Changeset 69aaf14 for lib/misc.c
- Timestamp:
- 2008-04-02T15:40:33Z (16 years ago)
- Branches:
- master
- Children:
- 6ff51ff
- Parents:
- fa75134 (diff), 5f5d433 (diff), 5be87b2 (diff), 4af7b4f (diff), f1e7407 (diff)
Note: this is a merge changeset, the changes displayed below correspond to the merge itself.
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- 1 edited
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lib/misc.c
rfa75134 r69aaf14 392 392 } 393 393 394 /* A pretty reliable random number generator. Tries to use the /dev/random395 devices first, and falls back to the random number generator from libc396 when it fails. Opens randomizer devices with O_NONBLOCK to make sure a397 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 else408 {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 not419 enough entropy. We really don't want that, so if it can't420 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 be430 sure. If it blocks, we'll disable use_dev and use the libc431 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 it441 again next time. If /dev/urandom also fails for some442 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 some453 platforms. Seems okay on at least Linux and OSX though. */454 for( i = 0; i < count; i ++ )455 buf[i] = rand() & 0xff;456 }457 }458 459 394 int is_bool( char *value ) 460 395 {
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