[apple/network_cmds.git] / rexecd.tproj / rexecd.8

.\" Copyright (c) 1983, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
.\"	California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"     @(#)rexecd.8	8.3 (Berkeley) 6/1/94
.\"
.Dd June 1, 1994
.Dt REXECD 8
.Os BSD 4.2
.Sh NAME
.Nm rexecd
.Nd remote execution server
.Sh SYNOPSIS
.Nm rexecd
.Sh DESCRIPTION
.Nm Rexecd
is the server for the 
.Xr rexec 3
routine.  The server provides remote execution facilities
with authentication based on user names and
passwords.
.Pp
.Nm Rexecd
listens for service requests at the port indicated in
the ``exec'' service specification; see
.Xr services 5 .
When a service request is received the following protocol
is initiated:
.Bl -enum
.It
The server reads characters from the socket up
to a NUL
.Pq Ql \e0
byte.  The resultant string is
interpreted as an
.Tn ASCII
number, base 10.
.It 
If the number received in step 1 is non-zero,
it is interpreted as the port number of a secondary
stream to be used for the 
.Em stderr .
A second connection is then created to the specified
port on the client's machine.
.It
A NUL terminated user name of at most 16 characters
is retrieved on the initial socket.
.It
A NUL terminated, unencrypted password of at most
16 characters is retrieved on the initial socket.  
.It
A NUL terminated command to be passed to a
shell is retrieved on the initial socket.  The length of
the command is limited by the upper bound on the size of
the system's argument list.  
.It
.Nm Rexecd
then validates the user as is done at login time
and, if the authentication was successful, changes
to the user's home directory, and establishes the user
and group protections of the user.
If any of these steps fail the connection is
aborted with a diagnostic message returned.
.It
A NUL byte is returned on the initial socket
and the command line is passed to the normal login
shell of the user.  The
shell inherits the network connections established
by
.Nm rexecd .
.El
.Sh DIAGNOSTICS
Except for the last one listed below,
all diagnostic messages are returned on the initial socket,
after which any network connections are closed.
An error is indicated by a leading byte with a value of
1 (0 is returned in step 7 above upon successful completion
of all the steps prior to the command execution).
.Pp
.Bl -tag -width Ds
.It Sy username too long
The name is
longer than 16 characters.
.It Sy password too long
The password is longer than 16 characters.
.It Sy command too long
The command line passed exceeds the size of the argument
list (as configured into the system).
.It Sy Login incorrect.
No password file entry for the user name existed.
.It Sy Password incorrect.
The wrong password was supplied.
.ne 1i
.It Sy \&No remote directory.
The 
.Xr chdir
command to the home directory failed.
.It Sy Try again.
A
.Xr fork
by the server failed.
.It Sy <shellname>: ...
The user's login shell could not be started.
This message is returned
on the connection associated with the
.Em stderr ,
and is not preceded by a flag byte.
.El
.Sh SEE ALSO
.Xr rexec 3
.Sh BUGS
Indicating ``Login incorrect'' as opposed to ``Password incorrect''
is a security breach which allows people to probe a system for users
with null passwords.
.Pp
A facility to allow all data and password exchanges to be encrypted should be
present.
.Sh HISTORY
The
.Nm
command appeared in
.Bx 4.2 .
Commit	Line	Data
b7080c8e A	1	.\" Copyright (c) 1983, 1991, 1993
	2	.\" The Regents of the University of California. All rights reserved.
	3	.\"
	4	.\" Redistribution and use in source and binary forms, with or without
	5	.\" modification, are permitted provided that the following conditions
	6	.\" are met:
	7	.\" 1. Redistributions of source code must retain the above copyright
	8	.\" notice, this list of conditions and the following disclaimer.
	9	.\" 2. Redistributions in binary form must reproduce the above copyright
	10	.\" notice, this list of conditions and the following disclaimer in the
	11	.\" documentation and/or other materials provided with the distribution.
	12	.\" 3. All advertising materials mentioning features or use of this software
	13	.\" must display the following acknowledgement:
	14	.\" This product includes software developed by the University of
	15	.\" California, Berkeley and its contributors.
	16	.\" 4. Neither the name of the University nor the names of its contributors
	17	.\" may be used to endorse or promote products derived from this software
	18	.\" without specific prior written permission.
	19	.\"
	20	.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	21	.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	22	.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	23	.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	24	.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	25	.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	26	.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	27	.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	28	.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	29	.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	30	.\" SUCH DAMAGE.
	31	.\"
	32	.\" @(#)rexecd.8 8.3 (Berkeley) 6/1/94
	33	.\"
	34	.Dd June 1, 1994
	35	.Dt REXECD 8
	36	.Os BSD 4.2
	37	.Sh NAME
	38	.Nm rexecd
	39	.Nd remote execution server
	40	.Sh SYNOPSIS
	41	.Nm rexecd
	42	.Sh DESCRIPTION
	43	.Nm Rexecd
	44	is the server for the
	45	.Xr rexec 3
	46	routine. The server provides remote execution facilities
	47	with authentication based on user names and
	48	passwords.
	49	.Pp
	50	.Nm Rexecd
	51	listens for service requests at the port indicated in
	52	the ``exec'' service specification; see
	53	.Xr services 5 .
	54	When a service request is received the following protocol
	55	is initiated:
	56	.Bl -enum
	57	.It
	58	The server reads characters from the socket up
	59	to a NUL
	60	.Pq Ql \e0
	61	byte. The resultant string is
	62	interpreted as an
	63	.Tn ASCII
	64	number, base 10.
65	.It
66	If the number received in step 1 is non-zero,
67	it is interpreted as the port number of a secondary
68	stream to be used for the
69	.Em stderr .
70	A second connection is then created to the specified
71	port on the client's machine.
72	.It
73	A NUL terminated user name of at most 16 characters
74	is retrieved on the initial socket.
75	.It
76	A NUL terminated, unencrypted password of at most
77	16 characters is retrieved on the initial socket.
78	.It
79	A NUL terminated command to be passed to a
80	shell is retrieved on the initial socket. The length of
81	the command is limited by the upper bound on the size of
82	the system's argument list.
83	.It
84	.Nm Rexecd
85	then validates the user as is done at login time
86	and, if the authentication was successful, changes
87	to the user's home directory, and establishes the user
88	and group protections of the user.
89	If any of these steps fail the connection is
90	aborted with a diagnostic message returned.
91	.It
92	A NUL byte is returned on the initial socket
93	and the command line is passed to the normal login
94	shell of the user. The
95	shell inherits the network connections established
96	by
97	.Nm rexecd .
98	.El
99	.Sh DIAGNOSTICS
100	Except for the last one listed below,
101	all diagnostic messages are returned on the initial socket,
102	after which any network connections are closed.
103	An error is indicated by a leading byte with a value of
104	1 (0 is returned in step 7 above upon successful completion
105	of all the steps prior to the command execution).
106	.Pp
107	.Bl -tag -width Ds
108	.It Sy username too long
109	The name is
110	longer than 16 characters.
111	.It Sy password too long
112	The password is longer than 16 characters.
113	.It Sy command too long
114	The command line passed exceeds the size of the argument
115	list (as configured into the system).
116	.It Sy Login incorrect.
117	No password file entry for the user name existed.
118	.It Sy Password incorrect.
119	The wrong password was supplied.
120	.ne 1i
121	.It Sy \&No remote directory.
122	The
123	.Xr chdir
124	command to the home directory failed.
125	.It Sy Try again.
126	A
127	.Xr fork
128	by the server failed.
129	.It Sy <shellname>: ...
130	The user's login shell could not be started.
131	This message is returned
132	on the connection associated with the
133	.Em stderr ,
134	and is not preceded by a flag byte.
135	.El
136	.Sh SEE ALSO
137	.Xr rexec 3
138	.Sh BUGS
139	Indicating ``Login incorrect'' as opposed to ``Password incorrect''
140	is a security breach which allows people to probe a system for users
141	with null passwords.
142	.Pp
143	A facility to allow all data and password exchanges to be encrypted should be
144	present.
145	.Sh HISTORY
146	The
147	.Nm
148	command appeared in
149	.Bx 4.2 .