1 /*
2  *  Diffie-Hellman-Merkle key exchange (server side)
3  *
4  *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
5  *  SPDX-License-Identifier: Apache-2.0
6  *
7  *  Licensed under the Apache License, Version 2.0 (the "License"); you may
8  *  not use this file except in compliance with the License.
9  *  You may obtain a copy of the License at
10  *
11  *  http://www.apache.org/licenses/LICENSE-2.0
12  *
13  *  Unless required by applicable law or agreed to in writing, software
14  *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
15  *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16  *  See the License for the specific language governing permissions and
17  *  limitations under the License.
18  *
19  *  This file is part of mbed TLS (https://tls.mbed.org)
20  */
21 
22 #if !defined(MBEDTLS_CONFIG_FILE)
23 #include "mbedtls/config.h"
24 #else
25 #include MBEDTLS_CONFIG_FILE
26 #endif
27 
28 #if defined(MBEDTLS_PLATFORM_C)
29 #include "mbedtls/platform.h"
30 #else
31 #include <stdio.h>
32 #define mbedtls_printf     printf
33 #define mbedtls_time_t     time_t
34 #endif
35 
36 #if defined(MBEDTLS_AES_C) && defined(MBEDTLS_DHM_C) && \
37     defined(MBEDTLS_ENTROPY_C) && defined(MBEDTLS_NET_C) && \
38     defined(MBEDTLS_RSA_C) && defined(MBEDTLS_SHA256_C) && \
39     defined(MBEDTLS_FS_IO) && defined(MBEDTLS_CTR_DRBG_C) && \
40     defined(MBEDTLS_SHA1_C)
41 #include "mbedtls/net_sockets.h"
42 #include "mbedtls/aes.h"
43 #include "mbedtls/dhm.h"
44 #include "mbedtls/rsa.h"
45 #include "mbedtls/sha1.h"
46 #include "mbedtls/entropy.h"
47 #include "mbedtls/ctr_drbg.h"
48 
49 #include <stdio.h>
50 #include <string.h>
51 #endif
52 
53 #define SERVER_PORT "11999"
54 #define PLAINTEXT "==Hello there!=="
55 
56 #if !defined(MBEDTLS_AES_C) || !defined(MBEDTLS_DHM_C) ||     \
57     !defined(MBEDTLS_ENTROPY_C) || !defined(MBEDTLS_NET_C) ||  \
58     !defined(MBEDTLS_RSA_C) || !defined(MBEDTLS_SHA256_C) ||    \
59     !defined(MBEDTLS_FS_IO) || !defined(MBEDTLS_CTR_DRBG_C) || \
60     !defined(MBEDTLS_SHA1_C)
main(void)61 int main( void )
62 {
63     mbedtls_printf("MBEDTLS_AES_C and/or MBEDTLS_DHM_C and/or MBEDTLS_ENTROPY_C "
64            "and/or MBEDTLS_NET_C and/or MBEDTLS_RSA_C and/or "
65            "MBEDTLS_SHA256_C and/or MBEDTLS_FS_IO and/or "
66            "MBEDTLS_CTR_DRBG_C not defined.\n");
67     return( 0 );
68 }
69 #else
main(void)70 int main( void )
71 {
72     FILE *f;
73 
74     int ret;
75     size_t n, buflen;
76     mbedtls_net_context listen_fd, client_fd;
77 
78     unsigned char buf[2048];
79     unsigned char hash[32];
80     unsigned char buf2[2];
81     const char *pers = "dh_server";
82 
83     mbedtls_entropy_context entropy;
84     mbedtls_ctr_drbg_context ctr_drbg;
85     mbedtls_rsa_context rsa;
86     mbedtls_dhm_context dhm;
87     mbedtls_aes_context aes;
88 
89     mbedtls_net_init( &listen_fd );
90     mbedtls_net_init( &client_fd );
91     mbedtls_rsa_init( &rsa, MBEDTLS_RSA_PKCS_V15, MBEDTLS_MD_SHA256 );
92     mbedtls_dhm_init( &dhm );
93     mbedtls_aes_init( &aes );
94     mbedtls_ctr_drbg_init( &ctr_drbg );
95 
96     /*
97      * 1. Setup the RNG
98      */
99     mbedtls_printf( "\n  . Seeding the random number generator" );
100     fflush( stdout );
101 
102     mbedtls_entropy_init( &entropy );
103     if( ( ret = mbedtls_ctr_drbg_seed( &ctr_drbg, mbedtls_entropy_func, &entropy,
104                                (const unsigned char *) pers,
105                                strlen( pers ) ) ) != 0 )
106     {
107         mbedtls_printf( " failed\n  ! mbedtls_ctr_drbg_seed returned %d\n", ret );
108         goto exit;
109     }
110 
111     /*
112      * 2a. Read the server's private RSA key
113      */
114     mbedtls_printf( "\n  . Reading private key from rsa_priv.txt" );
115     fflush( stdout );
116 
117     if( ( f = fopen( "rsa_priv.txt", "rb" ) ) == NULL )
118     {
119         ret = 1;
120         mbedtls_printf( " failed\n  ! Could not open rsa_priv.txt\n" \
121                 "  ! Please run rsa_genkey first\n\n" );
122         goto exit;
123     }
124 
125     mbedtls_rsa_init( &rsa, MBEDTLS_RSA_PKCS_V15, 0 );
126 
127     if( ( ret = mbedtls_mpi_read_file( &rsa.N , 16, f ) ) != 0 ||
128         ( ret = mbedtls_mpi_read_file( &rsa.E , 16, f ) ) != 0 ||
129         ( ret = mbedtls_mpi_read_file( &rsa.D , 16, f ) ) != 0 ||
130         ( ret = mbedtls_mpi_read_file( &rsa.P , 16, f ) ) != 0 ||
131         ( ret = mbedtls_mpi_read_file( &rsa.Q , 16, f ) ) != 0 ||
132         ( ret = mbedtls_mpi_read_file( &rsa.DP, 16, f ) ) != 0 ||
133         ( ret = mbedtls_mpi_read_file( &rsa.DQ, 16, f ) ) != 0 ||
134         ( ret = mbedtls_mpi_read_file( &rsa.QP, 16, f ) ) != 0 )
135     {
136         mbedtls_printf( " failed\n  ! mbedtls_mpi_read_file returned %d\n\n", ret );
137         fclose( f );
138         goto exit;
139     }
140 
141     rsa.len = ( mbedtls_mpi_bitlen( &rsa.N ) + 7 ) >> 3;
142 
143     fclose( f );
144 
145     /*
146      * 2b. Get the DHM modulus and generator
147      */
148     mbedtls_printf( "\n  . Reading DH parameters from dh_prime.txt" );
149     fflush( stdout );
150 
151     if( ( f = fopen( "dh_prime.txt", "rb" ) ) == NULL )
152     {
153         ret = 1;
154         mbedtls_printf( " failed\n  ! Could not open dh_prime.txt\n" \
155                 "  ! Please run dh_genprime first\n\n" );
156         goto exit;
157     }
158 
159     if( mbedtls_mpi_read_file( &dhm.P, 16, f ) != 0 ||
160         mbedtls_mpi_read_file( &dhm.G, 16, f ) != 0 )
161     {
162         mbedtls_printf( " failed\n  ! Invalid DH parameter file\n\n" );
163         fclose( f );
164         goto exit;
165     }
166 
167     fclose( f );
168 
169     /*
170      * 3. Wait for a client to connect
171      */
172     mbedtls_printf( "\n  . Waiting for a remote connection" );
173     fflush( stdout );
174 
175     if( ( ret = mbedtls_net_bind( &listen_fd, NULL, SERVER_PORT, MBEDTLS_NET_PROTO_TCP ) ) != 0 )
176     {
177         mbedtls_printf( " failed\n  ! mbedtls_net_bind returned %d\n\n", ret );
178         goto exit;
179     }
180 
181     if( ( ret = mbedtls_net_accept( &listen_fd, &client_fd,
182                                     NULL, 0, NULL ) ) != 0 )
183     {
184         mbedtls_printf( " failed\n  ! mbedtls_net_accept returned %d\n\n", ret );
185         goto exit;
186     }
187 
188     /*
189      * 4. Setup the DH parameters (P,G,Ys)
190      */
191     mbedtls_printf( "\n  . Sending the server's DH parameters" );
192     fflush( stdout );
193 
194     memset( buf, 0, sizeof( buf ) );
195 
196     if( ( ret = mbedtls_dhm_make_params( &dhm, (int) mbedtls_mpi_size( &dhm.P ), buf, &n,
197                                  mbedtls_ctr_drbg_random, &ctr_drbg ) ) != 0 )
198     {
199         mbedtls_printf( " failed\n  ! mbedtls_dhm_make_params returned %d\n\n", ret );
200         goto exit;
201     }
202 
203     /*
204      * 5. Sign the parameters and send them
205      */
206     mbedtls_sha1( buf, n, hash );
207 
208     buf[n    ] = (unsigned char)( rsa.len >> 8 );
209     buf[n + 1] = (unsigned char)( rsa.len      );
210 
211     if( ( ret = mbedtls_rsa_pkcs1_sign( &rsa, NULL, NULL, MBEDTLS_RSA_PRIVATE, MBEDTLS_MD_SHA256,
212                                 0, hash, buf + n + 2 ) ) != 0 )
213     {
214         mbedtls_printf( " failed\n  ! mbedtls_rsa_pkcs1_sign returned %d\n\n", ret );
215         goto exit;
216     }
217 
218     buflen = n + 2 + rsa.len;
219     buf2[0] = (unsigned char)( buflen >> 8 );
220     buf2[1] = (unsigned char)( buflen      );
221 
222     if( ( ret = mbedtls_net_send( &client_fd, buf2, 2 ) ) != 2 ||
223         ( ret = mbedtls_net_send( &client_fd, buf, buflen ) ) != (int) buflen )
224     {
225         mbedtls_printf( " failed\n  ! mbedtls_net_send returned %d\n\n", ret );
226         goto exit;
227     }
228 
229     /*
230      * 6. Get the client's public value: Yc = G ^ Xc mod P
231      */
232     mbedtls_printf( "\n  . Receiving the client's public value" );
233     fflush( stdout );
234 
235     memset( buf, 0, sizeof( buf ) );
236 
237     if( ( ret = mbedtls_net_recv( &client_fd, buf, n ) ) != (int) n )
238     {
239         mbedtls_printf( " failed\n  ! mbedtls_net_recv returned %d\n\n", ret );
240         goto exit;
241     }
242 
243     if( ( ret = mbedtls_dhm_read_public( &dhm, buf, dhm.len ) ) != 0 )
244     {
245         mbedtls_printf( " failed\n  ! mbedtls_dhm_read_public returned %d\n\n", ret );
246         goto exit;
247     }
248 
249     /*
250      * 7. Derive the shared secret: K = Ys ^ Xc mod P
251      */
252     mbedtls_printf( "\n  . Shared secret: " );
253     fflush( stdout );
254 
255     if( ( ret = mbedtls_dhm_calc_secret( &dhm, buf, sizeof( buf ), &n,
256                                  mbedtls_ctr_drbg_random, &ctr_drbg ) ) != 0 )
257     {
258         mbedtls_printf( " failed\n  ! mbedtls_dhm_calc_secret returned %d\n\n", ret );
259         goto exit;
260     }
261 
262     for( n = 0; n < 16; n++ )
263         mbedtls_printf( "%02x", buf[n] );
264 
265     /*
266      * 8. Setup the AES-256 encryption key
267      *
268      * This is an overly simplified example; best practice is
269      * to hash the shared secret with a random value to derive
270      * the keying material for the encryption/decryption keys
271      * and MACs.
272      */
273     mbedtls_printf( "...\n  . Encrypting and sending the ciphertext" );
274     fflush( stdout );
275 
276     mbedtls_aes_setkey_enc( &aes, buf, 256 );
277     memcpy( buf, PLAINTEXT, 16 );
278     mbedtls_aes_crypt_ecb( &aes, MBEDTLS_AES_ENCRYPT, buf, buf );
279 
280     if( ( ret = mbedtls_net_send( &client_fd, buf, 16 ) ) != 16 )
281     {
282         mbedtls_printf( " failed\n  ! mbedtls_net_send returned %d\n\n", ret );
283         goto exit;
284     }
285 
286     mbedtls_printf( "\n\n" );
287 
288 exit:
289 
290     mbedtls_net_free( &client_fd );
291     mbedtls_net_free( &listen_fd );
292 
293     mbedtls_aes_free( &aes );
294     mbedtls_rsa_free( &rsa );
295     mbedtls_dhm_free( &dhm );
296     mbedtls_ctr_drbg_free( &ctr_drbg );
297     mbedtls_entropy_free( &entropy );
298 
299 #if defined(_WIN32)
300     mbedtls_printf( "  + Press Enter to exit this program.\n" );
301     fflush( stdout ); getchar();
302 #endif
303 
304     return( ret );
305 }
306 #endif /* MBEDTLS_AES_C && MBEDTLS_DHM_C && MBEDTLS_ENTROPY_C &&
307           MBEDTLS_NET_C && MBEDTLS_RSA_C && MBEDTLS_SHA256_C &&
308           MBEDTLS_FS_IO && MBEDTLS_CTR_DRBG_C */
309