| 1 | /* |
| 2 | * PKCS#5 padding mechanism for udp tunnel |
| 3 | * |
| 4 | * mechanism: pkcs5 |
| 5 | * arguments: block size to pad to, must be power of 2 and <=128 |
| 6 | * |
| 7 | * restrictions: none |
| 8 | * encoding: append between 1 and n bytes, all of the same value being |
| 9 | * the number of bytes appended |
| 10 | */ |
| 11 | /* |
| 12 | * Copyright (C) 2000 Ian Jackson |
| 13 | * |
| 14 | * This is free software; you can redistribute it and/or modify it |
| 15 | * under the terms of the GNU General Public License as published by |
| 16 | * the Free Software Foundation; either version 2 of the License, or |
| 17 | * (at your option) any later version. |
| 18 | * |
| 19 | * This program is distributed in the hope that it will be useful, but |
| 20 | * WITHOUT ANY WARRANTY; without even the implied warranty of |
| 21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 22 | * General Public License for more details. |
| 23 | * |
| 24 | * You should have received a copy of the GNU General Public License |
| 25 | * along with userv-utils; if not, write to the Free Software |
| 26 | * Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
| 27 | */ |
| 28 | |
| 29 | #include "forwarder.h" |
| 30 | |
| 31 | struct mechdata { |
| 32 | unsigned mask; |
| 33 | }; |
| 34 | |
| 35 | static unsigned long setup(struct mechdata **md_r) { |
| 36 | struct mechdata *md; |
| 37 | unsigned long blocksize; |
| 38 | |
| 39 | XMALLOC(md); |
| 40 | |
| 41 | blocksize= getarg_ulong(); |
| 42 | md->mask= blocksize - 1; |
| 43 | arg_assert(!(md->mask & blocksize)); |
| 44 | arg_assert(blocksize <= 255); |
| 45 | |
| 46 | *md_r= md; |
| 47 | return blocksize; |
| 48 | } |
| 49 | |
| 50 | static void mes_pkcs5(struct mechdata **md_r, int *maxprefix_io, int *maxsuffix_io) { |
| 51 | unsigned long blocksize; |
| 52 | |
| 53 | blocksize= setup(md_r); |
| 54 | *maxsuffix_io += blocksize + 1; |
| 55 | } |
| 56 | |
| 57 | static void mds_pkcs5(struct mechdata **md_r) { |
| 58 | setup(md_r); |
| 59 | } |
| 60 | |
| 61 | static void menc_pkcs5(struct mechdata *md, struct buffer *buf) { |
| 62 | unsigned char *pad; |
| 63 | int padlen; |
| 64 | |
| 65 | /* eg with blocksize=4 mask=3 mask+2=5 */ |
| 66 | /* msgsize 20 21 22 23 24 */ |
| 67 | padlen= md->mask - buf->size; /* -17 -18 -19 -16 -17 */ |
| 68 | padlen &= md->mask; /* 3 2 1 0 3 */ |
| 69 | padlen++; /* 4 3 2 1 4 */ |
| 70 | |
| 71 | pad= buf_append(buf,padlen); |
| 72 | memset(pad,padlen,padlen); |
| 73 | } |
| 74 | |
| 75 | static const char *mdec_pkcs5(struct mechdata *md, struct buffer *buf) { |
| 76 | unsigned char *padp; |
| 77 | unsigned padlen; |
| 78 | int i; |
| 79 | |
| 80 | BUF_UNAPPEND(padp,buf,1); |
| 81 | padlen= *padp; |
| 82 | if (!padlen || (padlen > md->mask+1)) return "invalid length"; |
| 83 | |
| 84 | BUF_UNAPPEND(padp,buf,padlen-1); |
| 85 | for (i=0; i<padlen-1; i++) |
| 86 | if (*++padp != padlen) return "corrupted padding"; |
| 87 | |
| 88 | return 0; |
| 89 | } |
| 90 | |
| 91 | STANDARD_MECHANISMLIST("pkcs5",pkcs5) |