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 < 2) {
75 usage:
76 mbedtls_printf(USAGE);
77 goto exit;
78 }
79
80 for (i = 1; i < argc; i++) {
81 p = argv[i];
82 if ((q = strchr(p, '=')) == NULL) {
83 goto usage;
84 }
85 *q++ = '\0';
86
87 if (strcmp(p, "bits") == 0) {
88 nbits = atoi(q);
89 if (nbits < 0 || nbits > MBEDTLS_MPI_MAX_BITS) {
90 goto usage;
91 }
92 } else {
93 goto usage;
94 }
95 }
96
97 if ((ret = mbedtls_mpi_read_string(&G, 10, GENERATOR)) != 0) {
98 mbedtls_printf(" failed\n ! mbedtls_mpi_read_string returned %d\n", ret);
99 goto exit;
100 }
101
102 mbedtls_printf(" ! Generating large primes may take minutes!\n");
103
104 mbedtls_printf("\n . Seeding the random number generator...");
105 fflush(stdout);
106
107 if ((ret = mbedtls_ctr_drbg_seed(&ctr_drbg, mbedtls_entropy_func, &entropy,
108 (const unsigned char *) pers,
109 strlen(pers))) != 0) {
110 mbedtls_printf(" failed\n ! mbedtls_ctr_drbg_seed returned %d\n", ret);
111 goto exit;
112 }
113
114 mbedtls_printf(" ok\n . Generating the modulus, please wait...");
115 fflush(stdout);
116
117 /*
118 * This can take a long time...
119 */
120 if ((ret = mbedtls_mpi_gen_prime(&P, nbits, 1,
121 mbedtls_ctr_drbg_random, &ctr_drbg)) != 0) {
122 mbedtls_printf(" failed\n ! mbedtls_mpi_gen_prime returned %d\n\n", ret);
123 goto exit;
124 }
125
126 mbedtls_printf(" ok\n . Verifying that Q = (P-1)/2 is prime...");
127 fflush(stdout);
128
129 if ((ret = mbedtls_mpi_sub_int(&Q, &P, 1)) != 0) {
130 mbedtls_printf(" failed\n ! mbedtls_mpi_sub_int returned %d\n\n", ret);
131 goto exit;
132 }
133
134 if ((ret = mbedtls_mpi_div_int(&Q, NULL, &Q, 2)) != 0) {
135 mbedtls_printf(" failed\n ! mbedtls_mpi_div_int returned %d\n\n", ret);
136 goto exit;
137 }
138
139 if ((ret = mbedtls_mpi_is_prime_ext(&Q, 50, mbedtls_ctr_drbg_random, &ctr_drbg)) != 0) {
140 mbedtls_printf(" failed\n ! mbedtls_mpi_is_prime returned %d\n\n", ret);
141 goto exit;
142 }
143
144 mbedtls_printf(" ok\n . Exporting the value in dh_prime.txt...");
145 fflush(stdout);
146
147 if ((fout = fopen("dh_prime.txt", "wb+")) == NULL) {
148 mbedtls_printf(" failed\n ! Could not create dh_prime.txt\n\n");
149 goto exit;
150 }
151
152 if (((ret = mbedtls_mpi_write_file("P = ", &P, 16, fout)) != 0) ||
153 ((ret = mbedtls_mpi_write_file("G = ", &G, 16, fout)) != 0)) {
154 mbedtls_printf(" failed\n ! mbedtls_mpi_write_file returned %d\n\n", ret);
155 fclose(fout);
156 goto exit;
157 }
158
159 mbedtls_printf(" ok\n\n");
160 fclose(fout);
161
162 exit_code = MBEDTLS_EXIT_SUCCESS;
163
164 exit:
165
166 mbedtls_mpi_free(&G); mbedtls_mpi_free(&P); mbedtls_mpi_free(&Q);
167 mbedtls_ctr_drbg_free(&ctr_drbg);
168 mbedtls_entropy_free(&entropy);
169
170 mbedtls_exit(exit_code);
171 }
172 #endif /* MBEDTLS_BIGNUM_C && MBEDTLS_ENTROPY_C && MBEDTLS_FS_IO &&
173 MBEDTLS_CTR_DRBG_C && MBEDTLS_GENPRIME */
174
