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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 */
#ifdef DROPBEAR_DSS
static void getq(dropbear_dss_key *key);
static void getp(dropbear_dss_key *key, unsigned int size);
static void getg(dropbear_dss_key *key);
static void getx(dropbear_dss_key *key);
static void gety(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(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(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(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(dropbear_dss_key *key) {
gen_random_mpint(key->q, key->x);
}
static void gety(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 */
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