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mbedtls/programs/aes/aescrypt2.c
Hanno Becker 9a1a151a1a Zeroize sensitive data in aescrypt2 and crypt_and_hash examples 
This commit replaces multiple `memset()` calls in the example
programs aes/aescrypt2.c and aes/crypt_and_hash.c by calls to
the reliable zeroization function `mbedtls_zeroize()`.

While not a security issue because the code is in the example
programs, it's bad practice and should be fixed.
2018-10-15 13:26:37 +01:00

468 lines
12 KiB
C
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/*
* AES-256 file encryption program
*
* Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
* SPDX-License-Identifier: Apache-2.0
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* This file is part of mbed TLS (https://tls.mbed.org)
*/
#if !defined(MBEDTLS_CONFIG_FILE)
#include "mbedtls/config.h"
#else
#include MBEDTLS_CONFIG_FILE
#endif
#if defined(MBEDTLS_PLATFORM_C)
#include "mbedtls/platform.h"
#else
#include <stdio.h>
#include <stdlib.h>
#define mbedtls_fprintf fprintf
#define mbedtls_printf printf
#define MBEDTLS_EXIT_SUCCESS EXIT_SUCCESS
#define MBEDTLS_EXIT_FAILURE EXIT_FAILURE
#endif /* MBEDTLS_PLATFORM_C */
#include "mbedtls/aes.h"
#include "mbedtls/md.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#if defined(_WIN32)
#include <windows.h>
#if !defined(_WIN32_WCE)
#include <io.h>
#endif
#else
#include <sys/types.h>
#include <unistd.h>
#endif
#define MODE_ENCRYPT 0
#define MODE_DECRYPT 1
#define USAGE \
"\n aescrypt2 <mode> <input filename> <output filename> <key>\n" \
"\n <mode>: 0 = encrypt, 1 = decrypt\n" \
"\n example: aescrypt2 0 file file.aes hex:E76B2413958B00E193\n" \
"\n"
#if !defined(MBEDTLS_AES_C) || !defined(MBEDTLS_SHA256_C) || \
!defined(MBEDTLS_FS_IO) || !defined(MBEDTLS_MD_C)
int main( void )
{
mbedtls_printf("MBEDTLS_AES_C and/or MBEDTLS_SHA256_C "
"and/or MBEDTLS_FS_IO and/or MBEDTLS_MD_C "
"not defined.\n");
return( 0 );
}
#else
/* Implementation that should never be optimized out by the compiler */
static void mbedtls_zeroize( void *v, size_t n ) {
volatile unsigned char *p = v; while( n-- ) *p++ = 0;
}
int main( int argc, char *argv[] )
{
int ret = 0;
int exit_code = MBEDTLS_EXIT_FAILURE;
unsigned int i, n;
int mode, lastn;
size_t keylen;
FILE *fkey, *fin = NULL, *fout = NULL;
char *p;
unsigned char IV[16];
unsigned char tmp[16];
unsigned char key[512];
unsigned char digest[32];
unsigned char buffer[1024];
unsigned char diff;
mbedtls_aes_context aes_ctx;
mbedtls_md_context_t sha_ctx;
#if defined(_WIN32_WCE)
long filesize, offset;
#elif defined(_WIN32)
LARGE_INTEGER li_size;
__int64 filesize, offset;
#else
off_t filesize, offset;
#endif
mbedtls_aes_init( &aes_ctx );
mbedtls_md_init( &sha_ctx );
ret = mbedtls_md_setup( &sha_ctx, mbedtls_md_info_from_type( MBEDTLS_MD_SHA256 ), 1 );
if( ret != 0 )
{
mbedtls_printf( " ! mbedtls_md_setup() returned -0x%04x\n", -ret );
goto exit;
}
/*
* Parse the command-line arguments.
*/
if( argc != 5 )
{
mbedtls_printf( USAGE );
#if defined(_WIN32)
mbedtls_printf( "\n Press Enter to exit this program.\n" );
fflush( stdout ); getchar();
#endif
goto exit;
}
mode = atoi( argv[1] );
memset( IV, 0, sizeof( IV ) );
memset( key, 0, sizeof( key ) );
memset( digest, 0, sizeof( digest ) );
memset( buffer, 0, sizeof( buffer ) );
if( mode != MODE_ENCRYPT && mode != MODE_DECRYPT )
{
mbedtls_fprintf( stderr, "invalide operation mode\n" );
goto exit;
}
if( strcmp( argv[2], argv[3] ) == 0 )
{
mbedtls_fprintf( stderr, "input and output filenames must differ\n" );
goto exit;
}
if( ( fin = fopen( argv[2], "rb" ) ) == NULL )
{
mbedtls_fprintf( stderr, "fopen(%s,rb) failed\n", argv[2] );
goto exit;
}
if( ( fout = fopen( argv[3], "wb+" ) ) == NULL )
{
mbedtls_fprintf( stderr, "fopen(%s,wb+) failed\n", argv[3] );
goto exit;
}
/*
* Read the secret key from file or command line
*/
if( ( fkey = fopen( argv[4], "rb" ) ) != NULL )
{
keylen = fread( key, 1, sizeof( key ), fkey );
fclose( fkey );
}
else
{
if( memcmp( argv[4], "hex:", 4 ) == 0 )
{
p = &argv[4][4];
keylen = 0;
while( sscanf( p, "%02X", &n ) > 0 &&
keylen < (int) sizeof( key ) )
{
key[keylen++] = (unsigned char) n;
p += 2;
}
}
else
{
keylen = strlen( argv[4] );
if( keylen > (int) sizeof( key ) )
keylen = (int) sizeof( key );
memcpy( key, argv[4], keylen );
}
}
#if defined(_WIN32_WCE)
filesize = fseek( fin, 0L, SEEK_END );
#else
#if defined(_WIN32)
/*
* Support large files (> 2Gb) on Win32
*/
li_size.QuadPart = 0;
li_size.LowPart =
SetFilePointer( (HANDLE) _get_osfhandle( _fileno( fin ) ),
li_size.LowPart, &li_size.HighPart, FILE_END );
if( li_size.LowPart == 0xFFFFFFFF && GetLastError() != NO_ERROR )
{
mbedtls_fprintf( stderr, "SetFilePointer(0,FILE_END) failed\n" );
goto exit;
}
filesize = li_size.QuadPart;
#else
if( ( filesize = lseek( fileno( fin ), 0, SEEK_END ) ) < 0 )
{
perror( "lseek" );
goto exit;
}
#endif
#endif
if( fseek( fin, 0, SEEK_SET ) < 0 )
{
mbedtls_fprintf( stderr, "fseek(0,SEEK_SET) failed\n" );
goto exit;
}
if( mode == MODE_ENCRYPT )
{
/*
* Generate the initialization vector as:
* IV = SHA-256( filesize || filename )[0..15]
*/
for( i = 0; i < 8; i++ )
buffer[i] = (unsigned char)( filesize >> ( i << 3 ) );
p = argv[2];
mbedtls_md_starts( &sha_ctx );
mbedtls_md_update( &sha_ctx, buffer, 8 );
mbedtls_md_update( &sha_ctx, (unsigned char *) p, strlen( p ) );
mbedtls_md_finish( &sha_ctx, digest );
memcpy( IV, digest, 16 );
/*
* The last four bits in the IV are actually used
* to store the file size modulo the AES block size.
*/
lastn = (int)( filesize & 0x0F );
IV[15] = (unsigned char)
( ( IV[15] & 0xF0 ) | lastn );
/*
* Append the IV at the beginning of the output.
*/
if( fwrite( IV, 1, 16, fout ) != 16 )
{
mbedtls_fprintf( stderr, "fwrite(%d bytes) failed\n", 16 );
goto exit;
}
/*
* Hash the IV and the secret key together 8192 times
* using the result to setup the AES context and HMAC.
*/
memset( digest, 0, 32 );
memcpy( digest, IV, 16 );
for( i = 0; i < 8192; i++ )
{
mbedtls_md_starts( &sha_ctx );
mbedtls_md_update( &sha_ctx, digest, 32 );
mbedtls_md_update( &sha_ctx, key, keylen );
mbedtls_md_finish( &sha_ctx, digest );
}
mbedtls_aes_setkey_enc( &aes_ctx, digest, 256 );
mbedtls_md_hmac_starts( &sha_ctx, digest, 32 );
/*
* Encrypt and write the ciphertext.
*/
for( offset = 0; offset < filesize; offset += 16 )
{
n = ( filesize - offset > 16 ) ? 16 : (int)
( filesize - offset );
if( fread( buffer, 1, n, fin ) != (size_t) n )
{
mbedtls_fprintf( stderr, "fread(%d bytes) failed\n", n );
goto exit;
}
for( i = 0; i < 16; i++ )
buffer[i] = (unsigned char)( buffer[i] ^ IV[i] );
mbedtls_aes_crypt_ecb( &aes_ctx, MBEDTLS_AES_ENCRYPT, buffer, buffer );
mbedtls_md_hmac_update( &sha_ctx, buffer, 16 );
if( fwrite( buffer, 1, 16, fout ) != 16 )
{
mbedtls_fprintf( stderr, "fwrite(%d bytes) failed\n", 16 );
goto exit;
}
memcpy( IV, buffer, 16 );
}
/*
* Finally write the HMAC.
*/
mbedtls_md_hmac_finish( &sha_ctx, digest );
if( fwrite( digest, 1, 32, fout ) != 32 )
{
mbedtls_fprintf( stderr, "fwrite(%d bytes) failed\n", 16 );
goto exit;
}
}
if( mode == MODE_DECRYPT )
{
/*
* The encrypted file must be structured as follows:
*
* 00 .. 15 Initialization Vector
* 16 .. 31 AES Encrypted Block #1
* ..
* N*16 .. (N+1)*16 - 1 AES Encrypted Block #N
* (N+1)*16 .. (N+1)*16 + 32 HMAC-SHA-256(ciphertext)
*/
if( filesize < 48 )
{
mbedtls_fprintf( stderr, "File too short to be encrypted.\n" );
goto exit;
}
if( ( filesize & 0x0F ) != 0 )
{
mbedtls_fprintf( stderr, "File size not a multiple of 16.\n" );
goto exit;
}
/*
* Subtract the IV + HMAC length.
*/
filesize -= ( 16 + 32 );
/*
* Read the IV and original filesize modulo 16.
*/
if( fread( buffer, 1, 16, fin ) != 16 )
{
mbedtls_fprintf( stderr, "fread(%d bytes) failed\n", 16 );
goto exit;
}
memcpy( IV, buffer, 16 );
lastn = IV[15] & 0x0F;
/*
* Hash the IV and the secret key together 8192 times
* using the result to setup the AES context and HMAC.
*/
memset( digest, 0, 32 );
memcpy( digest, IV, 16 );
for( i = 0; i < 8192; i++ )
{
mbedtls_md_starts( &sha_ctx );
mbedtls_md_update( &sha_ctx, digest, 32 );
mbedtls_md_update( &sha_ctx, key, keylen );
mbedtls_md_finish( &sha_ctx, digest );
}
mbedtls_aes_setkey_dec( &aes_ctx, digest, 256 );
mbedtls_md_hmac_starts( &sha_ctx, digest, 32 );
/*
* Decrypt and write the plaintext.
*/
for( offset = 0; offset < filesize; offset += 16 )
{
if( fread( buffer, 1, 16, fin ) != 16 )
{
mbedtls_fprintf( stderr, "fread(%d bytes) failed\n", 16 );
goto exit;
}
memcpy( tmp, buffer, 16 );
mbedtls_md_hmac_update( &sha_ctx, buffer, 16 );
mbedtls_aes_crypt_ecb( &aes_ctx, MBEDTLS_AES_DECRYPT, buffer, buffer );
for( i = 0; i < 16; i++ )
buffer[i] = (unsigned char)( buffer[i] ^ IV[i] );
memcpy( IV, tmp, 16 );
n = ( lastn > 0 && offset == filesize - 16 )
? lastn : 16;
if( fwrite( buffer, 1, n, fout ) != (size_t) n )
{
mbedtls_fprintf( stderr, "fwrite(%d bytes) failed\n", n );
goto exit;
}
}
/*
* Verify the message authentication code.
*/
mbedtls_md_hmac_finish( &sha_ctx, digest );
if( fread( buffer, 1, 32, fin ) != 32 )
{
mbedtls_fprintf( stderr, "fread(%d bytes) failed\n", 32 );
goto exit;
}
/* Use constant-time buffer comparison */
diff = 0;
for( i = 0; i < 32; i++ )
diff |= digest[i] ^ buffer[i];
if( diff != 0 )
{
mbedtls_fprintf( stderr, "HMAC check failed: wrong key, "
"or file corrupted.\n" );
goto exit;
}
}
exit_code = MBEDTLS_EXIT_SUCCESS;
exit:
if( fin )
fclose( fin );
if( fout )
fclose( fout );
/* Zeroize all command line arguments to also cover
the case when the user has missed or reordered some,
in which case the key might not be in argv[4]. */
for( i = 0; i < (unsigned int) argc; i++ )
mbedtls_zeroize( argv[i], strlen( argv[i] ) );
mbedtls_zeroize( IV, sizeof( IV ) );
mbedtls_zeroize( key, sizeof( key ) );
mbedtls_zeroize( tmp, sizeof( tmp ) );
mbedtls_zeroize( buffer, sizeof( buffer ) );
mbedtls_zeroize( digest, sizeof( digest ) );
mbedtls_aes_free( &aes_ctx );
mbedtls_md_free( &sha_ctx );
return( exit_code );
}
#endif /* MBEDTLS_AES_C && MBEDTLS_SHA256_C && MBEDTLS_FS_IO */
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