161 lines
4.5 KiB
C
161 lines
4.5 KiB
C
/*
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* Diffie-Hellman-Merkle key exchange (prime generation)
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*
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* Copyright The Mbed TLS Contributors
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* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
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*/
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#include "mbedtls/build_info.h"
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#include "mbedtls/platform.h"
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#if !defined(MBEDTLS_BIGNUM_C) || !defined(MBEDTLS_ENTROPY_C) || \
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!defined(MBEDTLS_FS_IO) || !defined(MBEDTLS_CTR_DRBG_C) || \
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!defined(MBEDTLS_GENPRIME)
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int main(void)
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{
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mbedtls_printf("MBEDTLS_BIGNUM_C and/or MBEDTLS_ENTROPY_C and/or "
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"MBEDTLS_FS_IO and/or MBEDTLS_CTR_DRBG_C and/or "
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"MBEDTLS_GENPRIME not defined.\n");
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mbedtls_exit(0);
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}
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#else
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#include "mbedtls/bignum.h"
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#include "mbedtls/entropy.h"
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#include "mbedtls/ctr_drbg.h"
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#include <stdio.h>
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#include <string.h>
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#define USAGE \
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"\n usage: dh_genprime param=<>...\n" \
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"\n acceptable parameters:\n" \
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" bits=%%d default: 2048\n"
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#define DFL_BITS 2048
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/*
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* Note: G = 4 is always a quadratic residue mod P,
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* so it is a generator of order Q (with P = 2*Q+1).
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*/
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#define GENERATOR "4"
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int main(int argc, char **argv)
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{
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int ret = 1;
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int exit_code = MBEDTLS_EXIT_FAILURE;
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mbedtls_mpi G, P, Q;
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mbedtls_entropy_context entropy;
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mbedtls_ctr_drbg_context ctr_drbg;
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const char *pers = "dh_genprime";
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FILE *fout;
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int nbits = DFL_BITS;
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int i;
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char *p, *q;
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mbedtls_mpi_init(&G); mbedtls_mpi_init(&P); mbedtls_mpi_init(&Q);
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mbedtls_ctr_drbg_init(&ctr_drbg);
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mbedtls_entropy_init(&entropy);
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if (argc < 2) {
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usage:
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mbedtls_printf(USAGE);
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goto exit;
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}
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for (i = 1; i < argc; i++) {
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p = argv[i];
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if ((q = strchr(p, '=')) == NULL) {
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goto usage;
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}
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*q++ = '\0';
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if (strcmp(p, "bits") == 0) {
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nbits = atoi(q);
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if (nbits < 0 || nbits > MBEDTLS_MPI_MAX_BITS) {
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goto usage;
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}
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} else {
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goto usage;
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}
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}
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if ((ret = mbedtls_mpi_read_string(&G, 10, GENERATOR)) != 0) {
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mbedtls_printf(" failed\n ! mbedtls_mpi_read_string returned %d\n", ret);
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goto exit;
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}
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mbedtls_printf(" ! Generating large primes may take minutes!\n");
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mbedtls_printf("\n . Seeding the random number generator...");
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fflush(stdout);
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if ((ret = mbedtls_ctr_drbg_seed(&ctr_drbg, mbedtls_entropy_func, &entropy,
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(const unsigned char *) pers,
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strlen(pers))) != 0) {
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mbedtls_printf(" failed\n ! mbedtls_ctr_drbg_seed returned %d\n", ret);
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goto exit;
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}
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mbedtls_printf(" ok\n . Generating the modulus, please wait...");
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fflush(stdout);
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/*
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* This can take a long time...
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*/
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if ((ret = mbedtls_mpi_gen_prime(&P, nbits, 1,
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mbedtls_ctr_drbg_random, &ctr_drbg)) != 0) {
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mbedtls_printf(" failed\n ! mbedtls_mpi_gen_prime returned %d\n\n", ret);
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goto exit;
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}
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mbedtls_printf(" ok\n . Verifying that Q = (P-1)/2 is prime...");
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fflush(stdout);
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if ((ret = mbedtls_mpi_sub_int(&Q, &P, 1)) != 0) {
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mbedtls_printf(" failed\n ! mbedtls_mpi_sub_int returned %d\n\n", ret);
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goto exit;
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}
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if ((ret = mbedtls_mpi_div_int(&Q, NULL, &Q, 2)) != 0) {
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mbedtls_printf(" failed\n ! mbedtls_mpi_div_int returned %d\n\n", ret);
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goto exit;
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}
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if ((ret = mbedtls_mpi_is_prime_ext(&Q, 50, mbedtls_ctr_drbg_random, &ctr_drbg)) != 0) {
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mbedtls_printf(" failed\n ! mbedtls_mpi_is_prime returned %d\n\n", ret);
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goto exit;
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}
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mbedtls_printf(" ok\n . Exporting the value in dh_prime.txt...");
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fflush(stdout);
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if ((fout = fopen("dh_prime.txt", "wb+")) == NULL) {
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mbedtls_printf(" failed\n ! Could not create dh_prime.txt\n\n");
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goto exit;
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}
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if (((ret = mbedtls_mpi_write_file("P = ", &P, 16, fout)) != 0) ||
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((ret = mbedtls_mpi_write_file("G = ", &G, 16, fout)) != 0)) {
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mbedtls_printf(" failed\n ! mbedtls_mpi_write_file returned %d\n\n", ret);
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fclose(fout);
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goto exit;
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}
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mbedtls_printf(" ok\n\n");
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fclose(fout);
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exit_code = MBEDTLS_EXIT_SUCCESS;
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exit:
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mbedtls_mpi_free(&G); mbedtls_mpi_free(&P); mbedtls_mpi_free(&Q);
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mbedtls_ctr_drbg_free(&ctr_drbg);
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mbedtls_entropy_free(&entropy);
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mbedtls_exit(exit_code);
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}
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#endif /* MBEDTLS_BIGNUM_C && MBEDTLS_ENTROPY_C && MBEDTLS_FS_IO &&
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MBEDTLS_CTR_DRBG_C && MBEDTLS_GENPRIME */
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