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