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Static configuration in elasticsearch.yml
Due to the nature of Kerberos, you need to define some (static) settings in
elasticsearch.yml, and some in
elasticsearch.yml, you need to define:
searchguard.kerberos.krb5_filepath: '/etc/krb5.conf' searchguard.kerberos.acceptor_keytab_filepath: 'eskeytab.tab'
searchguard.kerberos.krb5_filepath defines the path to your Kerberos configuration file. This file contains various settings regarding your Kerberos installation, for example, the realm name(s) and the hostname(s) and port(s) of the Kerberos Key Distribution Center services.
searchguard.kerberos.acceptor_keytab_filepath defines the path to the keytab file, containing the principal that Search Guard will use to issue requests against Kerberos/KDC.
acceptor_principal: 'HTTP/localhost' defines the principal that Search Guard will use to issue requests against Kerberos/KDC.
acceptor_principal defines the acceptor/server principal name Search Guard uses to issue requests against Kerberos/KDC. This must be present in the keytab file.
Due to security restrictions the keytab file must be placed in the
<ES installation directory>/conf directory or a subdirectory, and the path in
elasticsearch.yml must be configured relative, not absolute.
Dynamic configuration in sgconfig.yml
A typical Kerberos authentication domain in sgconfig.yml looks like this:
authc: kerberos_auth_domain: http_enabled: true order: 1 http_authenticator: type: kerberos challenge: true config: krb_debug: false strip_realm_from_principal: true authentication_backend: type: noop
Authentication against Kerberos via a browser on HTTP level is achieved by using SPNEGO. The Kerberos/SPNEGO implementations vary, depending on your browser/operating system. This is important when deciding if you need to set the
challenge flag to true or false.
As with HTTP Basic Authentication, this flag determines how Search Guard should react when no
Authorization header is found in the HTTP request, or if this header does not equal
If set to true, Search Guard will send a response with status code 401 and a
WWW-Authenticate header set to
Negotiate. This will tell the client (browser) to resend the request with the
Authorization header set. If set to false, Search Guard cannot extract the credentials from the request, and authentication will fail. Setting
challenge to false thus only makes sense if the Kerberos credentials are sent in the inital request.
As the name implies, setting
krb_debug to true will output a lot of Kerberos specific debugging messages to stdout. Use this if you encounter any problems with your Kerberos integration.
If you set
strip_realm_from_principal to true, Search Guard will strip the realm from the user name.
Since SPNEGO/Kerberos authenticates a user on HTTP level, no additional
authentication_backend is needed, hence it can be set to
krb_debug: true in the dynamic configuration. Now any login attempt with a SPNEGO token should print diagnostic information to stdout.
If you do not see any output or use an older Search Guard Kerberos module set the following JVM porperties manually: