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c215a4bc IJ |
1 | /* |
2 | * dh.c | |
3 | */ | |
4 | /* | |
5 | * This file is Free Software. It was originally written for secnet. | |
6 | * | |
7 | * Copyright 1995-2003 Stephen Early | |
8 | * Copyright 2002-2014 Ian Jackson | |
9 | * | |
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 | |
13 | * later version. | |
14 | * | |
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 | |
18 | * version. | |
19 | * | |
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. | |
24 | * | |
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. | |
28 | */ | |
29 | ||
2fe58dfd SE |
30 | #include <stdio.h> |
31 | #include <gmp.h> | |
59230b9b | 32 | #include <limits.h> |
2fe58dfd SE |
33 | |
34 | #include "secnet.h" | |
35 | #include "util.h" | |
36 | ||
37 | struct dh { | |
38 | closure_t cl; | |
39 | struct dh_if ops; | |
40 | struct cloc loc; | |
41 | MP_INT p,g; /* prime modulus and generator */ | |
42 | }; | |
43 | ||
1caa23ff | 44 | static string_t dh_makepublic(void *sst, uint8_t *secret, int32_t secretlen) |
2fe58dfd SE |
45 | { |
46 | struct dh *st=sst; | |
47 | string_t r; | |
48 | MP_INT a, b; /* a is secret key, b is public key */ | |
49 | ||
50 | mpz_init(&a); | |
51 | mpz_init(&b); | |
52 | ||
53 | read_mpbin(&a, secret, secretlen); | |
54 | ||
b6aae8b2 | 55 | mpz_powm_sec(&b, &st->g, &a, &st->p); |
2fe58dfd SE |
56 | |
57 | r=write_mpstring(&b); | |
58 | ||
59 | mpz_clear(&a); | |
60 | mpz_clear(&b); | |
61 | return r; | |
62 | } | |
63 | ||
fe5e9cc4 | 64 | static dh_makeshared_fn dh_makeshared; |
1caa23ff | 65 | static void dh_makeshared(void *sst, uint8_t *secret, int32_t secretlen, |
fe5e9cc4 | 66 | cstring_t rempublic, uint8_t *sharedsecret, |
1caa23ff | 67 | int32_t buflen) |
2fe58dfd SE |
68 | { |
69 | struct dh *st=sst; | |
70 | MP_INT a, b, c; | |
71 | ||
72 | mpz_init(&a); | |
73 | mpz_init(&b); | |
74 | mpz_init(&c); | |
75 | ||
76 | read_mpbin(&a, secret, secretlen); | |
77 | mpz_set_str(&b, rempublic, 16); | |
78 | ||
b6aae8b2 | 79 | mpz_powm_sec(&c, &b, &a, &st->p); |
2fe58dfd SE |
80 | |
81 | write_mpbin(&c,sharedsecret,buflen); | |
82 | ||
83 | mpz_clear(&a); | |
84 | mpz_clear(&b); | |
85 | mpz_clear(&c); | |
86 | } | |
87 | ||
88 | static list_t *dh_apply(closure_t *self, struct cloc loc, dict_t *context, | |
89 | list_t *args) | |
90 | { | |
91 | struct dh *st; | |
92 | string_t p,g; | |
93 | item_t *i; | |
94 | ||
b7886fd4 | 95 | NEW(st); |
2fe58dfd SE |
96 | st->cl.description="dh"; |
97 | st->cl.type=CL_DH; | |
98 | st->cl.apply=NULL; | |
99 | st->cl.interface=&st->ops; | |
100 | st->ops.st=st; | |
101 | st->ops.makepublic=dh_makepublic; | |
102 | st->ops.makeshared=dh_makeshared; | |
103 | st->loc=loc; | |
104 | /* We have two string arguments: the first is the modulus, and the | |
105 | second is the generator. Both are in hex. */ | |
106 | i=list_elem(args,0); | |
107 | if (i) { | |
108 | if (i->type!=t_string) { | |
109 | cfgfatal(i->loc,"diffie-hellman","first argument must be a " | |
110 | "string\n"); | |
111 | } | |
112 | p=i->data.string; | |
113 | if (mpz_init_set_str(&st->p,p,16)!=0) { | |
114 | cfgfatal(i->loc,"diffie-hellman","\"%s\" is not a hex number " | |
115 | "string\n",p); | |
116 | } | |
117 | } else { | |
118 | cfgfatal(loc,"diffie-hellman","you must provide a prime modulus\n"); | |
119 | } | |
120 | ||
121 | i=list_elem(args,1); | |
122 | if (i) { | |
123 | if (i->type!=t_string) { | |
124 | cfgfatal(i->loc,"diffie-hellman","second argument must be a " | |
125 | "string\n"); | |
126 | } | |
127 | g=i->data.string; | |
128 | if (mpz_init_set_str(&st->g,g,16)!=0) { | |
129 | cfgfatal(i->loc,"diffie-hellman","\"%s\" is not a hex number " | |
130 | "string\n",g); | |
131 | } | |
132 | } else { | |
133 | cfgfatal(loc,"diffie-hellman","you must provide a generator\n"); | |
134 | } | |
135 | ||
70dc107b SE |
136 | i=list_elem(args,2); |
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); | |
140 | } else { | |
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"); | |
144 | } | |
2fe58dfd | 145 | } |
59230b9b IJ |
146 | |
147 | size_t sz=mpz_sizeinbase(&st->p,2)/8; | |
148 | if (sz>INT_MAX) { | |
149 | cfgfatal(loc,"diffie-hellman","modulus far too large\n"); | |
150 | } | |
151 | if (mpz_cmp(&st->g,&st->p) >= 0) { | |
152 | cfgfatal(loc,"diffie-hellman","generator must be less than modulus\n"); | |
153 | } | |
154 | ||
155 | st->ops.len=sz; | |
2fe58dfd | 156 | |
7c9ca4bd IJ |
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. */ | |
160 | ||
2fe58dfd SE |
161 | return new_closure(&st->cl); |
162 | } | |
163 | ||
2fe58dfd SE |
164 | void dh_module(dict_t *dict) |
165 | { | |
166 | add_closure(dict,"diffie-hellman",dh_apply); | |
167 | } |