https://github.com/vercel/lua-bcrypt

A bcrypt library for Lua
https://github.com/vercel/lua-bcrypt

Last synced: 3 months ago
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A bcrypt library for Lua

• Host: GitHub
• URL: https://github.com/vercel/lua-bcrypt
• Owner: vercel
• Fork: true (mikejsavage/lua-bcrypt)
• Created: 2020-02-13T11:30:42.000Z (almost 5 years ago)
• Default Branch: master
• Last Pushed: 2017-12-29T23:02:40.000Z (about 7 years ago)
• Last Synced: 2024-09-18T03:37:43.437Z (4 months ago)
• Homepage:
• Size: 131 KB
• Stars: 5
• Watchers: 2
• Forks: 2
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
A Lua wrapper for OpenBSD's bcrypt.

Requirements

------------

lua >= 5.1

Copying

-------

Many of the files in this repository have been taken from OpenBSD's

tree. You should consult individual file headers for specific licensing

information. More broadly, everything here is compatible with the [ISC

license][ISC].

[ISC]: http://en.wikipedia.org/wiki/ISC_license

Installation

------------

	$ luarocks install bcrypt

Usage

-----

	local bcrypt = require( "bcrypt" )

	

	-- Bigger numbers here will make your digest exponentially harder to compute

	local log_rounds = 9

	

	local digest = bcrypt.digest( "password", log_rounds )

	assert( bcrypt.verify( "password", digest ) )

Security concerns

-----------------

Lua will keep plaintext passwords around in memory as part of its string

interning mechanism. As far as I'm aware, there's nothing I can do about

this.

Tuning

------

If you would like to automatically tune the number of rounds to your

hardware, you can include a function like:

	function bcrypt.tune( t )

		local SAMPLES = 10

		local rounds = 5

	

		while true do

			local total = 0

	

			for i = 1, SAMPLES do

				local start = os.clock()

				bcrypt.digest( "asdf", rounds )

				local delta = os.clock() - start

	

				total = total + delta

			end

	

			if ( total / SAMPLES ) * 1000 >= t then

				return rounds - 1

			end

	

			rounds = rounds + 1

		end

	end

This function returns the largest load factor such that `bcrypt.digest(

str, work )` takes less than `t` milliseconds (assuming your CPU isn't

dodgy).

Note that this will take at least `2 * SAMPLES * t` ms to evaluate.

Chroot

------

[lua-setuid]: https://github.com/mikejsavage/lua-setuid

[test-chroot]: https://github.com/mikejsavage/lua-bcrypt/blob/master/test-chroot.lua

Some operating systems do not provide a method for reliably getting

random data from inside a chroot. One workaround for this is to chroot

after initialising lua-bcrypt, for example by using

[lua-setuid][lua-setuid].

	local setuid = require( "setuid" )

	local bcrypt = require( "bcrypt" )

	

	assert( setuid.chroot( "." ) )

	assert( not io.open( "/etc/passwd", "r" ) )

	

	print( bcrypt.digest( "adsf", 5 ) )

There are also operating system specific workarounds. On

non-bleeding-edge (earlier than 3.17) Linux kernels, you can run:

	mkdir /path/to/chroot/dev

	mknod -m 644 /path/to/chroot/dev/urandom c 1 9

I have included a test script in [`test-chroot.lua`][test-chroot].