/usr/lib/ruby/vendor_ruby/active_support/message_verifier.rb is in ruby-activesupport-3.2 3.2.16-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 | require 'active_support/base64'
require 'active_support/deprecation'
require 'active_support/core_ext/object/blank'
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 attribute to something that responds
# to dump and load, e.g.:
#
# @verifier.serializer = YAML
class MessageVerifier
class InvalidSignature < StandardError; end
def initialize(secret, options = {})
unless options.is_a?(Hash)
ActiveSupport::Deprecation.warn "The second parameter should be an options hash. Use :digest => 'algorithm' to specify the digest algorithm."
options = { :digest => options }
end
@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? && secure_compare(digest, generate_digest(data))
@serializer.load(::Base64.decode64(data))
else
raise InvalidSignature
end
end
def generate(value)
data = ::Base64.strict_encode64(@serializer.dump(value))
"#{data}--#{generate_digest(data)}"
end
private
# constant-time comparison algorithm to prevent timing attacks
def secure_compare(a, b)
return false unless a.bytesize == b.bytesize
l = a.unpack "C#{a.bytesize}"
res = 0
b.each_byte { |byte| res |= byte ^ l.shift }
res == 0
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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