142 lines
3.8 KiB
Groff
142 lines
3.8 KiB
Groff
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.\" Copyright (c) 1983 Regents of the University of California.
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.\" All rights reserved. The Berkeley software License Agreement
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.\" specifies the terms and conditions for redistribution.
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.\"
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.\" @(#)rcmd.3 6.7 (Berkeley) 5/14/86
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.\"
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.TH RCMD 3 "May 14, 1986"
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.UC 5
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.SH NAME
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rcmd, rresvport, ruserok \- routines for returning a stream to a remote command
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.SH SYNOPSIS
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.nf
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.B "#include <sys/types.h>"
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.B "#include <net/netlib.h>"
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.PP
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.B "rem = rcmd(ahost, inport, locuser, remuser, cmd, fd2p);"
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.B char **ahost;
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.B int inport;
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.B "char *locuser, *remuser, *cmd;"
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.B int *fd2p;
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.PP
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.B s = rresvport(port);
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.B int *port;
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.PP
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.B "ruserok(rhost, superuser, ruser, luser);"
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.B char *rhost;
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.B int superuser;
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.B char *ruser, *luser;
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.fi
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.SH DESCRIPTION
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.I Rcmd
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is a routine used by the super-user to execute a command on
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a remote machine using an authentication scheme based
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on reserved port numbers.
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.I Rresvport
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is a routine which returns a descriptor to a socket
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with an address in the privileged port space.
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.I Ruserok
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is a routine used by servers
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to authenticate clients requesting service with
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.IR rcmd .
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All three functions are present in the same file and are used
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by the
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.IR rshd (8)
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server (among others).
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.PP
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.I Rcmd
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looks up the host
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.I *ahost
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using
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.IR gethostbyname (3),
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returning \-1 if the host does not exist.
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Otherwise
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.I *ahost
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is set to the standard name of the host
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and a connection is established to a server
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residing at the well-known Internet port
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.IR inport .
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.PP
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If the connection succeeds,
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a socket in the Internet domain of type SOCK_STREAM
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is returned to the caller, and given to the remote
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command as
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.B stdin
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and
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.BR stdout .
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If
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.I fd2p
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is non-zero, then an auxiliary channel to a control
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process will be set up, and a descriptor for it will be placed
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in
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.IR *fd2p .
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The control process will return diagnostic
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output from the command (unit 2) on this channel, and will also
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accept bytes on this channel as being UNIX signal numbers, to be
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forwarded to the process group of the command.
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If
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.I fd2p
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is 0, then the
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.B stderr
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(unit 2 of the remote
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command) will be made the same as the
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.B stdout
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and no
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provision is made for sending arbitrary signals to the remote process,
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although you may be able to get its attention by using out-of-band data.
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.PP
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The protocol is described in detail in
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.IR rshd (8).
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.PP
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The
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.I rresvport
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routine is used to obtain a socket with a privileged
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address bound to it. This socket is suitable for use
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by
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.I rcmd
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and several other routines. Privileged Internet ports are those
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in the range 0 to 1023. Only the super-user
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is allowed to bind an address of this sort to a socket.
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.PP
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.I Ruserok
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takes a remote host's name, as returned by a
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.IR gethostbyaddr (3)
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routine, two user names and a flag indicating whether
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the local user's name is that of the super-user. It then
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checks the files
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.I /etc/hosts.equiv
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and, possibly,
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.I .rhosts
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in the current working directory (normally the local
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user's home directory) to see if the request for
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service is allowed. A 0 is returned if the machine
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name is listed in the ``hosts.equiv'' file, or the
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host and remote user name are found in the ``.rhosts''
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file; otherwise
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.I ruserok
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returns \-1. If the
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.I superuser
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flag is 1, the checking of the ``host.equiv'' file is
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bypassed.
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If the local domain (as obtained from \fIgethostname\fP\|(3))
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is the same as the remote domain, only the machine name need be specified.
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.SH SEE ALSO
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rlogin(1),
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rsh(1),
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intro(2),
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rexec(3),
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rexecd(8),
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rlogind(8),
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rshd(8)
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.SH DIAGNOSTICS
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.I Rcmd
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returns a valid socket descriptor on success.
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It returns -1 on error and prints a diagnostic message on the standard error.
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.PP
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.I Rresvport
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returns a valid, bound socket descriptor on success.
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It returns -1 on error with the global value
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.I errno
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set according to the reason for failure.
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The error code EAGAIN is overloaded to mean ``All network ports in use.''
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