/*
* Diffie-Hellman-Merkle key exchange (server side)
*
* Copyright (C) 2006-2011, Brainspark B.V.
*
* This file is part of PolarSSL (http://www.polarssl.org)
* Lead Maintainer: Paul Bakker <polarssl_maintainer at polarssl.org>
*
* All rights reserved.
*
* 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
#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_PORT 11999
#define PLAINTEXT "==Hello there!=="
#if !defined(POLARSSL_AES_C) || !defined(POLARSSL_DHM_C) || \
!defined(POLARSSL_ENTROPY_C) || !defined(POLARSSL_NET_C) || \
!defined(POLARSSL_RSA_C) || !defined(POLARSSL_SHA1_C) || \
!defined(POLARSSL_FS_IO) || !defined(POLARSSL_CTR_DRBG_C)
int main( int argc, char *argv[] )
{
((void) argc);
((void) argv);
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_SHA1_C and/or POLARSSL_FS_IO and/or "
"POLARSSL_CTR_DBRG_C not defined.\n");
return( 0 );
}
#else
int main( int argc, char *argv[] )
{
FILE *f;
int ret;
size_t n, buflen;
int listen_fd = -1;
int client_fd = -1;
unsigned char buf[2048];
unsigned char hash[20];
unsigned char buf2[2];
const char *pers = "dh_server";
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
*/
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 )
{
printf( " failed\n ! ctr_drbg_init returned %d\n", ret );
goto exit;
}
/*
* 2a. Read the server's private RSA key
*/
printf( "\n . Reading private key from rsa_priv.txt" );
fflush( stdout );
if( ( f = fopen( "rsa_priv.txt", "rb" ) ) == NULL )
{
ret = 1;
printf( " failed\n ! Could not open rsa_priv.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 ||
( ret = mpi_read_file( &rsa.D , 16, f ) ) != 0 ||
( ret = mpi_read_file( &rsa.P , 16, f ) ) != 0 ||
( ret = mpi_read_file( &rsa.Q , 16, f ) ) != 0 ||
( ret = mpi_read_file( &rsa.DP, 16, f ) ) != 0 ||
( ret = mpi_read_file( &rsa.DQ, 16, f ) ) != 0 ||
( ret = mpi_read_file( &rsa.QP, 16, f ) ) != 0 )
{
printf( " failed\n ! mpi_read_file returned %d\n\n", ret );
goto exit;
}
rsa.len = ( mpi_msb( &rsa.N ) + 7 ) >> 3;
fclose( f );
/*
* 2b. Get the DHM modulus and generator
*/
printf( "\n . Reading DH parameters from dh_prime.txt" );
fflush( stdout );
if( ( f = fopen( "dh_prime.txt", "rb" ) ) == NULL )
{
ret = 1;
printf( " failed\n ! Could not open dh_prime.txt\n" \
" ! Please run dh_genprime first\n\n" );
goto exit;
}
if( mpi_read_file( &dhm.P, 16, f ) != 0 ||
mpi_read_file( &dhm.G, 16, f ) != 0 )
{
printf( " failed\n ! Invalid DH parameter file\n\n" );
goto exit;
}
fclose( f );
/*
* 3. Wait for a client to connect
*/
printf( "\n . Waiting for a remote connection" );
fflush( stdout );
if( ( ret = net_bind( &listen_fd, NULL, SERVER_PORT, NET_PROTO_TCP ) ) != 0 )
{
printf( " failed\n ! net_bind returned %d\n\n", ret );
goto exit;
}
if( ( ret = net_accept( listen_fd, &client_fd, NULL ) ) != 0 )
{
printf( " failed\n ! net_accept returned %d\n\n", ret );
goto exit;
}
/*
* 4. Setup the DH parameters (P,G,Ys)
*/
printf( "\n . Sending the server's DH parameters" );
fflush( stdout );
memset( buf, 0, sizeof( buf ) );
if( ( ret = dhm_make_params( &dhm, (int) mpi_size( &dhm.P ), buf, &n,
ctr_drbg_random, &ctr_drbg ) ) != 0 )
{
printf( " failed\n ! dhm_make_params returned %d\n\n", ret );
goto exit;
}
/*
* 5. Sign the parameters and send them
*/
sha1( buf, n, hash );
buf[n ] = (unsigned char)( rsa.len >> 8 );
buf[n + 1] = (unsigned char)( rsa.len );
if( ( ret = rsa_pkcs1_sign( &rsa, NULL, NULL, RSA_PRIVATE, POLARSSL_MD_SHA1,
0, hash, buf + n + 2 ) ) != 0 )
{
printf( " failed\n ! rsa_pkcs1_sign returned %d\n\n", ret );
goto exit;
}
buflen = n + 2 + rsa.len;
buf2[0] = (unsigned char)( buflen >> 8 );
buf2[1] = (unsigned char)( buflen );
if( ( ret = net_send( &client_fd, buf2, 2 ) ) != 2 ||
( ret = net_send( &client_fd, buf, buflen ) ) != (int) buflen )
{
printf( " failed\n ! net_send returned %d\n\n", ret );
goto exit;
}
/*
* 6. Get the client's public value: Yc = G ^ Xc mod P
*/
printf( "\n . Receiving the client's public value" );
fflush( stdout );
memset( buf, 0, sizeof( buf ) );
n = dhm.len;
if( ( ret = net_recv( &client_fd, buf, n ) ) != (int) n )
{
printf( " failed\n ! net_recv returned %d\n\n", ret );
goto exit;
}
if( ( ret = dhm_read_public( &dhm, buf, dhm.len ) ) != 0 )
{
printf( " failed\n ! dhm_read_public returned %d\n\n", ret );
goto exit;
}
/*
* 7. Derive the shared secret: K = Ys ^ Xc mod P
*/
printf( "\n . Shared secret: " );
fflush( stdout );
if( ( ret = dhm_calc_secret( &dhm, buf, &n,
ctr_drbg_random, &ctr_drbg ) ) != 0 )
{
printf( " failed\n ! dhm_calc_secret returned %d\n\n", ret );
goto exit;
}
for( n = 0; n < 16; n++ )
printf( "%02x", buf[n] );
/*
* 8. Setup the AES-256 encryption 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
* and MACs.
*/
printf( "...\n . Encrypting and sending the ciphertext" );
fflush( stdout );
aes_setkey_enc( &aes, buf, 256 );
memcpy( buf, PLAINTEXT, 16 );
aes_crypt_ecb( &aes, AES_ENCRYPT, buf, buf );
if( ( ret = net_send( &client_fd, buf, 16 ) ) != 16 )
{
printf( " failed\n ! net_send returned %d\n\n", ret );
goto exit;
}
printf( "\n\n" );
exit:
if( client_fd != -1 )
net_close( client_fd );
aes_free( &aes );
rsa_free( &rsa );
dhm_free( &dhm );
ctr_drbg_free( &ctr_drbg );
entropy_free( &entropy );
#if defined(_WIN32)
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_SHA1_C &&
POLARSSL_FS_IO && POLARSSL_CTR_DRBG_C */