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