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crypto: add support for anti-forensic split algorithm

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The LUKS format specifies an anti-forensic split algorithm which
is used to artificially expand the size of the key material on
disk. This is an implementation of that algorithm.

Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
This commit is contained in:
Daniel P. Berrange 2015-10-23 16:14:25 +01:00
parent cb730894ae
commit 5a95e0fccd
6 changed files with 490 additions and 0 deletions
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1
crypto/Makefile.objs
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@ -17,6 +17,7 @@ crypto-obj-y += ivgen.o
crypto-obj-y += ivgen-essiv.o
crypto-obj-y += ivgen-plain.o
crypto-obj-y += ivgen-plain64.o
crypto-obj-y += afsplit.o
# Let the userspace emulators avoid linking gnutls/etc
crypto-aes-obj-y = aes.o

158
crypto/afsplit.c Normal file
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@ -0,0 +1,158 @@
/*
* QEMU Crypto anti forensic information splitter
*
* Copyright (c) 2015-2016 Red Hat, Inc.
*
* Derived from cryptsetup package lib/luks1/af.c
*
* Copyright (C) 2004, Clemens Fruhwirth <clemens@endorphin.org>
* Copyright (C) 2009-2012, Red Hat, Inc. All rights reserved.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU 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/afsplit.h"
#include "crypto/random.h"
static void qcrypto_afsplit_xor(size_t blocklen,
const uint8_t *in1,
const uint8_t *in2,
uint8_t *out)
{
size_t i;
for (i = 0; i < blocklen; i++) {
out[i] = in1[i] ^ in2[i];
}
}
static int qcrypto_afsplit_hash(QCryptoHashAlgorithm hash,
size_t blocklen,
uint8_t *block,
Error **errp)
{
size_t digestlen = qcrypto_hash_digest_len(hash);
size_t hashcount = blocklen / digestlen;
size_t finallen = blocklen % digestlen;
uint32_t i;
if (finallen) {
hashcount++;
} else {
finallen = digestlen;
}
for (i = 0; i < hashcount; i++) {
uint8_t *out = NULL;
size_t outlen = 0;
uint32_t iv = cpu_to_be32(i);
struct iovec in[] = {
{ .iov_base = &iv,
.iov_len = sizeof(iv) },
{ .iov_base = block + (i * digestlen),
.iov_len = (i == (hashcount - 1)) ? finallen : digestlen },
};
if (qcrypto_hash_bytesv(hash,
in,
G_N_ELEMENTS(in),
&out, &outlen,
errp) < 0) {
return -1;
}
assert(outlen == digestlen);
memcpy(block + (i * digestlen), out,
(i == (hashcount - 1)) ? finallen : digestlen);
g_free(out);
}
return 0;
}
int qcrypto_afsplit_encode(QCryptoHashAlgorithm hash,
size_t blocklen,
uint32_t stripes,
const uint8_t *in,
uint8_t *out,
Error **errp)
{
uint8_t *block = g_new0(uint8_t, blocklen);
size_t i;
int ret = -1;
for (i = 0; i < (stripes - 1); i++) {
if (qcrypto_random_bytes(out + (i * blocklen), blocklen, errp) < 0) {
goto cleanup;
}
qcrypto_afsplit_xor(blocklen,
out + (i * blocklen),
block,
block);
if (qcrypto_afsplit_hash(hash, blocklen, block,
errp) < 0) {
goto cleanup;
}
}
qcrypto_afsplit_xor(blocklen,
in,
block,
out + (i * blocklen));
ret = 0;
cleanup:
g_free(block);
return ret;
}
int qcrypto_afsplit_decode(QCryptoHashAlgorithm hash,
size_t blocklen,
uint32_t stripes,
const uint8_t *in,
uint8_t *out,
Error **errp)
{
uint8_t *block = g_new0(uint8_t, blocklen);
size_t i;
int ret = -1;
for (i = 0; i < (stripes - 1); i++) {
qcrypto_afsplit_xor(blocklen,
in + (i * blocklen),
block,
block);
if (qcrypto_afsplit_hash(hash, blocklen, block,
errp) < 0) {
goto cleanup;
}
}
qcrypto_afsplit_xor(blocklen,
in + (i * blocklen),
block,
out);
ret = 0;
cleanup:
g_free(block);
return ret;
}

135
include/crypto/afsplit.h Normal file
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@ -0,0 +1,135 @@
/*
* QEMU Crypto anti forensic information splitter
*
* 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 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/>.
*
*/
#ifndef QCRYPTO_AFSPLIT_H__
#define QCRYPTO_AFSPLIT_H__
#include "crypto/hash.h"
/**
* This module implements the anti-forensic splitter that is specified
* as part of the LUKS format:
*
* http://clemens.endorphin.org/cryptography
* http://clemens.endorphin.org/TKS1-draft.pdf
*
* The core idea is to take a short piece of data (key material)
* and process it to expand it to a much larger piece of data.
* The expansion process is reversible, to obtain the original
* short data. The key property of the expansion is that if any
* byte in the larger data set is changed / missing, it should be
* impossible to recreate the original short data.
*
* <example>
* <title>Creating a large split key for storage</title>
* <programlisting>
* size_t nkey = 32;
* uint32_t stripes = 32768; // To produce a 1 MB split key
* uint8_t *masterkey = ....a 32-byte AES key...
* uint8_t *splitkey;
*
* splitkey = g_new0(uint8_t, nkey * stripes);
*
* if (qcrypto_afsplit_encode(QCRYPTO_HASH_ALG_SHA256,
* nkey, stripes,
* masterkey, splitkey, errp) < 0) {
* g_free(splitkey);
* g_free(masterkey);
* return -1;
* }
*
* ...store splitkey somewhere...
*
* g_free(splitkey);
* g_free(masterkey);
* </programlisting>
* </example>
*
* <example>
* <title>Retrieving a master key from storage</title>
* <programlisting>
* size_t nkey = 32;
* uint32_t stripes = 32768; // To produce a 1 MB split key
* uint8_t *masterkey;
* uint8_t *splitkey = .... read in 1 MB of data...
*
* masterkey = g_new0(uint8_t, nkey);
*
* if (qcrypto_afsplit_decode(QCRYPTO_HASH_ALG_SHA256,
* nkey, stripes,
* splitkey, masterkey, errp) < 0) {
* g_free(splitkey);
* g_free(masterkey);
* return -1;
* }
*
* ..decrypt data with masterkey...
*
* g_free(splitkey);
* g_free(masterkey);
* </programlisting>
* </example>
*/
/**
* qcrypto_afsplit_encode:
* @hash: the hash algorithm to use for data expansion
* @blocklen: the size of @in in bytes
* @stripes: the number of times to expand @in in size
* @in: the master key to be expanded in size
* @out: preallocated buffer to hold the split key
* @errp: pointer to a NULL-initialized error object
*
* Split the data in @in, which is @blocklen bytes in
* size, to form a larger piece of data @out, which is
* @blocklen * @stripes bytes in size.
*
* Returns: 0 on success, -1 on error;
*/
int qcrypto_afsplit_encode(QCryptoHashAlgorithm hash,
size_t blocklen,
uint32_t stripes,
const uint8_t *in,
uint8_t *out,
Error **errp);
/**
* qcrypto_afsplit_decode:
* @hash: the hash algorithm to use for data compression
* @blocklen: the size of @out in bytes
* @stripes: the number of times to decrease @in in size
* @in: the split key to be recombined
* @out: preallocated buffer to hold the master key
* @errp: pointer to a NULL-initialized error object
*
* Join the data in @in, which is @blocklen * @stripes
* bytes in size, to form the original small piece of
* data @out, which is @blocklen bytes in size.
*
* Returns: 0 on success, -1 on error;
*/
int qcrypto_afsplit_decode(QCryptoHashAlgorithm hash,
size_t blocklen,
uint32_t stripes,
const uint8_t *in,
uint8_t *out,
Error **errp);
#endif /* QCRYPTO_AFSPLIT_H__ */

1
tests/.gitignore vendored
View File

@ -12,6 +12,7 @@ test-base64
test-bitops
test-blockjob-txn
test-coroutine
test-crypto-afsplit
test-crypto-cipher
test-crypto-hash
test-crypto-ivgen

2
tests/Makefile
View File

@ -94,6 +94,7 @@ check-unit-y += tests/test-io-channel-buffer$(EXESUF)
check-unit-y += tests/test-base64$(EXESUF)
check-unit-$(if $(CONFIG_NETTLE),y,$(CONFIG_GCRYPT_KDF)) += tests/test-crypto-pbkdf$(EXESUF)
check-unit-y += tests/test-crypto-ivgen$(EXESUF)
check-unit-y += tests/test-crypto-afsplit$(EXESUF)
check-block-$(CONFIG_POSIX) += tests/qemu-iotests-quick.sh
@ -500,6 +501,7 @@ tests/test-io-channel-buffer$(EXESUF): tests/test-io-channel-buffer.o \
tests/io-channel-helpers.o $(test-io-obj-y)
tests/test-crypto-pbkdf$(EXESUF): tests/test-crypto-pbkdf.o $(test-crypto-obj-y)
tests/test-crypto-ivgen$(EXESUF): tests/test-crypto-ivgen.o $(test-crypto-obj-y)
tests/test-crypto-afsplit$(EXESUF): tests/test-crypto-afsplit.o $(test-crypto-obj-y)
libqos-obj-y = tests/libqos/pci.o tests/libqos/fw_cfg.o tests/libqos/malloc.o
libqos-obj-y += tests/libqos/i2c.o tests/libqos/libqos.o

193
tests/test-crypto-afsplit.c Normal file
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@ -0,0 +1,193 @@
/*
* QEMU Crypto anti-forensic splitter
*
* 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/>.
*
*/
#include "qemu/osdep.h"
#include "crypto/init.h"
#include "crypto/afsplit.h"
typedef struct QCryptoAFSplitTestData QCryptoAFSplitTestData;
struct QCryptoAFSplitTestData {
const char *path;
QCryptoHashAlgorithm hash;
uint32_t stripes;
size_t blocklen;
const uint8_t *key;
const uint8_t *splitkey;
};
static QCryptoAFSplitTestData test_data[] = {
{
.path = "/crypto/afsplit/sha256/5",
.hash = QCRYPTO_HASH_ALG_SHA256,
.stripes = 5,
.blocklen = 32,
.key = (const uint8_t *)
"\x00\x01\x02\x03\x04\x05\x06\x07"
"\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f"
"\xa0\xa1\xa2\xa3\xa4\xa5\xa6\xa7"
"\xa8\xa9\xaa\xab\xac\xad\xae\xaf",
.splitkey = (const uint8_t *)
"\xfd\xd2\x73\xb1\x7d\x99\x93\x34"
"\x70\xde\xfa\x07\xc5\xac\x58\xd2"
"\x30\x67\x2f\x1a\x35\x43\x60\x7d"
"\x77\x02\xdb\x62\x3c\xcb\x2c\x33"
"\x48\x08\xb6\xf1\x7c\xa3\x20\xa0"
"\xad\x2d\x4c\xf3\xcd\x18\x6f\x53"
"\xf9\xe8\xe7\x59\x27\x3c\xa9\x54"
"\x61\x87\xb3\xaf\xf6\xf7\x7e\x64"
"\x86\xaa\x89\x7f\x1f\x9f\xdb\x86"
"\xf4\xa2\x16\xff\xa3\x4f\x8c\xa1"
"\x59\xc4\x23\x34\x28\xc4\x77\x71"
"\x83\xd4\xcd\x8e\x89\x1b\xc7\xc5"
"\xae\x4d\xa9\xcd\xc9\x72\x85\x70"
"\x13\x68\x52\x83\xfc\xb8\x11\x72"
"\xba\x3d\xc6\x4a\x28\xfa\xe2\x86"
"\x7b\x27\xab\x58\xe1\xa4\xca\xf6"
"\x9e\xbc\xfe\x0c\x92\x79\xb3\xec"
"\x1c\x5f\x79\x3b\x0d\x1e\xaa\x1a"
"\x77\x0f\x70\x19\x4b\xc8\x80\xee"
"\x27\x7c\x6e\x4a\x91\x96\x5c\xf4"
},
{
.path = "/crypto/afsplit/sha256/5000",
.hash = QCRYPTO_HASH_ALG_SHA256,
.stripes = 5000,
.blocklen = 16,
.key = (const uint8_t *)
"\x00\x01\x02\x03\x04\x05\x06\x07"
"\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f",
},
{
.path = "/crypto/afsplit/sha1/1000",
.hash = QCRYPTO_HASH_ALG_SHA1,
.stripes = 1000,
.blocklen = 32,
.key = (const uint8_t *)
"\x00\x01\x02\x03\x04\x05\x06\x07"
"\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f"
"\xa0\xa1\xa2\xa3\xa4\xa5\xa6\xa7"
"\xa8\xa9\xaa\xab\xac\xad\xae\xaf",
},
{
.path = "/crypto/afsplit/sha256/big",
.hash = QCRYPTO_HASH_ALG_SHA256,
.stripes = 1000,
.blocklen = 64,
.key = (const uint8_t *)
"\x00\x01\x02\x03\x04\x05\x06\x07"
"\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f"
"\x00\x01\x02\x03\x04\x05\x06\x07"
"\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f"
"\x00\x01\x02\x03\x04\x05\x06\x07"
"\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f"
"\x00\x01\x02\x03\x04\x05\x06\x07"
"\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f",
},
};
static inline char hex(int i)
{
if (i < 10) {
return '0' + i;
}
return 'a' + (i - 10);
}
static char *hex_string(const uint8_t *bytes,
size_t len)
{
char *hexstr = g_new0(char, len * 2 + 1);
size_t i;
for (i = 0; i < len; i++) {
hexstr[i * 2] = hex((bytes[i] >> 4) & 0xf);
hexstr[i * 2 + 1] = hex(bytes[i] & 0xf);
}
hexstr[len * 2] = '\0';
return hexstr;
}
static void test_afsplit(const void *opaque)
{
const QCryptoAFSplitTestData *data = opaque;
size_t splitlen = data->blocklen * data->stripes;
uint8_t *splitkey = g_new0(uint8_t, splitlen);
uint8_t *key = g_new0(uint8_t, data->blocklen);
gchar *expect, *actual;
/* First time we round-trip the key */
qcrypto_afsplit_encode(data->hash,
data->blocklen, data->stripes,
data->key, splitkey,
&error_abort);
qcrypto_afsplit_decode(data->hash,
data->blocklen, data->stripes,
splitkey, key,
&error_abort);
expect = hex_string(data->key, data->blocklen);
actual = hex_string(key, data->blocklen);
g_assert_cmpstr(actual, ==, expect);
g_free(actual);
g_free(expect);
/* Second time we merely try decoding a previous split */
if (data->splitkey) {
memset(key, 0, data->blocklen);
qcrypto_afsplit_decode(data->hash,
data->blocklen, data->stripes,
data->splitkey, key,
&error_abort);
expect = hex_string(data->key, data->blocklen);
actual = hex_string(key, data->blocklen);
g_assert_cmpstr(actual, ==, expect);
g_free(actual);
g_free(expect);
}
g_free(key);
g_free(splitkey);
}
int main(int argc, char **argv)
{
size_t i;
g_test_init(&argc, &argv, NULL);
g_assert(qcrypto_init(NULL) == 0);
for (i = 0; i < G_N_ELEMENTS(test_data); i++) {
if (!qcrypto_hash_supports(test_data[i].hash)) {
continue;
}
g_test_add_data_func(test_data[i].path, &test_data[i], test_afsplit);
}
return g_test_run();
}