mdw@git.distorted.org.uk Git - catacomb/blob - symm/latinpoly.c

   1 /* -*-c-*-
   2  *
   3  * AEAD schemes based on Salsa20/ChaCha and Poly1305
   4  *
   5  * (c) 2018 Straylight/Edgeware
   6  */
   7
   8 /*----- Licensing notice --------------------------------------------------*
   9  *
  10  * This file is part of Catacomb.
  11  *
  12  * Catacomb is free software: you can redistribute it and/or modify it
  13  * under the terms of the GNU Library General Public License as published
  14  * by the Free Software Foundation; either version 2 of the License, or
  15  * (at your option) any later version.
  16  *
  17  * Catacomb is distributed in the hope that it will be useful, but
  18  * WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  20  * Library General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU Library General Public
  23  * License along with Catacomb.  If not, write to the Free Software
  24  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
  25  * USA.
  26  */
  27
  28 /*----- Header files ------------------------------------------------------*/
  29
  30 #include "config.h"
  31
  32 #include <mLib/bits.h>
  33 #include <mLib/buf.h>
  34
  35 #include "gaead.h"
  36 #include "keysz.h"
  37 #include "latinpoly-def.h"
  38
  39 #include "poly1305.h"
  40 #include "salsa20.h"
  41
  42 /*----- Common definitions ------------------------------------------------*/
  43
  44 const octet
  45   latinpoly_noncesz[] = { KSZ_SET, SALSA20_NONCESZ, SALSA20_IETF_NONCESZ,
  46                           XSALSA20_NONCESZ, 0 },
  47   latinpoly_tagsz[] = { KSZ_SET, POLY1305_TAGSZ, 0 };
  48
  49 /* AAD handling. */
  50
  51 void latinpoly_aadhash(gaead_aad *a, const void *h, size_t hsz)
  52 {
  53   latinpoly_aad *aad = (latinpoly_aad *)a;
  54   poly1305_hash(&aad->poly, h, hsz);
  55 }
  56
  57 void latinpoly_aaddestroy(gaead_aad *a) { ; }
  58
  59 /* --- @latinpoly_tag@ --- *
  60  *
  61  * Arguments:   @const poly1305_ctx *aad@ = Poly1305 context hashing AAD
  62  *              @poly1305_ctx *ct@ = Poly1305 context hashing ciphertext
  63  *              @void *tag@ = where to write the tag
  64  *
  65  * Returns:     ---
  66  *
  67  * Use:         Completes a Latin-dance-Poly1305 tag, combining the AAD and
  68  *              ciphertext hashes, appending their lengths, and writing the
  69  *              final masked hash to @tag@.  The @ct@ context is clobbered.
  70  */
  71
  72 /* Write the length of data pushed through Poly1305 as a 64-bit integer. */
  73 static void putlen(octet *p, const poly1305_ctx *poly)
  74 {
  75   uint32 lo = U32((poly->count << 4) | poly->nbuf),
  76     hi = U32(poly->count >> 28);
  77   STORE32_L(p + 0, lo); STORE32_L(p + 4, hi);
  78 }
  79
  80 void latinpoly_tag(const poly1305_ctx *aad, poly1305_ctx *ct, void *tag)
  81 {
  82   octet b[16];
  83   poly1305_ctx t;
  84
  85   putlen(b + 8, ct); poly1305_flushzero(ct);
  86   if (!aad) memset(b, 0, 8);
  87   else {
  88     putlen(b + 0, aad);
  89     t = *aad; poly1305_flushzero(&t); poly1305_concat(ct, &t, ct);
  90   }
  91   poly1305_hash(ct, b, 16); poly1305_done(ct, tag);
  92 }
  93
  94 /*----- That's all, folks -------------------------------------------------*/