Christopher Moore
97 lines
1.9 KiB
Ruby
97 lines
1.9 KiB
Ruby
# -*- coding: binary -*-
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require 'openssl'
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module Net::SSH::Transport
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# Pure-Ruby implementation of Stateful Decryption Counter(SDCTR) Mode
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# for Block Ciphers. See RFC4344 for detail.
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module CTR
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def self.extended(orig)
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orig.instance_eval {
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@remaining = ""
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@counter = nil
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@counter_len = orig.block_size
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orig.encrypt
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orig.padding = 0
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}
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class <<orig
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alias :_update :update
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private :_update
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undef :update
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def iv
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@counter
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end
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def iv_len
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block_size
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end
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def iv=(iv_s)
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@counter = iv_s if @counter.nil?
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end
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def encrypt
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# DO NOTHING (always set to "encrypt")
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end
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def decrypt
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# DO NOTHING (always set to "decrypt")
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end
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def padding=(pad)
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# DO NOTHING (always 0)
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end
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def reset
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@remaining = ""
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end
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def update(data)
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@remaining += data
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encrypted = ""
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while @remaining.bytesize >= block_size
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encrypted += xor!(@remaining.slice!(0, block_size),
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_update(@counter))
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increment_counter!
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end
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encrypted
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end
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def final
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unless @remaining.empty?
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s = xor!(@remaining, _update(@counter))
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else
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s = ""
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end
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@remaining = ""
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s
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end
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private
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def xor!(s1, s2)
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s = []
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s1.unpack('Q*').zip(s2.unpack('Q*')) {|a,b| s.push(a^b) }
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s.pack('Q*')
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end
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def increment_counter!
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c = @counter_len
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while ((c -= 1) > 0)
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if @counter.setbyte(c, (@counter.getbyte(c) + 1) & 0xff) != 0
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break
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end
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end
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end
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end
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end
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end
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end
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