stdlib/arc4random.h

   1 /* Arc4random definition used on TLS.
   2    Copyright (C) 2022 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #ifndef _CHACHA20_H
  20 #define _CHACHA20_H
  21
  22 #include <stddef.h>
  23 #include <stdint.h>
  24
  25 /* Internal ChaCha20 state.  */
  26 #define CHACHA20_STATE_LEN      16
  27 #define CHACHA20_BLOCK_SIZE     64
  28
  29 /* Maximum number bytes until reseed (16 MB).  */
  30 #define CHACHA20_RESEED_SIZE    (16 * 1024 * 1024)
  31
  32 /* Internal arc4random buffer, used on each feedback step so offer some
  33    backtracking protection and to allow better used of vectorized
  34    chacha20 implementations.  */
  35 #define CHACHA20_BUFSIZE        (8 * CHACHA20_BLOCK_SIZE)
  36
  37 _Static_assert (CHACHA20_BUFSIZE >= CHACHA20_BLOCK_SIZE + CHACHA20_BLOCK_SIZE,
  38                 "CHACHA20_BUFSIZE < CHACHA20_BLOCK_SIZE + CHACHA20_BLOCK_SIZE");
  39
  40 struct arc4random_state_t
  41 {
  42   uint32_t ctx[CHACHA20_STATE_LEN];
  43   size_t have;
  44   size_t count;
  45   uint8_t buf[CHACHA20_BUFSIZE];
  46 };
  47
  48 #endif