LittleFS AES

fileAES.cpp

/*
 *  \brief  Generic file encryption program using generic wrappers for configured
 *          security.
 *
 *  Copyright The Mbed TLS Contributors
 *  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 (originally crypt_and_hash.c) is modified by CC Dharmani (Jan 2022) to suit 
     R-Pi Pico, Arduino-mbed, renamed here as fileAES.cpp.
   * The main(argc,arg[v]) function declaration is replaced with fileAES(arguments) function.
   * Tested on Raspberry Pi Pico board (Arduino-mbed, on PlatformIO).
*/
#include "fileAES.h"

#if defined(MBEDTLS_CIPHER_C) && defined(MBEDTLS_MD_C) && defined(MBEDTLS_FS_IO)
#include "mbedtls/cipher.h"
#include "mbedtls/md.h"
#include "mbedtls/aes.h"
#include "mbedtls/platform_util.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <sys/types.h>
#include <unistd.h>


int fileAES (int modeIn, char* inFilename, char* outFilename, char* cipher, char* mbedtls_md, char* keyIn)
{
    int ret = 1, i;
    unsigned n;
    int exit_code = MBEDTLS_EXIT_FAILURE;
    int mode;
    size_t keylen, ilen, olen;
    FILE *fkey, *fin = NULL, *fout = NULL;

    char *p;
    unsigned char IV[16];
    unsigned char key[512];
    unsigned char digest[MBEDTLS_MD_MAX_SIZE];
    unsigned char buffer[512];
    unsigned char output[512];
    unsigned char diff;

    const mbedtls_cipher_info_t *cipher_info;
    const mbedtls_md_info_t *md_info;
    mbedtls_cipher_context_t cipher_ctx;
    mbedtls_md_context_t md_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_cipher_init( &cipher_ctx );
    mbedtls_md_init( &md_ctx );

    mode = modeIn;

    if( mode != MODE_ENCRYPT && mode != MODE_DECRYPT )
    {
        mbedtls_fprintf( stderr, "invalid operation mode\n" );
        goto exit;
    }

    if( strcmp( inFilename, outFilename) == 0 )
    {
        mbedtls_fprintf( stderr, "input and output filenames must differ\n" );
        goto exit;
    }

    if( ( fin = fopen( inFilename, "rb" ) ) == NULL )
    {
        mbedtls_fprintf( stderr, "fopen(%s,rb) failed\n", inFilename );
        goto exit;
    }

    if( ( fout = fopen( outFilename, "wb+" ) ) == NULL )
    {
        mbedtls_fprintf( stderr, "fopen(%s,wb+) failed\n", outFilename );
        goto exit;
    }

    /*
     * Read the Cipher and MD from the command line
     */
    cipher_info = mbedtls_cipher_info_from_string( cipher );
    if( cipher_info == NULL )
    {
        mbedtls_fprintf( stderr, "Cipher '%s' not found\n", cipher );
        goto exit;
    }
    if( ( ret = mbedtls_cipher_setup( &cipher_ctx, cipher_info) ) != 0 )
    {
        mbedtls_fprintf( stderr, "mbedtls_cipher_setup failed\n" );
        goto exit;
    }

    md_info = mbedtls_md_info_from_string( mbedtls_md );
    if( md_info == NULL )
    {
        mbedtls_fprintf( stderr, "Message Digest '%s' not found\n", mbedtls_md );
        goto exit;
    }

    if( mbedtls_md_setup( &md_ctx, md_info, 1 ) != 0 )
    {
        mbedtls_fprintf( stderr, "mbedtls_md_setup failed\n" );
        goto exit;
    }

    /*
     * Read the secret key from file or command line
     */
    if( ( fkey = fopen( keyIn, "rb" ) ) != NULL )
    {
        keylen = fread( key, 1, sizeof( key ), fkey );
        fclose( fkey );
    }
    else
    {
        if( memcmp( keyIn, "hex:", 4 ) == 0 )
        {
            p = &keyIn[4];
            keylen = 0;

            while( sscanf( p, "%02X", (unsigned int*) &n ) > 0 &&
                   keylen < (int) sizeof( key ) )
            {
                key[keylen++] = (unsigned char) n;
                p += 2;
            }
        }
        else
        {
            keylen = strlen( keyIn );

            if( keylen > (int) sizeof( key ) )
                keylen = (int) sizeof( key );

            memcpy( key, keyIn, 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(fseek(fin, 0L, SEEK_END) < 0)
    {
        perror( "fseek" );
        goto exit;
    }
    filesize = ftell(fin);
    //mbedtls_fprintf( stdout, "\nInput File size: %ld bytes\n", (long)filesize );
/*
    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 = MD( filesize || filename )[0..15]
         */
        for( i = 0; i < 8; i++ )
            buffer[i] = (unsigned char)( filesize >> ( i << 3 ) );

        p = inFilename;

        if( mbedtls_md_starts( &md_ctx ) != 0 )
        {
            mbedtls_fprintf( stderr, "mbedtls_md_starts() returned error\n" );
            goto exit;
        }
        if( mbedtls_md_update( &md_ctx, buffer, 8 ) != 0 )
        {
            mbedtls_fprintf( stderr, "mbedtls_md_update() returned error\n" );
            goto exit;
        }
        if( mbedtls_md_update( &md_ctx, ( unsigned char * ) p, strlen( p ) )
            != 0 )
        {
            mbedtls_fprintf( stderr, "mbedtls_md_update() returned error\n" );
            goto exit;
        }
        if( mbedtls_md_finish( &md_ctx, digest ) != 0 )
        {
            mbedtls_fprintf( stderr, "mbedtls_md_finish() returned error\n" );
            goto exit;
        }

        memcpy( IV, digest, 16 );
        /*
        mbedtls_fprintf( stdout, "\nEncode IV: " ); 
        for(int i=0; i<16; i++) mbedtls_fprintf( stdout, "0x%02x ", IV[i]);
         mbedtls_fprintf( stdout, "\n");
        */

        /*
         * 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++ )
        {
            if( mbedtls_md_starts( &md_ctx ) != 0 )
            {
                mbedtls_fprintf( stderr,
                                 "mbedtls_md_starts() returned error\n" );
                goto exit;
            }
            if( mbedtls_md_update( &md_ctx, digest, 32 ) != 0 )
            {
                mbedtls_fprintf( stderr,
                                 "mbedtls_md_update() returned error\n" );
                goto exit;
            }
            if( mbedtls_md_update( &md_ctx, key, keylen ) != 0 )
            {
                mbedtls_fprintf( stderr,
                                 "mbedtls_md_update() returned error\n" );
                goto exit;
            }
            if( mbedtls_md_finish( &md_ctx, digest ) != 0 )
            {
                mbedtls_fprintf( stderr,
                                 "mbedtls_md_finish() returned error\n" );
                goto exit;
            }

        }

        if( mbedtls_cipher_setkey( &cipher_ctx,
                                   digest,
                                   //(int) mbedtls_cipher_info_get_key_bitlen( cipher_info ),
                                   mbedtls_cipher_get_key_bitlen ( &cipher_ctx),
                           MBEDTLS_ENCRYPT ) != 0 )
        {
            mbedtls_fprintf( stderr, "mbedtls_cipher_setkey() returned error\n");
            goto exit;
        }
        
        if( mbedtls_cipher_set_iv( &cipher_ctx, IV, 16 ) != 0 )
        {
            mbedtls_fprintf( stderr, "mbedtls_cipher_set_iv() returned error\n");
            goto exit;
        }
        if( mbedtls_cipher_reset( &cipher_ctx ) != 0 )
        {
            mbedtls_fprintf( stderr, "mbedtls_cipher_reset() returned error\n");
            goto exit;
        }

        if( mbedtls_md_hmac_starts( &md_ctx, digest, 32 ) != 0 )
        {
            mbedtls_fprintf( stderr, "mbedtls_md_hmac_starts() returned error\n" );
            goto exit;
        }

        /*
         * Encrypt and write the ciphertext.
         */
        for( offset = 0; offset < filesize; offset += 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(%ld bytes) failed\n", (long) ilen );
                goto exit;
            }

            if( mbedtls_cipher_update( &cipher_ctx, buffer, ilen, output, &olen ) != 0 )
            {
                mbedtls_fprintf( stderr, "mbedtls_cipher_update() returned error\n");
                goto exit;
            }

            if( mbedtls_md_hmac_update( &md_ctx, output, olen ) != 0 )
            {
                mbedtls_fprintf( stderr, "mbedtls_md_hmac_update() returned error\n" );
                goto exit;
            }

            if( fwrite( output, 1, olen, fout ) != olen )
            {
                mbedtls_fprintf( stderr, "fwrite(%ld bytes) failed\n", (long) olen );
                goto exit;
            }
        }

        if( mbedtls_cipher_finish( &cipher_ctx, output, &olen ) != 0 )
        {
            mbedtls_fprintf( stderr, "mbedtls_cipher_finish() returned error\n" );
            goto exit;
        }
        if( mbedtls_md_hmac_update( &md_ctx, output, olen ) != 0 )
        {
            mbedtls_fprintf( stderr, "mbedtls_md_hmac_update() returned error\n" );
            goto exit;
        }

        if( fwrite( output, 1, olen, fout ) != olen )
        {
            mbedtls_fprintf( stderr, "fwrite(%ld bytes) failed\n", (long) olen );
            goto exit;
        }

        /*
         * Finally write the HMAC.
         */
        if( mbedtls_md_hmac_finish( &md_ctx, digest ) != 0 )
        {
            mbedtls_fprintf( stderr, "mbedtls_md_hmac_finish() returned error\n" );
            goto exit;
        }

        if( fwrite( digest, 1, mbedtls_md_get_size( md_info ), fout ) != mbedtls_md_get_size( md_info ) )
        {
            mbedtls_fprintf( stderr, "fwrite(%d bytes) failed\n", mbedtls_md_get_size( md_info ) );
            goto exit;
        }
    }


    if( mode == MODE_DECRYPT )
    {
        /*
         *  The encrypted file must be structured as follows:
         *
         *        00 .. 15              Initialization Vector
         *        16 .. 31              Encrypted Block #1
         *           ..
         *      N*16 .. (N+1)*16 - 1    Encrypted Block #N
         *  (N+1)*16 .. (N+1)*16 + n    Hash(ciphertext)
         */
        
        /*
        if( fread( buffer, 1, 16, fin ) != 16 )
        {
            mbedtls_fprintf( stderr, "fread(%d bytes) failed\n", 16 );
            goto exit;
        }

        mbedtls_fprintf( stdout, "\nRead IV: " ); 
        for(int i=0; i<16; i++) mbedtls_fprintf( stdout, "0x%02x ", buffer[i]);
         mbedtls_fprintf( stdout, "\n");
        fseek( fin, 0, SEEK_SET );
        */

        if( filesize < 16 + mbedtls_md_get_size( md_info ) )
        {
            mbedtls_fprintf( stderr, "File too short to be encrypted.\n" );
            goto exit;
        }

        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( mbedtls_cipher_info_get_mode( cipher_info ) != MBEDTLS_MODE_GCM &&
        if( mbedtls_cipher_get_cipher_mode( &cipher_ctx ) != 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 (%u).\n",
                     mbedtls_cipher_get_block_size( &cipher_ctx ));
            goto exit;
        }


        /*
         * Subtract the IV + HMAC length.
         */
        filesize -= ( 16 + mbedtls_md_get_size( md_info ) );

        /*
         * 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 );
        /*
        mbedtls_fprintf( stdout, "Decode IV: " ); //------------------------------------
        for(int i=0; i<16; i++) mbedtls_fprintf( stdout, "0x%02x ", IV[i]);
         mbedtls_fprintf( stdout, "\n");
        */
        /*
         * 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++ )
        {
            if( mbedtls_md_starts( &md_ctx ) != 0 )
            {
                mbedtls_fprintf( stderr, "mbedtls_md_starts() returned error\n" );
                goto exit;
            }
            if( mbedtls_md_update( &md_ctx, digest, 32 ) != 0 )
            {
                mbedtls_fprintf( stderr, "mbedtls_md_update() returned error\n" );
                goto exit;
            }
            if( mbedtls_md_update( &md_ctx, key, keylen ) != 0 )
            {
                mbedtls_fprintf( stderr, "mbedtls_md_update() returned error\n" );
                goto exit;
            }
            if( mbedtls_md_finish( &md_ctx, digest ) != 0 )
            {
                mbedtls_fprintf( stderr, "mbedtls_md_finish() returned error\n" );
                goto exit;
            }
        }

        if( mbedtls_cipher_setkey( &cipher_ctx,
                                   digest,
                                   //(int) mbedtls_cipher_info_get_key_bitlen( cipher_info ),
                                   mbedtls_cipher_get_key_bitlen( &cipher_ctx ),
                           MBEDTLS_DECRYPT ) != 0 )
        {
            mbedtls_fprintf( stderr, "mbedtls_cipher_setkey() returned error\n" );
            goto exit;
        }

        if( mbedtls_cipher_set_iv( &cipher_ctx, IV, 16 ) != 0 )
        {
            mbedtls_fprintf( stderr, "mbedtls_cipher_set_iv() returned error\n" );
            goto exit;
        }

        if( mbedtls_cipher_reset( &cipher_ctx ) != 0 )
        {
            mbedtls_fprintf( stderr, "mbedtls_cipher_reset() returned error\n" );
            goto exit;
        }

        if( mbedtls_md_hmac_starts( &md_ctx, digest, 32 ) != 0 )
        {
            mbedtls_fprintf( stderr, "mbedtls_md_hmac_starts() returned error\n" );
            goto exit;
        }

        /*
         * Decrypt and write the plaintext.
         */
        for( offset = 0; offset < filesize; offset += 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(%u bytes) failed\n",
                    mbedtls_cipher_get_block_size( &cipher_ctx ) );
                goto exit;
            }

            if( mbedtls_md_hmac_update( &md_ctx, buffer, ilen ) != 0 )
            {
                mbedtls_fprintf( stderr, "mbedtls_md_hmac_update() returned error\n" );
                goto exit;
            }
            if( mbedtls_cipher_update( &cipher_ctx, buffer, ilen, output,
                                       &olen ) != 0 )
            {
                mbedtls_fprintf( stderr, "mbedtls_cipher_update() returned error\n" );
                goto exit;
            }

            if( fwrite( output, 1, olen, fout ) != olen )
            {
                mbedtls_fprintf( stderr, "fwrite(%ld bytes) failed\n", (long) olen );
                goto exit;
            }
        }

        /*
         * Verify the message authentication code.
         */
        if( mbedtls_md_hmac_finish( &md_ctx, digest ) != 0 )
        {
            mbedtls_fprintf( stderr, "mbedtls_md_hmac_finish() returned error\n" );
            goto exit;
        }

        if( fread( buffer, 1, mbedtls_md_get_size( md_info ), fin ) != mbedtls_md_get_size( md_info ) )
        {
            mbedtls_fprintf( stderr, "fread(%d bytes) failed\n", mbedtls_md_get_size( md_info ) );
            goto exit;
        }

        /* Use constant-time buffer comparison */
        diff = 0;
        for( i = 0; i < mbedtls_md_get_size( md_info ); i++ )
            diff |= digest[i] ^ buffer[i];

        if( diff != 0 )
        {
            mbedtls_fprintf( stderr, "HMAC check failed: wrong key, "
                             "or file corrupted.\n" );
            goto exit;
        }

        /*
         * Write the final block of data
         */
        if( mbedtls_cipher_finish( &cipher_ctx, output, &olen ) != 0 )
        {
            mbedtls_fprintf( stderr, "mbedtls_cipher_finish() returned error\n" );
            goto exit;
        }

        if( fwrite( output, 1, olen, fout ) != olen )
        {
            mbedtls_fprintf( stderr, "fwrite(%ld bytes) failed\n", (long) olen );
            goto exit;
        }
    }

    exit_code = MBEDTLS_EXIT_SUCCESS;

exit:
    if( fin )
        fclose( fin );
    if( fout )
        fclose( fout );

    /* Zeroize all memory buffers used */
  
    mbedtls_platform_zeroize( IV,     sizeof( IV ) );
    mbedtls_platform_zeroize( key,    sizeof( key ) );
    mbedtls_platform_zeroize( buffer, sizeof( buffer ) );
    mbedtls_platform_zeroize( output, sizeof( output ) );
    mbedtls_platform_zeroize( digest, sizeof( digest ) );

    mbedtls_cipher_free( &cipher_ctx );
    mbedtls_md_free( &md_ctx );
    return( exit_code );
}
#endif