1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
|
/*
* dh.c
*/
/*
* This file is Free Software. It was originally written for secnet.
*
* Copyright 1995-2003 Stephen Early
* Copyright 2002-2014 Ian Jackson
*
* You may redistribute secnet as a whole and/or modify it under the
* terms of the GNU General Public License as published by the Free
* Software Foundation; either version 3, or (at your option) any
* later version.
*
* You may redistribute this file and/or modify it under the terms of
* the GNU General Public License as published by the Free Software
* Foundation; either version 2, or (at your option) any later
* version.
*
* This software is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this software; if not, see
* https://www.gnu.org/licenses/gpl.html.
*/
#include <stdio.h>
#include <gmp.h>
#include <limits.h>
#include "secnet.h"
#include "util.h"
struct dh {
closure_t cl;
struct dh_if ops;
struct cloc loc;
MP_INT p,g; /* prime modulus and generator */
};
static string_t dh_makepublic(void *sst, uint8_t *secret, int32_t secretlen)
{
struct dh *st=sst;
string_t r;
MP_INT a, b; /* a is secret key, b is public key */
mpz_init(&a);
mpz_init(&b);
read_mpbin(&a, secret, secretlen);
mpz_powm_sec(&b, &st->g, &a, &st->p);
r=write_mpstring(&b);
mpz_clear(&a);
mpz_clear(&b);
return r;
}
static void write_mpbin_anomalous(MP_INT *a, uint8_t *buffer,
int32_t buflen)
/* If the BN is smaller than buflen, pads it *at the wrong end* */
{
char *hb = write_mpstring(a);
int32_t len;
hex_decode(buffer, buflen, &len, hb, True);
if (len<buflen)
memset(buffer+len,0,buflen-len);
free(hb);
}
static dh_makeshared_fn dh_makeshared;
static void dh_makeshared(void *sst, uint8_t *secret, int32_t secretlen,
cstring_t rempublic, uint8_t *sharedsecret,
int32_t buflen)
{
struct dh *st=sst;
MP_INT a, b, c;
mpz_init(&a);
mpz_init(&b);
mpz_init(&c);
read_mpbin(&a, secret, secretlen);
mpz_set_str(&b, rempublic, 16);
mpz_powm_sec(&c, &b, &a, &st->p);
write_mpbin_anomalous(&c,sharedsecret,buflen);
mpz_clear(&a);
mpz_clear(&b);
mpz_clear(&c);
}
static list_t *dh_apply(closure_t *self, struct cloc loc, dict_t *context,
list_t *args)
{
struct dh *st;
string_t p,g;
item_t *i;
NEW(st);
st->cl.description="dh";
st->cl.type=CL_DH;
st->cl.apply=NULL;
st->cl.interface=&st->ops;
st->ops.st=st;
st->ops.makepublic=dh_makepublic;
st->ops.makeshared=dh_makeshared;
st->loc=loc;
/* We have two string arguments: the first is the modulus, and the
second is the generator. Both are in hex. */
i=list_elem(args,0);
if (i) {
if (i->type!=t_string) {
cfgfatal(i->loc,"diffie-hellman","first argument must be a "
"string\n");
}
p=i->data.string;
if (mpz_init_set_str(&st->p,p,16)!=0) {
cfgfatal(i->loc,"diffie-hellman","\"%s\" is not a hex number "
"string\n",p);
}
} else {
cfgfatal(loc,"diffie-hellman","you must provide a prime modulus\n");
}
i=list_elem(args,1);
if (i) {
if (i->type!=t_string) {
cfgfatal(i->loc,"diffie-hellman","second argument must be a "
"string\n");
}
g=i->data.string;
if (mpz_init_set_str(&st->g,g,16)!=0) {
cfgfatal(i->loc,"diffie-hellman","\"%s\" is not a hex number "
"string\n",g);
}
} else {
cfgfatal(loc,"diffie-hellman","you must provide a generator\n");
}
i=list_elem(args,2);
if (i && i->type==t_bool && i->data.bool_==False) {
Message(M_INFO,"diffie-hellman (%s:%d): skipping modulus "
"primality check\n",loc.file,loc.line);
} else {
/* Test that the modulus is really prime */
if (mpz_probab_prime_p(&st->p,5)==0) {
cfgfatal(loc,"diffie-hellman","modulus must be a prime\n");
}
}
size_t sz=mpz_sizeinbase(&st->p,2)/8;
if (sz>INT_MAX) {
cfgfatal(loc,"diffie-hellman","modulus far too large\n");
}
if (mpz_cmp(&st->g,&st->p) >= 0) {
cfgfatal(loc,"diffie-hellman","generator must be less than modulus\n");
}
st->ops.len=sz;
st->ops.ceil_len=(mpz_sizeinbase(&st->p,2)+7)/8;
/* According to the docs, mpz_sizeinbase(,256) is allowed to return
* an answer which is 1 too large. But mpz_sizeinbase(,2) isn't. */
return new_closure(&st->cl);
}
void dh_module(dict_t *dict)
{
add_closure(dict,"diffie-hellman",dh_apply);
}
|
