| 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 it under |
| 13 | * the terms of the GNU General Public License as published by the Free |
| 14 | * Software Foundation; either version 3 of the License, or (at your |
| 15 | * option) any later version. |
| 16 | * |
| 17 | * TrIPE is distributed in the hope that it will be useful, but WITHOUT |
| 18 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| 19 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| 20 | * for more details. |
| 21 | * |
| 22 | * You should have received a copy of the GNU General Public License |
| 23 | * along with TrIPE. If not, see <https://www.gnu.org/licenses/>. |
| 24 | */ |
| 25 | |
| 26 | /*----- Header files ------------------------------------------------------*/ |
| 27 | |
| 28 | #include "tripe.h" |
| 29 | |
| 30 | /*----- Static variables --------------------------------------------------*/ |
| 31 | |
| 32 | static bulkchal *bchal; |
| 33 | static uint32 oseq; |
| 34 | static seqwin iseq; |
| 35 | |
| 36 | /*----- Challenges --------------------------------------------------------*/ |
| 37 | |
| 38 | /* --- @c_genkey@ --- * |
| 39 | * |
| 40 | * Arguments: --- |
| 41 | * |
| 42 | * Returns: --- |
| 43 | * |
| 44 | * Use: Generates a new challenge key. |
| 45 | */ |
| 46 | |
| 47 | static void c_genkey(void) |
| 48 | { |
| 49 | bulkalgs *bulk = master->algs.bulk; |
| 50 | if (bchal && bchal->ops == bulk->ops && oseq < 0x07ffffff) return; |
| 51 | if (bchal) bchal->ops->freechal(bchal); |
| 52 | bchal = bulk->ops->genchal(bulk); |
| 53 | bchal->ops = bulk->ops; |
| 54 | oseq = 0; |
| 55 | seq_reset(&iseq); |
| 56 | } |
| 57 | |
| 58 | /* --- @c_new@ --- * |
| 59 | * |
| 60 | * Arguments: @const void *m@ = pointer to associated message, or null |
| 61 | * @size_t msz@ = length of associated message |
| 62 | * @buf *b@ = where to put the challenge |
| 63 | * |
| 64 | * Returns: Zero if OK, nonzero on error. |
| 65 | * |
| 66 | * Use: Issues a new challenge. |
| 67 | */ |
| 68 | |
| 69 | int c_new(const void *m, size_t msz, buf *b) |
| 70 | { |
| 71 | const octet *p; |
| 72 | octet *t; |
| 73 | int rc; |
| 74 | |
| 75 | c_genkey(); |
| 76 | p = BCUR(b); |
| 77 | if (buf_putu32(b, oseq) || (t = buf_get(b, bchal->tagsz)) == 0) |
| 78 | { rc = -1; goto done; } |
| 79 | if (bchal->ops->chaltag(bchal, m, msz, oseq, t)) { rc = -1; goto done; } |
| 80 | IF_TRACING(T_CHAL, { |
| 81 | trace(T_CHAL, "chal: issuing challenge %lu", (unsigned long)oseq); |
| 82 | if (msz) trace_block(T_CRYPTO, "chal: message block", m, msz); |
| 83 | trace_block(T_CRYPTO, "chal: challenge block", p, BCUR(b) - p); |
| 84 | }) |
| 85 | rc = 0; |
| 86 | done: |
| 87 | oseq++; |
| 88 | return (rc); |
| 89 | } |
| 90 | |
| 91 | /* --- @c_check@ --- * |
| 92 | * |
| 93 | * Arguments: @const void *m@ = pointer to associated message, or null |
| 94 | * @size_t msz@ = length of associated message |
| 95 | * @buf *b@ = where to find the challenge |
| 96 | * |
| 97 | * Returns: Zero if OK, nonzero if it didn't work. |
| 98 | * |
| 99 | * Use: Checks a challenge. On failure, the buffer is broken. |
| 100 | */ |
| 101 | |
| 102 | int c_check(const void *m, size_t msz, buf *b) |
| 103 | { |
| 104 | const octet *p, *t; |
| 105 | uint32 seq; |
| 106 | |
| 107 | if (!bchal) { |
| 108 | a_warn("CHAL", "impossible-challenge", A_END); |
| 109 | goto fail; |
| 110 | } |
| 111 | p = BCUR(b); |
| 112 | if (buf_getu32(b, &seq) || (t = buf_get(b, bchal->tagsz)) == 0) { |
| 113 | a_warn("CHAL", "invalid-challenge", A_END); |
| 114 | goto fail; |
| 115 | } |
| 116 | IF_TRACING(T_CHAL, { |
| 117 | trace(T_CHAL, "chal: checking challenge, seq = %lu", (unsigned long)seq); |
| 118 | if (msz) trace_block(T_CRYPTO, "chal: message block", m, msz); |
| 119 | trace_block(T_CRYPTO, "chal: check challenge", p, BCUR(b) - p); |
| 120 | }) |
| 121 | if (bchal->ops->chalvrf(bchal, m, msz, seq, t)) { |
| 122 | a_warn("CHAL", "incorrect-tag", A_END); |
| 123 | goto fail; |
| 124 | } |
| 125 | if (seq_check(&iseq, seq, "CHAL")) goto fail; |
| 126 | T( trace(T_CHAL, "chal: challenge ok"); ) |
| 127 | return (0); |
| 128 | |
| 129 | fail: |
| 130 | buf_break(b); |
| 131 | return (-1); |
| 132 | } |
| 133 | |
| 134 | /*----- That's all, folks -------------------------------------------------*/ |