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NetBSD 6.1.5 - man page for rresvport (netbsd section 3)

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RCMD(3) 			   BSD Library Functions Manual 			  RCMD(3)

NAME
     rcmd, orcmd, rcmd_af, orcmd_af, rresvport, rresvport_af, iruserok, ruserok, iruserok_sa --
     routines for returning a stream to a remote command

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <unistd.h>

     int
     rcmd(char **ahost, int inport, const char *locuser, const char *remuser, const char *cmd,
	 int *fd2p);

     int
     orcmd(char **ahost, int inport, const char *locuser, const char *remuser, const char *cmd,
	 int *fd2p);

     int
     rcmd_af(char **ahost, int inport, const char *locuser, const char *remuser, const char *cmd,
	 int *fd2p, int af);

     int
     orcmd_af(char **ahost, int inport, const char *locuser, const char *remuser,
	 const char *cmd, int *fd2p, int af);

     int
     rresvport(int *port);

     int
     rresvport_af(int *port, int family);

     int
     iruserok(uint32_t raddr, int superuser, const char *ruser, const char *luser);

     int
     ruserok(const char *rhost, int superuser, const char *ruser, const char *luser);

     int
     iruserok_sa(const void *raddr, int rlen, int superuser, const char *ruser,
	 const char *luser);

DESCRIPTION
     The rcmd() function is available for use by anyone to run commands on a remote system.  It
     acts like the orcmd() command, with the exception that it makes a call out to the rcmd(1)
     command, or any other user-specified command, to perform the actual connection (thus not
     requiring that the caller be running as the super-user), and is only available for the
     ``shell/tcp'' port.  The orcmd() function is used by the super-user to execute a command on
     a remote machine using an authentication scheme based on reserved port numbers.  While
     rcmd() and orcmd() can only handle IPv4 address in the first argument, rcmd_af() and
     orcmd_af() can handle other cases as well.  The rresvport() function returns a descriptor to
     a socket with an address in the privileged port space.  The rresvport_af() function is simi-
     lar to rresvport(), but you can explicitly specify the address family to use.  Calling
     rresvport_af() with AF_INET has the same effect as rresvport().  The iruserok() and
     ruserok() functions are used by servers to authenticate clients requesting service with
     rcmd().  All six functions are present in the same file and are used by the rshd(8) server
     (among others).  iruserok_sa() is an address family independent variant of iruserok().

     The rcmd() function looks up the host *ahost using gethostbyname(3), returning -1 if the
     host does not exist.  Otherwise *ahost is set to the standard name of the host and a connec-
     tion is established to a server residing at the well-known Internet port inport.

     If the connection succeeds, a socket in the Internet domain of type SOCK_STREAM is returned
     to the caller, and given to the remote command as stdin and stdout.  If fd2p is non-zero,
     then an auxiliary channel to a control process will be set up, and a descriptor for it will
     be placed in *fd2p.  The control process will return diagnostic output from the command
     (unit 2) on this channel, and will also accept bytes on this channel as being UNIX signal
     numbers, to be forwarded to the process group of the command.  If fd2p is 0, then the stderr
     (unit 2 of the remote command) will be made the same as the stdout and no provision is made
     for sending arbitrary signals to the remote process, although you may be able to get its
     attention by using out-of-band data.

     rcmd_af() and orcmd_af() take address family in the last argument.  If the last argument is
     PF_UNSPEC, interpretation of *ahost will obey the underlying address resolution like DNS.

     The protocol is described in detail in rshd(8).

     The rresvport() and rresvport_af() functions are used to obtain a socket with a privileged
     address bound to it.  This socket is suitable for use by rcmd() and several other functions.
     Privileged Internet ports are those in the range 0 to 1023.  Only the super-user is allowed
     to bind an address of this sort to a socket.

     The iruserok() and ruserok() functions take a remote host's IP address or name, respec-
     tively, two user names and a flag indicating whether the local user's name is that of the
     super-user.  Then, if the user is NOT the super-user, it checks the /etc/hosts.equiv file.
     If that lookup is not done, or is unsuccessful, the .rhosts in the local user's home direc-
     tory is checked to see if the request for service is allowed.

     If this file does not exist, is not a regular file, is owned by anyone other than the user
     or the super-user, or is writable by anyone other than the owner, the check automatically
     fails.  Zero is returned if the machine name is listed in the ``hosts.equiv'' file, or the
     host and remote user name are found in the ``.rhosts'' file; otherwise iruserok() and
     ruserok() return -1.  If the local domain (as obtained from gethostname(3)) is the same as
     the remote domain, only the machine name need be specified.

     If the IP address of the remote host is known, iruserok() should be used in preference to
     ruserok(), as it does not require trusting the DNS server for the remote host's domain.

     While iruserok() can handle IPv4 addresses only, iruserok_sa() and ruserok() can handle
     other address families as well, like IPv6.  The first argument of iruserok_sa() is typed as
     void * to avoid dependency between <unistd.h> and <sys/socket.h>.

ENVIRONMENT
     RCMD_CMD	 When using the rcmd() function, this variable is used as the program to run
		 instead of rcmd(1).

DIAGNOSTICS
     The rcmd() function returns a valid socket descriptor on success.	It returns -1 on error
     and prints a diagnostic message on the standard error.

     The rresvport() and rresvport_af() function return a valid, bound socket descriptor on suc-
     cess.  They return -1 on error with the global value errno set according to the reason for
     failure.  The error code EAGAIN is overloaded to mean ``All network ports in use.''

SEE ALSO
     rcmd(1), rlogin(1), rsh(1), intro(2), rexec(3), hosts.equiv(5), rhosts(5), rexecd(8),
     rlogind(8), rshd(8)

HISTORY
     The orcmd(), rresvport(), iruserok() and ruserok() functions appeared in 4.2BSD, where the
     orcmd() function was called rcmd().  The (newer) rcmd() function appeared in NetBSD 1.3.
     rcmd_af() and rresvport_af() were defined in RFC2292.

BSD					  March 30, 2005				      BSD
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