Lightweight Third Party Authentication

LTPA is intended for distributed, multiple application server and machine environments.

LTPA supports forwardable credentials and single signon (SSO).

LTPA can support security in a distributed environment through cryptography, which permits LTPA to encrypt, digitally sign, and securely transmit authentication-related data, and later decrypt and verify the signature.

Application servers distributed in multiple nodes and cells can securely communicate using the LTPA protocol. It also provides the SSO feature wherein a user is required to authenticate only once in a DNS domain and can access resources in other WebSphere Application Server cells without getting prompted. The realm names on each system in the DNS domain are case sensitive and must match identically.

For iSeries, for local OS, the realm name is the domain name, if a domain is in use or the realm name is the machine name.

For Windows, for local OS, the realm name is the same as the host name.

For UNIX, for the LDAP, the realm name is the host:port value of the LDAP server.

The LTPA protocol uses cryptographic keys to encrypt and decrypt user data that passes between the servers. These keys need to be shared between the different cells for the resources in one cell to access resources in other cells, assuming that all the cells involved use the same LDAP or custom registry.

When using LTPA, a token is created with the user information and an expiration time and is signed by the keys. The LTPA token is time sensitive. All product servers participating in a protection domain must have their time, date, and time zone synchronized. If not, LTPA tokens appear prematurely expired and cause authentication or validation failures.

This token passes to other servers, in the same cell or in a different cell through cookies (for Web resources when SSO is enabled) or through the authentication layer (Security Authentication Service (SAS) or Common Secure Interoperability Version 2 (CSIv2) for enterprise beans).

If the receiving servers share the same keys as the originating server, the token can be decrypted to obtain the user information, which then is validated to make sure that it has not expired and that the user information in the token is valid in its registry. On successful validation, the resources in the receiving servers are accessible after the authorization check.

All of the WebSphere Application Server processes in a cell (cell, nodes, application servers) share the same set of keys. If key sharing is required between different cells, export them from one cell and import them to the other. For security purposes, the exported keys are encrypted with a user-defined password. This same password is needed when importing the keys into another cell.

WebSphere Application Server supports the LTPA and the Integrated Cryptographic Services Facility (ICSF) protocols.

When security is enabled for the first time with LTPA, configuring LTPA is normally the initial step performed.

LTPA requires that the configured user registry be a centrally shared repository such as LDAP or a Windows domain-type registry so that users and groups are the same, regardless of the machine.

The following table summarizes the authentication mechanism capabilities and user registries with which LTPA can work.

Forwardable credentials SSO Local OS user registry LDAP user registry Custom user registry

LTPA Yes Yes Yes Yes Yes
ICSF Yes Yes Yes Yes Yes

	Forwardable credentials	SSO	Local OS user registry	LDAP user registry	Custom user registry
LTPA	Yes	Yes	Yes	Yes	Yes
ICSF	Yes	Yes	Yes	Yes	Yes

Note: The use of LTPA with the LocalOS user registry is only applicable to configurations where all servers reside on the same iSeries system.

Related concepts

Trust associations
Single signon

Authentication mechanisms