Configuring Client Authentication

When a HAWQ system is first initialized, the system contains one predefined superuser role. This role will have the same name as the operating system user who initialized the HAWQ system. This role is referred to as gpadmin. By default, the system is configured to only allow local connections to the database from the gpadmin role. To allow any other roles to connect, or to allow connections from remote hosts, you configure HAWQ to allow such connections.

Allowing Connections to HAWQ

Client access and authentication is controlled by the standard PostgreSQL host-based authentication file, pg_hba.conf. In HAWQ, the pg_hba.conf file of the master instance controls client access and authentication to your HAWQ system. HAWQ segments have pg_hba.conf files that are configured to allow only client connections from the master host and never accept client connections. Do not alter the pg_hba.conf file on your segments.

See The pg_hba.conf File in the PostgreSQL documentation for more information.

The general format of the pg_hba.conf file is a set of records, one per line. HAWQ ignores blank lines and any text after the # comment character. A record consists of a number of fields that are separated by spaces and/or tabs. Fields can contain white space if the field value is quoted. Records cannot be continued across lines. Each remote client access record has the following format:

host|hostssl|hostnossl   <database>   <role>   <CIDR-address>|<IP-address>,<IP-mask>   <authentication-method>

Each UNIX-domain socket access record has the following format:

local   <database>   <role>   <authentication-method>

The following table describes meaning of each field.

Editing the pg_hba.conf File

This example shows how to edit the pg_hba.conf file of the master to allow remote client access to all databases from all roles using encrypted password authentication.

Note: For a more secure system, consider removing all connections that use trust authentication from your master pg_hba.conf. Trust authentication means the role is granted access without any authentication, therefore bypassing all security. Replace trust entries with ident authentication if your system has an ident service available.

Editing pg_hba.conf

1. Obtain the master data directory location from the hawq_master_directory property value in hawq-site.xml and use a text editor to open the pg_hba.conf file in this directory.

2. Add a line to the file for each type of connection you want to allow. Records are read sequentially, so the order of the records is significant. Typically, earlier records will have tight connection match parameters and weaker authentication methods, while later records will have looser match parameters and stronger authentication methods. For example:

   # allow the gpadmin user local access to all databases
   # using ident authentication
   local   all   gpadmin   ident         sameuser
   host    all   gpadmin   127.0.0.1/32  ident
   host    all   gpadmin   ::1/128       ident
   # allow the 'dba' role access to any database from any
   # host with IP address 192.168.x.x and use md5 encrypted
   # passwords to authenticate the user
   # Note that to use SHA-256 encryption, replace *md5* with
   # password in the line below
   host    all   dba   192.168.0.0/32  md5
   # allow all roles access to any database from any
   # host and use ldap to authenticate the user. HAWQ role
   # names must match the LDAP common name.
   host    all   all   192.168.0.0/32  ldap ldapserver=usldap1
   ldapport=1389 ldapprefix="cn="
   ldapsuffix=",ou=People,dc=company,dc=com"
   

3. Save and close the file.

4. Reload the pg_hba.confconfiguration file for your changes to take effect. Include the -M fast option if you have active/open database connections:

   $ hawq stop cluster -u [-M fast]
   

Limiting Concurrent Connections

HAWQ allocates some resources on a per-connection basis, so setting the maximum number of connections allowed is recommended.

To limit the number of active concurrent sessions to your HAWQ system, you can configure the max_connections server configuration parameter on the master instance or the seg_max_connections server configuration parameter on segments.

When you set max_connections, you can also set the value for the maximum concurrent connections for the segments by using seg_max_connections.

Example $GPHOME/etc/hawq-site.xml configuration:

  <property>
      <name>max_connections</name>
      <value>1280</value>
  </property>
  <property>
      <name>seg_max_connectionss</name>
      <value>3000</value>
  </property>

HAWQ is configured to allow a maximum of 1280 concurrent user connections on the master and 3000 connections on a segment. For best practices, the recommended value for seg_max_connections is its default value of 3000.

Note: Raising the values of these parameters may cause HAWQ to request more shared memory. To mitigate this effect, consider decreasing other memory-related server configuration parameters such as gp_cached_segworkers_threshold.

Setting the number of allowed connections

You will perform different procedures to set connection-related server configuration parameters for your HAWQ cluster depending upon whether you manage your cluster from the command line or use Ambari. If you use Ambari to manage your HAWQ cluster, you must ensure that you update server configuration parameters only via the Ambari Web UI. If you manage your HAWQ cluster from the command line, you will use the hawq config command line utility to set server configuration parameters.

If you use Ambari to manage your cluster:

1. Set the max_connections and seg_max_connections configuration properties via the HAWQ service Configs > Advanced > Custom hawq-site drop down.
2. Select Service Actions > Restart All to load the updated configuration.

If you manage your cluster from the command line:

1. Log in to the HAWQ master host as a HAWQ administrator and source the file /usr/local/hawq/greenplum_path.sh.

   $ source /usr/local/hawq/greenplum_path.sh
   

2. Use the hawq config utility to set the values of the max_connections and seg_max_connections parameters to values appropriate for your deployment. For example:

   $ hawq config -c max_connections -v 1280
   $ hawq config -c seg_max_connections -v 3000
   

3. Load the new configuration values by restarting your HAWQ cluster:

   $ hawq restart cluster
   

4. Use the -s option to hawq config to display server configuration parameter values:

   $ hawq config -s max_connections
   

Encrypting Client/Server Connections

Enable SSL for client connections to HAWQ to encrypt the data passed over the network between the client and the database.

HAWQ has native support for SSL connections between the client and the master server. SSL connections prevent third parties from snooping on the packets, and also prevent man-in-the-middle attacks. SSL should be used whenever the client connection goes through an insecure link, and must be used whenever client certificate authentication is used.

Enabling SSL requires that OpenSSL be installed on both the client and the master server systems. HAWQ can be started with SSL enabled by setting the server configuration parameter ssl to on in the master hawq-site.xml. When starting in SSL mode, the server will look for the files server.key (server private key) and server.crt (server certificate) in the master data directory. These files must be set up correctly before an SSL-enabled HAWQ system can start.

Important: Do not protect the private key with a passphrase. The server does not prompt for a passphrase for the private key, and the database startup fails with an error if one is required.

A self-signed certificate can be used for testing, but a certificate signed by a certificate authority (CA) should be used in production, so the client can verify the identity of the server. Either a global or local CA can be used. If all the clients are local to the organization, a local CA is recommended.

Creating a Self-signed Certificate without a Passphrase for Testing Only

To create a quick self-signed certificate for the server for testing, use the following OpenSSL command:

# openssl req -new -text -out server.req

Enter the information requested by the prompts. Be sure to enter the local host name as Common Name. The challenge password can be left blank.

The program will generate a key that is passphrase protected, and does not accept a passphrase that is less than four characters long.

To use this certificate with HAWQ, remove the passphrase with the following commands:

# openssl rsa -in privkey.pem -out server.key
# rm privkey.pem

Enter the old passphrase when prompted to unlock the existing key.

Then, enter the following command to turn the certificate into a self-signed certificate and to copy the key and certificate to a location where the server will look for them.

# openssl req -x509 -in server.req -text -key server.key -out server.crt

Finally, change the permissions on the key with the following command. The server will reject the file if the permissions are less restrictive than these.

# chmod og-rwx server.key

For more details on how to create your server private key and certificate, refer to the OpenSSL documentation.