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.
42 MP_INT p
,g
; /* prime modulus and generator */
45 static int32_t dh_makepublic(void *sst
, void *public, int32_t publiclen
,
46 uint8_t *secret
, int32_t secretlen
)
49 MP_INT a
, b
; /* a is secret key, b is public key */
54 read_mpbin(&a
, secret
, secretlen
);
56 mpz_powm_sec(&b
, &st
->g
, &a
, &st
->p
);
58 assert(mpz_sizeinbase(&b
, 16) + 2 <= (size_t)publiclen
);
59 mpz_get_str(public, 16, &b
);
64 return strlen(public);
67 static dh_makeshared_fn dh_makeshared
;
68 static bool_t
dh_makeshared(void *sst
, uint8_t *secret
, int32_t secretlen
,
69 const void *public, int32_t publiclen
,
70 uint8_t *sharedsecret
, int32_t buflen
)
79 read_mpbin(&a
, secret
, secretlen
);
80 mpz_set_str(&b
, public, 16);
82 mpz_powm_sec(&c
, &b
, &a
, &st
->p
);
84 write_mpbin(&c
,sharedsecret
,buflen
);
93 static list_t
*dh_apply(closure_t
*self
, struct cloc loc
, dict_t
*context
,
103 st
->cl
.description
="dh";
106 st
->cl
.interface
=&st
->ops
;
108 st
->ops
.makepublic
=dh_makepublic
;
109 st
->ops
.makeshared
=dh_makeshared
;
112 /* We either have two string arguments and maybe a boolean, or a
116 if (i
&& i
->type
==t_dict
) {
118 p
=dict_read_string(dict
,"p",True
,"diffie-hellman",loc
);
119 g
=dict_read_string(dict
,"g",True
,"diffie-hellman",loc
);
120 check
=dict_read_bool(dict
,"check",False
,"diffie-hellman",loc
,True
);
123 cfgfatal(loc
,"diffie-hellman","you must provide a prime modulus\n");
124 else if (i
->type
!=t_string
)
125 cfgfatal(i
->loc
,"diffie-hellman",
126 "first argument must be a string or a dictionary\n");
130 cfgfatal(loc
,"diffie-hellman","you must provide a generator\n");
131 else if (i
->type
!=t_string
)
132 cfgfatal(i
->loc
,"diffie-hellman","second argument must be a "
138 cfgfatal(i
->loc
,"diffie-hellman",
139 "third argument must be boolean or omitted\n");
144 if (mpz_init_set_str(&st
->p
,p
,16)!=0)
145 cfgfatal(loc
,"diffie-hellman","\"%s\" is not a hex number "
147 if (mpz_init_set_str(&st
->g
,g
,16)!=0)
148 cfgfatal(i
->loc
,"diffie-hellman","\"%s\" is not a hex number "
152 Message(M_INFO
,"diffie-hellman (%s:%d): skipping modulus "
153 "primality check\n",loc
.file
,loc
.line
);
155 /* Test that the modulus is really prime */
156 if (mpz_probab_prime_p(&st
->p
,5)==0) {
157 cfgfatal(loc
,"diffie-hellman","modulus must be a prime\n");
161 size_t sz
=mpz_sizeinbase(&st
->p
,2)/8;
163 cfgfatal(loc
,"diffie-hellman","modulus far too large\n");
165 if (mpz_cmp(&st
->g
,&st
->p
) >= 0) {
166 cfgfatal(loc
,"diffie-hellman","generator must be less than modulus\n");
169 st
->ops
.secret_len
=sz
;
171 st
->ops
.shared_len
=(mpz_sizeinbase(&st
->p
,2)+7)/8;
172 /* According to the docs, mpz_sizeinbase(,256) is allowed to return
173 * an answer which is 1 too large. But mpz_sizeinbase(,2) isn't. */
175 st
->ops
.public_len
=(mpz_sizeinbase(&st
->p
,16)+2);
178 st
->ops
.capab_bit
= CAPAB_BIT_TRADZP
;
180 st
->ops
.capab_bit
= dict_read_number(dict
, "capab-num", False
,
181 "dh", loc
, CAPAB_BIT_TRADZP
);
182 if (st
->ops
.capab_bit
> CAPAB_BIT_MAX
)
183 cfgfatal(loc
,"dh","capab-num out of range 0..%d\n",
186 return new_closure(&st
->cl
);
189 void dh_module(dict_t
*dict
)
191 add_closure(dict
,"diffie-hellman",dh_apply
);