Manual Pages for UNIX Darwin command on man hosts

Manual Pages for UNIX Darwin command on man hosts_options

HOSTSOPTIONS(5) HOSTSOPTIONS(5)

NAME

hostsoptions - host access control language extensions

DESCRIPTION

This document describes optional extensions to the language described in the hostsaccess(5) document. The extensions are enabled at program build time. For example, by editing the Makefile and turning on the

PROCESSOPTIONS compile-time option. These extensions are enabled on

Mac OS X. The extensible language uses the following format: daemonlist : clientlist : option : option ... The first two fields are described in the hostsaccess(5) manual page. The remainder of the rules is a list of zero or more options. Any ":" characters within options should be protected with a backslash.

An option is of the form "keyword" or "keyword value". Options are pro-

cessed in the specified order. Some options are subjected to %

substitutions. For the sake of backwards compatibility with earlier versions, an "=" is permitted between keyword and value. LLOOGGGGIINNGG severity mail.info severity notice Change the severity level at which the event will be logged.

Facility names (such as mail) are optional, and are not sup-

ported on systems with older syslog implementations. The sever-

ity option can be used to emphasize or to ignore specific events. AACCCCEESSSS CCOONNTTRROOLL allow deny Grant (deny) service. These options must appear at the end of a rule. The allow and deny keywords make it possible to keep all access control rules within a single file, for example in the hosts.allow file. To permit access from specific hosts only: ALL: .friendly.domain: ALLOW ALL: ALL: DENY To permit access from all hosts except a few trouble makers: ALL: .bad.domain: DENY ALL: ALL: ALLOW Notice the leading dot on the domain name patterns. RRUUNNNNIINNGG OOTTHHEERR CCOOMMMMAANNDDSS spawn shellcommand Execute, in a child process, the specified shell command, after

performing the % expansions described in the

hostsaccess(5) manual page. The command is executed with stdin, stdout and stderr connected to the null device, so that it won't mess up the conversation with the client host. Example:

spawn (/some/where/safefinger -l @%h | /usr/ucb/mail root) &

executes, in a background child process, the shell command

"safefinger -l @%h | mail root" after replacing %h by the name

or address of the remote host.

The example uses the "safefinger" command instead of the regu-

lar "finger" command, to limit possible damage from data sent by

the finger server. The "safefinger" command is part of the dae-

mon wrapper package; it is a wrapper around the regular finger command that filters the data sent by the remote host. twist shellcommand Replace the current process by an instance of the specified

shell command, after performing the % expansions

described in the hostsaccess(5) manual page. Stdin, stdout and stderr are connected to the client process. This option must appear at the end of a rule. To send a customized bounce message to the client instead of running the real ftp daemon: in.ftpd : ... : twist /bin/echo 421 Some bounce message

For an alternative way to talk to client processes, see the ban-

ners option below.

To run /some/other/in.telnetd without polluting its command-line

array or its process environment: in.telnetd : ... : twist PATH=/some/other; exec in.telnetd Warning: in case of UDP services, do not twist to commands that

use the standard I/O or the read(2)/write(2) routines to commu-

nicate with the client process; UDP requires other I/O primi-

tives. NNEETTWWOORRKK OOPPTTIIOONNSS keepalive Causes the server to periodically send a message to the client. The connection is considered broken when the client does not respond. The keepalive option can be useful when users turn off their machine while it is still connected to a server. The keepalive option is not useful for datagram (UDP) services. linger numberofseconds

Specifies how long the kernel will try to deliver not-yet deliv-

ered data after the server process closes a connection.

USERNAME LOOKUP

rfc931 [ timeoutinseconds ] Look up the client user name with the RFC 931 (TAP, IDENT, RFC

1413) protocol. This option is silently ignored in case of ser-

vices based on transports other than TCP. It requires that the

client system runs an RFC 931 (IDENT, etc.) -compliant daemon,

and may cause noticeable delays with connections from non-UNIX

clients. The timeout period is optional. If no timeout is spec-

ified a compile-time defined default value is taken.

MMIISSCCEELLLLAANNEEOOUUSS banners /some/directory Look for a file in `/some/directory' with the same name as the daemon process (for example in.telnetd for the telnet service), and copy its contents to the client. Newline characters are

replaced by carriage-return newline, and % sequences are

expanded (see the hostsaccess(5) manual page). The tcp wrappers source code distribution provides a sample makefile (Banners.Makefile) for convenient banner maintenance.

Warning: banners are supported for connection-oriented (TCP)

network services only. nice [ number ] Change the nice value of the process (default 10). Specify a positive value to spend more CPU resources on other processes. setenv name value Place a (name, value) pair into the process environment. The

value is subjected to % expansions and may contain

whitespace (but leading and trailing blanks are stripped off). Warning: many network daemons reset their environment before spawning a login or shell process. umask 022 Like the umask command that is built into the shell. An umask of 022 prevents the creation of files with group and world write permission. The umask argument should be an octal number. user nobody user nobody.kmem Assume the privileges of the "nobody" userid (or user "nobody",

group "kmem"). The first form is useful with inetd implementa-

tions that run all services with root privilege. The second form is useful for services that need special group privileges only. DIAGNOSTICS When a syntax error is found in an access control rule, the error is reported to the syslog daemon; further options will be ignored, and service is denied.