5 * This file is Free Software. It was originally written for secnet.
7 * Copyright 1995-2003 Stephen Early
8 * Copyright 2002-2014 Ian Jackson
10 * You may redistribute secnet as a whole and/or modify it under the
11 * terms of the GNU General Public License as published by the Free
12 * Software Foundation; either version 3, or (at your option) any
15 * You may redistribute this file and/or modify it under the terms of
16 * the GNU General Public License as published by the Free Software
17 * Foundation; either version 2, or (at your option) any later
20 * This software is distributed in the hope that it will be useful,
21 * but WITHOUT ANY WARRANTY; without even the implied warranty of
22 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
23 * GNU General Public License for more details.
25 * You should have received a copy of the GNU General Public License
26 * along with this software; if not, see
27 * https://www.gnu.org/licenses/gpl.html.
41 MP_INT p,g; /* prime modulus and generator */
44 static string_t dh_makepublic(void *sst, uint8_t *secret, int32_t secretlen)
48 MP_INT a, b; /* a is secret key, b is public key */
53 read_mpbin(&a, secret, secretlen);
55 mpz_powm_sec(&b, &st->g, &a, &st->p);
64 static void write_mpbin_anomalous(MP_INT *a, uint8_t *buffer,
66 /* If the BN is smaller than buflen, pads it *at the wrong end* */
68 char *hb = write_mpstring(a);
70 hex_decode(buffer, buflen, &len, hb, True);
72 memset(buffer+len,0,buflen-len);
76 static dh_makeshared_fn dh_makeshared;
77 static void dh_makeshared(void *sst, uint8_t *secret, int32_t secretlen,
78 cstring_t rempublic, uint8_t *sharedsecret,
88 read_mpbin(&a, secret, secretlen);
89 mpz_set_str(&b, rempublic, 16);
91 mpz_powm_sec(&c, &b, &a, &st->p);
93 write_mpbin_anomalous(&c,sharedsecret,buflen);
100 static list_t *dh_apply(closure_t *self, struct cloc loc, dict_t *context,
108 st->cl.description="dh";
111 st->cl.interface=&st->ops;
113 st->ops.makepublic=dh_makepublic;
114 st->ops.makeshared=dh_makeshared;
116 /* We have two string arguments: the first is the modulus, and the
117 second is the generator. Both are in hex. */
120 if (i->type!=t_string) {
121 cfgfatal(i->loc,"diffie-hellman","first argument must be a "
125 if (mpz_init_set_str(&st->p,p,16)!=0) {
126 cfgfatal(i->loc,"diffie-hellman","\"%s\" is not a hex number "
130 cfgfatal(loc,"diffie-hellman","you must provide a prime modulus\n");
135 if (i->type!=t_string) {
136 cfgfatal(i->loc,"diffie-hellman","second argument must be a "
140 if (mpz_init_set_str(&st->g,g,16)!=0) {
141 cfgfatal(i->loc,"diffie-hellman","\"%s\" is not a hex number "
145 cfgfatal(loc,"diffie-hellman","you must provide a generator\n");
149 if (i && i->type==t_bool && i->data.bool==False) {
150 Message(M_INFO,"diffie-hellman (%s:%d): skipping modulus "
151 "primality check\n",loc.file,loc.line);
153 /* Test that the modulus is really prime */
154 if (mpz_probab_prime_p(&st->p,5)==0) {
155 cfgfatal(loc,"diffie-hellman","modulus must be a prime\n");
159 size_t sz=mpz_sizeinbase(&st->p,2)/8;
161 cfgfatal(loc,"diffie-hellman","modulus far too large\n");
163 if (mpz_cmp(&st->g,&st->p) >= 0) {
164 cfgfatal(loc,"diffie-hellman","generator must be less than modulus\n");
169 st->ops.ceil_len=(mpz_sizeinbase(&st->p,2)+7)/8;
170 /* According to the docs, mpz_sizeinbase(,256) is allowed to return
171 * an answer which is 1 too large. But mpz_sizeinbase(,2) isn't. */
173 return new_closure(&st->cl);
176 void dh_module(dict_t *dict)
178 add_closure(dict,"diffie-hellman",dh_apply);