aescrypt2.c

/*
 *  AES-256 file encryption program
 *
 *  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.
 */

/* Enable definition of fileno() even when compiling with -std=c99. Must be
 * set before config.h, which pulls in glibc's features.h indirectly.
 * Harmless on other platforms. */
#define _POSIX_C_SOURCE 200112L

#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            exit
#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 "mbedtls/platform_util.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");
    mbedtls_exit( 0 );
}
#else


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[64];
    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", (unsigned int) -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(%u 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(%u 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_platform_zeroize( argv[i], strlen( argv[i] ) );

    mbedtls_platform_zeroize( IV,     sizeof( IV ) );
    mbedtls_platform_zeroize( key,    sizeof( key ) );
    mbedtls_platform_zeroize( tmp,    sizeof( tmp ) );
    mbedtls_platform_zeroize( buffer, sizeof( buffer ) );
    mbedtls_platform_zeroize( digest, sizeof( digest ) );

    mbedtls_aes_free( &aes_ctx );
    mbedtls_md_free( &sha_ctx );

    mbedtls_exit( exit_code );
}
#endif /* MBEDTLS_AES_C && MBEDTLS_SHA256_C && MBEDTLS_FS_IO */