| 1 | /* |
| 2 | * Sequence number / nonce mechanism for udp tunnel |
| 3 | * |
| 4 | * mechanisms: nonce, sequence |
| 5 | * arguments: none |
| 6 | * |
| 7 | * restrictions: none |
| 8 | * encoding: prepend 4 bytes of sequence arithmetic serial number |
| 9 | * decoding: check increasingness (sequence), or ignore (nonce) |
| 10 | */ |
| 11 | /* |
| 12 | * This file is part of ipif, part of userv-utils |
| 13 | * |
| 14 | * Copyright 1996-2013 Ian Jackson <ijackson@chiark.greenend.org.uk> |
| 15 | * Copyright 1998 David Damerell <damerell@chiark.greenend.org.uk> |
| 16 | * Copyright 1999,2003 |
| 17 | * Chancellor Masters and Scholars of the University of Cambridge |
| 18 | * Copyright 2010 Tony Finch <fanf@dotat.at> |
| 19 | * |
| 20 | * This is free software; you can redistribute it and/or modify it |
| 21 | * under the terms of the GNU General Public License as published by |
| 22 | * the Free Software Foundation; either version 3 of the License, or |
| 23 | * (at your option) any later version. |
| 24 | * |
| 25 | * This program is distributed in the hope that it will be useful, but |
| 26 | * WITHOUT ANY WARRANTY; without even the implied warranty of |
| 27 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 28 | * General Public License for more details. |
| 29 | * |
| 30 | * You should have received a copy of the GNU General Public License |
| 31 | * along with userv-utils; if not, see http://www.gnu.org/licenses/. |
| 32 | */ |
| 33 | |
| 34 | #include <netinet/in.h> |
| 35 | |
| 36 | #include "forwarder.h" |
| 37 | |
| 38 | struct mechdata { |
| 39 | uint32_t number; |
| 40 | int anyseen; /* decode only */ |
| 41 | }; |
| 42 | |
| 43 | static void mes_sequence(struct mechdata **md_r, int *maxprefix_io, int *maxsuffix_io) { |
| 44 | struct mechdata *md; |
| 45 | |
| 46 | XMALLOC(md); |
| 47 | get_random(&md->number,sizeof(md->number)); |
| 48 | *maxprefix_io += 4; |
| 49 | *md_r= md; |
| 50 | } |
| 51 | |
| 52 | static void mds_sequence(struct mechdata **md_r) { |
| 53 | struct mechdata *md; |
| 54 | XMALLOC(md); |
| 55 | md->anyseen= 0; |
| 56 | *md_r= md; |
| 57 | } |
| 58 | |
| 59 | static void menc_sequence(struct mechdata *md, struct buffer *buf) { |
| 60 | md->number++; |
| 61 | *(uint32_t*)buf_prepend(buf,4)= htonl(md->number); |
| 62 | } |
| 63 | |
| 64 | static const char *mdec_check(struct mechdata *md, struct buffer *buf) { |
| 65 | uint32_t *sp, sequence; |
| 66 | |
| 67 | BUF_UNPREPEND(sp,buf,4); |
| 68 | sequence= ntohl(*sp); |
| 69 | |
| 70 | if (md->anyseen) |
| 71 | if (sequence - md->number >= 0x800000UL) return "out of order packet"; |
| 72 | |
| 73 | md->number= sequence; |
| 74 | md->anyseen= 1; |
| 75 | |
| 76 | return 0; |
| 77 | } |
| 78 | |
| 79 | static const char *mdec_skip(struct mechdata *md, struct buffer *buf) { |
| 80 | uint32_t *sp; |
| 81 | BUF_UNPREPEND(sp,buf,4); |
| 82 | return 0; |
| 83 | } |
| 84 | |
| 85 | const struct mechanism mechlist_sequence[]= { |
| 86 | { "nonce", mes_sequence, mds_sequence, menc_sequence, mdec_skip }, |
| 87 | { "sequence", mes_sequence, mds_sequence, menc_sequence, mdec_check }, |
| 88 | { 0 } |
| 89 | }; |