Movatterモバイル変換

19.3.1. Trust Authentication

19.3.2. Password Authentication

19.3.3. GSSAPI Authentication

19.3.4. SSPI Authentication

19.3.5. Ident Authentication

19.3.6. Peer Authentication

19.3.7. LDAP Authentication

19.3.8. RADIUS Authentication

19.3.9. Certificate Authentication

19.3.10. PAM Authentication

19.3.11. BSD Authentication

Whentrust authentication is specified,Postgres Pro assumes that anyone who can connect to the server is authorized to access the database with whatever database user name they specify (even superuser names). Of course, restrictions made in thedatabase anduser columns still apply. This method should only be used when there is adequate operating-system-level protection on connections to the server.

trust authentication is appropriate and very convenient for local connections on a single-user workstation. It is usuallynot appropriate by itself on a multiuser machine. However, you might be able to usetrust even on a multiuser machine, if you restrict access to the server's Unix-domain socket file using file-system permissions. To do this, set theunix_socket_permissions (and possiblyunix_socket_group) configuration parameters as described inSection 18.3. Or you could set theunix_socket_directories configuration parameter to place the socket file in a suitably restricted directory.

Setting file-system permissions only helps for Unix-socket connections. Local TCP/IP connections are not restricted by file-system permissions. Therefore, if you want to use file-system permissions for local security, remove thehost ... 127.0.0.1 ... line frompg_hba.conf, or change it to a non-trust authentication method.

trust authentication is only suitable for TCP/IP connections if you trust every user on every machine that is allowed to connect to the server by thepg_hba.conf lines that specifytrust. It is seldom reasonable to usetrust for any TCP/IP connections other than those fromlocalhost (127.0.0.1).

The password-based authentication methods aremd5 andpassword. These methods operate similarly except for the way that the password is sent across the connection, namely MD5-hashed and clear-text respectively.

If you are at all concerned about password“sniffing” attacks thenmd5 is preferred. Plainpassword should always be avoided if possible. However,md5 cannot be used with thedb_user_namespace feature. If the connection is protected by SSL encryption thenpassword can be used safely (though SSL certificate authentication might be a better choice if one is depending on using SSL).

Postgres Pro database passwords are separate from operating system user passwords. The password for each database user is stored in thepg_authid system catalog. Passwords can be managed with the SQL commandsCREATE USER andALTER ROLE, e.g.,CREATE USER foo WITH PASSWORD 'secret'. If no password has been set up for a user, the stored password is null and password authentication will always fail for that user.

GSSAPI is an industry-standard protocol for secure authentication defined in RFC 2743.Postgres Pro supportsGSSAPI withKerberos 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 unlessSSL is used.

GSSAPI support has to be enabled whenPostgres Pro Standard is built.

WhenGSSAPI usesKerberos, it uses a standard principal in the formatservicename/hostname@realm. The Postgres Pro server will accept any principal that is included in the keytab used by the server, but care needs to be taken to specify the correct principal details when making the connection from the client using thekrbsrvname connection parameter. (See alsoSection 30.1.2.) The installation default can be changed from the defaultpostgres at build time using./configure --with-krb-srvnam=whatever. 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 can be mapped to differentPostgres Pro database user names withpg_ident.conf. For example,pgusername@realm could be mapped to justpgusername. Alternatively, you can use the fullusername@realm principal as the role name inPostgres Pro without any mapping.

Postgres Pro also supports a parameter to strip the realm from the principal. This method is supported for backwards compatibility and is strongly discouraged as it is then impossible to distinguish different users with the same user name but coming from different realms. To enable this, setinclude_realm to 0. For simple single-realm installations, doing that combined with setting thekrb_realm parameter (which checks that the principal's realm matches exactly what is in thekrb_realm parameter) is still secure; but this is a less capable approach compared to specifying an explicit mapping inpg_ident.conf.

Make sure that your server keytab file is readable (and preferably only readable, not writable) by thePostgres Pro server account. (See alsoSection 17.1.) The location of the key file is specified by thekrb_server_keyfile configuration parameter. The default is/usr/local/pgsql/etc/krb5.keytab (or whatever directory was specified assysconfdir at build time). For security reasons, it is recommended to use a separate keytab just for thePostgres Pro 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.orgkadmin%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 namefred, principalfred@EXAMPLE.COM would be able to connect. To also allow principalfred/users.example.com@EXAMPLE.COM, use a user name map, as described inSection 19.2.

The following configuration options are supported forGSSAPI:

SSPI is aWindows technology for secure authentication with single sign-on.Postgres Pro will use SSPI innegotiate mode, which will useKerberos when possible and automatically fall back toNTLM in other cases.SSPI authentication only works when both server and client are runningWindows, or, on non-Windows platforms, whenGSSAPI is available.

When usingKerberos authentication,SSPI works the same wayGSSAPI does; seeSection 19.3.3 for details.

The following configuration options are supported forSSPI:

The ident authentication method works by obtaining the client's operating system user name from an ident server and using it as the allowed database user name (with an optional user name mapping). This is only supported on TCP/IP connections.

The following configuration options are supported forident:

The“Identification Protocol” is described in RFC 1413. Virtually every Unix-like operating system ships with an ident server that listens on TCP port 113 by default. The basic functionality of an ident server is to answer questions like“What user initiated the connection that goes out of your portX and connects to my portY?”. SincePostgres Pro knows bothX andY when a physical connection is established, it can interrogate the ident server on the host of the connecting client and can theoretically determine the operating system user for any given connection.

The drawback of this procedure is that it depends on the integrity of the client: if the client machine is untrusted or compromised, an attacker could run just about any program on port 113 and return any user name they choose. This authentication method is therefore only appropriate for closed networks where each client machine is under tight control and where the database and system administrators operate in close contact. In other words, you must trust the machine running the ident server. Heed the warning:

Some ident servers have a nonstandard option that causes the returned user name to be encrypted, using a key that only the originating machine's administrator knows. This optionmust not be used when using the ident server withPostgres Pro, sincePostgres Pro does not have any way to decrypt the returned string to determine the actual user name.

The peer authentication method works by obtaining the client's operating system user name from the kernel and using it as the allowed database user name (with optional user name mapping). This method is only supported on local connections.

The following configuration options are supported forpeer:

Peer authentication is only available on operating systems providing thegetpeereid() function, theSO_PEERCRED socket parameter, or similar mechanisms. Currently that includesLinux, most flavors ofBSD includingOS X, andSolaris.

This authentication method operates similarly topassword except that it uses LDAP as the password verification 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 asprefixusernamesuffix. Typically, theprefix parameter is used to specifycn=, orDOMAIN\ 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 withldapbinddn andldapbindpasswd, 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 atldapbasedn, and will try to do an exact match of the attribute specified inldapsearchattribute. 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 Apachemod_authnz_ldap andpam_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:

The following options are used in simple bind mode only:

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

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

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 usersomeuser is requested, Postgres Pro will attempt to bind to the LDAP server using the DNcn=someuser, 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 usersomeuser is requested, Postgres Pro will attempt to bind anonymously (sinceldapbinddn was not specified) to the LDAP server, perform a search for(uid=someuser) 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.

This authentication method operates similarly topassword except that it uses RADIUS as the password verification method. RADIUS is used only to validate the user name/password pairs. Therefore the user must already exist in the database before RADIUS can be used for authentication.

When using RADIUS authentication, an Access Request message will be sent to the configured RADIUS server. This request will be of typeAuthenticate Only, and include parameters foruser name,password (encrypted) andNAS Identifier. The request will be encrypted using a secret shared with the server. The RADIUS server will respond to this server with eitherAccess Accept orAccess Reject. There is no support for RADIUS accounting.

The following configuration options are supported for RADIUS:

This authentication method uses SSL client certificates to perform authentication. It is therefore only available for SSL connections. When using this authentication method, the server will require that the client provide a valid, trusted certificate. No password prompt will be sent to the client. Thecn (Common Name) attribute of the certificate will be compared to the requested database user name, and if they match the login will be allowed. User name mapping can be used to allowcn to be different from the database user name.

The following configuration options are supported for SSL certificate authentication:

In apg_hba.conf record specifying certificate authentication, the authentication optionclientcert is assumed to be1, and it cannot be turned off since a client certificate is necessary for this method. What thecert method adds to the basicclientcert certificate validity test is a check that thecn attribute matches the database user name.

This authentication method operates similarly topassword except that it uses PAM (Pluggable Authentication Modules) as the authentication mechanism. The default PAM service name ispostgresql. PAM is used only to validate user name/password pairs and optionally the connected remote host name or IP address. Therefore the user must already exist in the database before PAM can be used for authentication. For more information about PAM, please read theLinux-PAM Page.

The following configuration options are supported for PAM:

This authentication method operates similarly topassword except that it uses BSD Authentication to verify the password. BSD Authentication is used only to validate user name/password pairs. Therefore the user's role must already exist in the database before BSD Authentication can be used for authentication. The BSD Authentication framework is currently only available on OpenBSD.

BSD Authentication inPostgres Pro uses theauth-postgresql login type and authenticates with thepostgresql login class if that's defined inlogin.conf. By default that login class does not exist, andPostgres Pro will use the default login class.