113 lines
2.7 KiB
Ruby
113 lines
2.7 KiB
Ruby
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# Copyright (C) 2001 Daiki Ueno <ueno@unixuser.org>
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# This library is distributed under the terms of the Ruby license.
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# This module provides common interface to HMAC engines.
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# HMAC standard is documented in RFC 2104:
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#
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# H. Krawczyk et al., "HMAC: Keyed-Hashing for Message Authentication",
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# RFC 2104, February 1997
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#
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# These APIs are inspired by JCE 1.2's javax.crypto.Mac interface.
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#
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# <URL:http://java.sun.com/security/JCE1.2/spec/apidoc/javax/crypto/Mac.html>
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module HMAC
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class Base
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def initialize(algorithm, block_size, output_length, key)
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@algorithm = algorithm
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@block_size = block_size
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@output_length = output_length
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@status = STATUS_UNDEFINED
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@key_xor_ipad = ''
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@key_xor_opad = ''
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set_key(key) unless key.nil?
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end
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private
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def check_status
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unless @status == STATUS_INITIALIZED
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raise RuntimeError,
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"The underlying hash algorithm has not yet been initialized."
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end
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end
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public
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def set_key(key)
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# If key is longer than the block size, apply hash function
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# to key and use the result as a real key.
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key = @algorithm.digest(key) if key.size > @block_size
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key_xor_ipad = "\x36" * @block_size
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key_xor_opad = "\x5C" * @block_size
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for i in 0 .. key.size - 1
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key_xor_ipad[i] ^= key[i]
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key_xor_opad[i] ^= key[i]
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end
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@key_xor_ipad = key_xor_ipad
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@key_xor_opad = key_xor_opad
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@md = @algorithm.new
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@status = STATUS_INITIALIZED
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end
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def reset_key
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@key_xor_ipad.gsub!(/./, '?')
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@key_xor_opad.gsub!(/./, '?')
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@key_xor_ipad[0..-1] = ''
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@key_xor_opad[0..-1] = ''
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@status = STATUS_UNDEFINED
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end
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def update(text)
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check_status
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# perform inner H
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md = @algorithm.new
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md.update(@key_xor_ipad)
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md.update(text)
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str = md.digest
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# perform outer H
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md = @algorithm.new
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md.update(@key_xor_opad)
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md.update(str)
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@md = md
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end
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alias << update
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def digest
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check_status
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@md.digest
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end
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def hexdigest
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check_status
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@md.hexdigest
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end
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alias to_s hexdigest
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# These two class methods below are safer than using above
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# instance methods combinatorially because an instance will have
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# held a key even if it's no longer in use.
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def Base.digest(key, text)
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begin
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hmac = self.new(key)
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hmac.update(text)
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hmac.digest
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ensure
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hmac.reset_key
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end
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end
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def Base.hexdigest(key, text)
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begin
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hmac = self.new(key)
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hmac.update(text)
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hmac.hexdigest
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ensure
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hmac.reset_key
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end
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end
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private_class_method :new, :digest, :hexdigest
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end
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STATUS_UNDEFINED, STATUS_INITIALIZED = 0, 1
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end
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