1 /*
2 * Diffie-Hellman-Merkle key exchange (prime generation)
3 *
4 * Copyright The Mbed TLS Contributors
5 * SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
6 */
7
8 #if !defined(MBEDTLS_CONFIG_FILE)
9 #include "mbedtls/config.h"
10 #else
11 #include MBEDTLS_CONFIG_FILE
12 #endif
13
14 #include "mbedtls/platform.h"
15
16 #if !defined(MBEDTLS_BIGNUM_C) || !defined(MBEDTLS_ENTROPY_C) || \
17 !defined(MBEDTLS_FS_IO) || !defined(MBEDTLS_CTR_DRBG_C) || \
18 !defined(MBEDTLS_GENPRIME)
main(void)19 int main(void)
20 {
21 mbedtls_printf("MBEDTLS_BIGNUM_C and/or MBEDTLS_ENTROPY_C and/or "
22 "MBEDTLS_FS_IO and/or MBEDTLS_CTR_DRBG_C and/or "
23 "MBEDTLS_GENPRIME not defined.\n");
24 mbedtls_exit(0);
25 }
26 #else
27
28 #include "mbedtls/bignum.h"
29 #include "mbedtls/entropy.h"
30 #include "mbedtls/ctr_drbg.h"
31
32 #include <stdio.h>
33 #include <string.h>
34
35 #define USAGE \
36 "\n usage: dh_genprime param=<>...\n" \
37 "\n acceptable parameters:\n" \
38 " bits=%%d default: 2048\n"
39
40 #define DFL_BITS 2048
41
42 /*
43 * Note: G = 4 is always a quadratic residue mod P,
44 * so it is a generator of order Q (with P = 2*Q+1).
45 */
46 #define GENERATOR "4"
47
48
main(int argc,char ** argv)49 int main(int argc, char **argv)
50 {
51 int ret = 1;
52 int exit_code = MBEDTLS_EXIT_FAILURE;
53 mbedtls_mpi G, P, Q;
54 mbedtls_entropy_context entropy;
55 mbedtls_ctr_drbg_context ctr_drbg;
56 const char *pers = "dh_genprime";
57 FILE *fout;
58 int nbits = DFL_BITS;
59 int i;
60 char *p, *q;
61
62 mbedtls_mpi_init(&G); mbedtls_mpi_init(&P); mbedtls_mpi_init(&Q);
63 mbedtls_ctr_drbg_init(&ctr_drbg);
64 mbedtls_entropy_init(&entropy);
65
66 if (argc < 2) {
67 usage:
68 mbedtls_printf(USAGE);
69 goto exit;
70 }
71
72 for (i = 1; i < argc; i++) {
73 p = argv[i];
74 if ((q = strchr(p, '=')) == NULL) {
75 goto usage;
76 }
77 *q++ = '\0';
78
79 if (strcmp(p, "bits") == 0) {
80 nbits = atoi(q);
81 if (nbits < 0 || nbits > MBEDTLS_MPI_MAX_BITS) {
82 goto usage;
83 }
84 } else {
85 goto usage;
86 }
87 }
88
89 if ((ret = mbedtls_mpi_read_string(&G, 10, GENERATOR)) != 0) {
90 mbedtls_printf(" failed\n ! mbedtls_mpi_read_string returned %d\n", ret);
91 goto exit;
92 }
93
94 mbedtls_printf(" ! Generating large primes may take minutes!\n");
95
96 mbedtls_printf("\n . Seeding the random number generator...");
97 fflush(stdout);
98
99 if ((ret = mbedtls_ctr_drbg_seed(&ctr_drbg, mbedtls_entropy_func, &entropy,
100 (const unsigned char *) pers,
101 strlen(pers))) != 0) {
102 mbedtls_printf(" failed\n ! mbedtls_ctr_drbg_seed returned %d\n", ret);
103 goto exit;
104 }
105
106 mbedtls_printf(" ok\n . Generating the modulus, please wait...");
107 fflush(stdout);
108
109 /*
110 * This can take a long time...
111 */
112 if ((ret = mbedtls_mpi_gen_prime(&P, nbits, 1,
113 mbedtls_ctr_drbg_random, &ctr_drbg)) != 0) {
114 mbedtls_printf(" failed\n ! mbedtls_mpi_gen_prime returned %d\n\n", ret);
115 goto exit;
116 }
117
118 mbedtls_printf(" ok\n . Verifying that Q = (P-1)/2 is prime...");
119 fflush(stdout);
120
121 if ((ret = mbedtls_mpi_sub_int(&Q, &P, 1)) != 0) {
122 mbedtls_printf(" failed\n ! mbedtls_mpi_sub_int returned %d\n\n", ret);
123 goto exit;
124 }
125
126 if ((ret = mbedtls_mpi_div_int(&Q, NULL, &Q, 2)) != 0) {
127 mbedtls_printf(" failed\n ! mbedtls_mpi_div_int returned %d\n\n", ret);
128 goto exit;
129 }
130
131 if ((ret = mbedtls_mpi_is_prime_ext(&Q, 50, mbedtls_ctr_drbg_random, &ctr_drbg)) != 0) {
132 mbedtls_printf(" failed\n ! mbedtls_mpi_is_prime returned %d\n\n", ret);
133 goto exit;
134 }
135
136 mbedtls_printf(" ok\n . Exporting the value in dh_prime.txt...");
137 fflush(stdout);
138
139 if ((fout = fopen("dh_prime.txt", "wb+")) == NULL) {
140 mbedtls_printf(" failed\n ! Could not create dh_prime.txt\n\n");
141 goto exit;
142 }
143
144 if (((ret = mbedtls_mpi_write_file("P = ", &P, 16, fout)) != 0) ||
145 ((ret = mbedtls_mpi_write_file("G = ", &G, 16, fout)) != 0)) {
146 mbedtls_printf(" failed\n ! mbedtls_mpi_write_file returned %d\n\n", ret);
147 fclose(fout);
148 goto exit;
149 }
150
151 mbedtls_printf(" ok\n\n");
152 fclose(fout);
153
154 exit_code = MBEDTLS_EXIT_SUCCESS;
155
156 exit:
157
158 mbedtls_mpi_free(&G); mbedtls_mpi_free(&P); mbedtls_mpi_free(&Q);
159 mbedtls_ctr_drbg_free(&ctr_drbg);
160 mbedtls_entropy_free(&entropy);
161
162 #if defined(_WIN32)
163 mbedtls_printf(" Press Enter to exit this program.\n");
164 fflush(stdout); getchar();
165 #endif
166
167 mbedtls_exit(exit_code);
168 }
169 #endif /* MBEDTLS_BIGNUM_C && MBEDTLS_ENTROPY_C && MBEDTLS_FS_IO &&
170 MBEDTLS_CTR_DRBG_C && MBEDTLS_GENPRIME */
171