This topic explains how to configure client connections and authentication for Greenplum Database.
When a Greenplum Database 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 Greenplum Database 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. If you want to allow any other roles to connect, or if you want to allow connections from remote hosts, you have to configure Greenplum Database to allow such connections. This section explains how to configure client connections and authentication to Greenplum Database.
Parent topic: Managing Greenplum Database Access
Client access and authentication is controlled by the standard PostgreSQL host-based authentication file, pg_hba.conf. For detailed information about this file, see The pg_hba.conf File in the PostgreSQL documentation.
In Greenplum Database, the pg_hba.conf file of the master instance controls client access and authentication to your Greenplum Database system. The Greenplum Database segments also have pg_hba.conf files, but these are already correctly configured to allow only client connections from the master host. The segments never accept outside client connections, so there is no need to alter the
pg_hba.conf file on segments.
The general format of the pg_hba.conf file is a set of records, one per line. Greenplum Database ignores blank lines and any text after the
# comment character. A record consists of a number of fields that are separated by spaces 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 database role address authentication-method
Each UNIX-domain socket access record is in this format:
local database role authentication-method
The following table describes meaning of each field.
|local||Matches connection attempts using UNIX-domain sockets. Without a record of this type, UNIX-domain socket connections are disallowed.|
|host||Matches connection attempts made using TCP/IP. Remote TCP/IP connections will not be possible unless the server is started with an appropriate value for the
|hostssl||Matches connection attempts made using TCP/IP, but only when the connection is made with SSL encryption. SSL must be enabled at server start time by setting the
|hostnossl||Matches connection attempts made over TCP/IP that do not use SSL.|
|database||Specifies which database names this record matches. The value
|role||Specifies which database role names this record matches. The value
|address||Specifies the client machine addresses that this record matches. This field can contain an IP address, an IP address range, or a host name.
An IP address range is specified using standard numeric notation for the range’s starting address, then a slash (
Typical examples of an IPv4 address range specified this way are
An entry given in IPv4 format will match only IPv4 connections, and an entry given in IPv6 format will match only IPv6 connections, even if the represented address is in the IPv4-in-IPv6 range.
Note: Entries in IPv6 format will be rejected if the host system C library does not have support for IPv6 addresses.
If a host name is specified (an address that is not an IP address or IP range is treated as a host name), that name is compared with the result of a reverse name resolution of the client IP address (for example, reverse DNS lookup, if DNS is used). Host name comparisons are case insensitive. If there is a match, then a forward name resolution (for example, forward DNS lookup) is performed on the host name to check whether any of the addresses it resolves to are equal to the client IP address. If both directions match, then the entry is considered to match.
Some host name databases allow associating an IP address with multiple host names, but the operating system only returns one host name when asked to resolve an IP address. The host name that is used in
When host names are specified in
|These fields can be used as an alternative to the CIDR address notation. Instead of specifying the mask length, the actual mask is specified in a separate column. For example,
|authentication-method||Specifies the authentication method to use when connecting. Greenplum supports the authentication methods supported by PostgreSQL 9.4.|
CAUTION: For a more secure system, consider removing records for remote connections that use trust authentication from the
pg_hba.conf file. Trust authentication grants any user who can connect to the server access to the database using any role they specify. You can safely replace trust authentication with ident authentication for local UNIX-socket connections. You can also use ident authentication for local and remote TCP clients, but the client host must be running an ident service and you must trust the integrity of that machine.
pg_hba.conf file is set up with generous permissions for the gpadmin user and no database access for other Greenplum Database roles. You will need to edit the
pg_hba.conf file to enable users’ access to databases and to secure the gpadmin user. Consider removing entries that have trust authentication, since they allow anyone with access to the server to connect with any role they choose. For local (UNIX socket) connections, use ident authentication, which requires the operating system user to match the role specified. For local and remote TCP connections, ident authentication requires the client’s host to run an indent service. You can install an ident service on the master host and then use ident authentication for local TCP connections, for example
127.0.0.1/28. Using ident authentication for remote TCP connections is less secure because it requires you to trust the integrity of the ident service on the client’s host.
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.
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. Greenplum 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"
Save and close the file.
Reload the pg_hba.conf configuration file for your changes to take effect:
$ gpstop -u
Note that you can also control database access by setting object privileges as described in Managing Object Privileges. The pg_hba.conf file just controls who can initiate a database session and how those connections are authenticated.
Greenplum Database 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 Greenplum Database system, you can configure the
max_connections server configuration parameter. This is a local parameter, meaning that you must set it in the
postgresql.conf file of the master, the standby master, and each segment instance (primary and mirror). The recommended value of
max_connections on segments is 5-10 times the value on the master.
When you set
max_connections, you must also set the dependent parameter
max_prepared_transactions. This value must be at least as large as the value of
max_connections on the master, and segment instances should be set to the same value as the master.
$MASTER_DATA_DIRECTORY/postgresql.conf (including standby master):
SEGMENT_DATA_DIRECTORY/postgresql.conf for all segment instances:
The following steps set the parameter values with the Greenplum Database utility
For information about
gpconfig, see the Greenplum Database Utility Guide.
Set the value of the
max_connections parameter. This
gpconfig command sets the value on the segments to 1000 and the value on the master to 200.
$ gpconfig -c max_connections -v 1000 -m 200
The value on the segments must be greater than the value on the master. The recommended value of
max_connections on segments is 5-10 times the value on the master.
Set the value of the
max_prepared_transactions parameter. This
gpconfig command sets the value to 200 on the master and all segments.
$ gpconfig -c max_prepared_transactions -v 200
The value of
max_prepared_transactions must be greater than or equal to
max_connections on the master.
Stop and restart your Greenplum Database system.
$ gpstop -r
You can check the value of parameters on the master and segments with the
-s option. This
gpconfig command displays the values of the
$ gpconfig -s max_connections
Raising the values of these parameters may cause Greenplum Database to request more shared memory. To mitigate this effect, consider decreasing other memory-related parameters such as
Enable SSL for client connections to Greenplum Database to encrypt the data passed over the network between the client and the database.
Greenplum Database 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 Greenplum Database in SSL mode requires the following items.
The SSL files server.key (server private key) and server.crt (server certificate) should be correctly generated for the master host and standby master host.
Ensure that Greenplum Database can access server.key and server.crt, and any additional authentication files such as
root.crt (for trusted certificate authorities). When starting in SSL mode, the Greenplum Database master looks for server.key and server.crt. As the default, Greenplum Database does not start if the files are not in the master data directory (
$MASTER_DATA_DIRECTORY). Also, if you use other SSL authentication files such as
root.crt (trusted certificate authorities), the files must be on the master host.
If Greenplum Database master mirroring is enabled with SSL client authentication, SSL authentication files must be on both the master host and standby master host and should not be placed in the default directory
$MASTER_DATA_DIRECTORY. When master mirroring is enabled, an
initstandby operation copies the contents of the
$MASTER_DATA_DIRECTORY from the master to the standby master and the incorrect SSL key, and cert files (the master files, and not the standby master files) will prevent standby master start up.
You can specify a different directory for the location of the SSL server files with the
sslcrl. For more information about the parameters, see SSL Client Authentication in the Security Configuration Guide.
Greenplum Database can be started with SSL enabled by setting the server configuration parameter
ssl=on in the
postgresql.conf file on the master and standby master hosts. This
gpconfig command sets the parameter:
gpconfig -c ssl -m on -v off
Setting the parameter requires a server restart. This command restarts the system:
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 Greenplum Database, 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.