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 *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
  51   if (bchal && bchal->ops == bulk->ops && oseq < 0x07ffffff) return;
  52   if (bchal) bchal->ops->freechal(bchal);
  53   bchal = bulk->ops->genchal(bulk);
  54   bchal->ops = bulk->ops;
  55   oseq = 0;
  56   seq_reset(&iseq);
  57 }
  58
  59 /* --- @c_new@ --- *
  60  *
  61  * Arguments:   @const void *m@ = pointer to associated message, or null
  62  *              @size_t msz@ = length of associated message
  63  *              @buf *b@ = where to put the challenge
  64  *
  65  * Returns:     Zero if OK, nonzero on error.
  66  *
  67  * Use:         Issues a new challenge.
  68  */
  69
  70 int c_new(const void *m, size_t msz, buf *b)
  71 {
  72   const octet *p;
  73   octet *t;
  74   int rc;
  75
  76   c_genkey();
  77   p = BCUR(b);
  78   if (buf_putu32(b, oseq) || (t = buf_get(b, bchal->tagsz)) == 0)
  79     { rc = -1; goto done; }
  80   if (bchal->ops->chaltag(bchal, m, msz, oseq, t)) { rc = -1; goto done; }
  81   IF_TRACING(T_CHAL, {
  82     trace(T_CHAL, "chal: issuing challenge %lu", (unsigned long)oseq);
  83     if (msz) trace_block(T_CRYPTO, "chal: message block", m, msz);
  84     trace_block(T_CRYPTO, "chal: challenge block", p, BCUR(b) - p);
  85   })
  86   rc = 0;
  87 done:
  88   oseq++;
  89   return (rc);
  90 }
  91
  92 /* --- @c_check@ --- *
  93  *
  94  * Arguments:   @const void *m@ = pointer to associated message, or null
  95  *              @size_t msz@ = length of associated message
  96  *              @buf *b@ = where to find the challenge
  97  *
  98  * Returns:     Zero if OK, nonzero if it didn't work.
  99  *
 100  * Use:         Checks a challenge.  On failure, the buffer is broken.
 101  */
 102
 103 int c_check(const void *m, size_t msz, buf *b)
 104 {
 105   const octet *p, *t;
 106   uint32 seq;
 107
 108   if (!bchal) {
 109     a_warn("CHAL", "impossible-challenge", A_END);
 110     goto fail;
 111   }
 112   p = BCUR(b);
 113   if (buf_getu32(b, &seq) || (t = buf_get(b, bchal->tagsz)) == 0) {
 114     a_warn("CHAL", "invalid-challenge", A_END);
 115     goto fail;
 116   }
 117   IF_TRACING(T_CHAL, {
 118     trace(T_CHAL, "chal: checking challenge, seq = %lu", (unsigned long)seq);
 119     if (msz) trace_block(T_CRYPTO, "chal: message block", m, msz);
 120     trace_block(T_CRYPTO, "chal: check challenge", p, BCUR(b) - p);
 121   })
 122   if (bchal->ops->chalvrf(bchal, m, msz, seq, t)) {
 123     a_warn("CHAL", "incorrect-tag", A_END);
 124     goto fail;
 125   }
 126   if (seq_check(&iseq, seq, "CHAL")) goto fail;
 127   T( trace(T_CHAL, "chal: challenge ok"); )
 128   return (0);
 129
 130 fail:
 131   buf_break(b);
 132   return (-1);
 133 }
 134
 135 /*----- That's all, folks -------------------------------------------------*/