CLIENT USERNAME LOOKUP
When the client host supports the RFC 931 protocol or one of its descendants (TAP, IDENT, RFC 1413) the wrapper programs
can retrieve additional information about the owner of a connection. Client username information, when available, is
logged together with the client host name, and can be used to match patterns like:
daemon_list : ... user_pattern@host_pattern ...
The daemon wrappers can be configured at compile time to perform rule-driven username lookups (default) or to always
interrogate the client host. In the case of rule-driven username lookups, the above rule would cause username lookup
only when both the daemon_list and the host_pattern match.
A user pattern has the same syntax as a daemon process pattern, so the same wildcards apply (netgroup membership is not
supported). One should not get carried away with username lookups, though.
o The client username information cannot be trusted when it is needed most, i.e. when the client system has been
compromised. In general, ALL and (UN)KNOWN are the only user name patterns that make sense.
o Username lookups are possible only with TCP-based services, and only when the client host runs a suitable daemon;
in all other cases the result is "unknown".
o A well-known UNIX kernel bug may cause loss of service when username lookups are blocked by a firewall. The wrap-
per README document describes a procedure to find out if your kernel has this bug.
o Username lookups may cause noticeable delays for non-UNIX users. The default timeout for username lookups is 10
seconds: too short to cope with slow networks, but long enough to irritate PC users.
Selective username lookups can alleviate the last problem. For example, a rule like:
daemon_list : @pcnetgroup ALL@ALL
would match members of the pc netgroup without doing username lookups, but would perform username lookups with all other