Changeset 5be87b2 for lib


Ignore:
Timestamp:
2008-04-02T15:03:02Z (12 years ago)
Author:
Jelmer Vernooij <jelmer@…>
Branches:
master
Children:
1a57b893, 69aaf14
Parents:
fa75134
Message:

Move unix-specific random_bytes() implementation to unix.c.

File:
1 edited

Legend:

Unmodified
Added
Removed
  • lib/misc.c

    rfa75134 r5be87b2  
    392392}
    393393
    394 /* A pretty reliable random number generator. Tries to use the /dev/random
    395    devices first, and falls back to the random number generator from libc
    396    when it fails. Opens randomizer devices with O_NONBLOCK to make sure a
    397    lack of entropy won't halt BitlBee. */
    398 void random_bytes( unsigned char *buf, int count )
    399 {
    400         static int use_dev = -1;
    401        
    402         /* Actually this probing code isn't really necessary, is it? */
    403         if( use_dev == -1 )
    404         {
    405                 if( access( "/dev/random", R_OK ) == 0 || access( "/dev/urandom", R_OK ) == 0 )
    406                         use_dev = 1;
    407                 else
    408                 {
    409                         use_dev = 0;
    410                         srand( ( getpid() << 16 ) ^ time( NULL ) );
    411                 }
    412         }
    413        
    414         if( use_dev )
    415         {
    416                 int fd;
    417                
    418                 /* At least on Linux, /dev/random can block if there's not
    419                    enough entropy. We really don't want that, so if it can't
    420                    give anything, use /dev/urandom instead. */
    421                 if( ( fd = open( "/dev/random", O_RDONLY | O_NONBLOCK ) ) >= 0 )
    422                         if( read( fd, buf, count ) == count )
    423                         {
    424                                 close( fd );
    425                                 return;
    426                         }
    427                 close( fd );
    428                
    429                 /* urandom isn't supposed to block at all, but just to be
    430                    sure. If it blocks, we'll disable use_dev and use the libc
    431                    randomizer instead. */
    432                 if( ( fd = open( "/dev/urandom", O_RDONLY | O_NONBLOCK ) ) >= 0 )
    433                         if( read( fd, buf, count ) == count )
    434                         {
    435                                 close( fd );
    436                                 return;
    437                         }
    438                 close( fd );
    439                
    440                 /* If /dev/random blocks once, we'll still try to use it
    441                    again next time. If /dev/urandom also fails for some
    442                    reason, stick with libc during this session. */
    443                
    444                 use_dev = 0;
    445                 srand( ( getpid() << 16 ) ^ time( NULL ) );
    446         }
    447        
    448         if( !use_dev )
    449         {
    450                 int i;
    451                
    452                 /* Possibly the LSB of rand() isn't very random on some
    453                    platforms. Seems okay on at least Linux and OSX though. */
    454                 for( i = 0; i < count; i ++ )
    455                         buf[i] = rand() & 0xff;
    456         }
    457 }
    458 
    459394int is_bool( char *value )
    460395{
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