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 #include <stdlib.h>
33 #define mbedtls_printf          printf
34 #define mbedtls_time_t          time_t
35 #define mbedtls_exit            exit
36 #define MBEDTLS_EXIT_SUCCESS    EXIT_SUCCESS
37 #define MBEDTLS_EXIT_FAILURE    EXIT_FAILURE
38 #endif /* MBEDTLS_PLATFORM_C */
39 
40 #if defined(MBEDTLS_AES_C) && defined(MBEDTLS_DHM_C) && \
41     defined(MBEDTLS_ENTROPY_C) && defined(MBEDTLS_NET_C) && \
42     defined(MBEDTLS_RSA_C) && defined(MBEDTLS_SHA256_C) && \
43     defined(MBEDTLS_FS_IO) && defined(MBEDTLS_CTR_DRBG_C) && \
44     defined(MBEDTLS_SHA1_C)
45 #include "mbedtls/net_sockets.h"
46 #include "mbedtls/aes.h"
47 #include "mbedtls/dhm.h"
48 #include "mbedtls/rsa.h"
49 #include "mbedtls/sha1.h"
50 #include "mbedtls/entropy.h"
51 #include "mbedtls/ctr_drbg.h"
52 
53 #include <stdio.h>
54 #include <string.h>
55 #endif
56 
57 #define SERVER_PORT "11999"
58 #define PLAINTEXT "==Hello there!=="
59 
60 #if !defined(MBEDTLS_AES_C) || !defined(MBEDTLS_DHM_C) ||     \
61     !defined(MBEDTLS_ENTROPY_C) || !defined(MBEDTLS_NET_C) ||  \
62     !defined(MBEDTLS_RSA_C) || !defined(MBEDTLS_SHA256_C) ||    \
63     !defined(MBEDTLS_FS_IO) || !defined(MBEDTLS_CTR_DRBG_C) || \
64     !defined(MBEDTLS_SHA1_C)
main(void)65 int main( void )
66 {
67     mbedtls_printf("MBEDTLS_AES_C and/or MBEDTLS_DHM_C and/or MBEDTLS_ENTROPY_C "
68            "and/or MBEDTLS_NET_C and/or MBEDTLS_RSA_C and/or "
69            "MBEDTLS_SHA256_C and/or MBEDTLS_FS_IO and/or "
70            "MBEDTLS_CTR_DRBG_C not defined.\n");
71     return( 0 );
72 }
73 #else
74 
75 #if defined(MBEDTLS_CHECK_PARAMS)
76 #include "mbedtls/platform_util.h"
mbedtls_param_failed(const char * failure_condition,const char * file,int line)77 void mbedtls_param_failed( const char *failure_condition,
78                            const char *file,
79                            int line )
80 {
81     mbedtls_printf( "%s:%i: Input param failed - %s\n",
82                     file, line, failure_condition );
83     mbedtls_exit( MBEDTLS_EXIT_FAILURE );
84 }
85 #endif
86 
main(void)87 int main( void )
88 {
89     FILE *f;
90 
91     int ret = 1;
92     int exit_code = MBEDTLS_EXIT_FAILURE;
93     size_t n, buflen;
94     mbedtls_net_context listen_fd, client_fd;
95 
96     unsigned char buf[2048];
97     unsigned char hash[32];
98     unsigned char buf2[2];
99     const char *pers = "dh_server";
100 
101     mbedtls_entropy_context entropy;
102     mbedtls_ctr_drbg_context ctr_drbg;
103     mbedtls_rsa_context rsa;
104     mbedtls_dhm_context dhm;
105     mbedtls_aes_context aes;
106 
107     mbedtls_mpi N, P, Q, D, E;
108 
109     mbedtls_net_init( &listen_fd );
110     mbedtls_net_init( &client_fd );
111     mbedtls_rsa_init( &rsa, MBEDTLS_RSA_PKCS_V15, MBEDTLS_MD_SHA256 );
112     mbedtls_dhm_init( &dhm );
113     mbedtls_aes_init( &aes );
114     mbedtls_ctr_drbg_init( &ctr_drbg );
115 
116     mbedtls_mpi_init( &N ); mbedtls_mpi_init( &P ); mbedtls_mpi_init( &Q );
117     mbedtls_mpi_init( &D ); mbedtls_mpi_init( &E );
118 
119     /*
120      * 1. Setup the RNG
121      */
122     mbedtls_printf( "\n  . Seeding the random number generator" );
123     fflush( stdout );
124 
125     mbedtls_entropy_init( &entropy );
126     if( ( ret = mbedtls_ctr_drbg_seed( &ctr_drbg, mbedtls_entropy_func, &entropy,
127                                (const unsigned char *) pers,
128                                strlen( pers ) ) ) != 0 )
129     {
130         mbedtls_printf( " failed\n  ! mbedtls_ctr_drbg_seed returned %d\n", ret );
131         goto exit;
132     }
133 
134     /*
135      * 2a. Read the server's private RSA key
136      */
137     mbedtls_printf( "\n  . Reading private key from rsa_priv.txt" );
138     fflush( stdout );
139 
140     if( ( f = fopen( "rsa_priv.txt", "rb" ) ) == NULL )
141     {
142         mbedtls_printf( " failed\n  ! Could not open rsa_priv.txt\n" \
143                 "  ! Please run rsa_genkey first\n\n" );
144         goto exit;
145     }
146 
147     mbedtls_rsa_init( &rsa, MBEDTLS_RSA_PKCS_V15, 0 );
148 
149     if( ( ret = mbedtls_mpi_read_file( &N , 16, f ) ) != 0 ||
150         ( ret = mbedtls_mpi_read_file( &E , 16, f ) ) != 0 ||
151         ( ret = mbedtls_mpi_read_file( &D , 16, f ) ) != 0 ||
152         ( ret = mbedtls_mpi_read_file( &P , 16, f ) ) != 0 ||
153         ( ret = mbedtls_mpi_read_file( &Q , 16, f ) ) != 0 )
154     {
155         mbedtls_printf( " failed\n  ! mbedtls_mpi_read_file returned %d\n\n",
156                         ret );
157         fclose( f );
158         goto exit;
159     }
160     fclose( f );
161 
162     if( ( ret = mbedtls_rsa_import( &rsa, &N, &P, &Q, &D, &E ) ) != 0 )
163     {
164         mbedtls_printf( " failed\n  ! mbedtls_rsa_import returned %d\n\n",
165                         ret );
166         goto exit;
167     }
168 
169     if( ( ret = mbedtls_rsa_complete( &rsa ) ) != 0 )
170     {
171         mbedtls_printf( " failed\n  ! mbedtls_rsa_complete returned %d\n\n",
172                         ret );
173         goto exit;
174     }
175 
176     /*
177      * 2b. Get the DHM modulus and generator
178      */
179     mbedtls_printf( "\n  . Reading DH parameters from dh_prime.txt" );
180     fflush( stdout );
181 
182     if( ( f = fopen( "dh_prime.txt", "rb" ) ) == NULL )
183     {
184         mbedtls_printf( " failed\n  ! Could not open dh_prime.txt\n" \
185                 "  ! Please run dh_genprime first\n\n" );
186         goto exit;
187     }
188 
189     if( mbedtls_mpi_read_file( &dhm.P, 16, f ) != 0 ||
190         mbedtls_mpi_read_file( &dhm.G, 16, f ) != 0 )
191     {
192         mbedtls_printf( " failed\n  ! Invalid DH parameter file\n\n" );
193         fclose( f );
194         goto exit;
195     }
196 
197     fclose( f );
198 
199     /*
200      * 3. Wait for a client to connect
201      */
202     mbedtls_printf( "\n  . Waiting for a remote connection" );
203     fflush( stdout );
204 
205     if( ( ret = mbedtls_net_bind( &listen_fd, NULL, SERVER_PORT, MBEDTLS_NET_PROTO_TCP ) ) != 0 )
206     {
207         mbedtls_printf( " failed\n  ! mbedtls_net_bind returned %d\n\n", ret );
208         goto exit;
209     }
210 
211     if( ( ret = mbedtls_net_accept( &listen_fd, &client_fd,
212                                     NULL, 0, NULL ) ) != 0 )
213     {
214         mbedtls_printf( " failed\n  ! mbedtls_net_accept returned %d\n\n", ret );
215         goto exit;
216     }
217 
218     /*
219      * 4. Setup the DH parameters (P,G,Ys)
220      */
221     mbedtls_printf( "\n  . Sending the server's DH parameters" );
222     fflush( stdout );
223 
224     memset( buf, 0, sizeof( buf ) );
225 
226     if( ( ret = mbedtls_dhm_make_params( &dhm, (int) mbedtls_mpi_size( &dhm.P ), buf, &n,
227                                  mbedtls_ctr_drbg_random, &ctr_drbg ) ) != 0 )
228     {
229         mbedtls_printf( " failed\n  ! mbedtls_dhm_make_params returned %d\n\n", ret );
230         goto exit;
231     }
232 
233     /*
234      * 5. Sign the parameters and send them
235      */
236     if( ( ret = mbedtls_sha1_ret( buf, n, hash ) ) != 0 )
237     {
238         mbedtls_printf( " failed\n  ! mbedtls_sha1_ret returned %d\n\n", ret );
239         goto exit;
240     }
241 
242     buf[n    ] = (unsigned char)( rsa.len >> 8 );
243     buf[n + 1] = (unsigned char)( rsa.len      );
244 
245     if( ( ret = mbedtls_rsa_pkcs1_sign( &rsa, NULL, NULL, MBEDTLS_RSA_PRIVATE, MBEDTLS_MD_SHA256,
246                                 0, hash, buf + n + 2 ) ) != 0 )
247     {
248         mbedtls_printf( " failed\n  ! mbedtls_rsa_pkcs1_sign returned %d\n\n", ret );
249         goto exit;
250     }
251 
252     buflen = n + 2 + rsa.len;
253     buf2[0] = (unsigned char)( buflen >> 8 );
254     buf2[1] = (unsigned char)( buflen      );
255 
256     if( ( ret = mbedtls_net_send( &client_fd, buf2, 2 ) ) != 2 ||
257         ( ret = mbedtls_net_send( &client_fd, buf, buflen ) ) != (int) buflen )
258     {
259         mbedtls_printf( " failed\n  ! mbedtls_net_send returned %d\n\n", ret );
260         goto exit;
261     }
262 
263     /*
264      * 6. Get the client's public value: Yc = G ^ Xc mod P
265      */
266     mbedtls_printf( "\n  . Receiving the client's public value" );
267     fflush( stdout );
268 
269     memset( buf, 0, sizeof( buf ) );
270 
271     n = dhm.len;
272     if( ( ret = mbedtls_net_recv( &client_fd, buf, n ) ) != (int) n )
273     {
274         mbedtls_printf( " failed\n  ! mbedtls_net_recv returned %d\n\n", ret );
275         goto exit;
276     }
277 
278     if( ( ret = mbedtls_dhm_read_public( &dhm, buf, dhm.len ) ) != 0 )
279     {
280         mbedtls_printf( " failed\n  ! mbedtls_dhm_read_public returned %d\n\n", ret );
281         goto exit;
282     }
283 
284     /*
285      * 7. Derive the shared secret: K = Ys ^ Xc mod P
286      */
287     mbedtls_printf( "\n  . Shared secret: " );
288     fflush( stdout );
289 
290     if( ( ret = mbedtls_dhm_calc_secret( &dhm, buf, sizeof( buf ), &n,
291                                  mbedtls_ctr_drbg_random, &ctr_drbg ) ) != 0 )
292     {
293         mbedtls_printf( " failed\n  ! mbedtls_dhm_calc_secret returned %d\n\n", ret );
294         goto exit;
295     }
296 
297     for( n = 0; n < 16; n++ )
298         mbedtls_printf( "%02x", buf[n] );
299 
300     /*
301      * 8. Setup the AES-256 encryption key
302      *
303      * This is an overly simplified example; best practice is
304      * to hash the shared secret with a random value to derive
305      * the keying material for the encryption/decryption keys
306      * and MACs.
307      */
308     mbedtls_printf( "...\n  . Encrypting and sending the ciphertext" );
309     fflush( stdout );
310 
311     mbedtls_aes_setkey_enc( &aes, buf, 256 );
312     memcpy( buf, PLAINTEXT, 16 );
313     mbedtls_aes_crypt_ecb( &aes, MBEDTLS_AES_ENCRYPT, buf, buf );
314 
315     if( ( ret = mbedtls_net_send( &client_fd, buf, 16 ) ) != 16 )
316     {
317         mbedtls_printf( " failed\n  ! mbedtls_net_send returned %d\n\n", ret );
318         goto exit;
319     }
320 
321     mbedtls_printf( "\n\n" );
322 
323     exit_code = MBEDTLS_EXIT_SUCCESS;
324 
325 exit:
326 
327     mbedtls_mpi_free( &N ); mbedtls_mpi_free( &P ); mbedtls_mpi_free( &Q );
328     mbedtls_mpi_free( &D ); mbedtls_mpi_free( &E );
329 
330     mbedtls_net_free( &client_fd );
331     mbedtls_net_free( &listen_fd );
332 
333     mbedtls_aes_free( &aes );
334     mbedtls_rsa_free( &rsa );
335     mbedtls_dhm_free( &dhm );
336     mbedtls_ctr_drbg_free( &ctr_drbg );
337     mbedtls_entropy_free( &entropy );
338 
339 #if defined(_WIN32)
340     mbedtls_printf( "  + Press Enter to exit this program.\n" );
341     fflush( stdout ); getchar();
342 #endif
343 
344     return( exit_code );
345 }
346 #endif /* MBEDTLS_AES_C && MBEDTLS_DHM_C && MBEDTLS_ENTROPY_C &&
347           MBEDTLS_NET_C && MBEDTLS_RSA_C && MBEDTLS_SHA256_C &&
348           MBEDTLS_FS_IO && MBEDTLS_CTR_DRBG_C */
349