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32 .\" @(#)rshd.8 8.1 (Berkeley) 6/4/93
40 .Nd remote shell server
50 routine and, consequently, for the
52 program. The server provides remote execution facilities
53 with authentication based on privileged port numbers from trusted hosts.
57 utility listens for service requests at the port indicated in
60 service specification; see
62 When a service request is received the following protocol
66 The server checks the client's source port.
67 If the port is not in the range 512-1023, the server
68 aborts the connection.
70 The server reads characters from the socket up
73 (`\e0') byte. The resultant string is
78 If the number received in step 2 is non-zero,
79 it is interpreted as the port number of a secondary
80 stream to be used for the
82 A second connection is then created to the specified
83 port on the client's machine. The source port of this
84 second connection is also in the range 512-1023.
86 The server checks the client's source address
87 and requests the corresponding host name (see
92 If the hostname cannot be determined or the hostname and address do
93 not match after verification,
94 the dot-notation representation of the host address is used.
96 A null terminated user name of at most 16 characters
97 is retrieved on the initial socket. This user name
98 is interpreted as the user identity on the
102 A null terminated user name of at most 16 characters
103 is retrieved on the initial socket. This user name
104 is interpreted as a user identity to use on the
108 A null terminated command to be passed to a
109 shell is retrieved on the initial socket. The length of
110 the command is limited by the upper bound on the size of
111 the system's argument list.
115 utility then validates the user using
121 file found in the user's home directory. The
125 from doing any validation based on the user's
128 unless the user is the superuser.
132 byte is returned on the initial socket
133 and the command line is passed to the normal login
134 shell of the user. The
135 shell inherits the network connections established
140 The options are as follows:
141 .Bl -tag -width indent
143 Display the usage message, and exit.
145 Sets the TCP_NODELAY socket option, which improves the performance
146 of small back-to-back writes at the expense of additional network
149 Causes all successful accesses to be logged to
155 This flag is ignored, and is present for compatability purposes.
157 Do not use the user's
159 file for authentication, unless the user is the superuser.
161 Turn off transport level keepalive messages. This will prevent sessions
162 from timing out if the client crashes or becomes unreachable.
165 Except for the last one listed below,
166 all diagnostic messages
167 are returned on the initial socket,
168 after which any network connections are closed.
169 An error is indicated by a leading byte with a value of
170 1 (0 is returned in step 10 above upon successful completion
171 of all the steps prior to the execution of the login shell).
172 .Bl -tag -width indent
173 .It Sy Locuser too long.
174 The name of the user on the client's machine is
175 longer than 16 characters.
176 .It Sy Ruser too long.
177 The name of the user on the remote machine is
178 longer than 16 characters.
179 .It Sy Command too long.
180 The command line passed exceeds the size of the argument
181 list (as configured into the system).
182 .It Sy Login incorrect.
183 No password file entry for the user name existed
184 or the authentication procedure described above failed.
185 .It Sy Remote directory.
188 function to the home directory failed.
189 .It Sy Logins not available right now.
191 was attempted outside the allowed hours defined in
193 for the local user's login class.
194 .It Sy Can't make pipe.
195 The pipe needed for the
198 .It Sy Can't fork; try again.
201 by the server failed.
202 .It Sy <shellname>: ...
203 The user's login shell could not be started. This message is returned
204 on the connection associated with the
206 and is not preceded by a flag byte.
211 .Xr gethostbyaddr 3 ,
223 .Bl -tag -width /var/run/nologin -compact
225 .It Pa /etc/hosts.equiv
226 .It Pa /etc/login.conf
227 .It Ev $HOME Ns Pa /.rhosts
233 entries with service name
235 Authentication modules requiring passwords (such as
240 The authentication procedure used here assumes the integrity
241 of each client machine and the connecting medium. This is
242 insecure, but is useful in an
246 A facility to allow all data exchanges to be encrypted should be
249 A more extensible protocol (such as Telnet) should be used.
251 IPv6 support was added by WIDE/KAME project.