290 lines
7.7 KiB
C
290 lines
7.7 KiB
C
/*
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* Diffie-Hellman-Merkle key exchange (client side)
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*
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* Copyright (C) 2006-2011, Brainspark B.V.
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*
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* This file is part of PolarSSL (http://www.polarssl.org)
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* Lead Maintainer: Paul Bakker <polarssl_maintainer at polarssl.org>
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*
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* All rights reserved.
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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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#include "polarssl/config.h"
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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/entropy.h"
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#include "polarssl/ctr_drbg.h"
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#define SERVER_NAME "localhost"
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#define SERVER_PORT 11999
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#if !defined(POLARSSL_AES_C) || !defined(POLARSSL_DHM_C) || \
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!defined(POLARSSL_ENTROPY_C) || !defined(POLARSSL_NET_C) || \
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!defined(POLARSSL_RSA_C) || !defined(POLARSSL_SHA1_C) || \
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!defined(POLARSSL_FS_IO) || !defined(POLARSSL_CTR_DRBG_C)
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int main( int argc, char *argv[] )
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{
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((void) argc);
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((void) argv);
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printf("POLARSSL_AES_C and/or POLARSSL_DHM_C and/or POLARSSL_ENTROPY_C "
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"and/or POLARSSL_NET_C and/or POLARSSL_RSA_C and/or "
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"POLARSSL_SHA1_C and/or POLARSSL_FS_IO and/or "
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"POLARSSL_CTR_DRBG_C not defined.\n");
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return( 0 );
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}
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#else
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int main( int argc, char *argv[] )
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{
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FILE *f;
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int ret;
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size_t n, buflen;
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int server_fd = -1;
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unsigned char *p, *end;
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unsigned char buf[2048];
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unsigned char hash[20];
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const char *pers = "dh_client";
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entropy_context entropy;
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ctr_drbg_context ctr_drbg;
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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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((void) argc);
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((void) argv);
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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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entropy_init( &entropy );
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if( ( ret = ctr_drbg_init( &ctr_drbg, entropy_func, &entropy,
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(const unsigned char *) pers,
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strlen( pers ) ) ) != 0 )
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{
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printf( " failed\n ! ctr_drbg_init returned %d\n", ret );
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goto exit;
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}
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/*
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* 2. Read the server's public RSA key
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*/
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printf( "\n . Reading public key from rsa_pub.txt" );
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fflush( stdout );
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if( ( f = fopen( "rsa_pub.txt", "rb" ) ) == NULL )
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{
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ret = 1;
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printf( " failed\n ! Could not open rsa_pub.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 );
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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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{
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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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* 3. Initiate the connection
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*/
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printf( "\n . Connecting to tcp/%s/%d", SERVER_NAME,
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SERVER_PORT );
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fflush( stdout );
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if( ( ret = net_connect( &server_fd, SERVER_NAME,
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SERVER_PORT ) ) != 0 )
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{
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printf( " failed\n ! net_connect returned %d\n\n", ret );
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goto exit;
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}
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/*
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* 4a. First get the buffer length
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*/
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printf( "\n . Receiving 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 = net_recv( &server_fd, buf, 2 ) ) != 2 )
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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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n = buflen = ( buf[0] << 8 ) | buf[1];
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if( buflen < 1 || buflen > sizeof( buf ) )
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{
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printf( " failed\n ! Got an invalid buffer length\n\n" );
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goto exit;
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}
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/*
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* 4b. Get the DHM parameters: P, G and Ys = G^Xs mod P
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*/
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memset( buf, 0, sizeof( buf ) );
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if( ( ret = net_recv( &server_fd, buf, n ) ) != (int) 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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p = buf, end = buf + buflen;
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if( ( ret = dhm_read_params( &dhm, &p, end ) ) != 0 )
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{
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printf( " failed\n ! dhm_read_params returned %d\n\n", ret );
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goto exit;
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}
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if( dhm.len < 64 || dhm.len > 512 )
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{
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ret = 1;
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printf( " failed\n ! Invalid DHM modulus size\n\n" );
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goto exit;
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}
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/*
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* 5. Check that the server's RSA signature matches
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* the SHA-1 hash of (P,G,Ys)
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*/
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printf( "\n . Verifying the server's RSA signature" );
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fflush( stdout );
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p += 2;
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if( ( n = (size_t) ( end - p ) ) != rsa.len )
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{
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ret = 1;
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printf( " failed\n ! Invalid RSA signature size\n\n" );
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goto exit;
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}
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sha1( buf, (int)( p - 2 - buf ), hash );
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if( ( ret = rsa_pkcs1_verify( &rsa, NULL, NULL, RSA_PUBLIC,
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POLARSSL_MD_SHA1, 0, hash, p ) ) != 0 )
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{
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printf( " failed\n ! rsa_pkcs1_verify returned %d\n\n", ret );
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goto exit;
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}
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/*
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* 6. Send our public value: Yc = G ^ Xc mod P
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*/
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printf( "\n . Sending own public value to server" );
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fflush( stdout );
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n = dhm.len;
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if( ( ret = dhm_make_public( &dhm, (int) dhm.len, buf, n,
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ctr_drbg_random, &ctr_drbg ) ) != 0 )
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{
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printf( " failed\n ! dhm_make_public returned %d\n\n", ret );
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goto exit;
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}
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if( ( ret = net_send( &server_fd, buf, n ) ) != (int) n )
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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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* 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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n = dhm.len;
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if( ( ret = dhm_calc_secret( &dhm, buf, &n,
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ctr_drbg_random, &ctr_drbg ) ) != 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 decryption 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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* IVs and MACs.
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*/
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printf( "...\n . Receiving and decrypting the ciphertext" );
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fflush( stdout );
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aes_setkey_dec( &aes, buf, 256 );
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memset( buf, 0, sizeof( buf ) );
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if( ( ret = net_recv( &server_fd, buf, 16 ) ) != 16 )
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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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aes_crypt_ecb( &aes, AES_DECRYPT, buf, buf );
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buf[16] = '\0';
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printf( "\n . Plaintext is \"%s\"\n\n", (char *) buf );
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exit:
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net_close( server_fd );
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rsa_free( &rsa );
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dhm_free( &dhm );
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entropy_free( &entropy );
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#if defined(_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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#endif /* POLARSSL_AES_C && POLARSSL_DHM_C && POLARSSL_ENTROPY_C &&
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POLARSSL_NET_C && POLARSSL_RSA_C && POLARSSL_SHA1_C &&
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POLARSSL_FS_IO && POLARSSL_CTR_DRBG_C */
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