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|
# frozen_string_literal: true
# this file originally based on authenticity_token.rb from the sinatra/rack-protection project
#
# The MIT License (MIT)
#
# Copyright (c) 2011-2017 Konstantin Haase
# Copyright (c) 2015-2017 Zachary Scott
#
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# 'Software'), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, 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 LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
# TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
# SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
require "securerandom"
require "rack/request"
module Sidekiq
class Web
class CsrfProtection
def initialize(app, options = nil)
@app = app
end
def call(env)
accept?(env) ? admit(env) : deny(env)
end
private
def admit(env)
# On each successful request, we create a fresh masked token
# which will be used in any forms rendered for this request.
s = session(env)
s[:csrf] ||= SecureRandom.base64(TOKEN_LENGTH)
env[:csrf_token] = mask_token(s[:csrf])
@app.call(env)
end
def safe?(env)
%w[GET HEAD OPTIONS TRACE].include? env["REQUEST_METHOD"]
end
def logger(env)
@logger ||= env["rack.logger"] || ::Logger.new(env["rack.errors"])
end
def deny(env)
logger(env).warn "attack prevented by #{self.class}"
[403, {Rack::CONTENT_TYPE => "text/plain"}, ["Forbidden"]]
end
def session(env)
env["rack.session"] || fail(<<~EOM)
Sidekiq::Web needs a valid Rack session for CSRF protection. If this is a Rails app,
make sure you mount Sidekiq::Web *inside* your application routes:
Rails.application.routes.draw do
mount Sidekiq::Web => "/sidekiq"
....
end
If this is a Rails app in API mode, you need to enable sessions.
https://guides.rubyonrails.org/api_app.html#using-session-middlewares
If this is a bare Rack app, use a session middleware before Sidekiq::Web:
# first, use IRB to create a shared secret key for sessions and commit it
require 'securerandom'; File.open(".session.key", "w") {|f| f.write(SecureRandom.hex(32)) }
# now use the secret with a session cookie middleware
use Rack::Session::Cookie, secret: File.read(".session.key"), same_site: true, max_age: 86400
run Sidekiq::Web
EOM
end
def accept?(env)
return true if safe?(env)
giventoken = ::Rack::Request.new(env).params["authenticity_token"]
valid_token?(env, giventoken)
end
TOKEN_LENGTH = 32
# Checks that the token given to us as a parameter matches
# the token stored in the session.
def valid_token?(env, giventoken)
return false if giventoken.nil? || giventoken.empty?
begin
token = decode_token(giventoken)
rescue ArgumentError # client input is invalid
return false
end
sess = session(env)
localtoken = sess[:csrf]
# Checks that Rack::Session::Cookie actually contains the csrf token
return false if localtoken.nil?
# Rotate the session token after every use
sess[:csrf] = SecureRandom.base64(TOKEN_LENGTH)
# See if it's actually a masked token or not. We should be able
# to handle any unmasked tokens that we've issued without error.
if unmasked_token?(token)
compare_with_real_token token, localtoken
elsif masked_token?(token)
unmasked = unmask_token(token)
compare_with_real_token unmasked, localtoken
else
false # Token is malformed
end
end
# Creates a masked version of the authenticity token that varies
# on each request. The masking is used to mitigate SSL attacks
# like BREACH.
def mask_token(token)
token = decode_token(token)
one_time_pad = SecureRandom.random_bytes(token.length)
encrypted_token = xor_byte_strings(one_time_pad, token)
masked_token = one_time_pad + encrypted_token
encode_token(masked_token)
end
# Essentially the inverse of +mask_token+.
def unmask_token(masked_token)
# Split the token into the one-time pad and the encrypted
# value and decrypt it
token_length = masked_token.length / 2
one_time_pad = masked_token[0...token_length]
encrypted_token = masked_token[token_length..]
xor_byte_strings(one_time_pad, encrypted_token)
end
def unmasked_token?(token)
token.length == TOKEN_LENGTH
end
def masked_token?(token)
token.length == TOKEN_LENGTH * 2
end
def compare_with_real_token(token, local)
::Rack::Utils.secure_compare(token.to_s, decode_token(local).to_s)
end
def encode_token(token)
[token].pack("m0").tr("+/", "-_")
end
def decode_token(token)
token.tr("-_", "+/").unpack1("m0")
end
def xor_byte_strings(s1, s2)
s1.bytes.zip(s2.bytes).map { |(c1, c2)| c1 ^ c2 }.pack("c*")
end
end
end
end
|
