view gendss.c @ 1653:76189c9ffea2

External Public-Key Authentication API (#72) * Implemented dynamic loading of an external plug-in shared library to delegate public key authentication * Moved conditional compilation of the plugin infrastructure into the configure.ac script to be able to add -ldl to dropbear build only when the flag is enabled * Added tags file to the ignore list * Updated API to have the constructor to return function pointers in the pliugin instance. Added support for passing user name to the checkpubkey function. Added options to the session returned by the plugin and have dropbear to parse and process them * Added -rdynamic to the linker flags when EPKA is enabled * Changed the API to pass a previously created session to the checkPubKey function (created during preauth) * Added documentation to the API * Added parameter addrstring to plugin creation function * Modified the API to retrieve the auth options. Instead of having them as field of the EPKASession struct, they are stored internally (plugin-dependent) in the plugin/session and retrieved through a pointer to a function (in the session) * Changed option string to be a simple char * instead of unsigned char *
author fabriziobertocci <fabriziobertocci@gmail.com>
date Wed, 15 May 2019 09:43:57 -0400
parents 06d52bcb8094
children f52919ffd3b1
line wrap: on
line source

/*
 * 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];

	/* 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);

	/* 18 rounds are required according to HAC */
	if (mp_prime_next_prime(key->q, 18, 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;
	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);
		}

		/* now check for prime, 5 rounds is enough according to HAC */
		/* result == 1  =>  p is prime */
		if (mp_prime_is_prime(key->p, 5, &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 */