pgpool-II 4.7.2 Documentation
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# 6.2. Authentication Methods

The following subsections describe the authentication methods specified by `pool_hba.conf` in more detail.

## 6.2.1. Trust Authentication

When `trust` authentication is specified, Pgpool-II assumes that anyone who can connect to the server is authorized to access connect with whatever database user name they specify.

## 6.2.2. Clear Text Password Authentication

The method `password` sends the password in clear-text and is therefore vulnerable to password "sniffing" attacks. It should always be avoided if possible. If the connection is protected by SSL encryption then `password` can be used safely, though. For this sake, it is recommended to use `hostssl` in `pool_hba.conf` so that clients are enforced to use SSL encryption.

A benefit to use the method is, the password for authentication is provided by client side and `pool_passwd` is not consulted. So you can avoid maintaining `pool_passwd` file.

You can avoid maintaining `pool_passwd` by using allow_clear_text_frontend_auth as well but it does not enforce to use SSL encryption because `pool_hba.conf` cannot be used with the parameter.

## 6.2.3. MD5 Password Authentication

This authentication method is the password-based authentication methods in which MD-5-hashed password is sent by client. Since Pgpool-II does not has the visibility of PostgreSQL's database user password and client application only sends the MD5-hash of the password, so `md5` authentication in Pgpool-II is supported using the pool_passwd authentication file.

### 6.2.3.1. Authentication file format

To use the `md5` authentication pool_passwd authentication file must contain the user password in either plain text, `AES` or `md5` encrypted format.

The pool_passwd file should contain lines in the following format:

           "username:TEXT_plain_text_passwd"

           "username:AES_encrypted_passwd"

           "username:md5_encrypted_passwd"

(Actually "_" after "TEXT", "AES" or "md5" does not exist.)

### 6.2.3.2. Setting md5 Authentication

here are the steps to enable `md5` authentication:

1- Login as the database's operating system user and type `"pg_md5 --config-file=path_to_pgpool.conf --md5auth --username=username password"` user name and `md5` encrypted password are registered into pool_passwd. If pool_passwd does not exist yet, pg_md5 command will automatically create it for you.

> Note: user name and password must be identical to those registered in PostgreSQL server.

2- Add an appropriate md5 entry to `pool_hba.conf`. See Section 6.1 for more details. If `pool_hba.conf` is not enabled, make sure that md5 authentication is specified in `pg_hba.conf` of PostgreSQL.

3- After changing md5 password (in both pool_passwd and PostgreSQL of course), reload the pgpool configurations.

## 6.2.4. scram-sha-256 Authentication

This authentication method also known as SCRAM is a challenge-response based authentication that prevents the password sniffing on untrusted connections. Since Pgpool-II does not has the visibility of PostgreSQL's database user password, so `SCRAM` authentication is supported using the pool_passwd authentication file.

### 6.2.4.1. Authentication file entry for SCRAM

To use the `SCRAM` authentication pool_passwd authentication file must contain the user password in either plain text or `AES` encrypted format.

           "username:TEXT_plain_text_passwd"

           "username:AES_encrypted_passwd"

(Actually "_" after "TEXT" or "AES" does not exist.)

> Note: `md5` type user passwords in pool_passwd file can't be used for `scram` authentication

### 6.2.4.2. Setting scram-sha-256 Authentication

Here are the steps to enable `scram-sha-256` authentication:

1- Create pool_passwd file entry for database user and password in plain text or `AES` encrypted format. The pg_enc utility that comes with Pgpool-II can be used to create the `AES` encrypted password entries in the pool_passwd file.

> Note: User name and password must be identical to those registered in the PostgreSQL server.

2- Add an appropriate scram-sha-256 entry to `pool_hba.conf`. See Section 6.1 for more details. If `pool_hba.conf` is not enabled, make sure that md5 authentication is specified in `pg_hba.conf` of PostgreSQL.

3- After changing SCRAM password (in both pool_passwd and PostgreSQL of course), reload the Pgpool-II configuration.

## 6.2.5. Certificate Authentication

This authentication method uses `SSL` client certificates to perform authentication. It is therefore only available for SSL connections. When using this authentication method, the Pgpool-II will require that the client provide a valid certificate. No password prompt will be sent to the client. The `cn` (Common Name) attribute of the certificate will be compared to the requested database user name, and if they match the login will be allowed.

> Note: The certificate authentication works between only client and Pgpool-II. The certificate authentication does not work between Pgpool-II and PostgreSQL. For backend authentication you can use any other authentication method.

## 6.2.6. PAM Authentication

This authentication method uses PAM (Pluggable Authentication Modules) as the authentication mechanism. The default PAM service name is `pgpool`. PAM authentication is supported using user information on the host where Pgpool-II is executed. For more information about PAM, please read the Linux-PAM Page.

To enable PAM authentication, you need to create a service-configuration file named for Pgpool-II in the system's PAM configuration directory (which is usually at `"/etc/pam.d"`).

> Note: To enable PAM support the Pgpool-II must be configured with `"--with-pam"`

## 6.2.7. LDAP Authentication

This authentication method uses LDAP as the password certification method. LDAP is used only to validate the user name/password pairs. Therefore the user must already exist in the database before LDAP can be used for authentication.

LDAP authentication can operate in two modes. In the first mode, which we will call the simple bind mode, the server will bind to the distinguished name constructed as `prefix` `username` `suffix`. Typically, the `prefix` parameter is used to specify `cn=`, or `DOMAIN``\` in an Active Directory environment. `suffix` is used to specify the remaining part of the DN in a non-Active Directory environment.

In the second mode, which we will call the search+bind mode, the server first binds to the LDAP directory with a fixed user name and password, specified with `ldapbinddn` and `ldapbindpasswd`, and performs a search for the user trying to log in to the database. If no user and password is configured, an anonymous bind will be attempted to the directory. The search will be performed over the subtree at `ldapbasedn`, and will try to do an exact match of the attribute specified in `ldapsearchattribute`. Once the user has been found in this search, the server disconnects and re-binds to the directory as this user, using the password specified by the client, to verify that the login is correct. This mode is the same as that used by LDAP authentication schemes in other software, such as Apache `mod_authnz_ldap` and `pam_ldap`. This method allows for significantly more flexibility in where the user objects are located in the directory, but will cause two separate connections to the LDAP server to be made.

The following configuration options are used in both modes:

`ldapserver`

  Names or IP addresses of LDAP servers to connect to. Multiple servers may be specified, separated by spaces.

`ldapport`

  Port number on LDAP server to connect to. If no port is specified, the LDAP library's default port setting will be used.

`ldapscheme`

  Set to `ldaps` to use LDAPS. This is a non-standard way of using LDAP over SSL, supported by some LDAP server implementations. See also the `ldaptls` option for an alternative.

`ldaptls`

  Set to 1 to make the connection between Pgpool-II and the LDAP server use TLS encryption. This uses the `StartTLS` operation per RFC 4513. See also the `ldapscheme` option for an alternative.

Note that using `ldapscheme` or `ldaptls` only encrypts the traffic between the Pgpool-II server and the LDAP server. The connection between the Pgpool-II server and the client will still be unencrypted unless SSL is used there as well.

The following options are used in simple bind mode only:

`ldapprefix`

  String to prepend to the user name when forming the DN to bind as, when doing simple bind authentication.

`ldapsuffix`

  String to append to the user name when forming the DN to bind as, when doing simple bind authentication.

The following options are used in search+bind mode only:

`ldapbasedn`

  Root DN to begin the search for the user in, when doing search+bind authentication.

`ldapbinddn`

  DN of user to bind to the directory with to perform the search when doing search+bind authentication.

`ldapbindpasswd`

  Password for user to bind to the directory with to perform the search when doing search+bind authentication.

`ldapsearchattribute`

  Attribute to match against the user name in the search when doing search+bind authentication. If no attribute is specified, the `uid` attribute will be used.

`ldapsearchfilter`

  The search filter to use when doing search+bind authentication. Occurrences of `$username` will be replaced with the user name. This allows for more flexible search filters than `ldapsearchattribute`.

`ldapurl`

  An RFC 4516 LDAP URL. This is an alternative way to write some of the other LDAP options in a more compact and standard form. The format is

      ldap[s]://host[:port]/basedn[?[attribute][?[scope][?[filter]]]]

  `scope` must be one of `base`, `one`, `sub`, typically the last. (The default is `base`, which is normally not useful in this application.) `attribute` can nominate a single attribute, in which case it is used as a value for `ldapsearchattribute`. If `attribute` is empty then `filter` can be used as a value for `ldapsearchfilter`.

  The URL scheme `ldaps` chooses the LDAPS method for making LDAP connections over SSL, equivalent to using `ldapscheme=ldaps`. To use encrypted LDAP connections using the `StartTLS` operation, use the normal URL scheme `ldap` and specify the `ldaptls` option in addition to `ldapurl`.

  For non-anonymous binds, `ldapbinddn` and `ldapbindpasswd` must be specified as separate options.

`backend_use_passwd`

  Set to 1 to make the password used for LDAP authentication use authentication between Pgpool-II and backend.

It is an error to mix configuration options for simple bind with options for search+bind.

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 `ldapsearchfilter`. Specifying `ldapsearchattribute=foo` is equivalent to specifying `ldapsearchfilter="(foo=$username)"`. If neither option is specified the default is `ldapsearchattribute=uid`.

If Pgpool-II was compiled with OpenLDAP as the LDAP client library, the `ldapserver` setting may be omitted. In that case, a list of host names and ports is looked up via RFC 2782 DNS SRV records. The name `_ldap._tcp.DOMAIN` is looked up, where `DOMAIN` is extracted from `ldapbasedn`.

Here is an example for a simple-bind LDAP configuration:

    host ... ldap ldapserver=ldap.example.net ldapprefix="cn=" ldapsuffix=", dc=example, dc=net"

When a connection to the database server as database user `foo` is requested, Pgpool-II will attempt to bind to the LDAP server using the DN `cn=foo, dc=example, dc=net` and the password provided by the client. If that connection succeeds, the database access is granted.

Here is an example for a search+bind configuration:

    host ... ldap ldapserver=ldap.example.net ldapbasedn="dc=example, dc=net" ldapsearchattribute=uid

When a connection to the database server as database user `foo` is requested, Pgpool-II will attempt to bind anonymously (since `ldapbinddn` was not specified) to the LDAP server, perform a search for `(uid=foo)` under the specified base DN. If an entry is found, it will then attempt to bind using that found information and the password supplied by the client. If that second connection succeeds, the database access is granted.

Here is the same search+bind configuration written as a URL:

    host ... ldap ldapurl="ldap://ldap.example.net/dc=example,dc=net?uid?sub"

Some other software that supports authentication against LDAP uses the same URL format, so it will be easier to share the configuration.

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))"

Here is an example for a search+bind configuration that uses DNS SRV discovery to find the host name(s) and port(s) for the LDAP service for the domain name `example.net`:

    host ... ldap ldapbasedn="dc=example,dc=net"

> Tip: Since LDAP often uses commas and spaces to separate the different parts of a DN, it is often necessary to use double-quoted parameter values when configuring LDAP options, as shown in the examples.

> Note: To enable LDAP support the Pgpool-II must be configured with `"--with-ldap"`

## 6.2.8. GSSAPI Authentication

GSSAPI is an industry-standard protocol for secure authentication defined in RFC 2743. Currently Pgpool-II does not support GSSAPI. Clients should not use GSSAPI authentication, or should use "prefer GSSAPI authentication if possible" option (this is the default setting of PostgreSQL clients). If latter is chosen, Pgpool-II requests non-GSSAPI authentication to client, and the clients will fall back to non-GSSAPI authentication method. Thus, usually users do not need to worry about that Pgpool-II does not accept GSSAPI authentication.

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