/*
* Diffie-Hellman-Merkle key exchange (client side)
*
* Copyright (C) 2006-2011, ARM Limited, All Rights Reserved
*
* This file is part of mbed TLS (https://polarssl.org)
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#if !defined(POLARSSL_CONFIG_FILE)
#include "polarssl/config.h"
#else
#include POLARSSL_CONFIG_FILE
#endif
#if defined(POLARSSL_PLATFORM_C)
#include "polarssl/platform.h"
#else
#define polarssl_printf printf
#endif
#include <string.h>
#include <stdio.h>
#include "polarssl/net.h"
#include "polarssl/aes.h"
#include "polarssl/dhm.h"
#include "polarssl/rsa.h"
#include "polarssl/sha1.h"
#include "polarssl/entropy.h"
#include "polarssl/ctr_drbg.h"
#define SERVER_NAME "localhost"
#define SERVER_PORT 11999
#if !defined(POLARSSL_AES_C) || !defined(POLARSSL_DHM_C) || \
!defined(POLARSSL_ENTROPY_C) || !defined(POLARSSL_NET_C) || \
!defined(POLARSSL_RSA_C) || !defined(POLARSSL_SHA256_C) || \
!defined(POLARSSL_FS_IO) || !defined(POLARSSL_CTR_DRBG_C)
int main( int argc, char *argv[] )
{
((void) argc);
((void) argv);
polarssl_printf("POLARSSL_AES_C and/or POLARSSL_DHM_C and/or POLARSSL_ENTROPY_C "
"and/or POLARSSL_NET_C and/or POLARSSL_RSA_C and/or "
"POLARSSL_SHA256_C and/or POLARSSL_FS_IO and/or "
"POLARSSL_CTR_DRBG_C not defined.\n");
return( 0 );
}
#else
int main( int argc, char *argv[] )
{
FILE *f;
int ret;
size_t n, buflen;
int server_fd = -1;
unsigned char *p, *end;
unsigned char buf[2048];
unsigned char hash[20];
const char *pers = "dh_client";
entropy_context entropy;
ctr_drbg_context ctr_drbg;
rsa_context rsa;
dhm_context dhm;
aes_context aes;
((void) argc);
((void) argv);
memset( &rsa, 0, sizeof( rsa ) );
dhm_init( &dhm );
aes_init( &aes );
/*
* 1. Setup the RNG
*/
polarssl_printf( "\n . Seeding the random number generator" );
fflush( stdout );
entropy_init( &entropy );
if( ( ret = ctr_drbg_init( &ctr_drbg, entropy_func, &entropy,
(const unsigned char *) pers,
strlen( pers ) ) ) != 0 )
{
polarssl_printf( " failed\n ! ctr_drbg_init returned %d\n", ret );
goto exit;
}
/*
* 2. Read the server's public RSA key
*/
polarssl_printf( "\n . Reading public key from rsa_pub.txt" );
fflush( stdout );
if( ( f = fopen( "rsa_pub.txt", "rb" ) ) == NULL )
{
ret = 1;
polarssl_printf( " failed\n ! Could not open rsa_pub.txt\n" \
" ! Please run rsa_genkey first\n\n" );
goto exit;
}
rsa_init( &rsa, RSA_PKCS_V15, 0 );
if( ( ret = mpi_read_file( &rsa.N, 16, f ) ) != 0 ||
( ret = mpi_read_file( &rsa.E, 16, f ) ) != 0 )
{
polarssl_printf( " failed\n ! mpi_read_file returned %d\n\n", ret );
goto exit;
}
rsa.len = ( mpi_msb( &rsa.N ) + 7 ) >> 3;
fclose( f );
/*
* 3. Initiate the connection
*/
polarssl_printf( "\n . Connecting to tcp/%s/%d", SERVER_NAME,
SERVER_PORT );
fflush( stdout );
if( ( ret = net_connect( &server_fd, SERVER_NAME,
SERVER_PORT ) ) != 0 )
{
polarssl_printf( " failed\n ! net_connect returned %d\n\n", ret );
goto exit;
}
/*
* 4a. First get the buffer length
*/
polarssl_printf( "\n . Receiving the server's DH parameters" );
fflush( stdout );
memset( buf, 0, sizeof( buf ) );
if( ( ret = net_recv( &server_fd, buf, 2 ) ) != 2 )
{
polarssl_printf( " failed\n ! net_recv returned %d\n\n", ret );
goto exit;
}
n = buflen = ( buf[0] << 8 ) | buf[1];
if( buflen < 1 || buflen > sizeof( buf ) )
{
polarssl_printf( " failed\n ! Got an invalid buffer length\n\n" );
goto exit;
}
/*
* 4b. Get the DHM parameters: P, G and Ys = G^Xs mod P
*/
memset( buf, 0, sizeof( buf ) );
if( ( ret = net_recv( &server_fd, buf, n ) ) != (int) n )
{
polarssl_printf( " failed\n ! net_recv returned %d\n\n", ret );
goto exit;
}
p = buf, end = buf + buflen;
if( ( ret = dhm_read_params( &dhm, &p, end ) ) != 0 )
{
polarssl_printf( " failed\n ! dhm_read_params returned %d\n\n", ret );
goto exit;
}
if( dhm.len < 64 || dhm.len > 512 )
{
ret = 1;
polarssl_printf( " failed\n ! Invalid DHM modulus size\n\n" );
goto exit;
}
/*
* 5. Check that the server's RSA signature matches
* the SHA-256 hash of (P,G,Ys)
*/
polarssl_printf( "\n . Verifying the server's RSA signature" );
fflush( stdout );
p += 2;
if( ( n = (size_t) ( end - p ) ) != rsa.len )
{
ret = 1;
polarssl_printf( " failed\n ! Invalid RSA signature size\n\n" );
goto exit;
}
sha1( buf, (int)( p - 2 - buf ), hash );
if( ( ret = rsa_pkcs1_verify( &rsa, NULL, NULL, RSA_PUBLIC,
POLARSSL_MD_SHA256, 0, hash, p ) ) != 0 )
{
polarssl_printf( " failed\n ! rsa_pkcs1_verify returned %d\n\n", ret );
goto exit;
}
/*
* 6. Send our public value: Yc = G ^ Xc mod P
*/
polarssl_printf( "\n . Sending own public value to server" );
fflush( stdout );
n = dhm.len;
if( ( ret = dhm_make_public( &dhm, (int) dhm.len, buf, n,
ctr_drbg_random, &ctr_drbg ) ) != 0 )
{
polarssl_printf( " failed\n ! dhm_make_public returned %d\n\n", ret );
goto exit;
}
if( ( ret = net_send( &server_fd, buf, n ) ) != (int) n )
{
polarssl_printf( " failed\n ! net_send returned %d\n\n", ret );
goto exit;
}
/*
* 7. Derive the shared secret: K = Ys ^ Xc mod P
*/
polarssl_printf( "\n . Shared secret: " );
fflush( stdout );
n = dhm.len;
if( ( ret = dhm_calc_secret( &dhm, buf, &n,
ctr_drbg_random, &ctr_drbg ) ) != 0 )
{
polarssl_printf( " failed\n ! dhm_calc_secret returned %d\n\n", ret );
goto exit;
}
for( n = 0; n < 16; n++ )
polarssl_printf( "%02x", buf[n] );
/*
* 8. Setup the AES-256 decryption key
*
* This is an overly simplified example; best practice is
* to hash the shared secret with a random value to derive
* the keying material for the encryption/decryption keys,
* IVs and MACs.
*/
polarssl_printf( "...\n . Receiving and decrypting the ciphertext" );
fflush( stdout );
aes_setkey_dec( &aes, buf, 256 );
memset( buf, 0, sizeof( buf ) );
if( ( ret = net_recv( &server_fd, buf, 16 ) ) != 16 )
{
polarssl_printf( " failed\n ! net_recv returned %d\n\n", ret );
goto exit;
}
aes_crypt_ecb( &aes, AES_DECRYPT, buf, buf );
buf[16] = '\0';
polarssl_printf( "\n . Plaintext is \"%s\"\n\n", (char *) buf );
exit:
if( server_fd != -1 )
net_close( server_fd );
aes_free( &aes );
rsa_free( &rsa );
dhm_free( &dhm );
ctr_drbg_free( &ctr_drbg );
entropy_free( &entropy );
#if defined(_WIN32)
polarssl_printf( " + Press Enter to exit this program.\n" );
fflush( stdout ); getchar();
#endif
return( ret );
}
#endif /* POLARSSL_AES_C && POLARSSL_DHM_C && POLARSSL_ENTROPY_C &&
POLARSSL_NET_C && POLARSSL_RSA_C && POLARSSL_SHA256_C &&
POLARSSL_FS_IO && POLARSSL_CTR_DRBG_C */