1/*-
2 * Copyright (c) 1991, 1993
3 *	Dave Safford.  All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 * 3. Neither the name of the University nor the names of its contributors
14 *    may be used to endorse or promote products derived from this software
15 *    without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 *
29 */
30
31#include <sys/cdefs.h>
32
33#ifdef notdef
34__FBSDID("$FreeBSD: src/contrib/telnet/libtelnet/pk.c,v 1.10 2002/08/22 06:19:07 nsayer Exp $");
35#else
36__RCSID("$NetBSD: pk.c,v 1.3 2005/02/19 22:47:51 christos Exp $");
37#endif
38
39/* public key routines */
40/* functions:
41	genkeys(char *public, char *secret)
42	common_key(char *secret, char *public, desData *deskey)
43	pk_encode(char *in, *out, DesData *deskey);
44	pk_decode(char *in, *out, DesData *deskey);
45      where
46	char public[HEXKEYBYTES + 1];
47	char secret[HEXKEYBYTES + 1];
48 */
49
50#include <sys/time.h>
51#include <des.h>
52#include <openssl/bn.h>
53#include <fcntl.h>
54#include <stdio.h>
55#include <stdlib.h>
56#include <string.h>
57
58#include "pk.h"
59
60static void adjust(char *, const char *);
61
62/*
63 * Choose top 128 bits of the common key to use as our idea key.
64 */
65static void
66extractideakey(BIGNUM *ck, IdeaData *ideakey)
67{
68	BIGNUM *a = BN_new();
69	BIGNUM *z = BN_new();
70	BIGNUM *base = BN_new();
71	BN_CTX *ctx = BN_CTX_new();
72	size_t i;
73	char *k;
74
75	(void)BN_zero(a);
76	(void)BN_zero(z);
77	(void)BN_set_word(base, 1 << 8);
78	BN_add(a, ck, z);
79
80	for (i = 0; i < ((KEYSIZE - 128) / 8); i++)
81		BN_div(a, z, a, base, ctx);
82
83	k = (char *)(void *)ideakey;
84	for (i = 0; i < 16; i++) {
85		BN_div(a, z, a, base, ctx);
86		*k++ = (char)BN_get_word(z);
87	}
88
89	BN_CTX_free(ctx);
90	BN_free(base);
91	BN_free(z);
92	BN_free(a);
93}
94
95/*
96 * Choose middle 64 bits of the common key to use as our des key, possibly
97 * overwriting the lower order bits by setting parity.
98 */
99static void
100extractdeskey(BIGNUM *ck, DesData *deskey)
101{
102	BIGNUM *a = BN_new();
103	BIGNUM *z = BN_new();
104	BIGNUM *base = BN_new();
105	BN_CTX *ctx = BN_CTX_new();
106	size_t i;
107	char *k;
108
109	(void)BN_zero(z);
110	(void)BN_zero(a);
111	(void)BN_set_word(base, 1 << 8);
112	BN_add(a, ck, z);
113
114	for (i = 0; i < ((KEYSIZE - 64) / 2) / 8; i++)
115		BN_div(a, z, a, base, ctx);
116
117	k = (char *)deskey;
118	for (i = 0; i < 8; i++) {
119		BN_div(a, z, a, base, ctx);
120		*k++ = (char)BN_get_word(z);
121	}
122
123	BN_CTX_free(ctx);
124	BN_free(base);
125	BN_free(z);
126	BN_free(a);
127}
128
129/*
130 * get common key from my secret key and his public key
131 */
132void
133common_key(char *xsecret, char *xpublic, IdeaData *ideakey, DesData *deskey)
134{
135	BIGNUM *public = BN_new();
136	BIGNUM *secret = BN_new();
137	BIGNUM *common = BN_new();
138	BIGNUM *modulus	 = BN_new();
139	BN_CTX *ctx = BN_CTX_new();
140
141	(void)BN_hex2bn(&modulus, HEXMODULUS);
142	(void)BN_hex2bn(&public, xpublic);
143	(void)BN_hex2bn(&secret, xsecret);
144	(void)BN_zero(common);
145
146	BN_mod_exp(common, public, secret, modulus, ctx);
147	extractdeskey(common, deskey);
148	extractideakey(common, ideakey);
149	des_set_odd_parity(deskey);
150
151	BN_CTX_free(ctx);
152	BN_free(common);
153	BN_free(secret);
154	BN_free(public);
155	BN_free(modulus);
156}
157
158/*
159 * Generate a seed
160 */
161static void
162getseed(char *seed, size_t seedsize)
163{
164	size_t i;
165
166	for (i = 0; i < seedsize; i++)
167		seed[i] = arc4random() & 0xff;
168}
169
170/*
171 * Generate a random public/secret key pair
172 */
173void
174genkeys(char *public, char *secret)
175{
176	size_t i;
177
178#	define BASEBITS (8 * sizeof(short) - 1)
179#	define BASE (1 << BASEBITS)
180
181	BIGNUM *pk = BN_new();
182	BIGNUM *sk = BN_new();
183	BIGNUM *tmp = BN_new();
184	BIGNUM *base = BN_new();
185	BIGNUM *root = BN_new();
186	BIGNUM *modulus = BN_new();
187	BN_CTX *ctx = BN_CTX_new();
188	short r;
189	unsigned short seed[KEYSIZE/BASEBITS + 1];
190	char *xkey;
191
192	(void)BN_zero(pk);
193	(void)BN_zero(sk);
194	(void)BN_set_word(base, BASE);
195	(void)BN_set_word(root, PROOT);
196	(void)BN_hex2bn(&modulus, HEXMODULUS);
197
198	getseed((char *)seed, sizeof(seed));
199	for (i = 0; i < KEYSIZE/BASEBITS + 1; i++) {
200		r = seed[i] % BASE;
201		(void)BN_set_word(tmp, r);
202		BN_mul(sk, tmp, sk, ctx);
203		BN_add(sk, tmp, sk);
204	}
205
206	(void)BN_zero(tmp);
207	BN_div(tmp, sk, sk, modulus, ctx);
208	BN_mod_exp(pk, root, sk, modulus, ctx);
209
210	xkey = BN_bn2hex(sk);
211	adjust(secret, xkey);
212	xkey = BN_bn2hex(pk);
213	adjust(public, xkey);
214
215	BN_CTX_free(ctx);
216	BN_free(sk);
217	BN_free(base);
218	BN_free(pk);
219	BN_free(tmp);
220	BN_free(root);
221	BN_free(modulus);
222}
223
224/*
225 * Adjust the input key so that it is 0-filled on the left
226 */
227static void
228adjust(char *keyout, const char *keyin)
229{
230	const char *p;
231	char *s;
232
233	for (p = keyin; *p; p++)
234		continue;
235	for (s = keyout + HEXKEYBYTES; p >= keyin; p--, s--)
236		*s = *p;
237	while (s >= keyout)
238		*s-- = '0';
239}
240
241static const char hextab[] = "0123456789ABCDEF";
242
243/* given a DES key, cbc encrypt and translate input to terminated hex */
244void
245pk_encode(const char *in, char *out, DesData *key)
246{
247	char buf[256];
248	DesData i;
249	des_key_schedule k;
250	size_t l, op, deslen;
251
252	(void)memset(&i, 0, sizeof(i));
253	(void)memset(buf, 0, sizeof(buf));
254	deslen = ((strlen(in) + 7) / 8) * 8;
255	des_key_sched(key, k);
256	des_cbc_encrypt(in, buf, deslen, k, &i, DES_ENCRYPT);
257	for (l = 0, op = 0; l < deslen; l++) {
258		out[op++] = hextab[(buf[l] & 0xf0) >> 4];
259		out[op++] = hextab[(buf[l] & 0x0f)];
260	}
261	out[op] = '\0';
262}
263
264/* given a DES key, translate input from hex and decrypt */
265void
266pk_decode(const char *in, char *out, DesData *key)
267{
268	char buf[256];
269	DesData i;
270	des_key_schedule k;
271	int n1, n2, op;
272	size_t l;
273	size_t len = strlen(in) / 2;
274
275	(void)memset(&i, 0, sizeof(i));
276	(void)memset(buf, 0, sizeof(buf));
277
278	for (l = 0, op = 0; l < len; l++, op += 2) {
279		if (in[op] > '9')
280			n1 = in[op] - 'A' + 10;
281		else
282			n1 = in[op] - '0';
283		if (in[op + 1] > '9')
284			n2 = in[op + 1] - 'A' + 10;
285		else
286			n2 = in[op + 1] - '0';
287		buf[l] = (char)(n1 * 16 + n2);
288	}
289	des_key_sched(key, k);
290	des_cbc_encrypt(buf, out, len, k, &i, DES_DECRYPT);
291	out[len] = '\0';
292}
293