252 lines
6.5 KiB
C
252 lines
6.5 KiB
C
/*
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* Diffie-Hellman-Merkle key exchange (server side)
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*
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* Copyright (C) 2006-2007 Christophe Devine
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#ifndef _CRT_SECURE_NO_DEPRECATE
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#define _CRT_SECURE_NO_DEPRECATE 1
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#endif
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#include <string.h>
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#include <stdio.h>
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#include "polarssl/net.h"
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#include "polarssl/aes.h"
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#include "polarssl/dhm.h"
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#include "polarssl/rsa.h"
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#include "polarssl/sha1.h"
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#include "polarssl/havege.h"
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#define SERVER_PORT 11999
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#define PLAINTEXT "==Hello there!=="
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int main( void )
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{
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FILE *f;
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int ret, n, buflen;
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int listen_fd = -1;
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int client_fd = -1;
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unsigned char buf[1024];
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unsigned char hash[20];
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unsigned char buf2[2];
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havege_state hs;
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rsa_context rsa;
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dhm_context dhm;
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aes_context aes;
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memset( &rsa, 0, sizeof( rsa ) );
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memset( &dhm, 0, sizeof( dhm ) );
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/*
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* 1. Setup the RNG
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*/
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printf( "\n . Seeding the random number generator" );
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fflush( stdout );
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havege_init( &hs );
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/*
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* 2a. Read the server's private RSA key
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*/
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printf( "\n . Reading private key from rsa_priv.txt" );
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fflush( stdout );
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if( ( f = fopen( "rsa_priv.txt", "rb" ) ) == NULL )
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{
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ret = 1;
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printf( " failed\n ! Could not open rsa_priv.txt\n" \
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" ! Please run rsa_genkey first\n\n" );
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goto exit;
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}
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rsa_init( &rsa, RSA_PKCS_V15, 0, NULL, NULL );
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if( ( ret = mpi_read_file( &rsa.N , 16, f ) ) != 0 ||
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( ret = mpi_read_file( &rsa.E , 16, f ) ) != 0 ||
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( ret = mpi_read_file( &rsa.D , 16, f ) ) != 0 ||
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( ret = mpi_read_file( &rsa.P , 16, f ) ) != 0 ||
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( ret = mpi_read_file( &rsa.Q , 16, f ) ) != 0 ||
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( ret = mpi_read_file( &rsa.DP, 16, f ) ) != 0 ||
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( ret = mpi_read_file( &rsa.DQ, 16, f ) ) != 0 ||
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( ret = mpi_read_file( &rsa.QP, 16, f ) ) != 0 )
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{
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printf( " failed\n ! mpi_read_file returned %d\n\n", ret );
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goto exit;
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}
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rsa.len = ( mpi_msb( &rsa.N ) + 7 ) >> 3;
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fclose( f );
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/*
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* 2b. Get the DHM modulus and generator
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*/
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printf( "\n . Reading DH parameters from dh_prime.txt" );
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fflush( stdout );
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if( ( f = fopen( "dh_prime.txt", "rb" ) ) == NULL )
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{
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ret = 1;
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printf( " failed\n ! Could not open dh_prime.txt\n" \
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" ! Please run dh_genprime first\n\n" );
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goto exit;
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}
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if( mpi_read_file( &dhm.P, 16, f ) != 0 ||
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mpi_read_file( &dhm.G, 16, f ) != 0 )
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{
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printf( " failed\n ! Invalid DH parameter file\n\n" );
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goto exit;
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}
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fclose( f );
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/*
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* 3. Wait for a client to connect
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*/
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printf( "\n . Waiting for a remote connection" );
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fflush( stdout );
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if( ( ret = net_bind( &listen_fd, NULL, SERVER_PORT ) ) != 0 )
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{
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printf( " failed\n ! net_bind returned %d\n\n", ret );
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goto exit;
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}
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if( ( ret = net_accept( listen_fd, &client_fd, NULL ) ) != 0 )
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{
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printf( " failed\n ! net_accept returned %d\n\n", ret );
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goto exit;
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}
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/*
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* 4. Setup the DH parameters (P,G,Ys)
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*/
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printf( "\n . Sending the server's DH parameters" );
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fflush( stdout );
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memset( buf, 0, sizeof( buf ) );
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if( ( ret = dhm_make_params( &dhm, 256, buf, &n,
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havege_rand, &hs ) ) != 0 )
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{
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printf( " failed\n ! dhm_make_params returned %d\n\n", ret );
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goto exit;
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}
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/*
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* 5. Sign the parameters and send them
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*/
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sha1( buf, n, hash );
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buf[n ] = (unsigned char)( rsa.len >> 8 );
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buf[n + 1] = (unsigned char)( rsa.len );
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if( ( ret = rsa_pkcs1_sign( &rsa, RSA_PRIVATE, RSA_SHA1,
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0, hash, buf + n + 2 ) ) != 0 )
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{
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printf( " failed\n ! rsa_pkcs1_sign returned %d\n\n", ret );
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goto exit;
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}
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buflen = n + 2 + rsa.len;
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buf2[0] = (unsigned char)( buflen >> 8 );
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buf2[1] = (unsigned char)( buflen );
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if( ( ret = net_send( &client_fd, buf2, 2 ) ) != 2 ||
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( ret = net_send( &client_fd, buf, buflen ) ) != buflen )
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{
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printf( " failed\n ! net_send returned %d\n\n", ret );
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goto exit;
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}
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/*
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* 6. Get the client's public value: Yc = G ^ Xc mod P
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*/
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printf( "\n . Receiving the client's public value" );
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fflush( stdout );
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memset( buf, 0, sizeof( buf ) );
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n = dhm.len;
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if( ( ret = net_recv( &client_fd, buf, n ) ) != n )
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{
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printf( " failed\n ! net_recv returned %d\n\n", ret );
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goto exit;
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}
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if( ( ret = dhm_read_public( &dhm, buf, dhm.len ) ) != 0 )
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{
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printf( " failed\n ! dhm_read_public returned %d\n\n", ret );
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goto exit;
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}
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/*
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* 7. Derive the shared secret: K = Ys ^ Xc mod P
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*/
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printf( "\n . Shared secret: " );
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fflush( stdout );
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if( ( ret = dhm_calc_secret( &dhm, buf, &n ) ) != 0 )
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{
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printf( " failed\n ! dhm_calc_secret returned %d\n\n", ret );
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goto exit;
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}
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for( n = 0; n < 16; n++ )
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printf( "%02x", buf[n] );
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/*
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* 8. Setup the AES-256 encryption key
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*
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* This is an overly simplified example; best practice is
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* to hash the shared secret with a random value to derive
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* the keying material for the encryption/decryption keys
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* and MACs.
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*/
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printf( "...\n . Encrypting and sending the ciphertext" );
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fflush( stdout );
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aes_setkey_enc( &aes, buf, 256 );
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memcpy( buf, PLAINTEXT, 16 );
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aes_crypt_ecb( &aes, AES_ENCRYPT, buf, buf );
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if( ( ret = net_send( &client_fd, buf, 16 ) ) != 16 )
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{
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printf( " failed\n ! net_send returned %d\n\n", ret );
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goto exit;
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}
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printf( "\n\n" );
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exit:
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net_close( client_fd );
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rsa_free( &rsa );
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dhm_free( &dhm );
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#ifdef WIN32
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printf( " + Press Enter to exit this program.\n" );
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fflush( stdout ); getchar();
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#endif
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return( ret );
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}
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