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 * $FreeBSD: src/crypto/telnet/libtelnet/pk.c,v 1.2.2.4 2002/08/24 07:28:35 nsayer Exp $
31 */
32
33 /* public key routines */
34 /* functions:
35 genkeys(char *public, char *secret)
36 common_key(char *secret, char *public, desData *deskey)
37 pk_encode(char *in, *out, DesData *deskey);
38 pk_decode(char *in, *out, DesData *deskey);
39 where
40 char public[HEXKEYBYTES + 1];
41 char secret[HEXKEYBYTES + 1];
42 */
43
44 #include <sys/param.h>
45 #include <sys/time.h>
46 #include <err.h>
47 #include <fcntl.h>
48 #include <stdio.h>
49 #include <stdlib.h>
50 #include <string.h>
51
52 #include <openssl/bn.h>
53 #include <openssl/crypto.h>
54 #include <openssl/des.h>
55 #include <openssl/err.h>
56
57 #include "pk.h"
58
59 static void adjust(char keyout[HEXKEYBYTES+1], char *keyin);
60
61 /*
62 * Choose top 128 bits of the common key to use as our idea key.
63 */
64 static void
extractideakey(BIGNUM * ck,IdeaData * ideakey)65 extractideakey(BIGNUM *ck, IdeaData *ideakey)
66 {
67 BIGNUM *a, *z;
68 int i;
69 BN_ULONG r, base = (1 << 8);
70 char *k;
71
72 if ((z = BN_new()) == NULL)
73 errx(1, "could not create BIGNUM");
74 BN_zero(z);
75 if ((a = BN_new()) == NULL)
76 errx(1, "could not create BIGNUM");
77 BN_zero(a);
78 BN_add(a, ck, z);
79 for (i = 0; i < ((KEYSIZE - 128) / 8); i++) {
80 r = BN_div_word(a, base);
81 }
82 k = (char *)ideakey;
83 for (i = 0; i < 16; i++) {
84 r = BN_div_word(a, base);
85 *k++ = r;
86 }
87 BN_free(z);
88 BN_free(a);
89 }
90
91 /*
92 * Choose middle 64 bits of the common key to use as our des key, possibly
93 * overwriting the lower order bits by setting parity.
94 */
95 static void
extractdeskey(BIGNUM * ck,DesData * deskey)96 extractdeskey(BIGNUM *ck, DesData *deskey)
97 {
98 BIGNUM *a, *z;
99 int i;
100 BN_ULONG r, base = (1 << 8);
101 char *k;
102
103 if ((z = BN_new()) == NULL)
104 errx(1, "could not create BIGNUM");
105 BN_zero(z);
106 if ((a = BN_new()) == NULL)
107 errx(1, "could not create BIGNUM");
108 BN_zero(a);
109 BN_add(a, ck, z);
110 for (i = 0; i < ((KEYSIZE - 64) / 2) / 8; i++) {
111 r = BN_div_word(a, base);
112 }
113 k = (char *)deskey;
114 for (i = 0; i < 8; i++) {
115 r = BN_div_word(a, base);
116 *k++ = r;
117 }
118 BN_free(z);
119 BN_free(a);
120 }
121
122 /*
123 * get common key from my secret key and his public key
124 */
125 void
common_key(char * xsecret,char * xpublic,IdeaData * ideakey,DesData * deskey)126 common_key(char *xsecret, char *xpublic, IdeaData *ideakey, DesData *deskey)
127 {
128 BIGNUM *public, *secret, *common, *modulus;
129 BN_CTX *ctx;
130
131 if ((ctx = BN_CTX_new()) == NULL)
132 errx(1, "could not create BN_CTX");
133 modulus = NULL;
134 if (BN_hex2bn(&modulus, HEXMODULUS) == 0)
135 errx(1, "could not convert modulus");
136 public = NULL;
137 if (BN_hex2bn(&public, xpublic) == 0)
138 errx(1, "could not convert public");
139 secret = NULL;
140 if (BN_hex2bn(&secret, xsecret) == 0)
141 errx(1, "could not convert secret");
142
143 if ((common = BN_new()) == NULL)
144 errx(1, "could not create BIGNUM");
145 BN_zero(common);
146 BN_mod_exp(common, public, secret, modulus, ctx);
147 extractdeskey(common, deskey);
148 extractideakey(common, ideakey);
149 DES_set_odd_parity(deskey);
150 BN_free(common);
151 BN_free(secret);
152 BN_free(public);
153 BN_free(modulus);
154 BN_CTX_free(ctx);
155 }
156
157 /*
158 * Generate a seed
159 */
160 static void
getseed(char * seed,int seedsize)161 getseed(char *seed, int seedsize)
162 {
163 int i;
164
165 for (i = 0; i < seedsize; i++) {
166 seed[i] = arc4random() & 0xff;
167 }
168 }
169
170 static BIGNUM *
itobn(long i)171 itobn(long i)
172 {
173 BIGNUM *n = NULL;
174
175 if ((n = BN_new()) == NULL)
176 errx(1, "could not create BIGNUM: %s",
177 ERR_error_string(ERR_get_error(), 0));
178 BN_init(n);
179 if (i > 0)
180 BN_add_word(n, (u_long)i);
181 else
182 BN_sub_word(n, (u_long)(-i));
183 return(n);
184 }
185
186 /*
187 * Generate a random public/secret key pair
188 */
189 void
genkeys(char * public,char * secret)190 genkeys(char *public, char *secret)
191 {
192 #define BASEBITS (8*sizeof (short) - 1)
193 #define BASE (short)(1 << BASEBITS)
194
195 unsigned int i;
196 short r;
197 unsigned short seed[KEYSIZE/BASEBITS + 1];
198 char *xkey;
199
200 BN_CTX *ctx;
201 BIGNUM *pk, *sk, *tmp, *base, *root, *modulus;
202
203 pk = itobn(0);
204 sk = itobn(0);
205 tmp = itobn(0);
206 base = itobn(BASE);
207 root = itobn(PROOT);
208 modulus = NULL;
209 if (BN_hex2bn(&modulus, HEXMODULUS) == 0)
210 errx(1, "could not convert modulus to BIGNUM: %s",
211 ERR_error_string(ERR_get_error(), 0));
212
213 if ((ctx = BN_CTX_new()) == NULL)
214 errx(1, "could not create BN_CTX: %s",
215 ERR_error_string(ERR_get_error(), 0));
216
217 getseed((char *)seed, sizeof (seed));
218 for (i = 0; i < KEYSIZE/BASEBITS + 1; i++) {
219 r = seed[i] % BASE;
220 BN_zero(tmp);
221 BN_add_word(tmp, r);
222 BN_mul(sk, base, sk, ctx);
223 BN_add(sk, tmp, sk);
224 }
225 BN_zero(tmp);
226 BN_div(tmp, sk, sk, modulus, ctx);
227 BN_mod_exp(pk, root, sk, modulus, ctx);
228
229 if ((xkey = BN_bn2hex(sk)) == NULL)
230 errx(1, "could convert sk to hex: %s",
231 ERR_error_string(ERR_get_error(), 0));
232 adjust(secret, xkey);
233 OPENSSL_free(xkey);
234
235 if ((xkey = BN_bn2hex(pk)) == NULL)
236 errx(1, "could convert pk to hex: %s",
237 ERR_error_string(ERR_get_error(), 0));
238 adjust(public, xkey);
239 OPENSSL_free(xkey);
240
241 BN_free(base);
242 BN_free(modulus);
243 BN_free(pk);
244 BN_free(sk);
245 BN_free(root);
246 BN_free(tmp);
247 }
248
249 /*
250 * Adjust the input key so that it is 0-filled on the left
251 */
252 static void
adjust(char keyout[HEXKEYBYTES+1],char * keyin)253 adjust(char keyout[HEXKEYBYTES+1], char *keyin)
254 {
255 char *p;
256 char *s;
257
258 for (p = keyin; *p; p++)
259 ;
260 for (s = keyout + HEXKEYBYTES; p >= keyin; p--, s--) {
261 *s = *p;
262 }
263 while (s >= keyout) {
264 *s-- = '0';
265 }
266 }
267
268 static char hextab[17] = "0123456789ABCDEF";
269
270 /* given a DES key, cbc encrypt and translate input to terminated hex */
271 void
pk_encode(char * in,char * out,DesData * key)272 pk_encode(char *in, char *out, DesData *key)
273 {
274 char buf[256];
275 DesData i;
276 DES_key_schedule k;
277 int l,op,deslen;
278
279 memset(&i,0,sizeof(i));
280 memset(buf,0,sizeof(buf));
281 deslen = rounddown(strlen(in) + 7, 8);
282 DES_key_sched(key, &k);
283 DES_cbc_encrypt(in,buf,deslen, &k,&i,DES_ENCRYPT);
284 for (l=0,op=0;l<deslen;l++) {
285 out[op++] = hextab[(buf[l] & 0xf0) >> 4];
286 out[op++] = hextab[(buf[l] & 0x0f)];
287 }
288 out[op] = '\0';
289 }
290
291 /* given a DES key, translate input from hex and decrypt */
292 void
pk_decode(char * in,char * out,DesData * key)293 pk_decode(char *in, char *out, DesData *key)
294 {
295 char buf[256];
296 DesData i;
297 DES_key_schedule k;
298 int n1,n2,op;
299 size_t l;
300
301 memset(&i,0,sizeof(i));
302 memset(buf,0,sizeof(buf));
303 for (l=0,op=0;l<strlen(in)/2;l++,op+=2) {
304 if (in[op] > '9')
305 n1 = in[op] - 'A' + 10;
306 else
307 n1 = in[op] - '0';
308 if (in[op+1] > '9')
309 n2 = in[op+1] - 'A' + 10;
310 else
311 n2 = in[op+1] - '0';
312 buf[l] = n1*16 +n2;
313 }
314 DES_key_sched(key, &k);
315 DES_cbc_encrypt(buf,out,strlen(in)/2, &k,&i,DES_DECRYPT);
316 out[strlen(in)/2] = '\0';
317 }
318