gl/lib/randread.c

   1 /* Generate buffers of random data.
   2
   3    Copyright (C) 2006, 2008-2010 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 #include <config.h>
  21
  22 #include "randread.h"
  23
  24 #include <errno.h>
  25 #include <error.h>
  26 #include <exitfail.h>
  27 #include <quotearg.h>
  28 #include <stdbool.h>
  29 #include <stdint.h>
  30 #include <stdio.h>
  31 #include <stdlib.h>
  32 #include <string.h>
  33
  34 #include "gettext.h"
  35 #define _(msgid) gettext (msgid)
  36
  37 #include "rand-isaac.h"
  38 #include "stdio-safer.h"
  39 #include "unlocked-io.h"
  40 #include "xalloc.h"
  41
  42 #ifndef __attribute__
  43 # if __GNUC__ < 2 || (__GNUC__ == 2 && __GNUC_MINOR__ < 8)
  44 #  define __attribute__(x) /* empty */
  45 # endif
  46 #endif
  47
  48 #ifndef ATTRIBUTE_NORETURN
  49 # define ATTRIBUTE_NORETURN __attribute__ ((__noreturn__))
  50 #endif
  51
  52 #ifndef MIN
  53 # define MIN(a, b) ((a) < (b) ? (a) : (b))
  54 #endif
  55
  56 #if _STRING_ARCH_unaligned
  57 # define ALIGNED_POINTER(ptr, type) true
  58 #else
  59 # define alignof(type) offsetof (struct { char c; type x; }, x)
  60 # define ALIGNED_POINTER(ptr, type) ((size_t) (ptr) % alignof (type) == 0)
  61 #endif
  62
  63 /* The maximum buffer size used for reads of random data.  Using the
  64    value 2 * ISAAC_BYTES makes this the largest power of two that
  65    would not otherwise cause struct randread_source to grow.  */
  66 #define RANDREAD_BUFFER_SIZE (2 * ISAAC_BYTES)
  67
  68 /* A source of random data for generating random buffers.  */
  69 struct randread_source
  70 {
  71   /* Stream to read random bytes from.  If null, the current
  72      implementation uses an internal PRNG (ISAAC).  */
  73   FILE *source;
  74
  75   /* Function to call, and its argument, if there is an input error or
  76      end of file when reading from the stream; errno is nonzero if
  77      there was an error.  If this function returns, it should fix the
  78      problem before returning.  The default handler assumes that
  79      handler_arg is the file name of the source.  */
  80   void (*handler) (void const *);
  81   void const *handler_arg;
  82
  83   /* The buffer for SOURCE.  It's kept here to simplify storage
  84      allocation and to make it easier to clear out buffered random
  85      data.  */
  86   union
  87   {
  88     /* The stream buffer, if SOURCE is not null.  */
  89     char c[RANDREAD_BUFFER_SIZE];
  90
  91     /* The buffered ISAAC pseudorandom buffer, if SOURCE is null.  */
  92     struct isaac
  93     {
  94       /* The number of bytes that are buffered at the end of data.b.  */
  95       size_t buffered;
  96
  97       /* State of the ISAAC generator.  */
  98       struct isaac_state state;
  99
 100       /* Up to a buffer's worth of pseudorandom data.  */
 101       union
 102       {
 103         uint32_t w[ISAAC_WORDS];
 104         unsigned char b[ISAAC_BYTES];
 105       } data;
 106     } isaac;
 107   } buf;
 108 };
 109
 110
 111 /* The default error handler.  */
 112
 113 static void ATTRIBUTE_NORETURN
 114 randread_error (void const *file_name)
 115 {
 116   if (file_name)
 117     error (exit_failure, errno,
 118            _(errno == 0 ? "%s: end of file" : "%s: read error"),
 119            quotearg_colon (file_name));
 120   abort ();
 121 }
 122
 123 /* Simply return a new randread_source object with the default error
 124    handler.  */
 125
 126 static struct randread_source *
 127 simple_new (FILE *source, void const *handler_arg)
 128 {
 129   struct randread_source *s = xmalloc (sizeof *s);
 130   s->source = source;
 131   s->handler = randread_error;
 132   s->handler_arg = handler_arg;
 133   return s;
 134 }
 135
 136 /* Create and initialize a random data source from NAME, or use a
 137    reasonable default source if NAME is null.  BYTES_BOUND is an upper
 138    bound on the number of bytes that will be needed.  If zero, it is a
 139    hard bound; otherwise it is just an estimate.
 140
 141    If NAME is not null, NAME is saved for use as the argument of the
 142    default handler.  Unless a non-default handler is used, NAME's
 143    lifetime should be at least that of the returned value.
 144
 145    Return NULL (setting errno) on failure.  */
 146
 147 struct randread_source *
 148 randread_new (char const *name, size_t bytes_bound)
 149 {
 150   if (bytes_bound == 0)
 151     return simple_new (NULL, NULL);
 152   else
 153     {
 154       FILE *source = NULL;
 155       struct randread_source *s;
 156
 157       if (name)
 158         if (! (source = fopen_safer (name, "rb")))
 159           return NULL;
 160
 161       s = simple_new (source, name);
 162
 163       if (source)
 164         setvbuf (source, s->buf.c, _IOFBF, MIN (sizeof s->buf.c, bytes_bound));
 165       else
 166         {
 167           s->buf.isaac.buffered = 0;
 168           isaac_seed (&s->buf.isaac.state);
 169         }
 170
 171       return s;
 172     }
 173 }
 174
 175
 176 /* Set S's handler and its argument.  HANDLER (HANDLER_ARG) is called
 177    when there is a read error or end of file from the random data
 178    source; errno is nonzero if there was an error.  If HANDLER
 179    returns, it should fix the problem before returning.  The default
 180    handler assumes that handler_arg is the file name of the source; it
 181    does not return.  */
 182
 183 void
 184 randread_set_handler (struct randread_source *s, void (*handler) (void const *))
 185 {
 186   s->handler = handler;
 187 }
 188
 189 void
 190 randread_set_handler_arg (struct randread_source *s, void const *handler_arg)
 191 {
 192   s->handler_arg = handler_arg;
 193 }
 194
 195
 196 /* Place SIZE random bytes into the buffer beginning at P, using
 197    the stream in S.  */
 198
 199 static void
 200 readsource (struct randread_source *s, unsigned char *p, size_t size)
 201 {
 202   while (true)
 203     {
 204       size_t inbytes = fread (p, sizeof *p, size, s->source);
 205       int fread_errno = errno;
 206       p += inbytes;
 207       size -= inbytes;
 208       if (size == 0)
 209         break;
 210       errno = (ferror (s->source) ? fread_errno : 0);
 211       s->handler (s->handler_arg);
 212     }
 213 }
 214
 215
 216 /* Place SIZE pseudorandom bytes into the buffer beginning at P, using
 217    the buffered ISAAC generator in ISAAC.  */
 218
 219 static void
 220 readisaac (struct isaac *isaac, unsigned char *p, size_t size)
 221 {
 222   size_t inbytes = isaac->buffered;
 223
 224   while (true)
 225     {
 226       if (size <= inbytes)
 227         {
 228           memcpy (p, isaac->data.b + ISAAC_BYTES - inbytes, size);
 229           isaac->buffered = inbytes - size;
 230           return;
 231         }
 232
 233       memcpy (p, isaac->data.b + ISAAC_BYTES - inbytes, inbytes);
 234       p += inbytes;
 235       size -= inbytes;
 236
 237       /* If P is aligned, write to *P directly to avoid the overhead
 238          of copying from the buffer.  */
 239       if (ALIGNED_POINTER (p, uint32_t))
 240         {
 241           uint32_t *wp = (uint32_t *) p;
 242           while (ISAAC_BYTES <= size)
 243             {
 244               isaac_refill (&isaac->state, wp);
 245               wp += ISAAC_WORDS;
 246               size -= ISAAC_BYTES;
 247               if (size == 0)
 248                 {
 249                   isaac->buffered = 0;
 250                   return;
 251                 }
 252             }
 253           p = (unsigned char *) wp;
 254         }
 255
 256       isaac_refill (&isaac->state, isaac->data.w);
 257       inbytes = ISAAC_BYTES;
 258     }
 259 }
 260
 261
 262 /* Consume random data from *S to generate a random buffer BUF of size
 263    SIZE.  */
 264
 265 void
 266 randread (struct randread_source *s, void *buf, size_t size)
 267 {
 268   if (s->source)
 269     readsource (s, buf, size);
 270   else
 271     readisaac (&s->buf.isaac, buf, size);
 272 }
 273
 274
 275 /* Clear *S so that it no longer contains undelivered random data, and
 276    deallocate any system resources associated with *S.  Return 0 if
 277    successful, a negative number (setting errno) if not (this is rare,
 278    but can occur in theory if there is an input error).  */
 279
 280 int
 281 randread_free (struct randread_source *s)
 282 {
 283   FILE *source = s->source;
 284   memset (s, 0, sizeof *s);
 285   free (s);
 286   return (source ? fclose (source) : 0);
 287 }