token.lua

-- token.lua - generate google authenticator token value keystrokes
-- written by Teun Vink <github@teun.tv>
-- https://github.com/teunvink/hammerspoon
--
-- Retrieve a google authenticator token seed from keychain and use this to calculate the current value
-- Simulate keystrokes for this token value

local gauth = require "gauth"

-- code is based on:
--   https://github.com/imzyxwvu/lua-gauth/blob/master/gauth.lua (with small modifications)
--   https://github.com/kikito/sha.lua

-- read a password from a keychain
function password_from_keychain(name)
    -- 'name' should be saved in the login keychain
    local cmd="/usr/bin/security 2>&1 >/dev/null find-generic-password -ga " .. name .. " | sed -En '/^password: / s,^password: \"(.*)\"$,\\1,p'"
    local handle = io.popen(cmd)
    local result = handle:read("*a")
    handle:close()
    return (result:gsub("^%s*(.-)%s*$", "%1"))
end

-- read a token seed from keychain, generate a code and make keystrokes for it
function token_keystroke(token_name)
    local token = password_from_keychain(token_name)
    local hash = gauth.GenCode(token, math.floor(os.time() / 30))

    -- generate keystrokes for the result
    hs.eventtap.keyStrokes(("%06d"):format(hash))
end