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(&b
, &st
->g
, &a
, &st
->p
);
64 static dh_makeshared_fn dh_makeshared
;
65 static void dh_makeshared(void *sst
, uint8_t *secret
, int32_t secretlen
,
66 cstring_t rempublic
, uint8_t *sharedsecret
,
76 read_mpbin(&a
, secret
, secretlen
);
77 mpz_set_str(&b
, rempublic
, 16);
79 mpz_powm(&c
, &b
, &a
, &st
->p
);
81 write_mpbin(&c
,sharedsecret
,buflen
);
88 static list_t
*dh_apply(closure_t
*self
, struct cloc loc
, dict_t
*context
,
96 st
->cl
.description
="dh";
99 st
->cl
.interface
=&st
->ops
;
101 st
->ops
.makepublic
=dh_makepublic
;
102 st
->ops
.makeshared
=dh_makeshared
;
104 /* We have two string arguments: the first is the modulus, and the
105 second is the generator. Both are in hex. */
108 if (i
->type
!=t_string
) {
109 cfgfatal(i
->loc
,"diffie-hellman","first argument must be a "
113 if (mpz_init_set_str(&st
->p
,p
,16)!=0) {
114 cfgfatal(i
->loc
,"diffie-hellman","\"%s\" is not a hex number "
118 cfgfatal(loc
,"diffie-hellman","you must provide a prime modulus\n");
123 if (i
->type
!=t_string
) {
124 cfgfatal(i
->loc
,"diffie-hellman","second argument must be a "
128 if (mpz_init_set_str(&st
->g
,g
,16)!=0) {
129 cfgfatal(i
->loc
,"diffie-hellman","\"%s\" is not a hex number "
133 cfgfatal(loc
,"diffie-hellman","you must provide a generator\n");
137 if (i
&& i
->type
==t_bool
&& i
->data
.bool==False
) {
138 Message(M_INFO
,"diffie-hellman (%s:%d): skipping modulus "
139 "primality check\n",loc
.file
,loc
.line
);
141 /* Test that the modulus is really prime */
142 if (mpz_probab_prime_p(&st
->p
,5)==0) {
143 cfgfatal(loc
,"diffie-hellman","modulus must be a prime\n");
147 size_t sz
=mpz_sizeinbase(&st
->p
,2)/8;
149 cfgfatal(loc
,"diffie-hellman","modulus far too large\n");
151 if (mpz_cmp(&st
->g
,&st
->p
) >= 0) {
152 cfgfatal(loc
,"diffie-hellman","generator must be less than modulus\n");
157 st
->ops
.ceil_len
=(mpz_sizeinbase(&st
->p
,2)+7)/8;
158 /* According to the docs, mpz_sizeinbase(,256) is allowed to return
159 * an answer which is 1 too large. But mpz_sizeinbase(,2) isn't. */
161 return new_closure(&st
->cl
);
164 void dh_module(dict_t
*dict
)
166 add_closure(dict
,"diffie-hellman",dh_apply
);