SSH Support in Direct Mode

In This Topic

SSH connection is established between client and SSH server. SSH server in turn communicates with Oracle in an unencrypted mode. This is called SSH tunneling. A benefit of SSH tunneling is that it allows you to connect to a Oracle server from behind a firewall when the Oracle server port is blocked. Oracle server does not need to be attuned for this type of connection and functions as usual. To connect to Oracle server a client must first be authorized on SSH server.

dotConnect for Oracle supports both connecting to Oracle Cloud and on-premises Oracle servers using SSH in the Direct mode.

Setting Up SSH Connection

To enable using SSH, you need to add the ssh:// prefix to the Host connection string parameter. Note also that the Host parameter must be set as if you are connecting from the computer with the SSH Server installed. Thus, if they are installed on the same computer, you need to set the Host parameter to ssh://localhost and specify the host domain name or address in the SSH Host connection string parameter.

OracleConnection.SshOptions property points to object that holds all information necessary to connect to SSH server. Alternatively, you may specify the corresponding parameters in the connection string. Here is brief explanation on what you have to specify in this object:

Property	Connection String Parameter	Meaning
SshOptions.AuthenticationType	SSH Authentication Type	Client authentication methods
SshOptions.CipherList	SSH Cipher List	List of ciphers that client agrees to use, by colons.
SshOptions.Host	SSH Host	Name or ip address of SSH server
SshOptions.Passphrase	SSH Passphrase	Passphrase for the client key
SshOptions.Password	SSH Password	User password on SSH server
SshOptions.Port	SSH Port	Number of port on SSH server to connect
SshOptions.PrivateKey	SSH Private Key	Location of private key to use.
SshOptions.User	SSH User	User id on SSH server

Locations of private key can be specified in three ways:

As file in the system: file://C:\Temp\client.key
As item of certificate store: storage://Name.Id (examples RSA.Client.key or DSA.Client.key)
As compiled resource: resource://client.key
Loaded to memory, using MemCryptStorage class: memory://key_id

The property SshOptions.CipherList contains the list of the ciphers that client agrees to use, separated by colons. By default it is empty, which means that client agrees to use any of available ciphers. The appropriate values for the CipherList property are listed below, highlighted in bold.

dotConnect for Oracle supports two modes of block ciphering: Cipher-block chaining (CBC) and Counter (CTR). The following ciphers are available for SSH connections in the CBC mode:

3DES or 3DES(168) - Triple Data Encryption Algorithm. Key size 168 bits.
Blowfish - Symmetric-key block cipher, designed in 1993 by Bruce Schneier. Key size 128 bits.
AES(128) - Advanced Encryption Standard. Key size 128 bits.
AES(192) - Advanced Encryption Standard. Key size 192 bits.
AES or AES(256) - Advanced Encryption Standard. Key size 256 bits.

In the CTR mode the AES ciphers are used.

AES(128)-CTR - Advanced Encryption Standard. Key size 128 bits.
AES(192)-CTR - Advanced Encryption Standard. Key size 192 bits.
AES-CTR or AES(256)-CTR - Advanced Encryption Standard. Key size 256 bits.

      // Password Authentication
      OracleConnection myConn = new OracleConnection("Direct=True;Host=ssh://localhost;Port=1521;Service Name=orcl;User ID=scott;Password=tiger;");
      myConn.SshOptions.AuthenticationType = SshAuthenticationType.Password;
      myConn.SshOptions.User = "sshUser";
      myConn.SshOptions.Host = "OracleSSH";
      myConn.SshOptions.Password = "sshPassword";
      OracleCommand myCommand = new OracleCommand("select count(*) from dept", myConn);
      myConn.Open();
      Int64 count = Convert.ToInt64(myCommand.ExecuteScalar());
      Console.WriteLine(count);
      myConn.Close();

      // Public Key Authentication
      OracleConnection myConn = new OracleConnection("Direct=True;Host=ssh://localhost;Port=1521;Service Name=orcl;User ID=scott;Password=tiger;");
      myConn.SshOptions.AuthenticationType = SshAuthenticationType.PublicKey;
      myConn.SshOptions.User = "sshUser";
      myConn.SshOptions.Host = "sshServer";
      myConn.SshOptions.PrivateKey = "E:\\WORK\\client.key";
      OracleCommand myCommand = new OracleCommand("select count(*) from dept", myConn);
      myConn.Open();
      Int64 count = Convert.ToInt64(myCommand.ExecuteScalar());
      Console.WriteLine(count);
      myConn.Close();

Visual Basic


	    ' Password Authentication
	    Dim myConn As OracleConnection = New OracleConnection("Direct=True;Host=ssh://localhost;Port=1521;Service Name=orcl;User ID=scott;Password=tiger;")
	    myConn.SshOptions.AuthenticationType = SshAuthenticationType.Password
	    myConn.SshOptions.User = "sshUser"
	    myConn.SshOptions.Host = "sshServer"
	    myConn.SshOptions.Password = "sshPassword"
	    Dim myCommand As OracleCommand = New OracleCommand("select count(*) from dept", myConn)
	    myConn.Open()
	    Dim count As Int64 = Convert.ToInt64(myCommand.ExecuteScalar())
	    Console.WriteLine(count)
	    myConn.Close()

	    ' Public Key Authentication
	    Dim myConn As OracleConnection = New OracleConnection("Direct=True;Host=ssh://localhost;Port=1521;Service Name=orcl;User ID=scott;Password=tiger;")
	    myConn.SshOptions.AuthenticationType = SshAuthenticationType.PublicKey
	    myConn.SshOptions.User = "sshUser"
	    myConn.SshOptions.Host = "sshServer"
	    myConn.SshOptions.PrivateKey = "E:\WORK\client.key"
	    Dim myCommand As OracleCommand = New OracleCommand("select count(*) from dept", myConn)
	    myConn.Open()
	    Dim count As Int64 = Convert.ToInt64(myCommand.ExecuteScalar())
	    Console.WriteLine(count)
	    myConn.Close()

Setting Up SSH Connection

See Also