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1.1 root 1: .\" Copyright (c) 1983 The Regents of the University of California.
2: .\" All rights reserved.
3: .\"
4: .\" Redistribution and use in source and binary forms are permitted provided
5: .\" that: (1) source distributions retain this entire copyright notice and
6: .\" comment, and (2) distributions including binaries display the following
7: .\" acknowledgement: ``This product includes software developed by the
8: .\" University of California, Berkeley and its contributors'' in the
9: .\" documentation or other materials provided with the distribution and in
10: .\" all advertising materials mentioning features or use of this software.
11: .\" Neither the name of the University nor the names of its contributors may
12: .\" be used to endorse or promote products derived from this software without
13: .\" specific prior written permission.
14: .\" THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
15: .\" WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
16: .\" MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
17: .\"
18: .\" @(#)rcmd.3 6.10 (Berkeley) 6/23/90
19: .\"
20: .TH RCMD 3 "June 23, 1990"
21: .UC 5
22: .SH NAME
23: rcmd, rresvport, ruserok \- routines for returning a stream to a remote command
24: .SH SYNOPSIS
25: .nf
26: .PP
27: .B "rem = rcmd(ahost, inport, locuser, remuser, cmd, fd2p);"
28: .B char **ahost;
29: .B int inport;
30: .B "char *locuser, *remuser, *cmd;"
31: .B int *fd2p;
32: .PP
33: .B s = rresvport(port);
34: .B int *port;
35: .PP
36: .B "ruserok(rhost, superuser, ruser, luser);"
37: .B char *rhost;
38: .B int superuser;
39: .B char *ruser, *luser;
40: .fi
41: .SH DESCRIPTION
42: .I Rcmd
43: is a routine used by the super-user to execute a command on
44: a remote machine using an authentication scheme based
45: on reserved port numbers.
46: .I Rresvport
47: is a routine which returns a descriptor to a socket
48: with an address in the privileged port space.
49: .I Ruserok
50: is a routine used by servers
51: to authenticate clients requesting service with
52: .IR rcmd .
53: All three functions are present in the same file and are used
54: by the
55: .IR rshd (8)
56: server (among others).
57: .PP
58: .I Rcmd
59: looks up the host
60: .I *ahost
61: using
62: .IR gethostbyname (3),
63: returning \-1 if the host does not exist.
64: Otherwise
65: .I *ahost
66: is set to the standard name of the host
67: and a connection is established to a server
68: residing at the well-known Internet port
69: .IR inport .
70: .PP
71: If the connection succeeds,
72: a socket in the Internet domain of type SOCK_STREAM
73: is returned to the caller, and given to the remote
74: command as
75: .B stdin
76: and
77: .BR stdout .
78: If
79: .I fd2p
80: is non-zero, then an auxiliary channel to a control
81: process will be set up, and a descriptor for it will be placed
82: in
83: .IR *fd2p .
84: The control process will return diagnostic
85: output from the command (unit 2) on this channel, and will also
86: accept bytes on this channel as being UNIX signal numbers, to be
87: forwarded to the process group of the command.
88: If
89: .I fd2p
90: is 0, then the
91: .B stderr
92: (unit 2 of the remote
93: command) will be made the same as the
94: .B stdout
95: and no
96: provision is made for sending arbitrary signals to the remote process,
97: although you may be able to get its attention by using out-of-band data.
98: .PP
99: The protocol is described in detail in
100: .IR rshd (8).
101: .PP
102: The
103: .I rresvport
104: routine is used to obtain a socket with a privileged
105: address bound to it. This socket is suitable for use
106: by
107: .I rcmd
108: and several other routines. Privileged Internet ports are those
109: in the range 0 to 1023. Only the super-user
110: is allowed to bind an address of this sort to a socket.
111: .PP
112: .I Ruserok
113: takes a remote host's name, as returned by the
114: .IR gethostbyaddr (3)
115: routine, two user names and a flag indicating whether
116: the local user's name is that of the super-user. Then,
117: if the user is
118: .B NOT
119: the super-user, it checks the files
120: .IR /etc/hosts.equiv .
121: If that lookup is not done, or is unsuccessful, the
122: .I .rhosts
123: in the local user's home directory is checked to see if the request for
124: service is allowed. If this file is owned by anyone other than the
125: user or the super-user, or if it is writeable by anyone other than the
126: owner, the check automatically fails. A 0 is returned if the machine
127: name is listed in the ``hosts.equiv'' file, or the host and remote
128: user name are found in the ``.rhosts'' file; otherwise
129: .I ruserok
130: returns \-1.
131: If the local domain (as obtained from \fIgethostname\fP\|(2))
132: is the same as the remote domain, only the machine name need be specified.
133: .SH SEE ALSO
134: rlogin(1), rsh(1), intro(2), rexec(3), rexecd(8), rlogind(8), rshd(8)
135: .SH DIAGNOSTICS
136: .I Rcmd
137: returns a valid socket descriptor on success.
138: It returns -1 on error and prints a diagnostic message on the standard error.
139: .PP
140: .I Rresvport
141: returns a valid, bound socket descriptor on success.
142: It returns -1 on error with the global value
143: .I errno
144: set according to the reason for failure.
145: The error code EAGAIN is overloaded to mean ``All network ports in use.''
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