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1 perry 1 ----
2 __NAME__
3
4
5 rcmd, rresvport, iruserok, ruserok - routines for returning
6 a stream to a remote command
7 __SYNOPSIS__
8
9
10 #include
11
12
13 int
14
15
16 rcmd(char ahost, int inport, const char locuser, const char
17 remuser, const char cmd, int fd2p);
18
19
20 int
21
22
23 rresvport(int port);
24
25
26 int
27
28
29 iruserok(u_int32_t raddr, int superuser, const char ruser,
30 const char luser);
31
32
33 int
34
35
36 ruserok(const char rhost, int superuser, const char ruser,
37 const char luser);
38 __DESCRIPTION__
39
40
41 The rcmd() function is used by the super-user to execute a
42 command on a remote machine using an authentication scheme
43 based on reserved port numbers. The rresvport() function
44 returns a descriptor to a socket with an address in the
45 privileged port space. The iruserok() and ruserok() func-
46 tions are used by servers to authenticate clients requesting
47 service with rcmd(). All four functions are present in the
48 same file and are used by the rshd(8) server (among
49 others).
50
51
52 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.
53
54
55 If the connection succeeds, a socket in the Internet domain
56 of type SOCK_STREAM is returned to the caller, and
57 given to the remote command as ''stdin'' and
58 ''stdout''. If fd2p is non-zero, then an auxiliary
59 channel to a control process will be set up, and a
60 descriptor for it will be placed in fd2p. The control
61 process will return diagnostic output from the command (unit
62 2) on this channel, and will also accept bytes on this
63 channel as being UNIX signal numbers, to be
64 forwarded to the process group of the command. If fd2p is 0,
65 then the ''stderr'' (unit 2 of the remote command) will
66 be made the same as the ''stdout'' and no provision is
67 made for sending arbitrary signals to the remote process,
68 although you may be able to get its attention by using
69 out-of-band data.
70
71
72 The protocol is described in detail in
73 rshd(8).
74
75
76 The rresvport() function is used to obtain a socket with a
77 privileged address bound to it. This socket is suitable for
78 use by rcmd() and several other functions. Privileged
79 Internet ports are those in the range 0 to 1023. Only the
80 super-user is allowed to bind an address of this sort to a
81 socket.
82
83
84 The iruserok() and ruserok() functions take a remote host's
85 IP address or name, respectively, two user names and a flag
86 indicating whether the local user's name is that of the
87 super-user. Then, if the user is ''NOT'' the super-user,
88 it checks the /etc/hosts.equiv file. If that lookup
89 is not done, or is unsuccessful, the .rhosts in the
90 local user's home directory is checked to see if the request
91 for service is allowed.
92
93
94 If this file does not exist, is not a regular file, is owned
95 by anyone other than the user or the super-user, or is
96 writeable by anyone other than the owner, the check automat-
97 ically fails. Zero is returned if the machine name is listed
98 in the ``hosts.equiv'' file, or the host and remote
99 user name are found in the ``.rhosts'' file;
100 otherwise iruserok() and ruserok() return -1. If the local
101 domain (as obtained from gethostname(2)) is the
102 same as the remote domain, only the machine name need be
103 specified.
104
105
106 If the IP address of the remote host is known, iruserok()
107 should be used in preference to ruserok(), as it does not
108 require trusting the DNS server for the remote host's
109 domain.
110 __DIAGNOSTICS__
111
112
113 The rcmd() function returns a valid socket descriptor on
114 success. It returns -1 on error and prints a diagnostic
115 message on the standard error.
116
117
118 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.''
119 __SEE ALSO__
120
121
122 rlogin(1), rsh(1), intro(2),
123 rexec(3), rexecd(8), rlogind(8),
124 rshd(8)
125 __HISTORY__
126
127
128 These functions appeared in 4.2 BSD
129 .
130
131
132 4.2 Berkeley Distribution June 4, 1993 1
133 ----
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