/* * Diffie-Hellman-Merkle key exchange (client side) * * Copyright (C) 2006-2010, Brainspark B.V. * * This file is part of PolarSSL (http://www.polarssl.org) * Lead Maintainer: Paul Bakker * * 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. */ #ifndef _CRT_SECURE_NO_DEPRECATE #define _CRT_SECURE_NO_DEPRECATE 1 #endif #include #include #include "polarssl/config.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_NAME "localhost" #define SERVER_PORT 11999 #if !defined(POLARSSL_AES_C) || !defined(POLARSSL_DHM_C) || \ !defined(POLARSSL_HAVEGE_C) || !defined(POLARSSL_NET_C) || \ !defined(POLARSSL_RSA_C) || !defined(POLARSSL_SHA1_C) || \ !defined(POLARSSL_FS_IO) int main( void ) { printf("POLARSSL_AES_C and/or POLARSSL_DHM_C and/or POLARSSL_HAVEGE_C " "and/or POLARSSL_NET_C and/or POLARSSL_RSA_C and/or " "POLARSSL_SHA1_C and/or POLARSSL_FS_IO not defined.\n"); return( 0 ); } #else int main( void ) { FILE *f; int ret; size_t n, buflen; int server_fd = -1; unsigned char *p, *end; unsigned char buf[1024]; unsigned char hash[20]; 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 ); /* * 2. Read the server's public RSA key */ printf( "\n . Reading public key from rsa_pub.txt" ); fflush( stdout ); if( ( f = fopen( "rsa_pub.txt", "rb" ) ) == NULL ) { ret = 1; 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 ) { 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 */ printf( "\n . Connecting to tcp/%s/%d", SERVER_NAME, SERVER_PORT ); fflush( stdout ); if( ( ret = net_connect( &server_fd, SERVER_NAME, SERVER_PORT ) ) != 0 ) { printf( " failed\n ! net_connect returned %d\n\n", ret ); goto exit; } /* * 4a. First get the buffer length */ printf( "\n . Receiving the server's DH parameters" ); fflush( stdout ); memset( buf, 0, sizeof( buf ) ); if( ( ret = net_recv( &server_fd, buf, 2 ) ) != 2 ) { 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 ) ) { 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 ) { 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 ) { printf( " failed\n ! dhm_read_params returned %d\n\n", ret ); goto exit; } if( dhm.len < 64 || dhm.len > 256 ) { ret = 1; printf( " failed\n ! Invalid DHM modulus size\n\n" ); goto exit; } /* * 5. Check that the server's RSA signature matches * the SHA-1 hash of (P,G,Ys) */ printf( "\n . Verifying the server's RSA signature" ); fflush( stdout ); if( ( n = (size_t) ( end - p ) ) != rsa.len ) { ret = 1; printf( " failed\n ! Invalid RSA signature size\n\n" ); goto exit; } sha1( buf, (int)( p - 2 - buf ), hash ); if( ( ret = rsa_pkcs1_verify( &rsa, RSA_PUBLIC, SIG_RSA_SHA1, 0, hash, p ) ) != 0 ) { printf( " failed\n ! rsa_pkcs1_verify returned %d\n\n", ret ); goto exit; } /* * 6. Send our public value: Yc = G ^ Xc mod P */ printf( "\n . Sending own public value to server" ); fflush( stdout ); n = dhm.len; if( ( ret = dhm_make_public( &dhm, 256, buf, n, havege_rand, &hs ) ) != 0 ) { printf( " failed\n ! dhm_make_public returned %d\n\n", ret ); goto exit; } if( ( ret = net_send( &server_fd, buf, n ) ) != (int) n ) { printf( " failed\n ! net_send returned %d\n\n", ret ); goto exit; } /* * 7. Derive the shared secret: K = Ys ^ Xc mod P */ printf( "\n . Shared secret: " ); fflush( stdout ); n = dhm.len; 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 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. */ 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 ) { printf( " failed\n ! net_recv returned %d\n\n", ret ); goto exit; } aes_crypt_ecb( &aes, AES_DECRYPT, buf, buf ); buf[16] = '\0'; printf( "\n . Plaintext is \"%s\"\n\n", (char *) buf ); exit: net_close( server_fd ); rsa_free( &rsa ); dhm_free( &dhm ); #ifdef WIN32 printf( " + Press Enter to exit this program.\n" ); fflush( stdout ); getchar(); #endif return( ret ); } #endif /* POLARSSL_AES_C && POLARSSL_DHM_C && POLARSSL_HAVEGE_C && POLARSSL_NET_C && POLARSSL_RSA_C && POLARSSL_SHA1_C && POLARSSL_FS_IO */