f70be197e0
git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@2437 e93f8b46-1217-0410-a6f0-8f06a7374b81
90 lines
2.7 KiB
Ruby
90 lines
2.7 KiB
Ruby
require "openid/util"
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require "openid/cryptutil"
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module OpenID
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# Encapsulates a Diffie-Hellman key exchange. This class is used
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# internally by both the consumer and server objects.
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#
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# Read more about Diffie-Hellman on wikipedia:
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# http://en.wikipedia.org/wiki/Diffie-Hellman
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class DiffieHellman
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# From the OpenID specification
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@@default_mod = 155172898181473697471232257763715539915724801966915404479707795314057629378541917580651227423698188993727816152646631438561595825688188889951272158842675419950341258706556549803580104870537681476726513255747040765857479291291572334510643245094715007229621094194349783925984760375594985848253359305585439638443
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@@default_gen = 2
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attr_reader :modulus, :generator, :public
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# A new DiffieHellman object, using the modulus and generator from
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# the OpenID specification
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def DiffieHellman.from_defaults
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DiffieHellman.new(@@default_mod, @@default_gen)
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end
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def initialize(modulus=nil, generator=nil, priv=nil)
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@modulus = modulus.nil? ? @@default_mod : modulus
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@generator = generator.nil? ? @@default_gen : generator
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set_private(priv.nil? ? OpenID::CryptUtil.rand(@modulus-2) + 1 : priv)
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end
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def get_shared_secret(composite)
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DiffieHellman.powermod(composite, @private, @modulus)
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end
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def xor_secret(algorithm, composite, secret)
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dh_shared = get_shared_secret(composite)
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packed_dh_shared = OpenID::CryptUtil.num_to_binary(dh_shared)
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hashed_dh_shared = algorithm.call(packed_dh_shared)
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return DiffieHellman.strxor(secret, hashed_dh_shared)
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end
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def using_default_values?
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@generator == @@default_gen && @modulus == @@default_mod
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end
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private
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def set_private(priv)
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@private = priv
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@public = DiffieHellman.powermod(@generator, @private, @modulus)
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end
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def DiffieHellman.strxor(s, t)
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if s.length != t.length
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raise ArgumentError, "strxor: lengths don't match. " +
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"Inputs were #{s.inspect} and #{t.inspect}"
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end
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if String.method_defined? :bytes
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s.bytes.zip(t.bytes).map{|sb,tb| sb^tb}.pack('C*')
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else
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indices = 0...(s.length)
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chrs = indices.collect {|i| (s[i]^t[i]).chr}
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chrs.join("")
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end
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end
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# This code is taken from this post:
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# <http://blade.nagaokaut.ac.jp/cgi-bin/scat.\rb/ruby/ruby-talk/19098>
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# by Eric Lee Green.
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def DiffieHellman.powermod(x, n, q)
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counter=0
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n_p=n
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y_p=1
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z_p=x
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while n_p != 0
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if n_p[0]==1
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y_p=(y_p*z_p) % q
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end
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n_p = n_p >> 1
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z_p = (z_p * z_p) % q
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counter += 1
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end
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return y_p
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end
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end
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end
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