
-- Copyright (c) 2016 IBM. All rights reserved.
--
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--   copy of this software and associated documentation files (the "Software"),
--   to deal in the Software without restriction, including without limitation
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--   and/or sell copies of the Software, and to permit persons to whom the
--   Software is furnished to do so, subject to the following conditions:
--
--   The above copyright notice and this permission notice shall be included in
--   all copies or substantial portions of the Software.
--
--   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
--   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
--   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
--   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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--- @module apiKey
-- Check a subscription with an API Key
-- @author Cody Walker (cmwalker), Alex Song (songs)

local dataStore = require "lib/dataStore"
local utils = require "lib/utils"
local request = require "lib/request"

local REDIS_HOST = os.getenv("REDIS_HOST")
local REDIS_PORT = os.getenv("REDIS_PORT")
local REDIS_PASS = os.getenv("REDIS_PASS")

local _M = {}

--- Validate that the given subscription is in the datastore
-- @param dataStore the datastore object
-- @param tenant the namespace
-- @param gatewayPath the gateway path to use, if scope is resource
-- @param apiId api Id to use, if scope is api
-- @param scope scope of the subscription
-- @param apiKey the subscription api key
-- @param return boolean value indicating if the subscription exists in redis
function validate(dataStore, tenant, gatewayPath, apiId, scope, apiKey)
  -- Open connection to redis or use one from connection pool
  local k
  if scope == 'tenant' then
    k = utils.concatStrings({'subscriptions:tenant:', tenant})
  elseif scope == 'resource' then
    k = utils.concatStrings({'subscriptions:tenant:', tenant, ':resource:', gatewayPath})
  elseif scope == 'api' then
    k = utils.concatStrings({'subscriptions:tenant:', tenant, ':api:', apiId})
  end
  k = utils.concatStrings({k, ':key:', apiKey})
  if dataStore:exists(k) == 1 then
    return k
  else
    return nil
  end
end

function process(dataStore, securityObj)
  return processWithHashFunction(dataStore, securityObj, sha256)
end

--- Process the security object
-- @param dataStore the datastore object
-- @param securityObj security object from nginx conf file
-- @param hashFunction a function that will be called to hash the string
-- @return apiKey api key for the subscription
function processWithHashFunction(dataStore, securityObj, hashFunction)
  local tenant = ngx.var.tenant
  local gatewayPath = ngx.var.gatewayPath
  local apiId = dataStore:resourceToApi(utils.concatStrings({'resources:', tenant, ':', gatewayPath}))
  local scope = securityObj.scope
  local name = (securityObj.name == nil) and ((securityObj.header == nil) and 'x-api-key' or securityObj.header) or securityObj.name
  local queryString = ngx.req.get_uri_args()
  local location = (securityObj.location == nil) and 'header' or securityObj.location
-- backwards compatible with "header" argument for name value. "name" argument takes precedent if both provided
  local name = (securityObj.name == nil and securityObj.header == nil) and 'x-api-key' or (securityObj.name or securityObj.header)
  local apiKey = nil

  if location == "header" then
    apiKey = ngx.var[utils.concatStrings({'http_', name}):gsub("-", "_")]
  end
  if location == "query" then
    apiKey = queryString[name]
  end
  if apiKey == nil or apiKey == '' then
    request.err(401, 'Unauthorized')
    return nil
  end
  if securityObj.hashed then
    apiKey = hashFunction(apiKey)
  end
  local key = validate(dataStore, tenant, gatewayPath, apiId, scope, apiKey)
  if key == nil then
    request.err(401, 'Unauthorized')
    return nil
  end
  ngx.var.apiKey = apiKey
  return apiKey
end

--- Calculate the sha256 hash of a string
-- @param str the string you want to hash
-- @return a hashed version of the string
function sha256(str)
  local resty_sha256 = require "resty.sha256"
  local resty_str = require "resty.string"
  local sha = resty_sha256:new()
  sha:update(str)
  local digest = sha:final()
  return resty_str.to_hex(digest)
end
_M.processWithHashFunction = processWithHashFunction
_M.process = process

return _M