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/*
* Diffie-Hellman-Merkle key exchange (server side)
*
* Based on XySSL: Copyright (C) 2006-2008 Christophe Devine
*
* Copyright (C) 2009 Paul Bakker <polarssl_maintainer at polarssl dot 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.
*/
#ifndef _CRT_SECURE_NO_DEPRECATE
#define _CRT_SECURE_NO_DEPRECATE 1
#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/havege.h"
#define SERVER_PORT 11999
#define PLAINTEXT "==Hello there!=="
int main( void )
{
FILE *f;
int ret, n, buflen;
int listen_fd = -1;
int client_fd = -1;
unsigned char buf[1024];
unsigned char hash[20];
unsigned char buf2[2];
havege_state hs;
rsa_context rsa;
dhm_context dhm;
aes_context aes;
memset( &rsa, 0, sizeof( rsa ) );
memset( &dhm, 0, sizeof( dhm ) );
/*
* 1. Setup the RNG
*/
printf( "\n . Seeding the random number generator" );
fflush( stdout );
havege_init( &hs );
/*
* 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, NULL, NULL );
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 ) ) != 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, 256, buf, &n,
havege_rand, &hs ) ) != 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, RSA_PRIVATE, SIG_RSA_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 ) ) != 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 ) ) != 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 ) ) != 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:
net_close( client_fd );
rsa_free( &rsa );
dhm_free( &dhm );
#ifdef WIN32
printf( " + Press Enter to exit this program.\n" );
fflush( stdout ); getchar();
#endif
return( ret );
}