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

   1 /* -*-c-*-
   2  *
   3  * $Id: noise.h,v 1.6 2004/04/08 01:36:15 mdw Exp $
   4  *
   5  * Acquisition of environmental noise (Unix-specific)
   6  *
   7  * (c) 1998 Straylight/Edgeware
   8  */
   9
  10 /*----- Licensing notice --------------------------------------------------*
  11  *
  12  * This file is part of Catacomb.
  13  *
  14  * Catacomb is free software; you can redistribute it and/or modify
  15  * it under the terms of the GNU Library General Public License as
  16  * published by the Free Software Foundation; either version 2 of the
  17  * License, or (at your option) any later version.
  18  *
  19  * Catacomb is distributed in the hope that it will be useful,
  20  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22  * GNU Library General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU Library General Public
  25  * License along with Catacomb; if not, write to the Free
  26  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  27  * MA 02111-1307, USA.
  28  */
  29
  30 #ifndef CATACOMB_NOISE_H
  31 #define CATACOMB_NOISE_H
  32
  33 #ifdef __cplusplus
  34   extern "C" {
  35 #endif
  36
  37 /*----- Header files ------------------------------------------------------*/
  38
  39 #include <sys/types.h>
  40
  41 #ifndef CATACOMB_RAND_H
  42 #  include "rand.h"
  43 #endif
  44
  45 /*----- Noise source definition -------------------------------------------*/
  46
  47 extern const rand_source noise_source;
  48
  49 /*----- Magic numbers -----------------------------------------------------*/
  50
  51 #define NOISE_NOSETUID ((uid_t)-1)
  52 #define NOISE_NOSETGID ((gid_t)-1)
  53
  54 /*----- Functions provided ------------------------------------------------*/
  55
  56 /* --- @noise_timer@ --- *
  57  *
  58  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
  59  *
  60  * Returns:     Nonzero if some randomness was contributed.
  61  *
  62  * Use:         Contributes the current time to the randomness pool.
  63  *              A guess at the number of useful bits contributed is made,
  64  *              based on first and second order bit differences.  This isn't
  65  *              ever-so reliable, but it's better than nothing.
  66  */
  67
  68 extern int noise_timer(rand_pool */*r*/);
  69
  70 /* --- @noise_devrandom@ --- *
  71  *
  72  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
  73  *
  74  * Returns:     Nonzero if some randomness was contributed.
  75  *
  76  * Use:         Attempts to obtain some randomness from the system entropy
  77  *              pool.  All bits from the device are assumed to be good.
  78  */
  79
  80 extern int noise_devrandom(rand_pool */*r*/);
  81
  82 /* --- @noise_setid@ --- *
  83  *
  84  * Arguments:   @uid_t uid@ = uid to set
  85  *              @gid_t gid@ = gid to set
  86  *
  87  * Returns:     ---
  88  *
  89  * Use:         Sets the user and group ids to be used by @noise_filter@
  90  *              when running child processes.  This is useful to avoid
  91  *              giving shell commands (even carefully written ones) undue
  92  *              privileges.  This interface is Unix-specific.
  93  */
  94
  95 extern void noise_setid(uid_t /*uid*/, gid_t /*gid*/);
  96
  97 /* --- @noise_filter@ --- *
  98  *
  99  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
 100  *              @int good@ = number of good bits per 1024 bits
 101  *              @const char *c@ = shell command to run
 102  *
 103  * Returns:     Nonzero if some randomness was contributed.
 104  *
 105  * Use:         Attempts to execute a shell command, and dump it into the
 106  *              randomness pool.  A very rough estimate of the number of
 107  *              good bits is made, based on the size of the command's output.
 108  *              This function calls @waitpid@, so be careful.  Before execing
 109  *              the command, the process uid and gid are set to the values
 110  *              given to @noise_setid@, and an attempt is made to reset the
 111  *              list of supplementary groups.  The environment passed to
 112  *              the command has been severly lobotimized.  If the command
 113  *              fails to complete within a short time period, it is killed.
 114  *              Paranoid use of close-on-exec flags for file descriptors is
 115  *              recommended.
 116  *
 117  *              This interface is Unix-specific.
 118  */
 119
 120 extern int noise_filter(rand_pool */*r*/, int /*good*/, const char */*c*/);
 121
 122 /* --- @noise_freewheel@ --- *
 123  *
 124  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
 125  *
 126  * Returns:     Nonzero if some randomness was contributed.
 127  *
 128  * Use:         Runs a free counter for a short while as a desparate attempt
 129  *              to get randomness from somewhere.  This is actually quite
 130  *              effective.
 131  */
 132
 133 int noise_freewheel(rand_pool */*r*/);
 134
 135 /* --- @noise_enquire@ --- *
 136  *
 137  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
 138  *
 139  * Returns:     Nonzero if some randomness was contributed.
 140  *
 141  * Use:         Runs some shell commands to enquire about the prevailing
 142  *              environment.  This can gather quite a lot of low-quality
 143  *              entropy.
 144  */
 145
 146 extern int noise_enquire(rand_pool */*r*/);
 147
 148 /* --- @noise_acquire@ --- *
 149  *
 150  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
 151  *
 152  * Returns:     ---
 153  *
 154  * Use:         Acquires some randomness from somewhere.
 155  */
 156
 157 extern void noise_acquire(rand_pool */*r*/);
 158
 159 /*----- That's all, folks -------------------------------------------------*/
 160
 161 #ifdef __cplusplus
 162   }
 163 #endif
 164
 165 #endif