Implements a factory of OpenSSL cipher algorithms.
Constants
| SSH_TO_OSSL | = | { "3des-cbc" => "des-ede3-cbc", "blowfish-cbc" => "bf-cbc", "aes256-cbc" => "aes-256-cbc", "aes192-cbc" => "aes-192-cbc", "aes128-cbc" => "aes-128-cbc", "idea-cbc" => "idea-cbc", "cast128-cbc" => "cast-cbc", "rijndael-cbc@lysator.liu.se" => "aes-256-cbc", "arcfour128" => "rc4", "arcfour256" => "rc4", "arcfour512" => "rc4", "none" => "none" } | Maps the SSH name of a cipher to it’s corresponding OpenSSL name | |
| KEY_LEN_OVERRIDE | = | { "arcfour256" => 32, "arcfour512" => 64 } | Ruby’s OpenSSL bindings always return a key length of 16 for RC4 ciphers resulting in the error: OpenSSL::CipherError: key length too short. The following ciphers will override this key length. |
Public class methods
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 45 45: def self.get(name, options={}) 46: ossl_name = SSH_TO_OSSL[name] or raise NotImplementedError, "unimplemented cipher `#{name}'" 47: return IdentityCipher if ossl_name == "none" 48: 49: cipher = OpenSSL::Cipher::Cipher.new(ossl_name) 50: cipher.send(options[:encrypt] ? :encrypt : :decrypt) 51: 52: cipher.padding = 0 53: cipher.iv = make_key(cipher.iv_len, options[:iv], options) if ossl_name != "rc4" 54: key_len = KEY_LEN_OVERRIDE[name] || cipher.key_len 55: cipher.key_len = key_len 56: cipher.key = make_key(key_len, options[:key], options) 57: cipher.update(" " * 1536) if ossl_name == "rc4" 58: 59: return cipher 60: end
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.
# File lib/net/ssh/transport/cipher_factory.rb, line 66 66: def self.get_lengths(name) 67: ossl_name = SSH_TO_OSSL[name] 68: return [0, 0] if ossl_name.nil? || ossl_name == "none" 69: 70: cipher = OpenSSL::Cipher::Cipher.new(ossl_name) 71: key_len = KEY_LEN_OVERRIDE[name] || cipher.key_len 72: cipher.key_len = key_len 73: 74: return [key_len, ossl_name=="rc4" ? 8 : cipher.block_size] 75: end
Returns true if the underlying OpenSSL library supports the given cipher, and false otherwise.
# File lib/net/ssh/transport/cipher_factory.rb, line 34 34: def self.supported?(name) 35: ossl_name = SSH_TO_OSSL[name] or raise NotImplementedError, "unimplemented cipher `#{name}'" 36: return true if ossl_name == "none" 37: return OpenSSL::Cipher.ciphers.include?(ossl_name) 38: end