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REXECD(1M)							    REXECD(1M)

NAME    [Toc]    [Back]

     rexecd - remote execution server

SYNOPSIS    [Toc]    [Back]

     /usr/etc/rexecd [ -l ]

DESCRIPTION    [Toc]    [Back]

     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

     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.

SHARE II ACTIONS    [Toc]    [Back]

     If	the Share II system is installed and enabled, then the following
     privilege and resource checks are made immediately	after validation
     checks are	complete (rshd(1)) but before the shell	is started:

     1.	 If your nologin flag is set, or you already have another connection
	 and your onelogin flag	is set,	then you are denied connection.

									Page 1

REXECD(1M)							    REXECD(1M)

     2.	 If a disk usage exceeds the soft disk limit in	any of your domains,
	 then a	message	is printed and you are given a warning.	 If you
	 accumulate too	many warnings, further connection attempts are denied
	 and you must see your subadministrator	to rectify the situation.
	 Whenever you connect with no disk usages in excess of any soft
	 limits, all your accumulated warnings are cleared.

     3.	 If you	do not have permission to use an rexec connection, as
	 determined by the terminal permission flag terminal.flag.rexec, then
	 you are denied	connection.

     4.	 Some installations place limits on terminal connect-time, which apply
	 equally to connection by way of rexec.	 If you	have already reached
	 your connect-time limit, then you are denied connection.  Otherwise,
	 if you	have a limit, your remaining connect-time is printed.

     If	all these checks are passed, rexecd proceeds normally.

     For each new instance of a	remotely initiated process, rexecd first reads
     the configuration file /etc/default/rexecd.  Currently the	only switch in
     this file is SVR4_SIGNALS,	which indicates	if SVR4	signal defaults	should
     be	used, and defaults to `YES'.  This means that processes	spawned	by
     rexecd will run with the SIGXFSZ and SIGXCPU signals disabled (i.e.
     ignored).	For CPU	and filesize resource limiting to work correctly, this
     file should be edited and SVR4_SIGNALS set	to `NO', so that these signal
     retain their default behaviour, which is to terminate the process.

OPTIONS    [Toc]    [Back]

     -l	  This option causes all successful accesses to	be logged to
	  syslogd(1M) as auth.info messages.

FILES    [Toc]    [Back]

     /etc/limconf	 The compiled Share II configuration file (machine

     /etc/default/rexecd Default behaviour configuration file

SEE ALSO    [Toc]    [Back]

     login(1), rshd(1M), rexec(3N), passwd(4), share(5)

DIAGNOSTICS    [Toc]    [Back]

     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.

									Page 2

REXECD(1M)							    REXECD(1M)

     ``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

     The Share II specific diagnostic messages are listed as follows:

     ``Warning <X> of <Y>: soft	disk limit exceeded.''
     One of your domains has a disk usage in excess of its soft	limit.

     ``Connection denied.  Too many warnings.''
     You have reached your warning limit.  See your subadministrator.

     ``Connection denied.  Already logged in - only one	login allowed.''
     You are already connected to the system and your onelogin flag is set.

     ``Connection denied.  Currently barred from logging in.''
     Your nologin flag is set.

     ``Connection denied.  No permission to use	this terminal.''
     You are not allowed to log	in at this terminal because of a clear
     terminal.flag.rexec flag.

     ``You have	a remaining terminal connect-time of <Y>.''
     You may use this connection until you have	used up	your remaining
     connect-time, at which point you are forced to disconnect.

     ``Connection denied.  Terminal connect-time limit exceeded.''
     You have already reached your terminal connect-time limit.

									Page 3

REXECD(1M)							    REXECD(1M)

     ``Share not configured - no limit checks.''
     The configuration file is unreadable for some reason, so terminal
     privileges, connect-time limits and disk space limits could not be

BUGS    [Toc]    [Back]

     Indicating	``Login	incorrect'' as opposed to ``Password incorrect'' is a
     security breach which allows people to probe a system for users with null

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

									PPPPaaaaggggeeee 4444
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