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Reliably zeroize sensitive data in AES sample application

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The AES sample application programs/aes/aescrypt2 could miss zeroizing
the stack-based key buffer in case of an error during operation. This
commit fixes this and also clears another temporary buffer as well as
all command line arguments (one of which might be the key) before exit.
This commit is contained in:
Hanno Becker 2017-06-27 08:24:34 +01:00 committed by Simon Butcher
parent f601ec5f34
commit ce37e6269e
1 changed files with 15 additions and 9 deletions
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24
programs/aes/aescrypt2.c
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@ -79,7 +79,9 @@ int main( int argc, char *argv[] )
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];
@ -123,10 +125,10 @@ int main( int argc, char *argv[] )
}
mode = atoi( argv[1] );
memset(IV, 0, sizeof(IV));
memset(key, 0, sizeof(key));
memset(digest, 0, sizeof(digest));
memset(buffer, 0, sizeof(buffer));
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 )
{
@ -185,8 +187,6 @@ int main( int argc, char *argv[] )
}
}
memset( argv[4], 0, strlen( argv[4] ) );
#if defined(_WIN32_WCE)
filesize = fseek( fin, 0L, SEEK_END );
#else
@ -272,7 +272,6 @@ int main( int argc, char *argv[] )
mbedtls_md_finish( &sha_ctx, digest );
}
memset( key, 0, sizeof( key ) );
mbedtls_aes_setkey_enc( &aes_ctx, digest, 256 );
mbedtls_md_hmac_starts( &sha_ctx, digest, 32 );
@ -319,7 +318,6 @@ int main( int argc, char *argv[] )
if( mode == MODE_DECRYPT )
{
unsigned char tmp[16];
/*
* The encrypted file must be structured as follows:
@ -374,7 +372,6 @@ int main( int argc, char *argv[] )
mbedtls_md_finish( &sha_ctx, digest );
}
memset( key, 0, sizeof( key ) );
mbedtls_aes_setkey_dec( &aes_ctx, digest, 256 );
mbedtls_md_hmac_starts( &sha_ctx, digest, 32 );
@ -441,6 +438,15 @@ exit:
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++ )
memset( argv[i], 0, strlen( argv[i] ) );
memset( IV, 0, sizeof( IV ) );
memset( key, 0, sizeof( key ) );
memset( tmp, 0, sizeof( tmp ) );
memset( buffer, 0, sizeof( buffer ) );
memset( digest, 0, sizeof( digest ) );