Granados.SSH2.SSH2UserAuthKey.FromSECSHStyleStream C# (CSharp) Method

        public static SSH2UserAuthKey FromSECSHStyleStream(Stream strm, string passphrase)
        {
            StreamReader r = new StreamReader(strm, Encoding.ASCII);
            string l = r.ReadLine();
            if (l == null || l != "---- BEGIN SSH2 ENCRYPTED PRIVATE KEY ----")
                throw new SSHException("Wrong key format");

            string comment = "";
            l = r.ReadLine();
            StringBuilder buf = new StringBuilder();
            while (l != "---- END SSH2 ENCRYPTED PRIVATE KEY ----") {
                if (l.IndexOf(':') == -1)
                    buf.Append(l);
                else if (l[l.Length - 1] == '\\')
                    buf.Append(l, 0, l.Length - 1);
                else if (l.StartsWith("Comment: "))
                    comment = l.Substring("Comment: ".Length);

                l = r.ReadLine();
                if (l == null)
                    throw new SSHException("Key is broken");
            }
            r.Close();

            byte[] keydata = Base64.Decode(Encoding.ASCII.GetBytes(buf.ToString()));
            //Debug.WriteLine(DebugUtil.DumpByteArray(keydata));

            SSH2DataReader re = new SSH2DataReader(keydata);
            int magic = re.ReadInt32();
            if (magic != MAGIC_VAL)
                throw new SSHException("key file is broken");
            int privateKeyLen = re.ReadInt32();
            string type = Encoding.ASCII.GetString(re.ReadString());

            string ciphername = Encoding.ASCII.GetString(re.ReadString());
            int bufLen = re.ReadInt32();
            if (ciphername != "none") {
                CipherAlgorithm algo = CipherFactory.SSH2NameToAlgorithm(ciphername);
                byte[] key = PassphraseToKey(passphrase, CipherFactory.GetKeySize(algo));
                Cipher c = CipherFactory.CreateCipher(SSHProtocol.SSH2, algo, key);
                byte[] tmp = new Byte[re.Image.Length - re.Offset];
                c.Decrypt(re.Image, re.Offset, re.Image.Length - re.Offset, tmp, 0);
                re = new SSH2DataReader(tmp);
            }

            int parmLen = re.ReadInt32();
            if (parmLen < 0 || parmLen > re.Rest)
                throw new SSHException(Strings.GetString("WrongPassphrase"));

            if (type.IndexOf("if-modn") != -1) {
                //mindterm mistaken this order of BigIntegers
                BigInteger e = re.ReadBigIntWithBits();
                BigInteger d = re.ReadBigIntWithBits();
                BigInteger n = re.ReadBigIntWithBits();
                BigInteger u = re.ReadBigIntWithBits();
                BigInteger p = re.ReadBigIntWithBits();
                BigInteger q = re.ReadBigIntWithBits();
                return new SSH2UserAuthKey(new RSAKeyPair(e, d, n, u, p, q), comment);
            }
            else if (type.IndexOf("dl-modp") != -1) {
                if (re.ReadInt32() != 0)
                    throw new SSHException("DSS Private Key File is broken");
                BigInteger p = re.ReadBigIntWithBits();
                BigInteger g = re.ReadBigIntWithBits();
                BigInteger q = re.ReadBigIntWithBits();
                BigInteger y = re.ReadBigIntWithBits();
                BigInteger x = re.ReadBigIntWithBits();
                return new SSH2UserAuthKey(new DSAKeyPair(p, g, q, y, x), comment);
            }
            else
                throw new SSHException("unknown authentication method " + type);
        }