impl flash.crypto.generateRandomBytes (google code Issue 103)

[zwetan]

https://code.google.com/p/redtamarin/issues/detail?id=103

---

see: http://help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/flash/crypto/package.html#generateRandomBytes()

signature:

public function generateRandomBytes(numberRandomBytes:uint):ByteArray

under Macintosh / Linux we can use /dev/urandom
$ cat /dev/urandom | LC_CTYPE=C tr -dc 'A-F0-9' | fold -w 2 | sed 1q

in AS3 that would gives

var str:String = Program.open( "cat /dev/urandom | LC_CTYPE=C tr -dc 'A-F0-9' | fold -w 2 | sed 1q" );
var byte:uint = uint( "0x" + str );

Under Windows we need to use CryptGenRandom()
see PHP implementation of php_win32_get_random_bytes
https://github.com/php/php-src/blob/master/win32/winutil.c#L80

---

because Program.open() call the CLI as sh -c ""

it is better to do like that

var str:String = Program.open( "LC_CTYPE=C tr -dc 'A-F0-9' < /dev/urandom | head -c 2" );

shorter command line, less dependencies and no risk to block the CLI and end up in an infinite loop while running the function, also avoid a carriage return at end of line

---

[zwetan]

we need to test this under Windows with cygwin_compat

eg. do we need to call something like
C:/cygwin/bin/bash.exe -c 'LC_CTYPE=C tr -dc 'A-F0-9' < /dev/urandom | head -c 2'
or
C:/cygwin/bin/sh.exe -c 'LC_CTYPE=C tr -dc 'A-F0-9' < /dev/urandom | head -c 2'

[zwetan]

we added a new C.stdlib function rand_s()
inspired by MSDN rand_s

Under Windows it reuse CRT rand_s() which uses RtlGenRandom()
see RtlGenRandom

Under POSIX systems (Linux and macOS) we implemented rand_s()
reading 1 byte from "/dev/urandom"

for flash.crypto.generateRandomBytes()

under Windows, we call rand_s() in a loop to fill a ByteArray

Under POSIX systems (Linux and macOS) we apply the same logic as the rand_s() implementation
reading N amount of bytes from "/dev/urandom"