rexecd(8)

1REXECD(8)                 BSD System Manager's Manual                REXECD(8)
2

NAME

4     rexecd — remote execution server
5

SYNOPSIS

7     rexecd [ -D ]
8

OPTIONS

10     Rexec accepts one option:
11
12     -D      Disable reverse DNS look up and in the log will be used client IP
13             addresses.
14

DESCRIPTION

16     Rexecd is the server for the rexec(3) routine.  The server provides
17     remote execution facilities with authentication based on user names and
18     passwords.
19
20     Rexecd listens for service requests at the port indicated in the ``exec''
21     service specification; see services(5).  When a service request is
22     received the following protocol is initiated:
23
24     1.   The server reads characters from the socket up to a NUL (‘\0’) byte.
25          The resultant string is interpreted as an ASCII number, base 10.
26
27     2.   If the number received in step 1 is non-zero, it is interpreted as
28          the port number of a secondary stream to be used for the stderr.  A
29          second connection will be created to the specified port on the
30          client's machine after receiving and authenticating the user, pass‐
31          word, and command from the client.
32
33     3.   A NUL terminated user name of at most 16 characters is retrieved on
34          the initial socket.
35
36     4.   A NUL terminated, unencrypted password of at most 16 characters is
37          retrieved on the initial socket.
38
39     5.   A NUL terminated command to be passed to a shell is retrieved on the
40          initial socket.  The length of the command is limited by the upper
41          bound on the size of the system's argument list.
42
43     6.   Rexecd then validates the user as is done at login time and, if the
44          authentication was successful, changes to the user's home directory,
45          and establishes the user and group protections of the user.  If any
46          of these steps fail the connection is aborted with a diagnostic mes‐
47          sage returned.
48
49     7.   A NUL byte is returned on the initial socket and the command line is
50          passed to the normal login shell of the user.  The shell inherits
51          the network connections established by rexecd.
52

DIAGNOSTICS

54     Except for the last one listed below, all diagnostic messages are
55     returned on the initial socket, after which any network connections are
56     closed.  An error is indicated by a leading byte with a value of 1 (0 is
57     returned in step 7 above upon successful completion of all the steps
58     prior to the command execution).
59
60     username too long
61             The name is longer than 16 characters.
62
63     password too long
64             The password is longer than 16 characters.
65
66     command too long
67             The command line passed exceeds the size of the argument list (as
68             configured into the system).
69
70     Login incorrect.
71             No password file entry for the user name existed or the wrong
72             password was supplied.
73
74     No remote directory.
75             The chdir command to the home directory failed.
76
77     Try again.
78             A fork by the server failed.
79
80     <shellname>: ...
81             The user's login shell could not be started.  This message is
82             returned on the connection associated with the stderr, and is not
83             preceded by a flag byte.
84

BUGS

89     A facility to allow all data and password exchanges to be encrypted
90     should be present.
91

HISTORY

93     The rexecd command appeared in 4.2BSD.
94
95Linux NetKit (0.17)             March 16, 1991             Linux NetKit (0.17)