👤
Home Man
Search
Today's Posts
Register

Linux & Unix Commands - Search Man Pages
Man Page or Keyword Search:
Select Section of Man Page:
Select Man Page Repository:

Linux 2.6 - man page for rresvport (linux section 3)

RCMD(3) 			    Linux Programmer's Manual				  RCMD(3)

NAME
       rcmd,  rresvport, iruserok, ruserok, rcmd_af, rresvport_af, iruserok_af, ruserok_af - rou-
       tines for returning a stream to a remote command

SYNOPSIS
       #include <netdb.h>   /* Or <unistd.h> on some systems */

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

       int rresvport(int *port);

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

       int rresvport_af(int *port, sa_family_t af);

       int iruserok_af(uint32_t raddr, int superuser,
		       const char *ruser, const char *luser, sa_family_t af);

       int ruserok_af(const char *rhost, int superuser,
		      const char *ruser, const char *luser, sa_family_t af);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       rcmd(), rcmd_af(),  rresvport(),  rresvport_af(),  iruserok(),  iruserok_af(),  ruserok(),
       ruserok_af(): _BSD_SOURCE

DESCRIPTION
       The  rcmd()  function  is  used	by the superuser to execute a command on a remote machine
       using an authentication scheme based on privileged port numbers.  The rresvport() function
       returns	a  descriptor  to  a  socket  with  an address in the privileged port space.  The
       iruserok() and ruserok() functions are used by servers to authenticate clients  requesting
       service with rcmd().  All four functions are used by the rshd(8) server (among others).

   rcmd()
       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  con-
       nection 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
       nonzero,  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.

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

   rresvport()
       The  rresvport()  function  is used to obtain a socket with a privileged port bound to it.
       This socket is suitable for use by rcmd() and several other functions.	Privileged  ports
       are  those  in  the  range 0 to 1023.  Only a privileged process (CAP_NET_BIND_SERVICE) is
       allowed to bind to  a  privileged  port.   In  the  glibc  implementation,  this  function
       restricts  its  search  to the ports from 512 to 1023.  The port argument is value-result:
       the value it supplies to the call is used as the starting point for a circular  search  of
       the port range; on (successful) return, it contains the port number that was bound to.

   iruserok() and ruserok()
       The  iruserok()	and  ruserok() functions take a remote host's IP address or name, respec-
       tively, two usernames and a flag indicating whether the local user's name is that  of  the
       superuser.   Then,  if the user is not the superuser, 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 superuser, 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 username are found in the .rhosts file; otherwise iruserok() and ruserok()
       return  -1.   If  the  local  domain  (as obtained from gethostname(2)) 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.

   *_af() variants
       All of the functions described above work with IPv4 (AF_INET) sockets.  The "_af" variants
       take an extra argument that allows the socket address family to be specified.   For  these
       functions,  the	af  argument  can  be  specified  as  AF_INET  or AF_INET6.  In addition,
       rcmd_af() supports the use of AF_UNSPEC.

RETURN VALUE
       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() function returns a valid, bound socket descriptor on success.  It returns
       -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."

       For information on the return from ruserok() and iruserok(), see above.

VERSIONS
       The  functions  iruserok_af(),  rcmd_af(),  rresvport_af(), and ruserok_af() functions are
       provide in glibc since version 2.2.

CONFORMING TO
       Not in POSIX.1-2001.  Present on the BSDs, Solaris, and many other systems.   These  func-
       tions  appeared	in  4.2BSD.   The  "_af"  variants are more recent additions, and are not
       present on as wide a range of systems.

BUGS
       iruserok() and iruserok_af() are declared in glibc headers only since version 2.12.

SEE ALSO
       rlogin(1), rsh(1), intro(2), rexec(3), rexecd(8), rlogind(8), rshd(8)

COLOPHON
       This page is part of release 3.55 of the Linux man-pages project.  A  description  of  the
       project,     and    information	  about    reporting	bugs,	 can	be    found    at
       http://www.kernel.org/doc/man-pages/.

Linux					    2012-04-23					  RCMD(3)


All times are GMT -4. The time now is 07:42 AM.

Unix & Linux Forums Content Copyrightę1993-2018. All Rights Reserved.
×
UNIX.COM Login
Username:
Password:  
Show Password