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require 'base64'
require 'active_support/core_ext/object/blank'
require 'active_support/security_utils'
module ActiveSupport
# +MessageVerifier+ makes it easy to generate and verify messages which are
# signed to prevent tampering.
#
# This is useful for cases like remember-me tokens and auto-unsubscribe links
# where the session store isn't suitable or available.
#
# Remember Me:
# cookies[:remember_me] = @verifier.generate([@user.id, 2.weeks.from_now])
#
# In the authentication filter:
#
# id, time = @verifier.verify(cookies[:remember_me])
# if time < Time.now
# self.current_user = User.find(id)
# end
#
# By default it uses Marshal to serialize the message. If you want to use
# another serialization method, you can set the serializer in the options
# hash upon initialization:
#
# @verifier = ActiveSupport::MessageVerifier.new('s3Krit', serializer: YAML)
class MessageVerifier
class InvalidSignature < StandardError; end
def initialize(secret, options = {})
raise ArgumentError, 'Secret should not be nil.' unless secret
@secret = secret
@digest = options[:digest] || 'SHA1'
@serializer = options[:serializer] || Marshal
end
def verify(signed_message)
raise InvalidSignature if signed_message.blank?
data, digest = signed_message.split("--")
if data.present? && digest.present? && ActiveSupport::SecurityUtils.secure_compare(digest, generate_digest(data))
begin
@serializer.load(decode(data))
rescue ArgumentError => argument_error
raise InvalidSignature if argument_error.message =~ %r{invalid base64}
raise
end
else
raise InvalidSignature
end
end
def generate(value)
data = encode(@serializer.dump(value))
"#{data}--#{generate_digest(data)}"
end
private
def encode(data)
::Base64.strict_encode64(data)
end
def decode(data)
::Base64.strict_decode64(data)
end
def generate_digest(data)
require 'openssl' unless defined?(OpenSSL)
OpenSSL::HMAC.hexdigest(OpenSSL::Digest.const_get(@digest).new, @secret, data)
end
end
end
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