File Formats HOSTSOPTIONS(4)
NAME
hostsoptions - host access control language extensions
DESCRIPTION
This document describes optional extensions to the language
described in the hostsaccess(4) document. The extensions
are enabled at program build time. For example, by editing
the Makefile and turning on the PROCESOPTIONS compile-time
option.
The extensible language uses the following format:
daemonlist : clientlist : option : option ...
The first two fields are described in the hostsaccess(4)
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 processed 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.
LOGING
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 supported on systems with older syslog imple-
mentations. The severity option can be used to
emphasize or to ignore specific events.
ACES CONTROL
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:
AL: .friendly.domain: ALOW
AL: AL: DENY
To permit access from all hosts except a few trouble makers:
SunOS 5.10 Last change: 1
File Formats HOSTSOPTIONS(4)
AL: .bad.domain: DENY
AL: AL: ALOW
Notice the leading dot on the domain name patterns.
RUNING OTHER COMANDS
spawn shellcommand
Execute, in a child process, the specified shell com-
mand, after performing the % expansions
described in the hostsaccess(4) manual page. The com-
mand is executed with stdin, stdout and stderr con-
nected 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 com-
mand "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 regular "finger" command, to limit possible damage
from data sent by the finger server. The "safefinger"
command is part of the daemon 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(4) 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 banners 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 com-
mands that use the standard I/O or the read(2)/write(2)
routines to communicate with the client process; UDP
requires other I/O primitives.
SunOS 5.10 Last change: 2
File Formats HOSTSOPTIONS(4)
NETWORK OPTIONS
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 delivered data after the server process closes a
connection.
USERNAME LOKUP
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 services 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 specified a compile-time defined default value is
taken.
MISCELANEOUS
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 new-
line, and % sequences are expanded (see the
hostsaccess(4) 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 environ-
ment. The value is subjected to % expansions
and may contain whitespace (but leading and trailing
blanks are stripped off).
SunOS 5.10 Last change: 3
File Formats HOSTSOPTIONS(4)
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 implementations 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.
SEE ALSO
hostsaccess(4), the default access control language
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
ATRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
ATRIBUTE TYPE ATRIBUTE VALUE
Availability SUNWtcpd
Interface Stability Committed
NOTES
Source for tcpwrappers is available in the SUNWtcpdS pack-
age.
SunOS 5.10 Last change: 4
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