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Implement AES-XTS mode

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XTS mode is fully known as "xor-encrypt-xor with ciphertext-stealing".
This is the generalization of the XEX mode.
This implementation is limited to an 8-bits (1 byte) boundary, which
doesn't seem to be what was thought considering some test vectors [1].

This commit comes with tests, extracted from [1], and benchmarks.
Although, benchmarks aren't really nice here, as they work with a buffer
of a multiple of 16 bytes, which isn't a challenge for XTS compared to
XEX.

[1] http://csrc.nist.gov/groups/STM/cavp/documents/aes/XTSTestVectors.zip
This commit is contained in:
Aorimn 2016-06-09 23:22:58 +02:00 committed by Jaeden Amero
parent 380162c34c
commit 5f77801ac3
8 changed files with 4483 additions and 5 deletions
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28
include/mbedtls/aes.h
View file

@ -237,6 +237,34 @@ int mbedtls_aes_crypt_xex( mbedtls_aes_context *crypt_ctx,
unsigned char *output );
#endif /* MBEDTLS_CIPHER_MODE_XEX */
#if defined(MBEDTLS_CIPHER_MODE_XTS)
/**
* \brief AES-XTS buffer encryption/decryption
* Length should be greater or equal than the block size (16
* bytes, 128 bits)
*
* Warning: The bits_length parameter must given be in bits, not bytes like the
* other modes
*
* \param crypt_ctx AES context for encrypting data
* \param tweak_ctx AES context for xor-ing with data
* \param mode MBEDTLS_AES_ENCRYPT or MBEDTLS_AES_DECRYPT
* \param bits_length length of the input data (in bits)
* \param iv initialization vector
* \param input buffer holding the input data
* \param output buffer holding the output data
*
* \return 0 if successful, or MBEDTLS_ERR_AES_INVALID_INPUT_LENGTH
*/
int mbedtls_aes_crypt_xts( mbedtls_aes_context *crypt_ctx,
mbedtls_aes_context *tweak_ctx,
int mode,
size_t bits_length,
unsigned char iv[16],
const unsigned char *input,
unsigned char *output );
#endif /* MBEDTLS_CIPHER_MODE_XTS */
#if defined(MBEDTLS_CIPHER_MODE_CFB)
/**
* \brief This function performs an AES-CFB128 encryption or decryption

8
include/mbedtls/config.h
View file

@ -508,6 +508,14 @@
*/
#define MBEDTLS_CIPHER_MODE_XEX
/**
* \def MBEDTLS_CIPHER_MODE_XTS
*
* Enable Xor-encrypt-xor with ciphertext stealing mode (XTS) for symmetric
* ciphers.
*/
#define MBEDTLS_CIPHER_MODE_XTS
/**
* \def MBEDTLS_CIPHER_MODE_OFB
*

141
library/aes.c
View file

@ -44,7 +44,7 @@
#include "mbedtls/aesni.h"
#endif
#if defined(MBEDTLS_CIPHER_MODE_XEX)
#if defined(MBEDTLS_CIPHER_MODE_XEX) || defined(MBEDTLS_CIPHER_MODE_XTS)
#include "mbedtls/gf128mul.h"
#endif
@ -1045,6 +1045,145 @@ first:
}
#endif /* MBEDTLS_CIPHER_MODE_XEX */
#if defined(MBEDTLS_CIPHER_MODE_XTS)
/*
* AES-XTS buffer encryption/decryption
*/
int mbedtls_aes_crypt_xts( mbedtls_aes_context *crypt_ctx,
mbedtls_aes_context *tweak_ctx,
int mode,
size_t bits_length,
unsigned char iv[16],
const unsigned char *input,
unsigned char *output )
{
union xts_buf128 {
uint8_t u8[16];
uint64_t u64[2];
};
union xts_buf128 scratch;
union xts_buf128 cts_scratch;
union xts_buf128 t_buf;
union xts_buf128 cts_t_buf;
union xts_buf128 *inbuf;
union xts_buf128 *outbuf;
size_t length = bits_length / 8;
size_t nblk = length / 16;
size_t remn = length % 16;
inbuf = (union xts_buf128*)input;
outbuf = (union xts_buf128*)output;
/* For performing the ciphertext-stealing operation, we have to get at least
* one complete block */
if( length < 16 )
return( MBEDTLS_ERR_AES_INVALID_INPUT_LENGTH );
mbedtls_aes_crypt_ecb( tweak_ctx, MBEDTLS_AES_ENCRYPT, iv, t_buf.u8 );
if( mode == MBEDTLS_AES_DECRYPT && remn )
{
if( nblk == 1 )
goto decrypt_only_one_full_block;
nblk--;
}
goto first;
do
{
mbedtls_gf128mul_x_ble( t_buf.u8, t_buf.u8 );
first:
/* PP <- T xor P */
scratch.u64[0] = (uint64_t)( inbuf->u64[0] ^ t_buf.u64[0] );
scratch.u64[1] = (uint64_t)( inbuf->u64[1] ^ t_buf.u64[1] );
/* CC <- E(Key2,PP) */
mbedtls_aes_crypt_ecb( crypt_ctx, mode, scratch.u8, outbuf->u8 );
/* C <- T xor CC */
outbuf->u64[0] = (uint64_t)( outbuf->u64[0] ^ t_buf.u64[0] );
outbuf->u64[1] = (uint64_t)( outbuf->u64[1] ^ t_buf.u64[1] );
inbuf += 1;
outbuf += 1;
nblk -= 1;
} while( nblk > 0 );
/* Ciphertext stealing, if necessary */
if( remn != 0 )
{
outbuf = (union xts_buf128*)output;
inbuf = (union xts_buf128*)input;
nblk = length / 16;
if( mode == MBEDTLS_AES_ENCRYPT )
{
memcpy( cts_scratch.u8, (uint8_t*)&inbuf[nblk], remn );
memcpy( cts_scratch.u8 + remn, ((uint8_t*)&outbuf[nblk - 1]) + remn, 16 - remn );
memcpy( (uint8_t*)&outbuf[nblk], (uint8_t*)&outbuf[nblk - 1], remn );
mbedtls_gf128mul_x_ble( t_buf.u8, t_buf.u8 );
/* PP <- T xor P */
scratch.u64[0] = (uint64_t)( cts_scratch.u64[0] ^ t_buf.u64[0] );
scratch.u64[1] = (uint64_t)( cts_scratch.u64[1] ^ t_buf.u64[1] );
/* CC <- E(Key2,PP) */
mbedtls_aes_crypt_ecb( crypt_ctx, mode, scratch.u8, scratch.u8 );
/* C <- T xor CC */
outbuf[nblk - 1].u64[0] = (uint64_t)( scratch.u64[0] ^ t_buf.u64[0] );
outbuf[nblk - 1].u64[1] = (uint64_t)( scratch.u64[1] ^ t_buf.u64[1] );
}
else /* AES_DECRYPT */
{
mbedtls_gf128mul_x_ble( t_buf.u8, t_buf.u8 );
decrypt_only_one_full_block:
cts_t_buf.u64[0] = t_buf.u64[0];
cts_t_buf.u64[1] = t_buf.u64[1];
mbedtls_gf128mul_x_ble( t_buf.u8, t_buf.u8 );
/* PP <- T xor P */
scratch.u64[0] = (uint64_t)( inbuf[nblk - 1].u64[0] ^ t_buf.u64[0] );
scratch.u64[1] = (uint64_t)( inbuf[nblk - 1].u64[1] ^ t_buf.u64[1] );
/* CC <- E(Key2,PP) */
mbedtls_aes_crypt_ecb( crypt_ctx, mode, scratch.u8, scratch.u8 );
/* C <- T xor CC */
cts_scratch.u64[0] = (uint64_t)( scratch.u64[0] ^ t_buf.u64[0] );
cts_scratch.u64[1] = (uint64_t)( scratch.u64[1] ^ t_buf.u64[1] );
memcpy( (uint8_t*)&inbuf[nblk - 1], (uint8_t*)&inbuf[nblk], remn );
memcpy( (uint8_t*)&inbuf[nblk - 1] + remn, cts_scratch.u8 + remn, 16 - remn );
memcpy( (uint8_t*)&outbuf[nblk], cts_scratch.u8, remn );
/* PP <- T xor P */
scratch.u64[0] = (uint64_t)( inbuf[nblk - 1].u64[0] ^ cts_t_buf.u64[0] );
scratch.u64[1] = (uint64_t)( inbuf[nblk - 1].u64[1] ^ cts_t_buf.u64[1] );
/* CC <- E(Key2,PP) */
mbedtls_aes_crypt_ecb( crypt_ctx, mode, scratch.u8, scratch.u8 );
/* C <- T xor CC */
outbuf[nblk - 1].u64[0] = (uint64_t)( scratch.u64[0] ^ cts_t_buf.u64[0] );
outbuf[nblk - 1].u64[1] = (uint64_t)( scratch.u64[1] ^ cts_t_buf.u64[1] );
}
}
return( 0 );
}
#endif /* MBEDTLS_CIPHER_MODE_XTS */
#if defined(MBEDTLS_CIPHER_MODE_CFB)
/*
* AES-CFB128 buffer encryption/decryption

3
library/version_features.c
View file

@ -252,6 +252,9 @@ static const char *features[] = {
#if defined(MBEDTLS_CIPHER_MODE_XEX)
"MBEDTLS_CIPHER_MODE_XEX",
#endif /* MBEDTLS_CIPHER_MODE_XEX */
#if defined(MBEDTLS_CIPHER_MODE_XTS)
"MBEDTLS_CIPHER_MODE_XTS",
#endif /* MBEDTLS_CIPHER_MODE_XTS */
#if defined(MBEDTLS_CIPHER_MODE_OFB)
"MBEDTLS_CIPHER_MODE_OFB",
#endif /* MBEDTLS_CIPHER_MODE_OFB */

33
programs/test/benchmark.c
View file

@ -99,8 +99,8 @@ int main( void )
#define OPTIONS \
"md4, md5, ripemd160, sha1, sha256, sha512,\n" \
"arc4, des3, des, camellia, blowfish,\n" \
"aes_cbc, aes_gcm, aes_ccm, aes_cmac, aes_xex, des3_cmac,\n" \
"havege, ctr_drbg, hmac_drbg\n" \
"aes_cbc, aes_gcm, aes_ccm, aes_cmac, aes_xex, aes_xts,\n" \
"des3_cmac, havege, ctr_drbg, hmac_drbg\n" \
"rsa, dhm, ecdsa, ecdh.\n"
#if defined(MBEDTLS_ERROR_C)
@ -233,8 +233,8 @@ unsigned char buf[BUFSIZE];
typedef struct {
char md4, md5, ripemd160, sha1, sha256, sha512,
arc4, des3, des,
aes_cbc, aes_gcm, aes_ccm, aes_cmac, aes_xex, des3_cmac,
aria, camellia, blowfish,
aes_cbc, aes_gcm, aes_ccm, aes_cmac, aes_xex, aes_xts,
des3_cmac, aria, camellia, blowfish,
havege, ctr_drbg, hmac_drbg,
rsa, dhm, ecdsa, ecdh;
} todo_list;
@ -281,6 +281,8 @@ int main( int argc, char *argv[] )
todo.aes_cbc = 1;
else if( strcmp( argv[i], "aes_xex" ) == 0 )
todo.aes_xex = 1;
else if( strcmp( argv[i], "aes_xts" ) == 0 )
todo.aes_xts = 1;
else if( strcmp( argv[i], "aes_gcm" ) == 0 )
todo.aes_gcm = 1;
else if( strcmp( argv[i], "aes_ccm" ) == 0 )
@ -451,6 +453,29 @@ int main( int argc, char *argv[] )
mbedtls_aes_free( &tweak_ctx );
}
#endif
#if defined(MBEDTLS_CIPHER_MODE_XTS)
if( todo.aes_xts )
{
int keysize;
mbedtls_aes_context crypt_ctx, tweak_ctx;
mbedtls_aes_init( &crypt_ctx );
mbedtls_aes_init( &tweak_ctx );
for( keysize = 128; keysize <= 256; keysize += 64 )
{
mbedtls_snprintf( title, sizeof( title ), "AES-XTS-%d", keysize );
memset( buf, 0, sizeof( buf ) );
memset( tmp, 0, sizeof( tmp ) );
mbedtls_aes_setkey_enc( &crypt_ctx, tmp, keysize );
mbedtls_aes_setkey_enc( &tweak_ctx, tmp, keysize );
TIME_AND_TSC( title,
mbedtls_aes_crypt_xts( &crypt_ctx, &tweak_ctx, MBEDTLS_AES_ENCRYPT, BUFSIZE * 8, tmp, buf, buf ) );
}
mbedtls_aes_free( &crypt_ctx );
mbedtls_aes_free( &tweak_ctx );
}
#endif
#if defined(MBEDTLS_GCM_C)
if( todo.aes_gcm )
{

1
tests/CMakeLists.txt
View file

@ -49,6 +49,7 @@ add_test_suite(aes aes.cbc)
add_test_suite(aes aes.cfb)
add_test_suite(aes aes.rest)
add_test_suite(aes aes.xex)
add_test_suite(aes aes.xts)
add_test_suite(arc4)
add_test_suite(aria)
add_test_suite(asn1write)

74
tests/suites/test_suite_aes.function
View file

@ -225,6 +225,80 @@ exit:
}
/* END_CASE */
/* BEGIN_CASE depends_on:MBEDTLS_CIPHER_MODE_XTS */
void aes_encrypt_xts( char *hex_key_string, char *hex_iv_string,
char *hex_src_string, char *hex_dst_string,
int data_unit_len, int xts_result )
{
unsigned char key_str[100] = { 0, };
unsigned char iv_str[100] = { 0, };
unsigned char src_str[100] = { 0, };
unsigned char dst_str[100] = { 0, };
unsigned char output[100] = { 0, };
mbedtls_aes_context crypt_ctx, tweak_ctx;
int key_len, data_len;
mbedtls_aes_init( &crypt_ctx );
mbedtls_aes_init( &tweak_ctx );
key_len = unhexify( key_str, hex_key_string );
unhexify( iv_str, hex_iv_string );
data_len = unhexify( src_str, hex_src_string );
mbedtls_aes_setkey_enc( &crypt_ctx, key_str, ( key_len * 8 ) / 2 );
mbedtls_aes_setkey_enc( &tweak_ctx, key_str + key_len / 2, ( key_len * 8 ) / 2 );
TEST_ASSERT( mbedtls_aes_crypt_xts( &crypt_ctx, &tweak_ctx, MBEDTLS_AES_ENCRYPT, data_unit_len, iv_str, src_str, output ) == xts_result );
if( xts_result == 0 )
{
hexify( dst_str, output, data_len );
TEST_ASSERT( strcmp( (char *) dst_str, hex_dst_string ) == 0 );
}
exit:
mbedtls_aes_free( &crypt_ctx );
mbedtls_aes_free( &tweak_ctx );
}
/* END_CASE */
/* BEGIN_CASE depends_on:MBEDTLS_CIPHER_MODE_XTS */
void aes_decrypt_xts( char *hex_key_string, char *hex_iv_string,
char *hex_src_string, char *hex_dst_string,
int data_unit_len, int xts_result )
{
unsigned char key_str[100] = { 0, };
unsigned char iv_str[100] = { 0, };
unsigned char src_str[100] = { 0, };
unsigned char dst_str[100] = { 0, };
unsigned char output[100] = { 0, };
mbedtls_aes_context crypt_ctx, tweak_ctx;
int key_len, data_len;
mbedtls_aes_init( &crypt_ctx );
mbedtls_aes_init( &tweak_ctx );
key_len = unhexify( key_str, hex_key_string );
unhexify( iv_str, hex_iv_string );
data_len = unhexify( src_str, hex_src_string );
mbedtls_aes_setkey_dec( &crypt_ctx, key_str, ( key_len * 8 ) / 2 );
mbedtls_aes_setkey_enc( &tweak_ctx, key_str + key_len / 2, ( key_len * 8 ) / 2 );
TEST_ASSERT( mbedtls_aes_crypt_xts( &crypt_ctx, &tweak_ctx, MBEDTLS_AES_DECRYPT, data_unit_len, iv_str, src_str, output ) == xts_result );
if( xts_result == 0 )
{
hexify( dst_str, output, data_len );
TEST_ASSERT( strcmp( (char *) dst_str, hex_dst_string ) == 0 );
}
exit:
mbedtls_aes_free( &crypt_ctx );
mbedtls_aes_free( &tweak_ctx );
}
/* END_CASE */
/* BEGIN_CASE depends_on:MBEDTLS_CIPHER_MODE_CFB */
void aes_encrypt_cfb128( char *hex_key_string, char *hex_iv_string,
char *hex_src_string, char *hex_dst_string )

4200
tests/suites/test_suite_aes.xts.data Normal file
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