Changeset 7f49a86 for unix.c


Ignore:
Timestamp:
2008-06-10T03:09:49Z (12 years ago)
Author:
Jelmer Vernooij <jelmer@…>
Branches:
master
Children:
fde7b91
Parents:
55eda08
Message:

Move random_bytes() back to lib/

File:
1 edited

Legend:

Unmodified
Added
Removed
  • unix.c

    r55eda08 r7f49a86  
    226226}
    227227
    228 /* A pretty reliable random number generator. Tries to use the /dev/random
    229    devices first, and falls back to the random number generator from libc
    230    when it fails. Opens randomizer devices with O_NONBLOCK to make sure a
    231    lack of entropy won't halt BitlBee. */
    232 void random_bytes( unsigned char *buf, int count )
    233 {
    234         static int use_dev = -1;
    235        
    236         /* Actually this probing code isn't really necessary, is it? */
    237         if( use_dev == -1 )
    238         {
    239                 if( access( "/dev/random", R_OK ) == 0 || access( "/dev/urandom", R_OK ) == 0 )
    240                         use_dev = 1;
    241                 else
    242                 {
    243                         use_dev = 0;
    244                         srand( ( getpid() << 16 ) ^ time( NULL ) );
    245                 }
    246         }
    247        
    248         if( use_dev )
    249         {
    250                 int fd;
    251                
    252                 /* At least on Linux, /dev/random can block if there's not
    253                    enough entropy. We really don't want that, so if it can't
    254                    give anything, use /dev/urandom instead. */
    255                 if( ( fd = open( "/dev/random", O_RDONLY | O_NONBLOCK ) ) >= 0 )
    256                         if( read( fd, buf, count ) == count )
    257                         {
    258                                 close( fd );
    259                                 return;
    260                         }
    261                 close( fd );
    262                
    263                 /* urandom isn't supposed to block at all, but just to be
    264                    sure. If it blocks, we'll disable use_dev and use the libc
    265                    randomizer instead. */
    266                 if( ( fd = open( "/dev/urandom", O_RDONLY | O_NONBLOCK ) ) >= 0 )
    267                         if( read( fd, buf, count ) == count )
    268                         {
    269                                 close( fd );
    270                                 return;
    271                         }
    272                 close( fd );
    273                
    274                 /* If /dev/random blocks once, we'll still try to use it
    275                    again next time. If /dev/urandom also fails for some
    276                    reason, stick with libc during this session. */
    277                
    278                 use_dev = 0;
    279                 srand( ( getpid() << 16 ) ^ time( NULL ) );
    280         }
    281        
    282         if( !use_dev )
    283         {
    284                 int i;
    285                
    286                 /* Possibly the LSB of rand() isn't very random on some
    287                    platforms. Seems okay on at least Linux and OSX though. */
    288                 for( i = 0; i < count; i ++ )
    289                         buf[i] = rand() & 0xff;
    290         }
    291 }
    292 
    293 
     228
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