How to convert php crypt function (SHA512) to ruby?

Question

note: i am not looking for workaround, i am looking for a plain ruby solution!

this question is the similar to this question, but it isn't answerd, its just a workaround to a shell commando there.

i want to generate a sha512 encrypted string which is compatible with the format in debian /etc/shadow.

the following create a correct string with php:

$salt = 'fGn9LR75';
$hash = crypt('test', '$6$'.$salt);
// hash is:
// $6$fGn9LR75$YpI/vJHjEhvrYp5/eUSRinpiXdMthCxFWSEo0ktFNUaRBsA7pCWYzzmQptmnfyHno9YEJFNHYuESj3nAQmSzc1

as far as i know this a normal, salted base64 encoded string. the spec of the sha generation method is here

Answer 1

irb(main):001:0> salt = 'fGn9LR75';
irb(main):002:0* hash = 'test'.crypt('$6$' + salt);
irb(main):003:0* hash
=> "$6$fGn9LR75$YpI/vJHjEhvrYp5/eUSRinpiXdMthCxFWSEo0ktFNUaRBsA7pCWYzzmQptmnfyHno9YEJFNHYuESj3nAQmSzc1"

The crypt() algorithm for SHA256/512 is not simply a base64-encoded hash. It's an intentionally crazy process which involves multiple hashes running in parallel.