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1.1 root 1: .\" Copyright (c) 1983 Regents of the University of California.
2: .\" All rights reserved. The Berkeley software License Agreement
3: .\" specifies the terms and conditions for redistribution.
4: .\"
5: .\" @(#)rcmd.3 6.8 (Berkeley) 9/30/87
6: .\"
7: .TH RCMD 3 "September 30, 1987"
8: .UC 5
9: .SH NAME
10: rcmd, rresvport, ruserok \- routines for returning a stream to a remote command
11: .SH SYNOPSIS
12: .nf
13: .PP
14: .B "rem = rcmd(ahost, inport, locuser, remuser, cmd, fd2p);"
15: .B char **ahost;
16: .B int inport;
17: .B "char *locuser, *remuser, *cmd;"
18: .B int *fd2p;
19: .PP
20: .B s = rresvport(port);
21: .B int *port;
22: .PP
23: .B "ruserok(rhost, superuser, ruser, luser);"
24: .B char *rhost;
25: .B int superuser;
26: .B char *ruser, *luser;
27: .fi
28: .SH DESCRIPTION
29: .I Rcmd
30: is a routine used by the super-user to execute a command on
31: a remote machine using an authentication scheme based
32: on reserved port numbers.
33: .I Rresvport
34: is a routine which returns a descriptor to a socket
35: with an address in the privileged port space.
36: .I Ruserok
37: is a routine used by servers
38: to authenticate clients requesting service with
39: .IR rcmd .
40: All three functions are present in the same file and are used
41: by the
42: .IR rshd (8C)
43: server (among others).
44: .PP
45: .I Rcmd
46: looks up the host
47: .I *ahost
48: using
49: .IR gethostbyname (3N),
50: returning \-1 if the host does not exist.
51: Otherwise
52: .I *ahost
53: is set to the standard name of the host
54: and a connection is established to a server
55: residing at the well-known Internet port
56: .IR inport .
57: .PP
58: If the connection succeeds,
59: a socket in the Internet domain of type SOCK_STREAM
60: is returned to the caller, and given to the remote
61: command as
62: .B stdin
63: and
64: .BR stdout .
65: If
66: .I fd2p
67: is non-zero, then an auxiliary channel to a control
68: process will be set up, and a descriptor for it will be placed
69: in
70: .IR *fd2p .
71: The control process will return diagnostic
72: output from the command (unit 2) on this channel, and will also
73: accept bytes on this channel as being UNIX signal numbers, to be
74: forwarded to the process group of the command.
75: If
76: .I fd2p
77: is 0, then the
78: .B stderr
79: (unit 2 of the remote
80: command) will be made the same as the
81: .B stdout
82: and no
83: provision is made for sending arbitrary signals to the remote process,
84: although you may be able to get its attention by using out-of-band data.
85: .PP
86: The protocol is described in detail in
87: .IR rshd (8C).
88: .PP
89: The
90: .I rresvport
91: routine is used to obtain a socket with a privileged
92: address bound to it. This socket is suitable for use
93: by
94: .I rcmd
95: and several other routines. Privileged Internet ports are those
96: in the range 0 to 1023. Only the super-user
97: is allowed to bind an address of this sort to a socket.
98: .PP
99: .I Ruserok
100: takes a remote host's name, as returned by a
101: .IR gethostbyaddr (3N)
102: routine, two user names and a flag indicating whether
103: the local user's name is that of the super-user. It then
104: checks the files
105: .I /etc/hosts.equiv
106: and, possibly,
107: .I .rhosts
108: in the local user's home directory to see if the request for
109: service is allowed. A 0 is returned if the machine
110: name is listed in the ``hosts.equiv'' file, or the
111: host and remote user name are found in the ``.rhosts''
112: file; otherwise
113: .I ruserok
114: returns \-1. If the
115: .I superuser
116: flag is 1, the checking of the ``hosts.equiv'' file is
117: bypassed.
118: If the local domain (as obtained from \fIgethostname\fP\|(2))
119: is the same as the remote domain, only the machine name need be specified.
120: .SH SEE ALSO
121: rlogin(1C),
122: rsh(1C),
123: intro(2),
124: rexec(3),
125: rexecd(8C),
126: rlogind(8C),
127: rshd(8C)
128: .SH DIAGNOSTICS
129: .I Rcmd
130: returns a valid socket descriptor on success.
131: It returns -1 on error and prints a diagnostic message on the standard error.
132: .PP
133: .I Rresvport
134: returns a valid, bound socket descriptor on success.
135: It returns -1 on error with the global value
136: .I errno
137: set according to the reason for failure.
138: The error code EAGAIN is overloaded to mean ``All network ports in use.''
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