require "base64"
require "active_support/security_utils"

module ActionController
  # Makes it dead easy to do HTTP Basic, Digest and Token authentication.
  module HttpAuthentication
    # Makes it dead easy to do HTTP \Basic authentication.
    #
    # === Simple \Basic example
    #
    #   class PostsController < ApplicationController
    #     http_basic_authenticate_with name: "dhh", password: "secret", except: :index
    #
    #     def index
    #       render plain: "Everyone can see me!"
    #     end
    #
    #     def edit
    #       render plain: "I'm only accessible if you know the password"
    #     end
    #  end
    #
    # === Advanced \Basic example
    #
    # Here is a more advanced \Basic example where only Atom feeds and the XML API is protected by HTTP authentication,
    # the regular HTML interface is protected by a session approach:
    #
    #   class ApplicationController < ActionController::Base
    #     before_action :set_account, :authenticate
    #
    #     private
    #       def set_account
    #         @account = Account.find_by(url_name: request.subdomains.first)
    #       end
    #
    #       def authenticate
    #         case request.format
    #         when Mime[:xml], Mime[:atom]
    #           if user = authenticate_with_http_basic { |u, p| @account.users.authenticate(u, p) }
    #             @current_user = user
    #           else
    #             request_http_basic_authentication
    #           end
    #         else
    #           if session_authenticated?
    #             @current_user = @account.users.find(session[:authenticated][:user_id])
    #           else
    #             redirect_to(login_url) and return false
    #           end
    #         end
    #       end
    #   end
    #
    # In your integration tests, you can do something like this:
    #
    #   def test_access_granted_from_xml
    #     @request.env['HTTP_AUTHORIZATION'] = ActionController::HttpAuthentication::Basic.encode_credentials(users(:dhh).name, users(:dhh).password)
    #     get "/notes/1.xml"
    #
    #     assert_equal 200, status
    #   end
    module Basic
      extend self

      module ControllerMethods
        extend ActiveSupport::Concern

        module ClassMethods
          def http_basic_authenticate_with(options = {})
            before_action(options.except(:name, :password, :realm)) do
              authenticate_or_request_with_http_basic(options[:realm] || "Application") do |name, password|
                # This comparison uses & so that it doesn't short circuit and
                # uses `variable_size_secure_compare` so that length information
                # isn't leaked.
                ActiveSupport::SecurityUtils.variable_size_secure_compare(name, options[:name]) &
                  ActiveSupport::SecurityUtils.variable_size_secure_compare(password, options[:password])
              end
            end
          end
        end

        def authenticate_or_request_with_http_basic(realm = "Application", message = nil, &login_procedure)
          authenticate_with_http_basic(&login_procedure) || request_http_basic_authentication(realm, message)
        end

        def authenticate_with_http_basic(&login_procedure)
          HttpAuthentication::Basic.authenticate(request, &login_procedure)
        end

        def request_http_basic_authentication(realm = "Application", message = nil)
          HttpAuthentication::Basic.authentication_request(self, realm, message)
        end
      end

      def authenticate(request, &login_procedure)
        if has_basic_credentials?(request)
          login_procedure.call(*user_name_and_password(request))
        end
      end

      def has_basic_credentials?(request)
        request.authorization.present? && (auth_scheme(request).downcase == "basic")
      end

      def user_name_and_password(request)
        decode_credentials(request).split(":", 2)
      end

      def decode_credentials(request)
        ::Base64.decode64(auth_param(request) || "")
      end

      def auth_scheme(request)
        request.authorization.to_s.split(" ", 2).first
      end

      def auth_param(request)
        request.authorization.to_s.split(" ", 2).second
      end

      def encode_credentials(user_name, password)
        "Basic #{::Base64.strict_encode64("#{user_name}:#{password}")}"
      end

      def authentication_request(controller, realm, message)
        message ||= "HTTP Basic: Access denied.\n"
        controller.headers["WWW-Authenticate"] = %(Basic realm="#{realm.tr('"'.freeze, "".freeze)}")
        controller.status = 401
        controller.response_body = message
      end
    end

    # Makes it dead easy to do HTTP \Digest authentication.
    #
    # === Simple \Digest example
    #
    #   require 'digest/md5'
    #   class PostsController < ApplicationController
    #     REALM = "SuperSecret"
    #     USERS = {"dhh" => "secret", #plain text password
    #              "dap" => Digest::MD5.hexdigest(["dap",REALM,"secret"].join(":"))}  #ha1 digest password
    #
    #     before_action :authenticate, except: [:index]
    #
    #     def index
    #       render plain: "Everyone can see me!"
    #     end
    #
    #     def edit
    #       render plain: "I'm only accessible if you know the password"
    #     end
    #
    #     private
    #       def authenticate
    #         authenticate_or_request_with_http_digest(REALM) do |username|
    #           USERS[username]
    #         end
    #       end
    #   end
    #
    # === Notes
    #
    # The +authenticate_or_request_with_http_digest+ block must return the user's password
    # or the ha1 digest hash so the framework can appropriately hash to check the user's
    # credentials. Returning +nil+ will cause authentication to fail.
    #
    # Storing the ha1 hash: MD5(username:realm:password), is better than storing a plain password. If
    # the password file or database is compromised, the attacker would be able to use the ha1 hash to
    # authenticate as the user at this +realm+, but would not have the user's password to try using at
    # other sites.
    #
    # In rare instances, web servers or front proxies strip authorization headers before
    # they reach your application. You can debug this situation by logging all environment
    # variables, and check for HTTP_AUTHORIZATION, amongst others.
    module Digest
      extend self

      module ControllerMethods
        def authenticate_or_request_with_http_digest(realm = "Application", message = nil, &password_procedure)
          authenticate_with_http_digest(realm, &password_procedure) || request_http_digest_authentication(realm, message)
        end

        # Authenticate with HTTP Digest, returns true or false
        def authenticate_with_http_digest(realm = "Application", &password_procedure)
          HttpAuthentication::Digest.authenticate(request, realm, &password_procedure)
        end

        # Render output including the HTTP Digest authentication header
        def request_http_digest_authentication(realm = "Application", message = nil)
          HttpAuthentication::Digest.authentication_request(self, realm, message)
        end
      end

      # Returns false on a valid response, true otherwise
      def authenticate(request, realm, &password_procedure)
        request.authorization && validate_digest_response(request, realm, &password_procedure)
      end

      # Returns false unless the request credentials response value matches the expected value.
      # First try the password as a ha1 digest password. If this fails, then try it as a plain
      # text password.
      def validate_digest_response(request, realm, &password_procedure)
        secret_key  = secret_token(request)
        credentials = decode_credentials_header(request)
        valid_nonce = validate_nonce(secret_key, request, credentials[:nonce])

        if valid_nonce && realm == credentials[:realm] && opaque(secret_key) == credentials[:opaque]
          password = password_procedure.call(credentials[:username])
          return false unless password

          method = request.get_header("rack.methodoverride.original_method") || request.get_header("REQUEST_METHOD")
          uri    = credentials[:uri]

          [true, false].any? do |trailing_question_mark|
            [true, false].any? do |password_is_ha1|
              _uri = trailing_question_mark ? uri + "?" : uri
              expected = expected_response(method, _uri, credentials, password, password_is_ha1)
              expected == credentials[:response]
            end
          end
        end
      end

      # Returns the expected response for a request of +http_method+ to +uri+ with the decoded +credentials+ and the expected +password+
      # Optional parameter +password_is_ha1+ is set to +true+ by default, since best practice is to store ha1 digest instead
      # of a plain-text password.
      def expected_response(http_method, uri, credentials, password, password_is_ha1 = true)
        ha1 = password_is_ha1 ? password : ha1(credentials, password)
        ha2 = ::Digest::MD5.hexdigest([http_method.to_s.upcase, uri].join(":"))
        ::Digest::MD5.hexdigest([ha1, credentials[:nonce], credentials[:nc], credentials[:cnonce], credentials[:qop], ha2].join(":"))
      end

      def ha1(credentials, password)
        ::Digest::MD5.hexdigest([credentials[:username], credentials[:realm], password].join(":"))
      end

      def encode_credentials(http_method, credentials, password, password_is_ha1)
        credentials[:response] = expected_response(http_method, credentials[:uri], credentials, password, password_is_ha1)
        "Digest " + credentials.sort_by { |x| x[0].to_s }.map { |v| "#{v[0]}='#{v[1]}'" }.join(", ")
      end

      def decode_credentials_header(request)
        decode_credentials(request.authorization)
      end

      def decode_credentials(header)
        ActiveSupport::HashWithIndifferentAccess[header.to_s.gsub(/^Digest\s+/, "").split(",").map do |pair|
          key, value = pair.split("=", 2)
          [key.strip, value.to_s.gsub(/^"|"$/, "").delete('\'')]
        end]
      end

      def authentication_header(controller, realm)
        secret_key = secret_token(controller.request)
        nonce = self.nonce(secret_key)
        opaque = opaque(secret_key)
        controller.headers["WWW-Authenticate"] = %(Digest realm="#{realm}", qop="auth", algorithm=MD5, nonce="#{nonce}", opaque="#{opaque}")
      end

      def authentication_request(controller, realm, message = nil)
        message ||= "HTTP Digest: Access denied.\n"
        authentication_header(controller, realm)
        controller.status = 401
        controller.response_body = message
      end

      def secret_token(request)
        key_generator  = request.key_generator
        http_auth_salt = request.http_auth_salt
        key_generator.generate_key(http_auth_salt)
      end

      # Uses an MD5 digest based on time to generate a value to be used only once.
      #
      # A server-specified data string which should be uniquely generated each time a 401 response is made.
      # It is recommended that this string be base64 or hexadecimal data.
      # Specifically, since the string is passed in the header lines as a quoted string, the double-quote character is not allowed.
      #
      # The contents of the nonce are implementation dependent.
      # The quality of the implementation depends on a good choice.
      # A nonce might, for example, be constructed as the base 64 encoding of
      #
      #   time-stamp H(time-stamp ":" ETag ":" private-key)
      #
      # where time-stamp is a server-generated time or other non-repeating value,
      # ETag is the value of the HTTP ETag header associated with the requested entity,
      # and private-key is data known only to the server.
      # With a nonce of this form a server would recalculate the hash portion after receiving the client authentication header and
      # reject the request if it did not match the nonce from that header or
      # if the time-stamp value is not recent enough. In this way the server can limit the time of the nonce's validity.
      # The inclusion of the ETag prevents a replay request for an updated version of the resource.
      # (Note: including the IP address of the client in the nonce would appear to offer the server the ability
      # to limit the reuse of the nonce to the same client that originally got it.
      # However, that would break proxy farms, where requests from a single user often go through different proxies in the farm.
      # Also, IP address spoofing is not that hard.)
      #
      # An implementation might choose not to accept a previously used nonce or a previously used digest, in order to
      # protect against a replay attack. Or, an implementation might choose to use one-time nonces or digests for
      # POST, PUT, or PATCH requests and a time-stamp for GET requests. For more details on the issues involved see Section 4
      # of this document.
      #
      # The nonce is opaque to the client. Composed of Time, and hash of Time with secret
      # key from the Rails session secret generated upon creation of project. Ensures
      # the time cannot be modified by client.
      def nonce(secret_key, time = Time.now)
        t = time.to_i
        hashed = [t, secret_key]
        digest = ::Digest::MD5.hexdigest(hashed.join(":"))
        ::Base64.strict_encode64("#{t}:#{digest}")
      end

      # Might want a shorter timeout depending on whether the request
      # is a PATCH, PUT, or POST, and if the client is a browser or web service.
      # Can be much shorter if the Stale directive is implemented. This would
      # allow a user to use new nonce without prompting the user again for their
      # username and password.
      def validate_nonce(secret_key, request, value, seconds_to_timeout = 5 * 60)
        return false if value.nil?
        t = ::Base64.decode64(value).split(":").first.to_i
        nonce(secret_key, t) == value && (t - Time.now.to_i).abs <= seconds_to_timeout
      end

      # Opaque based on digest of secret key
      def opaque(secret_key)
        ::Digest::MD5.hexdigest(secret_key)
      end
    end

    # Makes it dead easy to do HTTP Token authentication.
    #
    # Simple Token example:
    #
    #   class PostsController < ApplicationController
    #     TOKEN = "secret"
    #
    #     before_action :authenticate, except: [ :index ]
    #
    #     def index
    #       render plain: "Everyone can see me!"
    #     end
    #
    #     def edit
    #       render plain: "I'm only accessible if you know the password"
    #     end
    #
    #     private
    #       def authenticate
    #         authenticate_or_request_with_http_token do |token, options|
    #           # Compare the tokens in a time-constant manner, to mitigate
    #           # timing attacks.
    #           ActiveSupport::SecurityUtils.secure_compare(
    #             ::Digest::SHA256.hexdigest(token),
    #             ::Digest::SHA256.hexdigest(TOKEN)
    #           )
    #         end
    #       end
    #   end
    #
    #
    # Here is a more advanced Token example where only Atom feeds and the XML API is protected by HTTP token authentication,
    # the regular HTML interface is protected by a session approach:
    #
    #   class ApplicationController < ActionController::Base
    #     before_action :set_account, :authenticate
    #
    #     private
    #       def set_account
    #         @account = Account.find_by(url_name: request.subdomains.first)
    #       end
    #
    #       def authenticate
    #         case request.format
    #         when Mime[:xml], Mime[:atom]
    #           if user = authenticate_with_http_token { |t, o| @account.users.authenticate(t, o) }
    #             @current_user = user
    #           else
    #             request_http_token_authentication
    #           end
    #         else
    #           if session_authenticated?
    #             @current_user = @account.users.find(session[:authenticated][:user_id])
    #           else
    #             redirect_to(login_url) and return false
    #           end
    #         end
    #       end
    #   end
    #
    #
    # In your integration tests, you can do something like this:
    #
    #   def test_access_granted_from_xml
    #     get(
    #       "/notes/1.xml", nil,
    #       'HTTP_AUTHORIZATION' => ActionController::HttpAuthentication::Token.encode_credentials(users(:dhh).token)
    #     )
    #
    #     assert_equal 200, status
    #   end
    #
    #
    # On shared hosts, Apache sometimes doesn't pass authentication headers to
    # FCGI instances. If your environment matches this description and you cannot
    # authenticate, try this rule in your Apache setup:
    #
    #   RewriteRule ^(.*)$ dispatch.fcgi [E=X-HTTP_AUTHORIZATION:%{HTTP:Authorization},QSA,L]
    module Token
      TOKEN_KEY = "token="
      TOKEN_REGEX = /^(Token|Bearer)\s+/
      AUTHN_PAIR_DELIMITERS = /(?:,|;|\t+)/
      extend self

      module ControllerMethods
        def authenticate_or_request_with_http_token(realm = "Application", message = nil, &login_procedure)
          authenticate_with_http_token(&login_procedure) || request_http_token_authentication(realm, message)
        end

        def authenticate_with_http_token(&login_procedure)
          Token.authenticate(self, &login_procedure)
        end

        def request_http_token_authentication(realm = "Application", message = nil)
          Token.authentication_request(self, realm, message)
        end
      end

      # If token Authorization header is present, call the login
      # procedure with the present token and options.
      #
      # [controller]
      #   ActionController::Base instance for the current request.
      #
      # [login_procedure]
      #   Proc to call if a token is present. The Proc should take two arguments:
      #
      #     authenticate(controller) { |token, options| ... }
      #
      # Returns the return value of <tt>login_procedure</tt> if a
      # token is found. Returns <tt>nil</tt> if no token is found.

      def authenticate(controller, &login_procedure)
        token, options = token_and_options(controller.request)
        unless token.blank?
          login_procedure.call(token, options)
        end
      end

      # Parses the token and options out of the token Authorization header.
      # The value for the Authorization header is expected to have the prefix
      # <tt>"Token"</tt> or <tt>"Bearer"</tt>. If the header looks like this:
      #   Authorization: Token token="abc", nonce="def"
      # Then the returned token is <tt>"abc"</tt>, and the options are
      # <tt>{nonce: "def"}</tt>
      #
      # request - ActionDispatch::Request instance with the current headers.
      #
      # Returns an +Array+ of <tt>[String, Hash]</tt> if a token is present.
      # Returns +nil+ if no token is found.
      def token_and_options(request)
        authorization_request = request.authorization.to_s
        if authorization_request[TOKEN_REGEX]
          params = token_params_from authorization_request
          [params.shift[1], Hash[params].with_indifferent_access]
        end
      end

      def token_params_from(auth)
        rewrite_param_values params_array_from raw_params auth
      end

      # Takes raw_params and turns it into an array of parameters
      def params_array_from(raw_params)
        raw_params.map { |param| param.split %r/=(.+)?/ }
      end

      # This removes the <tt>"</tt> characters wrapping the value.
      def rewrite_param_values(array_params)
        array_params.each { |param| (param[1] || "").gsub! %r/^"|"$/, "" }
      end

      # This method takes an authorization body and splits up the key-value
      # pairs by the standardized <tt>:</tt>, <tt>;</tt>, or <tt>\t</tt>
      # delimiters defined in +AUTHN_PAIR_DELIMITERS+.
      def raw_params(auth)
        _raw_params = auth.sub(TOKEN_REGEX, "").split(/\s*#{AUTHN_PAIR_DELIMITERS}\s*/)

        if !(_raw_params.first =~ %r{\A#{TOKEN_KEY}})
          _raw_params[0] = "#{TOKEN_KEY}#{_raw_params.first}"
        end

        _raw_params
      end

      # Encodes the given token and options into an Authorization header value.
      #
      # token   - String token.
      # options - optional Hash of the options.
      #
      # Returns String.
      def encode_credentials(token, options = {})
        values = ["#{TOKEN_KEY}#{token.to_s.inspect}"] + options.map do |key, value|
          "#{key}=#{value.to_s.inspect}"
        end
        "Token #{values * ", "}"
      end

      # Sets a WWW-Authenticate header to let the client know a token is desired.
      #
      # controller - ActionController::Base instance for the outgoing response.
      # realm      - String realm to use in the header.
      #
      # Returns nothing.
      def authentication_request(controller, realm, message = nil)
        message ||= "HTTP Token: Access denied.\n"
        controller.headers["WWW-Authenticate"] = %(Token realm="#{realm.tr('"'.freeze, "".freeze)}")
        controller.__send__ :render, plain: message, status: :unauthorized
      end
    end
  end
end
