lib/hcrypto/rand-unix.c

   1 /*
   2  * Copyright (c) 2006 Kungliga Tekniska Högskolan
   3  * (Royal Institute of Technology, Stockholm, Sweden).
   4  * All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  *
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  *
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  *
  17  * 3. Neither the name of the Institute nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  */
  33
  34 #include <config.h>
  35
  36 #include <stdio.h>
  37 #include <stdlib.h>
  38 #include <rand.h>
  39 #include <heim_threads.h>
  40
  41 #include <roken.h>
  42
  43 #include "randi.h"
  44
  45 static int random_fd = -1;
  46 static HEIMDAL_MUTEX random_mutex = HEIMDAL_MUTEX_INITIALIZER;
  47
  48 /*
  49  * Unix /dev/random
  50  */
  51
  52 static int
  53 get_device_fd(int flags)
  54 {
  55     static const char *rnd_devices[] = {
  56         "/dev/urandom",
  57         "/dev/random",
  58         "/dev/srandom",
  59         "/dev/arandom",
  60         NULL
  61     };
  62     const char **p;
  63
  64     for(p = rnd_devices; *p; p++) {
  65         int fd = open(*p, flags | O_NDELAY);
  66         if(fd >= 0) {
  67             rk_cloexec(fd);
  68             return fd;
  69         }
  70     }
  71     return -1;
  72 }
  73
  74 static void
  75 unix_seed(const void *indata, int size)
  76 {
  77     int fd;
  78
  79     if (size <= 0)
  80         return;
  81
  82     fd = get_device_fd(O_WRONLY);
  83     if (fd < 0)
  84         return;
  85
  86     write(fd, indata, size);
  87     close(fd);
  88
  89 }
  90
  91
  92 static int
  93 unix_bytes(unsigned char *outdata, int size)
  94 {
  95     ssize_t count;
  96     int once = 0;
  97
  98     if (size < 0)
  99         return 0;
 100     else if (size == 0)
 101         return 1;
 102
 103     HEIMDAL_MUTEX_lock(&random_mutex);
 104     if (random_fd == -1) {
 105     retry:
 106         random_fd = get_device_fd(O_RDONLY);
 107         if (random_fd < 0) {
 108             HEIMDAL_MUTEX_unlock(&random_mutex);
 109             return 0;
 110         }
 111     }
 112
 113     while (size > 0) {
 114         HEIMDAL_MUTEX_unlock(&random_mutex);
 115         count = read (random_fd, outdata, size);
 116         HEIMDAL_MUTEX_lock(&random_mutex);
 117         if (random_fd < 0) {
 118             if (errno == EINTR)
 119                 continue;
 120             else if (errno == EBADF && once++ == 0) {
 121                 close(random_fd);
 122                 random_fd = -1;
 123                 goto retry;
 124             }
 125             return 0;
 126         } else if (count <= 0) {
 127             HEIMDAL_MUTEX_unlock(&random_mutex);
 128             return 0;
 129         }
 130         outdata += count;
 131         size -= count;
 132     }
 133     HEIMDAL_MUTEX_unlock(&random_mutex);
 134
 135     return 1;
 136 }
 137
 138 static void
 139 unix_cleanup(void)
 140 {
 141 }
 142
 143 static void
 144 unix_add(const void *indata, int size, double entropi)
 145 {
 146     unix_seed(indata, size);
 147 }
 148
 149 static int
 150 unix_pseudorand(unsigned char *outdata, int size)
 151 {
 152     return unix_bytes(outdata, size);
 153 }
 154
 155 static int
 156 unix_status(void)
 157 {
 158     int fd;
 159
 160     fd = get_device_fd(O_RDONLY);
 161     if (fd < 0)
 162         return 0;
 163     close(fd);
 164
 165     return 1;
 166 }
 167
 168 const RAND_METHOD hc_rand_unix_method = {
 169     unix_seed,
 170     unix_bytes,
 171     unix_cleanup,
 172     unix_add,
 173     unix_pseudorand,
 174     unix_status
 175 };
 176
 177 const RAND_METHOD *
 178 RAND_unix_method(void)
 179 {
 180     return &hc_rand_unix_method;
 181 }