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   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 -------------------------------------------------*/