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

   1 /* -*-c-*-
   2  *
   3  * Generic authenticated encryption interface
   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 "gaead.h"
  31
  32 /*----- Main code ---------------------------------------------------------*/
  33
  34 /* --- @gaead_encrypt@ --- *
  35  *
  36  * Arguments:   @const gaead_key *k@ = the AEAD key, already prepared
  37  *              @const void *n@, @size_t nsz@ = nonce
  38  *              @const void *h@, @size_t hsz@ = additional `header' data
  39  *              @const void *m@, @size_t msz@ = message input
  40  *              @void *c@, @size_t *csz_input@ = ciphertext output
  41  *              @void *t@, @size_t tsz@ = tag output
  42  *
  43  * Returns:     Zero on success, @-1@ if the output buffer is too small.
  44  *
  45  * Use:         Encrypts and authenticates a message in a single operation.
  46  *              This just saves a bunch of messing about with the various
  47  *              @gaead_...@ objects.
  48  *
  49  *              On entry, @*csz_inout@ should be the capacity of the
  50  *              ciphertext buffer; on exit, it will be updated with the
  51  *              actual size of ciphertext produced.  The function will not
  52  *              fail if @*csz_inout >= msz + k->c->ohd@.
  53  */
  54
  55 int gaead_encrypt(const gaead_key *k, const void *n, size_t nsz,
  56                   const void *h, size_t hsz,
  57                   const void *m, size_t msz,
  58                   void *c, size_t *csz_inout,
  59                   void *t, size_t tsz)
  60 {
  61   gaead_enc *e = 0;
  62   gaead_aad *a = 0;
  63   buf b;
  64   int rc;
  65
  66   buf_init(&b, c, *csz_inout);
  67   e = GAEAD_ENC(k, n, nsz, hsz, msz, tsz); if (!e) { rc = -1; goto end; }
  68   if (hsz) { a = GAEAD_AAD(e); GAEAD_HASH(a, h, hsz); }
  69   rc = GAEAD_ENCRYPT(e, m, msz, &b); if (rc) goto end;
  70   rc = GAEAD_DONE(e, a, &b, t, tsz);
  71 end:
  72   if (rc >= 0) *csz_inout = BLEN(&b);
  73   if (e) GAEAD_DESTROY(e);
  74   if (a) GAEAD_DESTROY(a);
  75   return (rc);
  76 }
  77
  78 /* --- @gaead_decrypt@ --- *
  79  *
  80  * Arguments:   @const gaead_key *k@ = the AEAD key, already prepared
  81  *              @const void *n@, @size_t nsz@ = nonce
  82  *              @const void *h@, @size_t hsz@ = additional `header' data
  83  *              @const void *c@, @size_t csz@ = ciphertext input
  84  *              @void *m@, @size_t *msz_inout@ = message output
  85  *              @const void *t@, @size_t tsz@ = tag input
  86  *
  87  * Returns:     @+1@ if everything is good; zero for authentication failure,
  88  *              @-1@ for other problems.
  89  *
  90  * Use:         Decrypts and verifies a message in a single operation.
  91  *              This just saves a bunch of messing about with the various
  92  *              @gaead_...@ objects.
  93  *
  94  *              On entry, @*msz_inout@ should be the capacity of the
  95  *              message buffer; on exit, it will be updated with the
  96  *              actual size of message produced.  The function will not
  97  *              fail if @*msz_inout >= csz@.
  98  */
  99
 100 int gaead_decrypt(const gaead_key *k, const void *n, size_t nsz,
 101                   const void *h, size_t hsz,
 102                   const void *c, size_t csz,
 103                   void *m, size_t *msz_inout,
 104                   const void *t, size_t tsz)
 105 {
 106   gaead_dec *d = 0;
 107   gaead_aad *a = 0;
 108   buf b;
 109   int rc;
 110
 111   buf_init(&b, m, *msz_inout);
 112   d = GAEAD_DEC(k, n, nsz, hsz, csz, tsz); if (!d) { rc = -1; goto end; }
 113   if (hsz) { a = GAEAD_AAD(d); GAEAD_HASH(a, h, hsz); }
 114   rc = GAEAD_DECRYPT(d, c, csz, &b); if (rc) goto end;
 115   rc = GAEAD_DONE(d, a, &b, t, tsz);
 116 end:
 117   if (rc >= 0) *msz_inout = BLEN(&b);
 118   if (d) GAEAD_DESTROY(d);
 119   if (a) GAEAD_DESTROY(a);
 120   return (rc);
 121 }
 122
 123 /*----- That's all, folks -------------------------------------------------*/