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Fix for #441 - crypt and hash gcm (#546)

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* Fix crypt_and_hash to support decrypting GCM encrypted files

* Fix documentation in crypt_and_hash for the generic case

* Remove unused lastn from crypt_and_hash

lastn is not used with the cipher layer as it already provides padding
and understanding of length of the original data.
This commit is contained in:
Paul Bakker 2016-09-02 22:44:09 +02:00 committed by Simon Butcher
parent e88c9102e4
commit a9f02c8c21
1 changed files with 24 additions and 23 deletions
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47
programs/aes/crypt_and_hash.c
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@ -2,7 +2,7 @@
* \brief Generic file encryption program using generic wrappers for configured
* security.
*
* Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
* Copyright (C) 2006-2016, ARM Limited, All Rights Reserved
* SPDX-License-Identifier: Apache-2.0
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may
@ -74,7 +74,7 @@ int main( void )
int main( int argc, char *argv[] )
{
int ret = 1, i, n;
int mode, lastn;
int mode;
size_t keylen, ilen, olen;
FILE *fkey, *fin = NULL, *fout = NULL;
@ -259,7 +259,7 @@ int main( int argc, char *argv[] )
{
/*
* Generate the initialization vector as:
* IV = SHA-256( filesize || filename )[0..15]
* IV = MD( filesize || filename )[0..15]
*/
for( i = 0; i < 8; i++ )
buffer[i] = (unsigned char)( filesize >> ( i << 3 ) );
@ -273,15 +273,6 @@ int main( int argc, char *argv[] )
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.
*/
@ -388,10 +379,10 @@ int main( int argc, char *argv[] )
* The encrypted file must be structured as follows:
*
* 00 .. 15 Initialization Vector
* 16 .. 31 AES Encrypted Block #1
* 16 .. 31 Encrypted Block #1
* ..
* N*16 .. (N+1)*16 - 1 AES Encrypted Block #N
* (N+1)*16 .. (N+1)*16 + 32 HMAC-SHA-256(ciphertext)
* N*16 .. (N+1)*16 - 1 Encrypted Block #N
* (N+1)*16 .. (N+1)*16 + n Hash(ciphertext)
*/
if( filesize < 16 + mbedtls_md_get_size( md_info ) )
{
@ -399,7 +390,17 @@ int main( int argc, char *argv[] )
goto exit;
}
if( ( ( filesize - mbedtls_md_get_size( md_info ) ) %
if( mbedtls_cipher_get_block_size( &cipher_ctx ) == 0 )
{
mbedtls_fprintf( stderr, "Invalid cipher block size: 0. \n" );
goto exit;
}
/*
* Check the file size.
*/
if( cipher_info->mode != MBEDTLS_MODE_GCM &&
( ( filesize - mbedtls_md_get_size( md_info ) ) %
mbedtls_cipher_get_block_size( &cipher_ctx ) ) != 0 )
{
mbedtls_fprintf( stderr, "File content not a multiple of the block size (%d).\n",
@ -422,7 +423,6 @@ int main( int argc, char *argv[] )
}
memcpy( IV, buffer, 16 );
lastn = IV[15] & 0x0F;
/*
* Hash the IV and the secret key together 8192 times
@ -467,18 +467,19 @@ int main( int argc, char *argv[] )
*/
for( offset = 0; offset < filesize; offset += mbedtls_cipher_get_block_size( &cipher_ctx ) )
{
if( fread( buffer, 1, mbedtls_cipher_get_block_size( &cipher_ctx ), fin ) !=
(size_t) mbedtls_cipher_get_block_size( &cipher_ctx ) )
ilen = ( (unsigned int) filesize - offset > mbedtls_cipher_get_block_size( &cipher_ctx ) ) ?
mbedtls_cipher_get_block_size( &cipher_ctx ) : (unsigned int) ( filesize - offset );
if( fread( buffer, 1, ilen, fin ) != ilen )
{
mbedtls_fprintf( stderr, "fread(%d bytes) failed\n",
mbedtls_cipher_get_block_size( &cipher_ctx ) );
goto exit;
}
mbedtls_md_hmac_update( &md_ctx, buffer, mbedtls_cipher_get_block_size( &cipher_ctx ) );
if( mbedtls_cipher_update( &cipher_ctx, buffer,
mbedtls_cipher_get_block_size( &cipher_ctx ),
output, &olen ) != 0 )
mbedtls_md_hmac_update( &md_ctx, buffer, ilen );
if( mbedtls_cipher_update( &cipher_ctx, buffer, ilen, output,
&olen ) != 0 )
{
mbedtls_fprintf( stderr, "mbedtls_cipher_update() returned error\n" );
goto exit;