bsd/dev/random/randomdev.c

   1 /*
   2  * Copyright (c) 1999-2009 Apple, Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. The rights granted to you under the License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
  12  * circumvent, violate, or enable the circumvention or violation of, any
  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
  19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  23  * Please see the License for the specific language governing rights and
  24  * limitations under the License.
  25  *
  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  */
  28
  29
  30 #include <sys/param.h>
  31 #include <sys/systm.h>
  32 #include <sys/proc.h>
  33 #include <sys/errno.h>
  34 #include <sys/ioctl.h>
  35 #include <sys/conf.h>
  36 #include <sys/fcntl.h>
  37 #include <string.h>
  38 #include <miscfs/devfs/devfs.h>
  39 #include <kern/locks.h>
  40 #include <kern/clock.h>
  41 #include <sys/time.h>
  42 #include <sys/malloc.h>
  43 #include <sys/uio_internal.h>
  44
  45 #include <dev/random/randomdev.h>
  46
  47 #include <libkern/OSByteOrder.h>
  48 #include <libkern/OSAtomic.h>
  49
  50 #include <mach/mach_time.h>
  51
  52 #define RANDOM_MAJOR  -1 /* let the kernel pick the device number */
  53 #define RANDOM_MINOR   0
  54 #define URANDOM_MINOR  1
  55
  56 d_ioctl_t       random_ioctl;
  57
  58 /*
  59  * A struct describing which functions will get invoked for certain
  60  * actions.
  61  */
  62 static struct cdevsw random_cdevsw =
  63 {
  64         random_open,            /* open */
  65         random_close,           /* close */
  66         random_read,            /* read */
  67         random_write,           /* write */
  68         random_ioctl,           /* ioctl */
  69         (stop_fcn_t *)nulldev, /* stop */
  70         (reset_fcn_t *)nulldev, /* reset */
  71         NULL,                           /* tty's */
  72         eno_select,                     /* select */
  73         eno_mmap,                       /* mmap */
  74         eno_strat,                      /* strategy */
  75         eno_getc,                       /* getc */
  76         eno_putc,                       /* putc */
  77         0                                       /* type */
  78 };
  79
  80
  81 /*
  82  * Called to initialize our device,
  83  * and to register ourselves with devfs
  84  */
  85 void
  86 random_init(void)
  87 {
  88         int ret;
  89
  90         ret = cdevsw_add(RANDOM_MAJOR, &random_cdevsw);
  91         if (ret < 0) {
  92                 panic("random_init: failed to allocate a major number!");
  93         }
  94
  95         devfs_make_node(makedev (ret, RANDOM_MINOR), DEVFS_CHAR,
  96                 UID_ROOT, GID_WHEEL, 0666, "random", 0);
  97
  98         /*
  99          * also make urandom
 100          * (which is exactly the same thing in our context)
 101          */
 102         devfs_make_node(makedev (ret, URANDOM_MINOR), DEVFS_CHAR,
 103                 UID_ROOT, GID_WHEEL, 0666, "urandom", 0);
 104
 105 }
 106
 107 int
 108 random_ioctl(   __unused dev_t dev, u_long cmd, __unused caddr_t data,
 109                                 __unused int flag, __unused struct proc *p  )
 110 {
 111         switch (cmd) {
 112         case FIONBIO:
 113         case FIOASYNC:
 114                 break;
 115         default:
 116                 return ENODEV;
 117         }
 118
 119         return (0);
 120 }
 121
 122 /*
 123  * Open the device.  Make sure init happened, and make sure the caller is
 124  * authorized.
 125  */
 126
 127 int
 128 random_open(__unused dev_t dev, int flags, __unused int devtype, __unused struct proc *p)
 129 {
 130         /*
 131          * if we are being opened for write,
 132          * make sure that we have privledges do so
 133          */
 134         if (flags & FWRITE) {
 135                 if (securelevel >= 2)
 136                         return (EPERM);
 137 #ifndef __APPLE__
 138                 if ((securelevel >= 1) && proc_suser(p))
 139                         return (EPERM);
 140 #endif  /* !__APPLE__ */
 141         }
 142
 143         return (0);
 144 }
 145
 146
 147 /*
 148  * close the device.
 149  */
 150
 151 int
 152 random_close(__unused dev_t dev, __unused int flags, __unused int mode, __unused struct proc *p)
 153 {
 154         return (0);
 155 }
 156
 157
 158 /*
 159  * Get entropic data from the Security Server, and use it to reseed the
 160  * prng.
 161  */
 162 int
 163 random_write (dev_t dev, struct uio *uio, __unused int ioflag)
 164 {
 165     int retCode = 0;
 166     char rdBuffer[256];
 167
 168     if (minor(dev) != RANDOM_MINOR)
 169         return EPERM;
 170
 171     /* Security server is sending us entropy */
 172
 173     while (uio_resid(uio) > 0 && retCode == 0) {
 174         /* get the user's data */
 175         int bytesToInput = MIN(uio_resid(uio),
 176                                (user_ssize_t) sizeof(rdBuffer));
 177         retCode = uiomove(rdBuffer, bytesToInput, uio);
 178         if (retCode != 0)
 179             break;
 180         retCode = write_random(rdBuffer, bytesToInput);
 181         if (retCode != 0)
 182             break;
 183     }
 184
 185     return retCode;
 186 }
 187
 188 /*
 189  * return data to the caller.  Results unpredictable.
 190  */
 191 int
 192 random_read(__unused dev_t dev, struct uio *uio, __unused int ioflag)
 193 {
 194         int retCode = 0;
 195         char buffer[512];
 196
 197         user_ssize_t bytes_remaining = uio_resid(uio);
 198         while (bytes_remaining > 0 && retCode == 0) {
 199                 int bytesToRead = MIN(bytes_remaining,
 200                                       (user_ssize_t) sizeof(buffer));
 201                 read_random(buffer, bytesToRead);
 202
 203                 retCode = uiomove(buffer, bytesToRead, uio);
 204                 if (retCode != 0)
 205                         break;
 206
 207                 bytes_remaining = uio_resid(uio);
 208         }
 209
 210         return retCode;
 211 }
 212
 213 /*
 214  * Return an u_int32_t pseudo-random number.
 215  */
 216 u_int32_t
 217 RandomULong(void)
 218 {
 219         u_int32_t buf;
 220         read_random(&buf, sizeof (buf));
 221         return (buf);
 222 }
 223