| 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 | |
| 30 | #include <stdio.h> |
| 31 | #include <gmp.h> |
| 32 | #include <limits.h> |
| 33 | |
| 34 | #include "secnet.h" |
| 35 | #include "magic.h" |
| 36 | #include "util.h" |
| 37 | |
| 38 | struct dh { |
| 39 | closure_t cl; |
| 40 | struct dh_if ops; |
| 41 | struct cloc loc; |
| 42 | MP_INT p,g; /* prime modulus and generator */ |
| 43 | }; |
| 44 | |
| 45 | static int32_t dh_makepublic(void *sst, void *public, int32_t publiclen, |
| 46 | uint8_t *secret, int32_t secretlen) |
| 47 | { |
| 48 | struct dh *st=sst; |
| 49 | MP_INT a, b; /* a is secret key, b is public key */ |
| 50 | |
| 51 | mpz_init(&a); |
| 52 | mpz_init(&b); |
| 53 | |
| 54 | read_mpbin(&a, secret, secretlen); |
| 55 | |
| 56 | mpz_powm_sec(&b, &st->g, &a, &st->p); |
| 57 | |
| 58 | assert(mpz_sizeinbase(&b, 16) + 2 <= (size_t)publiclen); |
| 59 | mpz_get_str(public, 16, &b); |
| 60 | |
| 61 | mpz_clear(&a); |
| 62 | mpz_clear(&b); |
| 63 | |
| 64 | return strlen(public); |
| 65 | } |
| 66 | |
| 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) |
| 71 | { |
| 72 | struct dh *st=sst; |
| 73 | MP_INT a, b, c; |
| 74 | |
| 75 | mpz_init(&a); |
| 76 | mpz_init(&b); |
| 77 | mpz_init(&c); |
| 78 | |
| 79 | read_mpbin(&a, secret, secretlen); |
| 80 | mpz_set_str(&b, public, 16); |
| 81 | |
| 82 | mpz_powm_sec(&c, &b, &a, &st->p); |
| 83 | |
| 84 | write_mpbin(&c,sharedsecret,buflen); |
| 85 | |
| 86 | mpz_clear(&a); |
| 87 | mpz_clear(&b); |
| 88 | mpz_clear(&c); |
| 89 | |
| 90 | return True; |
| 91 | } |
| 92 | |
| 93 | static list_t *dh_apply(closure_t *self, struct cloc loc, dict_t *context, |
| 94 | list_t *args) |
| 95 | { |
| 96 | struct dh *st; |
| 97 | string_t p,g; |
| 98 | dict_t *dict = 0; |
| 99 | item_t *i; |
| 100 | bool_t check = True; |
| 101 | |
| 102 | NEW(st); |
| 103 | st->cl.description="dh"; |
| 104 | st->cl.type=CL_DH; |
| 105 | st->cl.apply=NULL; |
| 106 | st->cl.interface=&st->ops; |
| 107 | st->ops.st=st; |
| 108 | st->ops.makepublic=dh_makepublic; |
| 109 | st->ops.makeshared=dh_makeshared; |
| 110 | st->loc=loc; |
| 111 | |
| 112 | /* We either have two string arguments and maybe a boolean, or a |
| 113 | * dictionary |
| 114 | */ |
| 115 | i=list_elem(args,0); |
| 116 | if (i && i->type==t_dict) { |
| 117 | dict=i->data.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); |
| 121 | } else { |
| 122 | if (!i) |
| 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"); |
| 127 | p=i->data.string; |
| 128 | i=list_elem(args,1); |
| 129 | if (!i) |
| 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 " |
| 133 | "string\n"); |
| 134 | g=i->data.string; |
| 135 | i=list_elem(args,2); |
| 136 | if (i) { |
| 137 | if (i->type!=t_bool) |
| 138 | cfgfatal(i->loc,"diffie-hellman", |
| 139 | "third argument must be boolean or omitted\n"); |
| 140 | check=i->data.bool; |
| 141 | } |
| 142 | } |
| 143 | |
| 144 | if (mpz_init_set_str(&st->p,p,16)!=0) |
| 145 | cfgfatal(loc,"diffie-hellman","\"%s\" is not a hex number " |
| 146 | "string\n",p); |
| 147 | if (mpz_init_set_str(&st->g,g,16)!=0) |
| 148 | cfgfatal(i->loc,"diffie-hellman","\"%s\" is not a hex number " |
| 149 | "string\n",g); |
| 150 | |
| 151 | if (!check) { |
| 152 | Message(M_INFO,"diffie-hellman (%s:%d): skipping modulus " |
| 153 | "primality check\n",loc.file,loc.line); |
| 154 | } else { |
| 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"); |
| 158 | } |
| 159 | } |
| 160 | |
| 161 | size_t sz=mpz_sizeinbase(&st->p,2)/8; |
| 162 | if (sz>INT_MAX) { |
| 163 | cfgfatal(loc,"diffie-hellman","modulus far too large\n"); |
| 164 | } |
| 165 | if (mpz_cmp(&st->g,&st->p) >= 0) { |
| 166 | cfgfatal(loc,"diffie-hellman","generator must be less than modulus\n"); |
| 167 | } |
| 168 | |
| 169 | st->ops.secret_len=sz; |
| 170 | |
| 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. */ |
| 174 | |
| 175 | st->ops.public_len=(mpz_sizeinbase(&st->p,16)+2); |
| 176 | |
| 177 | if (!dict) |
| 178 | st->ops.capab_bit = CAPAB_BIT_TRADZP; |
| 179 | else |
| 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", |
| 184 | CAPAB_BIT_MAX); |
| 185 | |
| 186 | return new_closure(&st->cl); |
| 187 | } |
| 188 | |
| 189 | void dh_module(dict_t *dict) |
| 190 | { |
| 191 | add_closure(dict,"diffie-hellman",dh_apply); |
| 192 | } |