| RCMD(3) | Library Functions Manual | RCMD(3) | 
rcmd, orcmd,
  rcmd_af, orcmd_af,
  rresvport, rresvport_af,
  iruserok, ruserok,
  iruserok_sa —
#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);
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 similar 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
    connection 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, respectively, 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 directory 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>.
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 success. 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.''
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.
| March 30, 2005 | NetBSD 9.3 |