class Net::SSH::Transport::CipherFactory

Implements a factory of OpenSSL cipher algorithms.

Constants

SSH_TO_OSSL: Maps the SSH name of a cipher to it's corresponding OpenSSL name

Public Class Methods

get(name, options={}) click to toggle source

Retrieves a new instance of the named algorithm. The new instance will be initialized using an iv and key generated from the given iv, key, shared, hash and digester values. Additionally, the cipher will be put into encryption or decryption mode, based on the value of the encrypt parameter.

# File lib/net/ssh/transport/cipher_factory.rb, line 46
def self.get(name, options={})
  ossl_name = SSH_TO_OSSL[name] or raise NotImplementedError, "unimplemented cipher `#{name}'"
  return IdentityCipher if ossl_name == "none"
  cipher = OpenSSL::Cipher.new(ossl_name)
    
  cipher.send(options[:encrypt] ? :encrypt : :decrypt)
    
  cipher.padding = 0
    
  if name =~ /-ctr(@openssh.org)?$/
    if ossl_name !~ /-ctr/
      cipher.extend(Net::SSH::Transport::CTR)
    else
      cipher = Net::SSH::Transport::OpenSSLAESCTR.new(cipher)
    end
  end
  cipher.iv = Net::SSH::Transport::KeyExpander.expand_key(cipher.iv_len, options[:iv], options)
    
  key_len = cipher.key_len
  cipher.key_len = key_len
  cipher.key = Net::SSH::Transport::KeyExpander.expand_key(key_len, options[:key], options)
    
  return cipher
end

get_lengths(name, options = {}) click to toggle source

Returns a two-element array containing the [ key-length, block-size ] for the named cipher algorithm. If the cipher algorithm is unknown, or is “none”, 0 is returned for both elements of the tuple. if :iv_len option is supplied the third return value will be ivlen

# File lib/net/ssh/transport/cipher_factory.rb, line 76
def self.get_lengths(name, options = {})
  ossl_name = SSH_TO_OSSL[name]
  if ossl_name.nil? || ossl_name == "none"
    result = [0, 0]
    result << 0 if options[:iv_len]
  else
    cipher = OpenSSL::Cipher.new(ossl_name)
    key_len = cipher.key_len
    cipher.key_len = key_len
    
    block_size =
      case ossl_name
      when /\-ctr/
        Net::SSH::Transport::OpenSSLAESCTR.block_size
      else
        cipher.block_size
      end
    
    result = [key_len, block_size]
    result << cipher.iv_len if options[:iv_len]
  end
  result
end

supported?(name) click to toggle source

Returns true if the underlying OpenSSL library supports the given cipher, and false otherwise.

# File lib/net/ssh/transport/cipher_factory.rb, line 35
def self.supported?(name)
  ossl_name = SSH_TO_OSSL[name] or raise NotImplementedError, "unimplemented cipher `#{name}'"
  return true if ossl_name == "none"
  return OpenSSL::Cipher.ciphers.include?(ossl_name)
end