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