1 /*
2 * Diffie-Hellman-Merkle key exchange (prime generation)
3 *
4 * Copyright The Mbed TLS Contributors
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
20 #include "mbedtls/build_info.h"
21
22 #if defined(MBEDTLS_PLATFORM_C)
23 #include "mbedtls/platform.h"
24 #else
25 #include <stdio.h>
26 #include <stdlib.h>
27 #define mbedtls_printf printf
28 #define mbedtls_time_t time_t
29 #define mbedtls_exit exit
30 #define MBEDTLS_EXIT_SUCCESS EXIT_SUCCESS
31 #define MBEDTLS_EXIT_FAILURE EXIT_FAILURE
32 #endif /* MBEDTLS_PLATFORM_C */
33
34 #if !defined(MBEDTLS_BIGNUM_C) || !defined(MBEDTLS_ENTROPY_C) || \
35 !defined(MBEDTLS_FS_IO) || !defined(MBEDTLS_CTR_DRBG_C) || \
36 !defined(MBEDTLS_GENPRIME)
main(void)37 int main( void )
38 {
39 mbedtls_printf("MBEDTLS_BIGNUM_C and/or MBEDTLS_ENTROPY_C and/or "
40 "MBEDTLS_FS_IO and/or MBEDTLS_CTR_DRBG_C and/or "
41 "MBEDTLS_GENPRIME not defined.\n");
42 mbedtls_exit( 0 );
43 }
44 #else
45
46 #include "mbedtls/bignum.h"
47 #include "mbedtls/entropy.h"
48 #include "mbedtls/ctr_drbg.h"
49
50 #include <stdio.h>
51 #include <string.h>
52
53 #define USAGE \
54 "\n usage: dh_genprime param=<>...\n" \
55 "\n acceprable parameters:\n" \
56 " bits=%%d default: 2048\n"
57
58 #define DFL_BITS 2048
59
60 /*
61 * Note: G = 4 is always a quadratic residue mod P,
62 * so it is a generator of order Q (with P = 2*Q+1).
63 */
64 #define GENERATOR "4"
65
66
main(int argc,char ** argv)67 int main( int argc, char **argv )
68 {
69 int ret = 1;
70 int exit_code = MBEDTLS_EXIT_FAILURE;
71 mbedtls_mpi G, P, Q;
72 mbedtls_entropy_context entropy;
73 mbedtls_ctr_drbg_context ctr_drbg;
74 const char *pers = "dh_genprime";
75 FILE *fout;
76 int nbits = DFL_BITS;
77 int i;
78 char *p, *q;
79
80 mbedtls_mpi_init( &G ); mbedtls_mpi_init( &P ); mbedtls_mpi_init( &Q );
81 mbedtls_ctr_drbg_init( &ctr_drbg );
82 mbedtls_entropy_init( &entropy );
83
84 if( argc == 0 )
85 {
86 usage:
87 mbedtls_printf( USAGE );
88 goto exit;
89 }
90
91 for( i = 1; i < argc; i++ )
92 {
93 p = argv[i];
94 if( ( q = strchr( p, '=' ) ) == NULL )
95 goto usage;
96 *q++ = '\0';
97
98 if( strcmp( p, "bits" ) == 0 )
99 {
100 nbits = atoi( q );
101 if( nbits < 0 || nbits > MBEDTLS_MPI_MAX_BITS )
102 goto usage;
103 }
104 else
105 goto usage;
106 }
107
108 if( ( ret = mbedtls_mpi_read_string( &G, 10, GENERATOR ) ) != 0 )
109 {
110 mbedtls_printf( " failed\n ! mbedtls_mpi_read_string returned %d\n", ret );
111 goto exit;
112 }
113
114 mbedtls_printf( " ! Generating large primes may take minutes!\n" );
115
116 mbedtls_printf( "\n . Seeding the random number generator..." );
117 fflush( stdout );
118
119 if( ( ret = mbedtls_ctr_drbg_seed( &ctr_drbg, mbedtls_entropy_func, &entropy,
120 (const unsigned char *) pers,
121 strlen( pers ) ) ) != 0 )
122 {
123 mbedtls_printf( " failed\n ! mbedtls_ctr_drbg_seed returned %d\n", ret );
124 goto exit;
125 }
126
127 mbedtls_printf( " ok\n . Generating the modulus, please wait..." );
128 fflush( stdout );
129
130 /*
131 * This can take a long time...
132 */
133 if( ( ret = mbedtls_mpi_gen_prime( &P, nbits, 1,
134 mbedtls_ctr_drbg_random, &ctr_drbg ) ) != 0 )
135 {
136 mbedtls_printf( " failed\n ! mbedtls_mpi_gen_prime returned %d\n\n", ret );
137 goto exit;
138 }
139
140 mbedtls_printf( " ok\n . Verifying that Q = (P-1)/2 is prime..." );
141 fflush( stdout );
142
143 if( ( ret = mbedtls_mpi_sub_int( &Q, &P, 1 ) ) != 0 )
144 {
145 mbedtls_printf( " failed\n ! mbedtls_mpi_sub_int returned %d\n\n", ret );
146 goto exit;
147 }
148
149 if( ( ret = mbedtls_mpi_div_int( &Q, NULL, &Q, 2 ) ) != 0 )
150 {
151 mbedtls_printf( " failed\n ! mbedtls_mpi_div_int returned %d\n\n", ret );
152 goto exit;
153 }
154
155 if( ( ret = mbedtls_mpi_is_prime_ext( &Q, 50, mbedtls_ctr_drbg_random, &ctr_drbg ) ) != 0 )
156 {
157 mbedtls_printf( " failed\n ! mbedtls_mpi_is_prime returned %d\n\n", ret );
158 goto exit;
159 }
160
161 mbedtls_printf( " ok\n . Exporting the value in dh_prime.txt..." );
162 fflush( stdout );
163
164 if( ( fout = fopen( "dh_prime.txt", "wb+" ) ) == NULL )
165 {
166 mbedtls_printf( " failed\n ! Could not create dh_prime.txt\n\n" );
167 goto exit;
168 }
169
170 if( ( ret = mbedtls_mpi_write_file( "P = ", &P, 16, fout ) != 0 ) ||
171 ( ret = mbedtls_mpi_write_file( "G = ", &G, 16, fout ) != 0 ) )
172 {
173 mbedtls_printf( " failed\n ! mbedtls_mpi_write_file returned %d\n\n", ret );
174 fclose( fout );
175 goto exit;
176 }
177
178 mbedtls_printf( " ok\n\n" );
179 fclose( fout );
180
181 exit_code = MBEDTLS_EXIT_SUCCESS;
182
183 exit:
184
185 mbedtls_mpi_free( &G ); mbedtls_mpi_free( &P ); mbedtls_mpi_free( &Q );
186 mbedtls_ctr_drbg_free( &ctr_drbg );
187 mbedtls_entropy_free( &entropy );
188
189 #if defined(_WIN32)
190 mbedtls_printf( " Press Enter to exit this program.\n" );
191 fflush( stdout ); getchar();
192 #endif
193
194 mbedtls_exit( exit_code );
195 }
196 #endif /* MBEDTLS_BIGNUM_C && MBEDTLS_ENTROPY_C && MBEDTLS_FS_IO &&
197 MBEDTLS_CTR_DRBG_C && MBEDTLS_GENPRIME */
198