shishi_realm_for_server_dns3

Arguments

Shishi * handle

Shishi library handle created by shishi_init().

char * server

Hostname to find realm for.

Overview

Finds the realm for a host server using DNS lookup, as is prescribed in "draft-ietf-krb-wg-krb-dns-locate-03.txt".

Since DNS lookup can be spoofed, relying on the realm information may result in a redirection attack. In a single-realm scenario, this only achieves a denial of service, but with trust across multiple realms the attack may redirect you to a compromised realm. For this reason, Shishi prints a warning, suggesting that the user should instead add a proper 'server-realm' configuration token.

To illustrate the DNS information used, here is an extract from a zone file for the domain ASDF.COM:

_kerberos.asdf.com. IN TXT "ASDF.COM" _kerberos.mrkserver.asdf.com. IN TXT "MARKETING.ASDF.COM" _kerberos.salesserver.asdf.com. IN TXT "SALES.ASDF.COM"

Let us suppose that in this case, a client wishes to use a service on the host "foo.asdf.com". It would first query for

_kerberos.foo.asdf.com. IN TXT

Finding no match, it would then query for

_kerberos.asdf.com. IN TXT

With the resource records stated above, the latter query returns a positive answer.

Return value

Returns realm for the indicated host, or NULL if no relevant TXT record could be found.