view gendss.c @ 1902:4a6725ac957c

Revert "Don't include sk keys at all in KEX list" This reverts git commit f972813ecdc7bb981d25b5a63638bd158f1c8e72. The sk algorithms need to remain in the sigalgs list so that they are included in the server-sig-algs ext-info message sent by the server. RFC8308 for server-sig-algs requires that all algorithms are listed (though OpenSSH client 8.4p1 tested doesn't require that)
author Matt Johnston <matt@ucc.asn.au>
date Thu, 24 Mar 2022 13:42:08 +0800
parents f52919ffd3b1
children
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/*
 * Dropbear - a SSH2 server
 * 
 * Copyright (c) 2002,2003 Matt Johnston
 * All rights reserved.
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE. */

#include "includes.h"
#include "dbutil.h"
#include "signkey.h"
#include "bignum.h"
#include "dbrandom.h"
#include "buffer.h"
#include "gendss.h"
#include "dss.h"

#define QSIZE 20 /* 160 bit */

/* This is just a test */

#if DROPBEAR_DSS

static void getq(const dropbear_dss_key *key);
static void getp(const dropbear_dss_key *key, unsigned int size);
static void getg(const dropbear_dss_key *key);
static void getx(const dropbear_dss_key *key);
static void gety(const dropbear_dss_key *key);

dropbear_dss_key * gen_dss_priv_key(unsigned int size) {

	dropbear_dss_key *key;

	if (size != 1024) {
		dropbear_exit("DSS keys have a fixed size of 1024 bits");
	}

	key = m_malloc(sizeof(*key));

	m_mp_alloc_init_multi(&key->p, &key->q, &key->g, &key->y, &key->x, NULL);
	
	getq(key);
	getp(key, size/8);
	getg(key);
	getx(key);
	gety(key);

	return key;
	
}

static void getq(const dropbear_dss_key *key) {

	unsigned char buf[QSIZE];
	int trials;

	/* 160 bit prime */
	genrandom(buf, QSIZE);
	buf[0] |= 0x80; /* top bit high */
	buf[QSIZE-1] |= 0x01; /* bottom bit high */

	bytes_to_mp(key->q, buf, QSIZE);

	/* ask FIPS 186.4 how many Rabin-Miller trials are required */
	trials = mp_prime_rabin_miller_trials(mp_count_bits(key->q));
	if (mp_prime_next_prime(key->q, trials, 0) != MP_OKAY) {
		fprintf(stderr, "DSS key generation failed\n");
		exit(1);
	}
}

static void getp(const dropbear_dss_key *key, unsigned int size) {

	DEF_MP_INT(tempX);
	DEF_MP_INT(tempC);
	DEF_MP_INT(tempP);
	DEF_MP_INT(temp2q);
	int result, trials;
	unsigned char *buf;

	m_mp_init_multi(&tempX, &tempC, &tempP, &temp2q, NULL);


	/* 2*q */
	if (mp_mul_d(key->q, 2, &temp2q) != MP_OKAY) {
		fprintf(stderr, "DSS key generation failed\n");
		exit(1);
	}
	
	buf = (unsigned char*)m_malloc(size);

	result = 0;
	do {
		
		genrandom(buf, size);
		buf[0] |= 0x80; /* set the top bit high */

		/* X is a random mp_int */
		bytes_to_mp(&tempX, buf, size);

		/* C = X mod 2q */
		if (mp_mod(&tempX, &temp2q, &tempC) != MP_OKAY) {
			fprintf(stderr, "DSS key generation failed\n");
			exit(1);
		}

		/* P = X - (C - 1) = X - C + 1*/
		if (mp_sub(&tempX, &tempC, &tempP) != MP_OKAY) {
			fprintf(stderr, "DSS key generation failed\n");
			exit(1);
		}
		
		if (mp_add_d(&tempP, 1, key->p) != MP_OKAY) {
			fprintf(stderr, "DSS key generation failed\n");
			exit(1);
		}

		/* ask FIPS 186.4 how many Rabin-Miller trials are required */
		trials = mp_prime_rabin_miller_trials(mp_count_bits(key->p));
		/* result == 1  =>  p is prime */
		if (mp_prime_is_prime(key->p, trials, &result) != MP_OKAY) {
			fprintf(stderr, "DSS key generation failed\n");
			exit(1);
		}
	} while (!result);

	mp_clear_multi(&tempX, &tempC, &tempP, &temp2q, NULL);
	m_burn(buf, size);
	m_free(buf);
}

static void getg(const dropbear_dss_key * key) {

	DEF_MP_INT(div);
	DEF_MP_INT(h);
	DEF_MP_INT(val);

	m_mp_init_multi(&div, &h, &val, NULL);

	/* get div=(p-1)/q */
	if (mp_sub_d(key->p, 1, &val) != MP_OKAY) {
		fprintf(stderr, "DSS key generation failed\n");
		exit(1);
	}
	if (mp_div(&val, key->q, &div, NULL) != MP_OKAY) {
		fprintf(stderr, "DSS key generation failed\n");
		exit(1);
	}

	/* initialise h=1 */
	mp_set(&h, 1);
	do {
		/* now keep going with g=h^div mod p, until g > 1 */
		if (mp_exptmod(&h, &div, key->p, key->g) != MP_OKAY) {
			fprintf(stderr, "DSS key generation failed\n");
			exit(1);
		}

		if (mp_add_d(&h, 1, &h) != MP_OKAY) {
			fprintf(stderr, "DSS key generation failed\n");
			exit(1);
		}
	
	} while (mp_cmp_d(key->g, 1) != MP_GT);

	mp_clear_multi(&div, &h, &val, NULL);
}

static void getx(const dropbear_dss_key *key) {

	gen_random_mpint(key->q, key->x);
}

static void gety(const dropbear_dss_key *key) {

	if (mp_exptmod(key->g, key->x, key->p, key->y) != MP_OKAY) {
		fprintf(stderr, "DSS key generation failed\n");
		exit(1);
	}
}

#endif /* DROPBEAR_DSS */