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mbedtls/library/ccm.c
Manuel Pégourié-Gonnard ce77d55023 Implement ccm_auth_decrypt()
2014-05-07 12:13:13 +02:00

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/*
* NIST SP800-38C compliant CCM implementation
*
* Copyright (C) 2014, Brainspark B.V.
*
* This file is part of PolarSSL (http://www.polarssl.org)
* Lead Maintainer: Paul Bakker <polarssl_maintainer at polarssl.org>
*
* All rights reserved.
*
* This program 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 program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
/*
* Definition of CCM:
* http://csrc.nist.gov/publications/nistpubs/800-38C/SP800-38C_updated-July20_2007.pdf
* RFC 3610 "Counter with CBC-MAC (CCM)"
*
* Related:
* RFC 5116 "An Interface and Algorithms for Authenticated Encryption"
*/
#if !defined(POLARSSL_CONFIG_FILE)
#include "polarssl/config.h"
#else
#include POLARSSL_CONFIG_FILE
#endif
#if defined(POLARSSL_CCM_C)
#include "polarssl/ccm.h"
#define CCM_ENCRYPT 0
#define CCM_DECRYPT 1
/*
* Initialize context
*/
int ccm_init( ccm_context *ctx, cipher_id_t cipher,
const unsigned char *key, unsigned int keysize )
{
int ret;
const cipher_info_t *cipher_info;
memset( ctx, 0, sizeof( ccm_context ) );
cipher_info = cipher_info_from_values( cipher, keysize, POLARSSL_MODE_ECB );
if( cipher_info == NULL )
return( POLARSSL_ERR_CCM_BAD_INPUT );
if( cipher_info->block_size != 16 )
return( POLARSSL_ERR_CCM_BAD_INPUT );
if( ( ret = cipher_init_ctx( &ctx->cipher_ctx, cipher_info ) ) != 0 )
return( ret );
if( ( ret = cipher_setkey( &ctx->cipher_ctx, key, keysize,
POLARSSL_ENCRYPT ) ) != 0 )
{
return( ret );
}
return( 0 );
}
/*
* Free context
*/
void ccm_free( ccm_context *ctx )
{
(void) cipher_free_ctx( &ctx->cipher_ctx );
memset( ctx, 0, sizeof( ccm_context ) );
}
#define UPDATE_CBC_MAC( src ) \
{ \
size_t olen; \
\
for( i = 0; i < 16; i++ ) \
src[i] ^= y[i]; \
\
if( ( ret = cipher_update( &ctx->cipher_ctx, src, 16, \
y, &olen ) ) != 0 ) \
{ \
return( ret ); \
} \
}
#define CTR_CRYPT_BLOCK( dst, src ) \
{ \
size_t olen; \
\
if( ( ret = cipher_update( &ctx->cipher_ctx, ctr, 16, \
dst, &olen ) ) != 0 ) \
{ \
return( ret ); \
} \
\
for( i = 0; i < 16; i++ ) \
dst[i] ^= src[i]; \
}
/*
* Authenticated encryption or decryption
*/
static int ccm_auth_crypt( ccm_context *ctx, int mode, size_t length,
const unsigned char *iv, size_t iv_len,
const unsigned char *add, size_t add_len,
const unsigned char *input, unsigned char *output,
unsigned char *tag, size_t tag_len )
{
int ret;
unsigned char i;
unsigned char q = 16 - 1 - iv_len;
size_t len_left;
unsigned char b[16];
unsigned char y[16];
unsigned char ctr[16];
const unsigned char *src;
unsigned char *dst;
/*
* Check length requirements: SP800-38C A.1
* Additional requirement: a < 2^16 - 2^8 to simplify the code.
* 'length' checked later (when writing it to the first block)
*/
if( tag_len < 4 || tag_len > 16 || tag_len % 2 != 0 )
return( POLARSSL_ERR_CCM_BAD_INPUT );
/* Also implies q is within bounds */
if( iv_len < 7 || iv_len > 13 )
return( POLARSSL_ERR_CCM_BAD_INPUT );
if( add_len > 0xFF00 )
return( POLARSSL_ERR_CCM_BAD_INPUT );
/*
* First block B_0:
* 0 .. 0 flags
* 1 .. iv_len nonce (aka iv)
* iv_len+1 .. 15 length
*
* With flags as (bits):
* 7 0
* 6 add present?
* 5 .. 3 (t - 2) / 2
* 2 .. 0 q - 1
*/
b[0] = 0;
b[0] |= ( add_len > 0 ) << 6;
b[0] |= ( ( tag_len - 2 ) / 2 ) << 3;
b[0] |= q - 1;
memcpy( b + 1, iv, iv_len );
for( i = 0, len_left = length; i < q; i++, len_left >>= 8 )
b[15-i] = (unsigned char)( len_left & 0xFF );
if( len_left > 0 )
return( POLARSSL_ERR_CCM_BAD_INPUT );
/* Start CBC-MAC with first block */
memset( y, 0, 16 );
UPDATE_CBC_MAC( b );
/*
* If there is additional data, update CBC-MAC with
* add_len, add, 0 (padding to a block boundary)
*/
if( add_len > 0 )
{
size_t use_len;
len_left = add_len;
src = add;
memset( b, 0, 16 );
b[0] = (unsigned char)( ( add_len >> 8 ) & 0xFF );
b[1] = (unsigned char)( ( add_len ) & 0xFF );
use_len = len_left < 16 - 2 ? len_left : 16 - 2;
memcpy( b + 2, src, use_len );
len_left -= use_len;
src += use_len;
UPDATE_CBC_MAC( b );
while( len_left > 16 )
{
memcpy( b, src, 16 );
UPDATE_CBC_MAC( b );
len_left -= 16;
src += 16;
}
if( len_left > 0 )
{
memset( b, 0, 16 );
memcpy( b, src, len_left );
UPDATE_CBC_MAC( b );
}
}
/*
* Counter block:
* 0 .. 0 flags
* 1 .. iv_len nonce (aka iv)
* iv_len+1 .. 15 counter (initially 1)
*
* With flags as (bits):
* 7 .. 3 0
* 2 .. 0 q - 1
*/
ctr[0] = q - 1;
memcpy( ctr + 1, iv, iv_len );
memset( ctr + 1 + iv_len, 0, q );
ctr[15] = 1;
len_left = length;
src = input;
dst = output;
/*
* Authenticate and crypt message
* The only difference between encryption and decryption is
* the respective order of authentication and {en,de}cryption
*/
while( len_left > 16 )
{
if( mode == CCM_ENCRYPT )
{
memcpy( b, src, 16 );
UPDATE_CBC_MAC( b );
}
CTR_CRYPT_BLOCK( dst, src );
if( mode == CCM_DECRYPT )
{
memcpy( b, dst, 16 );
UPDATE_CBC_MAC( b );
}
dst += 16;
src += 16;
len_left -= 16;
/*
* Increment counter.
* No need to check for overflow thanks to the length check above.
*/
for( i = 0; i < q; i++ )
if( ++ctr[15-i] != 0 )
break;
}
if( len_left > 0 )
{
unsigned char mask[16];
size_t olen;
if( mode == CCM_ENCRYPT )
{
memset( b, 0, 16 );
memcpy( b, src, len_left );
UPDATE_CBC_MAC( b );
}
if( ( ret = cipher_update( &ctx->cipher_ctx, ctr, 16,
mask, &olen ) ) != 0 )
{
return( ret );
}
for( i = 0; i < len_left; i++ )
dst[i] = src[i] ^ mask[i];
if( mode == CCM_DECRYPT )
{
memset( b, 0, 16 );
memcpy( b, dst, len_left );
UPDATE_CBC_MAC( b );
}
}
/*
* Authentication: reset counter and {en,de}crypt internal tag
*/
for( i = 0; i < q; i++ )
ctr[15-i] = 0;
CTR_CRYPT_BLOCK( b, y );
memcpy( tag, b, tag_len );
return( 0 );
}
/*
* Authenticated encryption
*/
int ccm_encrypt_and_tag( ccm_context *ctx, size_t length,
const unsigned char *iv, size_t iv_len,
const unsigned char *add, size_t add_len,
const unsigned char *input, unsigned char *output,
unsigned char *tag, size_t tag_len )
{
return( ccm_auth_crypt( ctx, CCM_ENCRYPT, length, iv, iv_len,
add, add_len, input, output, tag, tag_len ) );
}
/*
* Authenticated decryption
*/
int ccm_auth_decrypt( ccm_context *ctx, size_t length,
const unsigned char *iv, size_t iv_len,
const unsigned char *add, size_t add_len,
const unsigned char *input, unsigned char *output,
const unsigned char *tag, size_t tag_len )
{
int ret;
unsigned char check_tag[16];
unsigned char i;
int diff;
if( ( ret = ccm_auth_crypt( ctx, CCM_DECRYPT, length,
iv, iv_len, add, add_len,
input, output, check_tag, tag_len ) ) != 0 )
{
return( ret );
}
/* Check tag in "constant-time" */
for( diff = 0, i = 0; i < tag_len; i++ )
diff |= tag[i] ^ check_tag[i];
if( diff != 0 )
{
memset( output, 0, length );
return( POLARSSL_ERR_CCM_AUTH_FAILED );
}
return( 0 );
}
#if defined(POLARSSL_SELF_TEST) && defined(POLARSSL_AES_C)
#if defined(POLARSSL_PLATFORM_C)
#include "polarssl/platform.h"
#else
#define polarssl_printf printf
#endif
/*
* Examples 1 to 3 from SP800-38C Appendix C
*/
#define NB_TESTS 3
/*
* The data is the same for all tests, only the used length changes
*/
static const unsigned char key[] = {
0x40, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47,
0x48, 0x49, 0x4a, 0x4b, 0x4c, 0x4d, 0x4e, 0x4f
};
static const unsigned char iv[] = {
0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
0x18, 0x19, 0x1a, 0x1b
};
static const unsigned char ad[] = {
0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
0x10, 0x11, 0x12, 0x13
};
static const unsigned char msg[] = {
0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27,
0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f,
0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37,
};
static const size_t iv_len [NB_TESTS] = { 7, 8, 12 };
static const size_t add_len[NB_TESTS] = { 8, 16, 20 };
static const size_t msg_len[NB_TESTS] = { 4, 16, 24 };
static const size_t tag_len[NB_TESTS] = { 4, 6, 8 };
static const unsigned char res[NB_TESTS][32] = {
{ 0x71, 0x62, 0x01, 0x5b, 0x4d, 0xac, 0x25, 0x5d },
{ 0xd2, 0xa1, 0xf0, 0xe0, 0x51, 0xea, 0x5f, 0x62,
0x08, 0x1a, 0x77, 0x92, 0x07, 0x3d, 0x59, 0x3d,
0x1f, 0xc6, 0x4f, 0xbf, 0xac, 0xcd },
{ 0xe3, 0xb2, 0x01, 0xa9, 0xf5, 0xb7, 0x1a, 0x7a,
0x9b, 0x1c, 0xea, 0xec, 0xcd, 0x97, 0xe7, 0x0b,
0x61, 0x76, 0xaa, 0xd9, 0xa4, 0x42, 0x8a, 0xa5,
0x48, 0x43, 0x92, 0xfb, 0xc1, 0xb0, 0x99, 0x51 }
};
int ccm_self_test( int verbose )
{
ccm_context ctx;
unsigned char out[32];
size_t i;
int ret;
if( ccm_init( &ctx, POLARSSL_CIPHER_ID_AES, key, 8 * sizeof key ) != 0 )
{
if( verbose != 0 )
polarssl_printf( " CCM: setup failed" );
return( 1 );
}
for( i = 0; i < NB_TESTS; i++ )
{
if( verbose != 0 )
polarssl_printf( " CCM-AES #%u: ", (unsigned int) i + 1 );
ret = ccm_encrypt_and_tag( &ctx, msg_len[i],
iv, iv_len[i], ad, add_len[i],
msg, out,
out + msg_len[i], tag_len[i] );
if( ret != 0 ||
memcmp( out, res[i], msg_len[i] + tag_len[i] ) != 0 )
{
if( verbose != 0 )
polarssl_printf( "failed\n" );
return( 1 );
}
ret = ccm_auth_decrypt( &ctx, msg_len[i],
iv, iv_len[i], ad, add_len[i],
res[i], out,
res[i] + msg_len[i], tag_len[i] );
if( ret != 0 ||
memcmp( out, msg, msg_len[i] ) != 0 )
{
if( verbose != 0 )
polarssl_printf( "failed\n" );
return( 1 );
}
if( verbose != 0 )
polarssl_printf( "passed\n" );
}
ccm_free( &ctx );
if( verbose != 0 )
polarssl_printf( "\n" );
return( 0 );
}
#endif /* POLARSSL_SELF_TEST && POLARSSL_AES_C */
#endif /* POLARSSL_CCM_C */
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