rngd_linux.c

   1 /*
   2  * rngd_linux.c -- Entropy sink for the Linux Kernel (/dev/random)
   3  *
   4  * Copyright (C) 2001 Philipp Rumpf
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin Street, Suite 500, Boston, MA  02110-1335  USA
  19  */
  20
  21 #define _GNU_SOURCE
  22
  23 #ifndef HAVE_CONFIG_H
  24 #error Invalid or missing autoconf build environment
  25 #endif
  26
  27 #include "rng-tools-config.h"
  28
  29 #include <unistd.h>
  30 #include <stdint.h>
  31 #include <stdlib.h>
  32 #include <stdio.h>
  33 #include <errno.h>
  34 #include <syslog.h>
  35 #include <sys/ioctl.h>
  36 #include <sys/poll.h>
  37 #include <sys/types.h>
  38 #include <sys/stat.h>
  39 #include <fcntl.h>
  40 #include <sys/time.h>
  41 #include <time.h>
  42 #include <linux/types.h>
  43 #include <linux/random.h>
  44 #include <string.h>
  45
  46 #include "rngd.h"
  47 #include "fips.h"
  48 #include "exits.h"
  49 #include "rngd_linux.h"
  50
  51 extern struct rng *rng_list;
  52
  53 /* Kernel output device */
  54 static int random_fd;
  55
  56 /*
  57  * Get the default watermark
  58  */
  59 int default_watermark(void)
  60 {
  61         char psbuf[64], *p;
  62         unsigned long ps;
  63         FILE *f;
  64         size_t l;
  65         unsigned int wm = 2048; /* Default guess */
  66
  67         f = fopen("/proc/sys/kernel/random/poolsize", "r");
  68         if (!f)
  69                 goto err;
  70         l = fread(psbuf, 1, sizeof psbuf, f);
  71         if (ferror(f) || !feof(f) || l == 0)
  72                 goto err;
  73         if (psbuf[l-1] != '\n')
  74                 goto err;
  75         psbuf[l-1] = '\0';
  76         ps = strtoul(psbuf, &p, 0);
  77         if (*p)
  78                 goto err;
  79
  80         wm = ps*3/4;
  81
  82 err:
  83         if (f)
  84                 fclose(f);
  85         return wm;
  86 }
  87
  88 /*
  89  * Initialize the interface to the Linux Kernel
  90  * entropy pool (through /dev/random)
  91  *
  92  * randomdev is the path to the random device
  93  */
  94 void init_kernel_rng(const char* randomdev)
  95 {
  96         FILE *f;
  97         int err;
  98
  99         random_fd = open(randomdev, O_RDWR);
 100         if (random_fd == -1) {
 101                 message(LOG_DAEMON|LOG_ERR, "can't open %s: %s",
 102                         randomdev, strerror(errno));
 103                 exit(EXIT_USAGE);
 104         }
 105
 106         f = fopen("/proc/sys/kernel/random/write_wakeup_threshold", "w");
 107         if (!f) {
 108                 err = 1;
 109         } else {
 110                 fprintf(f, "%u\n", arguments->fill_watermark);
 111                 /* Note | not || here... we always want to close the file */
 112                 err = ferror(f) | fclose(f);
 113         }
 114         if (err) {
 115                 message(LOG_DAEMON|LOG_WARNING,
 116                         "unable to adjust write_wakeup_threshold: %s",
 117                         strerror(errno));
 118         }
 119 }
 120
 121 void random_add_entropy(void *buf, size_t size)
 122 {
 123         struct {
 124                 int ent_count;
 125                 int size;
 126                 unsigned char data[size];
 127         } entropy;
 128
 129         entropy.ent_count = size * 8;
 130         entropy.size = size;
 131         memcpy(entropy.data, buf, size);
 132
 133         if (ioctl(random_fd, RNDADDENTROPY, &entropy) != 0) {
 134                 message(LOG_DAEMON|LOG_ERR, "RNDADDENTROPY failed: %s\n",
 135                         strerror(errno));
 136                 exit(1);
 137         }
 138 }
 139
 140 void random_sleep(void)
 141 {
 142         struct pollfd pfd = {
 143                 fd:     random_fd,
 144                 events: POLLOUT,
 145         };
 146
 147         poll(&pfd, 1, -1);
 148 }
 149
 150 void src_list_add(struct rng *ent_src)
 151 {
 152         if (rng_list) {
 153                 struct rng *iter;
 154
 155                 iter = rng_list;
 156                 while (iter->next) {
 157                         iter = iter->next;
 158                 }
 159                 iter->next = ent_src;
 160         } else {
 161                 rng_list = ent_src;
 162         }
 163 }