434 lines
11 KiB
C
434 lines
11 KiB
C
/*
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* AES-256 file encryption program
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*
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* Copyright (C) 2006-2013, ARM Limited, All Rights Reserved
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*
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* This file is part of mbed TLS (http://www.polarssl.org)
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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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#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(_WIN32)
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#include <windows.h>
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#if !defined(_WIN32_WCE)
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#include <io.h>
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#endif
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#else
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#include <sys/types.h>
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#include <unistd.h>
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#endif
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#include <string.h>
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#include <stdlib.h>
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#include <stdio.h>
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#include <time.h>
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#include "polarssl/aes.h"
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#include "polarssl/sha256.h"
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#define MODE_ENCRYPT 0
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#define MODE_DECRYPT 1
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#define USAGE \
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"\n aescrypt2 <mode> <input filename> <output filename> <key>\n" \
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"\n <mode>: 0 = encrypt, 1 = decrypt\n" \
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"\n example: aescrypt2 0 file file.aes hex:E76B2413958B00E193\n" \
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"\n"
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#if !defined(POLARSSL_AES_C) || !defined(POLARSSL_SHA256_C)
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int main( int argc, char *argv[] )
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{
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((void) argc);
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((void) argv);
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printf("POLARSSL_AES_C and/or POLARSSL_SHA256_C not defined.\n");
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return( 0 );
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}
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#else
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int main( int argc, char *argv[] )
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{
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int ret = 1;
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int i, n;
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int mode, lastn;
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size_t keylen;
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FILE *fkey, *fin = NULL, *fout = NULL;
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char *p;
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unsigned char IV[16];
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unsigned char key[512];
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unsigned char digest[32];
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unsigned char buffer[1024];
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unsigned char diff;
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aes_context aes_ctx;
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sha256_context sha_ctx;
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#if defined(_WIN32_WCE)
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long filesize, offset;
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#elif defined(_WIN32)
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LARGE_INTEGER li_size;
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__int64 filesize, offset;
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#else
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off_t filesize, offset;
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#endif
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aes_init( &aes_ctx );
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sha256_init( &sha_ctx );
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/*
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* Parse the command-line arguments.
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*/
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if( argc != 5 )
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{
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printf( USAGE );
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#if defined(_WIN32)
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printf( "\n Press Enter to exit this program.\n" );
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fflush( stdout ); getchar();
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#endif
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goto exit;
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}
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mode = atoi( argv[1] );
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if( mode != MODE_ENCRYPT && mode != MODE_DECRYPT )
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{
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fprintf( stderr, "invalide operation mode\n" );
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goto exit;
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}
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if( strcmp( argv[2], argv[3] ) == 0 )
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{
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fprintf( stderr, "input and output filenames must differ\n" );
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goto exit;
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}
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if( ( fin = fopen( argv[2], "rb" ) ) == NULL )
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{
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fprintf( stderr, "fopen(%s,rb) failed\n", argv[2] );
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goto exit;
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}
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if( ( fout = fopen( argv[3], "wb+" ) ) == NULL )
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{
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fprintf( stderr, "fopen(%s,wb+) failed\n", argv[3] );
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goto exit;
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}
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/*
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* Read the secret key and clean the command line.
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*/
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if( ( fkey = fopen( argv[4], "rb" ) ) != NULL )
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{
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keylen = fread( key, 1, sizeof( key ), fkey );
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fclose( fkey );
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}
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else
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{
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if( memcmp( argv[4], "hex:", 4 ) == 0 )
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{
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p = &argv[4][4];
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keylen = 0;
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while( sscanf( p, "%02X", &n ) > 0 &&
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keylen < (int) sizeof( key ) )
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{
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key[keylen++] = (unsigned char) n;
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p += 2;
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}
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}
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else
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{
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keylen = strlen( argv[4] );
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if( keylen > (int) sizeof( key ) )
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keylen = (int) sizeof( key );
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memcpy( key, argv[4], keylen );
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}
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}
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memset( argv[4], 0, strlen( argv[4] ) );
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#if defined(_WIN32_WCE)
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filesize = fseek( fin, 0L, SEEK_END );
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#else
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#if defined(_WIN32)
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/*
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* Support large files (> 2Gb) on Win32
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*/
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li_size.QuadPart = 0;
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li_size.LowPart =
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SetFilePointer( (HANDLE) _get_osfhandle( _fileno( fin ) ),
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li_size.LowPart, &li_size.HighPart, FILE_END );
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if( li_size.LowPart == 0xFFFFFFFF && GetLastError() != NO_ERROR )
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{
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fprintf( stderr, "SetFilePointer(0,FILE_END) failed\n" );
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goto exit;
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}
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filesize = li_size.QuadPart;
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#else
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if( ( filesize = lseek( fileno( fin ), 0, SEEK_END ) ) < 0 )
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{
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perror( "lseek" );
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goto exit;
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}
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#endif
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#endif
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if( fseek( fin, 0, SEEK_SET ) < 0 )
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{
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fprintf( stderr, "fseek(0,SEEK_SET) failed\n" );
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goto exit;
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}
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if( mode == MODE_ENCRYPT )
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{
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/*
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* Generate the initialization vector as:
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* IV = SHA-256( filesize || filename )[0..15]
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*/
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for( i = 0; i < 8; i++ )
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buffer[i] = (unsigned char)( filesize >> ( i << 3 ) );
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p = argv[2];
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sha256_starts( &sha_ctx, 0 );
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sha256_update( &sha_ctx, buffer, 8 );
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sha256_update( &sha_ctx, (unsigned char *) p, strlen( p ) );
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sha256_finish( &sha_ctx, digest );
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memcpy( IV, digest, 16 );
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/*
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* The last four bits in the IV are actually used
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* to store the file size modulo the AES block size.
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*/
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lastn = (int)( filesize & 0x0F );
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IV[15] = (unsigned char)
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( ( IV[15] & 0xF0 ) | lastn );
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/*
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* Append the IV at the beginning of the output.
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*/
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if( fwrite( IV, 1, 16, fout ) != 16 )
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{
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fprintf( stderr, "fwrite(%d bytes) failed\n", 16 );
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goto exit;
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}
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/*
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* Hash the IV and the secret key together 8192 times
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* using the result to setup the AES context and HMAC.
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*/
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memset( digest, 0, 32 );
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memcpy( digest, IV, 16 );
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for( i = 0; i < 8192; i++ )
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{
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sha256_starts( &sha_ctx, 0 );
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sha256_update( &sha_ctx, digest, 32 );
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sha256_update( &sha_ctx, key, keylen );
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sha256_finish( &sha_ctx, digest );
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}
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memset( key, 0, sizeof( key ) );
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aes_setkey_enc( &aes_ctx, digest, 256 );
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sha256_hmac_starts( &sha_ctx, digest, 32, 0 );
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/*
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* Encrypt and write the ciphertext.
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*/
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for( offset = 0; offset < filesize; offset += 16 )
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{
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n = ( filesize - offset > 16 ) ? 16 : (int)
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( filesize - offset );
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if( fread( buffer, 1, n, fin ) != (size_t) n )
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{
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fprintf( stderr, "fread(%d bytes) failed\n", n );
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goto exit;
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}
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for( i = 0; i < 16; i++ )
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buffer[i] = (unsigned char)( buffer[i] ^ IV[i] );
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aes_crypt_ecb( &aes_ctx, AES_ENCRYPT, buffer, buffer );
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sha256_hmac_update( &sha_ctx, buffer, 16 );
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if( fwrite( buffer, 1, 16, fout ) != 16 )
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{
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fprintf( stderr, "fwrite(%d bytes) failed\n", 16 );
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goto exit;
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}
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memcpy( IV, buffer, 16 );
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}
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/*
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* Finally write the HMAC.
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*/
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sha256_hmac_finish( &sha_ctx, digest );
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if( fwrite( digest, 1, 32, fout ) != 32 )
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{
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fprintf( stderr, "fwrite(%d bytes) failed\n", 16 );
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goto exit;
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}
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}
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if( mode == MODE_DECRYPT )
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{
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unsigned char tmp[16];
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/*
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* The encrypted file must be structured as follows:
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*
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* 00 .. 15 Initialization Vector
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* 16 .. 31 AES Encrypted Block #1
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* ..
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* N*16 .. (N+1)*16 - 1 AES Encrypted Block #N
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* (N+1)*16 .. (N+1)*16 + 32 HMAC-SHA-256(ciphertext)
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*/
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if( filesize < 48 )
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{
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fprintf( stderr, "File too short to be encrypted.\n" );
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goto exit;
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}
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if( ( filesize & 0x0F ) != 0 )
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{
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fprintf( stderr, "File size not a multiple of 16.\n" );
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goto exit;
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}
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/*
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* Subtract the IV + HMAC length.
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*/
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filesize -= ( 16 + 32 );
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/*
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* Read the IV and original filesize modulo 16.
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*/
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if( fread( buffer, 1, 16, fin ) != 16 )
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{
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fprintf( stderr, "fread(%d bytes) failed\n", 16 );
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goto exit;
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}
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memcpy( IV, buffer, 16 );
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lastn = IV[15] & 0x0F;
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/*
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* Hash the IV and the secret key together 8192 times
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* using the result to setup the AES context and HMAC.
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*/
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memset( digest, 0, 32 );
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memcpy( digest, IV, 16 );
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for( i = 0; i < 8192; i++ )
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{
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sha256_starts( &sha_ctx, 0 );
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sha256_update( &sha_ctx, digest, 32 );
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sha256_update( &sha_ctx, key, keylen );
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sha256_finish( &sha_ctx, digest );
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}
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memset( key, 0, sizeof( key ) );
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aes_setkey_dec( &aes_ctx, digest, 256 );
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sha256_hmac_starts( &sha_ctx, digest, 32, 0 );
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/*
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* Decrypt and write the plaintext.
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*/
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for( offset = 0; offset < filesize; offset += 16 )
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{
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if( fread( buffer, 1, 16, fin ) != 16 )
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{
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fprintf( stderr, "fread(%d bytes) failed\n", 16 );
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goto exit;
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}
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memcpy( tmp, buffer, 16 );
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sha256_hmac_update( &sha_ctx, buffer, 16 );
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aes_crypt_ecb( &aes_ctx, AES_DECRYPT, buffer, buffer );
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for( i = 0; i < 16; i++ )
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buffer[i] = (unsigned char)( buffer[i] ^ IV[i] );
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memcpy( IV, tmp, 16 );
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n = ( lastn > 0 && offset == filesize - 16 )
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? lastn : 16;
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if( fwrite( buffer, 1, n, fout ) != (size_t) n )
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{
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fprintf( stderr, "fwrite(%d bytes) failed\n", n );
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goto exit;
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}
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}
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/*
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* Verify the message authentication code.
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*/
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sha256_hmac_finish( &sha_ctx, digest );
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if( fread( buffer, 1, 32, fin ) != 32 )
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{
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fprintf( stderr, "fread(%d bytes) failed\n", 32 );
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goto exit;
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}
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/* Use constant-time buffer comparison */
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diff = 0;
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for( i = 0; i < 32; i++ )
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diff |= digest[i] ^ buffer[i];
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if( diff != 0 )
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{
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fprintf( stderr, "HMAC check failed: wrong key, "
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"or file corrupted.\n" );
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goto exit;
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}
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}
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ret = 0;
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exit:
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if( fin )
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fclose( fin );
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if( fout )
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fclose( fout );
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memset( buffer, 0, sizeof( buffer ) );
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memset( digest, 0, sizeof( digest ) );
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aes_free( &aes_ctx );
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sha256_free( &sha_ctx );
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return( ret );
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}
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#endif /* POLARSSL_AES_C && POLARSSL_SHA256_C */
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