Changeset 7f49a86 for lib


Ignore:
Timestamp:
2008-06-10T03:09:49Z (11 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
  • lib/misc.c

    r55eda08 r7f49a86  
    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. */
     398void random_bytes( unsigned char *buf, int count )
     399{
     400#ifndef _WIN32
     401        static int use_dev = -1;
     402       
     403        /* Actually this probing code isn't really necessary, is it? */
     404        if( use_dev == -1 )
     405        {
     406                if( access( "/dev/random", R_OK ) == 0 || access( "/dev/urandom", R_OK ) == 0 )
     407                        use_dev = 1;
     408                else
     409                {
     410                        use_dev = 0;
     411                        srand( ( getpid() << 16 ) ^ time( NULL ) );
     412                }
     413        }
     414       
     415        if( use_dev )
     416        {
     417                int fd;
     418               
     419                /* At least on Linux, /dev/random can block if there's not
     420                   enough entropy. We really don't want that, so if it can't
     421                   give anything, use /dev/urandom instead. */
     422                if( ( fd = open( "/dev/random", O_RDONLY | O_NONBLOCK ) ) >= 0 )
     423                        if( read( fd, buf, count ) == count )
     424                        {
     425                                close( fd );
     426                                return;
     427                        }
     428                close( fd );
     429               
     430                /* urandom isn't supposed to block at all, but just to be
     431                   sure. If it blocks, we'll disable use_dev and use the libc
     432                   randomizer instead. */
     433                if( ( fd = open( "/dev/urandom", O_RDONLY | O_NONBLOCK ) ) >= 0 )
     434                        if( read( fd, buf, count ) == count )
     435                        {
     436                                close( fd );
     437                                return;
     438                        }
     439                close( fd );
     440               
     441                /* If /dev/random blocks once, we'll still try to use it
     442                   again next time. If /dev/urandom also fails for some
     443                   reason, stick with libc during this session. */
     444               
     445                use_dev = 0;
     446                srand( ( getpid() << 16 ) ^ time( NULL ) );
     447        }
     448       
     449        if( !use_dev )
     450#endif
     451        {
     452                int i;
     453               
     454                /* Possibly the LSB of rand() isn't very random on some
     455                   platforms. Seems okay on at least Linux and OSX though. */
     456                for( i = 0; i < count; i ++ )
     457                        buf[i] = rand() & 0xff;
     458        }
     459}
     460
    394461int is_bool( char *value )
    395462{
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