hosts_access.5 (2010 09)

hosts_access(5) hosts_access(5)

WARNING: Do not set traps on your

finger daemon, unless you are prepared for inﬁnite finger

loops.

Service trapping can be especially useful on network ﬁrewall systems. The typical network ﬁrewall only

provides a limited set of services to the outer world. All other services can be trapped just like the above

tftp example. The result is an excellent early-warning system.

DIAGNOSTICS

Problems are reported via

syslogd, the syslog daemon, at info, notice, warning and err

lev-

els. An error is reported in the following cases:

• When a syntax error is found in a host access control rule,

• When the length of an access control rule exceeds the capacity of an internal buffer,

• When an access control rule is not terminated by a newline character,

• When the result of

%letter expansion would overﬂow an internal buffer,

• When a system call fails that should not.

WARNINGS

If a name server lookup times out, the host name will not be available to the access control software, even

though the host is registered.

Domain name server lookups are not case-sensitive. NIS (formerly YP) netgroup lookups are case-

sensitive.

AUTHOR

Wietse Venema (wietse@wzv.win.tue.nl)

Department of Mathematics and Computing Science

Eindhoven University of Technology

Den Dolech 2, P.O. Box 513,

5600 MB Eindhoven, The Netherlands

FILES

/etc/hosts.allow (daemon,client) pairs that are granted access.

/etc/hosts.deny (daemon,client) pairs that are denied access.