gl/lib/randread.c

   1 /* Generate buffers of random data.
   2
   3    Copyright (C) 2006-2012 Free Software Foundation, Inc.
   4
   5    This program is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation, either version 3 of the License, or
   8    (at your option) any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  17
  18 /* Written by Paul Eggert.  */
  19
  20 /* FIXME: Improve performance by adding support for the RDRAND machine
  21    instruction if available (e.g., Ivy Bridge processors).  */
  22
  23 #include <config.h>
  24
  25 #include "randread.h"
  26
  27 #include <errno.h>
  28 #include <error.h>
  29 #include <exitfail.h>
  30 #include <fcntl.h>
  31 #include <quotearg.h>
  32 #include <stdalign.h>
  33 #include <stdbool.h>
  34 #include <stdint.h>
  35 #include <stdio.h>
  36 #include <stdlib.h>
  37 #include <string.h>
  38 #include <sys/time.h>
  39 #include <unistd.h>
  40
  41 #include "gettext.h"
  42 #define _(msgid) gettext (msgid)
  43
  44 #include "rand-isaac.h"
  45 #include "stdio-safer.h"
  46 #include "unlocked-io.h"
  47 #include "xalloc.h"
  48
  49 #ifndef __attribute__
  50 # if __GNUC__ < 2 || (__GNUC__ == 2 && __GNUC_MINOR__ < 8)
  51 #  define __attribute__(x) /* empty */
  52 # endif
  53 #endif
  54
  55 #ifndef ATTRIBUTE_NORETURN
  56 # define ATTRIBUTE_NORETURN __attribute__ ((__noreturn__))
  57 #endif
  58
  59 #ifndef MIN
  60 # define MIN(a, b) ((a) < (b) ? (a) : (b))
  61 #endif
  62
  63 #if _STRING_ARCH_unaligned
  64 # define ALIGNED_POINTER(ptr, type) true
  65 #else
  66 # define ALIGNED_POINTER(ptr, type) ((size_t) (ptr) % alignof (type) == 0)
  67 #endif
  68
  69 #ifndef NAME_OF_NONCE_DEVICE
  70 # define NAME_OF_NONCE_DEVICE "/dev/urandom"
  71 #endif
  72
  73 /* The maximum buffer size used for reads of random data.  Using the
  74    value 2 * ISAAC_BYTES makes this the largest power of two that
  75    would not otherwise cause struct randread_source to grow.  */
  76 #define RANDREAD_BUFFER_SIZE (2 * ISAAC_BYTES)
  77
  78 /* A source of random data for generating random buffers.  */
  79 struct randread_source
  80 {
  81   /* Stream to read random bytes from.  If null, the current
  82      implementation uses an internal PRNG (ISAAC).  */
  83   FILE *source;
  84
  85   /* Function to call, and its argument, if there is an input error or
  86      end of file when reading from the stream; errno is nonzero if
  87      there was an error.  If this function returns, it should fix the
  88      problem before returning.  The default handler assumes that
  89      handler_arg is the file name of the source.  */
  90   void (*handler) (void const *);
  91   void const *handler_arg;
  92
  93   /* The buffer for SOURCE.  It's kept here to simplify storage
  94      allocation and to make it easier to clear out buffered random
  95      data.  */
  96   union
  97   {
  98     /* The stream buffer, if SOURCE is not null.  */
  99     char c[RANDREAD_BUFFER_SIZE];
 100
 101     /* The buffered ISAAC pseudorandom buffer, if SOURCE is null.  */
 102     struct isaac
 103     {
 104       /* The number of bytes that are buffered at the end of data.b.  */
 105       size_t buffered;
 106
 107       /* State of the ISAAC generator.  */
 108       struct isaac_state state;
 109
 110       /* Up to a buffer's worth of pseudorandom data.  */
 111       union
 112       {
 113         isaac_word w[ISAAC_WORDS];
 114         unsigned char b[ISAAC_BYTES];
 115       } data;
 116     } isaac;
 117   } buf;
 118 };
 119
 120
 121 /* The default error handler.  */
 122
 123 static void ATTRIBUTE_NORETURN
 124 randread_error (void const *file_name)
 125 {
 126   if (file_name)
 127     error (exit_failure, errno,
 128            _(errno == 0 ? "%s: end of file" : "%s: read error"),
 129            quotearg_colon (file_name));
 130   abort ();
 131 }
 132
 133 /* Simply return a new randread_source object with the default error
 134    handler.  */
 135
 136 static struct randread_source *
 137 simple_new (FILE *source, void const *handler_arg)
 138 {
 139   struct randread_source *s = xmalloc (sizeof *s);
 140   s->source = source;
 141   s->handler = randread_error;
 142   s->handler_arg = handler_arg;
 143   return s;
 144 }
 145
 146 /* Put a nonce value into BUFFER, with size BUFSIZE, but do not get
 147    more than BYTES_BOUND bytes' worth of random information from any
 148    nonce device.  */
 149
 150 static void
 151 get_nonce (void *buffer, size_t bufsize, size_t bytes_bound)
 152 {
 153   char *buf = buffer;
 154   ssize_t seeded = 0;
 155
 156   /* Get some data from FD if available.  */
 157   int fd = open (NAME_OF_NONCE_DEVICE, O_RDONLY | O_BINARY);
 158   if (0 <= fd)
 159     {
 160       seeded = read (fd, buf, MIN (bufsize, bytes_bound));
 161       if (seeded < 0)
 162         seeded = 0;
 163       close (fd);
 164     }
 165
 166   /* If there's no nonce device, use a poor approximation
 167      by getting the time of day, etc.  */
 168 #define ISAAC_SEED(type, initialize_v)                      \
 169   if (seeded < bufsize)                                     \
 170     {                                                       \
 171       type v;                                               \
 172       size_t nbytes = MIN (sizeof v, bufsize - seeded);     \
 173       initialize_v;                                         \
 174       memcpy (buf + seeded, &v, nbytes);                    \
 175       seeded += nbytes;                                     \
 176     }
 177   ISAAC_SEED (struct timeval, gettimeofday (&v, NULL));
 178   ISAAC_SEED (pid_t, v = getpid ());
 179   ISAAC_SEED (pid_t, v = getppid ());
 180   ISAAC_SEED (uid_t, v = getuid ());
 181   ISAAC_SEED (uid_t, v = getgid ());
 182
 183 #ifdef lint
 184   /* Normally we like having the extra randomness from uninitialized
 185      parts of BUFFER.  However, omit this randomness if we want to
 186      avoid false-positives from memory-checking debugging tools.  */
 187   memset (buf + seeded, 0, bufsize - seeded);
 188 #endif
 189 }
 190
 191
 192 /* Create and initialize a random data source from NAME, or use a
 193    reasonable default source if NAME is null.  BYTES_BOUND is an upper
 194    bound on the number of bytes that will be needed.  If zero, it is a
 195    hard bound; otherwise it is just an estimate.
 196
 197    If NAME is not null, NAME is saved for use as the argument of the
 198    default handler.  Unless a non-default handler is used, NAME's
 199    lifetime should be at least that of the returned value.
 200
 201    Return NULL (setting errno) on failure.  */
 202
 203 struct randread_source *
 204 randread_new (char const *name, size_t bytes_bound)
 205 {
 206   if (bytes_bound == 0)
 207     return simple_new (NULL, NULL);
 208   else
 209     {
 210       FILE *source = NULL;
 211       struct randread_source *s;
 212
 213       if (name)
 214         if (! (source = fopen_safer (name, "rb")))
 215           return NULL;
 216
 217       s = simple_new (source, name);
 218
 219       if (source)
 220         setvbuf (source, s->buf.c, _IOFBF, MIN (sizeof s->buf.c, bytes_bound));
 221       else
 222         {
 223           s->buf.isaac.buffered = 0;
 224           get_nonce (s->buf.isaac.state.m, sizeof s->buf.isaac.state.m,
 225                      bytes_bound);
 226           isaac_seed (&s->buf.isaac.state);
 227         }
 228
 229       return s;
 230     }
 231 }
 232
 233
 234 /* Set S's handler and its argument.  HANDLER (HANDLER_ARG) is called
 235    when there is a read error or end of file from the random data
 236    source; errno is nonzero if there was an error.  If HANDLER
 237    returns, it should fix the problem before returning.  The default
 238    handler assumes that handler_arg is the file name of the source; it
 239    does not return.  */
 240
 241 void
 242 randread_set_handler (struct randread_source *s, void (*handler) (void const *))
 243 {
 244   s->handler = handler;
 245 }
 246
 247 void
 248 randread_set_handler_arg (struct randread_source *s, void const *handler_arg)
 249 {
 250   s->handler_arg = handler_arg;
 251 }
 252
 253
 254 /* Place SIZE random bytes into the buffer beginning at P, using
 255    the stream in S.  */
 256
 257 static void
 258 readsource (struct randread_source *s, unsigned char *p, size_t size)
 259 {
 260   while (true)
 261     {
 262       size_t inbytes = fread (p, sizeof *p, size, s->source);
 263       int fread_errno = errno;
 264       p += inbytes;
 265       size -= inbytes;
 266       if (size == 0)
 267         break;
 268       errno = (ferror (s->source) ? fread_errno : 0);
 269       s->handler (s->handler_arg);
 270     }
 271 }
 272
 273
 274 /* Place SIZE pseudorandom bytes into the buffer beginning at P, using
 275    the buffered ISAAC generator in ISAAC.  */
 276
 277 static void
 278 readisaac (struct isaac *isaac, unsigned char *p, size_t size)
 279 {
 280   size_t inbytes = isaac->buffered;
 281
 282   while (true)
 283     {
 284       if (size <= inbytes)
 285         {
 286           memcpy (p, isaac->data.b + ISAAC_BYTES - inbytes, size);
 287           isaac->buffered = inbytes - size;
 288           return;
 289         }
 290
 291       memcpy (p, isaac->data.b + ISAAC_BYTES - inbytes, inbytes);
 292       p += inbytes;
 293       size -= inbytes;
 294
 295       /* If P is aligned, write to *P directly to avoid the overhead
 296          of copying from the buffer.  */
 297       if (ALIGNED_POINTER (p, isaac_word))
 298         {
 299           isaac_word *wp = (isaac_word *) p;
 300           while (ISAAC_BYTES <= size)
 301             {
 302               isaac_refill (&isaac->state, wp);
 303               wp += ISAAC_WORDS;
 304               size -= ISAAC_BYTES;
 305               if (size == 0)
 306                 {
 307                   isaac->buffered = 0;
 308                   return;
 309                 }
 310             }
 311           p = (unsigned char *) wp;
 312         }
 313
 314       isaac_refill (&isaac->state, isaac->data.w);
 315       inbytes = ISAAC_BYTES;
 316     }
 317 }
 318
 319
 320 /* Consume random data from *S to generate a random buffer BUF of size
 321    SIZE.  */
 322
 323 void
 324 randread (struct randread_source *s, void *buf, size_t size)
 325 {
 326   if (s->source)
 327     readsource (s, buf, size);
 328   else
 329     readisaac (&s->buf.isaac, buf, size);
 330 }
 331
 332
 333 /* Clear *S so that it no longer contains undelivered random data, and
 334    deallocate any system resources associated with *S.  Return 0 if
 335    successful, a negative number (setting errno) if not (this is rare,
 336    but can occur in theory if there is an input error).  */
 337
 338 int
 339 randread_free (struct randread_source *s)
 340 {
 341   FILE *source = s->source;
 342   memset (s, 0, sizeof *s);
 343   free (s);
 344   return (source ? fclose (source) : 0);
 345 }