Describes the available methods for authenticating Greenplum Database clients.
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: Greenplum Database Security Configuration Guide
Client access and authentication is controlled by a configuration file named
pg_hba.conf (the standard PostgreSQL host-based authentication file). 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 coordinator instance controls client access and authentication to your Greenplum system. The segments also have
pg_hba.conf files, but these are already correctly configured to only allow client connections from the coordinator 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. Blank lines are ignored, as is any text after a # comment character. A record is made up of a number of fields which are separated by spaces and/or tabs. Fields can contain white space if the field value is quoted. Records cannot be continued across lines.
A record can have one of seven formats:
local <database> <user> <auth-method> [<auth-options>] host <database> <user> <address> <auth-method> [<auth-options>] hostssl <database> <user> <address> <auth-method> [<auth-options>] hostnossl <database> <user> <address> <auth-method> [<auth-options>] host <database> <user> <IP-address> <IP-mask> <auth-method> [<auth-options>] hostssl <database> <user> <IP-address> <IP-mask> <auth-method> [<auth-options>] hostnossl <database> <user> <IP-address> <IP-mask> <auth-method> [<auth-options>]
The meaning of the
pg_hba.conf fields is as follows:
listen_addressesserver configuration parameter. Greenplum Database by default allows connections from all hosts (
sslconfiguration parameter to on. Requires SSL authentication be configured in
postgresql.conf. See Configuring postgresql.conf for SSL Authentication.
allspecifies that it matches all databases. Multiple database names can be supplied by separating them with commas. A separate file containing database names can be specified by preceding the file name with
allspecifies that it matches all roles. If the specified role is a group and you want all members of that group to be included, precede the role name with a
+. Multiple role names can be supplied by separating them with commas. A separate file containing role names can be specified by preceding the file name with
An IP address range is specified using standard numeric notation for the range’s starting address, then a slash (
/) and a CIDR mask length. The mask length indicates the number of high-order bits of the client IP address that must match. Bits to the right of this should be zero in the given IP address. There must not be any white space between the IP address, the
/, and the CIDR mask length.
Typical examples of an IPv4 address range specified this way are
172.20.143.89/32 for a single host, or
172.20.143.0/24 for a small network, or
10.6.0.0/16 for a larger one. An IPv6 address range might look like
::1/128 for a single host (in this case the IPv6 loopback address) or
fe80::7a31:c1ff:0000:0000/96 for a small network.
0.0.0.0/0 represents all IPv4 addresses, and
::0/0 represents all IPv6 addresses. To specify a single host, use a mask length of 32 for IPv4 or 128 for IPv6. In a network address, do not omit trailing zeroes.
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.
Entries in IPv6 format will be rejected if the host system C library does not have support for IPv6 addresses.
You can also write
all to match any IP address,
samehost to match any of the server’s own IP addresses, or
samenet to match any address in any subnet to which the server is directly connected.
If a host name is specified (an address that is not an IP address, IP range, or special key word 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.
The host name that is used in
pg_hba.conf should be the one that address-to-name resolution of the client’s IP address returns, otherwise the line won’t be matched. Some host name databases allow associating an IP address with multiple host names, but the operating system will only return one host name when asked to resolve an IP address.
A host name specification that starts with a dot (.) matches a suffix of the actual host name. So
.example.com would match
foo.example.com (but not just
When host names are specified in
pg_hba.conf, you should ensure that name resolution is reasonably fast. It can be advantageous to set up a local name resolution cache such as
nscd. Also, you can enable the server configuration parameter
log_hostname to see the client host name instead of the IP address in the log.
255.0.0.0represents an IPv4 CIDR mask length of 8, and
255.255.255.255represents a CIDR mask length of 32.
auth-methodfield, there can be field(s) of the form
name=valuethat specify options for the authentication method. Details about which options are available for which authentication methods are described in Authentication Methods.
Files included by @ constructs are read as lists of names, which can be separated by either whitespace or commas. Comments are introduced by #, just as in
pg_hba.conf, and nested @ constructs are allowed. Unless the file name following @ is an absolute path, it is taken to be relative to the directory containing the referencing file.
pg_hba.conf records are examined sequentially for each connection attempt, 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, you might wish to use
trust authentication for local TCP/IP connections but require a password for remote TCP/IP connections. In this case a record specifying
trust authentication for connections from 127.0.0.1 would appear before a record specifying
password authentication for a wider range of allowed client IP addresses.
pg_hba.conf file is read on start-up and when the main server process receives a SIGHUP signal. If you edit the file on an active system, you must reload the file using this command:
$ gpstop -u
CAUTION: For a more secure system, remove records for remote connections that use
trust authentication from the
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 could install an ident service on the coordinator host and then use
ident authentication for local TCP connections, for example
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.
Greenplum Command Center provides an interface for editing the
pg_hba.conffile. It verifies entries before you save them, keeps a version history of the file so that you can reload a previous version of the file, and reloads the file into Greenplum Database.
This example shows how to edit the
pg_hba.conf file on the coordinator host to allow remote client access to all databases from all roles using encrypted password authentication.
$MASTER_DATA_DIRECTORY/pg_hba.confin a text editor.
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
gpadminrole, and for Greenplum utilities (for example
gpstartamongst others) that need to connect between nodes without prompting for input or a password.
For a more secure system, remove records for remote connections that use
trustauthentication from the
trustauthentication grants any user who can connect to the server access to the database using any role they specify. You can safely replace
identauthentication for local UNIX-socket connections. You can also use
identauthentication for local and remote TCP clients, but the client host must be running an ident service and you must
trustthe integrity of that machine.
identfor TCP connections from remote hosts requires that the client’s host is running an ident service. The
identauthentication method should only be used with remote hosts on a trusted, closed network.
The password-based authentication methods are
password. These methods operate similarly except for the way that the password is sent across the connection: MD5-hashed and clear-text respectively.
If you are at all concerned about password “sniffing” attacks then
md5 is preferred. Plain
password should always be avoided if possible. If the connection is protected by SSL encryption then
password can be used safely (although SSL certificate authentication might be a better choice if you are depending on using SSL).
Following are some sample
pg_hba.conf basic authentication entries:
hostnossl all all 0.0.0.0 reject hostssl all testuser 0.0.0.0/0 md5 local all gpuser ident
local all gpadmin ident host all gpadmin localhost trust host all gpadmin cdw trust local replication gpadmin ident host replication gpadmin samenet trust host all all 0.0.0.0/0 md5
GSSAPI is an industry-standard protocol for secure authentication defined in RFC 2743. Greenplum Database supports GSSAPI with Kerberos authentication according to RFC 1964. GSSAPI provides automatic authentication (single sign-on) for systems that support it. The authentication itself is secure, but the data sent over the database connection will be sent unencrypted unless SSL is used.
gss authentication method is only available for TCP/IP connections.
When GSSAPI uses Kerberos, it uses a standard principal in the format
servicename/hostname@realm. The Greenplum Database server will accept any principal that is included in the keytab file used by the server, but care needs to be taken to specify the correct principal details when making the connection from the client using the
krbsrvname connection parameter. (See Connection Parameter Key Words in the PostgreSQL documentation.) In most environments, this parameter never needs to be changed. Some Kerberos implementations might require a different service name, such as Microsoft Active Directory, which requires the service name to be in upper case (POSTGRES).
hostname is the fully qualified host name of the server machine. The service principal’s realm is the preferred realm of the server machine.
Client principals must have their Greenplum Database user name as their first component, for example
gpusername@realm. Alternatively, you can use a user name mapping to map from the first component of the principal name to the database user name. By default, Greenplum Database does not check the realm of the client. If you have cross-realm authentication enabled and need to verify the realm, use the
krb_realm parameter, or enable
include_realm and use user name mapping to check the realm.
Make sure that your server keytab file is readable (and preferably only readable) by the
gpadmin server account. The location of the key file is specified by the krb_server_keyfile configuration parameter. For security reasons, it is recommended to use a separate keytab just for the Greenplum Database server rather than opening up permissions on the system keytab file.
The keytab file is generated by the Kerberos software; see the Kerberos documentation for details. The following example is for MIT-compatible Kerberos 5 implementations:
kadmin% **ank -randkey postgres/server.my.domain.org** kadmin% **ktadd -k krb5.keytab postgres/server.my.domain.org**
When connecting to the database make sure you have a ticket for a principal matching the requested database user name. For example, for database user name
fred@EXAMPLE.COM would be able to connect. To also allow principal
fred/users.example.com@EXAMPLE.COM, use a user name map, as described in User Name Maps in the PostgreSQL documentation.
The following configuration options are supported for GSSAPI:
username@EXAMPLE.COM(or, less commonly,
username/hostbased@EXAMPLE.COM), the default user name used for mapping is
username/hostbased, respectively), unless
include_realmhas been set to 1 (as recommended, see above), in which case
username/hostbased@EXAMPLE.COM) is what is seen as the system username when mapping.
You can authenticate against an LDAP directory.
LDAPCONFenvironment variable with the path to the
ldap.conffile and add this to the
Following are the recommended steps for configuring your system for LDAP authentication:
pg_hba.conffile in the
$MASTER_DATA_DIRECTORYto use LDAP as the authentication method for the respective users. Note that the first entry to match the user/role in the
pg_hba.conffile will be used as the authentication mechanism, so the position of the entry in the file is important.
pg_hba.confconfiguration settings to take effect (
Specify the following parameter
$usernamewill be replaced with the user name. This allows for more flexible search filters than
ldapsearchattribute. Note that you can specify either
ldapsearchattribute, but not both.
When using search+bind mode, the search can be performed using a single attribute specified with
ldapsearchattribute, or using a custom search filter specified with
ldapsearchattribute=foo is equivalent to specifying
ldapsearchfilter="(foo=$username)". If neither option is specified the default is
Here is an example for a search+bind configuration that uses
ldapsearchfilter instead of
ldapsearchattribute to allow authentication by user ID or email address:
host ... ldap ldapserver=ldap.example.net ldapbasedn="dc=example, dc=net" ldapsearchfilter="(|(uid=$username)(mail=$username))"
Following are additional sample
pg_hba.conf file entries for LDAP authentication:
host all testuser 0.0.0.0/0 ldap ldap ldapserver=ldapserver.greenplum.com ldapport=389 ldapprefix="cn=" ldapsuffix=",ou=people,dc=greenplum,dc=com" hostssl all ldaprole 0.0.0.0/0 ldap ldapserver=ldapserver.greenplum.com ldaptls=1 ldapprefix="cn=" ldapsuffix=",ou=people,dc=greenplum,dc=com"
SSL authentication compares the Common Name (cn) attribute of an SSL certificate provided by the connecting client during the SSL handshake to the requested database user name. The database user should exist in the database. A map file can be used for mapping between system and database user names.
: This is specified in the
pg_ident.conf, or in the file specified in the
ident_file server setting.
Following are sample
pg_hba.conf entries for SSL client authentication:
Hostssl testdb certuser 192.168.0.0/16 cert Hostssl testdb all 192.168.0.0/16 cert map=gpuser
You can make changes to the OpenSSL configuration by updating the
openssl.cnf file under your OpenSSL installation directory, or the file referenced by
$OPENSSL_CONF, if present, and then restarting the Greenplum Database server.
A self-signed certificate can be used for testing, but a certificate signed by a certificate authority (CA) (either one of the global CAs or a local one) should be used in production so that clients can verify the server’s identity. If all the clients are local to the organization, using a local CA is recommended.
To create a self-signed certificate for the server:
Enter the following
openssl req -new -text -out server.req
Enter the requested information at the prompts.
Make sure you enter the local host name for the Common Name. The challenge password can be left blank.
The program generates a key that is passphrase-protected; it does not accept a passphrase that is less than four characters long. To remove the passphrase (and you must if you want automatic start-up of the server), run the following command:
openssl rsa -in privkey.pem -out server.key rm privkey.pem
Enter the old passphrase to unlock the existing key. Then run the following command:
openssl req -x509 -in server.req -text -key server.key -out server.crt
This turns the certificate into a self-signed certificate and copies the key and certificate to where the server will look for them.
Finally, run the following command:
chmod og-rwx server.key
For more details on how to create your server private key and certificate, refer to the OpenSSL documentation.
The following Server settings need to be specified in the
postgresql.conf configuration file:
sslboolean. Enables SSL connections.
ssl_renegotiation_limitinteger. Specifies the data limit before key renegotiation.
ssl_ciphers string. Configures the list SSL ciphers that are allowed.
ssl_ciphers overrides any ciphers string specified in
/etc/openssl.cnf. The default value
ALL:!ADH:!LOW:!EXP:!MD5:@STRENGTH enables all ciphers except for ADH, LOW, EXP, and MD5 ciphers, and prioritizes ciphers by their strength.
> Note With TLS 1.2 some ciphers in MEDIUM and HIGH strength still use NULL encryption (no encryption for transport), which the default
ssl_ciphers string allows. To bypass NULL ciphers with TLS 1.2 use a string such as
It is possible to have authentication without encryption overhead by using
NULL-MD5 ciphers. However, a man-in-the-middle could read and pass communications between client and server. Also, encryption overhead is minimal compared to the overhead of authentication. For these reasons, NULL ciphers should not be used.
The default location for the following SSL server files is the Greenplum Database coordinator data directory (
server.crt- Server certificate.
server.key- Server private key.
root.crt- Trusted certificate authorities.
root.crl- Certificates revoked by certificate authorities.
If Greenplum Database coordinator mirroring is enabled with SSL client authentication, the SSL server files should not be placed in the default directory
$MASTER_DATA_DIRECTORY. If a
gpinitstandby operation is performed, the contents of
$MASTER_DATA_DIRECTORY is copied from the coordinator to the standby coordinator and the incorrect SSL key, and cert files (the coordinator files, and not the standby coordinator files) will prevent standby coordinator start up.
You can specify a different directory for the location of the SSL server files with the
The client connection parameters can be set using the following environment variables:
For example, run the following command to connect to the
postgres database from
localhost and verify the certificate present in the default location under
psql "sslmode=verify-ca host=localhost dbname=postgres"
The “PAM” (Pluggable Authentication Modules) authentication method validates username/password pairs, similar to basic authentication. To use PAM authentication, the user must already exist as a Greenplum Database role name.
Greenplum uses the
pamservice authentication parameter to identify the service from which to obtain the PAM configuration.
If PAM is set up to read
/etc/shadow, authentication will fail because the PostgreSQL server is started by a non-root user. This is not an issue when PAM is configured to use LDAP or another authentication method.
Greenplum Database does not install a PAM configuration file. If you choose to use PAM authentication with Greenplum, you must identify the PAM service name for Greenplum and create the associated PAM service configuration file and configure Greenplum Database to use PAM authentication as described below:
Log in to the Greenplum Database coordinator host and set up your environment. For example:
$ ssh gpadmin@<gpmaster> gpadmin@gpmaster$ . /usr/local/greenplum-db/greenplum_path.sh
pamservice name for Greenplum Database. In this procedure, we choose the name
Create the PAM service configuration file,
/etc/pam.d/greenplum, and add the text below. You must have operating system superuser privileges to create the
/etc/pam.d directory (if necessary) and the
greenplum PAM configuration file.
#%PAM-1.0 auth include password-auth account include password-auth
This configuration instructs PAM to authenticate the local operating system user.
Ensure that the
/etc/pam.d/greenplum file is readable by all users:
sudo chmod 644 /etc/pam.d/greenplum
Add one or more entries to the
pg_hba.conf configuration file to enable PAM authentication in Greenplum Database. These entries must specify the
pam auth-method. You must also specify the
pamservice=greenplum auth-option. For example:
host <user-name> <db-name> <address> pam pamservice=greenplum
Reload the Greenplum Database configuration:
$ gpstop -u
RADIUS (Remote Authentication Dial In User Service) authentication works by sending an Access Request message of type ‘Authenticate Only’ to a configured RADIUS server. It includes parameters for user name, password (encrypted), and the Network Access Server (NAS) Identifier. The request is encrypted using the shared secret specified in the
radiussecret option. The RADIUS server responds with either
Access Accept or
RADIUS accounting is not supported.
RADIUS authentication only works if the users already exist in the database.
The RADIUS encryption vector requires SSL to be enabled in order to be cryptographically strong.
Following are sample
pg_hba.conf entries for RADIUS client authentication:
hostssl all all 0.0.0.0/0 radius radiusserver=servername radiussecret=sharedsecret
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 coordinator, the standby coordinator, and each segment instance (primary and mirror). The value of
max_connections on segments must be 5-10 times the value on the coordinator.
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 coordinator, and segment instances should be set to the same value as the coordinator.
$MASTER_DATA_DIRECTORY/postgresql.conf (including standby coordinator):
SEGMENT_DATA_DIRECTORY/postgresql.conf for all segment instances:
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
To change the number of allowed connections:
Stop your Greenplum Database system:
On the coordinator host, edit
$MASTER_DATA_DIRECTORY/postgresql.conf and change the following two parameters:
max_connections– the number of active user sessions you want to allow plus the number of
max_prepared_transactions– must be greater than or equal to
SEGMENT_DATA_DIRECTORY/postgresql.confand change the following two parameters:
max_connections– must be 5-10 times the value on the coordinator.
max_prepared_transactions– must be equal to the value on the coordinator.
Restart your Greenplum Database system:
Greenplum Database has native support for SSL connections between the client and the coordinator 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.
For information about encrypting data between the
gpfdistserver and Greenplum Database segment hosts, see Encrypting gpfdist Connections.
To enable SSL requires that OpenSSL be installed on both the client and the coordinator server systems. Greenplum can be started with SSL enabled by setting the server configuration parameter
ssl=on in the coordinator
postgresql.conf. When starting in SSL mode, the server will look for the files
server.key (server private key) and
server.crt (server certificate) in the coordinator data directory. These files must be set up correctly before an SSL-enabled Greenplum system can start.
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. See Creating a Self-Signed Certificate for steps to create a self-signed certificate.