gpfdists:// Protocol

gpfdists:// Protocol

The gpfdists:// protocol is a secure version of the gpfdist:// protocol.

To use it, you run the gpfdist utility with the --ssl option. When specified in a URI, the gpfdists:// protocol enables encrypted communication and secure identification of the file server and the Greenplum Database to protect against attacks such as eavesdropping and man-in-the-middle attacks.

gpfdists implements SSL security in a client/server scheme with the following attributes and limitations:
  • Client certificates are required.
  • Multilingual certificates are not supported.
  • A Certificate Revocation List (CRL) is not supported.
  • The TLSv1 protocol is used with the TLS_RSA_WITH_AES_128_CBC_SHA encryption algorithm.
  • SSL parameters cannot be changed.
  • SSL renegotiation is supported.
  • The SSL ignore host mismatch parameter is set to false.
  • Private keys containing a passphrase are not supported for the gpfdist file server (server.key) and for the Greenplum Database (client.key).
  • Issuing certificates that are appropriate for the operating system in use is the user's responsibility. Generally, converting certificates as shown in https://www.sslshopper.com/ssl-converter.html is supported.
    Note: A server started with the gpfdist --ssl option can only communicate with the gpfdists protocol. A server that was started with gpfdist without the --ssl option can only communicate with the gpfdist protocol.
  • The client certificate file, client.crt
  • The client private key file, client.key
Use one of the following methods to invoke the gpfdists protocol.
  • Run gpfdist with the --ssl option and then use the gpfdists protocol in the LOCATION clause of a CREATE EXTERNAL TABLE statement.
  • Use a gpload YAML control file with the SSL option set to true. Running gpload starts the gpfdist server with the --ssl option, then uses the gpfdists protocol.

Using gpfdists requires that the following client certificates reside in the $PGDATA/gpfdists directory on each segment.

  • The client certificate file, client.crt
  • The client private key file, client.key
  • The trusted certificate authorities, root.crt

For an example of loading data into an external table security, see Example 3—Multiple gpfdists instances.

The server configuration parameter verify_gpfdists_cert controls whether SSL certificate authentication is enabled when Greenplum Database communicates with the gpfdist utility to either read data from or write data to an external data source. You can set the parameter value to false to disable authentication when testing the communication between the Greenplum Database external table and the gpfdist utility that is serving the external data. If the value is false, these SSL exceptions are ignored:
  • The self-signed SSL certificate that is used by gpfdist is not trusted by Greenplum Database.
  • The host name contained in the SSL certificate does not match the host name that is running gpfdist.
Warning: Disabling SSL certificate authentication exposes a security risk by not validating the gpfdists SSL certificate.