BSD 4_4 development

[unix-history] / usr / share / man / cat3 / rcmd.0

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

N\bNA\bAM\bME\bE
     r\brc\bcm\bmd\bd, r\brr\bre\bes\bsv\bvp\bpo\bor\brt\bt, r\bru\bus\bse\ber\bro\bok\bk - routines for returning a stream to a remote
     command

S\bSY\bYN\bNO\bOP\bPS\bSI\bIS\bS
     #\b#i\bin\bnc\bcl\blu\bud\bde\be <\b<u\bun\bni\bis\bst\btd\bd.\b.h\bh>\b>

     _\bi_\bn_\bt
     r\brc\bcm\bmd\bd(_\bc_\bh_\ba_\br _\b*_\b*_\ba_\bh_\bo_\bs_\bt, _\bi_\bn_\bt _\bi_\bn_\bp_\bo_\br_\bt, _\bc_\bo_\bn_\bs_\bt _\bc_\bh_\ba_\br _\b*_\bl_\bo_\bc_\bu_\bs_\be_\br, _\bc_\bo_\bn_\bs_\bt _\bc_\bh_\ba_\br _\b*_\br_\be_\bm_\bu_\bs_\be_\br,
             _\bc_\bo_\bn_\bs_\bt _\bc_\bh_\ba_\br _\b*_\bc_\bm_\bd, _\bi_\bn_\bt _\b*_\bf_\bd_\b2_\bp);

     _\bi_\bn_\bt
     r\brr\bre\bes\bsv\bvp\bpo\bor\brt\bt(_\bi_\bn_\bt _\b*_\bp_\bo_\br_\bt);

     _\bi_\bn_\bt
     i\bir\bru\bus\bse\ber\bro\bok\bk(_\bu_\b__\bl_\bo_\bn_\bg _\br_\ba_\bd_\bd_\br, _\bi_\bn_\bt _\bs_\bu_\bp_\be_\br_\bu_\bs_\be_\br, _\bc_\bo_\bn_\bs_\bt _\bc_\bh_\ba_\br _\b*_\br_\bu_\bs_\be_\br,
             _\bc_\bo_\bn_\bs_\bt _\bc_\bh_\ba_\br _\b*_\bl_\bu_\bs_\be_\br);

     _\bi_\bn_\bt
     r\bru\bus\bse\ber\bro\bok\bk(_\bc_\bo_\bn_\bs_\bt _\bc_\bh_\ba_\br _\b*_\br_\bh_\bo_\bs_\bt, _\bi_\bn_\bt _\bs_\bu_\bp_\be_\br_\bu_\bs_\be_\br, _\bc_\bo_\bn_\bs_\bt _\bc_\bh_\ba_\br _\b*_\br_\bu_\bs_\be_\br,
             _\bc_\bo_\bn_\bs_\bt _\bc_\bh_\ba_\br _\b*_\bl_\bu_\bs_\be_\br);

D\bDE\bES\bSC\bCR\bRI\bIP\bPT\bTI\bIO\bON\bN
     The r\brc\bcm\bmd\bd() function is used by the super-user to execute a command on a
     remote machine using an authentication scheme based on reserved port num-
     bers.  The r\brr\bre\bes\bsv\bvp\bpo\bor\brt\bt() function returns a descriptor to a socket with an
     address in the privileged port space.  The r\bru\bus\bse\ber\bro\bok\bk() function is used by
     servers to authenticate clients requesting service with r\brc\bcm\bmd\bd().  All
     three functions are present in the same file and are used by the rshd(8)
     server (among others).

     The r\brc\bcm\bmd\bd() function looks up the host _\b*_\ba_\bh_\bo_\bs_\bt using gethostbyname(3),  re-
     turning -1 if the host does not exist.  Otherwise _\b*_\ba_\bh_\bo_\bs_\bt is set to the
     standard name of the host and a connection is established to a server re-
     siding at the well-known Internet port _\bi_\bn_\bp_\bo_\br_\bt.

     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
     _\bs_\bt_\bd_\bi_\bn and _\bs_\bt_\bd_\bo_\bu_\bt. If _\bf_\bd_\b2_\bp is non-zero, then an auxiliary channel to a
     control process will be set up, and a descriptor for it will be placed in
     _\b*_\bf_\bd_\b2_\bp. 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 _\bf_\bd_\b2_\bp is 0, then the _\bs_\bt_\bd_\be_\br_\br (unit 2 of the remote command)
     will be made the same as the _\bs_\bt_\bd_\bo_\bu_\bt 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).

     The r\brr\bre\bes\bsv\bvp\bpo\bor\brt\bt() function is used to obtain a socket with a privileged ad-
     dress bound to it.  This socket is suitable for use by r\brc\bcm\bmd\bd() 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 i\bir\bru\bus\bse\ber\bro\bok\bk() and r\bru\bus\bse\ber\bro\bok\bk() functions take a remote host's IP address or
     name, as returned by the gethostbyname(3) routines, two user names and a
     flag indicating whether the local user's name is that of the super-user.
     Then, if the user is _\bN_\bO_\bT the super-user, it checks the _\b/_\be_\bt_\bc_\b/_\bh_\bo_\bs_\bt_\bs_\b._\be_\bq_\bu_\bi_\bv
     file.  If that lookup is not done, or is unsuccessful, the _\b._\br_\bh_\bo_\bs_\bt_\bs 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 writeable by anyone other
     than the owner, the check automatically fails.  Zero is returned if the
     machine name is listed in the ``_\bh_\bo_\bs_\bt_\bs_\b._\be_\bq_\bu_\bi_\bv'' file, or the host and re-
     mote user name are found in the ``_\b._\br_\bh_\bo_\bs_\bt_\bs'' file; otherwise i\bir\bru\bus\bse\ber\bro\bok\bk()
     and r\bru\bus\bse\ber\bro\bok\bk() 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.

     The i\bir\bru\bus\bse\ber\bro\bok\bk() function is strongly preferred for security reasons.  It
     requires trusting the local DNS at most, while the r\bru\bus\bse\ber\bro\bok\bk() function re-
     quires trusting the entire DNS, which can be spoofed.

D\bDI\bIA\bAG\bGN\bNO\bOS\bST\bTI\bIC\bCS\bS
     The r\brc\bcm\bmd\bd() function returns a valid socket descriptor on success.  It re-
     turns -1 on error and prints a diagnostic message on the standard error.

     The r\brr\bre\bes\bsv\bvp\bpo\bor\brt\bt() function returns a valid, bound socket descriptor on suc-
     cess.  It returns -1 on error with the global value _\be_\br_\br_\bn_\bo set according
     to the reason for failure.  The error code EAGAIN is overloaded to mean
     ``All network ports in use.''

S\bSE\bEE\bE A\bAL\bLS\bSO\bO
     rlogin(1),  rsh(1),  intro(2),  rexec(3),  rexecd(8),  rlogind(8),
     rshd(8)

H\bHI\bIS\bST\bTO\bOR\bRY\bY
     These functions appeared in 4.2BSD.

4.2 Berkeley Distribution        June 4, 1993                                2