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Contents
require 'openssl'
module Net::SSH::Transport
# Pure-Ruby implementation of Stateful Decryption Counter(SDCTR) Mode
# for Block Ciphers. See RFC4344 for detail.
module CTR
def self.extended(orig)
orig.instance_eval {
@remaining = ""
@counter = nil
@counter_len = orig.block_size
orig.encrypt
orig.padding = 0
}
class <<orig
alias :_update :update
private :_update
undef :update
def iv
@counter
end
def iv_len
block_size
end
def iv=(iv_s)
@counter = iv_s if @counter.nil?
end
def encrypt
# DO NOTHING (always set to "encrypt")
end
def decrypt
# DO NOTHING (always set to "encrypt")
end
def padding=(pad)
# DO NOTHING (always 0)
end
def reset
@remaining = ""
end
def update(data)
@remaining += data
encrypted = ""
while @remaining.bytesize >= block_size
encrypted += xor!(@remaining.slice!(0, block_size),
_update(@counter))
increment_counter!
end
encrypted
end
def final
unless @remaining.empty?
s = xor!(@remaining, _update(@counter))
else
s = ""
end
@remaining = ""
s
end
private
def xor!(s1, s2)
s = []
s1.unpack('Q*').zip(s2.unpack('Q*')) {|a,b| s.push(a^b) }
s.pack('Q*')
end
def increment_counter!
c = @counter_len
while ((c -= 1) > 0)
if @counter.setbyte(c, (@counter.getbyte(c) + 1) & 0xff) != 0
break
end
end
end
end
end
end
end
Version data entries
93 entries across 83 versions & 12 rubygems