mdw@git.distorted.org.uk Git - tripe/blob - server/chal.c

   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 *bulk;
  33 static uint32 oseq;
  34 static seqwin iseq;
  35
  36 /*----- Main code ---------------------------------------------------------*/
  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   if (bulk && bulk->ops == master->algs.bulk->ops && oseq < 0x07ffffff)
  50     return;
  51   if (bulk) bulk->ops->freechal(bulk);
  52   bulk = master->algs.bulk->ops->genchal(master->algs.bulk);
  53   bulk->ops = master->algs.bulk->ops;
  54   oseq = 0;
  55   seq_reset(&iseq);
  56 }
  57
  58 /* --- @c_new@ --- *
  59  *
  60  * Arguments:   @buf *b@ = where to put the challenge
  61  *
  62  * Returns:     Zero if OK, nonzero on error.
  63  *
  64  * Use:         Issues a new challenge.
  65  */
  66
  67 int c_new(buf *b)
  68 {
  69   octet *p;
  70
  71   c_genkey();
  72   p = BCUR(b);
  73   if (buf_putu32(b, oseq++) || !buf_get(b, bulk->tagsz)) return (-1);
  74   if (bulk->ops->chaltag(bulk, p, 4, p + 4)) return (-1);
  75   IF_TRACING(T_CHAL, {
  76     trace(T_CHAL, "chal: issuing challenge %lu", (unsigned long)(oseq - 1));
  77     trace_block(T_CRYPTO, "chal: challenge block", p, BCUR(b) - p);
  78   })
  79   return (0);
  80 }
  81
  82 /* --- @c_check@ --- *
  83  *
  84  * Arguments:   @buf *b@ = where to find the challenge
  85  *
  86  * Returns:     Zero if OK, nonzero if it didn't work.
  87  *
  88  * Use:         Checks a challenge.  On failure, the buffer is broken.
  89  */
  90
  91 int c_check(buf *b)
  92 {
  93   const octet *p;
  94   size_t sz;
  95   uint32 seq;
  96
  97   if (!bulk) {
  98     a_warn("CHAL", "impossible-challenge", A_END);
  99     goto fail;
 100   }
 101   sz = 4 + bulk->tagsz;
 102   if ((p = buf_get(b, sz)) == 0) {
 103     a_warn("CHAL", "invalid-challenge", A_END);
 104     goto fail;
 105   }
 106   IF_TRACING(T_CHAL, trace_block(T_CRYPTO, "chal: check challenge", p, sz); )
 107   if (bulk->ops->chalvrf(bulk, p, 4, p + 4)) {
 108     a_warn("CHAL", "incorrect-tag", A_END);
 109     goto fail;
 110   }
 111   seq = LOAD32(p);
 112   if (seq_check(&iseq, seq, "CHAL"))
 113     goto fail;
 114   T( trace(T_CHAL, "chal: checked challenge %lu", (unsigned long)seq); )
 115   return (0);
 116
 117 fail:
 118   buf_break(b);
 119   return (-1);
 120 }
 121
 122 /*----- That's all, folks -------------------------------------------------*/