10 Proxy Authentication

About Proxy Authentication

Proxy authentication is the process of using a middletier for user authentication. You can design a middletier server to proxy clients in a secure fashion by using the following three forms of proxy authentication:

• The middletier server authenticates itself with the database server and a client. In this case, an application user or another application, authenticates itself with the middletier server. Client identities can be maintained all the way through to the database.

• The client, that is, a database user, is not authenticated by the middletier server. The client's identity and database password are passed through the middletier server to the database server for authentication.

• The client, that is, a global user, is authenticated by the middletier server, and passes either a Distinguished name (DN) or a Certificate through the middle tier for retrieving the client's user name.

  Note:

  Operations done on behalf of a client by a middletier server can be audited. For more information, refer to Oracle Database Security Guide.

  See Also:

  "Creating Proxy Connections"

In all cases, an administrator must authorize the middletier server to proxy a client, that is, to act on behalf of the client. Suppose, the middletier server initially connects to the database as user scott and activates a proxy connection as user jeff, and then issues the following statement to authorize the middletier server to proxy a client:

ALTER USER jeff GRANT CONNECT THROUGH scott;

You can also:

• Specify roles that the middle tier is permitted to activate when connecting as the client. For example,

  CREATE ROLE role1; 
  GRANT SELECT ON emp TO role1;
  ALTER USER jeff GRANT CONNECT THROUGH scott ROLE role1;
  

  The role clause limits the access only to those database objects that are mentioned in the list of the roles. The list of roles can be empty.

• Find the users who are currently authorized to connect through a middle tier by querying the PROXY_USERS data dictionary view.

• Disallow a proxy connection by using the REVOKE CONNECT THROUGH clause of ALTER USER statement.

You need to use the different fields and methods present in the oracle.jdbc.OracleConnection interface to set up the different types of proxy connections.

Types of Proxy Connections

You can create proxy connections using any one of the following options:

• USER NAME

  This is done by supplying the user name or the password or both. The SQL statement for specifying authentication using password is:

  ALTER USER jeff GRANT CONNECT THROUGH scott AUTHENTICATED USING password;
  

  In this case, jeff is the user name and scott is the proxy for jeff.

  The password option exists for additional security. Having no authenticated clause implies default authentication, which is using only the user name without the password. The SQL statement for specifying default authentication is:

  ALTER USER jeff GRANT CONNECT THROUGH scott
  

• DISTINGUISHED NAME

  This is a global name in lieu of the password of the user being proxied for. An example of the corresponding SQL statement using a distinguished name is:

  CREATE USER jeff IDENTIFIED GLOBALLY AS 'CN=jeff,OU=americas,O=oracle,L=redwoodshores,ST=ca,C=us';
  

  The string that follows the identified globally as clause is the distinguished name. It is then necessary to authenticate using this distinguished name. The corresponding SQL statement to specify authentication using distinguished name is:

  ALTER USER jeff GRANT CONNECT THROUGH scott AUTHENTICATED USING DISTINGUISHED NAME;
  

• CERTIFICATE

  This is a more encrypted way of passing the credentials of the user, who is to be proxied, to the database. The certificate contains the distinguished name encoded in it. One way of generating the certificate is by creating a wallet and then decoding the wallet to get the certificate. The wallet can be created using runutl mkwallet. It is then necessary to authenticate using the generated certificate. The SQL statement for specifying authentication using certificate is:

  ALTER USER jeff GRANT CONNECT THROUGH scott AUTHENTICATED USING CERTIFICATE;
  

  Note:

  The use of certificates for proxy authentication will be desupported in future Oracle Database releases.

Creating Proxy Connections

A user, say jeff, has to connect to the database through another user, say scott. The proxy user, scott, should have an active authenticated connection. A proxy session is then created on this active connection, with the driver issuing a command to the server to create a session for the user, jeff. The server returns the new session ID, and the driver sends a session switch command to switch to this new session.

The JDBC OCI and Thin driver switch sessions in the same manner. The drivers permanently switch to the new session, jeff. As a result, the proxy session, scott, is not available until the new session, jeff, is closed.

A new proxy session is opened by using the following method from the oracle.jdbc.OracleConnection interface:

void openProxySession(int type, java.util.Properties prop) throws SQLExceptionOpens

Where,

type is the type of the proxy session and can have the following values:

• OracleConnection.PROXYTYPE_USER_NAME

  This type is used for specifying the user name.

• OracleConnection.PROXYTYPE_DISTINGUISHED_NAME

  This type is used for specifying the distinguished name of the user.

• OracleConnection.PROXYTYPE_CERTIFICATE

  This type is used for specifying the proxy certificate.

prop is the property value of the proxy session and can have the following values:

• PROXY_USER_NAME

  This property value should be used with the type OracleConnection.PROXYTYPE_USER_NAME. The value should be a java.lang.String.

• PROXY_DISTINGUISHED_NAME

  This property value should be used with the type OracleConnection.PROXYTYPE_DISTINGUISHED_NAME. The value should be a java.lang.String.

• PROXY_CERTIFICATE

  This property value should be used with the type OracleConnection.PROXYTYPE_CERTIFICATE. The value is a bytep[] array that contains the certificate.

• PROXY_ROLES

  This property value can be used with the following types:

  • OracleConnection.PROXYTYPE_USER_NAME

  • OracleConnection.PROXYTYPE_DISTINGUISHED_NAME

  • OracleConnection.PROXYTYPE_CERTIFICATE

  The value should be a java.lang.String.

• PROXY_SESSION

  This property value is used with the close method to close the proxy session.

  See Also:

  Closing a Proxy Session

• PROXY_USER_PASSWORD

  This property value should be used with the type OracleConnection.PROXYTYPE_USER_NAME. The value should be a java.lang.String.

The following code snippet shows the use of the openProxySession method:

java.util.Properties prop = new java.util.Properties();
    prop.put(OracleConnection.PROXY_USER_NAME, "jeff");
    String[] roles = {"role1", "role2"};
    prop.put(OracleConnection.PROXY_ROLES, roles);
    conn.openProxySession(OracleConnection.PROXYTYPE_USER_NAME, prop);
    

Closing a Proxy Session

You can close the proxy session opened with the OracleConnection.openProxySession method by passing the OracleConnection.PROXY_SESSION parameter to the OracleConnection.close method in the following way:

OracleConnection.close(OracleConnection.PROXY_SESSION);

This is similar to closing a proxy session on a non-cached connection. The standard close method must be called explicitly to close the connection itself. If the close method is called directly, without closing the proxy session, then both the proxy session and the connection are closed. This can be achieved in the following way:

OracleConnection.close(OracleConnection.INVALID_CONNECTION);

Caching Proxy Connections

Proxy connections, like standard connections, can be cached. Caching proxy connections enhances the performance. To cache a proxy connection, you need to create a connection using one of the getConnection methods on a cache enabled OracleDataSource object.

A proxy connection may be cached in the connection cache using the connection attributes feature of the connection cache. Connection attributes are name/value pairs that are user-defined and help tag a connection before returning it to the connection cache for reuse. When the tagged connection is retrieved, it can be directly used without having to do a round-trip to create or close a proxy session. Implicit connection cache supports caching of any user/password authenticated connection. Therefore, any user authenticated proxy connection can be cached and retrieved.

It is recommended that proxy connections should not be closed without applying the connection attributes. If a proxy connection is closed without applying the connection attributes, the connection is returned to the connection cache for reuse, but cannot be retrieved. The connection caching mechanism does not remember or reset session state.

A proxy connection can be removed from the connection cache by closing the connection directly.

Limitations of Proxy Connections

Closing a proxy connection automatically closes every SQL Statement created by the proxy connection, during the proxy session or prior to the proxy session. This may cause unexpected consequences on application pooling or statement caching. The following code samples explain this limitation of proxy connections:

Example 1

....
public void displayName(String N)  // Any function using the Proxy feature
{
     Properties props = new Properties();
     props.put("PROXY_USER_NAME", proxyUser);
     c.openProxySession(OracleConnection.PROXYTYPE_USER_NAME, props);
     .......
     c.close(OracleConnection.PROXY_SESSION);
}
 
public static void main (String args[]) throws SQLException
{
    ............
    PreparedStatement pstmt = conn.prepareStatement("SELECT empname FROM EMP WHERE empno = ?");
    pstmt.setString(1, "28959");
    ResultSet rs = pstmt.executeQuery();
    while (rs.next())
    {
        displayName(rs.getString(1));
         if (rs.isClosed() // The ResultSet is already closed while closing the connection!
         {
             throw new Exception("Your ResultSet has been prematurely closed! 
Your Statement object is also dead now.");
         }
    }
}

In the preceding example, when you close the proxy connection in the displayName method, then the PreparedStatement object and the ResultSet object also get closed. So, if you do not check the status of the ResultSet object inside loop, then the loop will fail when the next method is called for the second time.

Example 2

....
    PreparedStatement pstmt = conn.prepareStatement("SELECT empname FROM EMP WHERE empno = ?");
    pstmt.setString(1, "28959");
    ResultSet rs = pstmt.executeQuery();
    while (rs.next())
    {
        ....
    }
 
    Properties props = new Properties();
    props.put("PROXY_USER_NAME", proxyUser);
 
    conn.openProxySession(OracleConnection.PROXYTYPE_USER_NAME, props);
    .......
    conn.close(OracleConnection.PROXY_SESSION);
 
    // Try to use the PreparedStatement again
    pstmt.setString(1, "28960");
// This line of code will fail because the Statement is already closed while closing the connection!
    rs = pstmt.executeQuery(); 

In the preceding example, the PreparedStatement object and the ResultSet object work fine before opening the proxy connection. But, if you try to execute the same PreparedStatement object after closing the proxy connection, then the statement fails.