1/*
2 * Dropbear - a SSH2 server
3 *
4 * Copyright (c) 2002,2003 Matt Johnston
5 * All rights reserved.
6 *
7 * Permission is hereby granted, free of charge, to any person obtaining a copy
8 * of this software and associated documentation files (the "Software"), to deal
9 * in the Software without restriction, including without limitation the rights
10 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
11 * copies of the Software, and to permit persons to whom the Software is
12 * furnished to do so, subject to the following conditions:
13 *
14 * The above copyright notice and this permission notice shall be included in
15 * all copies or substantial portions of the Software.
16 *
17 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
18 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
19 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
20 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
21 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
22 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
23 * SOFTWARE. */
24
25#include "includes.h"
26#include "dbutil.h"
27#include "signkey.h"
28#include "bignum.h"
29#include "random.h"
30#include "buffer.h"
31#include "gendss.h"
32#include "dss.h"
33
34#define QSIZE 20 /* 160 bit */
35
36/* This is just a test */
37
38#ifdef DROPBEAR_DSS
39
40static void getq(dss_key *key);
41static void getp(dss_key *key, unsigned int size);
42static void getg(dss_key *key);
43static void getx(dss_key *key);
44static void gety(dss_key *key);
45
46dss_key * gen_dss_priv_key(unsigned int size) {
47
48	dss_key *key;
49
50	key = (dss_key*)m_malloc(sizeof(dss_key));
51
52	key->p = (mp_int*)m_malloc(sizeof(mp_int));
53	key->q = (mp_int*)m_malloc(sizeof(mp_int));
54	key->g = (mp_int*)m_malloc(sizeof(mp_int));
55	key->y = (mp_int*)m_malloc(sizeof(mp_int));
56	key->x = (mp_int*)m_malloc(sizeof(mp_int));
57	m_mp_init_multi(key->p, key->q, key->g, key->y, key->x, NULL);
58
59	seedrandom();
60
61	getq(key);
62	getp(key, size);
63	getg(key);
64	getx(key);
65	gety(key);
66
67	return key;
68
69}
70
71static void getq(dss_key *key) {
72
73	char buf[QSIZE];
74
75	/* 160 bit prime */
76	genrandom(buf, QSIZE);
77	buf[0] |= 0x80; /* top bit high */
78	buf[QSIZE-1] |= 0x01; /* bottom bit high */
79
80	bytes_to_mp(key->q, buf, QSIZE);
81
82	/* 18 rounds are required according to HAC */
83	if (mp_prime_next_prime(key->q, 18, 0) != MP_OKAY) {
84		fprintf(stderr, "dss key generation failed\n");
85		exit(1);
86	}
87}
88
89static void getp(dss_key *key, unsigned int size) {
90
91	DEF_MP_INT(tempX);
92	DEF_MP_INT(tempC);
93	DEF_MP_INT(tempP);
94	DEF_MP_INT(temp2q);
95	int result;
96	unsigned char *buf;
97
98	m_mp_init_multi(&tempX, &tempC, &tempP, &temp2q, NULL);
99
100
101	/* 2*q */
102	if (mp_mul_d(key->q, 2, &temp2q) != MP_OKAY) {
103		fprintf(stderr, "dss key generation failed\n");
104		exit(1);
105	}
106
107	buf = (unsigned char*)m_malloc(size);
108
109	result = 0;
110	do {
111
112		genrandom(buf, size);
113		buf[0] |= 0x80; /* set the top bit high */
114
115		/* X is a random mp_int */
116		bytes_to_mp(&tempX, buf, size);
117
118		/* C = X mod 2q */
119		if (mp_mod(&tempX, &temp2q, &tempC) != MP_OKAY) {
120			fprintf(stderr, "dss key generation failed\n");
121			exit(1);
122		}
123
124		/* P = X - (C - 1) = X - C + 1*/
125		if (mp_sub(&tempX, &tempC, &tempP) != MP_OKAY) {
126			fprintf(stderr, "dss key generation failed\n");
127			exit(1);
128		}
129
130		if (mp_add_d(&tempP, 1, key->p) != MP_OKAY) {
131			fprintf(stderr, "dss key generation failed\n");
132			exit(1);
133		}
134
135		/* now check for prime, 5 rounds is enough according to HAC */
136		/* result == 1  =>  p is prime */
137		if (mp_prime_is_prime(key->p, 5, &result) != MP_OKAY) {
138			fprintf(stderr, "dss key generation failed\n");
139			exit(1);
140		}
141	} while (!result);
142
143	mp_clear_multi(&tempX, &tempC, &tempP, &temp2q, NULL);
144	m_burn(buf, size);
145	m_free(buf);
146}
147
148static void getg(dss_key * key) {
149
150	DEF_MP_INT(div);
151	DEF_MP_INT(h);
152	DEF_MP_INT(val);
153
154	m_mp_init_multi(&div, &h, &val, NULL);
155
156	/* get div=(p-1)/q */
157	if (mp_sub_d(key->p, 1, &val) != MP_OKAY) {
158		fprintf(stderr, "dss key generation failed\n");
159		exit(1);
160	}
161	if (mp_div(&val, key->q, &div, NULL) != MP_OKAY) {
162		fprintf(stderr, "dss key generation failed\n");
163		exit(1);
164	}
165
166	/* initialise h=1 */
167	mp_set(&h, 1);
168	do {
169		/* now keep going with g=h^div mod p, until g > 1 */
170		if (mp_exptmod(&h, &div, key->p, key->g) != MP_OKAY) {
171			fprintf(stderr, "dss key generation failed\n");
172			exit(1);
173		}
174
175		if (mp_add_d(&h, 1, &h) != MP_OKAY) {
176			fprintf(stderr, "dss key generation failed\n");
177			exit(1);
178		}
179
180	} while (mp_cmp_d(key->g, 1) != MP_GT);
181
182	mp_clear_multi(&div, &h, &val, NULL);
183}
184
185static void getx(dss_key *key) {
186
187	gen_random_mpint(key->q, key->x);
188}
189
190static void gety(dss_key *key) {
191
192	if (mp_exptmod(key->g, key->x, key->p, key->y) != MP_OKAY) {
193		fprintf(stderr, "dss key generation failed\n");
194		exit(1);
195	}
196}
197
198#endif /* DROPBEAR_DSS */
199