81 lines
2.8 KiB
Ruby
81 lines
2.8 KiB
Ruby
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require 'openssl'
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require 'net/ssh/transport/identity_cipher'
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module Net; module SSH; module Transport
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# Implements a factory of OpenSSL cipher algorithms.
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class CipherFactory
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# Maps the SSH name of a cipher to it's corresponding OpenSSL name
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SSH_TO_OSSL = {
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"3des-cbc" => "des-ede3-cbc",
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"blowfish-cbc" => "bf-cbc",
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"aes256-cbc" => "aes-256-cbc",
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"aes192-cbc" => "aes-192-cbc",
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"aes128-cbc" => "aes-128-cbc",
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"idea-cbc" => "idea-cbc",
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"cast128-cbc" => "cast-cbc",
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"rijndael-cbc@lysator.liu.se" => "aes-256-cbc",
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"none" => "none"
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}
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# Returns true if the underlying OpenSSL library supports the given cipher,
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# and false otherwise.
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def self.supported?(name)
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ossl_name = SSH_TO_OSSL[name] or raise NotImplementedError, "unimplemented cipher `#{name}'"
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return true if ossl_name == "none"
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return OpenSSL::Cipher.ciphers.include?(ossl_name)
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end
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# Retrieves a new instance of the named algorithm. The new instance
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# will be initialized using an iv and key generated from the given
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# iv, key, shared, hash and digester values. Additionally, the
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# cipher will be put into encryption or decryption mode, based on the
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# value of the +encrypt+ parameter.
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def self.get(name, options={})
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ossl_name = SSH_TO_OSSL[name] or raise NotImplementedError, "unimplemented cipher `#{name}'"
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return IdentityCipher if ossl_name == "none"
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cipher = OpenSSL::Cipher::Cipher.new(ossl_name)
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cipher.send(options[:encrypt] ? :encrypt : :decrypt)
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cipher.padding = 0
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cipher.iv = make_key(cipher.iv_len, options[:iv], options)
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cipher.key = make_key(cipher.key_len, options[:key], options)
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return cipher
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end
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# Returns a two-element array containing the [ key-length,
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# block-size ] for the named cipher algorithm. If the cipher
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# algorithm is unknown, or is "none", 0 is returned for both elements
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# of the tuple.
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def self.get_lengths(name)
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ossl_name = SSH_TO_OSSL[name]
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return [0, 0] if ossl_name.nil? || ossl_name == "none"
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cipher = OpenSSL::Cipher::Cipher.new(ossl_name)
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return [cipher.key_len, cipher.block_size]
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end
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private
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# Generate a key value in accordance with the SSH2 specification.
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def self.make_key(bytes, start, options={})
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k = start[0, bytes]
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digester = options[:digester]
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shared = options[:shared]
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hash = options[:hash]
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while k.length < bytes
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step = digester.digest(shared + hash + k)
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bytes_needed = bytes - k.length
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k << step[0, bytes_needed]
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end
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return k
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end
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end
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end; end; end
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