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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 | .\" | |
e21fbf8d | 5 | .\" @(#)rexecd.8 6.2 (Berkeley) %G% |
8412ed9b | 6 | .\" |
6931c252 | 7 | .TH REXECD 8C "" |
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8 | .UC 5 |
9 | .SH NAME | |
10 | rexecd \- remote execution server | |
11 | .SH SYNOPSIS | |
12 | .B /etc/rexecd | |
13 | .SH DESCRIPTION | |
14 | .I Rexecd | |
15 | is the server for the | |
16 | .IR rexec (3X) | |
17 | routine. The server provides remote execution facilities | |
e21fbf8d | 18 | with authentication based on user names and |
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19 | passwords. |
20 | .PP | |
21 | .I Rexecd | |
22 | listens for service requests at the port indicated in | |
23 | the ``exec'' service specification; see | |
24 | .IR services (5). | |
25 | When a service request is received the following protocol | |
26 | is initiated: | |
27 | .IP 1) | |
28 | The server reads characters from the socket up | |
29 | to a null (`\e0') byte. The resultant string is | |
30 | interpreted as an ASCII number, base 10. | |
31 | .IP 2) | |
32 | If the number received in step 1 is non-zero, | |
33 | it is interpreted as the port number of a secondary | |
34 | stream to be used for the | |
35 | .BR stderr . | |
36 | A second connection is then created to the specified | |
37 | port on the client's machine. | |
38 | .IP 3) | |
39 | A null terminated user name of at most 16 characters | |
40 | is retrieved on the initial socket. | |
41 | .IP 4) | |
e21fbf8d | 42 | A null terminated, unencrypted password of at most |
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43 | 16 characters is retrieved on the initial socket. |
44 | .IP 5) | |
45 | A null terminated command to be passed to a | |
46 | shell is retrieved on the initial socket. The length of | |
47 | the command is limited by the upper bound on the size of | |
48 | the system's argument list. | |
49 | .IP 6) | |
50 | .I Rexecd | |
51 | then validates the user as is done at login time | |
52 | and, if the authentication was successful, changes | |
53 | to the user's home directory, and establishes the user | |
54 | and group protections of the user. | |
55 | If any of these steps fail the connection is | |
56 | aborted with a diagnostic message returned. | |
57 | .IP 7) | |
e21fbf8d | 58 | A null byte is returned on the initial socket |
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59 | and the command line is passed to the normal login |
60 | shell of the user. The | |
61 | shell inherits the network connections established | |
62 | by | |
63 | .IR rexecd . | |
64 | .SH DIAGNOSTICS | |
e21fbf8d JL |
65 | Except for the last one listed below, |
66 | all diagnostic messages are returned on the initial socket, | |
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67 | after which any network connections are closed. |
68 | An error is indicated by a leading byte with a value of | |
69 | 1 (0 is returned in step 7 above upon successful completion | |
70 | of all the steps prior to the command execution). | |
71 | .PP | |
72 | .B ``username too long'' | |
73 | .br | |
74 | The name is | |
75 | longer than 16 characters. | |
76 | .PP | |
77 | .B ``password too long'' | |
78 | .br | |
79 | The password is longer than 16 characters. | |
80 | .PP | |
81 | .B ``command too long '' | |
82 | .br | |
83 | The command line passed exceeds the size of the argument | |
84 | list (as configured into the system). | |
85 | .PP | |
86 | .B ``Login incorrect.'' | |
87 | .br | |
88 | No password file entry for the user name existed. | |
89 | .PP | |
90 | .B ``Password incorrect.'' | |
91 | .br | |
92 | The wrong was password supplied. | |
93 | .PP | |
94 | .B ``No remote directory.'' | |
95 | .br | |
96 | The | |
97 | .I chdir | |
98 | command to the home directory failed. | |
99 | .PP | |
100 | .B ``Try again.'' | |
101 | .br | |
102 | A | |
103 | .I fork | |
104 | by the server failed. | |
105 | .PP | |
e21fbf8d | 106 | .B ``<shellname>: ...'' |
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107 | .br |
108 | The user's login shell could not be started. | |
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109 | This message is returned |
110 | on the connection associated with the | |
111 | .BR stderr , | |
112 | and is not preceded by a flag byte. | |
113 | .SH SEE ALSO | |
114 | rexec(3X) | |
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115 | .SH BUGS |
116 | Indicating ``Login incorrect'' as opposed to ``Password incorrect'' | |
117 | is a security breach which allows people to probe a system for users | |
118 | with null passwords. | |
119 | .PP | |
e21fbf8d | 120 | A facility to allow all data and password exchanges to be encrypted should be |
8412ed9b | 121 | present. |