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