/* * Diffie-Hellman-Merkle key exchange (server side) * * Based on XySSL: Copyright (C) 2006-2008 Christophe Devine * * Copyright (C) 2009 Paul Bakker * * 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 #include #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 ); }