auth.lua

local hmac = require "resty.hmac"
local setmetatable = setmetatable

local _M = { _VERSION = '0.0.1' }
local mt = { __index = _M }

function _M.new(self, secret)
    return setmetatable({_secret = secret}, mt)
end

function _M.is_valid(self, auth_header, url, custom_header)
    if not auth_header or not url or not custom_header then
        return false
    end
    local hmac512 = hmac:new()
    local string_to_sign = url .. ":" .. custom_header
    local digest = hmac:digest("sha512", self._secret, string_to_sign)
    local signed_b64 = ngx.encode_base64(digest)
    local result = "NYTV " .. signed_b64
    return result == auth_header
end

return _M