| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * Cryptographic challenges |
| 4 | * |
| 5 | * (c) 2005 Straylight/Edgeware |
| 6 | */ |
| 7 | |
| 8 | /*----- Licensing notice --------------------------------------------------* |
| 9 | * |
| 10 | * This file is part of Trivial IP Encryption (TrIPE). |
| 11 | * |
| 12 | * TrIPE is free software; you can redistribute it and/or modify |
| 13 | * it under the terms of the GNU General Public License as published by |
| 14 | * the Free Software Foundation; either version 2 of the License, or |
| 15 | * (at your option) any later version. |
| 16 | * |
| 17 | * TrIPE is distributed in the hope that it will be useful, |
| 18 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 20 | * GNU General Public License for more details. |
| 21 | * |
| 22 | * You should have received a copy of the GNU General Public License |
| 23 | * along with TrIPE; if not, write to the Free Software Foundation, |
| 24 | * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
| 25 | */ |
| 26 | |
| 27 | /*----- Header files ------------------------------------------------------*/ |
| 28 | |
| 29 | #include "tripe.h" |
| 30 | |
| 31 | /*----- Static variables --------------------------------------------------*/ |
| 32 | |
| 33 | static gmac *mac; |
| 34 | static uint32 oseq; |
| 35 | static seqwin iseq; |
| 36 | |
| 37 | /*----- Main code ---------------------------------------------------------*/ |
| 38 | |
| 39 | /* --- @c_genkey@ --- * |
| 40 | * |
| 41 | * Arguments: --- |
| 42 | * |
| 43 | * Returns: --- |
| 44 | * |
| 45 | * Use: Generates a new challenge key. |
| 46 | */ |
| 47 | |
| 48 | static void c_genkey(void) |
| 49 | { |
| 50 | if (mac && GM_CLASS(mac) == master->algs.m && oseq < 0x07ffffff) return; |
| 51 | if (mac) GM_DESTROY(mac); |
| 52 | assert(master->algs.mksz < sizeof(buf_t)); |
| 53 | rand_get(RAND_GLOBAL, buf_t, master->algs.mksz); |
| 54 | mac = GM_KEY(master->algs.m, buf_t, master->algs.mksz); |
| 55 | oseq = 0; |
| 56 | seq_reset(&iseq); |
| 57 | IF_TRACING(T_CHAL, { |
| 58 | trace(T_CHAL, "chal: generated new challenge key"); |
| 59 | trace_block(T_CRYPTO, "chal: new key", buf_t, master->algs.mksz); |
| 60 | }) |
| 61 | } |
| 62 | |
| 63 | /* --- @c_new@ --- * |
| 64 | * |
| 65 | * Arguments: @buf *b@ = where to put the challenge |
| 66 | * |
| 67 | * Returns: Zero if OK, nonzero on error. |
| 68 | * |
| 69 | * Use: Issues a new challenge. |
| 70 | */ |
| 71 | |
| 72 | int c_new(buf *b) |
| 73 | { |
| 74 | octet *p; |
| 75 | ghash *h; |
| 76 | |
| 77 | c_genkey(); |
| 78 | p = BCUR(b); |
| 79 | if (buf_putu32(b, oseq++)) return (-1); |
| 80 | h = GM_INIT(mac); |
| 81 | GH_HASH(h, p, BCUR(b) - p); |
| 82 | buf_put(b, GH_DONE(h, 0), master->algs.tagsz); |
| 83 | GH_DESTROY(h); |
| 84 | if (BBAD(b)) return (-1); |
| 85 | IF_TRACING(T_CHAL, { |
| 86 | trace(T_CHAL, "chal: issuing challenge %lu", (unsigned long)(oseq - 1)); |
| 87 | trace_block(T_CRYPTO, "chal: challenge block", p, BCUR(b) - p); |
| 88 | }) |
| 89 | return (0); |
| 90 | } |
| 91 | |
| 92 | /* --- @c_check@ --- * |
| 93 | * |
| 94 | * Arguments: @buf *b@ = where to find the challenge |
| 95 | * |
| 96 | * Returns: Zero if OK, nonzero if it didn't work. |
| 97 | * |
| 98 | * Use: Checks a challenge. On failure, the buffer is broken. |
| 99 | */ |
| 100 | |
| 101 | int c_check(buf *b) |
| 102 | { |
| 103 | const octet *p; |
| 104 | size_t sz = 4 + master->algs.tagsz; |
| 105 | uint32 seq; |
| 106 | ghash *h; |
| 107 | int ok; |
| 108 | |
| 109 | if ((p = buf_get(b, sz)) == 0) { |
| 110 | a_warn("CHAL", "invalid-challenge", A_END); |
| 111 | goto fail; |
| 112 | } |
| 113 | IF_TRACING(T_CHAL, trace_block(T_CRYPTO, "chal: check challenge", p, sz); ) |
| 114 | if (!mac) { |
| 115 | a_warn("CHAL", "impossible-challenge", A_END); |
| 116 | goto fail; |
| 117 | } |
| 118 | h = GM_INIT(mac); |
| 119 | GH_HASH(h, p, 4); |
| 120 | ok = ct_memeq(GH_DONE(h, 0), p + 4, master->algs.tagsz); |
| 121 | GH_DESTROY(h); |
| 122 | if (!ok) { |
| 123 | a_warn("CHAL", "incorrect-tag", A_END); |
| 124 | goto fail; |
| 125 | } |
| 126 | seq = LOAD32(p); |
| 127 | if (seq_check(&iseq, LOAD32(p), "CHAL")) |
| 128 | goto fail; |
| 129 | T( trace(T_CHAL, "chal: checked challenge %lu", (unsigned long)seq); ) |
| 130 | return (0); |
| 131 | |
| 132 | fail: |
| 133 | buf_break(b); |
| 134 | return (-1); |
| 135 | } |
| 136 | |
| 137 | /*----- That's all, folks -------------------------------------------------*/ |