Hi Danh,
Crystal Reports 2008 SP7 supports Oracle 12 c.
Have a look at the document: SAP Crystal Reports 2008 SP7 for Windows - Supported Platforms
For Native connectivity: You need to install Oracle Client 12.1 (32 bit) on the client machine.
For JDBC, download JAR file: http://www.oracle.com/technetwork/database/features/jdbc/jdbc-drivers-12c-download-1958347.html
For more details on JDBC visit a URL: JDBC Connectivity for SAP Crystal Reports
Thanks,
Nilesh