git.distorted.org.uk Git - u/mdw/catacomb/blob - rand/noise.h

   1 /* -*-c-*-
   2  *
   3  * Acquisition of environmental noise (Unix-specific)
   4  *
   5  * (c) 1998 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
  13  * it under the terms of the GNU Library General Public License as
  14  * published by the Free Software Foundation; either version 2 of the
  15  * License, or (at your option) any later version.
  16  *
  17  * Catacomb is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU 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
  24  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  25  * MA 02111-1307, USA.
  26  */
  27
  28 #ifndef CATACOMB_NOISE_H
  29 #define CATACOMB_NOISE_H
  30
  31 #ifdef __cplusplus
  32   extern "C" {
  33 #endif
  34
  35 /*----- Header files ------------------------------------------------------*/
  36
  37 #include <sys/types.h>
  38
  39 #ifndef CATACOMB_RAND_H
  40 #  include "rand.h"
  41 #endif
  42
  43 /*----- Noise source definition -------------------------------------------*/
  44
  45 extern const rand_source noise_source;
  46
  47 /*----- Magic numbers -----------------------------------------------------*/
  48
  49 #define NOISE_NOSETUID ((uid_t)-1)
  50 #define NOISE_NOSETGID ((gid_t)-1)
  51
  52 /*----- Functions provided ------------------------------------------------*/
  53
  54 /* --- @noise_timer@ --- *
  55  *
  56  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
  57  *
  58  * Returns:     Nonzero if some randomness was contributed.
  59  *
  60  * Use:         Contributes the current time to the randomness pool.
  61  *              A guess at the number of useful bits contributed is made,
  62  *              based on first and second order bit differences.  This isn't
  63  *              ever-so reliable, but it's better than nothing.
  64  */
  65
  66 extern int noise_timer(rand_pool */*r*/);
  67
  68 /* --- @noise_devrandom@ --- *
  69  *
  70  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
  71  *
  72  * Returns:     Nonzero if some randomness was contributed.
  73  *
  74  * Use:         Attempts to obtain some randomness from the system entropy
  75  *              pool.  All bits from the device are assumed to be good.
  76  */
  77
  78 extern int noise_devrandom(rand_pool */*r*/);
  79
  80 /* --- @noise_setid@ --- *
  81  *
  82  * Arguments:   @uid_t uid@ = uid to set
  83  *              @gid_t gid@ = gid to set
  84  *
  85  * Returns:     ---
  86  *
  87  * Use:         Sets the user and group ids to be used by @noise_filter@
  88  *              when running child processes.  This is useful to avoid
  89  *              giving shell commands (even carefully written ones) undue
  90  *              privileges.  This interface is Unix-specific.
  91  */
  92
  93 extern void noise_setid(uid_t /*uid*/, gid_t /*gid*/);
  94
  95 /* --- @noise_filter@ --- *
  96  *
  97  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
  98  *              @int good@ = number of good bits per 1024 bits
  99  *              @const char *c@ = shell command to run
 100  *
 101  * Returns:     Nonzero if some randomness was contributed.
 102  *
 103  * Use:         Attempts to execute a shell command, and dump it into the
 104  *              randomness pool.  A very rough estimate of the number of
 105  *              good bits is made, based on the size of the command's output.
 106  *              This function calls @waitpid@, so be careful.  Before execing
 107  *              the command, the process uid and gid are set to the values
 108  *              given to @noise_setid@, and an attempt is made to reset the
 109  *              list of supplementary groups.  The environment passed to
 110  *              the command has been severly lobotimized.  If the command
 111  *              fails to complete within a short time period, it is killed.
 112  *              Paranoid use of close-on-exec flags for file descriptors is
 113  *              recommended.
 114  *
 115  *              This interface is Unix-specific.
 116  */
 117
 118 extern int noise_filter(rand_pool */*r*/, int /*good*/, const char */*c*/);
 119
 120 /* --- @noise_freewheel@ --- *
 121  *
 122  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
 123  *
 124  * Returns:     Nonzero if some randomness was contributed.
 125  *
 126  * Use:         Runs a free counter for a short while as a desparate attempt
 127  *              to get randomness from somewhere.  This is actually quite
 128  *              effective.
 129  */
 130
 131 int noise_freewheel(rand_pool */*r*/);
 132
 133 /* --- @noise_enquire@ --- *
 134  *
 135  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
 136  *
 137  * Returns:     Nonzero if some randomness was contributed.
 138  *
 139  * Use:         Runs some shell commands to enquire about the prevailing
 140  *              environment.  This can gather quite a lot of low-quality
 141  *              entropy.
 142  */
 143
 144 extern int noise_enquire(rand_pool */*r*/);
 145
 146 /* --- @noise_acquire@ --- *
 147  *
 148  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
 149  *
 150  * Returns:     ---
 151  *
 152  * Use:         Acquires some randomness from somewhere.
 153  */
 154
 155 extern void noise_acquire(rand_pool */*r*/);
 156
 157 /*----- That's all, folks -------------------------------------------------*/
 158
 159 #ifdef __cplusplus
 160   }
 161 #endif
 162
 163 #endif