REXECD(1M)REXECD(1M)NAMErexecd - remote execution server
SYNOPSIS
/usr/etc/rexecd [ -l ]
DESCRIPTION
Rexecd is the server for the rexec(3N) routine. The server provides
remote execution facilities with authentication based on user names and
passwords. NOTE: password aging is not supported by this daemon.
Rexecd listens for service requests at the port indicated in the ``exec''
service specification; see services(4). When a service request is
received the following protocol is initiated:
1) The server reads characters from the socket up to a null (`\0')
byte. The resultant string is interpreted as an ASCII number, base
10.
2) 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 stderr. A
second connection is then created to the specified port on the
client's machine.
3) A null-terminated user name of at most 16 characters is retrieved on
the initial socket.
4) A null-terminated, unencrypted password of at most 16 characters is
retrieved on the initial socket.
5) A null-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.
6) 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.
7) A null 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 rexecd.
OPTIONS-l This option causes all successful accesses to be logged to
syslogd(1M) as auth.info messages.
FILES
/etc/default/rexecd Default behaviour configuration file
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REXECD(1M)REXECD(1M)SEE ALSOlogin(1), rshd(1M), rexec(3N), passwd(4)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).
``username too long''
The name is longer than 16 characters.
``password too long''
The password is longer than 16 characters.
``command too long ''
The command line passed exceeds the size of the argument list (as
configured into the system).
``Login incorrect.''
No password file entry for the user name existed. (Also logged to the
syslogd(1M) daemon as an auth.notice message.)
``Password incorrect.''
The wrong was password supplied. (Also logged to the syslogd(1M) daemon
as an auth.notice message.)
``No remote directory.''
The chdir command to the home directory failed.
``Try again.''
A fork by the server failed.
``<shellname>: ...''
The user's login shell could not be started. This message is returned on
the connection associated with the stderr, and is not preceded by a flag
byte.
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.
A facility to allow all data and password exchanges to be encrypted
should be present.
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