inndstart - Start innd

inndstart [-P port] [-I address] [innd-options]

The purpose of inndstart is to raise system file descriptor limits, open the privileged news transfer port, and then start innd(8), passing it the open file descriptor for the news port. inndstart is used since only privileged programs can perform those two operations and since innd should not run with elevated privileges. It is installed setuid root and drops privileges to the news user (as set at configure time) before running innd.

Normally there is no need to run inndstart directly. Instead, run rc.news(8) as the news user, and it will handle running inndstart appropriately for you.

Since inndstart is setuid root, it is extremely restrictive about who can run it and what it is willing to do. See SECURITY for the full details.

inndstart can only be run by the news user; if run by any other user, it will abort. It will also only bind to ports 119, 433, or a port number given at configure time with --with-innd-port among those ports below 1024, although it can bind to any port above 1024. This is to prevent various security exploits possible by binding to arbitrary privileged ports.

Before running innd, inndstart cleans out the environment and sets only those environment variables listed in ENVIRONMENT.

-P port

Bind to port instead of whatever is specified by port in inn.conf. Note that this is subject to the constraints mentioned above.

-I address

Bind as address instead of whatever is specified by bindaddress in inn.conf. The default behavior is to bind to INADDR_ANY, and that's what's desired almost all the time. This option, and the inn.conf parameter, may be useful if the machine has multiple interface cards and innd should only be listening on a particular one.

All other options given on the command line are passed verbatim to innd. In addition, inndstart will give the -p option to innd, specifying the file descriptor of the open network socket.

inndstart is setuid root, and therefore an expected point of attack. It has therefore been carefully written with security in mind. In a normal INN installation, it is installed setuid root and executable only by users in the news group.

Ideally, everything about inndstart's operations would be hard-coded so that it could not be modified. Fighting against this desire, however, is the ideal that as much of INN's operation as possible should be configurable at run-time using inn.conf, and the news system should be able to an alternate inn.conf by setting INNCONF to the path to that file before starting any programs. The configuration data therefore can't be trusted.

The security model used is:

•

inndstart can only be executed by the news user and news group, as determined at configure time and compiled into inndstart as constants. Similarly, inndstart will always setuid() and setgid() to those users before running innd. This is to prevent a user other than news but in the news group from using inndstart to leverage that access into access to the news account.

•

As mentioned above, inndstart will only bind to a very limited subset of ports below 1024. There are various attacks that can be performed using random low-numbered ports, including exploits of the rsh(1) family of commands on some systems.

•

inndstart does as little as possible as root, dropping privileges before performing any operations that do not require elevated privileges.

This program therefore gives the news user the ability to revoke system file descriptor limits and bind to the news port, and nothing else.

inndstart may log the following messages to syslog and print them to stderr. (Fatal) Unable to bind to the designated port. This usually means that something else is already running on the news port. Check with netstat(8) and make sure that inetd(8) doesn't think it's running a service on the same port you're trying to run innd on. (Fatal) inndstart was told to bind to a low numbered port (under 1024) other than 119, 433, or a port number given at configure time. This is not allowed for security reasons. If you're running innd on a port other than 119 or 433, you need to give the --with-innd-port flag to CWconfigure when you compile INN. (Fatal) inndstart was unable to execute innd. Make sure that pathbin is set correctly in inn.conf and that innd is located in that directory and is executable by the news user.

can't getgrnam(%s)

(Fatal) Unable to determine the GID for the compiled-in news group. Perhaps the news group is not listed in /etc/group.

can't getpwnam(%s)

(Fatal) Unable to determine the UID for the compiled-in news user. Perhaps the news user is not listed in /etc/passwd. (Fatal) Something went wrong in creating the network socket. Chances are your system is out of resources of some kind. (Warning) Unable to set the system file descriptor limit to the specified value; the limit was left unchanged. Perhaps that value is too high for your system. Try changing rlimitnofile in inn.conf to a smaller value. (Warning) inndstart attempts to set SO_REUSEADDR using setsockopt(2) so that if innd exits, it can be restarted again immediately without waiting for the port to time out. For some reason, this failed, and that option was not set on the port. (Fatal) Unable to change the effective UID. If inndstart has the correct permissions (setuid root) and seteuid to root (UID 0) is failing, this may mean that your system has seteuid(2) but doesn't have support for POSIX saved UIDs. If this is the case, please report this to the INN maintainers. (Fatal) Dropping privileges to the news group failed for some reason. (Warning) Dropping all supplemental groups except the news group failed for some reason, and the process group membership was left unchanged. This almost always indicates that inndstart isn't setuid root as it has to be to do what it does. Make sure that inndstart is setuid root, owned by group news, and mode 4710. (Fatal) Dropping privileges to the news user failed for some reason. (Fatal) -I was specified on the command line, but the argument wasn't a valid address. Addresses must be given as numeric IP addresses.

invalid bindaddress in inn.conf (%s)

(Fatal) The bindaddress specified in inn.conf could not be converted to an IP address. See inn.conf(5) for more information about valid values. (Fatal) -P was specified on the command line, but the argument wasn't a valid port. Ports must be port numbers; service names are not allowed.

missing address after -I

(Fatal) -I was given on the command line, but no address was given after the option.

missing port after -P

(Fatal) -P was given on the command line, but no port was given after the option. (Fatal) Someone other than the news user attempted to run inndstart. inndstart may only be run by the news user for security reasons.

Normally, inndstart is never run directly. However, a simple way to just restart innd (if it is not running) without running any other auxilliary programs or performing any of the other checks done by rc.news(8) is to just run:

    inndstart

as the news user.

To start innd on port 433, passing it the CW-c21 option, use:

    inndstart -P433 -c21

One environment variable affects the operation of inndstart itself:

INNCONF

The full path to the inn.conf(5) file to read, rather than the default. This can be used to run multiple copies of INN on the same machine with different settings.

When executing innd, inndstart cleans out the entire environmnent and sets only the following variables:

BIND_INADDR

Passed verbatim from inndstart's environment. This is used by various programs to override the bindaddress parameter in inn.conf and therefore must be in innd's environment for programs like innfeed(8).

HOME

Set to pathnews from inn.conf.

LOGNAME

Set to the news master, as determined at configure time.

PATH

Set to pathbin from inn.conf, pathetc from inn.conf, and then /bin, /usr/bin, and /usr/ucb in that order.

SHELL

Set to the path to the system Bourne shell as determined by configure (probably /bin/sh).

TMPDIR

Set to pathtmp from inn.conf.

TZ

Passed verbatim from inndstart's environment.

USER

Set to the news master, as determined at configure time.

inn.conf

Read for pathnews, pathbin, pathtmp, rlimitnofile, bindaddress, and port.

pathbin/innd

The binary that is executed as innd and passed the open network socket.

Written by Russ Allbery <rra@stanford.edu> for InterNetNews.

$Id: inndstart.8,v 1.6 2002/12/03 05:31:10 vinocur Exp $

inn.conf(5), innd(8)