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1 | .\" Copyright (c) 1983 The Regents of the University of California. |
2 | .\" All rights reserved. | |
8412ed9b | 3 | .\" |
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4 | .\" Redistribution and use in source and binary forms are permitted |
5 | .\" provided that the above copyright notice and this paragraph are | |
6 | .\" duplicated in all such forms and that any documentation, | |
7 | .\" advertising materials, and other materials related to such | |
8 | .\" distribution and use acknowledge that the software was developed | |
9 | .\" by the University of California, Berkeley. The name of the | |
10 | .\" University may not be used to endorse or promote products derived | |
11 | .\" from this software without specific prior written permission. | |
12 | .\" THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR | |
13 | .\" IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED | |
14 | .\" WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE. | |
8412ed9b | 15 | .\" |
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16 | .\" @(#)rexecd.8 6.3 (Berkeley) %G% |
17 | .\" | |
18 | .TH REXECD 8 "" | |
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19 | .UC 5 |
20 | .SH NAME | |
21 | rexecd \- remote execution server | |
22 | .SH SYNOPSIS | |
23 | .B /etc/rexecd | |
24 | .SH DESCRIPTION | |
25 | .I Rexecd | |
26 | is the server for the | |
df119935 | 27 | .IR rexec (3) |
8412ed9b | 28 | routine. The server provides remote execution facilities |
e21fbf8d | 29 | with authentication based on user names and |
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30 | passwords. |
31 | .PP | |
32 | .I Rexecd | |
33 | listens for service requests at the port indicated in | |
34 | the ``exec'' service specification; see | |
35 | .IR services (5). | |
36 | When a service request is received the following protocol | |
37 | is initiated: | |
38 | .IP 1) | |
39 | The server reads characters from the socket up | |
40 | to a null (`\e0') byte. The resultant string is | |
41 | interpreted as an ASCII number, base 10. | |
42 | .IP 2) | |
43 | If the number received in step 1 is non-zero, | |
44 | it is interpreted as the port number of a secondary | |
45 | stream to be used for the | |
46 | .BR stderr . | |
47 | A second connection is then created to the specified | |
48 | port on the client's machine. | |
49 | .IP 3) | |
50 | A null terminated user name of at most 16 characters | |
51 | is retrieved on the initial socket. | |
52 | .IP 4) | |
e21fbf8d | 53 | A null terminated, unencrypted password of at most |
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54 | 16 characters is retrieved on the initial socket. |
55 | .IP 5) | |
56 | A null terminated command to be passed to a | |
57 | shell is retrieved on the initial socket. The length of | |
58 | the command is limited by the upper bound on the size of | |
59 | the system's argument list. | |
60 | .IP 6) | |
61 | .I Rexecd | |
62 | then validates the user as is done at login time | |
63 | and, if the authentication was successful, changes | |
64 | to the user's home directory, and establishes the user | |
65 | and group protections of the user. | |
66 | If any of these steps fail the connection is | |
67 | aborted with a diagnostic message returned. | |
68 | .IP 7) | |
e21fbf8d | 69 | A null byte is returned on the initial socket |
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70 | and the command line is passed to the normal login |
71 | shell of the user. The | |
72 | shell inherits the network connections established | |
73 | by | |
74 | .IR rexecd . | |
75 | .SH DIAGNOSTICS | |
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76 | Except for the last one listed below, |
77 | all diagnostic messages are returned on the initial socket, | |
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78 | after which any network connections are closed. |
79 | An error is indicated by a leading byte with a value of | |
80 | 1 (0 is returned in step 7 above upon successful completion | |
81 | of all the steps prior to the command execution). | |
82 | .PP | |
83 | .B ``username too long'' | |
84 | .br | |
85 | The name is | |
86 | longer than 16 characters. | |
87 | .PP | |
88 | .B ``password too long'' | |
89 | .br | |
90 | The password is longer than 16 characters. | |
91 | .PP | |
92 | .B ``command too long '' | |
93 | .br | |
94 | The command line passed exceeds the size of the argument | |
95 | list (as configured into the system). | |
96 | .PP | |
97 | .B ``Login incorrect.'' | |
98 | .br | |
99 | No password file entry for the user name existed. | |
100 | .PP | |
101 | .B ``Password incorrect.'' | |
102 | .br | |
103 | The wrong was password supplied. | |
104 | .PP | |
105 | .B ``No remote directory.'' | |
106 | .br | |
107 | The | |
108 | .I chdir | |
109 | command to the home directory failed. | |
110 | .PP | |
111 | .B ``Try again.'' | |
112 | .br | |
113 | A | |
114 | .I fork | |
115 | by the server failed. | |
116 | .PP | |
e21fbf8d | 117 | .B ``<shellname>: ...'' |
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118 | .br |
119 | The user's login shell could not be started. | |
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120 | This message is returned |
121 | on the connection associated with the | |
122 | .BR stderr , | |
123 | and is not preceded by a flag byte. | |
124 | .SH SEE ALSO | |
df119935 | 125 | rexec(3) |
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126 | .SH BUGS |
127 | Indicating ``Login incorrect'' as opposed to ``Password incorrect'' | |
128 | is a security breach which allows people to probe a system for users | |
129 | with null passwords. | |
130 | .PP | |
e21fbf8d | 131 | A facility to allow all data and password exchanges to be encrypted should be |
8412ed9b | 132 | present. |