| 1 | /* |
| 2 | * xdh.c: x-coordinate-only Montgomery-ladder elliptic-curve Diffie--Hellman |
| 3 | */ |
| 4 | /* |
| 5 | * This file is Free Software. It was originally written for secnet. |
| 6 | * |
| 7 | * Copyright 2017 Mark Wooding |
| 8 | * |
| 9 | * You may redistribute secnet as a whole and/or modify it under the |
| 10 | * terms of the GNU General Public License as published by the Free |
| 11 | * Software Foundation; either version 3, or (at your option) any |
| 12 | * later version. |
| 13 | * |
| 14 | * You may redistribute this file and/or modify it under the terms of |
| 15 | * the GNU General Public License as published by the Free Software |
| 16 | * Foundation; either version 2, or (at your option) any later |
| 17 | * version. |
| 18 | * |
| 19 | * This software is distributed in the hope that it will be useful, |
| 20 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 22 | * GNU General Public License for more details. |
| 23 | * |
| 24 | * You should have received a copy of the GNU General Public License |
| 25 | * along with this software; if not, see |
| 26 | * https://www.gnu.org/licenses/gpl.html. |
| 27 | */ |
| 28 | |
| 29 | #include <stdio.h> |
| 30 | #include <limits.h> |
| 31 | |
| 32 | #include "secnet.h" |
| 33 | #include "magic.h" |
| 34 | #include "util.h" |
| 35 | |
| 36 | #include "x25519.h" |
| 37 | #include "x448.h" |
| 38 | |
| 39 | #define XDH_MAXSZ 64 |
| 40 | |
| 41 | typedef void xdh_fn(uint8_t *z, const uint8_t *k, const uint8_t *x); |
| 42 | |
| 43 | struct xdh { |
| 44 | closure_t cl; |
| 45 | struct dh_if ops; |
| 46 | xdh_fn *fn; |
| 47 | const uint8_t *base; |
| 48 | }; |
| 49 | |
| 50 | static int32_t xdh_makepublic(void *sst, void *pub, int32_t publen, |
| 51 | uint8_t *k, int32_t klen) |
| 52 | { |
| 53 | struct xdh *st = sst; |
| 54 | |
| 55 | assert(klen == st->ops.secret_len); |
| 56 | assert(publen >= st->ops.public_len); |
| 57 | st->fn(pub, k, st->base); |
| 58 | return st->ops.public_len; |
| 59 | } |
| 60 | |
| 61 | static bool_t xdh_makeshared(void *sst, |
| 62 | uint8_t *k, int32_t klen, |
| 63 | const void *pub, int32_t publen, |
| 64 | uint8_t *z, int32_t zlen) |
| 65 | { |
| 66 | struct xdh *st = sst; |
| 67 | |
| 68 | assert(klen == st->ops.secret_len); |
| 69 | assert(zlen >= st->ops.shared_len); |
| 70 | if (publen != st->ops.public_len) { |
| 71 | Message(M_ERR, |
| 72 | "xdh_makeshared: incoming public point has wrong length"); |
| 73 | return False; |
| 74 | } |
| 75 | st->fn(z, k, pub); |
| 76 | return (True); |
| 77 | } |
| 78 | |
| 79 | static void make_xdh_closure(dict_t *dict, const char *name, xdh_fn *fn, |
| 80 | const uint8_t *base, size_t sz, int cap) |
| 81 | { |
| 82 | struct xdh *st; |
| 83 | |
| 84 | NEW(st); |
| 85 | st->cl.description = name; |
| 86 | st->cl.type = CL_DH; |
| 87 | st->cl.apply = 0; |
| 88 | st->cl.interface = &st->ops; |
| 89 | st->ops.st = st; |
| 90 | st->ops.makepublic = xdh_makepublic; |
| 91 | st->ops.makeshared = xdh_makeshared; |
| 92 | st->ops.secret_len = st->ops.public_len = st->ops.shared_len = sz; |
| 93 | st->ops.capab_bit = cap; |
| 94 | st->fn = fn; |
| 95 | st->base = base; |
| 96 | dict_add(dict, name, new_closure(&st->cl)); |
| 97 | } |
| 98 | |
| 99 | void xdh_module(dict_t *dict) |
| 100 | { |
| 101 | make_xdh_closure(dict, "x25519", x25519, x25519_base, |
| 102 | X25519_PUBSZ, CAPAB_BIT_X25519); |
| 103 | make_xdh_closure(dict, "x448", x448, x448_base, |
| 104 | X448_PUBSZ, CAPAB_BIT_X448); |
| 105 | } |