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INNBIND(8)		  InterNetNews Documentation		    INNBIND(8)

NAME
       innbind - Helper	program	to bind	sockets	to privileged ports

SYNOPSIS
       innbind [-p] fd,family,address,port [...]

DESCRIPTION
       innbind is a helper program that's not meant to be run directly.
       Instead,	innd and nnrpd use it internally to bind to ports that require
       root privileges to bind to.

       This program must be installed setuid root in order for innd or nnrpd
       to bind to ports	under 1024.  The only functions	that it's willing to
       perform are to bind an open file	descriptor to a	given address and port
       or to create a new socket, bind it, and return the bound	socket to its
       caller.	It can only be run as the news user (as	specified at configure
       time), and will only bind to ports 119, 433, 563, an additional port
       specified with the --with-innd-port argument to configure, or ports
       numbered	1024 or	higher.

       Each argument to	innbind	must be	a comma-separated list of four
       elements.  The first is the file	descriptor number that should be
       bound, the second is the	numeric	family of the socket (AF_INET or
       AF_INET6), the third is the local address to bind to (in	dotted-quad
       format for IPv4 and in colon-separated address format for IPv6),	and
       the fourth is the port number.  To bind to all addresses	with IPv4, use
       0.0.0.0 as the address.	To bind	to all addresses with IPv6, use	"::"
       as the address.

       Multiple	arguments can be specified to tell innbind to bind multiple
       sockets at the same time.  Any errors (other than permission denied
       -- see below) encountered will cause innbind to abort, and error
       messages	will be	sent both to syslog and	to standard error.

       By default, innbind attempts to just bind the already open file
       descriptor that it inherits from	its caller.  For each successfully
       bound file descriptor (in the order given on the	command	line), innbind
       prints "ok" and a newline to its	standard output.

       On some systems (apparently just	STREAMS-based systems),	however, even
       a setuid	root program cannot bind a socket to a privileged port that
       was created by a	process	that didn't have permissions.  If innbind gets
       permission denied when trying to	bind a socket, it will print "no" and
       a newline to its	standard output.  It will then create a	new socket,
       bind it as specified, and then attempt to pass that socket back to its
       caller using the	I_SENDFD STREAMS ioctl.	 The caller should receive
       that file descriptor with I_RECVFD and use it instead of	the one	that
       it created.

       Note that file descriptor passing is only supported on STREAMS-based
       systems since it	is done	with ioctls over a pipe.  However, it is
       believed	that those systems are exactly the systems that	can't simply
       bind the	inherited file descriptor.  If this assumption proves to be
       incorrect, traditional BSD file descriptor passing over a Unix domain
       socket will have	to be added.

OPTIONS
       -p  If given as the first command-line argument,	no attempt will	be
	   made	to bind	the inherited file descriptor and innbind will only
	   try creation	of a new file descriptor and passing it	back via
	   standard output.  This option is primarily useful for testing.

SECURITY
       As innbind is normally installed	setuid root, security is even more of
       an issue	for it than for	other parts of INN.  It	is a fairly short
       program,	and if you understand C, you are encouraged to audit it
       yourself	to be certain that it does only	what it	is supposed to do.
       The only	INN library functions it uses are the vector functions,	the
       message functions for error reporting, and xstrdup.

       The ports that will be bound are	restricted to prevent potential
       attacks made possible by	the ability to bind low-numbered ports,	such
       as exploits of the rsh(1) family	of commands on some systems.  If
       innbind is installed setuid root, it can	only be	executed by the	news
       user to prevent other users on the system from being able to bind to
       even those few privileged ports that it allows.

       innbind uses no external	configuration files; the only files it might
       open are	through	the system getpwnam(3) service to get the UID of the
       news user.  The only user input that it accepts are its command-line
       arguments.

DIAGNOSTICS
       innbind may log the following messages to syslog	and print them to
       standard	error.

       cannot create socket for	%s: %s
	   (Fatal) innbind fell	back on	attempting to create a new socket to
	   bind	for the	given argument,	and the	socket creation	failed.

       cannot bind socket for %s: %s
	   (Fatal) Calling bind	for the	socket corresponding to	the given
	   argument failed with	a system error.	 If the	error indicates
	   permission denied, make sure	that innbind is	setuid root.  This can
	   also	be caused by trying to use IPv6	on a system whose kernel does
	   not support it.

       cannot bind to restricted port %hu in %s
	   (Fatal) The port number portion of the given	command-line argument
	   is for a port below 1024 which is not 119, 433, 563,	or a port
	   given to --with-innd-port at	configure time.	 Other ports are not
	   allowed for security	reasons.

       cannot get socket options for file descriptor %d: %s
	   (Fatal) innbind was unable to get the socket	options	for that file
	   descriptor.	The most likely	cause of this error is passing the
	   wrong file descriptor number	to innbind (a file descriptor that
	   isn't open, or that corresponds to a	regular	file rather than a
	   network socket).

       cannot get UID for %s
	   (Fatal) innbind was unable to get the UID for the news user
	   specified during configure (and defaulting to "news").  This
	   normally means that user isn't in the system	passwd file.

       cannot mark socket reusable for %s: %s
	   (Fatal) innbind created a new socket	for the	given argument but was
	   unable to mark its bind address reusable (the SO_REUSEADDR socket
	   option).

       cannot pass file	descriptor: %s
	   (Fatal) innbind created and bound a new file	descriptor but was
	   unable to pass it back to its caller	via its	standard output, using
	   the I_SENDFD	STREAMS	ioctl.

       invalid file descriptor %d: not SOCK_STREAM
	   (Fatal) The given file descriptor is	not a SOCK_STREAM socket.
	   innbind can only bind SOCK_STREAM sockets.

       invalid IPv4 address %s in %s
	   (Fatal) The IPv4 address specified in the given command-line	option
	   could not be	parsed by inet_aton(3).	 IPv4 addresses	should be
	   specified in	the standard dotted-quad format	(10.2.3.4).

       invalid IPv6 address %s in %s
	   (Fatal) The IPv6 address specified in the given command-line	option
	   could not be	parsed by inet_pton(3).	 IPv6 addresses	should be
	   specified in	RFC 4291 format	(1080:0:0:0:8:800:200C:417A or
	   1080::8:800:200C:417A).

       invalid command-line argument %s
	   (Fatal) The specified command-line argument could not be parsed or
	   was not in the correct format.

       invalid file descriptor %s in %s
	   (Fatal) The file descriptor portion of the given command-line
	   argument is not a non-negative integer.

       invalid port number %s in %s
	   (Fatal) The port number portion of the given	command-line argument
	   is not a non-negative integer.

       invalid protocol	family %s in %s
	   (Fatal) The protocol	family portion of the given command-line
	   argument is not a non-negative integer.  It should be equal to
	   either AF_INET or AF_INET6 on the system where innbind is run.

       must be run by user %s (%lu), not %lu
	   (Fatal) When	setuid root, innbind may only be run by	the news user
	   as specified	at configure time ("news" by default), for security
	   reasons.

       no addresses specified
	   (Fatal) No arguments	were given on the command line (except maybe
	   -p).

       port may	not be zero in %s
	   (Fatal) The port number portion of the given	command-line argument
	   was zero.

       unknown protocol	family %s in %s
	   (Fatal) The protocol	number portion of the given command-line
	   argument is neither AF_INET nor AF_INET6.

EXAMPLES
       As mentioned above, innbind is never run	directly, only by innd and
       other programs that need	to bind	to and listen to network ports.
       Sample invocations by innd would	be:

	   innbind 3,10,::,119

       to bind the IPv6	socket on file descriptor 3 to port 119, all
       addresses, or:

	   innbind 6,2,10.0.0.3,433

       to bind the IPv4	socket on file descriptor 6 to port 433	in the address
       10.0.0.3.

HISTORY
       Written by Russ Allbery <eagle@eyrie.org> for InterNetNews.

       $Id: innbind.pod	9767 2014-12-07	21:13:43Z iulius $

SEE ALSO
       inet_aton(3), inet_pton(3), innd(8), nnrpd(8).

INN 2.6.1			  2015-09-12			    INNBIND(8)

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | SECURITY | DIAGNOSTICS | EXAMPLES | HISTORY | SEE ALSO

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